Release 2.8

Fixed musl
Missing headers
2026-04-28 19:03:33 +00:00 · 2022-05-10 04:17:09 +03:00 · 2022-05-10 04:04:05 +03:00 · 2022-05-09 22:56:41 +03:00 · 2022-05-09 20:21:42 +03:00 · 2022-05-09 20:00:44 +03:00
113 changed files with 11216 additions and 5213 deletions
--- a/.github/workflows/cpp.yml
+++ b/.github/workflows/cpp.yml
@@ -0,0 +1,21 @@
+name: C++ CI
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v2.1.0
+        with:
+          distribution: "adopt"
+          java-version: "11"
+      - run: sudo sysctl kernel.perf_event_paranoid=1
+      - run: make
+      - run: make test
+      - uses: actions/upload-artifact@v2
+        with:
+          path: build/
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 language: cpp

-dist: precise
+dist: bionic

 sudo: required

--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,21 +1,112 @@
 # Changelog

-## [2.0-b1] - Early access
+## [2.8] - 2022-05-09
+
+### Features
+ - Mark top methods as interpreted, compiled (C1/C2), or inlined
+ - JVM TI based allocation profiling for JDK 11+
+ - Embedded HTTP management server
+
+### Improvements
+ - Re-implemented stack recovery for better reliability
+ - Add `loglevel` argument
+ - Do not mmap perf page in `--all-user` mode
+ - Distinguish runnable/sleeping threads in OpenJ9 wall-clock profiler
+ - `--cpu` converter option to extract CPU profile from the wall-clock output
+
+## [2.7] - 2022-02-14
+
+### Features
+ - Experimental support for OpenJ9 VM
+ - DWARF stack unwinding
+
+### Improvements
+ - Better handling of VM threads (fixed missing JIT threads)
+ - More reliable recovery from `not_walkable` AGCT failures
+ - Do not accept unknown agent arguments
+
+## [2.6] - 2022-01-09
+
+### Features
+ - Continuous profiling; `loop` and `timeout` options
+
+### Improvements
+ - Reliability improvements: avoid certain crashes and deadlocks
+ - Smaller and faster agent library
+ - Minor `jfr` and `jfrsync` enhancements (see the commit log)
+
+## [2.5.1] - 2021-12-05
+
+### Bug fixes
+ - Prevent early unloading of libasyncProfiler.so
+ - Read kernel symbols only for perf_events
+ - Escape backslashes in flame graphs
+ - Avoid duplicate categories in `jfrsync` mode
+ - Fixed stack overflow in RedefineClasses
+ - Fixed deadlock when flushing JFR
+
+### Improvements
+ - Support OpenJDK C++ Interpreter (aka Zero)
+ - Allow reading incomplete JFR recordings
+
+## [2.5] - 2021-10-01
+
+### Features
+ - macOS/ARM64 (aka Apple M1) port
+ - PPC64LE port (contributed by @ghaug)
+ - Profile low-privileged processes with perf_events (contributed by @Jongy)
+ - Raw PMU events; kprobes & uprobes
+ - Dump results in the middle of profiling session
+ - Chunked JFR; support JFR files larger than 2 GB
+ - Integrate async-profiler events with JDK Flight Recordings
+
+### Improvements
+ - Use RDTSC for JFR timestamps when possible
+ - Show line numbers and bci in Flame Graphs
+ - jfr2flame can produce Allocation and Lock flame graphs
+ - Flame Graph title depends on the event and `--total`
+ - Include profiler logs and native library list in JFR output
+ - Lock profiling no longer requires JVM symbols
+ - Better container support
+ - Native function profiler can count the specified argument
+ - An option to group threads by scheduling policy
+ - An option to prepend library name to native symbols
+
+### Notes
+ - macOS build is provided as a fat binary that works both on x86-64 and ARM64
+ - 32-bit binaries are no longer shipped. It is still possible to build them from sources
+ - Dropped JDK 6 support (may still work though)
+
+## [2.0] - 2021-03-14

 ### Features
 - Profile multiple events together (cpu + alloc + lock)
 - HTML 5 Flame Graphs: faster rendering, smaller size
 - JFR v2 output format, compatible with FlightRecorder API
+ - JFR to Flame Graph converter
 - Automatically turn profiling on/off at `--begin`/`--end` functions
- - Time-to-safepoint profiling
+ - Time-to-safepoint profiling: `--ttsp`

 ### Improvements
 - Unlimited frame buffer. Removed `-b` option and 64K stack traces limit
- - Record CPU load in JFR format
+ - Additional JFR events: OS, CPU, and JVM information; CPU load
+ - Record bytecode indices / line numbers
+ - Native stack traces for Java events
+ - Improved CLI experience
+ - Better error handling; an option to log warnings/errors to a dedicated stream
+ - Reduced the amount of unknown stack traces

 ### Changes
 - Removed non-ASL code. No more CDDL license

+## [1.8.4] - 2021-02-24
+
+### Improvements
+ - Smaller and faster agent library
+
+### Bug fixes
+ - Fixed JDK 7 crash during wall-clock profiling
+
 ## [1.8.3] - 2021-01-06

 ### Improvements
--- a/96
+++ b/96
@@ -1,6 +1,4 @@
-PROFILER_VERSION=2.0-b1
-JATTACH_VERSION=1.5
-JAVAC_RELEASE_VERSION=6
+PROFILER_VERSION=2.8

 PACKAGE_NAME=async-profiler-$(PROFILER_VERSION)-$(OS_TAG)-$(ARCH_TAG)
 PACKAGE_DIR=/tmp/$(PACKAGE_NAME)
@@ -11,16 +9,19 @@ JATTACH=jattach
 API_JAR=async-profiler.jar
 CONVERTER_JAR=converter.jar

-CFLAGS=-O3 -fno-omit-frame-pointer -fvisibility=hidden
+CFLAGS=-O3
 CXXFLAGS=-O3 -fno-omit-frame-pointer -fvisibility=hidden
 INCLUDES=-I$(JAVA_HOME)/include
 LIBS=-ldl -lpthread
+MERGE=true

 JAVAC=$(JAVA_HOME)/bin/javac
 JAR=$(JAVA_HOME)/bin/jar
+JAVAC_RELEASE_VERSION=7

 SOURCES := $(wildcard src/*.cpp)
-HEADERS := $(wildcard src/*.h)
+HEADERS := $(wildcard src/*.h src/fdtransfer/*.h)
+JAVA_HEADERS := $(patsubst %.java,%.class.h,$(wildcard src/helper/one/profiler/*.java))
 API_SOURCES := $(wildcard src/api/one/profiler/*.java)
 CONVERTER_SOURCES := $(shell find src/converter -name '*.java')

@@ -29,17 +30,33 @@ ifeq ($(JAVA_HOME),)
 endif

 OS:=$(shell uname -s)
-ifeq ($(OS), Darwin)
+ifeq ($(OS),Darwin)
  CXXFLAGS += -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE
  INCLUDES += -I$(JAVA_HOME)/include/darwin
+  FDTRANSFER_BIN=
  SOEXT=dylib
+  PACKAGE_EXT=zip
  OS_TAG=macos
+  ifeq ($(FAT_BINARY),true)
+    FAT_BINARY_FLAGS=-arch x86_64 -arch arm64 -mmacos-version-min=10.12
+    CFLAGS += $(FAT_BINARY_FLAGS)
+    CXXFLAGS += $(FAT_BINARY_FLAGS)
+    PACKAGE_NAME=async-profiler-$(PROFILER_VERSION)-$(OS_TAG)
+    MERGE=false
+  endif
 else
+  CXXFLAGS += -Wl,-z,defs -Wl,-z,nodelete
+  ifeq ($(MERGE),true)
+    CXXFLAGS += -fwhole-program
+  endif
  LIBS += -lrt
  INCLUDES += -I$(JAVA_HOME)/include/linux
+  FDTRANSFER_BIN=build/fdtransfer
  SOEXT=so
+  PACKAGE_EXT=tar.gz
  ifeq ($(findstring musl,$(shell ldd /bin/ls)),musl)
    OS_TAG=linux-musl
+    CXXFLAGS += -D__musl__
  else
    OS_TAG=linux
  endif
@@ -50,62 +67,99 @@ ifeq ($(ARCH),x86_64)
  ARCH_TAG=x64
 else
  ifeq ($(findstring arm,$(ARCH)),arm)
-    ARCH_TAG=arm
+    ifeq ($(findstring 64,$(ARCH)),64)
+      ARCH_TAG=arm64
+    else
+      ARCH_TAG=arm32
+    endif
  else
    ifeq ($(findstring aarch64,$(ARCH)),aarch64)
-      ARCH_TAG=aarch64
+      ARCH_TAG=arm64
    else
-      ARCH_TAG=x86
+      ifeq ($(ARCH),ppc64le)
+        ARCH_TAG=ppc64le
+      else
+        ARCH_TAG=x86
+      endif
    endif
  endif
 endif

+ifneq ($(ARCH),ppc64le)
+  ifneq ($(ARCH_TAG),arm32)
+    CXXFLAGS += -momit-leaf-frame-pointer
+  endif
+endif
+

 .PHONY: all release test clean

-all: build build/$(LIB_PROFILER) build/$(JATTACH) build/$(API_JAR) build/$(CONVERTER_JAR)
+all: build build/$(LIB_PROFILER) build/$(JATTACH) $(FDTRANSFER_BIN) build/$(API_JAR) build/$(CONVERTER_JAR)

-release: build $(PACKAGE_NAME).tar.gz
+release: build $(PACKAGE_NAME).$(PACKAGE_EXT)

-$(PACKAGE_NAME).tar.gz: build/$(LIB_PROFILER) build/$(JATTACH) \
-                        build/$(API_JAR) build/$(CONVERTER_JAR) \
-                        profiler.sh LICENSE *.md
+$(PACKAGE_NAME).tar.gz: $(PACKAGE_DIR)
+	tar czf $@ -C $(PACKAGE_DIR)/.. $(PACKAGE_NAME)
+	rm -r $(PACKAGE_DIR)
+
+$(PACKAGE_NAME).zip: $(PACKAGE_DIR)
+	codesign -s "Developer ID" -o runtime --timestamp -v $(PACKAGE_DIR)/build/$(JATTACH) $(PACKAGE_DIR)/build/$(LIB_PROFILER_SO)
+	ditto -c -k --keepParent $(PACKAGE_DIR) $@
+	rm -r $(PACKAGE_DIR)
+
+$(PACKAGE_DIR): build/$(LIB_PROFILER) build/$(JATTACH) $(FDTRANSFER_BIN) \
+                build/$(API_JAR) build/$(CONVERTER_JAR) \
+                profiler.sh LICENSE *.md
 	mkdir -p $(PACKAGE_DIR)
 	cp -RP build profiler.sh LICENSE *.md $(PACKAGE_DIR)
 	chmod -R 755 $(PACKAGE_DIR)
 	chmod 644 $(PACKAGE_DIR)/LICENSE $(PACKAGE_DIR)/*.md $(PACKAGE_DIR)/build/*.jar
-	tar cvzf $@ -C $(PACKAGE_DIR)/.. $(PACKAGE_NAME)
-	rm -r $(PACKAGE_DIR)

 %.$(SOEXT): %.so
+	rm -f $@
 	-ln -s $(<F) $@

 build:
 	mkdir -p build

-build/$(LIB_PROFILER_SO): $(SOURCES) $(HEADERS)
+build/$(LIB_PROFILER_SO): $(SOURCES) $(HEADERS) $(JAVA_HEADERS)
+ifeq ($(MERGE),true)
+	for f in src/*.cpp; do echo '#include "'$$f'"'; done |\
+	$(CXX) $(CXXFLAGS) -DPROFILER_VERSION=\"$(PROFILER_VERSION)\" $(INCLUDES) -fPIC -shared -o $@ -xc++ - $(LIBS)
+else
 	$(CXX) $(CXXFLAGS) -DPROFILER_VERSION=\"$(PROFILER_VERSION)\" $(INCLUDES) -fPIC -shared -o $@ $(SOURCES) $(LIBS)
+endif

-build/$(JATTACH): src/jattach/jattach.c
-	$(CC) $(CFLAGS) -DJATTACH_VERSION=\"$(JATTACH_VERSION)\" -o $@ $^
+build/$(JATTACH): src/jattach/*.c src/jattach/*.h
+	$(CC) $(CFLAGS) -DJATTACH_VERSION=\"$(PROFILER_VERSION)-ap\" -o $@ src/jattach/*.c
+
+build/fdtransfer: src/fdtransfer/*.cpp src/fdtransfer/*.h src/jattach/psutil.c src/jattach/psutil.h
+	$(CXX) $(CFLAGS) -o $@ src/fdtransfer/*.cpp src/jattach/psutil.c

 build/$(API_JAR): $(API_SOURCES)
 	mkdir -p build/api
 	$(JAVAC) -source $(JAVAC_RELEASE_VERSION) -target $(JAVAC_RELEASE_VERSION) -d build/api $^
-	$(JAR) cvf $@ -C build/api .
+	$(JAR) cf $@ -C build/api .
 	$(RM) -r build/api

 build/$(CONVERTER_JAR): $(CONVERTER_SOURCES) src/converter/MANIFEST.MF
 	mkdir -p build/converter
 	$(JAVAC) -source 7 -target 7 -d build/converter $(CONVERTER_SOURCES)
-	$(JAR) cvfm $@ src/converter/MANIFEST.MF -C build/converter .
+	$(JAR) cfm $@ src/converter/MANIFEST.MF -C build/converter .
 	$(RM) -r build/converter

+%.class.h: %.class
+	hexdump -v -e '1/1 "%u,"' $^ > $@
+
+%.class: %.java
+	$(JAVAC) -g:none -source $(JAVAC_RELEASE_VERSION) -target $(JAVAC_RELEASE_VERSION) $(*D)/*.java
+
 test: all
 	test/smoke-test.sh
 	test/thread-smoke-test.sh
 	test/alloc-smoke-test.sh
 	test/load-library-test.sh
+	test/fdtransfer-smoke-test.sh
 	echo "All tests passed"

 clean:
--- a/README.md
+++ b/README.md
@@ -1,7 +1,5 @@
 # async-profiler

-[![Build Status](https://travis-ci.org/jvm-profiling-tools/async-profiler.svg?branch=master)](https://travis-ci.org/jvm-profiling-tools/async-profiler)
-
 This project is a low overhead sampling profiler for Java
 that does not suffer from [Safepoint bias problem](http://psy-lob-saw.blogspot.ru/2016/02/why-most-sampling-java-profilers-are.html).
 It features HotSpot-specific APIs to collect stack traces
@@ -13,41 +11,616 @@ async-profiler can trace the following kinds of events:
 - Hardware and Software performance counters like cache misses, branch misses, page faults, context switches etc.
 - Allocations in Java Heap
 - Contented lock attempts, including both Java object monitors and ReentrantLocks
- 
-## Usage

-See our [Wiki](https://github.com/jvm-profiling-tools/async-profiler/wiki) or [3 hours playlist](https://www.youtube.com/playlist?list=PLNCLTEx3B8h4Yo_WvKWdLvI9mj1XpTKBr) to learn about all set of features. 
+See our [Wiki](https://github.com/jvm-profiling-tools/async-profiler/wiki) or
+[3 hours playlist](https://www.youtube.com/playlist?list=PLNCLTEx3B8h4Yo_WvKWdLvI9mj1XpTKBr)
+to learn about all features. 

 ## Download

-Latest release (1.8.3):
+Current release (2.8):

- - Linux x64 (glibc): [async-profiler-1.8.3-linux-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-linux-x64.tar.gz)
- - Linux x86 (glibc): [async-profiler-1.8.3-linux-x86.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-linux-x86.tar.gz)
- - Linux x64 (musl): [async-profiler-1.8.3-linux-musl-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-linux-musl-x64.tar.gz)
- - Linux ARM: [async-profiler-1.8.3-linux-arm.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-linux-arm.tar.gz)
- - Linux AArch64: [async-profiler-1.8.3-linux-aarch64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-linux-aarch64.tar.gz)
- - macOS x64: [async-profiler-1.8.3-macos-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v1.8.3/async-profiler-1.8.3-macos-x64.tar.gz)
-
-[Early access](https://github.com/jvm-profiling-tools/async-profiler/releases/tag/v2.0-b1) (2.0-b1):
-
- - Linux x64 (glibc): [async-profiler-2.0-b1-linux-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.0-b1/async-profiler-2.0-b1-linux-x64.tar.gz)
- - macOS x64: [async-profiler-2.0-b1-macos-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.0-b1/async-profiler-2.0-b1-macos-x64.tar.gz)
+ - Linux x64 (glibc): [async-profiler-2.8-linux-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.8/async-profiler-2.8-linux-x64.tar.gz)
+ - Linux x64 (musl): [async-profiler-2.8-linux-musl-x64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.8/async-profiler-2.8-linux-musl-x64.tar.gz)
+ - Linux arm64: [async-profiler-2.8-linux-arm64.tar.gz](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.8/async-profiler-2.8-linux-arm64.tar.gz)
+ - macOS x64/arm64: [async-profiler-2.8-macos.zip](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.8/async-profiler-2.8-macos.zip)
+ - Converters between profile formats: [converter.jar](https://github.com/jvm-profiling-tools/async-profiler/releases/download/v2.8/converter.jar)  
+   (JFR to Flame Graph, JFR to FlameScope, collapsed stacks to Flame Graph)

 [Previous releases](https://github.com/jvm-profiling-tools/async-profiler/releases)

+Note: async-profiler also comes bundled with IntelliJ IDEA Ultimate 2018.3 and later.
+For more information refer to [IntelliJ IDEA documentation](https://www.jetbrains.com/help/idea/cpu-profiler.html).
+
 ## Supported platforms

- **Linux** / x64 / x86 / ARM / AArch64
- **macOS** / x64
+ - **Linux** / x64 / x86 / arm64 / arm32 / ppc64le
+ - **macOS** / x64 / arm64

-Note: macOS profiling is limited to user space code only.
+### Community supported builds
+
+ - **Windows** / x64 - <img src="https://upload.wikimedia.org/wikipedia/commons/9/9c/IntelliJ_IDEA_Icon.svg" width="16" height="16"/> [IntelliJ IDEA](https://www.jetbrains.com/idea/) 2021.2 and later
+
+## CPU profiling
+
+In this mode profiler collects stack trace samples that include **Java** methods,
+**native** calls, **JVM** code and **kernel** functions.
+
+The general approach is receiving call stacks generated by `perf_events`
+and matching them up with call stacks generated by `AsyncGetCallTrace`,
+in order to produce an accurate profile of both Java and native code.
+Additionally, async-profiler provides a workaround to recover stack traces
+in some [corner cases](https://bugs.openjdk.java.net/browse/JDK-8178287)
+where `AsyncGetCallTrace` fails.
+
+This approach has the following advantages compared to using `perf_events`
+directly with a Java agent that translates addresses to Java method names:
+
+* Works on older Java versions because it doesn't require
+  `-XX:+PreserveFramePointer`, which is only available in JDK 8u60 and later.
+
+* Does not introduce the performance overhead from `-XX:+PreserveFramePointer`,
+  which can in rare cases be as high as 10%.
+
+* Does not require generating a map file to map Java code addresses to method
+  names.
+
+* Works with interpreter frames.
+
+* Does not require writing out a perf.data file for further processing in
+  user space scripts.
+
+If you wish to resolve frames within `libjvm`, the [debug symbols](#installing-debug-symbols) are required.
+
+## ALLOCATION profiling
+
+Instead of detecting CPU-consuming code, the profiler can be configured
+to collect call sites where the largest amount of heap memory is allocated.
+
+async-profiler does not use intrusive techniques like bytecode instrumentation
+or expensive DTrace probes which have significant performance impact.
+It also does not affect Escape Analysis or prevent from JIT optimizations
+like allocation elimination. Only actual heap allocations are measured.
+
+The profiler features TLAB-driven sampling. It relies on HotSpot-specific
+callbacks to receive two kinds of notifications:
+ - when an object is allocated in a newly created TLAB (aqua frames in a Flame Graph);
+ - when an object is allocated on a slow path outside TLAB (brown frames).
+
+This means not each allocation is counted, but only allocations every _N_ kB,
+where _N_ is the average size of TLAB. This makes heap sampling very cheap
+and suitable for production. On the other hand, the collected data
+may be incomplete, though in practice it will often reflect the top allocation
+sources.
+
+Sampling interval can be adjusted with `--alloc` option.
+For example, `--alloc 500k` will take one sample after 500 KB of allocated
+space on average. However, intervals less than TLAB size will not take effect.
+
+The minimum supported JDK version is 7u40 where the TLAB callbacks appeared.
+
+### Installing Debug Symbols
+
+The allocation profiler requires HotSpot debug symbols. Oracle JDK already has them
+embedded in `libjvm.so`, but in OpenJDK builds they are typically shipped
+in a separate package. For example, to install OpenJDK debug symbols on
+Debian / Ubuntu, run:
+```
+# apt install openjdk-8-dbg
+```
+or for OpenJDK 11:
+```
+# apt install openjdk-11-dbg
+```
+
+On CentOS, RHEL and some other RPM-based distributions, this could be done with
+[debuginfo-install](http://man7.org/linux/man-pages/man1/debuginfo-install.1.html) utility:
+```
+# debuginfo-install java-1.8.0-openjdk
+```
+
+On Gentoo the `icedtea` OpenJDK package can be built with the per-package setting
+`FEATURES="nostrip"` to retain symbols.
+
+The `gdb` tool can be used to verify if the debug symbols are properly installed for the `libjvm` library.
+For example on Linux:
+```
+$ gdb $JAVA_HOME/lib/server/libjvm.so -ex 'info address UseG1GC'
+```
+This command's output will either contain `Symbol "UseG1GC" is at 0xxxxx`
+or `No symbol "UseG1GC" in current context`.
+
+## Wall-clock profiling
+
+`-e wall` option tells async-profiler to sample all threads equally every given
+period of time regardless of thread status: Running, Sleeping or Blocked.
+For instance, this can be helpful when profiling application start-up time.
+
+Wall-clock profiler is most useful in per-thread mode: `-t`.
+
+Example: `./profiler.sh -e wall -t -i 5ms -f result.html 8983`
+
+## Java method profiling
+
+`-e ClassName.methodName` option instruments the given Java method
+in order to record all invocations of this method with the stack traces.
+
+Example: `-e java.util.Properties.getProperty` will profile all places
+where `getProperty` method is called from.
+
+Only non-native Java methods are supported. To profile a native method,
+use hardware breakpoint event instead, e.g. `-e Java_java_lang_Throwable_fillInStackTrace`
+
+**Be aware** that if you attach async-profiler at runtime, the first instrumentation
+of a non-native Java method may cause the [deoptimization](https://github.com/openjdk/jdk/blob/bf2e9ee9d321ed289466b2410f12ad10504d01a2/src/hotspot/share/prims/jvmtiRedefineClasses.cpp#L4092-L4096)
+of all compiled methods. The subsequent instrumentation flushes only the _dependent code_.
+
+The massive CodeCache flush doesn't occur if attaching async-profiler as an agent.
+
+Here are some useful native methods that you may want to profile:
+* ```G1CollectedHeap::humongous_obj_allocate``` - trace the _humongous allocation_ of the G1 GC,
+* ```JVM_StartThread``` - trace the new thread creation,
+* ```Java_java_lang_ClassLoader_defineClass1``` - trace class loading.

 ## Building

+Build status: [![Build Status](https://github.com/jvm-profiling-tools/async-profiler/actions/workflows/cpp.yml/badge.svg?branch=master)](https://github.com/jvm-profiling-tools/async-profiler/actions/workflows/cpp.yml)
+
 Make sure the `JAVA_HOME` environment variable points to your JDK installation,
 and then run `make`. GCC is required. After building, the profiler agent binary
 will be in the `build` subdirectory. Additionally, a small application `jattach`
 that can load the agent into the target process will also be compiled to the
 `build` subdirectory.

+## Basic Usage
+
+As of Linux 4.6, capturing kernel call stacks using `perf_events` from a non-root
+process requires setting two runtime variables. You can set them using
+sysctl or as follows:
+
+```
+# sysctl kernel.perf_event_paranoid=1
+# sysctl kernel.kptr_restrict=0
+```
+
+To run the agent and pass commands to it, the helper script `profiler.sh`
+is provided. A typical workflow would be to launch your Java application,
+attach the agent and start profiling, exercise your performance scenario, and
+then stop profiling. The agent's output, including the profiling results, will
+be displayed in the Java application's standard output.
+
+Example:
+
+```
+$ jps
+9234 Jps
+8983 Computey
+$ ./profiler.sh start 8983
+$ ./profiler.sh stop 8983
+```
+
+The following may be used in lieu of the `pid` (8983):
+
+ - The keyword `jps`, which will use the most recently launched Java process.
+ - The application name as it appears in the `jps` output: e.g. `Computey`
+
+Alternatively, you may specify `-d` (duration) argument to profile
+the application for a fixed period of time with a single command.
+
+```
+$ ./profiler.sh -d 30 8983
+```
+
+By default, the profiling frequency is 100Hz (every 10ms of CPU time).
+Here is a sample of the output printed to the Java application's terminal:
+
+```
+--- Execution profile ---
+Total samples:           687
+Unknown (native):        1 (0.15%)
+
+--- 6790000000 (98.84%) ns, 679 samples
+  [ 0] Primes.isPrime
+  [ 1] Primes.primesThread
+  [ 2] Primes.access$000
+  [ 3] Primes$1.run
+  [ 4] java.lang.Thread.run
+
+... a lot of output omitted for brevity ...
+
+          ns  percent  samples  top
+  ----------  -------  -------  ---
+  6790000000   98.84%      679  Primes.isPrime
+    40000000    0.58%        4  __do_softirq
+
+... more output omitted ...
+```
+
+This indicates that the hottest method was `Primes.isPrime`, and the hottest
+call stack leading to it comes from `Primes.primesThread`.
+
+## Launching as an Agent
+
+If you need to profile some code as soon as the JVM starts up, instead of using the `profiler.sh` script,
+it is possible to attach async-profiler as an agent on the command line. For example:
+
+```
+$ java -agentpath:/path/to/libasyncProfiler.so=start,event=cpu,file=profile.html ...
+```
+
+Agent library is configured through the JVMTI argument interface.
+The format of the arguments string is described
+[in the source code](https://github.com/jvm-profiling-tools/async-profiler/blob/v2.8/src/arguments.cpp#L52).
+The `profiler.sh` script actually converts command line arguments to that format.
+
+For instance, `-e wall` is converted to `event=wall`, `-f profile.html`
+is converted to `file=profile.html`, and so on. However, some arguments are processed
+directly by `profiler.sh` script. E.g. `-d 5` results in 3 actions:
+attaching profiler agent with start command, sleeping for 5 seconds,
+and then attaching the agent again with stop command.
+
+## Multiple events
+
+It is possible to profile CPU, allocations, and locks at the same time.
+Or, instead of CPU, you may choose any other execution event: wall-clock,
+perf event, tracepoint, Java method, etc.
+
+The only output format that supports multiple events together is JFR.
+The recording will contain the following event types:
+ - `jdk.ExecutionSample`
+ - `jdk.ObjectAllocationInNewTLAB` (alloc)
+ - `jdk.ObjectAllocationOutsideTLAB` (alloc)
+ - `jdk.JavaMonitorEnter` (lock)
+ - `jdk.ThreadPark` (lock)
+
+To start profiling cpu + allocations + locks together, specify
+```
+./profiler.sh -e cpu,alloc,lock -f profile.jfr ...
+```
+or use `--alloc` and `--lock` parameters with the desired threshold:
+```
+./profiler.sh -e cpu --alloc 2m --lock 10ms -f profile.jfr ...
+```
+The same, when starting profiler as an agent:
+```
+-agentpath:/path/to/libasyncProfiler.so=start,event=cpu,alloc=2m,lock=10ms,file=profile.jfr
+```
+
+## Flame Graph visualization
+
+async-profiler provides out-of-the-box [Flame Graph](https://github.com/BrendanGregg/FlameGraph) support.
+Specify `-o flamegraph` argument to dump profiling results as an interactive HTML Flame Graph.
+Also, Flame Graph output format will be chosen automatically if the target filename ends with `.html`.
+
+```
+$ jps
+9234 Jps
+8983 Computey
+$ ./profiler.sh -d 30 -f /tmp/flamegraph.html 8983
+```
+
+[![Example](https://github.com/jvm-profiling-tools/async-profiler/blob/master/demo/flamegraph.png)](https://htmlpreview.github.io/?https://github.com/jvm-profiling-tools/async-profiler/blob/master/demo/flamegraph.html)
+
+## Profiler Options
+
+The following is a complete list of the command-line options accepted by
+`profiler.sh` script.
+
+* `start` - starts profiling in semi-automatic mode, i.e. profiler will run
+  until `stop` command is explicitly called.
+
+* `resume` - starts or resumes earlier profiling session that has been stopped.
+  All the collected data remains valid. The profiling options are not preserved
+  between sessions, and should be specified again.
+
+* `stop` - stops profiling and prints the report.
+
+* `dump` - dump collected data without stopping profiling session.
+
+* `check` - check if the specified profiling event is available.
+
+* `status` - prints profiling status: whether profiler is active and
+  for how long.
+
+* `list` - show the list of available profiling events. This option still
+  requires PID, since supported events may differ depending on JVM version.
+
+* `-d N` - the profiling duration, in seconds. If no `start`, `resume`, `stop`
+  or `status` option is given, the profiler will run for the specified period
+  of time and then automatically stop.  
+  Example: `./profiler.sh -d 30 8983`
+
+* `-e event` - the profiling event: `cpu`, `alloc`, `lock`, `cache-misses` etc.
+  Use `list` to see the complete list of available events.
+
+  In allocation profiling mode the top frame of every call trace is the class
+  of the allocated object, and the counter is the heap pressure (the total size
+  of allocated TLABs or objects outside TLAB).
+
+  In lock profiling mode the top frame is the class of lock/monitor, and
+  the counter is number of nanoseconds it took to enter this lock/monitor.
+
+  Two special event types are supported on Linux: hardware breakpoints
+  and kernel tracepoints:
+    - `-e mem:<func>[:rwx]` sets read/write/exec breakpoint at function
+      `<func>`. The format of `mem` event is the same as in `perf-record`.
+      Execution breakpoints can be also specified by the function name,
+      e.g. `-e malloc` will trace all calls of native `malloc` function.
+    - `-e trace:<id>` sets a kernel tracepoint. It is possible to specify
+      tracepoint symbolic name, e.g. `-e syscalls:sys_enter_open` will trace
+      all `open` syscalls.
+
+* `-i N` - sets the profiling interval in nanoseconds or in other units,
+  if N is followed by `ms` (for milliseconds), `us` (for microseconds),
+  or `s` (for seconds). Only CPU active time is counted. No samples
+  are collected while CPU is idle. The default is 10000000 (10ms).  
+  Example: `./profiler.sh -i 500us 8983`
+
+* `--alloc N` - allocation profiling interval in bytes or in other units,
+  if N is followed by `k` (kilobytes), `m` (megabytes), or `g` (gigabytes).
+
+* `--lock N` - lock profiling threshold in nanoseconds (or other units).
+  In lock profiling mode, record contended locks that the JVM has waited for
+  longer than the specified duration.
+
+* `-j N` - sets the Java stack profiling depth. This option will be ignored if N is greater
+  than default 2048.  
+  Example: `./profiler.sh -j 30 8983`
+
+* `-t` - profile threads separately. Each stack trace will end with a frame
+  that denotes a single thread.  
+  Example: `./profiler.sh -t 8983`
+
+* `-s` - print simple class names instead of FQN.
+
+* `-g` - print method signatures.
+
+* `-a` - annotate JIT compiled methods with `_[j]` and inlined methods with `_[i]`.
+
+* `-l` - prepend library names to symbols, e.g. ``libjvm.so`JVM_DefineClassWithSource``.
+
+* `-o fmt` - specifies what information to dump when profiling ends.
+  `fmt` can be one of the following options:
+    - `traces[=N]` - dump call traces (at most N samples);
+    - `flat[=N]` - dump flat profile (top N hot methods);  
+      can be combined with `traces`, e.g. `traces=200,flat=200`
+    - `jfr` - dump events in Java Flight Recorder format readable by Java Mission Control.
+      This *does not* require JDK commercial features to be enabled.
+    - `collapsed` - dump collapsed call traces in the format used by
+      [FlameGraph](https://github.com/brendangregg/FlameGraph) script. This is
+      a collection of call stacks, where each line is a semicolon separated list
+      of frames followed by a counter.
+    - `flamegraph` - produce Flame Graph in HTML format.
+    - `tree` - produce Call Tree in HTML format.  
+      `--reverse` option will generate backtrace view.
+
+* `--total` - count the total value of the collected metric instead of the number of samples,
+  e.g. total allocation size.
+
+* `--chunksize N`, `--chunktime N` - approximate size and time limits for a single JFR chunk.
+  Example: `./profiler.sh -f profile.jfr --chunksize 100m --chunktime 1h 8983`
+
+* `-I include`, `-X exclude` - filter stack traces by the given pattern(s).
+  `-I` defines the name pattern that *must* be present in the stack traces,
+  while `-X` is the pattern that *must not* occur in any of stack traces in the output.
+  `-I` and `-X` options can be specified multiple times. A pattern may begin or end with
+  a star `*` that denotes any (possibly empty) sequence of characters.  
+  Example: `./profiler.sh -I 'Primes.*' -I 'java/*' -X '*Unsafe.park*' 8983`
+
+* `--title TITLE`, `--minwidth PERCENT`, `--reverse` - FlameGraph parameters.  
+  Example: `./profiler.sh -f profile.html --title "Sample CPU profile" --minwidth 0.5 8983`
+
+* `-f FILENAME` - the file name to dump the profile information to.  
+  `%p` in the file name is expanded to the PID of the target JVM;  
+  `%t` - to the timestamp;  
+  `%{ENV}` - to the value of the given environment variable.  
+  Example: `./profiler.sh -o collapsed -f /tmp/traces-%t.txt 8983`
+
+* `--loop TIME` - run profiler in a loop (continuous profiling).
+  The argument is either a clock time (`hh:mm:ss`) or
+  a loop duration in `s`econds, `m`inutes, `h`ours, or `d`ays.
+  Make sure the filename includes a timestamp pattern, or the output
+  will be overwritten on each iteration.  
+  Example: `./profiler.sh --loop 1h -f /var/log/profile-%t.jfr 8983`
+
+* `--all-user` - include only user-mode events. This option is helpful when kernel profiling
+  is restricted by `perf_event_paranoid` settings.  
+
+* `--sched` - group threads by Linux-specific scheduling policy: BATCH/IDLE/OTHER.
+
+* `--cstack MODE` - how to walk native frames (C stack). Possible modes are
+  `fp` (Frame Pointer), `dwarf` (DWARF unwind info),
+  `lbr` (Last Branch Record, available on Haswell since Linux 4.1),
+  and `no` (do not collect C stack).
+
+  By default, C stack is shown in cpu, itimer, wall-clock and perf-events profiles.
+  Java-level events like `alloc` and `lock` collect only Java stack.
+
+* `--begin function`, `--end function` - automatically start/stop profiling
+  when the specified native function is executed.
+
+* `--ttsp` - time-to-safepoint profiling. An alias for  
+  `--begin SafepointSynchronize::begin --end RuntimeService::record_safepoint_synchronized`  
+  It is not a separate event type, but rather a constraint. Whatever event type
+  you choose (e.g. `cpu` or `wall`), the profiler will work as usual, except that
+  only events between the safepoint request and the start of the VM operation
+  will be recorded.
+
+* `--jfrsync CONFIG` - start Java Flight Recording with the given configuration
+  synchronously with the profiler. The output .jfr file will include all regular
+  JFR events, except that execution samples will be obtained from async-profiler.
+  This option implies `-o jfr`.
+    - `CONFIG` is a predefined JFR profile or a JFR configuration file (.jfc).
+
+  Example: `./profiler.sh -e cpu --jfrsync profile -f combined.jfr 8983`
+
+* `--fdtransfer` - runs "fdtransfer" alongside, which is a small program providing an interface
+  for the profiler to access, `perf_event_open` even while this syscall is unavailable for the
+  profiled process (due to low privileges).
+  See [Profiling Java in a container](#profiling-java-in-a-container).
+
+* `-v`, `--version` - prints the version of profiler library. If PID is specified,
+  gets the version of the library loaded into the given process.
+
+## Profiling Java in a container
+
+It is possible to profile Java processes running in a Docker or LXC container
+both from within a container and from the host system.
+
+When profiling from the host, `pid` should be the Java process ID in the host
+namespace. Use `ps aux | grep java` or `docker top <container>` to find
+the process ID.
+
+async-profiler should be run from the host by a privileged user - it will
+automatically switch to the proper pid/mount namespace and change
+user credentials to match the target process. Also make sure that
+the target container can access `libasyncProfiler.so` by the same
+absolute path as on the host.
+
+By default, Docker container restricts the access to `perf_event_open`
+syscall. There are 3 alternatives to allow profiling in a container:
+1. You can modify the [seccomp profile](https://docs.docker.com/engine/security/seccomp/)
+or disable it altogether with `--security-opt seccomp=unconfined` option. In
+addition, `--cap-add SYS_ADMIN` may be required.
+2. You can use "fdtransfer": see the help for `--fdtransfer`.
+3. Last, you may fall back to `-e itimer` profiling mode, see [Troubleshooting](#troubleshooting).
+
+## Restrictions/Limitations
+
+* macOS profiling is limited to user space code only.
+
+* On most Linux systems, `perf_events` captures call stacks with a maximum depth
+  of 127 frames. On recent Linux kernels, this can be configured using
+  `sysctl kernel.perf_event_max_stack` or by writing to the
+  `/proc/sys/kernel/perf_event_max_stack` file.
+
+* Profiler allocates 8kB perf_event buffer for each thread of the target process.
+  Make sure `/proc/sys/kernel/perf_event_mlock_kb` value is large enough
+  (more than `8 * threads`) when running under unprivileged user.
+  Otherwise the message _"perf_event mmap failed: Operation not permitted"_
+  will be printed, and no native stack traces will be collected.
+
+* There is no bullet-proof guarantee that the `perf_events` overflow signal
+  is delivered to the Java thread in a way that guarantees no other code has run,
+  which means that in some rare cases, the captured Java stack might not match
+  the captured native (user+kernel) stack.
+
+* You will not see the non-Java frames _preceding_ the Java frames on the
+  stack. For example, if `start_thread` called `JavaMain` and then your Java
+  code started running, you will not see the first two frames in the resulting
+  stack. On the other hand, you _will_ see non-Java frames (user and kernel)
+  invoked by your Java code.
+
+* No Java stacks will be collected if `-XX:MaxJavaStackTraceDepth` is zero
+  or negative.
+
+* Too short profiling interval may cause continuous interruption of heavy
+  system calls like `clone()`, so that it will never complete;
+  see [#97](https://github.com/jvm-profiling-tools/async-profiler/issues/97).
+  The workaround is simply to increase the interval.
+
+* When agent is not loaded at JVM startup (by using -agentpath option) it is
+  highly recommended to use `-XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints` JVM flags.
+  Without those flags the profiler will still work correctly but results might be
+  less accurate. For example, without `-XX:+DebugNonSafepoints` there is a high chance
+  that simple inlined methods will not appear in the profile. When the agent is attached at runtime,
+  `CompiledMethodLoad` JVMTI event enables debug info, but only for methods compiled after attaching.
+
+## Troubleshooting
+
+```
+Failed to change credentials to match the target process: Operation not permitted
+```
+Due to limitation of HotSpot Dynamic Attach mechanism, the profiler must be run
+by exactly the same user (and group) as the owner of target JVM process.
+If profiler is run by a different user, it will try to automatically change
+current user and group. This will likely succeed for `root`, but not for
+other users, resulting in the above error.
+
+```
+Could not start attach mechanism: No such file or directory
+```
+The profiler cannot establish communication with the target JVM through UNIX domain socket.
+
+Usually this happens in one of the following cases:
+1. Attach socket `/tmp/.java_pidNNN` has been deleted. It is a common
+   practice to clean `/tmp` automatically with some scheduled script.
+   Configure the cleanup software to exclude `.java_pid*` files from deletion.  
+   How to check: run `lsof -p PID | grep java_pid`  
+   If it lists a socket file, but the file does not exist, then this is exactly
+   the described problem.
+2. JVM is started with `-XX:+DisableAttachMechanism` option.
+3. `/tmp` directory of Java process is not physically the same directory
+   as `/tmp` of your shell, because Java is running in a container or in
+   `chroot` environment. `jattach` attempts to solve this automatically,
+   but it might lack the required permissions to do so.  
+   Check `strace build/jattach PID properties`
+4. JVM is busy and cannot reach a safepoint. For instance,
+   JVM is in the middle of long-running garbage collection.  
+   How to check: run `kill -3 PID`. Healthy JVM process should print
+   a thread dump and heap info in its console.
+
+```
+Failed to inject profiler into <pid>
+```
+The connection with the target JVM has been established, but JVM is unable to load profiler shared library.
+Make sure the user of JVM process has permissions to access `libasyncProfiler.so` by exactly the same absolute path.
+For more information see [#78](https://github.com/jvm-profiling-tools/async-profiler/issues/78).
+
+```
+No access to perf events. Try --fdtransfer or --all-user option or 'sysctl kernel.perf_event_paranoid=1'
+```
+or
+```
+Perf events unavailable
+```
+`perf_event_open()` syscall has failed.
+
+Typical reasons include:
+1. `/proc/sys/kernel/perf_event_paranoid` is set to restricted mode (>=2).
+2. seccomp disables `perf_event_open` API in a container.
+3. OS runs under a hypervisor that does not virtualize performance counters.
+4. perf_event_open API is not supported on this system, e.g. WSL.
+
+For permissions-related reasons (such as 1 and 2), using `--fdtransfer` while running the profiler
+as a privileged user will allow using perf_events.
+
+If changing the configuration is not possible, you may fall back to
+`-e itimer` profiling mode. It is similar to `cpu` mode, but does not
+require perf_events support. As a drawback, there will be no kernel
+stack traces.
+
+```
+No AllocTracer symbols found. Are JDK debug symbols installed?
+```
+The OpenJDK debug symbols are required for allocation profiling.
+See [Installing Debug Symbols](#installing-debug-symbols) for more details.
+If the error message persists after a successful installation of the debug symbols,
+it is possible that the JDK was upgraded when installing the debug symbols.
+In this case, profiling any Java process which had started prior to the installation
+will continue to display this message, since the process had loaded
+the older version of the JDK which lacked debug symbols.
+Restarting the affected Java processes should resolve the issue.
+
+```
+VMStructs unavailable. Unsupported JVM?
+```
+JVM shared library does not export `gHotSpotVMStructs*` symbols -
+apparently this is not a HotSpot JVM. Sometimes the same message
+can be also caused by an incorrectly built JDK
+(see [#218](https://github.com/jvm-profiling-tools/async-profiler/issues/218)).
+In these cases installing JDK debug symbols may solve the problem.
+
+```
+Could not parse symbols from <libname.so>
+```
+Async-profiler was unable to parse non-Java function names because of
+the corrupted contents in `/proc/[pid]/maps`. The problem is known to
+occur in a container when running Ubuntu with Linux kernel 5.x.
+This is the OS bug, see https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1843018.
+
+```
+Could not open output file
+```
+Output file is written by the target JVM process, not by the profiler script.
+Make sure the path specified in `-f` option is correct and is accessible by the JVM.
--- a/demo/SwingSet2.svg
+++ b/demo/SwingSet2.svg
--- a/demo/flamegraph.html
+++ b/demo/flamegraph.html
@@ -0,0 +1,877 @@
+<!DOCTYPE html>
+<html lang='en'>
+<head>
+<meta charset='utf-8'>
+<style>
+	body {margin: 0; padding: 10px; background-color: #ffffff}
+	h1 {margin: 5px 0 0 0; font-size: 18px; font-weight: normal; text-align: center}
+	header {margin: -24px 0 5px 0; line-height: 24px}
+	button {font: 12px sans-serif; cursor: pointer}
+	p {margin: 5px 0 5px 0}
+	a {color: #0366d6}
+	#hl {position: absolute; display: none; overflow: hidden; white-space: nowrap; pointer-events: none; background-color: #ffffe0; outline: 1px solid #ffc000; height: 15px}
+	#hl span {padding: 0 3px 0 3px}
+	#status {overflow: hidden; white-space: nowrap}
+	#match {overflow: hidden; white-space: nowrap; display: none; float: right; text-align: right}
+	#reset {cursor: pointer}
+</style>
+</head>
+<body style='font: 12px Verdana, sans-serif'>
+<h1>Flame Graph</h1>
+<header style='text-align: left'><button id='reverse' title='Reverse'>&#x1f53b;</button>&nbsp;&nbsp;<button id='search' title='Search'>&#x1f50d;</button></header>
+<header style='text-align: right'>Produced by <a href='https://github.com/jvm-profiling-tools/async-profiler'>async-profiler</a></header>
+<canvas id='canvas' style='width: 100%; height: 752px'></canvas>
+<div id='hl'><span></span></div>
+<p id='match'>Matched: <span id='matchval'></span> <span id='reset' title='Clear'>&#x274c;</span></p>
+<p id='status'>&nbsp;</p>
+<script>
+	// Copyright 2020 Andrei Pangin
+	// Licensed under the Apache License, Version 2.0.
+	'use strict';
+	var root, rootLevel, px, pattern;
+	var reverse = false;
+	const levels = Array(47);
+	for (let h = 0; h < levels.length; h++) {
+		levels[h] = [];
+	}
+
+	const canvas = document.getElementById('canvas');
+	const c = canvas.getContext('2d');
+	const hl = document.getElementById('hl');
+	const status = document.getElementById('status');
+
+	const canvasWidth = canvas.offsetWidth;
+	const canvasHeight = canvas.offsetHeight;
+	canvas.style.width = canvasWidth + 'px';
+	canvas.width = canvasWidth * (devicePixelRatio || 1);
+	canvas.height = canvasHeight * (devicePixelRatio || 1);
+	if (devicePixelRatio) c.scale(devicePixelRatio, devicePixelRatio);
+	c.font = document.body.style.font;
+
+	const palette = [
+		[0x50e150, 30, 30, 30],
+		[0x50bebe, 30, 30, 30],
+		[0xe17d00, 30, 30,  0],
+		[0xc8c83c, 30, 30, 10],
+		[0xe15a5a, 30, 40, 40],
+	];
+
+	function getColor(p) {
+		const v = Math.random();
+		return '#' + (p[0] + ((p[1] * v) << 16 | (p[2] * v) << 8 | (p[3] * v))).toString(16);
+	}
+
+	function f(level, left, width, type, title) {
+		levels[level].push({left: left, width: width, color: getColor(palette[type]), title: title});
+	}
+
+	function samples(n) {
+		return n === 1 ? '1 sample' : n.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',') + ' samples';
+	}
+
+	function pct(a, b) {
+		return a >= b ? '100' : (100 * a / b).toFixed(2);
+	}
+
+	function findFrame(frames, x) {
+		let left = 0;
+		let right = frames.length - 1;
+
+		while (left <= right) {
+			const mid = (left + right) >>> 1;
+			const f = frames[mid];
+
+			if (f.left > x) {
+				right = mid - 1;
+			} else if (f.left + f.width <= x) {
+				left = mid + 1;
+			} else {
+				return f;
+			}
+		}
+
+		if (frames[left] && (frames[left].left - x) * px < 0.5) return frames[left];
+		if (frames[right] && (x - (frames[right].left + frames[right].width)) * px < 0.5) return frames[right];
+
+		return null;
+	}
+
+	function search(r) {
+		if (r && (r = prompt('Enter regexp to search:', '')) === null) {
+			return;
+		}
+
+		pattern = r ? RegExp(r) : undefined;
+		const matched = render(root, rootLevel);
+		document.getElementById('matchval').textContent = pct(matched, root.width) + '%';
+		document.getElementById('match').style.display = r ? 'inherit' : 'none';
+	}
+
+	function render(newRoot, newLevel) {
+		if (root) {
+			c.fillStyle = '#ffffff';
+			c.fillRect(0, 0, canvasWidth, canvasHeight);
+		}
+
+		root = newRoot || levels[0][0];
+		rootLevel = newLevel || 0;
+		px = canvasWidth / root.width;
+
+		const x0 = root.left;
+		const x1 = x0 + root.width;
+		const marked = [];
+
+		function mark(f) {
+			return marked[f.left] >= f.width || (marked[f.left] = f.width);
+		}
+
+		function totalMarked() {
+			let total = 0;
+			let left = 0;
+			for (let x in marked) {
+				if (+x >= left) {
+					total += marked[x];
+					left = +x + marked[x];
+				}
+			}
+			return total;
+		}
+
+		function drawFrame(f, y, alpha) {
+			if (f.left < x1 && f.left + f.width > x0) {
+				c.fillStyle = pattern && f.title.match(pattern) && mark(f) ? '#ee00ee' : f.color;
+				c.fillRect((f.left - x0) * px, y, f.width * px, 15);
+
+				if (f.width * px >= 21) {
+					const chars = Math.floor(f.width * px / 7);
+					const title = f.title.length <= chars ? f.title : f.title.substring(0, chars - 2) + '..';
+					c.fillStyle = '#000000';
+					c.fillText(title, Math.max(f.left - x0, 0) * px + 3, y + 12, f.width * px - 6);
+				}
+
+				if (alpha) {
+					c.fillStyle = 'rgba(255, 255, 255, 0.5)';
+					c.fillRect((f.left - x0) * px, y, f.width * px, 15);
+				}
+			}
+		}
+
+		for (let h = 0; h < levels.length; h++) {
+			const y = reverse ? h * 16 : canvasHeight - (h + 1) * 16;
+			const frames = levels[h];
+			for (let i = 0; i < frames.length; i++) {
+				drawFrame(frames[i], y, h < rootLevel);
+			}
+		}
+
+		return totalMarked();
+	}
+
+	canvas.onmousemove = function() {
+		const h = Math.floor((reverse ? event.offsetY : (canvasHeight - event.offsetY)) / 16);
+		if (h >= 0 && h < levels.length) {
+			const f = findFrame(levels[h], event.offsetX / px + root.left);
+			if (f) {
+				hl.style.left = (Math.max(f.left - root.left, 0) * px + canvas.offsetLeft) + 'px';
+				hl.style.width = (Math.min(f.width, root.width) * px) + 'px';
+				hl.style.top = ((reverse ? h * 16 : canvasHeight - (h + 1) * 16) + canvas.offsetTop) + 'px';
+				hl.firstChild.textContent = f.title;
+				hl.style.display = 'block';
+				canvas.title = f.title + '\n(' + samples(f.width) + ', ' + pct(f.width, levels[0][0].width) + '%)';
+				canvas.style.cursor = 'pointer';
+				canvas.onclick = function() {
+					if (f != root) {
+						render(f, h);
+						canvas.onmousemove();
+					}
+				};
+				status.textContent = 'Function: ' + canvas.title;
+				return;
+			}
+		}
+		canvas.onmouseout();
+	}
+
+	canvas.onmouseout = function() {
+		hl.style.display = 'none';
+		status.textContent = '\xa0';
+		canvas.title = '';
+		canvas.style.cursor = '';
+		canvas.onclick = '';
+	}
+
+	document.getElementById('reverse').onclick = function() {
+		reverse = !reverse;
+		render();
+	}
+
+	document.getElementById('search').onclick = function() {
+		search(true);
+	}
+
+	document.getElementById('reset').onclick = function() {
+		search(false);
+	}
+
+	window.onkeydown = function() {
+		if (event.ctrlKey && event.keyCode === 70) {
+			event.preventDefault();
+			search(true);
+		} else if (event.keyCode === 27) {
+			search(false);
+		}
+	}
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+f(17,439,7,0,'demo/parallel/Complex.plus')
+f(14,447,4,0,'javafx/scene/image/WritableImage$2.setColor')
+f(15,448,3,0,'javafx/scene/image/WritableImage$2.setArgb')
+f(16,449,2,0,'javafx/scene/image/Image.getWritablePlatformImage')
+f(4,451,125,0,'java/util/concurrent/ForkJoinTask.doExec')
+f(5,451,125,0,'java/util/concurrent/CountedCompleter.exec')
+f(6,451,125,0,'java/util/stream/ForEachOps$ForEachTask.compute')
+f(7,452,124,0,'java/util/stream/AbstractPipeline.copyInto')
+f(8,452,124,0,'java/util/Spliterator$OfInt.forEachRemaining')
+f(9,452,124,0,'java/util/stream/Streams$RangeIntSpliterator.forEachRemaining')
+f(10,452,124,0,'java/util/stream/ForEachOps$ForEachOp$OfInt.accept')
+f(11,452,124,0,'demo/parallel/MandelbrotSetTask$$Lambda$99/105194951.accept')
+f(12,452,124,0,'demo/parallel/MandelbrotSetTask.lambda$call$19')
+f(13,454,119,0,'demo/parallel/MandelbrotSetTask.calcAntialiasedPixel')
+f(14,462,111,0,'demo/parallel/MandelbrotSetTask.calcPixel')
+f(15,464,109,0,'demo/parallel/MandelbrotSetTask.calc')
+f(16,504,39,0,'demo/parallel/Complex.lengthSQ')
+f(16,543,22,0,'demo/parallel/Complex.plus')
+f(16,565,8,0,'demo/parallel/Complex.times')
+f(13,573,3,0,'javafx/scene/image/WritableImage$2.setColor')
+f(1,576,65,4,'start_thread')
+f(2,576,65,4,'java_start(Thread*)')
+f(3,576,4,3,'GCTaskThread::run()')
+f(4,577,3,3,'OldToYoungRootsTask::do_it(GCTaskManager*, unsigned int)')
+f(5,577,3,3,'CardTableExtension::scavenge_contents_parallel(ObjectStartArray*, MutableSpace*, HeapWord*, PSPromotionManager*, unsigned int, unsigned int)')
+f(6,577,3,3,'PSPromotionManager::drain_stacks_depth(bool)')
+f(7,578,2,3,'oopDesc* PSPromotionManager::copy_to_survivor_space<false>(oopDesc*)')
+f(3,580,61,3,'JavaThread::run()')
+f(4,580,61,3,'JavaThread::thread_main_inner()')
+f(5,580,61,3,'CompileBroker::compiler_thread_loop()')
+f(6,580,58,3,'CompileBroker::invoke_compiler_on_method(CompileTask*)')
+f(7,580,58,3,'C2Compiler::compile_method(ciEnv*, ciMethod*, int)')
+f(8,580,58,3,'Compile::Compile(ciEnv*, C2Compiler*, ciMethod*, int, bool, bool, bool)')
+f(9,580,32,3,'Compile::Code_Gen()')
+f(10,582,3,3,'PhaseCFG::do_global_code_motion()')
+f(11,582,3,3,'PhaseCFG::global_code_motion()')
+f(10,585,27,3,'PhaseChaitin::Register_Allocate()')
+f(11,585,2,3,'PhaseChaitin::Select()')
+f(12,585,2,3,'PhaseIFG::re_insert(unsigned int)')
+f(11,589,9,3,'PhaseChaitin::build_ifg_physical(ResourceArea*)')
+f(12,592,3,3,'PhaseChaitin::interfere_with_live(unsigned int, IndexSet*)')
+f(12,596,2,3,'RegMask::smear_to_sets(int)')
+f(11,599,3,3,'PhaseChaitin::gather_lrg_masks(bool)')
+f(11,602,5,3,'PhaseChaitin::post_allocate_copy_removal()')
+f(12,604,2,3,'PhaseChaitin::elide_copy(Node*, int, Block*, Node_List&, Node_List&, bool)')
+f(11,609,2,3,'PhaseIFG::init(unsigned int)')
+f(12,609,2,3,'IndexSet::initialize(unsigned int)')
+f(9,613,15,3,'Compile::Optimize()')
+f(10,614,13,3,'PhaseIdealLoop::build_and_optimize(bool, bool)')
+f(11,617,2,3,'PhaseIdealLoop::build_loop_early(VectorSet&, Node_List&, Node_Stack&)')
+f(11,619,4,3,'PhaseIdealLoop::build_loop_late(VectorSet&, Node_List&, Node_Stack&)')
+f(11,625,2,3,'PhaseIterGVN::optimize()')
+f(12,625,2,3,'PhaseIterGVN::transform_old(Node*)')
+f(9,629,3,3,'ParseGenerator::generate(JVMState*)')
+f(10,629,3,3,'Parse::Parse(JVMState*, ciMethod*, float)')
+f(11,629,3,3,'Parse::do_all_blocks()')
+f(12,629,3,3,'Parse::do_one_block()')
+f(13,629,3,3,'Parse::do_one_bytecode()')
+f(14,629,3,3,'Parse::do_call()')
+f(15,630,2,3,'PredictedCallGenerator::generate(JVMState*)')
+f(16,630,2,3,'ParseGenerator::generate(JVMState*)')
+f(17,630,2,3,'Parse::Parse(JVMState*, ciMethod*, float)')
+f(18,630,2,3,'Parse::do_all_blocks()')
+f(19,630,2,3,'Parse::do_one_block()')
+f(20,630,2,3,'Parse::do_one_bytecode()')
+f(21,630,2,3,'Parse::do_call()')
+f(9,632,6,3,'ciEnv::register_method(ciMethod*, int, CodeOffsets*, int, CodeBuffer*, int, OopMapSet*, ExceptionHandlerTable*, ImplicitExceptionTable*, AbstractCompiler*, int, bool, bool, RTMState)')
+f(10,632,6,3,'nmethod::post_compiled_method_load_event()')
+f(11,632,6,4,'pthread_cond_signal@@GLIBC_2.3.2')
+f(12,632,6,2,'entry_SYSCALL_64_after_hwframe')
+f(13,632,6,2,'do_syscall_64')
+f(14,632,6,2,'__x64_sys_futex')
+f(15,632,6,2,'do_futex')
+f(16,632,6,2,'wake_up_q')
+f(17,632,6,2,'try_to_wake_up')
+f(18,632,6,2,'_raw_spin_unlock_irqrestore')
+f(6,638,3,3,'CompileQueue::get()')
+f(7,638,3,4,'pthread_cond_signal@@GLIBC_2.3.2')
+f(8,638,3,2,'entry_SYSCALL_64_after_hwframe')
+f(9,638,3,2,'do_syscall_64')
+f(10,638,3,2,'__x64_sys_futex')
+f(11,638,3,2,'do_futex')
+f(12,638,3,2,'wake_up_q')
+f(13,638,3,2,'try_to_wake_up')
+f(14,638,3,2,'_raw_spin_unlock_irqrestore')
+render();
+</script></body></html>
--- a/demo/flamegraph.png
+++ b/demo/flamegraph.png
--- a/pom.xml
+++ b/pom.xml
@@ -3,7 +3,7 @@
    <modelVersion>4.0.0</modelVersion>
    <groupId>tools.profiler</groupId>
    <artifactId>async-profiler</artifactId>
-    <version>1.8.3</version>
+    <version>2.8</version>
    <packaging>jar</packaging>

    <name>async-profiler</name>
--- a/profiler.sh
+++ b/profiler.sh
@@ -7,7 +7,7 @@ usage() {
    echo "  start             start profiling and return immediately"
    echo "  resume            resume profiling without resetting collected data"
    echo "  stop              stop profiling"
-    echo "  jstack            get a thread dump"
+    echo "  dump              dump collected data without stopping profiling session"
    echo "  check             check if the specified profiling event is available"
    echo "  status            print profiling status"
    echo "  list              list profiling events supported by the target JVM"
@@ -22,8 +22,9 @@ usage() {
    echo "  -t                profile different threads separately"
    echo "  -s                simple class names instead of FQN"
    echo "  -g                print method signatures"
-    echo "  -a                annotate Java method names"
-    echo "  -o fmt            output format: flat|collapsed|html|tree|jfr"
+    echo "  -a                annotate Java methods"
+    echo "  -l                prepend library names"
+    echo "  -o fmt            output format: flat|traces|collapsed|flamegraph|tree|jfr"
    echo "  -I include        output only stack traces containing the specified pattern"
    echo "  -X exclude        exclude stack traces with the specified pattern"
    echo "  -v, --version     display version string"
@@ -32,17 +33,25 @@ usage() {
    echo "  --minwidth pct    skip frames smaller than pct%"
    echo "  --reverse         generate stack-reversed FlameGraph / Call tree"
    echo ""
-    echo "  --all-kernel      only include kernel-mode events"
+    echo "  --loop time       run profiler in a loop"
+    echo "  --alloc bytes     allocation profiling interval in bytes"
+    echo "  --lock duration   lock profiling threshold in nanoseconds"
+    echo "  --total           accumulate the total value (time, bytes, etc.)"
    echo "  --all-user        only include user-mode events"
-    echo "  --cstack mode     how to traverse C stack: fp|lbr|no"
+    echo "  --sched           group threads by scheduling policy"
+    echo "  --cstack mode     how to traverse C stack: fp|dwarf|lbr|no"
    echo "  --begin function  begin profiling when function is executed"
    echo "  --end function    end profiling when function is executed"
+    echo "  --ttsp            time-to-safepoint profiling"
+    echo "  --jfrsync config  synchronize profiler with JFR recording"
+    echo "  --fdtransfer      use fdtransfer to serve perf requests"
+    echo "                    from the non-privileged target"
    echo ""
    echo "<pid> is a numeric process ID of the target JVM"
    echo "      or 'jps' keyword to find running JVM automatically"
    echo "      or the application's name as it would appear in the jps tool"
    echo ""
-    echo "Example: $0 -d 30 -f profile.svg 3456"
+    echo "Example: $0 -d 30 -f profile.html 3456"
    echo "         $0 start -i 999000 jps"
    echo "         $0 stop -o flat jps"
    echo "         $0 -d 5 -e alloc MyAppName"
@@ -55,10 +64,25 @@ mirror_output() {
        if [ -f "$FILE" ]; then
            cat "$FILE"
            rm "$FILE"
+        elif [ -f "$ROOT_PREFIX$FILE" ]; then
+            cat "$ROOT_PREFIX$FILE"
+            rm "$ROOT_PREFIX$FILE"
        fi
    fi
 }

+mirror_log() {
+    # Try to access the log file both directly and through /proc/[pid]/root,
+    # in case the target namespace differs
+    if [ -f "$LOG" ]; then
+        cat "$LOG" >&2
+        rm "$LOG"
+    elif [ -f "$ROOT_PREFIX$LOG" ]; then
+        cat "$ROOT_PREFIX$LOG" >&2
+        rm "$ROOT_PREFIX$LOG"
+    fi
+}
+
 check_if_terminated() {
    if ! kill -0 "$PID" 2> /dev/null; then
        mirror_output
@@ -66,34 +90,48 @@ check_if_terminated() {
    fi
 }

+fdtransfer() {
+    if [ "$USE_FDTRANSFER" = "true" ]; then
+        "$FDTRANSFER" "$PID"
+    fi
+}
+
 jattach() {
    set +e
-    "$JATTACH" "$PID" load "$PROFILER" true "$1" > /dev/null
+    "$JATTACH" "$PID" load "$PROFILER" true "$1,log=$LOG" > /dev/null
    RET=$?
-    set -e

    # Check if jattach failed
    if [ $RET -ne 0 ]; then
        if [ $RET -eq 255 ]; then
            echo "Failed to inject profiler into $PID"
-            if [ "$(uname -s)" = "Darwin" ]; then
+            if [ "$UNAME_S" = "Darwin" ]; then
                otool -L "$PROFILER"
            else
-                ldd "$PROFILER"
+                LD_PRELOAD="$PROFILER" /bin/true
            fi
        fi
+
+        mirror_log
        exit $RET
    fi

+    mirror_log
    mirror_output
+    set -e
 }

-OPTIND=1
-SCRIPT_DIR="$(cd "$(dirname "$0")" > /dev/null 2>&1; pwd -P)"
+SCRIPT_BIN="$0"
+while [ -h "$SCRIPT_BIN" ]; do
+    SCRIPT_BIN="$(readlink "$SCRIPT_BIN")"
+done
+SCRIPT_DIR="$(cd "$(dirname "$SCRIPT_BIN")" > /dev/null 2>&1; pwd -P)"
+
 JATTACH=$SCRIPT_DIR/build/jattach
+FDTRANSFER=$SCRIPT_DIR/build/fdtransfer
+USE_FDTRANSFER="false"
 PROFILER=$SCRIPT_DIR/build/libasyncProfiler.so
 ACTION="collect"
-EVENT="cpu"
 DURATION="60"
 FILE=""
 USE_TMP="true"
@@ -107,19 +145,14 @@ while [ $# -gt 0 ]; do
        -h|"-?")
            usage
            ;;
-        start|resume|stop|check|status|list|collect)
+        start|resume|stop|dump|check|status|list|collect)
            ACTION="$1"
            ;;
-        jstack)
-            ACTION="start"
-            EVENT="jstack"
-            PARAMS="$PARAMS,threads"
-            ;;
        -v|--version)
            ACTION="version"
            ;;
        -e)
-            EVENT="$(echo "$2" | sed 's/,/,event=/g')"
+            PARAMS="$PARAMS,event=$2"
            shift
            ;;
        -d)
@@ -151,6 +184,9 @@ while [ $# -gt 0 ]; do
        -a)
            FORMAT="$FORMAT,ann"
            ;;
+        -l)
+            FORMAT="$FORMAT,lib"
+            ;;
        -o)
            OUTPUT="$2"
            shift
@@ -181,12 +217,26 @@ while [ $# -gt 0 ]; do
        --reverse)
            FORMAT="$FORMAT,reverse"
            ;;
-        --all-kernel)
-            PARAMS="$PARAMS,allkernel"
+        --samples|--total)
+            FORMAT="$FORMAT,${1#--}"
+            ;;
+        --alloc|--lock|--chunksize|--chunktime)
+            PARAMS="$PARAMS,${1#--}=$2"
+            shift
+            ;;
+        --timeout|--loop)
+            if [ "$ACTION" = "collect" ]; then
+                ACTION="start"
+            fi
+            PARAMS="$PARAMS,${1#--}=$2"
+            shift
            ;;
        --all-user)
            PARAMS="$PARAMS,alluser"
            ;;
+        --sched)
+            PARAMS="$PARAMS,sched"
+            ;;
        --cstack|--call-graph)
            PARAMS="$PARAMS,cstack=$2"
            shift
@@ -195,6 +245,18 @@ while [ $# -gt 0 ]; do
            PARAMS="$PARAMS,${1#--}=$2"
            shift
            ;;
+        --ttsp)
+            PARAMS="$PARAMS,begin=SafepointSynchronize::begin,end=RuntimeService::record_safepoint_synchronized"
+            ;;
+        --jfrsync)
+            OUTPUT="jfr"
+            PARAMS="$PARAMS,jfrsync=$2"
+            shift
+            ;;
+        --fdtransfer)
+            PARAMS="$PARAMS,fdtransfer"
+            USE_FDTRANSFER="true"
+            ;;
        --safe-mode)
            PARAMS="$PARAMS,safemode=$2"
            shift
@@ -249,27 +311,45 @@ else
            ;;
    esac
 fi
+LOG=/tmp/async-profiler-log.$$.$PID
+
+UNAME_S=$(uname -s)
+if [ "$UNAME_S" = "Linux" ]; then
+    ROOT_PREFIX="/proc/$PID/root"
+else
+    ROOT_PREFIX=""
+fi

 case $ACTION in
-    start|resume|check)
-        jattach "$ACTION,event=$EVENT,file=$FILE,$OUTPUT$FORMAT$PARAMS"
+    start|resume)
+        fdtransfer
+        jattach "$ACTION,file=$FILE,$OUTPUT$FORMAT$PARAMS"
        ;;
-    stop)
-        jattach "stop,file=$FILE,$OUTPUT$FORMAT"
+    check)
+        jattach "$ACTION,file=$FILE,$OUTPUT$FORMAT$PARAMS"
        ;;
-    status)
-        jattach "status,file=$FILE"
+    stop|dump)
+        jattach "$ACTION,file=$FILE,$OUTPUT$FORMAT"
        ;;
-    list)
-        jattach "list,file=$FILE"
+    status|list)
+        jattach "$ACTION,file=$FILE"
        ;;
    collect)
-        jattach "start,event=$EVENT,file=$FILE,$OUTPUT$FORMAT$PARAMS"
+        fdtransfer
+        jattach "start,file=$FILE,$OUTPUT$FORMAT$PARAMS"
+        echo Profiling for "$DURATION" seconds >&2
+        set +e
+        trap 'DURATION=0' INT
+
        while [ "$DURATION" -gt 0 ]; do
            DURATION=$(( DURATION-1 ))
            check_if_terminated
            sleep 1
        done
+
+        set -e
+        trap - INT
+        echo Done >&2
        jattach "stop,file=$FILE,$OUTPUT$FORMAT"
        ;;
    version)
--- a/src/allocTracer.cpp
+++ b/src/allocTracer.cpp
@@ -15,22 +15,21 @@
 */

 #include "allocTracer.h"
-#include "os.h"
 #include "profiler.h"
 #include "stackFrame.h"
 #include "vmStructs.h"


 int AllocTracer::_trap_kind;
-Trap AllocTracer::_in_new_tlab;
-Trap AllocTracer::_outside_tlab;
+Trap AllocTracer::_in_new_tlab(0);
+Trap AllocTracer::_outside_tlab(1);

 u64 AllocTracer::_interval;
 volatile u64 AllocTracer::_allocated_bytes;


 // Called whenever our breakpoint trap is hit
-void AllocTracer::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
+void AllocTracer::trapHandler(int signo, siginfo_t* siginfo, void* ucontext) {
    StackFrame frame(ucontext);
    int event_type;
    uintptr_t total_size;
@@ -51,6 +50,7 @@ void AllocTracer::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
        instance_size = 0;
    } else {
        // Not our trap
+        Profiler::instance()->trapHandler(signo, siginfo, ucontext);
        return;
    }

@@ -58,31 +58,13 @@ void AllocTracer::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
    uintptr_t klass = frame.arg0();
    frame.ret();

-    if (_enabled) {
-        // TODO: _enabled also uses traps
+    if (_enabled && updateCounter(_allocated_bytes, total_size, _interval)) {
        recordAllocation(ucontext, event_type, klass, total_size, instance_size);
    }
 }

 void AllocTracer::recordAllocation(void* ucontext, int event_type, uintptr_t rklass,
                                   uintptr_t total_size, uintptr_t instance_size) {
-    if (_interval) {
-        // Do not record allocation unless allocated at least _interval bytes
-        while (true) {
-            u64 prev = _allocated_bytes;
-            u64 next = prev + total_size;
-            if (next < _interval) {
-                if (__sync_bool_compare_and_swap(&_allocated_bytes, prev, next)) {
-                    return;
-                }
-            } else {
-                if (__sync_bool_compare_and_swap(&_allocated_bytes, prev, next % _interval)) {
-                    break;
-                }
-            }
-        }
-    }
-
    AllocEvent event;
    event._class_id = 0;
    event._total_size = total_size;
@@ -90,10 +72,10 @@ void AllocTracer::recordAllocation(void* ucontext, int event_type, uintptr_t rkl

    if (VMStructs::hasClassNames()) {
        VMSymbol* symbol = VMKlass::fromHandle(rklass)->name();
-        event._class_id = Profiler::_instance.classMap()->lookup(symbol->body(), symbol->length());
+        event._class_id = Profiler::instance()->classMap()->lookup(symbol->body(), symbol->length());
    }

-    Profiler::_instance.recordSample(ucontext, total_size, event_type, &event);
+    Profiler::instance()->recordSample(ucontext, total_size, event_type, &event);
 }

 Error AllocTracer::check(Arguments& args) {
@@ -101,7 +83,7 @@ Error AllocTracer::check(Arguments& args) {
        return Error::OK;
    }

-    NativeCodeCache* libjvm = VMStructs::libjvm();
+    CodeCache* libjvm = VMStructs::libjvm();
    const void* ne;
    const void* oe;

@@ -118,9 +100,9 @@ Error AllocTracer::check(Arguments& args) {
        return Error("No AllocTracer symbols found. Are JDK debug symbols installed?");
    }

-    if (!_in_new_tlab.assign(ne) || !_outside_tlab.assign(oe)) {
-        return Error("Unable to install allocation trap");
-    }
+    _in_new_tlab.assign(ne);
+    _outside_tlab.assign(oe);
+    _in_new_tlab.pair(_outside_tlab);

    return Error::OK;
 }
@@ -131,13 +113,12 @@ Error AllocTracer::start(Arguments& args) {
        return error;
    }

-    _interval = args._interval;
+    _interval = args._alloc > 0 ? args._alloc : 0;
    _allocated_bytes = 0;

-    OS::installSignalHandler(SIGTRAP, signalHandler);
-
-    _in_new_tlab.install();
-    _outside_tlab.install();
+    if (!_in_new_tlab.install() || !_outside_tlab.install()) {
+        return Error("Cannot install allocation breakpoints");
+    }

    return Error::OK;
 }
--- a/src/allocTracer.h
+++ b/src/allocTracer.h
@@ -32,27 +32,23 @@ class AllocTracer : public Engine {
    static u64 _interval;
    static volatile u64 _allocated_bytes;

-    static void signalHandler(int signo, siginfo_t* siginfo, void* ucontext);
-
    static void recordAllocation(void* ucontext, int event_type, uintptr_t rklass,
                                 uintptr_t total_size, uintptr_t instance_size);

  public:
-    const char* name() {
-        return "alloc";
+    const char* title() {
+        return "Allocation profile";
    }

    const char* units() {
        return "bytes";
    }

-    CStack cstack() {
-        return CSTACK_NO;
-    }
-
    Error check(Arguments& args);
    Error start(Arguments& args);
    void stop();
+
+    static void trapHandler(int signo, siginfo_t* siginfo, void* ucontext);
 };

 #endif // _ALLOCTRACER_H
--- a/src/api/one/profiler/AsyncProfiler.java
+++ b/src/api/one/profiler/AsyncProfiler.java
@@ -58,6 +58,9 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
     */
    @Override
    public void start(String event, long interval) throws IllegalStateException {
+        if (event == null) {
+            throw new NullPointerException();
+        }
        start0(event, interval, true);
    }

@@ -71,6 +74,9 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
     */
    @Override
    public void resume(String event, long interval) throws IllegalStateException {
+        if (event == null) {
+            throw new NullPointerException();
+        }
        start0(event, interval, false);
    }

@@ -116,7 +122,10 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
     * @throws IOException If failed to create output file
     */
    @Override
-    public String execute(String command) throws IllegalArgumentException, IOException {
+    public String execute(String command) throws IllegalArgumentException, IllegalStateException, IOException {
+        if (command == null) {
+            throw new NullPointerException();
+        }
        return execute0(command);
    }

@@ -129,7 +138,22 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
    @Override
    public String dumpCollapsed(Counter counter) {
        try {
-            return execute0("collapsed,counter=" + counter.name().toLowerCase());
+            return execute0("collapsed," + counter.name().toLowerCase());
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    /**
+     * Dump collected stack traces
+     *
+     * @param maxTraces Maximum number of stack traces to dump. 0 means no limit
+     * @return Textual representation of the profile
+     */
+    @Override
+    public String dumpTraces(int maxTraces) {
+        try {
+            return execute0(maxTraces == 0 ? "traces" : "traces=" + maxTraces);
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
@@ -144,7 +168,7 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
    @Override
    public String dumpFlat(int maxMethods) {
        try {
-            return execute0("flat=" + maxMethods);
+            return execute0(maxMethods == 0 ? "flat" : "flat=" + maxMethods);
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
@@ -171,7 +195,7 @@ public class AsyncProfiler implements AsyncProfilerMXBean {
    }

    private void filterThread(Thread thread, boolean enable) {
-        if (thread == null) {
+        if (thread == null || thread == Thread.currentThread()) {
            filterThread0(null, enable);
        } else {
            // Need to take lock to avoid race condition with a thread state change
@@ -186,6 +210,6 @@ public class AsyncProfiler implements AsyncProfilerMXBean {

    private native void start0(String event, long interval, boolean reset) throws IllegalStateException;
    private native void stop0() throws IllegalStateException;
-    private native String execute0(String command) throws IllegalArgumentException, IOException;
+    private native String execute0(String command) throws IllegalArgumentException, IllegalStateException, IOException;
    private native void filterThread0(Thread thread, boolean enable);
 }
--- a/src/api/one/profiler/AsyncProfilerMXBean.java
+++ b/src/api/one/profiler/AsyncProfilerMXBean.java
@@ -35,8 +35,9 @@ public interface AsyncProfilerMXBean {
    long getSamples();
    String getVersion();

-    String execute(String command) throws IllegalArgumentException, java.io.IOException;
+    String execute(String command) throws IllegalArgumentException, IllegalStateException, java.io.IOException;

    String dumpCollapsed(Counter counter);
+    String dumpTraces(int maxTraces);
    String dumpFlat(int maxMethods);
 }
--- a/src/arch.h
+++ b/src/arch.h
@@ -31,28 +31,42 @@ static inline int atomicInc(volatile int& var, int increment = 1) {
    return __sync_fetch_and_add(&var, increment);
 }

+static inline u64 loadAcquire(u64& var) {
+    return __atomic_load_n(&var, __ATOMIC_ACQUIRE);
+}
+
+static inline void storeRelease(u64& var, u64 value) {
+    return __atomic_store_n(&var, value, __ATOMIC_RELEASE);
+}
+

 #if defined(__x86_64__) || defined(__i386__)

 typedef unsigned char instruction_t;
 const instruction_t BREAKPOINT = 0xcc;
+const int BREAKPOINT_OFFSET = 0;

 const int SYSCALL_SIZE = 2;
+const int FRAME_PC_SLOT = 1;
+const int ADJUST_RET = 1;
 const int PLT_HEADER_SIZE = 16;
 const int PLT_ENTRY_SIZE = 16;
 const int PERF_REG_PC = 8;  // PERF_REG_X86_IP

 #define spinPause()       asm volatile("pause")
 #define rmb()             asm volatile("lfence" : : : "memory")
-#define flushCache(addr)  asm volatile("mfence; clflush (%0); mfence" : : "r"(addr) : "memory")
+#define flushCache(addr)  asm volatile("mfence; clflush (%0); mfence" : : "r" (addr) : "memory")

 #elif defined(__arm__) || defined(__thumb__)

 typedef unsigned int instruction_t;
 const instruction_t BREAKPOINT = 0xe7f001f0;
 const instruction_t BREAKPOINT_THUMB = 0xde01de01;
+const int BREAKPOINT_OFFSET = 0;

 const int SYSCALL_SIZE = sizeof(instruction_t);
+const int FRAME_PC_SLOT = 1;
+const int ADJUST_RET = 0;
 const int PLT_HEADER_SIZE = 20;
 const int PLT_ENTRY_SIZE = 12;
 const int PERF_REG_PC = 15;  // PERF_REG_ARM_PC
@@ -65,16 +79,38 @@ const int PERF_REG_PC = 15;  // PERF_REG_ARM_PC

 typedef unsigned int instruction_t;
 const instruction_t BREAKPOINT = 0xd4200000;
+const int BREAKPOINT_OFFSET = 0;

 const int SYSCALL_SIZE = sizeof(instruction_t);
+const int FRAME_PC_SLOT = 1;
+const int ADJUST_RET = 0;
 const int PLT_HEADER_SIZE = 32;
 const int PLT_ENTRY_SIZE = 16;
 const int PERF_REG_PC = 32;  // PERF_REG_ARM64_PC

-#define spinPause()       asm volatile("yield")
+#define spinPause()       asm volatile("isb")
 #define rmb()             asm volatile("dmb ish" : : : "memory")
 #define flushCache(addr)  __builtin___clear_cache((char*)(addr), (char*)(addr) + sizeof(instruction_t))

+#elif defined(__PPC64__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+
+typedef unsigned int instruction_t;
+const instruction_t BREAKPOINT = 0x7fe00008;
+// We place the break point in the third instruction slot on PPCLE as the first two are skipped if
+// the call comes from within the same compilation unit according to the LE ABI.
+const int BREAKPOINT_OFFSET = 8;
+
+const int SYSCALL_SIZE = sizeof(instruction_t);
+const int FRAME_PC_SLOT = 2;
+const int ADJUST_RET = 0;
+const int PLT_HEADER_SIZE = 24;
+const int PLT_ENTRY_SIZE = 24;
+const int PERF_REG_PC = 32;  // PERF_REG_POWERPC_NIP
+
+#define spinPause()       asm volatile("yield") // does nothing, but using or 1,1,1 would lead to other problems
+#define rmb()             asm volatile ("sync" : : : "memory") // lwsync would do but better safe than sorry
+#define flushCache(addr)  __builtin___clear_cache((char*)(addr), (char*)(addr) + sizeof(instruction_t))
+
 #else

 #error "Compiling on unsupported arch"
@@ -82,4 +118,22 @@ const int PERF_REG_PC = 32;  // PERF_REG_ARM64_PC
 #endif


+// Return address signing support.
+// Apple M1 has 47 bit virtual addresses.
+#if defined(__aarch64__) && defined(__APPLE__)
+#  define ADDRESS_BITS 47
+#  define WX_MEMORY    true
+#else
+#  define WX_MEMORY    false
+#endif
+
+#ifdef ADDRESS_BITS
+static inline const void* stripPointer(const void* p) {
+    return (const void*) ((unsigned long)p & ((1UL << ADDRESS_BITS) - 1));
+}
+#else
+#  define stripPointer(p)  (p)
+#endif
+
+
 #endif // _ARCH_H
--- a/src/arguments.cpp
+++ b/src/arguments.cpp
@@ -30,60 +30,80 @@ const Error Error::OK(NULL);
 // Extra buffer space for expanding file pattern
 const size_t EXTRA_BUF_SIZE = 512;

-// Statically compute hash code of a string containing up to 12 [a-z] letters
-#define HASH(s)    (HASH12(s "            "))
+static const Multiplier NANOS[] = {{'n', 1}, {'u', 1000}, {'m', 1000000}, {'s', 1000000000}, {0, 0}};
+static const Multiplier BYTES[] = {{'b', 1}, {'k', 1024}, {'m', 1048576}, {'g', 1073741824}, {0, 0}};
+static const Multiplier SECONDS[] = {{'s', 1}, {'m', 60}, {'h', 3600}, {'d', 86400}, {0, 0}};
+static const Multiplier UNIVERSAL[] = {{'n', 1}, {'u', 1000}, {'m', 1000000}, {'s', 1000000000}, {'b', 1}, {'k', 1024}, {'g', 1073741824}, {0, 0}};

-#define HASH12(s)  (s[0] & 31LL)       | (s[1] & 31LL) <<  5 | (s[2]  & 31LL) << 10 | (s[3]  & 31LL) << 15 | \
-                   (s[4] & 31LL) << 20 | (s[5] & 31LL) << 25 | (s[6]  & 31LL) << 30 | (s[7]  & 31LL) << 35 | \
-                   (s[8] & 31LL) << 40 | (s[9] & 31LL) << 45 | (s[10] & 31LL) << 50 | (s[11] & 31LL) << 55
+
+// Statically compute hash code of a string containing up to 12 [a-z] letters
+#define HASH(s)  ((s[0] & 31LL)       | (s[1] & 31LL) <<  5 | (s[2]  & 31LL) << 10 | (s[3]  & 31LL) << 15 | \
+                  (s[4] & 31LL) << 20 | (s[5] & 31LL) << 25 | (s[6]  & 31LL) << 30 | (s[7]  & 31LL) << 35 | \
+                  (s[8] & 31LL) << 40 | (s[9] & 31LL) << 45 | (s[10] & 31LL) << 50 | (s[11] & 31LL) << 55)

 // Simulate switch statement over string hashes
 #define SWITCH(arg)    long long arg_hash = hash(arg); if (0)

-#define CASE(s)        } else if (arg_hash == HASH(s)) {
+#define CASE(s)        } else if (arg_hash == HASH(s "            ")) {

-#define CASE2(s1, s2)  } else if (arg_hash == HASH(s1) || arg_hash == HASH(s2)) {
+#define DEFAULT()      } else {


 // Parses agent arguments.
 // The format of the string is:
 //     arg[,arg...]
 // where arg is one of the following options:
-//     start           - start profiling
-//     resume          - start or resume profiling without resetting collected data
-//     stop            - stop profiling
-//     check           - check if the specified profiling event is available
-//     status          - print profiling status (inactive / running for X seconds)
-//     list            - show the list of available profiling events
-//     version[=full]  - display the agent version
-//     event=EVENT     - which event to trace (cpu, alloc, lock, cache-misses etc.)
-//     collapsed[=C]   - dump collapsed stacks (the format used by FlameGraph script)
-//     html[=C]        - produce Flame Graph in HTML format
-//     tree[=C]        - produce call tree in HTML format
-//                       C is counter type: 'samples' or 'total'
-//     jfr             - dump events in Java Flight Recorder format
-//     flat[=N]        - dump top N methods (aka flat profile)
-//     interval=N      - sampling interval in ns (default: 10'000'000, i.e. 10 ms)
-//     jstackdepth=N   - maximum Java stack depth (default: 2048)
-//     safemode=BITS   - disable stack recovery techniques (default: 0, i.e. everything enabled)
-//     file=FILENAME   - output file name for dumping
-//     filter=FILTER   - thread filter
-//     threads         - profile different threads separately
-//     cstack=MODE     - how to collect C stack frames in addition to Java stack
-//                       MODE is 'fp' (Frame Pointer), 'lbr' (Last Branch Record) or 'no'
-//     allkernel       - include only kernel-mode events
-//     alluser         - include only user-mode events
-//     simple          - simple class names instead of FQN
-//     dot             - dotted class names
-//     sig             - print method signatures
-//     ann             - annotate Java method names
-//     include=PATTERN - include stack traces containing PATTERN
-//     exclude=PATTERN - exclude stack traces containing PATTERN
-//     begin=FUNCTION  - begin profiling when FUNCTION is executed
-//     end=FUNCTION    - end profiling when FUNCTION is executed
-//     title=TITLE     - FlameGraph title
-//     minwidth=PCT    - FlameGraph minimum frame width in percent
-//     reverse         - generate stack-reversed FlameGraph / Call tree
+//     start            - start profiling
+//     resume           - start or resume profiling without resetting collected data
+//     stop             - stop profiling
+//     dump             - dump collected data without stopping profiling session
+//     check            - check if the specified profiling event is available
+//     status           - print profiling status (inactive / running for X seconds)
+//     list             - show the list of available profiling events
+//     version[=full]   - display the agent version
+//     event=EVENT      - which event to trace (cpu, wall, cache-misses, etc.)
+//     alloc[=BYTES]    - profile allocations with BYTES interval
+//     lock[=DURATION]  - profile contended locks longer than DURATION ns
+//     collapsed        - dump collapsed stacks (the format used by FlameGraph script)
+//     flamegraph       - produce Flame Graph in HTML format
+//     tree             - produce call tree in HTML format
+//     jfr              - dump events in Java Flight Recorder format
+//     jfrsync[=CONFIG] - start Java Flight Recording with the given config along with the profiler 
+//     traces[=N]       - dump top N call traces
+//     flat[=N]         - dump top N methods (aka flat profile)
+//     samples          - count the number of samples (default)
+//     total            - count the total value (time, bytes, etc.) instead of samples
+//     chunksize=N      - approximate size of JFR chunk in bytes (default: 100 MB)
+//     chunktime=N      - duration of JFR chunk in seconds (default: 1 hour)
+//     timeout=TIME     - automatically stop profiler at TIME (absolute or relative)
+//     loop=TIME        - run profiler in a loop (continuous profiling)
+//     interval=N       - sampling interval in ns (default: 10'000'000, i.e. 10 ms)
+//     jstackdepth=N    - maximum Java stack depth (default: 2048)
+//     safemode=BITS    - disable stack recovery techniques (default: 0, i.e. everything enabled)
+//     file=FILENAME    - output file name for dumping
+//     log=FILENAME     - log warnings and errors to the given dedicated stream
+//     loglevel=LEVEL   - logging level: TRACE, DEBUG, INFO, WARN, ERROR, or NONE
+//     server=ADDRESS   - start insecure HTTP server at ADDRESS/PORT
+//     filter=FILTER    - thread filter
+//     threads          - profile different threads separately
+//     sched            - group threads by scheduling policy
+//     cstack=MODE      - how to collect C stack frames in addition to Java stack
+//                        MODE is 'fp' (Frame Pointer), 'dwarf', 'lbr' (Last Branch Record) or 'no'
+//     allkernel        - include only kernel-mode events
+//     alluser          - include only user-mode events
+//     fdtransfer       - use fdtransfer to pass fds to the profiler
+//     simple           - simple class names instead of FQN
+//     dot              - dotted class names
+//     sig              - print method signatures
+//     ann              - annotate Java methods
+//     lib              - prepend library names
+//     include=PATTERN  - include stack traces containing PATTERN
+//     exclude=PATTERN  - exclude stack traces containing PATTERN
+//     begin=FUNCTION   - begin profiling when FUNCTION is executed
+//     end=FUNCTION     - end profiling when FUNCTION is executed
+//     title=TITLE      - FlameGraph title
+//     minwidth=PCT     - FlameGraph minimum frame width in percent
+//     reverse          - generate stack-reversed FlameGraph / Call tree
 //
 // It is possible to specify multiple dump options at the same time

@@ -94,13 +114,15 @@ Error Arguments::parse(const char* args) {

    size_t len = strlen(args);
    free(_buf);
-    _buf = (char*)malloc(len + EXTRA_BUF_SIZE);
+    _buf = (char*)malloc(len + EXTRA_BUF_SIZE + 1);
    if (_buf == NULL) {
        return Error("Not enough memory to parse arguments");
    }
-    strcpy(_buf, args);
+    char* args_copy = strcpy(_buf + EXTRA_BUF_SIZE, args);

-    for (char* arg = strtok(_buf, ","); arg != NULL; arg = strtok(NULL, ",")) {
+    const char* msg = NULL;    
+
+    for (char* arg = strtok(args_copy, ","); arg != NULL; arg = strtok(NULL, ",")) {
        char* value = strchr(arg, '=');
        if (value != NULL) *value++ = 0;

@@ -115,6 +137,9 @@ Error Arguments::parse(const char* args) {
            CASE("stop")
                _action = ACTION_STOP;

+            CASE("dump")
+                _action = ACTION_DUMP;
+
            CASE("check")
                _action = ACTION_CHECK;

@@ -128,54 +153,125 @@ Error Arguments::parse(const char* args) {
                _action = value == NULL ? ACTION_VERSION : ACTION_FULL_VERSION;

            // Output formats
-            CASE2("collapsed", "folded")
+            CASE("collapsed")
                _output = OUTPUT_COLLAPSED;
-                _counter = value == NULL || strcmp(value, "samples") == 0 ? COUNTER_SAMPLES : COUNTER_TOTAL;

-            CASE2("flamegraph", "html")
+            CASE("flamegraph")
                _output = OUTPUT_FLAMEGRAPH;
-                _counter = value == NULL || strcmp(value, "samples") == 0 ? COUNTER_SAMPLES : COUNTER_TOTAL;

            CASE("tree")
                _output = OUTPUT_TREE;
-                _counter = value == NULL || strcmp(value, "samples") == 0 ? COUNTER_SAMPLES : COUNTER_TOTAL;

            CASE("jfr")
                _output = OUTPUT_JFR;
+                if (value != NULL) {
+                    _jfr_options = (int)strtol(value, NULL, 0);
+                }
+
+            CASE("jfrsync")
+                _output = OUTPUT_JFR;
+                _jfr_options = JFR_SYNC_OPTS;
+                _jfr_sync = value == NULL ? "default" : value;
+
+            CASE("traces")
+                _output = OUTPUT_TEXT;
+                _dump_traces = value == NULL ? INT_MAX : atoi(value);

            CASE("flat")
-                _output = OUTPUT_FLAT;
+                _output = OUTPUT_TEXT;
                _dump_flat = value == NULL ? INT_MAX : atoi(value);

+            CASE("samples")
+                _counter = COUNTER_SAMPLES;
+
+            CASE("total")
+                _counter = COUNTER_TOTAL;
+
+            CASE("chunksize")
+                if (value == NULL || (_chunk_size = parseUnits(value, BYTES)) < 0) {
+                    msg = "Invalid chunksize";
+                }
+
+            CASE("chunktime")
+                if (value == NULL || (_chunk_time = parseUnits(value, SECONDS)) < 0) {
+                    msg = "Invalid chunktime";
+                }
+
            // Basic options
            CASE("event")
                if (value == NULL || value[0] == 0) {
-                    return Error("event must not be empty");
+                    msg = "event must not be empty";
+                } else if (strcmp(value, EVENT_ALLOC) == 0) {
+                    if (_alloc < 0) _alloc = 0;
+                } else if (strcmp(value, EVENT_LOCK) == 0) {
+                    if (_lock < 0) _lock = 0;
+                } else if (_event != NULL) {
+                    msg = "Duplicate event argument";
+                } else {
+                    _event = value;
                }

-                if (!addEvent(value)) {
-                    return Error("multiple incompatible events");
+            CASE("timeout")
+                if (value == NULL || (_timeout = parseTimeout(value)) == -1 || !_persistent) {
+                    msg = "Invalid timeout";
+                }
+
+            CASE("loop")
+                _loop = true;
+                if (value == NULL || (_timeout = parseTimeout(value)) == -1 || !_persistent) {
+                    msg = "Invalid loop duration";
+                }
+
+            CASE("alloc")
+                _alloc = value == NULL ? 0 : parseUnits(value, BYTES);
+                if (_alloc < 0) {
+                    msg = "alloc must be >= 0";
+                }
+
+            CASE("lock")
+                _lock = value == NULL ? 0 : parseUnits(value, NANOS);
+                if (_lock < 0) {
+                    msg = "lock must be >= 0";
                }

            CASE("interval")
-                if (value == NULL || (_interval = parseUnits(value)) <= 0) {
-                    return Error("Invalid interval");
+                if (value == NULL || (_interval = parseUnits(value, UNIVERSAL)) <= 0) {
+                    msg = "Invalid interval";
                }

            CASE("jstackdepth")
                if (value == NULL || (_jstackdepth = atoi(value)) <= 0) {
-                    return Error("jstackdepth must be > 0");
+                    msg = "jstackdepth must be > 0";
                }

            CASE("safemode")
-                _safe_mode = value == NULL ? INT_MAX : atoi(value);
+                _safe_mode = value == NULL ? INT_MAX : (int)strtol(value, NULL, 0);

            CASE("file")
                if (value == NULL || value[0] == 0) {
-                    return Error("file must not be empty");
+                    msg = "file must not be empty";
                }
                _file = value;

+            CASE("log")
+                _log = value == NULL || value[0] == 0 ? NULL : value;
+
+            CASE("loglevel")
+                if (value == NULL || value[0] == 0) {
+                    msg = "loglevel must not be empty";
+                }
+                _loglevel = value;
+
+            CASE("server")
+                if (value == NULL || value[0] == 0) {
+                    msg = "server address must not be empty";
+                }
+                _server = value;
+
+            CASE("fdtransfer")
+                _fdtransfer = true;
+                _fdtransfer_path = value;
+
            // Filters
            CASE("filter")
                _filter = value == NULL ? "" : value;
@@ -189,6 +285,9 @@ Error Arguments::parse(const char* args) {
            CASE("threads")
                _threads = true;

+            CASE("sched")
+                _sched = true;
+
            CASE("allkernel")
                _ring = RING_KERNEL;

@@ -199,6 +298,8 @@ Error Arguments::parse(const char* args) {
                if (value != NULL) {
                    if (value[0] == 'n') {
                        _cstack = CSTACK_NO;
+                    } else if (value[0] == 'd') {
+                        _cstack = CSTACK_DWARF;
                    } else if (value[0] == 'l') {
                        _cstack = CSTACK_LBR;
                    } else {
@@ -219,6 +320,9 @@ Error Arguments::parse(const char* args) {
            CASE("ann")
                _style |= STYLE_ANNOTATE;

+            CASE("lib")
+                _style |= STYLE_LIB_NAMES;
+
            CASE("begin")
                _begin = value;

@@ -227,45 +331,49 @@ Error Arguments::parse(const char* args) {

            // FlameGraph options
            CASE("title")
-                if (value != NULL) _title = value;
+                _title = value;

            CASE("minwidth")
                if (value != NULL) _minwidth = atof(value);

            CASE("reverse")
                _reverse = true;
+
+            DEFAULT()
+                if (_unknown_arg == NULL) _unknown_arg = arg;
        }
    }

-    if (_file != NULL && strchr(_file, '%') != NULL) {
-        _file = expandFilePattern(_buf + len + 1, EXTRA_BUF_SIZE - 1, _file);
+    // Return error only after parsing all arguments, when 'log' is already set
+    if (msg != NULL) {
+        return Error(msg);
+    }
+
+    if (_event == NULL && _alloc < 0 && _lock < 0) {
+        _event = EVENT_CPU;
    }

    if (_file != NULL && _output == OUTPUT_NONE) {
        _output = detectOutputFormat(_file);
+        if (_output == OUTPUT_SVG) {
+            return Error("SVG format is obsolete, use .html for FlameGraph");
+        }
+        _dump_traces = 100;
        _dump_flat = 200;
    }

-    if (_output != OUTPUT_NONE && (_action == ACTION_NONE || _action == ACTION_STOP)) {
+    if (_action == ACTION_NONE && _output != OUTPUT_NONE) {
        _action = ACTION_DUMP;
    }

    return Error::OK;
 }

-bool Arguments::addEvent(const char* event) {
-    if (strcmp(event, EVENT_ALLOC) == 0) {
-        _events |= EK_ALLOC;
-    } else if (strcmp(event, EVENT_LOCK) == 0) {
-        _events |= EK_LOCK;
-    } else {
-        if (_events & EK_CPU) {
-            return false;
-        }
-        _events |= EK_CPU;
-        _event_desc = event;
+const char* Arguments::file() {
+    if (_file != NULL && strchr(_file, '%') != NULL) {
+        return expandFilePattern(_buf, EXTRA_BUF_SIZE - 1, _file);
    }
-    return true;
+    return _file;
 }

 // The linked list of string offsets is embedded right into _buf array
@@ -306,6 +414,19 @@ const char* Arguments::expandFilePattern(char* dest, size_t max_size, const char
                                t.tm_year + 1900, t.tm_mon + 1, t.tm_mday,
                                t.tm_hour, t.tm_min, t.tm_sec);
                continue;
+            } else if (c == '{') {
+                char env_key[128];
+                const char* p = strchr(pattern, '}');
+                if (p != NULL && p - pattern < sizeof(env_key)) {
+                    memcpy(env_key, pattern, p - pattern);
+                    env_key[p - pattern] = 0;
+                    const char* env_value = getenv(env_key);
+                    if (env_value != NULL) {
+                        ptr += snprintf(ptr, end - ptr, "%s", env_value);
+                        pattern = p + 1;
+                        continue;
+                    }
+                }
            }
        }
        *ptr++ = c;
@@ -324,31 +445,46 @@ Output Arguments::detectOutputFormat(const char* file) {
            return OUTPUT_JFR;
        } else if (strcmp(ext, ".collapsed") == 0 || strcmp(ext, ".folded") == 0) {
            return OUTPUT_COLLAPSED;
+        } else if (strcmp(ext, ".svg") == 0) {
+            return OUTPUT_SVG;
        }
    }
-    return OUTPUT_FLAT;
+    return OUTPUT_TEXT;
 }

-long Arguments::parseUnits(const char* str) {
+long Arguments::parseUnits(const char* str, const Multiplier* multipliers) {
    char* end;
    long result = strtol(str, &end, 0);

-    switch (*end) {
-        case 0:
-            return result;
-        case 'K': case 'k':
-        case 'U': case 'u': // microseconds
-            return result * 1000;
-        case 'M': case 'm': // million, megabytes or milliseconds
-            return result * 1000000;
-        case 'G': case 'g':
-        case 'S': case 's': // seconds
-            return result * 1000000000;
+    char c = *end;
+    if (c == 0) {
+        return result;
+    }
+    if (c >= 'A' && c <= 'Z') {
+        c += 'a' - 'A';
+    }
+
+    for (const Multiplier* m = multipliers; m->symbol; m++) {
+        if (c == m->symbol) {
+            return result * m->multiplier;
+        }
    }

    return -1;
 }

+int Arguments::parseTimeout(const char* str) {
+    const char* p = strchr(str, ':');
+    if (p == NULL) {
+        return parseUnits(str, SECONDS);
+    }
+
+    int hh = str[0] >= '0' && str[0] <= '2' ? atoi(str) : 0xff;
+    int mm = p[1] >= '0' && p[1] <= '5' ? atoi(p + 1) : 0xff;
+    int ss = (p = strchr(p + 1, ':')) != NULL && p[1] >= '0' && p[1] <= '5' ? atoi(p + 1) : 0xff;
+    return 0xff000000 | hh << 16 | mm << 8 | ss;
+}
+
 Arguments::~Arguments() {
    if (!_shared) free(_buf);
 }
--- a/src/arguments.h
+++ b/src/arguments.h
@@ -20,7 +20,8 @@
 #include <stddef.h>


-const long DEFAULT_INTERVAL = 10000000;  // 10 ms
+const long DEFAULT_INTERVAL = 10000000;      // 10 ms
+const long DEFAULT_ALLOC_INTERVAL = 524287;  // 512 KiB
 const int DEFAULT_JSTACKDEPTH = 2048;

 const char* const EVENT_CPU    = "cpu";
@@ -28,19 +29,18 @@ const char* const EVENT_ALLOC  = "alloc";
 const char* const EVENT_LOCK   = "lock";
 const char* const EVENT_WALL   = "wall";
 const char* const EVENT_ITIMER = "itimer";
-const char* const EVENT_JSTACK = "jstack";

 enum Action {
    ACTION_NONE,
    ACTION_START,
    ACTION_RESUME,
    ACTION_STOP,
+    ACTION_DUMP,
    ACTION_CHECK,
    ACTION_STATUS,
    ACTION_LIST,
    ACTION_VERSION,
-    ACTION_FULL_VERSION,
-    ACTION_DUMP
+    ACTION_FULL_VERSION
 };

 enum Counter {
@@ -54,35 +54,47 @@ enum Ring {
    RING_USER
 };

-enum EventKind {
-    EK_CPU   = 1,
-    EK_ALLOC = 2,
-    EK_LOCK  = 4
-};
-
 enum Style {
    STYLE_SIMPLE     = 1,
    STYLE_DOTTED     = 2,
    STYLE_SIGNATURES = 4,
-    STYLE_ANNOTATE   = 8
+    STYLE_ANNOTATE   = 8,
+    STYLE_LIB_NAMES  = 16
 };

 enum CStack {
    CSTACK_DEFAULT,
    CSTACK_NO,
    CSTACK_FP,
+    CSTACK_DWARF,
    CSTACK_LBR
 };

 enum Output {
    OUTPUT_NONE,
-    OUTPUT_FLAT,
+    OUTPUT_TEXT,
+    OUTPUT_SVG,  // obsolete
    OUTPUT_COLLAPSED,
    OUTPUT_FLAMEGRAPH,
    OUTPUT_TREE,
    OUTPUT_JFR
 };

+enum JfrOption {
+    NO_SYSTEM_INFO  = 0x1,
+    NO_SYSTEM_PROPS = 0x2,
+    NO_NATIVE_LIBS  = 0x4,
+    NO_CPU_LOAD     = 0x8,
+
+    JFR_SYNC_OPTS   = NO_SYSTEM_INFO | NO_SYSTEM_PROPS | NO_NATIVE_LIBS | NO_CPU_LOAD
+};
+
+
+struct Multiplier {
+    char symbol;
+    long multiplier;
+};
+

 class Error {
  private:
@@ -108,31 +120,48 @@ class Arguments {
  private:
    char* _buf;
    bool _shared;
+    bool _persistent;

    void appendToEmbeddedList(int& list, char* value);

    static long long hash(const char* arg);
    static const char* expandFilePattern(char* dest, size_t max_size, const char* pattern);
    static Output detectOutputFormat(const char* file);
-    static long parseUnits(const char* str);
+    static long parseUnits(const char* str, const Multiplier* multipliers);
+    static int parseTimeout(const char* str);

  public:
    Action _action;
    Counter _counter;
    Ring _ring;
-    int _events;
-    const char* _event_desc;
+    const char* _event;
+    int _timeout;
    long _interval;
+    long _alloc;
+    long _lock;
    int  _jstackdepth;
    int _safe_mode;
    const char* _file;
+    const char* _log;
+    const char* _loglevel;
+    const char* _unknown_arg;
+    const char* _server;
    const char* _filter;
    int _include;
    int _exclude;
+    bool _loop;
    bool _threads;
+    bool _sched;
+    bool _fdtransfer;
+    const char* _fdtransfer_path;
    int _style;
    CStack _cstack;
    Output _output;
+    long _chunk_size;
+    long _chunk_time;
+    const char* _jfr_sync;
+    int _jfr_options;
+    int _dump_traces;
    int _dump_flat;
    const char* _begin;
    const char* _end;
@@ -141,28 +170,45 @@ class Arguments {
    double _minwidth;
    bool _reverse;

-    Arguments() :
+    Arguments(bool persistent = false) :
        _buf(NULL),
        _shared(false),
+        _persistent(persistent),
        _action(ACTION_NONE),
        _counter(COUNTER_SAMPLES),
        _ring(RING_ANY),
-        _events(0),
-        _event_desc(NULL),
+        _event(NULL),
+        _timeout(0),
        _interval(0),
+        _alloc(-1),
+        _lock(-1),
        _jstackdepth(DEFAULT_JSTACKDEPTH),
        _safe_mode(0),
        _file(NULL),
+        _log(NULL),
+        _loglevel(NULL),
+        _unknown_arg(NULL),
+        _server(NULL),
        _filter(NULL),
        _include(0),
        _exclude(0),
+        _loop(false),
        _threads(false),
+        _sched(false),
+        _fdtransfer(false),
+        _fdtransfer_path(NULL),
        _style(0),
        _cstack(CSTACK_DEFAULT),
        _output(OUTPUT_NONE),
+        _chunk_size(100 * 1024 * 1024),
+        _chunk_time(3600),
+        _jfr_sync(NULL),
+        _jfr_options(0),
+        _dump_traces(0),
+        _dump_flat(0),
        _begin(NULL),
        _end(NULL),
-        _title("Flame Graph"),
+        _title(NULL),
        _minwidth(0),
        _reverse(false) {
    }
@@ -173,7 +219,16 @@ class Arguments {

    Error parse(const char* args);

-    bool addEvent(const char* event);
+    const char* file();
+
+    bool hasOutputFile() const {
+        return _file != NULL &&
+            (_action == ACTION_STOP || _action == ACTION_DUMP ? _output != OUTPUT_JFR : _action >= ACTION_STATUS);
+    }
+
+    bool hasOption(JfrOption option) const {
+        return (_jfr_options & option) != 0;
+    }

    friend class FrameName;
    friend class Recording;
--- a/src/callTraceStorage.cpp
+++ b/src/callTraceStorage.cpp
@@ -15,14 +15,13 @@
 */

 #include <string.h>
-#include <unistd.h>
 #include "callTraceStorage.h"
 #include "os.h"


 static const u32 INITIAL_CAPACITY = 65536;
 static const u32 CALL_TRACE_CHUNK = 8 * 1024 * 1024;
-static const size_t PAGE_ALIGNMENT = sysconf(_SC_PAGESIZE) - 1;
+static const u32 OVERFLOW_TRACE_ID = 0x7fffffff;


 class LongHashTable {
@@ -36,7 +35,7 @@ class LongHashTable {

    static size_t getSize(u32 capacity) {
        size_t size = sizeof(LongHashTable) + (sizeof(u64) + sizeof(CallTraceSample)) * capacity;
-        return (size + PAGE_ALIGNMENT) & ~PAGE_ALIGNMENT;
+        return (size + OS::page_mask) & ~OS::page_mask;
    }

  public:
@@ -87,8 +86,11 @@ class LongHashTable {
 };


+CallTrace CallTraceStorage::_overflow_trace = {1, {BCI_ERROR, (jmethodID)"storage_overflow"}};
+
 CallTraceStorage::CallTraceStorage() : _allocator(CALL_TRACE_CHUNK) {
    _current_table = LongHashTable::allocate(NULL, INITIAL_CAPACITY);
+    _overflow = 0;
 }

 CallTraceStorage::~CallTraceStorage() {
@@ -103,6 +105,7 @@ void CallTraceStorage::clear() {
    }
    _current_table->clear();
    _allocator.clear();
+    _overflow = 0;
 }

 void CallTraceStorage::collectTraces(std::map<u32, CallTrace*>& map) {
@@ -112,11 +115,20 @@ void CallTraceStorage::collectTraces(std::map<u32, CallTrace*>& map) {
        u32 capacity = table->capacity();

        for (u32 slot = 0; slot < capacity; slot++) {
-            if (keys[slot] != 0) {
-                map[capacity - (INITIAL_CAPACITY - 1) + slot] = values[slot].trace;
+            if (keys[slot] != 0 && loadAcquire(values[slot].samples) != 0) {
+                // Reset samples to avoid duplication of call traces between JFR chunks
+                values[slot].samples = 0;
+                CallTrace* trace = values[slot].acquireTrace();
+                if (trace != NULL) {
+                    map[capacity - (INITIAL_CAPACITY - 1) + slot] = trace;
+                }
            }
        }
    }
+
+    if (_overflow > 0) {
+        map[OVERFLOW_TRACE_ID] = &_overflow_trace;
+    }
 }

 void CallTraceStorage::collectSamples(std::vector<CallTraceSample*>& samples) {
@@ -133,6 +145,20 @@ void CallTraceStorage::collectSamples(std::vector<CallTraceSample*>& samples) {
    }
 }

+void CallTraceStorage::collectSamples(std::map<u64, CallTraceSample>& map) {
+    for (LongHashTable* table = _current_table; table != NULL; table = table->prev()) {
+        u64* keys = table->keys();
+        CallTraceSample* values = table->values();
+        u32 capacity = table->capacity();
+
+        for (u32 slot = 0; slot < capacity; slot++) {
+            if (keys[slot] != 0 && values[slot].acquireTrace() != NULL) {
+                map[keys[slot]] += values[slot];
+            }
+        }
+    }
+}
+
 // Adaptation of MurmurHash64A by Austin Appleby
 u64 CallTraceStorage::calcHash(int num_frames, ASGCT_CallFrame* frames) {
    const u64 M = 0xc6a4a7935bd1e995ULL;
@@ -225,19 +251,19 @@ u32 CallTraceStorage::put(int num_frames, ASGCT_CallFrame* frames, u64 counter)
            if (trace == NULL) {
                trace = storeCallTrace(num_frames, frames);
            }
-            table->values()[slot].trace = trace;
+            table->values()[slot].setTrace(trace);
            break;
        }

        if (++step >= capacity) {
            // Very unlikely case of a table overflow
-            return 0;
+            atomicInc(_overflow);
+            return OVERFLOW_TRACE_ID;
        }
        // Improved version of linear probing
        slot = (slot + step) & (capacity - 1);
    }

-    // TODO: check overhead
    CallTraceSample& s = table->values()[slot];
    atomicInc(s.samples);
    atomicInc(s.counter, counter);
--- a/src/callTraceStorage.h
+++ b/src/callTraceStorage.h
@@ -35,12 +35,34 @@ struct CallTraceSample {
    CallTrace* trace;
    u64 samples;
    u64 counter;
+
+    CallTrace* acquireTrace() {
+        return __atomic_load_n(&trace, __ATOMIC_ACQUIRE);
+    }
+
+    void setTrace(CallTrace* value) {
+        return __atomic_store_n(&trace, value, __ATOMIC_RELEASE);
+    }
+
+    CallTraceSample& operator+=(const CallTraceSample& s) {
+        trace = s.trace;
+        samples += s.samples;
+        counter += s.counter;
+        return *this;
+    }
+
+    bool operator<(const CallTraceSample& other) const {
+        return counter > other.counter;
+    }
 };

 class CallTraceStorage {
  private:
+    static CallTrace _overflow_trace;
+
    LinearAllocator _allocator;
    LongHashTable* _current_table;
+    u64 _overflow;

    u64 calcHash(int num_frames, ASGCT_CallFrame* frames);
    CallTrace* storeCallTrace(int num_frames, ASGCT_CallFrame* frames);
@@ -53,6 +75,7 @@ class CallTraceStorage {
    void clear();
    void collectTraces(std::map<u32, CallTrace*>& map);
    void collectSamples(std::vector<CallTraceSample*>& samples);
+    void collectSamples(std::map<u64, CallTraceSample>& map);

    u32 put(int num_frames, ASGCT_CallFrame* frames, u64 counter);
 };
--- a/src/codeCache.cpp
+++ b/src/codeCache.cpp
@@ -17,26 +17,66 @@
 #include <stdlib.h>
 #include <string.h>
 #include "codeCache.h"
+#include "dwarf.h"


+char* NativeFunc::create(const char* name, short lib_index) {
+    NativeFunc* f = (NativeFunc*)malloc(sizeof(NativeFunc) + 1 + strlen(name));
+    f->_lib_index = lib_index;
+    f->_mark = 0;
+    return strcpy(f->_name, name);
+}
+
+void NativeFunc::destroy(char* name) {
+    free(from(name));
+}
+
+
+CodeCache::CodeCache(const char* name, short lib_index, const void* min_address, const void* max_address) {
+    _name = NativeFunc::create(name, -1);
+    _lib_index = lib_index;
+    _min_address = min_address;
+    _max_address = max_address;
+    _text_base = NULL;
+
+    _got_start = NULL;
+    _got_end = NULL;
+
+    _dwarf_table = NULL;
+    _dwarf_table_length = 0;
+
+    _capacity = INITIAL_CODE_CACHE_CAPACITY;
+    _count = 0;
+    _blobs = new CodeBlob[_capacity];
+}
+
+CodeCache::~CodeCache() {
+    for (int i = 0; i < _count; i++) {
+        NativeFunc::destroy(_blobs[i]._name);
+    }
+    NativeFunc::destroy(_name);
+    delete[] _blobs;
+    free(_dwarf_table);
+}
+
 void CodeCache::expand() {
    CodeBlob* old_blobs = _blobs;
    CodeBlob* new_blobs = new CodeBlob[_capacity * 2];

-    int live = 0;
-    for (int i = 0; i < _count; i++) {
-        if (_blobs[i]._method != NULL) {
-            new_blobs[live++] = _blobs[i];
-        }
-    }
+    memcpy(new_blobs, old_blobs, _count * sizeof(CodeBlob));

-    _count = live;
    _capacity *= 2;
    _blobs = new_blobs;
    delete[] old_blobs;
 }

-void CodeCache::add(const void* start, int length, jmethodID method, bool update_bounds) {
+void CodeCache::add(const void* start, int length, const char* name, bool update_bounds) {
+    char* name_copy = NativeFunc::create(name, _lib_index);
+    // Replace non-printable characters
+    for (char* s = name_copy; *s != 0; s++) {
+        if (*s < ' ') *s = '?';
+    }
+
    if (_count >= _capacity) {
        expand();
    }
@@ -44,58 +84,20 @@ void CodeCache::add(const void* start, int length, jmethodID method, bool update
    const void* end = (const char*)start + length;
    _blobs[_count]._start = start;
    _blobs[_count]._end = end;
-    _blobs[_count]._method = method;
+    _blobs[_count]._name = name_copy;
    _count++;

    if (update_bounds) {
-        if (start < _min_address) _min_address = start;
-        if (end > _max_address) _max_address = end;
+        updateBounds(start, end);
    }
 }

-void CodeCache::remove(const void* start, jmethodID method) {
-    for (int i = 0; i < _count; i++) {
-        if (_blobs[i]._start == start && _blobs[i]._method == method) {
-            _blobs[i]._method = NULL;
-            return;
-        }
-    }
+void CodeCache::updateBounds(const void* start, const void* end) {
+    if (start < _min_address) _min_address = start;
+    if (end > _max_address) _max_address = end;
 }

-jmethodID CodeCache::find(const void* address) {
-    for (int i = 0; i < _count; i++) {
-        CodeBlob* cb = _blobs + i;
-        if (address >= cb->_start && address < cb->_end && cb->_method != NULL) {
-            return _blobs[i]._method;
-        }
-    }
-    return NULL;
-}
-
-
-NativeCodeCache::NativeCodeCache(const char* name, const void* min_address, const void* max_address) {
-    _name = strdup(name);
-    _min_address = min_address;
-    _max_address = max_address;
-}
-
-NativeCodeCache::~NativeCodeCache() {
-    for (int i = 0; i < _count; i++) {
-        free(_blobs[i]._method);
-    }
-    free(_name);
-}
-
-void NativeCodeCache::add(const void* start, int length, const char* name, bool update_bounds) {
-    char* name_copy = strdup(name);
-    // Replace non-printable characters
-    for (char* s = name_copy; *s != 0; s++) {
-        if (*s < ' ') *s = '?';
-    }
-    CodeCache::add(start, length, (jmethodID)name_copy, update_bounds);
-}
-
-void NativeCodeCache::sort() {
+void CodeCache::sort() {
    if (_count == 0) return;

    qsort(_blobs, _count, sizeof(CodeBlob), CodeBlob::comparator);
@@ -104,7 +106,25 @@ void NativeCodeCache::sort() {
    if (_max_address == NO_MAX_ADDRESS) _max_address = _blobs[_count - 1]._end;
 }

-const char* NativeCodeCache::binarySearch(const void* address) {
+void CodeCache::mark(NamePredicate predicate) {
+    for (int i = 0; i < _count; i++) {
+        const char* blob_name = _blobs[i]._name;
+        if (blob_name != NULL && predicate(blob_name)) {
+            NativeFunc::mark(blob_name);
+        }
+    }
+}
+
+CodeBlob* CodeCache::find(const void* address) {
+    for (int i = 0; i < _count; i++) {
+        if (address >= _blobs[i]._start && address < _blobs[i]._end) {
+            return &_blobs[i];
+        }
+    }
+    return NULL;
+}
+
+const char* CodeCache::binarySearch(const void* address) {
    int low = 0;
    int high = _count - 1;

@@ -115,21 +135,21 @@ const char* NativeCodeCache::binarySearch(const void* address) {
        } else if (_blobs[mid]._start > address) {
            high = mid - 1;
        } else {
-            return (const char*)_blobs[mid]._method;
+            return _blobs[mid]._name;
        }
    }

    // Symbols with zero size can be valid functions: e.g. ASM entry points or kernel code.
    // Also, in some cases (endless loop) the return address may point beyond the function.
    if (low > 0 && (_blobs[low - 1]._start == _blobs[low - 1]._end || _blobs[low - 1]._end == address)) {
-        return (const char*)_blobs[low - 1]._method;
+        return _blobs[low - 1]._name;
    }
    return _name;
 }

-const void* NativeCodeCache::findSymbol(const char* name) {
+const void* CodeCache::findSymbol(const char* name) {
    for (int i = 0; i < _count; i++) {
-        const char* blob_name = (const char*)_blobs[i]._method;
+        const char* blob_name = _blobs[i]._name;
        if (blob_name != NULL && strcmp(blob_name, name) == 0) {
            return _blobs[i]._start;
        }
@@ -137,16 +157,54 @@ const void* NativeCodeCache::findSymbol(const char* name) {
    return NULL;
 }

-const void* NativeCodeCache::findSymbolByPrefix(const char* prefix) {
+const void* CodeCache::findSymbolByPrefix(const char* prefix) {
    return findSymbolByPrefix(prefix, strlen(prefix));
 }

-const void* NativeCodeCache::findSymbolByPrefix(const char* prefix, int prefix_len) {
+const void* CodeCache::findSymbolByPrefix(const char* prefix, int prefix_len) {
    for (int i = 0; i < _count; i++) {
-        const char* blob_name = (const char*)_blobs[i]._method;
+        const char* blob_name = _blobs[i]._name;
        if (blob_name != NULL && strncmp(blob_name, prefix, prefix_len) == 0) {
            return _blobs[i]._start;
        }
    }
    return NULL;
 }
+
+void CodeCache::setGlobalOffsetTable(void** table, unsigned int count) {
+    _got_start = table;
+    _got_end = table + count;
+}
+
+void** CodeCache::findGlobalOffsetEntry(void* address) {
+    for (void** entry = _got_start; entry < _got_end; entry++) {
+        if (*entry == address) {
+            return entry;
+        }
+    }
+    return NULL;
+}
+
+void CodeCache::setDwarfTable(FrameDesc* table, int length) {
+    _dwarf_table = table;
+    _dwarf_table_length = length;
+}
+
+FrameDesc* CodeCache::findFrameDesc(const void* pc) {
+    u32 target_loc = (const char*)pc - _text_base;
+    int low = 0;
+    int high = _dwarf_table_length - 1;
+
+    while (low <= high) {
+        int mid = (unsigned int)(low + high) >> 1;
+        if (_dwarf_table[mid].loc < target_loc) {
+            low = mid + 1;
+        } else if (_dwarf_table[mid].loc > target_loc) {
+            high = mid - 1;
+        } else {
+            return &_dwarf_table[mid];
+        }
+    }
+
+    return low > 0 ? &_dwarf_table[low - 1] : NULL;
+}
--- a/src/codeCache.h
+++ b/src/codeCache.h
@@ -23,14 +23,46 @@
 #define NO_MIN_ADDRESS  ((const void*)-1)
 #define NO_MAX_ADDRESS  ((const void*)0)

+typedef bool (*NamePredicate)(const char* name);
+
 const int INITIAL_CODE_CACHE_CAPACITY = 1000;
+const int MAX_NATIVE_LIBS = 2048;
+
+
+class NativeFunc {
+  private:
+    short _lib_index;
+    char _mark;
+    char _reserved;
+    char _name[0];
+
+    static NativeFunc* from(const char* name) {
+        return (NativeFunc*)(name - sizeof(NativeFunc));
+    }
+
+  public:
+    static char* create(const char* name, short lib_index);
+    static void destroy(char* name);
+
+    static short libIndex(const char* name) {
+        return from(name)->_lib_index;
+    }
+
+    static bool isMarked(const char* name) {
+        return from(name)->_mark != 0;
+    }
+
+    static void mark(const char* name) {
+        from(name)->_mark = 1;
+    }
+};


 class CodeBlob {
  public:
    const void* _start;
    const void* _end;
-    jmethodID _method;
+    char* _name;

    static int comparator(const void* c1, const void* c2) {
        CodeBlob* cb1 = (CodeBlob*)c1;
@@ -48,60 +80,105 @@ class CodeBlob {
 };


+class FrameDesc;
+
 class CodeCache {
  protected:
+    char* _name;
+    short _lib_index;
+    const void* _min_address;
+    const void* _max_address;
+    const char* _text_base;
+
+    void** _got_start;
+    void** _got_end;
+
+    FrameDesc* _dwarf_table;
+    int _dwarf_table_length;
+
    int _capacity;
    int _count;
    CodeBlob* _blobs;
-    const void* _min_address;
-    const void* _max_address;

    void expand();

  public:
-    CodeCache() {
-        _capacity = INITIAL_CODE_CACHE_CAPACITY;
-        _count = 0;
-        _blobs = new CodeBlob[_capacity];
-        _min_address = NO_MIN_ADDRESS;
-        _max_address = NO_MAX_ADDRESS;
-    }
+    CodeCache(const char* name,
+              short lib_index = -1,
+              const void* min_address = NO_MIN_ADDRESS,
+              const void* max_address = NO_MAX_ADDRESS);

-    ~CodeCache() {
-        delete[] _blobs;
-    }
+    ~CodeCache();

-    bool contains(const void* address) {
-        return address >= _min_address && address < _max_address;
-    }
-
-    void add(const void* start, int length, jmethodID method, bool update_bounds = false);
-    void remove(const void* start, jmethodID method);
-    jmethodID find(const void* address);
-};
-
-
-class NativeCodeCache : public CodeCache {
-  private:
-    char* _name;
-
-  public:
-    NativeCodeCache(const char* name,
-                    const void* min_address = NO_MIN_ADDRESS,
-                    const void* max_address = NO_MAX_ADDRESS);
-
-    ~NativeCodeCache();
-
-    const char* name() {
+    const char* name() const {
        return _name;
    }

+    const void* minAddress() const {
+        return _min_address;
+    }
+
+    const void* maxAddress() const {
+        return _max_address;
+    }
+
+    bool contains(const void* address) const {
+        return address >= _min_address && address < _max_address;
+    }
+
+    void setTextBase(const char* text_base) {
+        _text_base = text_base;
+    }
+
+    void** gotStart() const {
+        return _got_start;
+    }
+
+    void** gotEnd() const {
+        return _got_end;
+    }
+
    void add(const void* start, int length, const char* name, bool update_bounds = false);
+    void updateBounds(const void* start, const void* end);
    void sort();
+    void mark(NamePredicate predicate);
+
+    CodeBlob* find(const void* address);
    const char* binarySearch(const void* address);
    const void* findSymbol(const char* name);
    const void* findSymbolByPrefix(const char* prefix);
    const void* findSymbolByPrefix(const char* prefix, int prefix_len);
+
+    void setGlobalOffsetTable(void** table, unsigned int count);
+    void** findGlobalOffsetEntry(void* address);
+
+    void setDwarfTable(FrameDesc* table, int length);
+    FrameDesc* findFrameDesc(const void* pc);
+};
+
+
+class CodeCacheArray {
+  private:
+    CodeCache* _libs[MAX_NATIVE_LIBS];
+    int _count;
+
+  public:
+    CodeCacheArray() : _count(0) {
+    }
+
+    CodeCache* operator[](int index) {
+        return _libs[index];
+    }
+
+    int count() {
+        return __atomic_load_n(&_count, __ATOMIC_ACQUIRE);
+    }
+
+    void add(CodeCache* lib) {
+        int index = __atomic_load_n(&_count, __ATOMIC_ACQUIRE);
+        _libs[index] = lib;
+        __atomic_store_n(&_count, index + 1, __ATOMIC_RELEASE);
+    }
 };

 #endif // _CODECACHE_H
--- a/src/converter/FlameGraph.java
+++ b/src/converter/FlameGraph.java
@@ -27,6 +27,14 @@ import java.util.Map;
 import java.util.TreeMap;

 public class FlameGraph {
+    public static final byte FRAME_INTERPRETED = 0;
+    public static final byte FRAME_JIT_COMPILED = 1;
+    public static final byte FRAME_INLINED = 2;
+    public static final byte FRAME_NATIVE = 3;
+    public static final byte FRAME_CPP = 4;
+    public static final byte FRAME_KERNEL = 5;
+    public static final byte FRAME_C1_COMPILED = 6;
+
    public String title = "Flame Graph";
    public boolean reverse;
    public double minwidth;
@@ -34,7 +42,7 @@ public class FlameGraph {
    public String input;
    public String output;

-    private final Frame root = new Frame();
+    private final Frame root = new Frame(FRAME_NATIVE);
    private int depth;
    private long mintotal;

@@ -80,17 +88,14 @@ public class FlameGraph {
        Frame frame = root;
        if (reverse) {
            for (int i = trace.length; --i >= skip; ) {
-                frame.total += ticks;
-                frame = frame.child(trace[i]);
+                frame = frame.addChild(trace[i], ticks);
            }
        } else {
            for (int i = skip; i < trace.length; i++) {
-                frame.total += ticks;
-                frame = frame.child(trace[i]);
+                frame = frame.addChild(trace[i], ticks);
            }
        }
-        frame.total += ticks;
-        frame.self += ticks;
+        frame.addLeaf(ticks);

        depth = Math.max(depth, trace.length);
    }
@@ -107,13 +112,15 @@ public class FlameGraph {
    }

    public void dump(PrintStream out) {
+        mintotal = (long) (root.total * minwidth / 100);
+        int depth = mintotal > 1 ? root.depth(mintotal) : this.depth + 1;
+
        out.print(applyReplacements(HEADER,
                "{title}", title,
-                "{height}", (depth + 1) * 16,
-                "{depth}", depth + 1,
+                "{height}", Math.min(depth * 16, 32767),
+                "{depth}", depth,
                "{reverse}", reverse));

-        mintotal = (long) (root.total * minwidth / 100);
        printFrame(out, "all", root, 0, 0);

        out.print(FOOTER);
@@ -141,13 +148,23 @@ public class FlameGraph {
    }

    private void printFrame(PrintStream out, String title, Frame frame, int level, long x) {
-        int type = frameType(title);
-        title = stripSuffix(title);
+        int type = frame.getType();
+        if (type == FRAME_KERNEL) {
+            title = stripSuffix(title);
+        }
+        if (title.indexOf('\\') >= 0) {
+            title = title.replace("\\", "\\\\");
+        }
        if (title.indexOf('\'') >= 0) {
            title = title.replace("'", "\\'");
        }

-        out.println("f(" + level + "," + x + "," + frame.total + "," + type + ",'" + title + "')");
+        if ((frame.inlined | frame.c1 | frame.interpreted) != 0 && frame.inlined < frame.total && frame.interpreted < frame.total) {
+            out.println("f(" + level + "," + x + "," + frame.total + "," + type + ",'" + title + "'," +
+                    frame.inlined + "," + frame.c1 + "," + frame.interpreted + ")");
+        } else {
+            out.println("f(" + level + "," + x + "," + frame.total + "," + type + ",'" + title + "')");
+        }

        x += frame.self;
        for (Map.Entry<String, Frame> e : frame.entrySet()) {
@@ -159,28 +176,8 @@ public class FlameGraph {
        }
    }

-    private String stripSuffix(String title) {
-        int len = title.length();
-        if (len >= 4 && title.charAt(len - 1) == ']' && title.regionMatches(len - 4, "_[", 0, 2)) {
-            return title.substring(0, len - 4);
-        }
-        return title;
-    }
-
-    private int frameType(String title) {
-        if (title.endsWith("_[j]")) {
-            return 0;
-        } else if (title.endsWith("_[i]")) {
-            return 1;
-        } else if (title.endsWith("_[k]")) {
-            return 2;
-        } else if (title.contains("::") || title.startsWith("-[") || title.startsWith("+[")) {
-            return 3;
-        } else if (title.indexOf('/') > 0 || title.indexOf('.') > 0 && Character.isUpperCase(title.charAt(0))) {
-            return 0;
-        } else {
-            return 4;
-        }
+    static String stripSuffix(String title) {
+        return title.substring(0, title.length() - 4);
    }

    public static void main(String[] args) throws IOException {
@@ -201,16 +198,74 @@ public class FlameGraph {
    }

    static class Frame extends TreeMap<String, Frame> {
+        final byte type;
        long total;
        long self;
+        long inlined, c1, interpreted;

-        Frame child(String title) {
-            Frame child = get(title);
+        Frame(byte type) {
+            this.type = type;
+        }
+
+        byte getType() {
+            if (inlined * 3 >= total) {
+                return FRAME_INLINED;
+            } else if (c1 * 2 >= total) {
+                return FRAME_C1_COMPILED;
+            } else if (interpreted * 2 >= total) {
+                return FRAME_INTERPRETED;
+            } else {
+                return type;
+            }
+        }
+
+        private Frame getChild(String title, byte type) {
+            Frame child = super.get(title);
            if (child == null) {
-                put(title, child = new Frame());
+                super.put(title, child = new Frame(type));
            }
            return child;
        }
+
+        Frame addChild(String title, long ticks) {
+            total += ticks;
+
+            Frame child;
+            if (title.endsWith("_[j]")) {
+                child = getChild(stripSuffix(title), FRAME_JIT_COMPILED);
+            } else if (title.endsWith("_[i]")) {
+                (child = getChild(stripSuffix(title), FRAME_JIT_COMPILED)).inlined += ticks;
+            } else if (title.endsWith("_[k]")) {
+                child = getChild(title, FRAME_KERNEL);
+            } else if (title.endsWith("_[1]")) {
+                (child = getChild(stripSuffix(title), FRAME_JIT_COMPILED)).c1 += ticks;
+            } else if (title.contains("::") || title.startsWith("-[") || title.startsWith("+[")) {
+                child = getChild(title, FRAME_CPP);
+            } else if (title.indexOf('/') > 0 && title.charAt(0) != '['
+                    || title.indexOf('.') > 0 && Character.isUpperCase(title.charAt(0))) {
+                (child = getChild(title, FRAME_JIT_COMPILED)).interpreted += ticks;
+            } else {
+                child = getChild(title, FRAME_NATIVE);
+            }
+            return child;
+        }
+
+        void addLeaf(long ticks) {
+            total += ticks;
+            self += ticks;
+        }
+
+        int depth(long cutoff) {
+            int depth = 0;
+            if (size() > 0) {
+                for (Frame child : values()) {
+                    if (child.total >= cutoff) {
+                        depth = Math.max(depth, child.depth(cutoff));
+                    }
+                }
+            }
+            return depth + 1;
+        }
    }

    private static final String HEADER = "<!DOCTYPE html>\n" +
@@ -264,11 +319,13 @@ public class FlameGraph {
            "\tc.font = document.body.style.font;\n" +
            "\n" +
            "\tconst palette = [\n" +
+            "\t\t[0xb2e1b2, 20, 20, 20],\n" +
            "\t\t[0x50e150, 30, 30, 30],\n" +
-            "\t\t[0x50bebe, 30, 30, 30],\n" +
-            "\t\t[0xe17d00, 30, 30,  0],\n" +
-            "\t\t[0xc8c83c, 30, 30, 10],\n" +
+            "\t\t[0x50cccc, 30, 30, 30],\n" +
            "\t\t[0xe15a5a, 30, 40, 40],\n" +
+            "\t\t[0xc8c83c, 30, 30, 10],\n" +
+            "\t\t[0xe17d00, 30, 30,  0],\n" +
+            "\t\t[0xcce880, 20, 20, 20],\n" +
            "\t];\n" +
            "\n" +
            "\tfunction getColor(p) {\n" +
@@ -276,8 +333,10 @@ public class FlameGraph {
            "\t\treturn '#' + (p[0] + ((p[1] * v) << 16 | (p[2] * v) << 8 | (p[3] * v))).toString(16);\n" +
            "\t}\n" +
            "\n" +
-            "\tfunction f(level, left, width, type, title) {\n" +
-            "\t\tlevels[level].push({left: left, width: width, color: getColor(palette[type]), title: title});\n" +
+            "\tfunction f(level, left, width, type, title, inln, c1, int) {\n" +
+            "\t\tlevels[level].push({left: left, width: width, color: getColor(palette[type]), title: title,\n" +
+            "\t\t\tdetails: (int ? ', int=' + int : '') + (c1 ? ', c1=' + c1 : '') + (inln ? ', inln=' + inln : '')\n" +
+            "\t\t});\n" +
            "\t}\n" +
            "\n" +
            "\tfunction samples(n) {\n" +
@@ -343,12 +402,12 @@ public class FlameGraph {
            "\t\tfunction totalMarked() {\n" +
            "\t\t\tlet total = 0;\n" +
            "\t\t\tlet left = 0;\n" +
-            "\t\t\tfor (let x in marked) {\n" +
+            "\t\t\tObject.keys(marked).sort(function(a, b) { return a - b; }).forEach(function(x) {\n" +
            "\t\t\t\tif (+x >= left) {\n" +
            "\t\t\t\t\ttotal += marked[x];\n" +
            "\t\t\t\t\tleft = +x + marked[x];\n" +
            "\t\t\t\t}\n" +
-            "\t\t\t}\n" +
+            "\t\t\t});\n" +
            "\t\t\treturn total;\n" +
            "\t\t}\n" +
            "\n" +
@@ -392,7 +451,7 @@ public class FlameGraph {
            "\t\t\t\thl.style.top = ((reverse ? h * 16 : canvasHeight - (h + 1) * 16) + canvas.offsetTop) + 'px';\n" +
            "\t\t\t\thl.firstChild.textContent = f.title;\n" +
            "\t\t\t\thl.style.display = 'block';\n" +
-            "\t\t\t\tcanvas.title = f.title + '\\n(' + samples(f.width) + ', ' + pct(f.width, levels[0][0].width) + '%)';\n" +
+            "\t\t\t\tcanvas.title = f.title + '\\n(' + samples(f.width) + f.details + ', ' + pct(f.width, levels[0][0].width) + '%)';\n" +
            "\t\t\t\tcanvas.style.cursor = 'pointer';\n" +
            "\t\t\t\tcanvas.onclick = function() {\n" +
            "\t\t\t\t\tif (f != root) {\n" +
--- a/src/converter/jfr2flame.java
+++ b/src/converter/jfr2flame.java
@@ -19,15 +19,24 @@ import one.jfr.Dictionary;
 import one.jfr.JfrReader;
 import one.jfr.MethodRef;
 import one.jfr.StackTrace;
+import one.jfr.event.AllocationSample;
+import one.jfr.event.ContendedLock;
+import one.jfr.event.Event;
+import one.jfr.event.EventAggregator;
+import one.jfr.event.ExecutionSample;

+import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Map;

 /**
 * Converts .jfr output produced by async-profiler to HTML Flame Graph.
 */
 public class jfr2flame {

-    private static final int FRAME_KERNEL = 5;
+    private static final String[] FRAME_SUFFIX = {"", "_[j]", "_[i]", "", "", "_[k]", "_[1]"};

    private final JfrReader jfr;
    private final Dictionary<String> methodNames = new Dictionary<>();
@@ -36,55 +45,187 @@ public class jfr2flame {
        this.jfr = jfr;
    }

-    public void convert(final FlameGraph fg) {
+    public void convert(final FlameGraph fg, final boolean threads, final boolean total,
+                        final boolean lines, final boolean bci, final int threadState,
+                        final Class<? extends Event> eventClass) throws IOException {
+        EventAggregator agg = new EventAggregator(threads, total);
+        for (Event event; (event = jfr.readEvent(eventClass)) != null; ) {
+            if (threadState < 0 || ((ExecutionSample) event).threadState == threadState) {
+                agg.collect(event);
+            }
+        }
+
+        final double ticksToNanos = 1e9 / jfr.ticksPerSec;
+        final boolean scale = total && eventClass == ContendedLock.class && ticksToNanos != 1.0;
+
        // Don't use lambda for faster startup
-        jfr.stackTraces.forEach(new Dictionary.Visitor<StackTrace>() {
+        agg.forEach(new EventAggregator.Visitor() {
            @Override
-            public void visit(long id, StackTrace stackTrace) {
-                long[] methods = stackTrace.methods;
-                byte[] types = stackTrace.types;
-                String[] trace = new String[methods.length];
-                for (int i = 0; i < methods.length; i++) {
-                    trace[trace.length - 1 - i] = getMethodName(methods[i], types[i]);
+            public void visit(Event event, long value) {
+                StackTrace stackTrace = jfr.stackTraces.get(event.stackTraceId);
+                if (stackTrace != null) {
+                    long[] methods = stackTrace.methods;
+                    byte[] types = stackTrace.types;
+                    int[] locations = stackTrace.locations;
+                    String classFrame = getClassFrame(event);
+                    String[] trace = new String[methods.length + (threads ? 1 : 0) + (classFrame != null ? 1 : 0)];
+                    if (threads) {
+                        trace[0] = getThreadFrame(event.tid);
+                    }
+                    int idx = trace.length;
+                    if (classFrame != null) {
+                        trace[--idx] = classFrame;
+                    }
+                    for (int i = 0; i < methods.length; i++) {
+                        String methodName = getMethodName(methods[i], types[i]);
+                        int location;
+                        if (lines && (location = locations[i] >>> 16) != 0) {
+                            methodName += ":" + location;
+                        } else if (bci && (location = locations[i] & 0xffff) != 0) {
+                            methodName += "@" + location;
+                        }
+                        trace[--idx] = methodName + FRAME_SUFFIX[types[i]];
+                    }
+                    fg.addSample(trace, scale ? (long) (value * ticksToNanos) : value);
                }
-                fg.addSample(trace, stackTrace.samples);
            }
        });
    }

-    private String getMethodName(long methodId, int type) {
+    private String getThreadFrame(int tid) {
+        String threadName = jfr.threads.get(tid);
+        return threadName == null ? "[tid=" + tid + ']' : '[' + threadName + " tid=" + tid + ']';
+    }
+
+    private String getClassFrame(Event event) {
+        long classId;
+        String suffix;
+        if (event instanceof AllocationSample) {
+            classId = ((AllocationSample) event).classId;
+            suffix = ((AllocationSample) event).tlabSize == 0 ? "_[k]" : "_[i]";
+        } else if (event instanceof ContendedLock) {
+            classId = ((ContendedLock) event).classId;
+            suffix = "_[i]";
+        } else {
+            return null;
+        }
+
+        ClassRef cls = jfr.classes.get(classId);
+        if (cls == null) {
+            return "null";
+        }
+        byte[] className = jfr.symbols.get(cls.name);
+
+        int arrayDepth = 0;
+        while (className[arrayDepth] == '[') {
+            arrayDepth++;
+        }
+
+        StringBuilder sb = new StringBuilder(toJavaClassName(className, arrayDepth));
+        while (arrayDepth-- > 0) {
+            sb.append("[]");
+        }
+        return sb.append(suffix).toString();
+    }
+
+    private String toJavaClassName(byte[] symbol, int start) {
+        switch (symbol[start]) {
+            case 'B':
+                return "byte";
+            case 'C':
+                return "char";
+            case 'S':
+                return "short";
+            case 'I':
+                return "int";
+            case 'J':
+                return "long";
+            case 'Z':
+                return "boolean";
+            case 'F':
+                return "float";
+            case 'D':
+                return "double";
+            case 'L':
+                return new String(symbol, start + 1, symbol.length - start - 2, StandardCharsets.UTF_8).replace('/', '.');
+            default:
+                return new String(symbol, start, symbol.length - start, StandardCharsets.UTF_8).replace('/', '.');
+        }
+    }
+
+    private String getMethodName(long methodId, byte methodType) {
        String result = methodNames.get(methodId);
        if (result != null) {
            return result;
        }

        MethodRef method = jfr.methods.get(methodId);
-        ClassRef cls = jfr.classes.get(method.cls);
-        byte[] className = jfr.symbols.get(cls.name);
-        byte[] methodName = jfr.symbols.get(method.name);
-
-        if (className == null || className.length == 0) {
-            String methodStr = new String(methodName, StandardCharsets.UTF_8);
-            result = type == FRAME_KERNEL ? methodStr + "_[k]" : methodStr;
+        if (method == null) {
+            result = "unknown";
        } else {
-            String classStr = new String(className, StandardCharsets.UTF_8);
-            String methodStr = new String(methodName, StandardCharsets.UTF_8);
-            result = classStr + '.' + methodStr + "_[j]";
+            ClassRef cls = jfr.classes.get(method.cls);
+            byte[] className = jfr.symbols.get(cls.name);
+            byte[] methodName = jfr.symbols.get(method.name);
+
+            if ((methodType >= FlameGraph.FRAME_NATIVE && methodType <= FlameGraph.FRAME_KERNEL)
+                    || className == null || className.length == 0) {
+                result = new String(methodName, StandardCharsets.UTF_8);
+            } else {
+                String classStr = new String(className, StandardCharsets.UTF_8);
+                String methodStr = new String(methodName, StandardCharsets.UTF_8);
+                result = classStr + '.' + methodStr;
+            }
        }

        methodNames.put(methodId, result);
        return result;
    }

+    private static int getMapKey(Map<Integer, String> map, String value) {
+        for (Map.Entry<Integer, String> entry : map.entrySet()) {
+            if (value.equals(entry.getValue())) {
+                return entry.getKey();
+            }
+        }
+        return -1;
+    }
+
    public static void main(String[] args) throws Exception {
        FlameGraph fg = new FlameGraph(args);
        if (fg.input == null) {
            System.out.println("Usage: java " + jfr2flame.class.getName() + " [options] input.jfr [output.html]");
+            System.out.println();
+            System.out.println("options include all supported FlameGraph options, plus the following:");
+            System.out.println("  --cpu      CPU Flame Graph");
+            System.out.println("  --alloc    Allocation Flame Graph");
+            System.out.println("  --lock     Lock contention Flame Graph");
+            System.out.println("  --threads  Split profile by threads");
+            System.out.println("  --total    Accumulate the total value (time, bytes, etc.)");
+            System.out.println("  --lines    Show line numbers");
+            System.out.println("  --bci      Show bytecode indices");
            System.exit(1);
        }

+        HashSet<String> options = new HashSet<>(Arrays.asList(args));
+        boolean threads = options.contains("--threads");
+        boolean total = options.contains("--total");
+        boolean lines = options.contains("--lines");
+        boolean bci = options.contains("--bci");
+
+        Class<? extends Event> eventClass;
+        boolean cpu = false;
+        if (options.contains("--alloc")) {
+            eventClass = AllocationSample.class;
+        } else if (options.contains("--lock")) {
+            eventClass = ContendedLock.class;
+        } else {
+            eventClass = ExecutionSample.class;
+            cpu = options.contains("--cpu");
+        }
+
        try (JfrReader jfr = new JfrReader(fg.input)) {
-            new jfr2flame(jfr).convert(fg);
+            int threadState = cpu ? getMapKey(jfr.threadStates, "STATE_RUNNABLE") : -1;
+            new jfr2flame(jfr).convert(fg, threads, total, lines, bci, threadState, eventClass);
        }

        fg.dump();
--- a/src/converter/jfr2nflx.java
+++ b/src/converter/jfr2nflx.java
@@ -15,11 +15,12 @@
 */

 import one.jfr.ClassRef;
-import one.jfr.Dictionary;
 import one.jfr.JfrReader;
 import one.jfr.MethodRef;
-import one.jfr.Sample;
 import one.jfr.StackTrace;
+import one.jfr.event.Event;
+import one.jfr.event.EventAggregator;
+import one.jfr.event.ExecutionSample;
 import one.proto.Proto;

 import java.io.File;
@@ -27,6 +28,7 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.Arrays;
+import java.util.List;

 /**
 * Converts .jfr output produced by async-profiler to nflxprofile format
@@ -35,24 +37,27 @@ import java.util.Arrays;
 */
 public class jfr2nflx {

-    private static final String[] FRAME_TYPE = {"jit", "jit", "inlined", "user", "user", "kernel"};
+    private static final String[] FRAME_TYPE = {"jit", "jit", "inlined", "user", "user", "kernel", "jit"};
    private static final byte[] NO_STACK = "[no_stack]".getBytes();
+    private static final byte[] UNKNOWN = "[unknown]".getBytes();

    private final JfrReader jfr;
+    private final List<ExecutionSample> samples;

-    public jfr2nflx(JfrReader jfr) {
+    public jfr2nflx(JfrReader jfr) throws IOException {
        this.jfr = jfr;
+        this.samples = jfr.readAllEvents(ExecutionSample.class);
    }

    public void dump(OutputStream out) throws IOException {
        long startTime = System.nanoTime();

-        int samples = jfr.samples.size();
-        long durationTicks = samples == 0 ? 0 : jfr.samples.get(samples - 1).time - jfr.startTicks + 1;
+        int size = samples.size();
+        long durationTicks = size == 0 ? 0 : samples.get(size - 1).time - jfr.startTicks + 1;

        final Proto profile = new Proto(200000)
                .field(1, 0.0)
-                .field(2, Math.max(jfr.durationNanos / 1e9, durationTicks / (double) jfr.ticksPerSec))
+                .field(2, Math.max(jfr.durationNanos() / 1e9, durationTicks / (double) jfr.ticksPerSec))
                .field(3, packSamples())
                .field(4, packDeltas())
                .field(6, "async-profiler")
@@ -63,15 +68,23 @@ public class jfr2nflx {
        final Proto nodes = new Proto(10000);
        final Proto node = new Proto(10000);

+        EventAggregator agg = new EventAggregator(false, false);
+        for (ExecutionSample sample : samples) {
+            agg.collect(sample);
+        }
+
        // Don't use lambda for faster startup
-        jfr.stackTraces.forEach(new Dictionary.Visitor<StackTrace>() {
+        agg.forEach(new EventAggregator.Visitor() {
            @Override
-            public void visit(long id, StackTrace stackTrace) {
-                profile.field(5, nodes
-                        .field(1, (int) id)
-                        .field(2, packNode(node, stackTrace)));
-                nodes.reset();
-                node.reset();
+            public void visit(Event event, long value) {
+                StackTrace stackTrace = jfr.stackTraces.get(event.stackTraceId);
+                if (stackTrace != null) {
+                    profile.field(5, nodes
+                            .field(1, event.stackTraceId)
+                            .field(2, packNode(node, stackTrace)));
+                    nodes.reset();
+                    node.reset();
+                }
            }
        });

@@ -86,13 +99,13 @@ public class jfr2nflx {
        byte[] types = stackTrace.types;
        int top = methods.length - 1;

-        node.field(1, top >= 0 ? getMethodName(methods[top]) : NO_STACK);
+        node.field(1, top >= 0 ? getMethodName(methods[top], types[top]) : NO_STACK);
        node.field(2, 1);
        node.field(4, top >= 0 ? FRAME_TYPE[types[top]] : "user");

        for (Proto frame = new Proto(100); --top >= 0; frame.reset()) {
            node.field(10, frame
-                    .field(1, getMethodName(methods[top]))
+                    .field(1, getMethodName(methods[top], types[top]))
                    .field(2, FRAME_TYPE[types[top]]));
        }

@@ -101,7 +114,7 @@ public class jfr2nflx {

    private Proto packSamples() {
        Proto proto = new Proto(10000);
-        for (Sample sample : jfr.samples) {
+        for (ExecutionSample sample : samples) {
            proto.writeInt(sample.stackTraceId);
        }
        return proto;
@@ -111,7 +124,7 @@ public class jfr2nflx {
        Proto proto = new Proto(10000);
        double ticksPerSec = jfr.ticksPerSec;
        long prevTime = jfr.startTicks;
-        for (Sample sample : jfr.samples) {
+        for (ExecutionSample sample : samples) {
            proto.writeDouble((sample.time - prevTime) / ticksPerSec);
            prevTime = sample.time;
        }
@@ -120,19 +133,24 @@ public class jfr2nflx {

    private Proto packTids() {
        Proto proto = new Proto(10000);
-        for (Sample sample : jfr.samples) {
+        for (ExecutionSample sample : samples) {
            proto.writeInt(sample.tid);
        }
        return proto;
    }

-    private byte[] getMethodName(long methodId) {
+    private byte[] getMethodName(long methodId, byte methodType) {
        MethodRef method = jfr.methods.get(methodId);
+        if (method == null) {
+            return UNKNOWN;
+        }
+
        ClassRef cls = jfr.classes.get(method.cls);
        byte[] className = jfr.symbols.get(cls.name);
        byte[] methodName = jfr.symbols.get(method.name);

-        if (className == null || className.length == 0) {
+        if ((methodType >= FlameGraph.FRAME_NATIVE && methodType <= FlameGraph.FRAME_KERNEL)
+                || className == null || className.length == 0) {
            return methodName;
        } else {
            byte[] fullName = Arrays.copyOf(className, className.length + 1 + methodName.length);
--- a/src/converter/one/jfr/Dictionary.java
+++ b/src/converter/one/jfr/Dictionary.java
@@ -31,22 +31,32 @@ public class Dictionary<T> {
        this.values = new Object[INITIAL_CAPACITY];
    }

+    public void clear() {
+        keys = new long[INITIAL_CAPACITY];
+        values = new Object[INITIAL_CAPACITY];
+        size = 0;
+    }
+
    public void put(long key, T value) {
        if (key == 0) {
            throw new IllegalArgumentException("Zero key not allowed");
        }

-        if (++size * 2 > keys.length) {
-            resize(keys.length * 2);
-        }
-
        int mask = keys.length - 1;
        int i = hashCode(key) & mask;
-        while (keys[i] != 0 && keys[i] != key) {
+        while (keys[i] != 0) {
+            if (keys[i] == key) {
+                values[i] = value;
+                return;
+            }
            i = (i + 1) & mask;
        }
        keys[i] = key;
        values[i] = value;
+
+        if (++size * 2 > keys.length) {
+            resize(keys.length * 2);
+        }
    }

    @SuppressWarnings("unchecked")
@@ -69,9 +79,8 @@ public class Dictionary<T> {
    }

    public int preallocate(int count) {
-        int newSize = size + count;
-        if (newSize * 2 > keys.length) {
-            resize(Integer.highestOneBit(newSize * 4 - 1));
+        if (count * 2 > keys.length) {
+            resize(Integer.highestOneBit(count * 4 - 1));
        }
        return count;
    }
@@ -98,6 +107,7 @@ public class Dictionary<T> {
    }

    private static int hashCode(long key) {
+        key *= 0xc6a4a7935bd1e995L;
        return (int) (key ^ (key >>> 32));
    }

--- a/src/converter/one/jfr/JfrReader.java
+++ b/src/converter/one/jfr/JfrReader.java
@@ -16,6 +16,11 @@

 package one.jfr;

+import one.jfr.event.AllocationSample;
+import one.jfr.event.ContendedLock;
+import one.jfr.event.Event;
+import one.jfr.event.ExecutionSample;
+
 import java.io.Closeable;
 import java.io.IOException;
 import java.nio.ByteBuffer;
@@ -33,17 +38,19 @@ import java.util.Map;
 * Parses JFR output produced by async-profiler.
 */
 public class JfrReader implements Closeable {
+    private static final int BUFFER_SIZE = 2 * 1024 * 1024;
    private static final int CHUNK_HEADER_SIZE = 68;
-    private static final int CPOOL_OFFSET = 16;
-    private static final int META_OFFSET = 24;
+    private static final int CHUNK_SIGNATURE = 0x464c5200;

    private final FileChannel ch;
-    private final ByteBuffer buf;
+    private ByteBuffer buf;
+    private long filePosition;

-    public final long startNanos;
-    public final long durationNanos;
-    public final long startTicks;
-    public final long ticksPerSec;
+    public boolean incomplete;
+    public long startNanos = Long.MAX_VALUE;
+    public long endNanos = Long.MIN_VALUE;
+    public long startTicks = Long.MAX_VALUE;
+    public long ticksPerSec;

    public final Dictionary<JfrClass> types = new Dictionary<>();
    public final Map<String, JfrClass> typesByName = new HashMap<>();
@@ -54,29 +61,27 @@ public class JfrReader implements Closeable {
    public final Dictionary<StackTrace> stackTraces = new Dictionary<>();
    public final Map<Integer, String> frameTypes = new HashMap<>();
    public final Map<Integer, String> threadStates = new HashMap<>();
-    public final List<Sample> samples = new ArrayList<>();
+    public final Map<String, String> settings = new HashMap<>();
+
+    private int executionSample;
+    private int nativeMethodSample;
+    private int allocationInNewTLAB;
+    private int allocationOutsideTLAB;
+    private int allocationSample;
+    private int monitorEnter;
+    private int threadPark;
+    private int activeSetting;
+    private boolean activeSettingHasStack;

    public JfrReader(String fileName) throws IOException {
        this.ch = FileChannel.open(Paths.get(fileName), StandardOpenOption.READ);
-        this.buf = ch.map(FileChannel.MapMode.READ_ONLY, 0, ch.size());
+        this.buf = ByteBuffer.allocateDirect(BUFFER_SIZE);

-        if (buf.getInt(0) != 0x464c5200) {
-            throw new IOException("Not a valid JFR file");
+        buf.flip();
+        ensureBytes(CHUNK_HEADER_SIZE);
+        if (!readChunk(0)) {
+            throw new IOException("Incomplete JFR file");
        }
-
-        int version = buf.getInt(4);
-        if (version < 0x20000 || version > 0x2ffff) {
-            throw new IOException("Unsupported JFR version: " + (version >>> 16) + "." + (version & 0xffff));
-        }
-
-        this.startNanos = buf.getLong(32);
-        this.durationNanos = buf.getLong(40);
-        this.startTicks = buf.getLong(48);
-        this.ticksPerSec = buf.getLong(56);
-
-        readMeta();
-        readConstantPool();
-        readEvents();
    }

    @Override
@@ -84,9 +89,144 @@ public class JfrReader implements Closeable {
        ch.close();
    }

-    private void readMeta() {
-        buf.position(buf.getInt(META_OFFSET + 4));
-        getVarint();
+    public long durationNanos() {
+        return endNanos - startNanos;
+    }
+
+    public List<Event> readAllEvents() throws IOException {
+        return readAllEvents(null);
+    }
+
+    public <E extends Event> List<E> readAllEvents(Class<E> cls) throws IOException {
+        ArrayList<E> events = new ArrayList<>();
+        for (E event; (event = readEvent(cls)) != null; ) {
+            events.add(event);
+        }
+        Collections.sort(events);
+        return events;
+    }
+
+    public Event readEvent() throws IOException {
+        return readEvent(null);
+    }
+
+    @SuppressWarnings("unchecked")
+    public <E extends Event> E readEvent(Class<E> cls) throws IOException {
+        while (ensureBytes(CHUNK_HEADER_SIZE)) {
+            int pos = buf.position();
+            int size = getVarint();
+            int type = getVarint();
+
+            if (type == 'L' && buf.getInt(pos) == CHUNK_SIGNATURE) {
+                if (readChunk(pos)) {
+                    continue;
+                }
+                break;
+            }
+
+            if (type == executionSample || type == nativeMethodSample) {
+                if (cls == null || cls == ExecutionSample.class) return (E) readExecutionSample();
+            } else if (type == allocationInNewTLAB) {
+                if (cls == null || cls == AllocationSample.class) return (E) readAllocationSample(true);
+            } else if (type == allocationOutsideTLAB || type == allocationSample) {
+                if (cls == null || cls == AllocationSample.class) return (E) readAllocationSample(false);
+            } else if (type == monitorEnter) {
+                if (cls == null || cls == ContendedLock.class) return (E) readContendedLock(false);
+            } else if (type == threadPark) {
+                if (cls == null || cls == ContendedLock.class) return (E) readContendedLock(true);
+            } else if (type == activeSetting) {
+                readActiveSetting();
+            }
+
+            if ((pos += size) <= buf.limit()) {
+                buf.position(pos);
+            } else {
+                seek(filePosition + pos);
+            }
+        }
+        return null;
+    }
+
+    private ExecutionSample readExecutionSample() {
+        long time = getVarlong();
+        int tid = getVarint();
+        int stackTraceId = getVarint();
+        int threadState = getVarint();
+        return new ExecutionSample(time, tid, stackTraceId, threadState);
+    }
+
+    private AllocationSample readAllocationSample(boolean tlab) {
+        long time = getVarlong();
+        int tid = getVarint();
+        int stackTraceId = getVarint();
+        int classId = getVarint();
+        long allocationSize = getVarlong();
+        long tlabSize = tlab ? getVarlong() : 0;
+        return new AllocationSample(time, tid, stackTraceId, classId, allocationSize, tlabSize);
+    }
+
+    private ContendedLock readContendedLock(boolean hasTimeout) {
+        long time = getVarlong();
+        long duration = getVarlong();
+        int tid = getVarint();
+        int stackTraceId = getVarint();
+        int classId = getVarint();
+        if (hasTimeout) getVarlong();
+        long until = getVarlong();
+        long address = getVarlong();
+        return new ContendedLock(time, tid, stackTraceId, duration, classId);
+    }
+
+    private void readActiveSetting() {
+        long time = getVarlong();
+        long duration = getVarlong();
+        int tid = getVarint();
+        if (activeSettingHasStack) getVarint();
+        long id = getVarlong();
+        String name = getString();
+        String value = getString();
+        settings.put(name, value);
+    }
+
+    private boolean readChunk(int pos) throws IOException {
+        if (pos + CHUNK_HEADER_SIZE > buf.limit() || buf.getInt(pos) != CHUNK_SIGNATURE) {
+            throw new IOException("Not a valid JFR file");
+        }
+
+        int version = buf.getInt(pos + 4);
+        if (version < 0x20000 || version > 0x2ffff) {
+            throw new IOException("Unsupported JFR version: " + (version >>> 16) + "." + (version & 0xffff));
+        }
+
+        long cpOffset = buf.getLong(pos + 16);
+        long metaOffset = buf.getLong(pos + 24);
+        if (cpOffset == 0 || metaOffset == 0) {
+            incomplete = true;
+            return false;
+        }
+
+        startNanos = Math.min(startNanos, buf.getLong(pos + 32));
+        endNanos = Math.max(endNanos, buf.getLong(pos + 32) + buf.getLong(pos + 40));
+        startTicks = Math.min(startTicks, buf.getLong(pos + 48));
+        ticksPerSec = buf.getLong(pos + 56);
+
+        types.clear();
+        typesByName.clear();
+
+        long chunkStart = filePosition + pos;
+        readMeta(chunkStart + metaOffset);
+        readConstantPool(chunkStart + cpOffset);
+        cacheEventTypes();
+
+        seek(chunkStart + CHUNK_HEADER_SIZE);
+        return true;
+    }
+
+    private void readMeta(long metaOffset) throws IOException {
+        seek(metaOffset);
+        ensureBytes(5);
+
+        ensureBytes(getVarint() - buf.position());
        getVarint();
        getVarlong();
        getVarlong();
@@ -133,15 +273,17 @@ public class JfrReader implements Closeable {
        }
    }

-    private void readConstantPool() {
-        int offset = buf.getInt(CPOOL_OFFSET + 4);
-        while (true) {
-            buf.position(offset);
-            getVarint();
+    private void readConstantPool(long cpOffset) throws IOException {
+        long delta;
+        do {
+            seek(cpOffset);
+            ensureBytes(5);
+
+            ensureBytes(getVarint() - buf.position());
            getVarint();
            getVarlong();
            getVarlong();
-            long delta = getVarlong();
+            delta = getVarlong();
            getVarint();

            int poolCount = getVarint();
@@ -149,12 +291,7 @@ public class JfrReader implements Closeable {
                int type = getVarint();
                readConstants(types.get(type));
            }
-
-            if (delta == 0) {
-                break;
-            }
-            offset += delta;
-        }
+        } while (delta != 0 && (cpOffset += delta) > 0);
    }

    private void readConstants(JfrClass type) {
@@ -241,13 +378,15 @@ public class JfrReader implements Closeable {
        int depth = getVarint();
        long[] methods = new long[depth];
        byte[] types = new byte[depth];
+        int[] locations = new int[depth];
        for (int i = 0; i < depth; i++) {
            methods[i] = getVarlong();
            int line = getVarint();
            int bci = getVarint();
+            locations[i] = line << 16 | (bci & 0xffff);
            types[i] = buf.get();
        }
-        return new StackTrace(methods, types);
+        return new StackTrace(methods, types, locations);
    }

    private void readSymbols() {
@@ -294,36 +433,16 @@ public class JfrReader implements Closeable {
        }
    }

-    private void readEvents() {
-        int executionSample = getTypeId("jdk.ExecutionSample");
-        int nativeMethodSample = getTypeId("jdk.NativeMethodSample");
-
-        buf.position(CHUNK_HEADER_SIZE);
-        while (buf.hasRemaining()) {
-            int position = buf.position();
-            int size = getVarint();
-            int type = getVarint();
-            if (type == executionSample || type == nativeMethodSample) {
-                readExecutionSample();
-            } else {
-                buf.position(position + size);
-            }
-        }
-
-        Collections.sort(samples);
-    }
-
-    private void readExecutionSample() {
-        long time = getVarlong();
-        int tid = getVarint();
-        int stackTraceId = getVarint();
-        int threadState = getVarint();
-        samples.add(new Sample(time, tid, stackTraceId, threadState));
-
-        StackTrace stackTrace = stackTraces.get(stackTraceId);
-        if (stackTrace != null) {
-            stackTrace.samples++;
-        }
+    private void cacheEventTypes() {
+        executionSample = getTypeId("jdk.ExecutionSample");
+        nativeMethodSample = getTypeId("jdk.NativeMethodSample");
+        allocationInNewTLAB = getTypeId("jdk.ObjectAllocationInNewTLAB");
+        allocationOutsideTLAB = getTypeId("jdk.ObjectAllocationOutsideTLAB");
+        allocationSample = getTypeId("jdk.ObjectAllocationSample");
+        monitorEnter = getTypeId("jdk.JavaMonitorEnter");
+        threadPark = getTypeId("jdk.ThreadPark");
+        activeSetting = getTypeId("jdk.ActiveSetting");
+        activeSettingHasStack = activeSetting >= 0 && typesByName.get("jdk.ActiveSetting").field("stackTrace") != null;
    }

    private int getTypeId(String typeName) {
@@ -381,4 +500,32 @@ public class JfrReader implements Closeable {
        buf.get(bytes);
        return bytes;
    }
+
+    private void seek(long pos) throws IOException {
+        filePosition = pos;
+        ch.position(pos);
+        buf.rewind().flip();
+    }
+
+    private boolean ensureBytes(int needed) throws IOException {
+        if (buf.remaining() >= needed) {
+            return true;
+        }
+
+        filePosition += buf.position();
+
+        if (buf.capacity() < needed) {
+            ByteBuffer newBuf = ByteBuffer.allocateDirect(needed);
+            newBuf.put(buf);
+            buf = newBuf;
+        } else {
+            buf.compact();
+        }
+
+        while (ch.read(buf) > 0 && buf.position() < needed) {
+            // keep reading
+        }
+        buf.flip();
+        return buf.limit() > 0;
+    }
 }
--- a/src/converter/one/jfr/StackTrace.java
+++ b/src/converter/one/jfr/StackTrace.java
@@ -19,10 +19,11 @@ package one.jfr;
 public class StackTrace {
    public final long[] methods;
    public final byte[] types;
-    public long samples;
+    public final int[] locations;

-    public StackTrace(long[] methods, byte[] types) {
+    public StackTrace(long[] methods, byte[] types, int[] locations) {
        this.methods = methods;
        this.types = types;
+        this.locations = locations;
    }
 }
--- a/src/converter/one/jfr/event/AllocationSample.java
+++ b/src/converter/one/jfr/event/AllocationSample.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.jfr.event;
+
+public class AllocationSample extends Event {
+    public final int classId;
+    public final long allocationSize;
+    public final long tlabSize;
+
+    public AllocationSample(long time, int tid, int stackTraceId, int classId, long allocationSize, long tlabSize) {
+        super(time, tid, stackTraceId);
+        this.classId = classId;
+        this.allocationSize = allocationSize;
+        this.tlabSize = tlabSize;
+    }
+
+    @Override
+    public int hashCode() {
+        return classId * 127 + stackTraceId + (tlabSize == 0 ? 17 : 0);
+    }
+
+    @Override
+    public boolean sameGroup(Event o) {
+        if (o instanceof AllocationSample) {
+            AllocationSample a = (AllocationSample) o;
+            return classId == a.classId && (tlabSize == 0) == (a.tlabSize == 0);
+        }
+        return false;
+    }
+
+    @Override
+    public long value() {
+        return tlabSize != 0 ? tlabSize : allocationSize;
+    }
+}
--- a/src/converter/one/jfr/event/ContendedLock.java
+++ b/src/converter/one/jfr/event/ContendedLock.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.jfr.event;
+
+public class ContendedLock extends Event {
+    public final long duration;
+    public final int classId;
+
+    public ContendedLock(long time, int tid, int stackTraceId, long duration, int classId) {
+        super(time, tid, stackTraceId);
+        this.duration = duration;
+        this.classId = classId;
+    }
+
+    @Override
+    public int hashCode() {
+        return classId * 127 + stackTraceId;
+    }
+
+    @Override
+    public boolean sameGroup(Event o) {
+        if (o instanceof ContendedLock) {
+            ContendedLock c = (ContendedLock) o;
+            return classId == c.classId;
+        }
+        return false;
+    }
+
+    @Override
+    public long value() {
+        return duration;
+    }
+}
--- a/src/converter/one/jfr/event/Event.java
+++ b/src/converter/one/jfr/event/Event.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 Andrei Pangin
+ * Copyright 2021 Andrei Pangin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -14,23 +14,34 @@
 * limitations under the License.
 */

-package one.jfr;
+package one.jfr.event;

-public class Sample implements Comparable<Sample> {
+public abstract class Event implements Comparable<Event> {
    public final long time;
    public final int tid;
    public final int stackTraceId;
-    public final int threadState;

-    public Sample(long time, int tid, int stackTraceId, int threadState) {
+    protected Event(long time, int tid, int stackTraceId) {
        this.time = time;
        this.tid = tid;
        this.stackTraceId = stackTraceId;
-        this.threadState = threadState;
    }

    @Override
-    public int compareTo(Sample o) {
+    public int compareTo(Event o) {
        return Long.compare(time, o.time);
    }
+
+    @Override
+    public int hashCode() {
+        return stackTraceId;
+    }
+
+    public boolean sameGroup(Event o) {
+        return getClass() == o.getClass();
+    }
+
+    public long value() {
+        return 1;
+    }
 }
--- a/src/converter/one/jfr/event/EventAggregator.java
+++ b/src/converter/one/jfr/event/EventAggregator.java
@@ -0,0 +1,103 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.jfr.event;
+
+public class EventAggregator {
+    private static final int INITIAL_CAPACITY = 1024;
+
+    private final boolean threads;
+    private final boolean total;
+    private Event[] keys;
+    private long[] values;
+    private int size;
+
+    public EventAggregator(boolean threads, boolean total) {
+        this.threads = threads;
+        this.total = total;
+        this.keys = new Event[INITIAL_CAPACITY];
+        this.values = new long[INITIAL_CAPACITY];
+    }
+
+    public void collect(Event e) {
+        int mask = keys.length - 1;
+        int i = hashCode(e) & mask;
+        while (keys[i] != null) {
+            if (sameGroup(keys[i], e)) {
+                values[i] += total ? e.value() : 1;
+                return;
+            }
+            i = (i + 1) & mask;
+        }
+
+        keys[i] = e;
+        values[i] = total ? e.value() : 1;
+
+        if (++size * 2 > keys.length) {
+            resize(keys.length * 2);
+        }
+    }
+
+    public long getValue(Event e) {
+        int mask = keys.length - 1;
+        int i = hashCode(e) & mask;
+        while (keys[i] != null && !sameGroup(keys[i], e)) {
+            i = (i + 1) & mask;
+        }
+        return values[i];
+    }
+
+    public void forEach(Visitor visitor) {
+        for (int i = 0; i < keys.length; i++) {
+            if (keys[i] != null) {
+                visitor.visit(keys[i], values[i]);
+            }
+        }
+    }
+
+    private int hashCode(Event e) {
+        return e.hashCode() + (threads ? e.tid * 31 : 0);
+    }
+
+    private boolean sameGroup(Event e1, Event e2) {
+        return e1.stackTraceId == e2.stackTraceId && (!threads || e1.tid == e2.tid) && e1.sameGroup(e2);
+    }
+
+    private void resize(int newCapacity) {
+        Event[] newKeys = new Event[newCapacity];
+        long[] newValues = new long[newCapacity];
+        int mask = newKeys.length - 1;
+
+        for (int i = 0; i < keys.length; i++) {
+            if (keys[i] != null) {
+                for (int j = hashCode(keys[i]) & mask; ; j = (j + 1) & mask) {
+                    if (newKeys[j] == null) {
+                        newKeys[j] = keys[i];
+                        newValues[j] = values[i];
+                        break;
+                    }
+                }
+            }
+        }
+
+        keys = newKeys;
+        values = newValues;
+    }
+
+    public interface Visitor {
+        void visit(Event event, long value);
+    }
+}
--- a/src/converter/one/jfr/event/ExecutionSample.java
+++ b/src/converter/one/jfr/event/ExecutionSample.java
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.jfr.event;
+
+public class ExecutionSample extends Event {
+    public final int threadState;
+
+    public ExecutionSample(long time, int tid, int stackTraceId, int threadState) {
+        super(time, tid, stackTraceId);
+        this.threadState = threadState;
+    }
+}
--- a/src/dwarf.cpp
+++ b/src/dwarf.cpp
@@ -0,0 +1,353 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include "dwarf.h"
+#include "log.h"
+
+
+enum {
+    DW_CFA_nop                = 0x0,
+    DW_CFA_set_loc            = 0x1,
+    DW_CFA_advance_loc1       = 0x2,
+    DW_CFA_advance_loc2       = 0x3,
+    DW_CFA_advance_loc4       = 0x4,
+    DW_CFA_offset_extended    = 0x5,
+    DW_CFA_restore_extended   = 0x6,
+    DW_CFA_undefined          = 0x7,
+    DW_CFA_same_value         = 0x8,
+    DW_CFA_register           = 0x9,
+    DW_CFA_remember_state     = 0xa,
+    DW_CFA_restore_state      = 0xb,
+    DW_CFA_def_cfa            = 0xc,
+    DW_CFA_def_cfa_register   = 0xd,
+    DW_CFA_def_cfa_offset     = 0xe,
+    DW_CFA_def_cfa_expression = 0xf,
+    DW_CFA_expression         = 0x10,
+    DW_CFA_offset_extended_sf = 0x11,
+    DW_CFA_def_cfa_sf         = 0x12,
+    DW_CFA_def_cfa_offset_sf  = 0x13,
+    DW_CFA_val_offset         = 0x14,
+    DW_CFA_val_offset_sf      = 0x15,
+    DW_CFA_val_expression     = 0x16,
+    DW_CFA_GNU_args_size      = 0x2e,
+
+    DW_CFA_advance_loc        = 0x1,
+    DW_CFA_offset             = 0x2,
+    DW_CFA_restore            = 0x3,
+};
+
+enum {
+    DW_OP_breg_pc = 0x70 + DW_REG_PC,
+    DW_OP_const1u = 0x08,
+    DW_OP_const1s = 0x09,
+    DW_OP_const2u = 0x0a,
+    DW_OP_const2s = 0x0b,
+    DW_OP_const4u = 0x0c,
+    DW_OP_const4s = 0x0d,
+    DW_OP_constu  = 0x10,
+    DW_OP_consts  = 0x11,
+    DW_OP_minus   = 0x1c,
+    DW_OP_plus    = 0x22,
+};
+
+
+FrameDesc FrameDesc::default_frame = {0, DW_REG_FP | (2 * DW_STACK_SLOT) << 8, -2 * DW_STACK_SLOT};
+
+
+DwarfParser::DwarfParser(const char* name, const char* image_base, const char* eh_frame_hdr) {
+    _name = name;
+    _image_base = image_base;
+
+    _capacity = 128;
+    _count = 0;
+    _table = (FrameDesc*)malloc(_capacity * sizeof(FrameDesc));
+    _prev = NULL;
+
+    _code_align = sizeof(instruction_t);
+    _data_align = -(int)sizeof(void*);
+
+    parse(eh_frame_hdr);
+}
+
+void DwarfParser::parse(const char* eh_frame_hdr) {
+    u8 version = eh_frame_hdr[0];
+    u8 eh_frame_ptr_enc = eh_frame_hdr[1];
+    u8 fde_count_enc = eh_frame_hdr[2];
+    u8 table_enc = eh_frame_hdr[3];
+
+    if (version != 1 || (eh_frame_ptr_enc & 0x7) != 0x3 || (fde_count_enc & 0x7) != 0x3 || (table_enc & 0xf7) != 0x33) {
+        Log::warn("Unsupported .eh_frame_hdr [%02x%02x%02x%02x] in %s",
+                  version, eh_frame_ptr_enc, fde_count_enc, table_enc, _name);
+        return;
+    }
+
+    int fde_count = *(int*)(eh_frame_hdr + 8);
+    int* table =  (int*)(eh_frame_hdr + 16);
+    for (int i = 0; i < fde_count; i++) {
+        _ptr = eh_frame_hdr + table[i * 2];
+        parseFde();
+    }
+}
+
+void DwarfParser::parseCie() {
+    u32 cie_len = get32();
+    if (cie_len == 0 || cie_len == 0xffffffff) {
+        return;
+    }
+
+    const char* cie_start = _ptr;
+    _ptr += 5;
+    while (*_ptr++) {}
+    _code_align = getLeb();
+    _data_align = getSLeb();
+    _ptr = cie_start + cie_len;
+}
+
+void DwarfParser::parseFde() {
+    u32 fde_len = get32();
+    if (fde_len == 0 || fde_len == 0xffffffff) {
+        return;
+    }
+
+    const char* fde_start = _ptr;
+    u32 cie_offset = get32();
+    if (_count == 0) {
+        _ptr = fde_start - cie_offset;
+        parseCie();
+        _ptr = fde_start + 4;
+    }
+
+    u32 range_start = getPtr() - _image_base;
+    u32 range_len = get32();
+    _ptr += getLeb();
+    parseInstructions(range_start, fde_start + fde_len);
+    addRecord(range_start + range_len, DW_REG_SP, DW_STACK_SLOT, DW_SAME_FP);
+}
+
+void DwarfParser::parseInstructions(u32 loc, const char* end) {
+    const u32 code_align = _code_align;
+    const int data_align = _data_align;
+
+    u32 cfa_reg = DW_REG_SP;
+    int cfa_off = DW_STACK_SLOT;
+    int fp_off = DW_SAME_FP;
+    int pc_off = -DW_STACK_SLOT;
+
+    u32 rem_cfa_reg;
+    int rem_cfa_off;
+    int rem_fp_off;
+    int rem_pc_off;
+
+    while (_ptr < end) {
+        u8 op = get8();
+        switch (op >> 6) {
+            case 0:
+                switch (op) {
+                    case DW_CFA_nop:
+                    case DW_CFA_set_loc:
+                        _ptr = end;
+                        break;
+                    case DW_CFA_advance_loc1:
+                        addRecord(loc, cfa_reg, cfa_off, fp_off);
+                        loc += get8() * code_align;
+                        break;
+                    case DW_CFA_advance_loc2:
+                        addRecord(loc, cfa_reg, cfa_off, fp_off);
+                        loc += get16() * code_align;
+                        break;
+                    case DW_CFA_advance_loc4:
+                        addRecord(loc, cfa_reg, cfa_off, fp_off);
+                        loc += get32() * code_align;
+                        break;
+                    case DW_CFA_offset_extended:
+                        switch (getLeb()) {
+                            case DW_REG_FP: fp_off = getLeb() * data_align; break;
+                            case DW_REG_PC: pc_off = getLeb() * data_align; break;
+                            default: skipLeb();
+                        }
+                        break;
+                    case DW_CFA_restore_extended:
+                    case DW_CFA_undefined:
+                    case DW_CFA_same_value:
+                        skipLeb();
+                        break;
+                    case DW_CFA_register:
+                        skipLeb();
+                        skipLeb();
+                        break;
+                    case DW_CFA_remember_state:
+                        rem_cfa_reg = cfa_reg;
+                        rem_cfa_off = cfa_off;
+                        rem_fp_off = fp_off;
+                        rem_pc_off = pc_off;
+                        break;
+                    case DW_CFA_restore_state:
+                        cfa_reg = rem_cfa_reg;
+                        cfa_off = rem_cfa_off;
+                        fp_off = rem_fp_off;
+                        pc_off = rem_pc_off;
+                        break;
+                    case DW_CFA_def_cfa:
+                        cfa_reg = getLeb();
+                        cfa_off = getLeb();
+                        break;
+                    case DW_CFA_def_cfa_register:
+                        cfa_reg = getLeb();
+                        break;
+                    case DW_CFA_def_cfa_offset:
+                        cfa_off = getLeb();
+                        break;
+                    case DW_CFA_def_cfa_expression: {
+                        u32 len = getLeb();
+                        cfa_reg = len == 11 ? DW_REG_PLT : DW_REG_INVALID;
+                        cfa_off = DW_STACK_SLOT;
+                        _ptr += len;
+                        break;
+                    }
+                    case DW_CFA_expression:
+                        skipLeb();
+                        _ptr += getLeb();
+                        break;
+                    case DW_CFA_offset_extended_sf:
+                        switch (getLeb()) {
+                            case DW_REG_FP: fp_off = getSLeb() * data_align; break;
+                            case DW_REG_PC: pc_off = getSLeb() * data_align; break;
+                            default: skipLeb();
+                        }
+                        break;
+                    case DW_CFA_def_cfa_sf:
+                        cfa_reg = getLeb();
+                        cfa_off = getSLeb() * data_align;
+                        break;
+                    case DW_CFA_def_cfa_offset_sf:
+                        cfa_off = getSLeb() * data_align;
+                        break;
+                    case DW_CFA_val_offset:
+                    case DW_CFA_val_offset_sf:
+                        skipLeb();
+                        skipLeb();
+                        break;
+                    case DW_CFA_val_expression:
+                        if (getLeb() == DW_REG_PC) {
+                            int pc_off = parseExpression();
+                            if (pc_off != 0) {
+                                fp_off = DW_PC_OFFSET | (pc_off << 1);
+                            }
+                        } else {
+                            _ptr += getLeb();
+                        }
+                        break;
+                    case DW_CFA_GNU_args_size:
+                        skipLeb();
+                        break;
+                    default:
+                        Log::warn("Unknown DWARF instruction 0x%x in %s", op, _name);
+                        return;
+                }
+                break;
+            case DW_CFA_advance_loc:
+                addRecord(loc, cfa_reg, cfa_off, fp_off);
+                loc += (op & 0x3f) * code_align;
+                break;
+            case DW_CFA_offset:
+                switch (op & 0x3f) {
+                    case DW_REG_FP: fp_off = getLeb() * data_align; break;
+                    case DW_REG_PC: pc_off = getLeb() * data_align; break;
+                    default: skipLeb();
+                }
+                break;
+            case DW_CFA_restore:
+                break;
+        }
+    }
+
+    addRecord(loc, cfa_reg, cfa_off, fp_off);
+}
+
+// Parse a limited subset of DWARF expressions, which is used in DW_CFA_val_expression
+// to point to the previous PC relative to the current PC.
+// Returns the offset of the previous PC from the current PC.
+int DwarfParser::parseExpression() {
+    int pc_off = 0;
+    int tos = 0;
+
+    u32 len = getLeb();
+    const char* end = _ptr + len;
+
+    while (_ptr < end) {
+        u8 op = get8();
+        switch (op) {
+            case DW_OP_breg_pc:
+                pc_off = getSLeb();
+                break;
+            case DW_OP_const1u:
+                tos = get8();
+                break;
+            case DW_OP_const1s:
+                tos = (signed char)get8();
+                break;
+            case DW_OP_const2u:
+                tos = get16();
+                break;
+            case DW_OP_const2s:
+                tos = (short)get16();
+                break;
+            case DW_OP_const4u:
+            case DW_OP_const4s:
+                tos = get32();
+                break;
+            case DW_OP_constu:
+                tos = getLeb();
+                break;
+            case DW_OP_consts:
+                tos = getSLeb();
+                break;
+            case DW_OP_minus:
+                pc_off -= tos;
+                break;
+            case DW_OP_plus:
+                pc_off += tos;
+                break;
+            default:
+                Log::warn("Unknown DWARF opcode 0x%x in %s", op, _name);
+                _ptr = end;
+                return 0;
+        }
+    }
+
+    return pc_off;
+}
+
+void DwarfParser::addRecord(u32 loc, u32 cfa_reg, int cfa_off, int fp_off) {
+    int cfa = cfa_reg | cfa_off << 8;
+    if (_prev == NULL || (_prev->loc == loc && --_count >= 0) || _prev->cfa != cfa || _prev->fp_off != fp_off) {
+        _prev = addRecordRaw(loc, cfa, fp_off);
+    }
+}
+
+FrameDesc* DwarfParser::addRecordRaw(u32 loc, int cfa, int fp_off) {
+    if (_count >= _capacity) {
+        _capacity *= 2;
+        _table = (FrameDesc*)realloc(_table, _capacity * sizeof(FrameDesc));
+    }
+
+    FrameDesc* f = &_table[_count++];
+    f->loc = loc;
+    f->cfa = cfa;
+    f->fp_off = fp_off;
+    return f;
+}
--- a/src/dwarf.h
+++ b/src/dwarf.h
@@ -0,0 +1,160 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _DWARF_H
+#define _DWARF_H
+
+#include <stddef.h>
+#include "arch.h"
+
+
+#if defined(__x86_64__)
+
+#define DWARF_SUPPORTED true
+
+const int DW_REG_FP = 6;
+const int DW_REG_SP = 7;
+const int DW_REG_PC = 16;
+
+#elif defined(__i386__)
+
+#define DWARF_SUPPORTED true
+
+const int DW_REG_FP = 5;
+const int DW_REG_SP = 4;
+const int DW_REG_PC = 8;
+
+#else
+
+#define DWARF_SUPPORTED false
+
+const int DW_REG_FP = 0;
+const int DW_REG_SP = 1;
+const int DW_REG_PC = 2;
+
+#endif
+
+const int DW_REG_PLT = 128;      // denotes special rule for PLT entries
+const int DW_REG_INVALID = 255;  // denotes unsupported configuration
+
+const int DW_PC_OFFSET = 1;
+const int DW_SAME_FP = 0x80000000;
+const int DW_STACK_SLOT = sizeof(void*);
+
+
+struct FrameDesc {
+    u32 loc;
+    int cfa;
+    int fp_off;
+
+    static FrameDesc default_frame;
+
+    static int comparator(const void* p1, const void* p2) {
+        FrameDesc* fd1 = (FrameDesc*)p1;
+        FrameDesc* fd2 = (FrameDesc*)p2;
+        return (int)(fd1->loc - fd2->loc);
+    }
+};
+
+
+class DwarfParser {
+  private:
+    const char* _name;
+    const char* _image_base;
+    const char* _ptr;
+
+    int _capacity;
+    int _count;
+    FrameDesc* _table;
+    FrameDesc* _prev;
+
+    u32 _code_align;
+    int _data_align;
+
+    const char* add(size_t size) {
+        const char* ptr = _ptr;
+        _ptr = ptr + size;
+        return ptr;
+    }
+
+    u8 get8() {
+        return *_ptr++;
+    }
+
+    u16 get16() {
+        return *(u16*)add(2);
+    }
+
+    u32 get32() {
+        return *(u32*)add(4);
+    }
+
+    u32 getLeb() {
+        u32 result = 0;
+        for (u32 shift = 0; ; shift += 7) {
+            u8 b = *_ptr++;
+            result |= (b & 0x7f) << shift;
+            if ((b & 0x80) == 0) {
+                return result;
+            }
+        }
+    }
+
+    int getSLeb() {
+        int result = 0;
+        for (u32 shift = 0; ; shift += 7) {
+            u8 b = *_ptr++;
+            result |= (b & 0x7f) << shift;
+            if ((b & 0x80) == 0) {
+                if ((b & 0x40) != 0 && (shift += 7) < 32) {
+                    result |= -1 << shift;
+                }
+                return result;
+            }
+        }
+    }
+
+    void skipLeb() {
+        while (*_ptr++ & 0x80) {}
+    }
+
+    const char* getPtr() {
+        const char* ptr = _ptr;
+        return ptr + *(int*)add(4);
+    }
+
+    void parse(const char* eh_frame_hdr);
+    void parseCie();
+    void parseFde();
+    void parseInstructions(u32 loc, const char* end);
+    int parseExpression();
+
+    void addRecord(u32 loc, u32 cfa_reg, int cfa_off, int fp_off);
+    FrameDesc* addRecordRaw(u32 loc, int cfa, int fp_off);
+
+  public:
+    DwarfParser(const char* name, const char* image_base, const char* eh_frame_hdr);
+
+    FrameDesc* table() const {
+        return _table;
+    }
+
+    int count() const {
+        return _count;
+    }
+};
+
+#endif // _DWARF_H
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -15,60 +15,17 @@
 */

 #include "engine.h"
-#include "stackFrame.h"


-volatile bool Engine::_enabled;
+volatile bool Engine::_enabled = false;

 Error Engine::check(Arguments& args) {
    return Error::OK;
 }

-CStack Engine::cstack() {
-    return CSTACK_FP;
+Error Engine::start(Arguments& args) {
+    return Error::OK;
 }

-int Engine::getNativeTrace(void* ucontext, int tid, const void** callchain, int max_depth,
-                           CodeCache* java_methods, CodeCache* runtime_stubs) {
-    const void* pc;
-    uintptr_t fp;
-    uintptr_t prev_fp = (uintptr_t)&fp;
-    uintptr_t bottom = prev_fp + 0x100000;
-
-    if (ucontext == NULL) {
-        pc = __builtin_return_address(0);
-        fp = (uintptr_t)__builtin_frame_address(1);
-    } else {
-        StackFrame frame(ucontext);
-        pc = (const void*)frame.pc();
-        fp = frame.fp();
-    }
-
-    int depth = 0;
-    const void* const valid_pc = (const void* const)0x1000;
-
-    // Walk until the bottom of the stack or until the first Java frame
-    while (depth < max_depth && pc >= valid_pc) {
-        if (java_methods->contains(pc) || runtime_stubs->contains(pc)) {
-            break;
-        }
-
-        callchain[depth++] = pc;
-
-        // Check if the next frame is below on the current stack
-        if (fp <= prev_fp || fp >= prev_fp + 0x40000 || fp >= bottom) {
-            break;
-        }
-
-        // Frame pointer must be word aligned
-        if ((fp & (sizeof(uintptr_t) - 1)) != 0) {
-            break;
-        }
-
-        prev_fp = fp;
-        pc = ((const void**)fp)[1];
-        fp = ((uintptr_t*)fp)[0];
-    }
-
-    return depth;
+void Engine::stop() {
 }
--- a/src/engine.h
+++ b/src/engine.h
@@ -18,50 +18,48 @@
 #define _ENGINE_H

 #include "arguments.h"
-#include "codeCache.h"


 class Engine {
  protected:
    static volatile bool _enabled;

+    static bool updateCounter(volatile unsigned long long& counter, unsigned long long value, unsigned long long interval) {
+        if (interval <= 1) {
+            return true;
+        }
+
+        while (true) {
+            unsigned long long prev = counter;
+            unsigned long long next = prev + value;
+            if (next < interval) {
+                if (__sync_bool_compare_and_swap(&counter, prev, next)) {
+                    return false;
+                }
+            } else {
+                if (__sync_bool_compare_and_swap(&counter, prev, next % interval)) {
+                    return true;
+                }
+            }
+        }
+    }
+
  public:
-    virtual const char* name() = 0;
-    virtual const char* units() = 0;
+    virtual const char* title() {
+        return "Flame Graph";
+    }
+
+    virtual const char* units() {
+        return "total";
+    }

    virtual Error check(Arguments& args);
-    virtual Error start(Arguments& args) = 0;
-    virtual void stop() = 0;
-
-    virtual CStack cstack();
-    virtual int getNativeTrace(void* ucontext, int tid, const void** callchain, int max_depth,
-                               CodeCache* java_methods, CodeCache* runtime_stubs);
+    virtual Error start(Arguments& args);
+    virtual void stop();

    void enableEvents(bool enabled) {
        _enabled = enabled;
    }
 };

-class NoopEngine : public Engine {
-  public:
-    const char* name() {
-        return "noop";
-    }
-
-    const char* units() {
-        return "ns";
-    }
-
-    Error start(Arguments& args) {
-        return Error::OK;
-    }
-
-    void stop() {
-    }
-
-    CStack cstack() {
-        return CSTACK_NO;
-    }
-};
-
 #endif // _ENGINE_H
--- a/src/fdtransfer/fdtransfer.h
+++ b/src/fdtransfer/fdtransfer.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _FDTRANSFER_H
+#define _FDTRANSFER_H
+
+#ifdef __linux__
+
+#include <linux/perf_event.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#define ARRAY_SIZE(arr)  (sizeof(arr) / sizeof(arr[0]))
+
+
+// base header for all requests
+enum request_type {
+    PERF_FD,
+    KALLSYMS_FD,
+};
+
+struct fd_request {
+    // of type "enum request_type"
+    unsigned int type;
+};
+
+struct perf_fd_request {
+    struct fd_request header;
+    int tid;
+    struct perf_event_attr attr;
+};
+
+struct fd_response {
+    // of type "enum request_type"
+    unsigned int type;
+    // 0 on success, otherwise errno
+    int error;
+};
+
+struct perf_fd_response {
+    struct fd_response header;
+    int tid;
+};
+
+
+static inline bool socketPathForPid(int pid, struct sockaddr_un *sun, socklen_t *addrlen) {
+    sun->sun_path[0] = '\0';
+    const int max_size = sizeof(sun->sun_path) - 1;
+    const int path_len = snprintf(sun->sun_path + 1, max_size, "async-profiler-%d", pid);
+    if (path_len > max_size) {
+        return false;
+    }
+
+    sun->sun_family = AF_UNIX;
+    // +1 for the first \0 byte
+    *addrlen = sizeof(*sun) - (sizeof(sun->sun_path) - (path_len + 1));
+
+    return true;
+}
+
+static inline bool socketPath(const char *path, struct sockaddr_un *sun, socklen_t *addrlen) {
+    const int path_len = strlen(path);
+    if (path_len > sizeof(sun->sun_path)) {
+        return false;
+    }
+    memcpy(sun->sun_path, path, path_len);
+
+    sun->sun_family = AF_UNIX;
+    *addrlen = sizeof(*sun) - (sizeof(sun->sun_path) - path_len);
+
+    return true;
+}
+
+#endif // __linux__
+
+#endif // _FDTRANSFER_H
--- a/src/fdtransfer/fdtransferServer.cpp
+++ b/src/fdtransfer/fdtransferServer.cpp
@@ -0,0 +1,378 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/sendfile.h>
+#include <sys/syscall.h>
+#include <sys/wait.h>
+
+#include "fdtransfer.h"
+#include "../jattach/psutil.h"
+
+
+class FdTransferServer {
+  private:
+    static int _server;
+    static int _peer;
+    static int copyFile(const char* src_name, const char* dst_name, mode_t mode);
+    static bool sendFd(int fd, struct fd_response *resp, size_t resp_size);
+
+  public:
+    static void closeServer() { close(_server); }
+    static void closePeer() { close(_peer); }
+    static bool bindServer(struct sockaddr_un *sun, socklen_t addrlen, int accept_timeout);
+    static bool acceptPeer(int *peer_pid);
+    static bool serveRequests(int peer_pid);
+};
+
+int FdTransferServer::_server;
+int FdTransferServer::_peer;
+
+bool FdTransferServer::bindServer(struct sockaddr_un *sun, socklen_t addrlen, int accept_timeout) {
+    _server = socket(AF_UNIX, SOCK_SEQPACKET, 0);
+    if (_server == -1) {
+        perror("FdTransfer socket()");
+        return false;
+    }
+
+    // Arbitrary timeout, to prevent it from listening forever.
+    if (accept_timeout > 0) {
+        const struct timeval timeout = {accept_timeout, 0};
+        if (setsockopt(_server, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout)) < 0) {
+            perror("FdTransfer setsockopt(SO_RCVTIMEO)");
+            close(_server);
+            return false;
+        }
+    }
+
+    if (bind(_server, (const struct sockaddr*)sun, addrlen) < 0 || listen(_server, 1) < 0) {
+        perror("FdTransfer listen()");
+        close(_server);
+        return false;
+    }
+
+    return true;
+}
+
+bool FdTransferServer::acceptPeer(int *peer_pid) {
+    _peer = accept(_server, NULL, NULL);
+    if (_peer == -1) {
+        perror("FdTransfer accept()");
+        return false;
+    }
+
+    struct ucred cred;
+    socklen_t len = sizeof(cred);
+    if (getsockopt(_peer, SOL_SOCKET, SO_PEERCRED, &cred, &len) == -1) {
+        perror("getsockopt(SO_PEERCRED)");
+        close(_peer);
+        return false;
+    }
+
+    if (*peer_pid != 0) {
+        if (cred.pid != *peer_pid) {
+            fprintf(stderr, "Unexpected connection from PID %d, expected from %d\n", cred.pid, *peer_pid);
+            close(_peer);
+            return false;
+        }
+    } else {
+        *peer_pid = cred.pid;
+    }
+
+    return true;
+}
+
+bool FdTransferServer::serveRequests(int peer_pid) {
+    // Close the server side, don't need it anymore.
+    FdTransferServer::closeServer();
+
+    void *perf_mmap_ringbuf[1024] = {};
+    size_t ringbuf_index = 0;
+    const size_t perf_mmap_size = 2 * sysconf(_SC_PAGESIZE);
+
+    while (1) {
+        unsigned char request_buf[1024];
+        struct fd_request *req = (struct fd_request *)request_buf;
+
+        ssize_t ret = recv(_peer, req, sizeof(request_buf), 0);
+
+        if (ret == 0) {
+            // EOF means done
+            return true;
+        } else if (ret < 0) {
+            perror("recv()");
+            break;
+        }
+
+        switch (req->type) {
+        case PERF_FD: {
+            struct perf_fd_request *request = (struct perf_fd_request*)req;
+            int perf_fd = -1;
+            int error;
+
+            // In pid == 0 mode, allow all perf_event_open requests.
+            // Otherwise, verify the thread belongs to PID.
+            if (peer_pid == 0 || syscall(__NR_tgkill, peer_pid, request->tid, 0) == 0) {
+                perf_fd = syscall(__NR_perf_event_open, &request->attr, request->tid, -1, -1, 0);
+                error = perf_fd < 0 ? errno : 0;
+            } else {
+                fprintf(stderr, "Target has requested perf_event_open for TID %d which is not a thread of process %d\n", request->tid, peer_pid);
+                error = ESRCH;
+            }
+
+            // Map the perf buffer here (mapping perf fds may require privileges, and fdtransfer has them while the target application does not
+            // necessarily; if pages are already mapped, the same physical pages will be used when the profiler agent maps them again, requiring
+            // no privileges this time)
+            if (error == 0) {
+                // Settings match the mmap() done in PerfEvents::createForThread().
+                void *map_result = mmap(NULL, perf_mmap_size, PROT_READ | PROT_WRITE, MAP_SHARED, perf_fd, 0);
+                // Ignore errors - if this fails, let it fail again in the profiler again & produce a proper error for the user.
+
+                // Free next entry in the ring buffer, if it was previously allocated.
+                if (perf_mmap_ringbuf[ringbuf_index] != NULL && perf_mmap_ringbuf[ringbuf_index] != MAP_FAILED) {
+                    (void)munmap(perf_mmap_ringbuf[ringbuf_index], perf_mmap_size);
+                }
+                // Store it in the ring buffer so we can free it later.
+                perf_mmap_ringbuf[ringbuf_index] = map_result;
+
+                ringbuf_index++;
+                ringbuf_index = ringbuf_index % ARRAY_SIZE(perf_mmap_ringbuf);
+            }
+
+            struct perf_fd_response resp;
+            resp.header.type = request->header.type;
+            resp.header.error = error;
+            resp.tid = request->tid;
+            sendFd(perf_fd, &resp.header, sizeof(resp));
+            close(perf_fd);
+            break;
+        }
+
+        case KALLSYMS_FD: {
+            // can't directly pass the fd of /proc/kallsyms, because before Linux 4.15 the permission check
+            // was conducted on each read.
+            // it's simpler to copy the file to a temporary location and pass the fd of it (compared to passing the
+            // entire contents over the peer socket)
+            char tmp_path[256];
+            snprintf(tmp_path, sizeof(tmp_path), "/tmp/async-profiler-kallsyms.%d", getpid());
+
+            int kallsyms_fd = -1;
+            int error = copyFile("/proc/kallsyms", tmp_path, 0600);
+            if (error == 0) {
+                kallsyms_fd = open(tmp_path, O_RDONLY);
+                if (kallsyms_fd == -1) {
+                    error = errno;
+                } else {
+                    unlink(tmp_path);
+                }
+            }
+
+            struct fd_response resp;
+            resp.type = req->type;
+            resp.error = error;
+            sendFd(kallsyms_fd, &resp, sizeof(resp));
+            close(kallsyms_fd);
+            break;
+        }
+
+        default:
+            fprintf(stderr, "Unknown request type %u\n", req->type);
+            break;
+        }
+    }
+
+    return false;
+}
+
+int FdTransferServer::copyFile(const char* src_name, const char* dst_name, mode_t mode) {
+    int src = open(src_name, O_RDONLY);
+    if (src == -1) {
+        return errno;
+    }
+
+    int dst = creat(dst_name, mode);
+    if (dst == -1) {
+        int result = errno;
+        close(src);
+        return result;
+    }
+
+    // copy_file_range() doesn't exist in older kernels, sendfile() no longer works in newer ones
+    char buf[65536];
+    ssize_t r;
+    while ((r = read(src, buf, sizeof(buf))) > 0) {
+        ssize_t w = write(dst, buf, r);
+        (void)w;
+    }
+
+    close(dst);
+    close(src);
+    return 0;
+}
+
+bool FdTransferServer::sendFd(int fd, struct fd_response *resp, size_t resp_size) {
+    struct msghdr msg = {0};
+
+    struct iovec iov[1];
+    iov[0].iov_base = resp;
+    iov[0].iov_len = resp_size;
+    msg.msg_iov = iov;
+    msg.msg_iovlen = ARRAY_SIZE(iov);
+
+    union {
+       char buf[CMSG_SPACE(sizeof(fd))];
+       struct cmsghdr align;
+    } u;
+
+    if (fd != -1) {
+        msg.msg_control = u.buf;
+        msg.msg_controllen = sizeof(u.buf);
+
+        struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
+        memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
+    }
+
+    ssize_t ret = sendmsg(_peer, &msg, 0);
+    if (ret < 0) {
+        perror("sendmsg()");
+        return false;
+    }
+
+    return true;
+}
+
+static int single_pid_server(int pid) {
+    // get its nspid prior to moving to its PID namespace.
+    int nspid;
+    uid_t _target_uid;
+    gid_t _target_gid;
+    if (get_process_info(pid, &_target_uid, &_target_gid, &nspid)) {
+        fprintf(stderr, "Process %d not found\n", pid);
+        return 1;
+    }
+
+    struct sockaddr_un sun;
+    socklen_t addrlen;
+    if (!socketPathForPid(nspid, &sun, &addrlen)) {
+        fprintf(stderr, "Path too long\n");
+        return 1;
+    }
+
+    // Create the server before forking, so w're ready to accept connections once our parent
+    // exits.
+
+    if (enter_ns(pid, "net") == -1) {
+        fprintf(stderr, "Failed to enter the net NS of target process %d\n", pid);
+        return 1;
+    }
+
+    if (!FdTransferServer::bindServer(&sun, addrlen, 10)) {
+        return 1;
+    }
+
+    if (!enter_ns(pid, "pid") == -1) {
+        fprintf(stderr, "Failed to enter the PID NS of target process %d\n", pid);
+        return 1;
+    }
+
+    // CLONE_NEWPID affects children only - so we fork here.
+    if (0 == fork()) {
+        return FdTransferServer::acceptPeer(&nspid) && FdTransferServer::serveRequests(nspid) ? 0 : 1;
+    } else {
+        // Exit now, let our caller continue.
+        return 0;
+    }
+}
+
+static int path_server(const char *path) {
+    struct sockaddr_un sun;
+    socklen_t addrlen;
+
+    struct sigaction sigchld_action;
+    sigchld_action.sa_handler = SIG_DFL;
+    sigchld_action.sa_flags = SA_NOCLDWAIT;
+    sigaction(SIGCHLD, &sigchld_action, NULL);
+
+    if (!socketPath(path, &sun, &addrlen)) {
+        fprintf(stderr, "Path '%s' is too long\n", path);
+        return 1;
+    }
+
+    if (!FdTransferServer::bindServer(&sun, addrlen, 0)) {
+        return 1;
+    }
+
+    printf("Server ready at '%s'\n", path);
+
+    while (1) {
+        int peer_pid = 0;
+        if (!FdTransferServer::acceptPeer(&peer_pid)) {
+            return 1;
+        }
+
+        // Enter its PID namespace.
+        if (enter_ns(peer_pid, "pid") == -1) {
+            fprintf(stderr, "Failed to enter the PID NS of target process %d\n", peer_pid);
+            return 1;
+        }
+
+        printf("Serving PID %d\n", peer_pid);
+
+        // We fork(), to actually move a PID namespace.
+        if (0 == fork()) {
+            return FdTransferServer::serveRequests(0) ? 0 : 1;
+        } else {
+            FdTransferServer::closePeer();
+        }
+
+        // Move back to our original PID namespace (reverts pid_for_children)
+        if (enter_ns(getpid(), "pid") == -1) {
+            fprintf(stderr, "Failed to exit the PID NS of target process %d\n", peer_pid);
+            return 1;
+        }
+    }
+}
+
+int main(int argc, const char** argv) {
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <pid>|<path>\n", argv[0]);
+        return 1;
+    }
+
+    int pid = atoi(argv[1]);
+    // 2 modes:
+    // pid == 0 - bind on a path and accept requests forever, from any PID, until being killed
+    // pid != 0 - bind on an abstract namespace UDS for that PID, accept requests only from that PID
+    //            until the single connection is closed.
+    if (pid != 0) {
+        return single_pid_server(pid);
+    } else {
+        return path_server(argv[1]);
+    }
+}
--- a/src/fdtransferClient.h
+++ b/src/fdtransferClient.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _FDTRANSFER_CLIENT_H
+#define _FDTRANSFER_CLIENT_H
+
+#ifdef __linux__
+
+#include "fdtransfer/fdtransfer.h"
+
+class FdTransferClient {
+  private:
+    static int _peer;
+
+    static int recvFd(unsigned int request_id, struct fd_response *resp, size_t resp_size);
+
+  public:
+    static bool connectToServer(const char *path, int pid);
+    static bool hasPeer() { return _peer != -1; }
+    static void closePeer() {
+        if (_peer != -1) {
+            close(_peer);
+            _peer = -1;
+        }
+    }
+
+    static int requestPerfFd(int *tid, struct perf_event_attr *attr);
+    static int requestKallsymsFd();
+};
+
+#else
+
+class FdTransferClient {
+  public:
+    static bool connectToServer(const char *path, int pid) { return false; }
+    static bool hasPeer() { return false; }
+    static void closePeer() { }
+};
+
+#endif // __linux__
+
+#endif // _FDTRANSFER_CLIENT_H
--- a/src/fdtransferClient_linux.cpp
+++ b/src/fdtransferClient_linux.cpp
@@ -0,0 +1,149 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifdef __linux__
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "fdtransferClient.h"
+#include "log.h"
+
+
+int FdTransferClient::_peer = -1;
+
+bool FdTransferClient::connectToServer(const char *path, int pid) {
+    _peer = socket(AF_UNIX, SOCK_SEQPACKET, 0);
+    if (_peer == -1) {
+        Log::warn("FdTransferClient socket(): %s", strerror(errno));
+        return false;
+    }
+
+    struct sockaddr_un sun;
+    socklen_t addrlen;
+    if (path != NULL) {
+        if (!socketPath(path, &sun, &addrlen)) {
+            return false;
+        }
+    } else {
+        if (!socketPathForPid(pid, &sun, &addrlen)) {
+            return false;
+        }
+    }
+
+    if (connect(_peer, (const struct sockaddr *)&sun, addrlen) == -1) {
+        Log::warn("FdTransferClient connect(): %s", strerror(errno));
+        return false;
+    }
+
+    return true;
+}
+
+int FdTransferClient::requestPerfFd(int *tid, struct perf_event_attr *attr) {
+    struct perf_fd_request request;
+    request.header.type = PERF_FD;
+    request.tid = *tid;
+    memcpy(&request.attr, attr, sizeof(request.attr));
+
+    if (send(_peer, &request, sizeof(request), 0) != sizeof(request)) {
+        Log::warn("FdTransferClient send(): %s", strerror(errno));
+        return -1;
+    }
+
+    struct perf_fd_response resp;
+    int fd = recvFd(request.header.type, &resp.header, sizeof(resp));
+    if (fd == -1) {
+        // Update errno for our caller.
+        errno = resp.header.error;
+    } else {
+        // Update the TID of createForThread, in case the multiple threads' requests got mixed up and we're
+        // now handling the response destined to another. It's alright - the other thread(s) will finish the
+        // handling of our TID perf fd.
+        *tid = resp.tid;
+    }
+    return fd;
+}
+
+int FdTransferClient::requestKallsymsFd() {
+    struct fd_request request;
+    request.type = KALLSYMS_FD;
+
+    if (send(_peer, &request, sizeof(request), 0) != sizeof(request)) {
+        Log::warn("FdTransferClient send(): %s", strerror(errno));
+        return -1;
+    }
+
+    struct fd_response resp;
+    int fd = recvFd(request.type, &resp, sizeof(resp));
+    if (fd == -1) {
+        errno = resp.error;
+    }
+
+    return fd;
+}
+
+int FdTransferClient::recvFd(unsigned int type, struct fd_response *resp, size_t resp_size) {
+    struct msghdr msg = {0};
+
+    struct iovec iov[1];
+    iov[0].iov_base = resp;
+    iov[0].iov_len = resp_size;
+    msg.msg_iov = iov;
+    msg.msg_iovlen = ARRAY_SIZE(iov);
+
+    int newfd;
+    union {
+        char buf[CMSG_SPACE(sizeof(newfd))];
+        struct cmsghdr align;
+    } u;
+    msg.msg_control = u.buf;
+    msg.msg_controllen = sizeof(u.buf);
+
+    ssize_t ret = recvmsg(_peer, &msg, 0);
+    if (ret < 0) {
+        Log::warn("FdTransferClient recvmsg(): %s", strerror(errno));
+        return -1;
+    }
+
+    if (resp->type != type) {
+        Log::warn("FdTransferClient recvmsg(): bad response type");
+        return -1;
+    }
+
+    if (resp->error == 0) {
+        struct cmsghdr *cmptr = CMSG_FIRSTHDR(&msg);
+        if (cmptr != NULL && cmptr->cmsg_len == CMSG_LEN(sizeof(newfd))
+            && cmptr->cmsg_level == SOL_SOCKET && cmptr->cmsg_type == SCM_RIGHTS) {
+
+            newfd = *((int*)CMSG_DATA(cmptr));
+        } else {
+            Log::warn("FdTransferClient recvmsg(): unexpected response with no SCM_RIGHTS: %s", strerror(errno));
+            newfd = -1;
+        }
+    } else {
+        newfd = -1;
+    }
+
+    return newfd;
+}
+
+#endif // __linux__
--- a/src/flameGraph.cpp
+++ b/src/flameGraph.cpp
@@ -18,8 +18,12 @@
 #include <vector>
 #include <stdio.h>
 #include "flameGraph.h"
+#include "vmEntry.h"


+// Browsers refuse to draw on canvas larger than 32767 px
+const int MAX_CANVAS_HEIGHT = 32767;
+
 static const char FLAMEGRAPH_HEADER[] =
    "<!DOCTYPE html>\n"
    "<html lang='en'>\n"
@@ -72,11 +76,13 @@ static const char FLAMEGRAPH_HEADER[] =
    "\tc.font = document.body.style.font;\n"
    "\n"
    "\tconst palette = [\n"
+    "\t\t[0xb2e1b2, 20, 20, 20],\n"
    "\t\t[0x50e150, 30, 30, 30],\n"
-    "\t\t[0x50bebe, 30, 30, 30],\n"
-    "\t\t[0xe17d00, 30, 30,  0],\n"
-    "\t\t[0xc8c83c, 30, 30, 10],\n"
+    "\t\t[0x50cccc, 30, 30, 30],\n"
    "\t\t[0xe15a5a, 30, 40, 40],\n"
+    "\t\t[0xc8c83c, 30, 30, 10],\n"
+    "\t\t[0xe17d00, 30, 30,  0],\n"
+    "\t\t[0xcce880, 20, 20, 20],\n"
    "\t];\n"
    "\n"
    "\tfunction getColor(p) {\n"
@@ -84,8 +90,10 @@ static const char FLAMEGRAPH_HEADER[] =
    "\t\treturn '#' + (p[0] + ((p[1] * v) << 16 | (p[2] * v) << 8 | (p[3] * v))).toString(16);\n"
    "\t}\n"
    "\n"
-    "\tfunction f(level, left, width, type, title) {\n"
-    "\t\tlevels[level].push({left: left, width: width, color: getColor(palette[type]), title: title});\n"
+    "\tfunction f(level, left, width, type, title, inln, c1, int) {\n"
+    "\t\tlevels[level].push({left: left, width: width, color: getColor(palette[type]), title: title,\n"
+    "\t\t\tdetails: (int ? ', int=' + int : '') + (c1 ? ', c1=' + c1 : '') + (inln ? ', inln=' + inln : '')\n"
+    "\t\t});\n"
    "\t}\n"
    "\n"
    "\tfunction samples(n) {\n"
@@ -151,12 +159,12 @@ static const char FLAMEGRAPH_HEADER[] =
    "\t\tfunction totalMarked() {\n"
    "\t\t\tlet total = 0;\n"
    "\t\t\tlet left = 0;\n"
-    "\t\t\tfor (let x in marked) {\n"
+    "\t\t\tObject.keys(marked).sort(function(a, b) { return a - b; }).forEach(function(x) {\n"
    "\t\t\t\tif (+x >= left) {\n"
    "\t\t\t\t\ttotal += marked[x];\n"
    "\t\t\t\t\tleft = +x + marked[x];\n"
    "\t\t\t\t}\n"
-    "\t\t\t}\n"
+    "\t\t\t});\n"
    "\t\t\treturn total;\n"
    "\t\t}\n"
    "\n"
@@ -200,7 +208,7 @@ static const char FLAMEGRAPH_HEADER[] =
    "\t\t\t\thl.style.top = ((reverse ? h * 16 : canvasHeight - (h + 1) * 16) + canvas.offsetTop) + 'px';\n"
    "\t\t\t\thl.firstChild.textContent = f.title;\n"
    "\t\t\t\thl.style.display = 'block';\n"
-    "\t\t\t\tcanvas.title = f.title + '\\n(' + samples(f.width) + ', ' + pct(f.width, levels[0][0].width) + '%%)';\n"
+    "\t\t\t\tcanvas.title = f.title + '\\n(' + samples(f.width) + f.details + ', ' + pct(f.width, levels[0][0].width) + '%%)';\n"
    "\t\t\t\tcanvas.style.cursor = 'pointer';\n"
    "\t\t\t\tcanvas.onclick = function() {\n"
    "\t\t\t\t\tif (f != root) {\n"
@@ -295,19 +303,25 @@ static const char TREE_HEADER[] =
    "    background-color: #D9D9D9;\n"
    "}\n"
    ".t0 {\n"
-    "    color: #32c832;\n"
+    "    color: #8eb48e;\n"
    "}\n"
    ".t1 {\n"
-    "    color: #32a5a5;\n"
+    "    color: #30b430;\n"
    "}\n"
    ".t2 {\n"
-    "    color: #be5a00;\n"
+    "    color: #30b4b4;\n"
    "}\n"
    ".t3 {\n"
-    "    color: #afaf32;\n"
+    "    color: #b43030;\n"
    "}\n"
    ".t4 {\n"
-    "    color: #c83232;\n"
+    "    color: #aaaa00;\n"
+    "}\n"
+    ".t5 {\n"
+    "    color: #cc8000;\n"
+    "}\n"
+    ".t6 {\n"
+    "    color: #a3ba66;\n"
    "}\n"
    "ul.tree li > div {\n"
    "    display: inline;\n"
@@ -413,9 +427,9 @@ class StringUtils {
        return len >= suffixlen && s.compare(len - suffixlen, suffixlen, suffix) == 0; 
    }

-    static void replace(std::string& s, char c, const char* replacement) {
-        for (size_t i = 0; (i = s.find(c, i)) != std::string::npos; i++) {
-            s.replace(i, 1, replacement);
+    static void replace(std::string& s, char c, const char* replacement, size_t rlen) {
+        for (size_t i = 0; (i = s.find(c, i)) != std::string::npos; i += rlen) {
+            s.replace(i, 1, replacement, rlen);
        }
    }
 };
@@ -479,7 +493,8 @@ void FlameGraph::dump(std::ostream& out, bool tree) {
        out << TREE_FOOTER;
    } else {
        char buf[sizeof(FLAMEGRAPH_HEADER) + 256];
-        snprintf(buf, sizeof(buf) - 1, FLAMEGRAPH_HEADER, _title, depth * 16, _reverse ? "true" : "false", depth);
+        snprintf(buf, sizeof(buf) - 1, FLAMEGRAPH_HEADER, _title,
+                 std::min(depth * 16, MAX_CANVAS_HEIGHT), _reverse ? "true" : "false", depth);
        out << buf;

        printFrame(out, "all", _root, 0, 0);
@@ -490,10 +505,16 @@ void FlameGraph::dump(std::ostream& out, bool tree) {

 void FlameGraph::printFrame(std::ostream& out, const std::string& name, const Trie& f, int level, u64 x) {
    std::string name_copy = name;
-    int type = frameType(name_copy);
-    StringUtils::replace(name_copy, '\'', "\\'");
+    int type = frameType(name_copy, f);
+    StringUtils::replace(name_copy, '\'', "\\'", 2);

-    snprintf(_buf, sizeof(_buf) - 1, "f(%d,%llu,%llu,%d,'%s')\n", level, x, f._total, type, name_copy.c_str());
+    if (f._inlined | f._c1_compiled | f._interpreted) {
+        snprintf(_buf, sizeof(_buf) - 1, "f(%d,%llu,%llu,%d,'%s',%llu,%llu,%llu)\n",
+                 level, x, f._total, type, name_copy.c_str(), f._inlined, f._c1_compiled, f._interpreted);
+    } else {
+        snprintf(_buf, sizeof(_buf) - 1, "f(%d,%llu,%llu,%d,'%s')\n",
+                 level, x, f._total, type, name_copy.c_str());
+    }
    out << _buf;

    x += f._self;
@@ -517,10 +538,10 @@ void FlameGraph::printTreeFrame(std::ostream& out, const Trie& f, int level) {
        std::string name = subnodes[i]._name;
        const Trie* trie = subnodes[i]._trie;

-        int type = frameType(name);
-        StringUtils::replace(name, '&', "&amp;");
-        StringUtils::replace(name, '<', "&lt;");
-        StringUtils::replace(name, '>', "&gt;");
+        int type = frameType(name, f);
+        StringUtils::replace(name, '&', "&amp;", 5);
+        StringUtils::replace(name, '<', "&lt;", 4);
+        StringUtils::replace(name, '>', "&gt;", 4);

        if (_reverse) {
            snprintf(_buf, sizeof(_buf) - 1,
@@ -550,27 +571,31 @@ void FlameGraph::printTreeFrame(std::ostream& out, const Trie& f, int level) {
    }
 }

-int FlameGraph::frameType(std::string& name) {
+// TODO: Reuse frame type embedded in ASGCT_CallFrame
+int FlameGraph::frameType(std::string& name, const Trie& f) {
+    if (f._inlined * 3 >= f._total) {
+        return FRAME_INLINED;
+    } else if (f._c1_compiled * 2 >= f._total) {
+        return FRAME_C1_COMPILED;
+    } else if (f._interpreted * 2 >= f._total) {
+        return FRAME_INTERPRETED;
+    }
+
    if (StringUtils::endsWith(name, "_[j]", 4)) {
-        // Java compiled frame
        name = name.substr(0, name.length() - 4);
-        return 0;
+        return FRAME_JIT_COMPILED;
    } else if (StringUtils::endsWith(name, "_[i]", 4)) {
-        // Java inlined frame
        name = name.substr(0, name.length() - 4);
-        return 1;
+        return FRAME_INLINED;
    } else if (StringUtils::endsWith(name, "_[k]", 4)) {
-        // Kernel function
        name = name.substr(0, name.length() - 4);
-        return 2;
+        return FRAME_KERNEL;
    } else if (name.find("::") != std::string::npos || name.compare(0, 2, "-[") == 0 || name.compare(0, 2, "+[") == 0) {
-        // C++ function or Objective C method
-        return 3;
-    } else if ((int)name.find('/') > 0 || ((int)name.find('.') > 0 && name[0] >= 'A' && name[0] <= 'Z')) {
-        // Java regular method
-        return 0;
+        return FRAME_CPP;
+    } else if (((int)name.find('/') > 0 && name[0] != '[')
+            || ((int)name.find('.') > 0 && name[0] >= 'A' && name[0] <= 'Z')) {
+        return FRAME_JIT_COMPILED;
    } else {
-        // Other native code
-        return 4;
+        return FRAME_NATIVE;
    }
 }
--- a/src/flameGraph.h
+++ b/src/flameGraph.h
@@ -22,6 +22,7 @@
 #include <iostream>
 #include "arch.h"
 #include "arguments.h"
+#include "vmEntry.h"


 class Trie {
@@ -29,10 +30,11 @@ class Trie {
    std::map<std::string, Trie> _children;
    u64 _total;
    u64 _self;
+    u64 _inlined, _c1_compiled, _interpreted;

-    Trie() : _children(), _total(0), _self(0) {
+    Trie() : _children(), _total(0), _self(0), _inlined(0), _c1_compiled(0), _interpreted(0) {
    }
-    
+
    Trie* addChild(const std::string& key, u64 value) {
        _total += value;
        return &_children[key];
@@ -43,6 +45,15 @@ class Trie {
        _self += value;
    }

+    void addCompilationDetails(int bci, u64 counter) {
+        switch (FrameType::decode(bci)) {
+            case FRAME_INLINED:     _inlined += counter; break;
+            case FRAME_C1_COMPILED: _c1_compiled += counter; break;
+            case FRAME_INTERPRETED: _interpreted += counter; break;
+            default: break;
+        }
+    }
+
    int depth(u64 cutoff) const {
        if (_total < cutoff) {
            return 0;
@@ -71,7 +82,7 @@ class FlameGraph {

    void printFrame(std::ostream& out, const std::string& name, const Trie& f, int level, u64 x);
    void printTreeFrame(std::ostream& out, const Trie& f, int level);
-    int frameType(std::string& name);
+    int frameType(std::string& name, const Trie& f);

  public:
    FlameGraph(const char* title, Counter counter, double minwidth, bool reverse) :
--- a/src/flightRecorder.cpp
+++ b/src/flightRecorder.cpp
--- a/src/flightRecorder.h
+++ b/src/flightRecorder.h
@@ -20,6 +20,7 @@
 #include "arch.h"
 #include "arguments.h"
 #include "event.h"
+#include "log.h"

 class Recording;

@@ -27,19 +28,26 @@ class FlightRecorder {
  private:
    Recording* _rec;

+    Error startMasterRecording(Arguments& args);
+    void stopMasterRecording();
+
  public:
    FlightRecorder() : _rec(NULL) {
    }

    Error start(Arguments& args, bool reset);
    void stop();
+    void flush();
+    bool timerTick(u64 wall_time);

-    bool active() {
+    bool active() const {
        return _rec != NULL;
    }

    void recordEvent(int lock_index, int tid, u32 call_trace_id,
                     int event_type, Event* event, u64 counter);
+
+    void recordLog(LogLevel level, const char* message, size_t len);
 };

 #endif // _FLIGHTRECORDER_H
--- a/src/frameName.cpp
+++ b/src/frameName.cpp
@@ -23,6 +23,11 @@
 #include "vmStructs.h"


+static inline bool isDigit(char c) {
+    return c >= '0' && c <= '9';
+}
+
+
 Matcher::Matcher(const char* pattern) {
    if (pattern[0] == '*') {
        _type = MATCH_ENDS_WITH;
@@ -91,7 +96,7 @@ FrameName::FrameName(Arguments& args, int style, Mutex& thread_names_lock, Threa
    buildFilter(_include, args._buf, args._include);
    buildFilter(_exclude, args._buf, args._exclude);

-    Profiler::_instance.classMap()->collect(_class_names);
+    Profiler::instance()->classMap()->collect(_class_names);
 }

 FrameName::~FrameName() {
@@ -112,17 +117,41 @@ char* FrameName::truncate(char* name, int max_length) {
    return name;
 }

-const char* FrameName::cppDemangle(const char* name) {
-    if (name != NULL && name[0] == '_' && name[1] == 'Z') {
+const char* FrameName::decodeNativeSymbol(const char* name) {
+    const char* lib_name = (_style & STYLE_LIB_NAMES) ? Profiler::instance()->getLibraryName(name) : NULL;
+
+    if (name[0] == '_' && name[1] == 'Z') {
        int status;
        char* demangled = abi::__cxa_demangle(name, NULL, NULL, &status);
        if (demangled != NULL) {
-            strncpy(_buf, demangled, sizeof(_buf) - 1);
+            if (lib_name != NULL) {
+                snprintf(_buf, sizeof(_buf) - 1, "%s`%s", lib_name, demangled);
+            } else {
+                strncpy(_buf, demangled, sizeof(_buf) - 1);
+            }
            free(demangled);
            return _buf;
        }
    }
-    return name;
+
+    if (lib_name != NULL) {
+        snprintf(_buf, sizeof(_buf) - 1, "%s`%s", lib_name, name);
+        return _buf;
+    } else {
+        return name;
+    }
+}
+
+const char* FrameName::typeSuffix(FrameTypeId type) {
+    if (_style & STYLE_ANNOTATE) {
+        switch (type) {
+            case FRAME_JIT_COMPILED: return "_[j]";
+            case FRAME_INLINED:      return "_[i]";
+            case FRAME_C1_COMPILED:  return "_[1]";
+            default:                 return NULL;
+        }
+    }
+    return NULL;
 }

 char* FrameName::javaMethodName(jmethodID method) {
@@ -143,7 +172,6 @@ char* FrameName::javaMethodName(jmethodID method) {
        strcat(result, ".");
        strcat(result, method_name);
        if (_style & STYLE_SIGNATURES) strcat(result, truncate(method_sig, 255));
-        if (_style & STYLE_ANNOTATE) strcat(result, "_[j]");
    } else {
        snprintf(_buf, sizeof(_buf) - 1, "[jvmtiError %d]", err);
        result = _buf;
@@ -191,13 +219,13 @@ char* FrameName::javaClassName(const char* symbol, int length, int style) {

    if (style & STYLE_SIMPLE) {
        for (char* s = result; *s; s++) {
-            if (*s == '/') result = s + 1;
+            if (*s == '/' && !isDigit(s[1])) result = s + 1;
        }
    }

    if (style & STYLE_DOTTED) {
        for (char* s = result; *s; s++) {
-            if (*s == '/') *s = '.';
+            if (*s == '/' && !isDigit(s[1])) *s = '.';
        }
    }

@@ -211,7 +239,7 @@ const char* FrameName::name(ASGCT_CallFrame& frame, bool for_matching) {

    switch (frame.bci) {
        case BCI_NATIVE_FRAME:
-            return cppDemangle((const char*)frame.method_id);
+            return decodeNativeSymbol((const char*)frame.method_id);

        case BCI_ALLOC:
        case BCI_ALLOC_OUTSIDE_TLAB:
@@ -245,14 +273,20 @@ const char* FrameName::name(ASGCT_CallFrame& frame, bool for_matching) {
        }

        default: {
+            const char* type_suffix = typeSuffix(FrameType::decode(frame.bci));
+
            JMethodCache::iterator it = _cache.lower_bound(frame.method_id);
            if (it != _cache.end() && it->first == frame.method_id) {
+                if (type_suffix != NULL) {
+                    snprintf(_buf, sizeof(_buf) - 1, "%s%s", it->second.c_str(), type_suffix);
+                    return _buf;
+                }
                return it->second.c_str();
            }

-            const char* newName = javaMethodName(frame.method_id);
+            char* newName = javaMethodName(frame.method_id);
            _cache.insert(it, JMethodCache::value_type(frame.method_id, newName));
-            return newName;
+            return type_suffix != NULL ? strcat(newName, type_suffix) : newName;
        }
    }
 }
--- a/src/frameName.h
+++ b/src/frameName.h
@@ -75,7 +75,8 @@ class FrameName {

    void buildFilter(std::vector<Matcher>& vector, const char* base, int offset);
    char* truncate(char* name, int max_length);
-    const char* cppDemangle(const char* name);
+    const char* decodeNativeSymbol(const char* name);
+    const char* typeSuffix(FrameTypeId type);
    char* javaMethodName(jmethodID method);
    char* javaClassName(const char* symbol, int length, int style);

--- a/src/helper/one/profiler/Instrument.class.h
+++ b/src/helper/one/profiler/Instrument.class.h
@@ -0,0 +1 @@
+202,254,186,190,0,0,0,50,0,11,10,0,3,0,8,7,0,9,7,0,10,1,0,6,60,105,110,105,116,62,1,0,3,40,41,86,1,0,4,67,111,100,101,1,0,12,114,101,99,111,114,100,83,97,109,112,108,101,12,0,4,0,5,1,0,23,111,110,101,47,112,114,111,102,105,108,101,114,47,73,110,115,116,114,117,109,101,110,116,1,0,16,106,97,118,97,47,108,97,110,103,47,79,98,106,101,99,116,0,33,0,2,0,3,0,0,0,0,0,2,0,2,0,4,0,5,0,1,0,6,0,0,0,17,0,1,0,1,0,0,0,5,42,183,0,1,177,0,0,0,0,1,9,0,7,0,5,0,0,0,0,
--- a/src/helper/one/profiler/Instrument.java
+++ b/src/helper/one/profiler/Instrument.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.profiler;
+
+/**
+ * Instrumentation helper for Java method profiling.
+ */
+public class Instrument {
+
+    private Instrument() {
+    }
+
+    public static native void recordSample();
+}
--- a/src/helper/one/profiler/JfrSync.class.h
+++ b/src/helper/one/profiler/JfrSync.class.h
--- a/src/helper/one/profiler/JfrSync.java
+++ b/src/helper/one/profiler/JfrSync.java
@@ -0,0 +1,101 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.profiler;
+
+import jdk.jfr.Configuration;
+import jdk.jfr.FlightRecorder;
+import jdk.jfr.FlightRecorderListener;
+import jdk.jfr.Recording;
+import jdk.jfr.RecordingState;
+
+import java.io.IOException;
+import java.nio.file.NoSuchFileException;
+import java.nio.file.Paths;
+import java.text.ParseException;
+
+/**
+ * Synchronize async-profiler recording with an existing JFR recording.
+ */
+class JfrSync implements FlightRecorderListener {
+    private static volatile Recording masterRecording;
+
+    private JfrSync() {
+    }
+
+    static {
+        FlightRecorder.addListener(new JfrSync());
+    }
+
+    @Override
+    public void recordingStateChanged(Recording recording) {
+        if (recording == masterRecording && recording.getState() == RecordingState.STOPPED) {
+            masterRecording = null;
+            stopProfiler();
+        }
+    }
+
+    public static void start(String fileName, String settings, int eventMask) throws IOException, ParseException {
+        Configuration config;
+        try {
+            config = Configuration.getConfiguration(settings);
+        } catch (NoSuchFileException e) {
+            config = Configuration.create(Paths.get(settings));
+        }
+
+        Recording recording = new Recording(config);
+        masterRecording = recording;
+
+        disableBuiltinEvents(recording, eventMask);
+
+        recording.setDestination(Paths.get(fileName));
+        recording.setToDisk(true);
+        recording.setDumpOnExit(true);
+        recording.start();
+    }
+
+    public static void stop() {
+        Recording recording = masterRecording;
+        if (recording != null) {
+            // Disable state change notification before stopping
+            masterRecording = null;
+            recording.stop();
+        }
+    }
+
+    private static void disableBuiltinEvents(Recording recording, int eventMask) {
+        if ((eventMask & 1) != 0) {
+            recording.disable("jdk.ExecutionSample");
+            recording.disable("jdk.NativeMethodSample");
+        }
+        if ((eventMask & 2) != 0) {
+            recording.disable("jdk.ObjectAllocationInNewTLAB");
+            recording.disable("jdk.ObjectAllocationOutsideTLAB");
+            recording.disable("jdk.ObjectAllocationSample");
+        }
+        if ((eventMask & 4) != 0) {
+            recording.disable("jdk.JavaMonitorEnter");
+            recording.disable("jdk.ThreadPark");
+        }
+    }
+
+    private static native void stopProfiler();
+
+    // JNI helper
+    static Integer box(int n) {
+        return n;
+    }
+}
--- a/src/helper/one/profiler/Server.class.h
+++ b/src/helper/one/profiler/Server.class.h
--- a/src/helper/one/profiler/Server.java
+++ b/src/helper/one/profiler/Server.java
@@ -0,0 +1,111 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package one.profiler;
+
+import com.sun.net.httpserver.HttpExchange;
+import com.sun.net.httpserver.HttpHandler;
+import com.sun.net.httpserver.HttpServer;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.URI;
+import java.nio.charset.StandardCharsets;
+import java.util.concurrent.Executor;
+import java.util.concurrent.atomic.AtomicInteger;
+
+class Server extends Thread implements Executor, HttpHandler {
+    private static final String[] COMMANDS = "start,resume,stop,dump,check,status,list,version".split(",");
+
+    private final HttpServer server;
+    private final AtomicInteger threadNum = new AtomicInteger();
+
+    private Server(String address) throws IOException {
+        super("Async-profiler Server");
+        setDaemon(true);
+
+        int p = address.lastIndexOf(':');
+        InetSocketAddress socketAddress = p >= 0
+                ? new InetSocketAddress(address.substring(0, p), Integer.parseInt(address.substring(p + 1)))
+                : new InetSocketAddress(Integer.parseInt(address));
+
+        server = HttpServer.create(socketAddress, 0);
+        server.createContext("/", this);
+        server.setExecutor(this);
+    }
+
+    public static void start(String address) throws IOException {
+        new Server(address).start();
+    }
+
+    @Override
+    public void run() {
+        server.start();
+    }
+
+    @Override
+    public void execute(Runnable command) {
+        Thread t = new Thread(command, "Async-profiler Request #" + threadNum.incrementAndGet());
+        t.setDaemon(false);
+        t.start();
+    }
+
+    @Override
+    public void handle(HttpExchange exchange) throws IOException {
+        try {
+            String command = getCommand(exchange.getRequestURI());
+            if (command == null) {
+                sendResponse(exchange, 404, "Unknown command");
+            } else {
+                String response = execute0(command);
+                sendResponse(exchange, 200, response);
+            }
+        } catch (IllegalArgumentException e) {
+            sendResponse(exchange, 400, e.getMessage());
+        } catch (Exception e) {
+            sendResponse(exchange, 500, e.getMessage());
+        } finally {
+            exchange.close();
+        }
+    }
+
+    private String getCommand(URI uri) {
+        String path = uri.getPath();
+        if (path.startsWith("/")) {
+            if ((path = path.substring(1)).isEmpty()) {
+                return "version=full";
+            }
+            for (String command : COMMANDS) {
+                if (path.startsWith(command)) {
+                    String query = uri.getQuery();
+                    return query == null ? path : path + ',' + query.replace('&', ',');
+                }
+            }
+        }
+        return null;
+    }
+
+    private void sendResponse(HttpExchange exchange, int code, String body) throws IOException {
+        String contentType = body.startsWith("<!DOCTYPE html>") ? "text/html; charset=utf-8" : "text/plain";
+        exchange.getResponseHeaders().add("Content-Type", contentType);
+
+        byte[] bodyBytes = body.getBytes(StandardCharsets.UTF_8);
+        exchange.sendResponseHeaders(code, bodyBytes.length);
+        exchange.getResponseBody().write(bodyBytes);
+    }
+
+    private native String execute0(String command) throws IllegalArgumentException, IllegalStateException, IOException;
+}
--- a/src/instrument.cpp
+++ b/src/instrument.cpp
@@ -24,28 +24,9 @@
 #include "instrument.h"


-// A class with a single native recordSample() method
-static const char INSTRUMENT_CLASS[] =
-    "\xCA\xFE\xBA\xBE"                     // magic
-    "\x00\x00\x00\x32"                     // version: 50
-    "\x00\x07"                             // constant_pool_count: 7
-    "\x07\x00\x02"                         //   #1 = CONSTANT_Class: #2
-    "\x01\x00\x17one/profiler/Instrument"  //   #2 = CONSTANT_Utf8: "one/profiler/Instrument"
-    "\x07\x00\x04"                         //   #3 = CONSTANT_Class: #4
-    "\x01\x00\x10java/lang/Object"         //   #4 = CONSTANT_Utf8: "java/lang/Object"
-    "\x01\x00\x0CrecordSample"             //   #5 = CONSTANT_Utf8: "recordSample"
-    "\x01\x00\x03()V"                      //   #6 = CONSTANT_Utf8: "()V"
-    "\x00\x21"                             // access_flags: public super
-    "\x00\x01"                             // this_class: #1
-    "\x00\x03"                             // super_class: #3
-    "\x00\x00"                             // interfaces_count: 0
-    "\x00\x00"                             // fields_count: 0
-    "\x00\x01"                             // methods_count: 1
-    "\x01\x09"                             //   access_flags: public static native
-    "\x00\x05"                             //   name_index: #5
-    "\x00\x06"                             //   descriptor_index: #6
-    "\x00\x00"                             //   attributes_count: 0
-    "\x00";                                // attributes_count: 0
+static const unsigned char INSTRUMENT_CLASS[] = {
+#include "helper/one/profiler/Instrument.class.h"
+};


 enum ConstantTag {
@@ -255,6 +236,7 @@ class BytecodeRewriter {
    void rewriteCode();
    void rewriteBytecodeTable(int data_len);
    void rewriteStackMapTable();
+    void rewriteVerificationTypeInfo();
    void rewriteAttributes(Scope scope);
    void rewriteMembers(Scope scope);
    bool rewriteClass();
@@ -315,7 +297,7 @@ void BytecodeRewriter::rewriteCode() {
    put32(code_length + EXTRA_BYTECODES);

    // invokestatic "one/profiler/Instrument.recordSample()V"
-    // nop after invoke helps to prepend StackMapTable without rewriting
+    // nop ensures that tableswitch/lookupswitch needs no realignment
    put8(0xb8);
    put16(_cpool_len);
    put8(0);
@@ -366,7 +348,53 @@ void BytecodeRewriter::rewriteStackMapTable() {

    // Prepend same_frame
    put8(EXTRA_BYTECODES - 1);
-    put(get(attribute_length - 2), attribute_length - 2);
+
+    for (int i = 0; i < number_of_entries; i++) {
+        u8 frame_type = get8();
+        put8(frame_type);
+
+        if (frame_type <= 63) {
+            // same_frame
+        } else if (frame_type <= 127) {
+            // same_locals_1_stack_item_frame
+            rewriteVerificationTypeInfo();
+        } else if (frame_type == 247) {
+            // same_locals_1_stack_item_frame_extended
+            put16(get16());
+            rewriteVerificationTypeInfo();
+        } else if (frame_type <= 251) {
+            // chop_frame or same_frame_extended
+            put16(get16());
+        } else if (frame_type <= 254) {
+            // append_frame
+            put16(get16());
+            for (int j = 0; j < frame_type - 251; j++) {
+                rewriteVerificationTypeInfo();
+            }
+        } else {
+            // full_frame
+            put16(get16());
+            u16 number_of_locals = get16();
+            put16(number_of_locals);
+            for (int j = 0; j < number_of_locals; j++) {
+                rewriteVerificationTypeInfo();
+            }
+            u16 number_of_stack_items = get16();
+            put16(number_of_stack_items);
+            for (int j = 0; j < number_of_stack_items; j++) {
+                rewriteVerificationTypeInfo();
+            }
+        }
+    }
+}
+
+void BytecodeRewriter::rewriteVerificationTypeInfo() {
+    u8 tag = get8();
+    put8(tag);
+    if (tag >= 7) {
+        // Adjust ITEM_Uninitialized offset
+        put16(tag == 8 ? EXTRA_BYTECODES + get16() : get16());
+    }
 }

 void BytecodeRewriter::rewriteAttributes(Scope scope) {
@@ -489,7 +517,7 @@ Error Instrument::check(Arguments& args) {

        jclass cls = jni->DefineClass(NULL, NULL, (const jbyte*)INSTRUMENT_CLASS, sizeof(INSTRUMENT_CLASS));
        if (cls == NULL || jni->RegisterNatives(cls, &native_method, 1) != 0) {
-            jni->ExceptionClear();
+            jni->ExceptionDescribe();
            return Error("Could not load Instrument class");
        }

@@ -509,7 +537,7 @@ Error Instrument::start(Arguments& args) {
        return Error("interval must be positive");
    }

-    setupTargetClassAndMethod(args._event_desc);
+    setupTargetClassAndMethod(args._event);
    _interval = args._interval ? args._interval : 1;
    _calls = 0;
    _running = true;
@@ -588,6 +616,6 @@ void JNICALL Instrument::recordSample(JNIEnv* jni, jobject unused) {

    if (_interval <= 1 || ((atomicInc(_calls) + 1) % _interval) == 0) {
        ExecutionEvent event;
-        Profiler::_instance.recordSample(NULL, _interval, BCI_INSTRUMENT, &event);
+        Profiler::instance()->recordSample(NULL, _interval, BCI_INSTRUMENT, &event);
    }
 }
--- a/src/instrument.h
+++ b/src/instrument.h
@@ -30,18 +30,14 @@ class Instrument : public Engine {
    static volatile bool _running;

  public:
-    const char* name() {
-        return "instrument";
+    const char* title() {
+        return "Java method profile";
    }

    const char* units() {
        return "calls";
    }

-    CStack cstack() {
-        return CSTACK_NO;
-    }
-
    Error check(Arguments& args);
    Error start(Arguments& args);
    void stop();
--- a/src/itimer.cpp
+++ b/src/itimer.cpp
@@ -16,18 +16,32 @@

 #include <sys/time.h>
 #include "itimer.h"
+#include "j9StackTraces.h"
 #include "os.h"
 #include "profiler.h"
+#include "stackWalker.h"


 long ITimer::_interval;
+CStack ITimer::_cstack;


 void ITimer::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
    if (!_enabled) return;

    ExecutionEvent event;
-    Profiler::_instance.recordSample(ucontext, _interval, 0, &event);
+    Profiler::instance()->recordSample(ucontext, _interval, 0, &event);
+}
+
+void ITimer::signalHandlerJ9(int signo, siginfo_t* siginfo, void* ucontext) {
+    if (!_enabled) return;
+
+    J9StackTraceNotification notif;
+    StackContext java_ctx;
+    notif.num_frames = _cstack == CSTACK_NO ? 0 : _cstack == CSTACK_DWARF
+        ? StackWalker::walkDwarf(ucontext, notif.addr, MAX_J9_NATIVE_FRAMES, &java_ctx)
+        : StackWalker::walkFP(ucontext, notif.addr, MAX_J9_NATIVE_FRAMES, &java_ctx);
+    J9StackTraces::checkpoint(_interval, &notif);
 }

 Error ITimer::check(Arguments& args) {
@@ -49,11 +63,21 @@ Error ITimer::start(Arguments& args) {
        return Error("interval must be positive");
    }
    _interval = args._interval ? args._interval : DEFAULT_INTERVAL;
+    _cstack = args._cstack;

-    OS::installSignalHandler(SIGPROF, signalHandler);
+    if (VM::isOpenJ9()) {
+        if (_cstack == CSTACK_DEFAULT) _cstack = CSTACK_DWARF;
+        OS::installSignalHandler(SIGPROF, signalHandlerJ9);
+        Error error = J9StackTraces::start(args);
+        if (error) {
+            return error;
+        }
+    } else {
+        OS::installSignalHandler(SIGPROF, signalHandler);
+    }

-    long sec = _interval / 1000000000;
-    long usec = (_interval % 1000000000) / 1000;
+    time_t sec = _interval / 1000000000;
+    suseconds_t usec = (_interval % 1000000000) / 1000;
    struct itimerval tv = {{sec, usec}, {sec, usec}};
    
    if (setitimer(ITIMER_PROF, &tv, NULL) != 0) {
@@ -66,4 +90,6 @@ Error ITimer::start(Arguments& args) {
 void ITimer::stop() {
    struct itimerval tv = {{0, 0}, {0, 0}};
    setitimer(ITIMER_PROF, &tv, NULL);
+
+    J9StackTraces::stop();
 }
--- a/src/itimer.h
+++ b/src/itimer.h
@@ -24,12 +24,14 @@
 class ITimer : public Engine {
  private:
    static long _interval;
+    static CStack _cstack;

    static void signalHandler(int signo, siginfo_t* siginfo, void* ucontext);
+    static void signalHandlerJ9(int signo, siginfo_t* siginfo, void* ucontext);

  public:
-    const char* name() {
-        return "itimer";
+    const char* title() {
+        return "CPU profile";
    }

    const char* units() {
--- a/src/j9Ext.cpp
+++ b/src/j9Ext.cpp
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "j9Ext.h"
+#include "j9ObjectSampler.h"
+#include <string.h>
+
+
+jvmtiEnv* J9Ext::_jvmti;
+
+void* (*J9Ext::_j9thread_self)() = NULL;
+
+jvmtiExtensionFunction J9Ext::_GetOSThreadID = NULL;
+jvmtiExtensionFunction J9Ext::_GetJ9vmThread = NULL;
+jvmtiExtensionFunction J9Ext::_GetStackTraceExtended = NULL;
+jvmtiExtensionFunction J9Ext::_GetAllStackTracesExtended = NULL;
+
+int J9Ext::InstrumentableObjectAlloc_id = -1;
+
+
+// Look for OpenJ9-specific JVM TI extension
+bool J9Ext::initialize(jvmtiEnv* jvmti, const void* j9thread_self) {
+    _jvmti = jvmti;
+    _j9thread_self = (void* (*)())j9thread_self;
+
+    jint ext_count;
+    jvmtiExtensionFunctionInfo* ext_functions;
+    if (jvmti->GetExtensionFunctions(&ext_count, &ext_functions) == 0) {
+        for (int i = 0; i < ext_count; i++) {
+            if (strcmp(ext_functions[i].id, "com.ibm.GetOSThreadID") == 0) {
+                _GetOSThreadID = ext_functions[i].func;
+            } else if (strcmp(ext_functions[i].id, "com.ibm.GetJ9vmThread") == 0) {
+                _GetJ9vmThread = ext_functions[i].func;
+            } else if (strcmp(ext_functions[i].id, "com.ibm.GetStackTraceExtended") == 0) {
+                _GetStackTraceExtended = ext_functions[i].func;
+            } else if (strcmp(ext_functions[i].id, "com.ibm.GetAllStackTracesExtended") == 0) {
+                _GetAllStackTracesExtended = ext_functions[i].func;
+            }
+        }
+       jvmti->Deallocate((unsigned char*)ext_functions);
+    }
+
+    jvmtiExtensionEventInfo* ext_events;
+    if (jvmti->GetExtensionEvents(&ext_count, &ext_events) == 0) {
+        for (int i = 0; i < ext_count; i++) {
+            if (strcmp(ext_events[i].id, "com.ibm.InstrumentableObjectAlloc") == 0) {
+                InstrumentableObjectAlloc_id = ext_events[i].extension_event_index;
+                // If we don't set a callback now, we won't be able to enable it later in runtime
+                jvmti->SetExtensionEventCallback(InstrumentableObjectAlloc_id, (jvmtiExtensionEvent)J9ObjectSampler::JavaObjectAlloc);
+                jvmti->SetExtensionEventCallback(InstrumentableObjectAlloc_id, NULL);
+                break;
+            }
+        }
+       jvmti->Deallocate((unsigned char*)ext_events);
+    }
+
+    return _GetOSThreadID != NULL && _GetStackTraceExtended != NULL && _GetAllStackTracesExtended != NULL;
+}
--- a/src/j9Ext.h
+++ b/src/j9Ext.h
@@ -0,0 +1,91 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _J9EXT_H
+#define _J9EXT_H
+
+#include <jvmti.h>
+
+
+#define JVMTI_EXT(f, ...)  ((jvmtiError (*)(jvmtiEnv*, __VA_ARGS__))f)
+
+struct jvmtiFrameInfoExtended {
+    jmethodID method;
+    jlocation location;
+    jlocation machinepc;
+    jint type;
+    void* native_frame_address;
+};
+
+struct jvmtiStackInfoExtended {
+    jthread thread;
+    jint state;
+    jvmtiFrameInfoExtended* frame_buffer;
+    jint frame_count;
+};
+
+enum {
+    SHOW_COMPILED_FRAMES = 4,
+    SHOW_INLINED_FRAMES = 8
+};
+
+
+class J9Ext {
+  private:
+    static jvmtiEnv* _jvmti;
+
+    static void* (*_j9thread_self)();
+
+    static jvmtiExtensionFunction _GetOSThreadID;
+    static jvmtiExtensionFunction _GetJ9vmThread;
+    static jvmtiExtensionFunction _GetStackTraceExtended;
+    static jvmtiExtensionFunction _GetAllStackTracesExtended;
+
+  public:
+    static bool initialize(jvmtiEnv* jvmti, const void* j9thread_self);
+
+    static int GetOSThreadID(jthread thread) {
+        jlong thread_id;
+        return JVMTI_EXT(_GetOSThreadID, jthread, jlong*)(_jvmti, thread, &thread_id) == 0 ? (int)thread_id : -1;
+    }
+
+    static JNIEnv* GetJ9vmThread(jthread thread) {
+        JNIEnv* result;
+        return JVMTI_EXT(_GetJ9vmThread, jthread, JNIEnv**)(_jvmti, thread, &result) == 0 ? result : NULL;
+    }
+
+    static jvmtiError GetStackTraceExtended(jthread thread, jint start_depth, jint max_frame_count,
+                                            void* frame_buffer, jint* count_ptr) {
+        return JVMTI_EXT(_GetStackTraceExtended, jint, jthread, jint, jint, void*, jint*)(
+            _jvmti, SHOW_COMPILED_FRAMES | SHOW_INLINED_FRAMES,
+            thread, start_depth, max_frame_count, frame_buffer, count_ptr);
+    }
+
+    static jvmtiError GetAllStackTracesExtended(jint max_frame_count, void** stack_info_ptr, jint* thread_count_ptr) {
+        return JVMTI_EXT(_GetAllStackTracesExtended, jint, jint, void**, jint*)(
+            _jvmti, SHOW_COMPILED_FRAMES | SHOW_INLINED_FRAMES,
+            max_frame_count, stack_info_ptr, thread_count_ptr);
+    }
+
+    static void* j9thread_self() {
+        return _j9thread_self != NULL ? _j9thread_self() : NULL;
+    }
+
+    static int InstrumentableObjectAlloc_id;
+};
+
+
+#endif // _J9EXT_H
--- a/src/j9ObjectSampler.cpp
+++ b/src/j9ObjectSampler.cpp
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "j9ObjectSampler.h"
+#include "j9Ext.h"
+#include "vmEntry.h"
+
+
+void J9ObjectSampler::JavaObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                      jobject object, jclass object_klass, jlong size) {
+    if (_enabled && updateCounter(_allocated_bytes, size, _interval)) {
+        recordAllocation(jvmti, BCI_ALLOC, object_klass, size);
+    }
+}
+
+void J9ObjectSampler::VMObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                    jobject object, jclass object_klass, jlong size) {
+    if (_enabled && updateCounter(_allocated_bytes, size, _interval)) {
+        recordAllocation(jvmti, BCI_ALLOC_OUTSIDE_TLAB, object_klass, size);
+    }
+}
+
+Error J9ObjectSampler::check(Arguments& args) {
+    if (J9Ext::InstrumentableObjectAlloc_id < 0) {
+        return Error("InstrumentableObjectAlloc is not supported on this JVM");
+    }
+    return Error::OK;
+}
+
+Error J9ObjectSampler::start(Arguments& args) {
+    Error error = check(args);
+    if (error) {
+        return error;
+    }
+
+    _interval = args._alloc > 0 ? args._alloc : DEFAULT_ALLOC_INTERVAL;
+    _allocated_bytes = 0;
+
+    jvmtiEnv* jvmti = VM::jvmti();
+    if (jvmti->SetExtensionEventCallback(J9Ext::InstrumentableObjectAlloc_id, (jvmtiExtensionEvent)JavaObjectAlloc) != 0) {
+        return Error("Could not enable InstrumentableObjectAlloc callback");
+    }
+    jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_VM_OBJECT_ALLOC, NULL);
+
+    return Error::OK;
+}
+
+void J9ObjectSampler::stop() {
+    jvmtiEnv* jvmti = VM::jvmti();
+    jvmti->SetEventNotificationMode(JVMTI_DISABLE, JVMTI_EVENT_VM_OBJECT_ALLOC, NULL);
+    jvmti->SetExtensionEventCallback(J9Ext::InstrumentableObjectAlloc_id, NULL);
+}
--- a/src/j9ObjectSampler.h
+++ b/src/j9ObjectSampler.h
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _J9OBJECTSAMPLER_H
+#define _J9OBJECTSAMPLER_H
+
+#include "objectSampler.h"
+
+
+class J9ObjectSampler : public ObjectSampler {
+  public:
+    Error check(Arguments& args);
+    Error start(Arguments& args);
+    void stop();
+
+    static void JNICALL JavaObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                        jobject object, jclass object_klass, jlong size);
+
+    static void JNICALL VMObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                      jobject object, jclass object_klass, jlong size);
+};
+
+#endif // _J9OBJECTSAMPLER_H
--- a/src/j9StackTraces.cpp
+++ b/src/j9StackTraces.cpp
@@ -0,0 +1,186 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include <sys/time.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <map>
+#include "j9StackTraces.h"
+#include "j9Ext.h"
+#include "profiler.h"
+#include "perfEvents.h"
+
+
+enum {
+    J9_STOPPED = 0x40,
+    J9_HALT_THREAD_INSPECTION = 0x8000
+};
+
+class J9VMThread {
+  private:
+    uintptr_t _unused1[10];
+    uintptr_t _overflow_mark;
+    uintptr_t _unused2[8];
+    uintptr_t _flags;
+
+  public:
+    uintptr_t getAndSetFlag(uintptr_t flag) {
+        return __sync_fetch_and_or(&_flags, flag);
+    }
+
+    void clearFlag(uintptr_t flag) {
+        __sync_fetch_and_and(&_flags, ~flag);
+    }
+
+    void setOverflowMark() {
+        __atomic_store_n(&_overflow_mark, (uintptr_t)-1, __ATOMIC_RELEASE);
+    }
+};
+
+
+pthread_t J9StackTraces::_thread = 0;
+int J9StackTraces::_max_stack_depth;
+int J9StackTraces::_pipe[2];
+
+static JNIEnv* _self_env = NULL;
+
+
+Error J9StackTraces::start(Arguments& args) {
+    _max_stack_depth = args._jstackdepth; 
+
+    if (pipe(_pipe) != 0) {
+        return Error("Failed to create pipe");
+    }
+    fcntl(_pipe[1], F_SETFL, O_NONBLOCK);
+
+    if (pthread_create(&_thread, NULL, threadEntry, NULL) != 0) {
+        close(_pipe[0]);
+        close(_pipe[1]);
+        return Error("Unable to create sampler thread");
+    }
+
+    return Error::OK;
+}
+
+void J9StackTraces::stop() {
+    if (_thread != 0) {
+        close(_pipe[1]);
+        pthread_join(_thread, NULL);
+        close(_pipe[0]);
+        _thread = 0;
+    }
+}
+
+void J9StackTraces::timerLoop() {
+    JNIEnv* jni = VM::attachThread("Async-profiler Sampler");
+    __atomic_store_n(&_self_env, jni, __ATOMIC_RELEASE);
+
+    jni->PushLocalFrame(64);
+
+    jvmtiEnv* jvmti = VM::jvmti();
+    char notification_buf[65536];
+    std::map<void*, jthread> known_threads;
+
+    int max_frames = _max_stack_depth + MAX_J9_NATIVE_FRAMES + RESERVED_FRAMES;
+    ASGCT_CallFrame* frames = (ASGCT_CallFrame*)malloc(max_frames * sizeof(ASGCT_CallFrame));
+    jvmtiFrameInfoExtended* jvmti_frames = (jvmtiFrameInfoExtended*)malloc(max_frames * sizeof(jvmtiFrameInfoExtended));
+
+    while (true) {
+        ssize_t bytes = read(_pipe[0], notification_buf, sizeof(notification_buf));
+        if (bytes <= 0) {
+            if (bytes < 0 && errno == EAGAIN) {
+                continue;
+            }
+            break;
+        }
+
+        ssize_t ptr = 0;
+        while (ptr < bytes) {
+            J9StackTraceNotification* notif = (J9StackTraceNotification*)(notification_buf + ptr);
+
+            jthread thread = known_threads[notif->env];
+            jint num_jvmti_frames;
+            if (thread == NULL || J9Ext::GetStackTraceExtended(thread, 0, _max_stack_depth, jvmti_frames, &num_jvmti_frames) != 0) {
+                jni->PopLocalFrame(NULL);
+                jni->PushLocalFrame(64);
+
+                jint thread_count;
+                jthread* threads;
+                if (jvmti->GetAllThreads(&thread_count, &threads) == 0) {
+                    known_threads.clear();
+                    for (jint i = 0; i < thread_count; i++) {
+                        known_threads[J9Ext::GetJ9vmThread(threads[i])] = threads[i];
+                    }
+                    jvmti->Deallocate((unsigned char*)threads);
+                }
+
+                if ((thread = known_threads[notif->env]) == NULL ||
+                    J9Ext::GetStackTraceExtended(thread, 0, _max_stack_depth, jvmti_frames, &num_jvmti_frames) != 0) {
+                    continue;
+                }
+            }
+
+            int num_frames = Profiler::instance()->convertNativeTrace(notif->num_frames, notif->addr, frames);
+
+            for (int j = 0; j < num_jvmti_frames; j++) {
+                frames[num_frames].method_id = jvmti_frames[j].method;
+                frames[num_frames].bci = FrameType::encode(jvmti_frames[j].type, jvmti_frames[j].location);
+                num_frames++;
+            }
+
+            int tid = J9Ext::GetOSThreadID(thread);
+            ExecutionEvent event;
+            Profiler::instance()->recordExternalSample(notif->counter, &event, tid, num_frames, frames);
+
+            ptr += notif->size();
+        }
+    }
+
+    free(jvmti_frames);
+    free(frames);
+
+    __atomic_store_n(&_self_env, NULL, __ATOMIC_RELEASE);
+    VM::detachThread();
+}
+
+void J9StackTraces::checkpoint(u64 counter, J9StackTraceNotification* notif) {
+    JNIEnv* self_env = __atomic_load_n(&_self_env, __ATOMIC_ACQUIRE);
+    if (self_env == NULL) {
+        // Sampler thread is not ready
+        return;
+    }
+
+    JNIEnv* env = VM::jni();
+    if (env != NULL && env != self_env) {
+        J9VMThread* vm_thread = (J9VMThread*)env;
+        uintptr_t flags = vm_thread->getAndSetFlag(J9_HALT_THREAD_INSPECTION);
+        if (flags & J9_HALT_THREAD_INSPECTION) {
+            // Thread is already scheduled for inspection, no need to notify again
+            return;
+        } else if (!(flags & J9_STOPPED)) {
+            vm_thread->setOverflowMark();
+            notif->env = env;
+            notif->counter = counter;
+            if (write(_pipe[1], notif, notif->size()) > 0) {
+                return;
+            }
+        }
+        // Something went wrong - rollback
+        vm_thread->clearFlag(J9_HALT_THREAD_INSPECTION);
+    }
+}
--- a/src/j9StackTraces.h
+++ b/src/j9StackTraces.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _J9STACKTRACES_H
+#define _J9STACKTRACES_H
+
+#include <pthread.h>
+#include "arch.h"
+#include "arguments.h"
+
+
+const int MAX_J9_NATIVE_FRAMES = 128;
+
+struct J9StackTraceNotification {
+    void* env;
+    u64 counter;
+    int num_frames;
+    int reserved;
+    const void* addr[MAX_J9_NATIVE_FRAMES];
+
+    size_t size() {
+        return sizeof(*this) - sizeof(this->addr) + num_frames * sizeof(const void*);
+    }
+};
+
+
+class J9StackTraces {
+  private:
+    static pthread_t _thread;
+    static int _max_stack_depth;
+    static int _pipe[2];
+
+    static void* threadEntry(void* unused) {
+        timerLoop();
+        return NULL;
+    }
+
+    static void timerLoop();
+
+  public:
+    static Error start(Arguments& args);
+    static void stop();
+
+    static void checkpoint(u64 counter, J9StackTraceNotification* notif);
+};
+
+#endif // _J9STACKTRACES_H
--- a/src/j9WallClock.cpp
+++ b/src/j9WallClock.cpp
@@ -0,0 +1,86 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include "j9WallClock.h"
+#include "j9Ext.h"
+#include "profiler.h"
+
+
+long J9WallClock::_interval;
+
+Error J9WallClock::start(Arguments& args) {
+    _interval = args._interval ? args._interval : DEFAULT_INTERVAL * 5;
+    _max_stack_depth = args._jstackdepth;
+
+    _running = true;
+
+    if (pthread_create(&_thread, NULL, threadEntry, this) != 0) {
+        return Error("Unable to create timer thread");
+    }
+
+    return Error::OK;
+}
+
+void J9WallClock::stop() {
+    _running = false;
+    pthread_kill(_thread, WAKEUP_SIGNAL);
+    pthread_join(_thread, NULL);
+}
+
+void J9WallClock::timerLoop() {
+    JNIEnv* jni = VM::attachThread("Async-profiler Sampler");
+    jvmtiEnv* jvmti = VM::jvmti();
+
+    int max_frames = _max_stack_depth + MAX_NATIVE_FRAMES + RESERVED_FRAMES;
+    ASGCT_CallFrame* frames = (ASGCT_CallFrame*)malloc(max_frames * sizeof(ASGCT_CallFrame));
+
+    while (_running) {
+        if (!_enabled) {
+            OS::sleep(_interval);
+            continue;
+        }
+
+        jni->PushLocalFrame(64);
+
+        jvmtiStackInfoExtended* stack_infos;
+        jint thread_count;
+        if (J9Ext::GetAllStackTracesExtended(_max_stack_depth, (void**)&stack_infos, &thread_count) == 0) {
+            for (int i = 0; i < thread_count; i++) {
+                jvmtiStackInfoExtended* si = &stack_infos[i];
+                for (int j = 0; j < si->frame_count; j++) {
+                    jvmtiFrameInfoExtended* fi = &si->frame_buffer[j];
+                    frames[j].method_id = fi->method;
+                    frames[j].bci = FrameType::encode(fi->type, fi->location);
+                }
+
+                int tid = J9Ext::GetOSThreadID(si->thread);
+                ExecutionEvent event;
+                event._thread_state = (si->state & JVMTI_THREAD_STATE_RUNNABLE) ? THREAD_RUNNING : THREAD_SLEEPING;
+                Profiler::instance()->recordExternalSample(_interval, &event, tid, si->frame_count, frames);
+            }
+            jvmti->Deallocate((unsigned char*)stack_infos);
+        }
+
+        jni->PopLocalFrame(NULL);
+
+        OS::sleep(_interval);
+    }
+
+    free(frames);
+
+    VM::detachThread();
+}
--- a/src/j9WallClock.h
+++ b/src/j9WallClock.h
@@ -14,28 +14,39 @@
 * limitations under the License.
 */

-#ifndef _JSTACK_H
-#define _JSTACK_H
+#ifndef _J9WALLCLOCK_H
+#define _J9WALLCLOCK_H

-#include <signal.h>
+#include <pthread.h>
 #include "engine.h"


-class JStack : public Engine {
+class J9WallClock : public Engine {
  private:
-    static void signalHandler(int signo, siginfo_t* siginfo, void* ucontext);
+    static long _interval;
+
+    int _max_stack_depth;
+    volatile bool _running;
+    pthread_t _thread;
+
+    static void* threadEntry(void* wall_clock) {
+        ((J9WallClock*)wall_clock)->timerLoop();
+        return NULL;
+    }
+
+    void timerLoop();

  public:
-    const char* name() {
-        return EVENT_JSTACK;
+    const char* title() {
+        return "Wall clock profile";
    }

    const char* units() {
-        return "samples";
+        return "ns";
    }

    Error start(Arguments& args);
    void stop();
 };

-#endif // _JSTACK_H
+#endif // _J9WALLCLOCK_H
--- a/src/jattach/jattach.c
+++ b/src/jattach/jattach.c
@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 Andrei Pangin
+ * Copyright 2021 Andrei Pangin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -16,388 +16,35 @@

 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <sys/syscall.h>
-#include <dirent.h>
-#include <errno.h>
-#include <fcntl.h>
 #include <signal.h>
-#include <time.h>
 #include <unistd.h>
-
-#define MAX_PATH 1024
-#define TMP_PATH (MAX_PATH - 64)
-
-static char tmp_path[TMP_PATH] = {0};
+#include "psutil.h"


-#ifdef __linux__
-
-int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
-    // Parse /proc/pid/status to find process credentials
-    char path[64];
-    snprintf(path, sizeof(path), "/proc/%d/status", pid);
-    FILE* status_file = fopen(path, "r");
-    if (status_file == NULL) {
-        return 0;
-    }
-
-    char* line = NULL;
-    size_t size;
-
-    while (getline(&line, &size, status_file) != -1) {
-        if (strncmp(line, "Uid:", 4) == 0) {
-            // Get the effective UID, which is the second value in the line
-            *uid = (uid_t)atoi(strchr(line + 5, '\t'));
-        } else if (strncmp(line, "Gid:", 4) == 0) {
-            // Get the effective GID, which is the second value in the line
-            *gid = (gid_t)atoi(strchr(line + 5, '\t'));
-        } else if (strncmp(line, "NStgid:", 7) == 0) {
-            // PID namespaces can be nested; the last one is the innermost one
-            *nspid = atoi(strrchr(line, '\t'));
-        }
-    }
-
-    free(line);
-    fclose(status_file);
-    return 1;
-}
-
-int get_tmp_path(int pid) {
-    // A process may have its own root path (when running in chroot environment)
-    char path[64];
-    snprintf(path, sizeof(path), "/proc/%d/root", pid);
-
-    // Append /tmp to the resolved root symlink
-    ssize_t path_size = readlink(path, tmp_path, sizeof(tmp_path) - 10);
-    strcpy(tmp_path + (path_size > 1 ? path_size : 0), "/tmp");
-    return 1;
-}
-
-int enter_mount_ns(int pid) {
-#ifdef __NR_setns
-    char path[128];
-    snprintf(path, sizeof(path), "/proc/%d/ns/mnt", pid);
-
-    struct stat oldns_stat, newns_stat;
-    if (stat("/proc/self/ns/mnt", &oldns_stat) == 0 && stat(path, &newns_stat) == 0) {
-        // Don't try to call setns() if we're in the same namespace already
-        if (oldns_stat.st_ino != newns_stat.st_ino) {
-            int newns = open(path, O_RDONLY);
-            if (newns < 0) {
-                return 0;
-            }
-
-            // Some ancient Linux distributions do not have setns() function
-            int result = syscall(__NR_setns, newns, 0);
-            close(newns);
-            return result < 0 ? 0 : 1;
-        }
-    }
-#endif // __NR_setns
-
-    return 1;
-}
-
-// The first line of /proc/pid/sched looks like
-// java (1234, #threads: 12)
-// where 1234 is the required host PID
-int sched_get_host_pid(const char* path) {
-    static char* line = NULL;
-    size_t size;
-    int result = -1;
-
-    FILE* sched_file = fopen(path, "r");
-    if (sched_file != NULL) {
-        if (getline(&line, &size, sched_file) != -1) {
-            char* c = strrchr(line, '(');
-            if (c != NULL) {
-                result = atoi(c + 1);
-            }
-        }
-        fclose(sched_file);
-    }
-
-    return result;
-}
-
-// Linux kernels < 4.1 do not export NStgid field in /proc/pid/status.
-// Fortunately, /proc/pid/sched in a container exposes a host PID,
-// so the idea is to scan all container PIDs to find which one matches the host PID.
-int alt_lookup_nspid(int pid) {
-    int namespace_differs = 0;
-    char path[300];
-    snprintf(path, sizeof(path), "/proc/%d/ns/pid", pid);
-
-    // Don't bother looking for container PID if we are already in the same PID namespace
-    struct stat oldns_stat, newns_stat;
-    if (stat("/proc/self/ns/pid", &oldns_stat) == 0 && stat(path, &newns_stat) == 0) {
-        if (oldns_stat.st_ino == newns_stat.st_ino) {
-            return pid;
-        }
-        namespace_differs = 1;
-    }
-
-    // Otherwise browse all PIDs in the namespace of the target process
-    // trying to find which one corresponds to the host PID
-    snprintf(path, sizeof(path), "/proc/%d/root/proc", pid);
-    DIR* dir = opendir(path);
-    if (dir != NULL) {
-        struct dirent* entry;
-        while ((entry = readdir(dir)) != NULL) {
-            if (entry->d_name[0] >= '1' && entry->d_name[0] <= '9') {
-                // Check if /proc/<container-pid>/sched points back to <host-pid>
-                snprintf(path, sizeof(path), "/proc/%d/root/proc/%s/sched", pid, entry->d_name);
-                if (sched_get_host_pid(path) == pid) {
-                    closedir(dir);
-                    return atoi(entry->d_name);
-                }
-            }
-        }
-        closedir(dir);
-    }
-
-    if (namespace_differs) {
-        printf("WARNING: couldn't find container pid of the target process\n");
-    }
-
-    return pid;
-}
-
-#elif defined(__APPLE__)
-
-#include <sys/sysctl.h>
-
-int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
-    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
-    struct kinfo_proc info;
-    size_t len = sizeof(info);
-
-    if (sysctl(mib, 4, &info, &len, NULL, 0) < 0 || len <= 0) {
-        return 0;
-    }
-
-    *uid = info.kp_eproc.e_ucred.cr_uid;
-    *gid = info.kp_eproc.e_ucred.cr_gid;
-    *nspid = pid;
-    return 1;
-}
-
-// macOS has a secure per-user temporary directory
-int get_tmp_path(int pid) {
-    int path_size = confstr(_CS_DARWIN_USER_TEMP_DIR, tmp_path, sizeof(tmp_path));
-    return path_size > 0 && path_size <= sizeof(tmp_path);
-}
-
-// This is a Linux-specific API; nothing to do on macOS and FreeBSD
-int enter_mount_ns(int pid) {
-    return 1;
-}
-
-// Not used on macOS and FreeBSD
-int alt_lookup_nspid(int pid) {
-    return pid;
-}
-
-#else // __FreeBSD__
-
-#include <sys/sysctl.h>
-#include <sys/user.h>
-
-int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
-    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
-    struct kinfo_proc info;
-    size_t len = sizeof(info);
-
-    if (sysctl(mib, 4, &info, &len, NULL, 0) < 0 || len <= 0) {
-        return 0;
-    }
-
-    *uid = info.ki_uid;
-    *gid = info.ki_groups[0];
-    *nspid = pid;
-    return 1;
-}
-
-// Use default /tmp path on FreeBSD
-int get_tmp_path(int pid) {
-    return 0;
-}
-
-// This is a Linux-specific API; nothing to do on macOS and FreeBSD
-int enter_mount_ns(int pid) {
-    return 1;
-}
-
-// Not used on macOS and FreeBSD
-int alt_lookup_nspid(int pid) {
-    return pid;
-}
-
-#endif
+extern int is_openj9_process(int pid);
+extern int jattach_openj9(int pid, int nspid, int argc, char** argv);
+extern int jattach_hotspot(int pid, int nspid, int argc, char** argv);


-// Check if remote JVM has already opened socket for Dynamic Attach
-static int check_socket(int pid) {
-    char path[MAX_PATH];
-    snprintf(path, sizeof(path), "%s/.java_pid%d", tmp_path, pid);
-
-    struct stat stats;
-    return stat(path, &stats) == 0 && S_ISSOCK(stats.st_mode);
-}
-
-// Check if a file is owned by current user
-static int check_file_owner(const char* path) {
-    struct stat stats;
-    if (stat(path, &stats) == 0 && stats.st_uid == geteuid()) {
-        return 1;
-    }
-
-    // Some mounted filesystems may change the ownership of the file.
-    // JVM will not trust such file, so it's better to remove it and try a different path
-    unlink(path);
-    return 0;
-}
-
-// Force remote JVM to start Attach listener.
-// HotSpot will start Attach listener in response to SIGQUIT if it sees .attach_pid file
-static int start_attach_mechanism(int pid, int nspid) {
-    char path[MAX_PATH];
-    snprintf(path, sizeof(path), "/proc/%d/cwd/.attach_pid%d", nspid, nspid);
-    
-    int fd = creat(path, 0660);
-    if (fd == -1 || (close(fd) == 0 && !check_file_owner(path))) {
-        // Failed to create attach trigger in current directory. Retry in /tmp
-        snprintf(path, sizeof(path), "%s/.attach_pid%d", tmp_path, nspid);
-        fd = creat(path, 0660);
-        if (fd == -1) {
-            return 0;
-        }
-        close(fd);
-    }
-    
-    // We have to still use the host namespace pid here for the kill() call
-    kill(pid, SIGQUIT);
-    
-    // Start with 20 ms sleep and increment delay each iteration
-    struct timespec ts = {0, 20000000};
-    int result;
-    do {
-        nanosleep(&ts, NULL);
-        result = check_socket(nspid);
-    } while (!result && (ts.tv_nsec += 20000000) < 300000000);
-
-    unlink(path);
-    return result;
-}
-
-// Connect to UNIX domain socket created by JVM for Dynamic Attach
-static int connect_socket(int pid) {
-    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
-    if (fd == -1) {
-        return -1;
-    }
-    
-    struct sockaddr_un addr;
-    addr.sun_family = AF_UNIX;
-    int bytes = snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.java_pid%d", tmp_path, pid);
-    if (bytes >= sizeof(addr.sun_path)) {
-        addr.sun_path[sizeof(addr.sun_path) - 1] = 0;
-    }
-
-    if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
-        close(fd);
-        return -1;
-    }
-    return fd;
-}
-
-// Send command with arguments to socket
-static int write_command(int fd, int argc, char** argv) {
-    // Protocol version
-    if (write(fd, "1", 2) <= 0) {
-        return 0;
-    }
-
-    int i;
-    for (i = 0; i < 4; i++) {
-        const char* arg = i < argc ? argv[i] : "";
-        if (write(fd, arg, strlen(arg) + 1) <= 0) {
-            return 0;
-        }
-    }
-    return 1;
-}
-
-// Mirror response from remote JVM to stdout
-static int read_response(int fd) {
-    char buf[8192];
-    ssize_t bytes = read(fd, buf, sizeof(buf) - 1);
-    if (bytes <= 0) {
-        perror("Error reading response");
-        return 1;
-    }
-
-    // First line of response is the command result code
-    buf[bytes] = 0;
-    int result = atoi(buf);
-
-    do {
-        fwrite(buf, 1, bytes, stdout);
-        bytes = read(fd, buf, sizeof(buf));
-    } while (bytes > 0);
-
-    return result;
-}
-
-int main(int argc, char** argv) {
-    if (argc < 3) {
-        printf("jattach " JATTACH_VERSION " built on " __DATE__ "\n"
-               "Copyright 2018 Andrei Pangin\n"
-               "\n"
-               "Usage: jattach <pid> <cmd> [args ...]\n");
-        return 1;
-    }
-    
-    int pid = atoi(argv[1]);
-    if (pid == 0) {
-        perror("Invalid pid provided");
-        return 1;
-    }
-
+__attribute__((visibility("default")))
+int jattach(int pid, int argc, char** argv) {
    uid_t my_uid = geteuid();
    gid_t my_gid = getegid();
    uid_t target_uid = my_uid;
    gid_t target_gid = my_gid;
-    int nspid = -1;
-    if (!get_process_info(pid, &target_uid, &target_gid, &nspid)) {
+    int nspid;
+    if (get_process_info(pid, &target_uid, &target_gid, &nspid) < 0) {
        fprintf(stderr, "Process %d not found\n", pid);
        return 1;
    }

-    if (nspid < 0) {
-        nspid = alt_lookup_nspid(pid);
-    }
+    // Container support: switch to the target namespaces.
+    // Network and IPC namespaces are essential for OpenJ9 connection.
+    enter_ns(pid, "net");
+    enter_ns(pid, "ipc");
+    int mnt_changed = enter_ns(pid, "mnt");

-    // Get attach socket path of the target process (usually /tmp)
-    char* jattach_path = getenv("JATTACH_PATH");
-    if (jattach_path != NULL && strlen(jattach_path) < TMP_PATH) {
-        strcpy(tmp_path, jattach_path);
-    } else {
-        // Make sure our /tmp and target /tmp is the same
-        if (!get_tmp_path(pid)) {
-            strcpy(tmp_path, "/tmp");
-        }
-        if (!enter_mount_ns(pid)) {
-            printf("WARNING: couldn't enter target process mnt namespace\n");
-        }
-    }
-
-    // Dynamic attach is allowed only for the clients with the same euid/egid.
+    // In HotSpot, dynamic attach is allowed only for the clients with the same euid/egid.
    // If we are running under root, switch to the required euid/egid automatically.
    if ((my_gid != target_gid && setegid(target_gid) != 0) ||
        (my_uid != target_uid && seteuid(target_uid) != 0)) {
@@ -405,33 +52,37 @@ int main(int argc, char** argv) {
        return 1;
    }

-    // Make write() return EPIPE instead of silent process termination
+    get_tmp_path(mnt_changed > 0 ? nspid : pid);
+
+    // Make write() return EPIPE instead of abnormal process termination
    signal(SIGPIPE, SIG_IGN);

-    if (!check_socket(nspid) && !start_attach_mechanism(pid, nspid)) {
-        perror("Could not start attach mechanism");
-        return 1;
+    if (is_openj9_process(nspid)) {
+        return jattach_openj9(pid, nspid, argc, argv);
+    } else {
+        return jattach_hotspot(pid, nspid, argc, argv);
    }
-
-    int fd = connect_socket(nspid);
-    if (fd == -1) {
-        perror("Could not connect to socket");
-        return 1;
-    }
-    
-    printf("Connected to remote JVM\n");
-    if (!write_command(fd, argc - 2, argv + 2)) {
-        perror("Error writing to socket");
-        close(fd);
-        return 1;
-    }
-
-    printf("Response code = ");
-    fflush(stdout);
-
-    int result = read_response(fd);
-    printf("\n");
-    close(fd);
-
-    return result;
+}
+
+int main(int argc, char** argv) {
+    if (argc < 3) {
+        printf("jattach " JATTACH_VERSION " built on " __DATE__ "\n"
+               "Copyright 2021 Andrei Pangin\n"
+               "\n"
+               "Usage: jattach <pid> <cmd> [args ...]\n"
+               "\n"
+               "Commands:\n"
+               "    load  threaddump   dumpheap  setflag    properties\n"
+               "    jcmd  inspectheap  datadump  printflag  agentProperties\n"
+               );
+        return 1;
+    }
+
+    int pid = atoi(argv[1]);
+    if (pid <= 0) {
+        fprintf(stderr, "%s is not a valid process ID\n", argv[1]);
+        return 1;
+    }
+
+    return jattach(pid, argc - 2, argv + 2);
 }
--- a/src/jattach/jattach_hotspot.c
+++ b/src/jattach/jattach_hotspot.c
@@ -0,0 +1,184 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <time.h>
+#include <unistd.h>
+#include "psutil.h"
+
+
+// Check if remote JVM has already opened socket for Dynamic Attach
+static int check_socket(int pid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.java_pid%d", tmp_path, pid);
+
+    struct stat stats;
+    return stat(path, &stats) == 0 && S_ISSOCK(stats.st_mode) ? 0 : -1;
+}
+
+// Check if a file is owned by current user
+static uid_t get_file_owner(const char* path) {
+    struct stat stats;
+    return stat(path, &stats) == 0 ? stats.st_uid : (uid_t)-1;
+}
+
+// Force remote JVM to start Attach listener.
+// HotSpot will start Attach listener in response to SIGQUIT if it sees .attach_pid file
+static int start_attach_mechanism(int pid, int nspid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "/proc/%d/cwd/.attach_pid%d", nspid, nspid);
+
+    int fd = creat(path, 0660);
+    if (fd == -1 || (close(fd) == 0 && get_file_owner(path) != geteuid())) {
+        // Some mounted filesystems may change the ownership of the file.
+        // JVM will not trust such file, so it's better to remove it and try a different path
+        unlink(path);
+
+        // Failed to create attach trigger in current directory. Retry in /tmp
+        snprintf(path, sizeof(path), "%s/.attach_pid%d", tmp_path, nspid);
+        fd = creat(path, 0660);
+        if (fd == -1) {
+            return -1;
+        }
+        close(fd);
+    }
+
+    // We have to still use the host namespace pid here for the kill() call
+    kill(pid, SIGQUIT);
+
+    // Start with 20 ms sleep and increment delay each iteration. Total timeout is 6000 ms
+    struct timespec ts = {0, 20000000};
+    int result;
+    do {
+        nanosleep(&ts, NULL);
+        result = check_socket(nspid);
+    } while (result != 0 && (ts.tv_nsec += 20000000) < 500000000);
+
+    unlink(path);
+    return result;
+}
+
+// Connect to UNIX domain socket created by JVM for Dynamic Attach
+static int connect_socket(int pid) {
+    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
+    if (fd == -1) {
+        return -1;
+    }
+
+    struct sockaddr_un addr;
+    addr.sun_family = AF_UNIX;
+
+    int bytes = snprintf(addr.sun_path, sizeof(addr.sun_path), "%s/.java_pid%d", tmp_path, pid);
+    if (bytes >= sizeof(addr.sun_path)) {
+        addr.sun_path[sizeof(addr.sun_path) - 1] = 0;
+    }
+
+    if (connect(fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
+        close(fd);
+        return -1;
+    }
+    return fd;
+}
+
+// Send command with arguments to socket
+static int write_command(int fd, int argc, char** argv) {
+    // Protocol version
+    if (write(fd, "1", 2) <= 0) {
+        return -1;
+    }
+
+    int i;
+    for (i = 0; i < 4; i++) {
+        const char* arg = i < argc ? argv[i] : "";
+        if (write(fd, arg, strlen(arg) + 1) <= 0) {
+            return -1;
+        }
+    }
+    return 0;
+}
+
+// Mirror response from remote JVM to stdout
+static int read_response(int fd, int argc, char** argv) {
+    char buf[8192];
+    ssize_t bytes = read(fd, buf, sizeof(buf) - 1);
+    if (bytes == 0) {
+        fprintf(stderr, "Unexpected EOF reading response\n");
+        return 1;
+    } else if (bytes < 0) {
+        perror("Error reading response");
+        return 1;
+    }
+
+    // First line of response is the command result code
+    buf[bytes] = 0;
+    int result = atoi(buf);
+
+    // Special treatment of 'load' command
+    if (result == 0 && argc > 0 && strcmp(argv[0], "load") == 0) {
+        size_t total = bytes;
+        while (total < sizeof(buf) - 1 && (bytes = read(fd, buf + total, sizeof(buf) - 1 - total)) > 0) {
+            total += (size_t)bytes;
+        }
+        bytes = total;
+
+        // The second line is the result of 'load' command; since JDK 9 it starts from "return code: "
+        buf[bytes] = 0;
+        result = atoi(strncmp(buf + 2, "return code: ", 13) == 0 ? buf + 15 : buf + 2);
+    }
+
+    // Mirror JVM response to stdout
+    printf("JVM response code = ");
+    do {
+        fwrite(buf, 1, bytes, stdout);
+        bytes = read(fd, buf, sizeof(buf));
+    } while (bytes > 0);
+    printf("\n");
+
+    return result;
+}
+
+int jattach_hotspot(int pid, int nspid, int argc, char** argv) {
+    if (check_socket(nspid) != 0 && start_attach_mechanism(pid, nspid) != 0) {
+        perror("Could not start attach mechanism");
+        return 1;
+    }
+
+    int fd = connect_socket(nspid);
+    if (fd == -1) {
+        perror("Could not connect to socket");
+        return 1;
+    }
+
+    printf("Connected to remote JVM\n");
+
+    if (write_command(fd, argc, argv) != 0) {
+        perror("Error writing to socket");
+        close(fd);
+        return 1;
+    }
+
+    int result = read_response(fd, argc, argv);
+    close(fd);
+
+    return result;
+}
--- a/src/jattach/jattach_openj9.c
+++ b/src/jattach/jattach_openj9.c
@@ -0,0 +1,440 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/file.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <netinet/in.h>
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <time.h>
+#include <unistd.h>
+#include "psutil.h"
+
+
+#define MAX_NOTIF_FILES 256
+static int notif_lock[MAX_NOTIF_FILES];
+
+
+// Translate HotSpot command to OpenJ9 equivalent
+static void translate_command(char* buf, size_t bufsize, int argc, char** argv) {
+    const char* cmd = argv[0];
+
+    if (strcmp(cmd, "load") == 0 && argc >= 2) {
+        if (argc > 2 && strcmp(argv[2], "true") == 0) {
+            snprintf(buf, bufsize, "ATTACH_LOADAGENTPATH(%s,%s)", argv[1], argc > 3 ? argv[3] : "");
+        } else {
+            snprintf(buf, bufsize, "ATTACH_LOADAGENT(%s,%s)", argv[1], argc > 3 ? argv[3] : "");
+        }
+
+    } else if (strcmp(cmd, "jcmd") == 0) {
+        snprintf(buf, bufsize, "ATTACH_DIAGNOSTICS:%s,%s", argc > 1 ? argv[1] : "help", argc > 2 ? argv[2] : "");
+
+    } else if (strcmp(cmd, "threaddump") == 0) {
+        snprintf(buf, bufsize, "ATTACH_DIAGNOSTICS:Thread.print,%s", argc > 1 ? argv[1] : "");
+
+    } else if (strcmp(cmd, "dumpheap") == 0) {
+        snprintf(buf, bufsize, "ATTACH_DIAGNOSTICS:Dump.heap,%s", argc > 1 ? argv[1] : "");
+
+    } else if (strcmp(cmd, "inspectheap") == 0) {
+        snprintf(buf, bufsize, "ATTACH_DIAGNOSTICS:GC.class_histogram,%s", argc > 1 ? argv[1] : "");
+
+    } else if (strcmp(cmd, "datadump") == 0) {
+        snprintf(buf, bufsize, "ATTACH_DIAGNOSTICS:Dump.java,%s", argc > 1 ? argv[1] : "");
+
+    } else if (strcmp(cmd, "properties") == 0) {
+        strcpy(buf, "ATTACH_GETSYSTEMPROPERTIES");
+
+    } else if (strcmp(cmd, "agentProperties") == 0) {
+        strcpy(buf, "ATTACH_GETAGENTPROPERTIES");
+
+    } else {
+        snprintf(buf, bufsize, "%s", cmd);
+    }
+
+    buf[bufsize - 1] = 0;
+}
+
+// Unescape a string and print it on stdout
+static void print_unescaped(char* str) {
+    char* p = strchr(str, '\n');
+    if (p != NULL) {
+        *p = 0;
+    }
+
+    while ((p = strchr(str, '\\')) != NULL) {
+        switch (p[1]) {
+            case 0:
+                break;
+            case 'f':
+                *p = '\f';
+                break;
+            case 'n':
+                *p = '\n';
+                break;
+            case 'r':
+                *p = '\r';
+                break;
+            case 't':
+                *p = '\t';
+                break;
+            default:
+                *p = p[1];
+        }
+        fwrite(str, 1, p - str + 1, stdout);
+        str = p + 2;
+    }
+
+    fwrite(str, 1, strlen(str), stdout);
+    printf("\n");
+}
+
+// Send command with arguments to socket
+static int write_command(int fd, const char* cmd) {
+    size_t len = strlen(cmd) + 1;
+    size_t off = 0;
+    while (off < len) {
+        ssize_t bytes = write(fd, cmd + off, len - off);
+        if (bytes <= 0) {
+            return -1;
+        }
+        off += bytes;
+    }
+    return 0;
+}
+
+// Mirror response from remote JVM to stdout
+static int read_response(int fd, const char* cmd) {
+    size_t size = 8192;
+    char* buf = malloc(size);
+
+    size_t off = 0;
+    while (buf != NULL) {
+        ssize_t bytes = read(fd, buf + off, size - off);
+        if (bytes == 0) {
+            fprintf(stderr, "Unexpected EOF reading response\n");
+            return 1;
+        } else if (bytes < 0) {
+            perror("Error reading response");
+            return 1;
+        }
+
+        off += bytes;
+        if (buf[off - 1] == 0) {
+            break;
+        }
+
+        if (off >= size) {
+            buf = realloc(buf, size *= 2);
+        }
+    }
+
+    if (buf == NULL) {
+        fprintf(stderr, "Failed to allocate memory for response\n");
+        return 1;
+    }
+
+    int result = 0;
+
+    if (strncmp(cmd, "ATTACH_LOADAGENT", 16) == 0) {
+        if (strncmp(buf, "ATTACH_ACK", 10) != 0) {
+            // AgentOnLoad error code comes right after AgentInitializationException
+            result = strncmp(buf, "ATTACH_ERR AgentInitializationException", 39) == 0 ? atoi(buf + 39) : -1;
+        }
+    } else if (strncmp(cmd, "ATTACH_DIAGNOSTICS:", 19) == 0) {
+        char* p = strstr(buf, "openj9_diagnostics.string_result=");
+        if (p != NULL) {
+            // The result of a diagnostic command is encoded in Java Properties format
+            print_unescaped(p + 33);
+            free(buf);
+            return result;
+        }
+    }
+
+    buf[off - 1] = '\n';
+    fwrite(buf, 1, off, stdout);
+
+    free(buf);
+    return result;
+}
+
+static void detach(int fd) {
+    if (write_command(fd, "ATTACH_DETACHED") != 0) {
+        return;
+    }
+
+    char buf[256];
+    ssize_t bytes;
+    do {
+        bytes = read(fd, buf, sizeof(buf));
+    } while (bytes > 0 && buf[bytes - 1] != 0);
+}
+
+static void close_with_errno(int fd) {
+    int saved_errno = errno;
+    close(fd);
+    errno = saved_errno;
+}
+
+static int acquire_lock(const char* subdir, const char* filename) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach/%s/%s", tmp_path, subdir, filename);
+
+    int lock_fd = open(path, O_WRONLY | O_CREAT, 0666);
+    if (lock_fd < 0) {
+        return -1;
+    }
+
+    if (flock(lock_fd, LOCK_EX) < 0) {
+        close_with_errno(lock_fd);
+        return -1;
+    }
+
+    return lock_fd;
+}
+
+static void release_lock(int lock_fd) {
+    flock(lock_fd, LOCK_UN);
+    close(lock_fd);
+}
+
+static int create_attach_socket(int* port) {
+    // Try IPv6 socket first, then fall back to IPv4
+    int s = socket(AF_INET6, SOCK_STREAM, 0);
+    if (s != -1) {
+        struct sockaddr_in6 addr = {AF_INET6, 0};
+        socklen_t addrlen = sizeof(addr);
+        if (bind(s, (struct sockaddr*)&addr, addrlen) == 0 && listen(s, 0) == 0
+                && getsockname(s, (struct sockaddr*)&addr, &addrlen) == 0) {
+            *port = ntohs(addr.sin6_port);
+            return s;
+        }
+    } else if ((s = socket(AF_INET, SOCK_STREAM, 0)) != -1) {
+        struct sockaddr_in addr = {AF_INET, 0};
+        socklen_t addrlen = sizeof(addr);
+        if (bind(s, (struct sockaddr*)&addr, addrlen) == 0 && listen(s, 0) == 0
+                && getsockname(s, (struct sockaddr*)&addr, &addrlen) == 0) {
+            *port = ntohs(addr.sin_port);
+            return s;
+        }
+    }
+
+    close_with_errno(s);
+    return -1;
+}
+
+static void close_attach_socket(int s, int pid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach/%d/replyInfo", tmp_path, pid);
+    unlink(path);
+
+    close(s);
+}
+
+static unsigned long long random_key() {
+    unsigned long long key = time(NULL) * 0xc6a4a7935bd1e995ULL;
+
+    int fd = open("/dev/urandom", O_RDONLY);
+    if (fd >= 0) {
+        ssize_t r = read(fd, &key, sizeof(key));
+        (void)r;
+        close(fd);
+    }
+
+    return key;
+}
+
+static int write_reply_info(int pid, int port, unsigned long long key) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach/%d/replyInfo", tmp_path, pid);
+
+    int fd = open(path, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (fd < 0) {
+        return -1;
+    }
+
+    int chars = snprintf(path, sizeof(path), "%016llx\n%d\n", key, port);
+    ssize_t r = write(fd, path, chars);
+    (void)r;
+    close(fd);
+
+    return 0;
+}
+
+static int notify_semaphore(int value, int notif_count) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach/_notifier", tmp_path);
+
+    key_t sem_key = ftok(path, 0xa1);
+    int sem = semget(sem_key, 1, IPC_CREAT | 0666);
+    if (sem < 0) {
+        return -1;
+    }
+
+    struct sembuf op = {0, value, value < 0 ? IPC_NOWAIT : 0};
+    while (notif_count-- > 0) {
+        semop(sem, &op, 1);
+    }
+
+    return 0;
+}
+
+static int accept_client(int s, unsigned long long key) {
+    struct timeval tv = {5, 0};
+    setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
+
+    int client = accept(s, NULL, NULL);
+    if (client < 0) {
+        perror("JVM did not respond");
+        return -1;
+    }
+
+    char buf[35];
+    size_t off = 0;
+    while (off < sizeof(buf)) {
+        ssize_t bytes = recv(client, buf + off, sizeof(buf) - off, 0);
+        if (bytes <= 0) {
+            fprintf(stderr, "The JVM connection was prematurely closed\n");
+            close(client);
+            return -1;
+        }
+        off += bytes;
+    }
+
+    char expected[35];
+    snprintf(expected, sizeof(expected), "ATTACH_CONNECTED %016llx ", key);
+    if (memcmp(buf, expected, sizeof(expected) - 1) != 0) {
+        fprintf(stderr, "Unexpected JVM response\n");
+        close(client);
+        return -1;
+    }
+
+    return client;
+}
+
+static int lock_notification_files() {
+    int count = 0;
+
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach", tmp_path);
+
+    DIR* dir = opendir(path);
+    if (dir != NULL) {
+        struct dirent* entry;
+        while ((entry = readdir(dir)) != NULL && count < MAX_NOTIF_FILES) {
+            if (entry->d_name[0] >= '1' && entry->d_name[0] <= '9' &&
+                (entry->d_type == DT_DIR || entry->d_type == DT_UNKNOWN)) {
+                notif_lock[count++] = acquire_lock(entry->d_name, "attachNotificationSync");
+            }
+        }
+        closedir(dir);
+    }
+
+    return count;
+}
+
+static void unlock_notification_files(int count) {
+    int i;
+    for (i = 0; i < count; i++) {
+        if (notif_lock[i] >= 0) {
+            release_lock(notif_lock[i]);
+        }
+    }
+}
+
+int is_openj9_process(int pid) {
+    char path[MAX_PATH];
+    snprintf(path, sizeof(path), "%s/.com_ibm_tools_attach/%d/attachInfo", tmp_path, pid);
+
+    struct stat stats;
+    return stat(path, &stats) == 0;
+}
+
+int jattach_openj9(int pid, int nspid, int argc, char** argv) {
+    int attach_lock = acquire_lock("", "_attachlock");
+    if (attach_lock < 0) {
+        perror("Could not acquire attach lock");
+        return 1;
+    }
+
+    int notif_count = 0;
+    int port;
+    int s = create_attach_socket(&port);
+    if (s < 0) {
+        perror("Failed to listen to attach socket");
+        goto error;
+    }
+
+    unsigned long long key = random_key();
+    if (write_reply_info(nspid, port, key) != 0) {
+        perror("Could not write replyInfo");
+        goto error;
+    }
+
+    notif_count = lock_notification_files();
+    if (notify_semaphore(1, notif_count) != 0) {
+        perror("Could not notify semaphore");
+        goto error;
+    }
+
+    int fd = accept_client(s, key);
+    if (fd < 0) {
+        // The error message has been already printed
+        goto error;
+    }
+
+    close_attach_socket(s, nspid);
+    unlock_notification_files(notif_count);
+    notify_semaphore(-1, notif_count);
+    release_lock(attach_lock);
+
+    printf("Connected to remote JVM\n");
+
+    char cmd[8192];
+    translate_command(cmd, sizeof(cmd), argc, argv);
+
+    if (write_command(fd, cmd) != 0) {
+        perror("Error writing to socket");
+        close(fd);
+        return 1;
+    }
+
+    int result = read_response(fd, cmd);
+    if (result != 1) {
+        detach(fd);
+    }
+    close(fd);
+
+    return result;
+
+error:
+    if (s >= 0) {
+        close_attach_socket(s, nspid);
+    }
+    if (notif_count > 0) {
+        unlock_notification_files(notif_count);
+        notify_semaphore(-1, notif_count);
+    }
+    release_lock(attach_lock);
+
+    return 1;
+}
--- a/src/jattach/psutil.c
+++ b/src/jattach/psutil.c
@@ -0,0 +1,241 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/syscall.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "psutil.h"
+
+
+// Less than MAX_PATH to leave some space for appending
+char tmp_path[MAX_PATH - 100];
+
+// Called just once to fill in tmp_path buffer
+void get_tmp_path(int pid) {
+    // Try user-provided alternative path first
+    const char* jattach_path = getenv("JATTACH_PATH");
+    if (jattach_path != NULL && strlen(jattach_path) < sizeof(tmp_path)) {
+        strcpy(tmp_path, jattach_path);
+        return;
+    }
+
+    if (get_tmp_path_r(pid, tmp_path, sizeof(tmp_path)) != 0) {
+        strcpy(tmp_path, "/tmp");
+    }
+}
+
+
+#ifdef __linux__
+
+// The first line of /proc/pid/sched looks like
+// java (1234, #threads: 12)
+// where 1234 is the host PID (before Linux 4.1)
+static int sched_get_host_pid(const char* path) {
+    static char* line = NULL;
+    size_t size;
+    int result = -1;
+
+    FILE* sched_file = fopen(path, "r");
+    if (sched_file != NULL) {
+        if (getline(&line, &size, sched_file) != -1) {
+            char* c = strrchr(line, '(');
+            if (c != NULL) {
+                result = atoi(c + 1);
+            }
+        }
+        fclose(sched_file);
+    }
+
+    return result;
+}
+
+// Linux kernels < 4.1 do not export NStgid field in /proc/pid/status.
+// Fortunately, /proc/pid/sched in a container exposes a host PID,
+// so the idea is to scan all container PIDs to find which one matches the host PID.
+static int alt_lookup_nspid(int pid) {
+    char path[300];
+    snprintf(path, sizeof(path), "/proc/%d/ns/pid", pid);
+
+    // Don't bother looking for container PID if we are already in the same PID namespace
+    struct stat oldns_stat, newns_stat;
+    if (stat("/proc/self/ns/pid", &oldns_stat) == 0 && stat(path, &newns_stat) == 0) {
+        if (oldns_stat.st_ino == newns_stat.st_ino) {
+            return pid;
+        }
+    }
+
+    // Otherwise browse all PIDs in the namespace of the target process
+    // trying to find which one corresponds to the host PID
+    snprintf(path, sizeof(path), "/proc/%d/root/proc", pid);
+    DIR* dir = opendir(path);
+    if (dir != NULL) {
+        struct dirent* entry;
+        while ((entry = readdir(dir)) != NULL) {
+            if (entry->d_name[0] >= '1' && entry->d_name[0] <= '9') {
+                // Check if /proc/<container-pid>/sched points back to <host-pid>
+                snprintf(path, sizeof(path), "/proc/%d/root/proc/%s/sched", pid, entry->d_name);
+                if (sched_get_host_pid(path) == pid) {
+                    closedir(dir);
+                    return atoi(entry->d_name);
+                }
+            }
+        }
+        closedir(dir);
+    }
+
+    // Could not find container pid; return host pid as the last resort
+    return pid;
+}
+
+int get_tmp_path_r(int pid, char* buf, size_t bufsize) {
+    if (snprintf(buf, bufsize, "/proc/%d/root/tmp", pid) >= bufsize) {
+        return -1;
+    }
+
+    // Check if the remote /tmp can be accessed via /proc/[pid]/root
+    struct stat stats;
+    return stat(buf, &stats);
+}
+
+int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
+    // Parse /proc/pid/status to find process credentials
+    char path[64];
+    snprintf(path, sizeof(path), "/proc/%d/status", pid);
+    FILE* status_file = fopen(path, "r");
+    if (status_file == NULL) {
+        return -1;
+    }
+
+    char* line = NULL;
+    size_t size;
+    int nspid_found = 0;
+
+    while (getline(&line, &size, status_file) != -1) {
+        if (strncmp(line, "Uid:", 4) == 0) {
+            // Get the effective UID, which is the second value in the line
+            *uid = (uid_t)atoi(strchr(line + 5, '\t'));
+        } else if (strncmp(line, "Gid:", 4) == 0) {
+            // Get the effective GID, which is the second value in the line
+            *gid = (gid_t)atoi(strchr(line + 5, '\t'));
+        } else if (strncmp(line, "NStgid:", 7) == 0) {
+            // PID namespaces can be nested; the last one is the innermost one
+            *nspid = atoi(strrchr(line, '\t'));
+            nspid_found = 1;
+        }
+    }
+
+    free(line);
+    fclose(status_file);
+
+    if (!nspid_found) {
+        *nspid = alt_lookup_nspid(pid);
+    }
+
+    return 0;
+}
+
+int enter_ns(int pid, const char* type) {
+#ifdef __NR_setns
+    char path[64], selfpath[64];
+    snprintf(path, sizeof(path), "/proc/%d/ns/%s", pid, type);
+    snprintf(selfpath, sizeof(selfpath), "/proc/self/ns/%s", type);
+
+    struct stat oldns_stat, newns_stat;
+    if (stat(selfpath, &oldns_stat) == 0 && stat(path, &newns_stat) == 0) {
+        // Don't try to call setns() if we're in the same namespace already
+        if (oldns_stat.st_ino != newns_stat.st_ino) {
+            int newns = open(path, O_RDONLY);
+            if (newns < 0) {
+                return -1;
+            }
+
+            // Some ancient Linux distributions do not have setns() function
+            int result = syscall(__NR_setns, newns, 0);
+            close(newns);
+            return result < 0 ? -1 : 1;
+        }
+    }
+#endif // __NR_setns
+
+    return 0;
+}
+
+#elif defined(__APPLE__)
+
+#include <sys/sysctl.h>
+
+// macOS has a secure per-user temporary directory
+int get_tmp_path_r(int pid, char* buf, size_t bufsize) {
+    size_t path_size = confstr(_CS_DARWIN_USER_TEMP_DIR, buf, bufsize);
+    return path_size > 0 && path_size <= sizeof(tmp_path) ? 0 : -1;
+}
+
+int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
+    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
+    struct kinfo_proc info;
+    size_t len = sizeof(info);
+
+    if (sysctl(mib, 4, &info, &len, NULL, 0) < 0 || len <= 0) {
+        return -1;
+    }
+
+    *uid = info.kp_eproc.e_ucred.cr_uid;
+    *gid = info.kp_eproc.e_ucred.cr_gid;
+    *nspid = pid;
+    return 0;
+}
+
+// This is a Linux-specific API; nothing to do on macOS and FreeBSD
+int enter_ns(int pid, const char* type) {
+    return 0;
+}
+
+#else // __FreeBSD__
+
+#include <sys/sysctl.h>
+#include <sys/user.h>
+
+// Use default /tmp path on FreeBSD
+int get_tmp_path_r(int pid, char* buf, size_t bufsize) {
+    return -1;
+}
+
+int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid) {
+    int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
+    struct kinfo_proc info;
+    size_t len = sizeof(info);
+
+    if (sysctl(mib, 4, &info, &len, NULL, 0) < 0 || len <= 0) {
+        return -1;
+    }
+
+    *uid = info.ki_uid;
+    *gid = info.ki_groups[0];
+    *nspid = pid;
+    return 0;
+}
+
+// This is a Linux-specific API; nothing to do on macOS and FreeBSD
+int enter_ns(int pid, const char* type) {
+    return 0;
+}
+
+#endif
--- a/src/jattach/psutil.h
+++ b/src/jattach/psutil.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _PSUTIL_H
+#define _PSUTIL_H
+
+#include <sys/types.h>
+
+
+#define MAX_PATH 1024
+extern char tmp_path[];
+
+// Gets /tmp path of the specified process, as it can be accessed from the host.
+// The obtained path is stored in the global tmp_path buffer.
+void get_tmp_path(int pid);
+
+// The reentrant version of get_tmp_path.
+// Stores the process-specific temporary path into the provided buffer.
+// Returns 0 on success, -1 on failure.
+int get_tmp_path_r(int pid, char* buf, size_t bufsize);
+
+// Gets the owner uid/gid of the target process, and also its pid inside the container.
+// Returns 0 on success, -1 on failure.
+int get_process_info(int pid, uid_t* uid, gid_t* gid, int* nspid);
+
+// Tries to enter the namespace of the target process.
+// type of the namespace can be "mnt", "net", "pid", etc.
+// Returns 1, if the namespace has been successfully changed,
+//         0, if the target process is in the same namespace as the host,
+//        -1, if the attempt failed.
+int enter_ns(int pid, const char* type);
+
+#endif // _PSUTIL_H
--- a/src/javaApi.cpp
+++ b/src/javaApi.cpp
@@ -19,36 +19,55 @@
 #include <errno.h>
 #include <string.h>
 #include "javaApi.h"
-#include "arguments.h"
 #include "os.h"
 #include "profiler.h"
 #include "vmStructs.h"


-extern "C" JNIEXPORT void JNICALL
+static const unsigned char SERVER_CLASS[] = {
+#include "helper/one/profiler/Server.class.h"
+};
+
+
+static void throwNew(JNIEnv* env, const char* exception_class, const char* message) {
+    jclass cls = env->FindClass(exception_class);
+    if (cls != NULL) {
+        env->ThrowNew(cls, message);
+    }
+}
+
+
+extern "C" DLLEXPORT void JNICALL
 Java_one_profiler_AsyncProfiler_start0(JNIEnv* env, jobject unused, jstring event, jlong interval, jboolean reset) {
    Arguments args;
    const char* event_str = env->GetStringUTFChars(event, NULL);
-    args.addEvent(event_str); 
-    args._interval = interval;
-    Error error = Profiler::_instance.start(args, reset);
+    if (strcmp(event_str, EVENT_ALLOC) == 0) {
+        args._alloc = interval > 0 ? interval : 0;
+    } else if (strcmp(event_str, EVENT_LOCK) == 0) {
+        args._lock = interval > 0 ? interval : 0;
+    } else {
+        args._event = event_str;
+        args._interval = interval;
+    }
+
+    Error error = Profiler::instance()->start(args, reset);
    env->ReleaseStringUTFChars(event, event_str);

    if (error) {
-        JavaAPI::throwNew(env, "java/lang/IllegalStateException", error.message());
+        throwNew(env, "java/lang/IllegalStateException", error.message());
    }
 }

-extern "C" JNIEXPORT void JNICALL
+extern "C" DLLEXPORT void JNICALL
 Java_one_profiler_AsyncProfiler_stop0(JNIEnv* env, jobject unused) {
-    Error error = Profiler::_instance.stop();
+    Error error = Profiler::instance()->stop();

    if (error) {
-        JavaAPI::throwNew(env, "java/lang/IllegalStateException", error.message());
+        throwNew(env, "java/lang/IllegalStateException", error.message());
    }
 }

-extern "C" JNIEXPORT jstring JNICALL
+extern "C" DLLEXPORT jstring JNICALL
 Java_one_profiler_AsyncProfiler_execute0(JNIEnv* env, jobject unused, jstring command) {
    Arguments args;
    const char* command_str = env->GetStringUTFChars(command, NULL);
@@ -56,48 +75,54 @@ Java_one_profiler_AsyncProfiler_execute0(JNIEnv* env, jobject unused, jstring co
    env->ReleaseStringUTFChars(command, command_str);

    if (error) {
-        JavaAPI::throwNew(env, "java/lang/IllegalArgumentException", error.message());
+        throwNew(env, "java/lang/IllegalArgumentException", error.message());
        return NULL;
    }

-    if (args._file == NULL || args._output == OUTPUT_JFR) {
+    Log::open(args);
+
+    if (!args.hasOutputFile()) {
        std::ostringstream out;
-        Profiler::_instance.runInternal(args, out);
-        return env->NewStringUTF(out.str().c_str());
+        error = Profiler::instance()->runInternal(args, out);
+        if (!error) {
+            if (out.tellp() >= 0x3fffffff) {
+                throwNew(env, "java/lang/IllegalStateException", "Output exceeds string size limit");
+                return NULL;
+            }
+            return env->NewStringUTF(out.str().c_str());
+        }
    } else {
-        std::ofstream out(args._file, std::ios::out | std::ios::trunc);
-        if (out.is_open()) {
-            Profiler::_instance.runInternal(args, out);
-            out.close();
-            return env->NewStringUTF("OK");
-        } else {
-            JavaAPI::throwNew(env, "java/io/IOException", strerror(errno));
+        std::ofstream out(args.file(), std::ios::out | std::ios::trunc);
+        if (!out.is_open()) {
+            throwNew(env, "java/io/IOException", strerror(errno));
            return NULL;
        }
+        error = Profiler::instance()->runInternal(args, out);
+        out.close();
+        if (!error) {
+            return env->NewStringUTF("OK");
+        }
    }
+
+    throwNew(env, "java/lang/IllegalStateException", error.message());
+    return NULL;
 }

-extern "C" JNIEXPORT jlong JNICALL
+extern "C" DLLEXPORT jlong JNICALL
 Java_one_profiler_AsyncProfiler_getSamples(JNIEnv* env, jobject unused) {
-    return (jlong)Profiler::_instance.total_samples();
+    return (jlong)Profiler::instance()->total_samples();
 }

-extern "C" JNIEXPORT void JNICALL
+extern "C" DLLEXPORT void JNICALL
 Java_one_profiler_AsyncProfiler_filterThread0(JNIEnv* env, jobject unused, jthread thread, jboolean enable) {
    int thread_id;
    if (thread == NULL) {
        thread_id = OS::threadId();
-    } else if (VMThread::hasNativeId()) {
-        VMThread* vmThread = VMThread::fromJavaThread(env, thread);
-        if (vmThread == NULL) {
-            return;
-        }
-        thread_id = vmThread->osThreadId();
-    } else {
+    } else if ((thread_id = VMThread::nativeThreadId(env, thread)) < 0) {
        return;
    }

-    ThreadFilter* thread_filter = Profiler::_instance.threadFilter();
+    ThreadFilter* thread_filter = Profiler::instance()->threadFilter();
    if (enable) {
        thread_filter->add(thread_id);
    } else {
@@ -116,16 +141,11 @@ static const JNINativeMethod profiler_natives[] = {
    F(filterThread0, "(Ljava/lang/Thread;Z)V"),
 };

+static const JNINativeMethod* execute0 = &profiler_natives[2];
+
 #undef F


-void JavaAPI::throwNew(JNIEnv* env, const char* exception_class, const char* message) {
-    jclass cls = env->FindClass(exception_class);
-    if (cls != NULL) {
-        env->ThrowNew(cls, message);
-    }
-}
-
 // Since AsyncProfiler class can be renamed or moved to another package (shaded),
 // we look for the actual class in the stack trace.
 void JavaAPI::registerNatives(jvmtiEnv* jvmti, JNIEnv* jni) {
@@ -155,3 +175,23 @@ void JavaAPI::registerNatives(jvmtiEnv* jvmti, JNIEnv* jni) {

    jni->ExceptionClear();
 }
+
+bool JavaAPI::startHttpServer(jvmtiEnv* jvmti, JNIEnv* jni, const char* address) {
+    jclass handler = jni->FindClass("com/sun/net/httpserver/HttpHandler");
+    jobject loader;
+    if (handler != NULL && jvmti->GetClassLoader(handler, &loader) == 0) {
+        jclass cls = jni->DefineClass(NULL, loader, (const jbyte*)SERVER_CLASS, sizeof(SERVER_CLASS));
+        if (cls != NULL && jni->RegisterNatives(cls, execute0, 1) == 0) {
+            jmethodID method = jni->GetStaticMethodID(cls, "start", "(Ljava/lang/String;)V");
+            if (method != NULL) {
+                jni->CallStaticVoidMethod(cls, method, jni->NewStringUTF(address));
+                if (!jni->ExceptionCheck()) {
+                    return true;
+                }
+            }
+        }
+    }
+
+    jni->ExceptionDescribe();
+    return false;
+}
--- a/src/javaApi.h
+++ b/src/javaApi.h
@@ -22,8 +22,8 @@

 class JavaAPI {
  public:
-    static void throwNew(JNIEnv* env, const char* exception_class, const char* message);
    static void registerNatives(jvmtiEnv* jvmti, JNIEnv* jni);
+    static bool startHttpServer(jvmtiEnv* jvmti, JNIEnv* jni, const char* address);
 };

 #endif // _JAVAAPI_H
--- a/src/jfrMetadata.cpp
+++ b/src/jfrMetadata.cpp
@@ -82,6 +82,9 @@ JfrMetadata::JfrMetadata() : Element("root") {
            << (type("jdk.types.Symbol", T_SYMBOL, "Symbol", true)
                << field("string", T_STRING, "String"))

+            << (type("profiler.types.LogLevel", T_LOG_LEVEL, "Log Level", true)
+                << field("name", T_STRING, "Name"))
+
            << (type("jdk.ExecutionSample", T_EXECUTION_SAMPLE, "Method Profiling Sample")
                << category("Java Virtual Machine", "Profiling")
                << field("startTime", T_LONG, "Start Time", F_TIME_TICKS)
@@ -113,6 +116,7 @@ JfrMetadata::JfrMetadata() : Element("root") {
                << field("eventThread", T_THREAD, "Event Thread", F_CPOOL)
                << field("stackTrace", T_STACK_TRACE, "Stack Trace", F_CPOOL)
                << field("monitorClass", T_CLASS, "Monitor Class", F_CPOOL)
+                << field("previousOwner", T_THREAD, "Previous Monitor Owner", F_CPOOL)
                << field("address", T_LONG, "Monitor Address", F_ADDRESS))

            << (type("jdk.ThreadPark", T_THREAD_PARK, "Java Thread Park")
@@ -123,6 +127,7 @@ JfrMetadata::JfrMetadata() : Element("root") {
                << field("stackTrace", T_STACK_TRACE, "Stack Trace", F_CPOOL)
                << field("parkedClass", T_CLASS, "Class Parked On", F_CPOOL)
                << field("timeout", T_LONG, "Park Timeout", F_DURATION_NANOS)
+                << field("until", T_LONG, "Park Until", F_TIME_MILLIS)
                << field("address", T_LONG, "Address of Object Parked", F_ADDRESS))

            << (type("jdk.CPULoad", T_CPU_LOAD, "CPU Load")
@@ -132,7 +137,7 @@ JfrMetadata::JfrMetadata() : Element("root") {
                << field("jvmSystem", T_FLOAT, "JVM System", F_PERCENTAGE)
                << field("machineTotal", T_FLOAT, "Machine Total", F_PERCENTAGE))

-            << (type("jdk.ActiveRecording", T_ACTIVE_RECORDING, "Flight Recording")
+            << (type("jdk.ActiveRecording", T_ACTIVE_RECORDING, "Async-profiler Recording")
                << category("Flight Recorder")
                << field("startTime", T_LONG, "Start Time", F_TIME_TICKS)
                << field("duration", T_LONG, "Duration", F_DURATION_TICKS)
@@ -145,11 +150,12 @@ JfrMetadata::JfrMetadata() : Element("root") {
                << field("recordingStart", T_LONG, "Start Time", F_TIME_MILLIS)
                << field("recordingDuration", T_LONG, "Recording Duration", F_DURATION_MILLIS))

-            << (type("jdk.ActiveSetting", T_ACTIVE_SETTING, "Recording Setting")
+            << (type("jdk.ActiveSetting", T_ACTIVE_SETTING, "Async-profiler Setting")
                << category("Flight Recorder")
                << field("startTime", T_LONG, "Start Time", F_TIME_TICKS)
                << field("duration", T_LONG, "Duration", F_DURATION_TICKS)
                << field("eventThread", T_THREAD, "Event Thread", F_CPOOL)
+                << field("stackTrace", T_STACK_TRACE, "Stack Trace", F_CPOOL)
                << field("id", T_LONG, "Event Id")
                << field("name", T_STRING, "Setting Name")
                << field("value", T_STRING, "Setting Value"))
@@ -185,6 +191,19 @@ JfrMetadata::JfrMetadata() : Element("root") {
                << field("key", T_STRING, "Key")
                << field("value", T_STRING, "Value"))

+            << (type("jdk.NativeLibrary", T_NATIVE_LIBRARY, "Native Library")
+                << category("Java Virtual Machine", "Runtime")
+                << field("startTime", T_LONG, "Start Time", F_TIME_TICKS)
+                << field("name", T_STRING, "Name")
+                << field("baseAddress", T_LONG, "Base Address", F_ADDRESS)
+                << field("topAddress", T_LONG, "Top Address", F_ADDRESS))
+
+            << (type("profiler.Log", T_LOG, "Log Message")
+                << category("Profiler")
+                << field("startTime", T_LONG, "Start Time", F_TIME_TICKS)
+                << field("level", T_LOG_LEVEL, "Level", F_CPOOL)
+                << field("message", T_STRING, "Message"))
+
            << (type("jdk.jfr.Label", T_LABEL, NULL)
                << field("value", T_STRING))

--- a/src/jfrMetadata.h
+++ b/src/jfrMetadata.h
@@ -48,6 +48,7 @@ enum JfrType {
    T_METHOD = 28,
    T_PACKAGE = 29,
    T_SYMBOL = 30,
+    T_LOG_LEVEL = 31,

    T_EVENT = 100,
    T_EXECUTION_SAMPLE = 101,
@@ -62,6 +63,8 @@ enum JfrType {
    T_CPU_INFORMATION = 110,
    T_JVM_INFORMATION = 111,
    T_INITIAL_SYSTEM_PROPERTY = 112,
+    T_NATIVE_LIBRARY = 113,
+    T_LOG = 114,

    T_ANNOTATION = 200,
    T_LABEL = 201,
--- a/src/jstack.cpp
+++ b/src/jstack.cpp
@@ -1,71 +0,0 @@
-/*
- * Copyright 2021 Andrei Pangin
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <signal.h>
-#include <time.h>
-#include "jstack.h"
-#include "profiler.h"
-
-
-// Wait at most this number of milliseconds to finish processing of pending signals
-const int MAX_WAIT_MILLIS = 2000;
-
-
-void JStack::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
-    ExecutionEvent event;
-    event._thread_state = Profiler::_instance.getThreadState(ucontext);
-    Profiler::_instance.recordSample(ucontext, 1, 0, &event);
-}
-
-Error JStack::start(Arguments& args) {
-    OS::installSignalHandler(SIGVTALRM, signalHandler);
-
-    int self = OS::threadId();
-    u64 required_samples = Profiler::_instance.total_samples();
-    ThreadFilter* thread_filter = Profiler::_instance.threadFilter();
-    bool thread_filter_enabled = thread_filter->enabled();
-
-    ThreadList* thread_list = OS::listThreads();
-    int thread_id;
-    while ((thread_id = thread_list->next()) != -1) {
-        if (thread_id != self && (!thread_filter_enabled || thread_filter->accept(thread_id))) {
-            if (OS::sendSignalToThread(thread_id, SIGVTALRM)) {
-                required_samples++;
-            }
-        }
-    }
-    delete thread_list;
-
-    // Get our own stack trace after all other threads
-    if (!thread_filter_enabled || thread_filter->accept(self)) {
-        ExecutionEvent event;
-        event._thread_state = THREAD_RUNNING;
-        Profiler::_instance.recordSample(NULL, 1, 0, &event);
-        required_samples++;
-    }
-
-    // Wait until all asynchronous stack traces collected
-    for (int i = 0; Profiler::_instance.total_samples() < required_samples && i < MAX_WAIT_MILLIS; i++) {
-        struct timespec timeout = {0, 1000000};
-        nanosleep(&timeout, NULL);
-    }
-
-    return Error::OK;
-}
-
-void JStack::stop() {
-    // Nothing to do
-}
--- a/src/lockTracer.cpp
+++ b/src/lockTracer.cpp
@@ -16,31 +16,37 @@

 #include <string.h>
 #include "lockTracer.h"
-#include "os.h"
 #include "profiler.h"
-#include "vmStructs.h"
+#include "tsc.h"


+double LockTracer::_ticks_to_nanos;
+jlong LockTracer::_threshold;
 jlong LockTracer::_start_time = 0;
+jclass LockTracer::_UnsafeClass = NULL;
 jclass LockTracer::_LockSupport = NULL;
 jmethodID LockTracer::_getBlocker = NULL;
+RegisterNativesFunc LockTracer::_orig_RegisterNatives = NULL;
+UnsafeParkFunc LockTracer::_orig_Unsafe_park = NULL;
+bool LockTracer::_initialized = false;

 Error LockTracer::start(Arguments& args) {
+    _ticks_to_nanos = 1e9 / TSC::frequency();
+    _threshold = (jlong)(args._lock * (TSC::frequency() / 1e9));
+
+    if (!_initialized) {
+        initialize();
+    }
+
    // Enable Java Monitor events
    jvmtiEnv* jvmti = VM::jvmti();
    jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_MONITOR_CONTENDED_ENTER, NULL);
    jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_MONITOR_CONTENDED_ENTERED, NULL);
-    _start_time = OS::nanotime();
+    _start_time = TSC::ticks();

-    if (_getBlocker == NULL) {
-        JNIEnv* env = VM::jni();
-        _LockSupport = (jclass)env->NewGlobalRef(env->FindClass("java/util/concurrent/locks/LockSupport"));
-        _getBlocker = env->GetStaticMethodID(_LockSupport, "getBlocker", "(Ljava/lang/Thread;)Ljava/lang/Object;");
-    }
-
-    // Intercent Unsafe.park() for tracing contended ReentrantLocks
-    if (VMStructs::_unsafe_park != NULL) {
-        bindUnsafePark(UnsafeParkTrap);
+    // Intercept Unsafe.park() for tracing contended ReentrantLocks
+    if (_orig_Unsafe_park != NULL) {
+        bindUnsafePark(UnsafeParkHook);
    }

    return Error::OK;
@@ -53,48 +59,98 @@ void LockTracer::stop() {
    jvmti->SetEventNotificationMode(JVMTI_DISABLE, JVMTI_EVENT_MONITOR_CONTENDED_ENTERED, NULL);

    // Reset Unsafe.park() trap
-    if (VMStructs::_unsafe_park != NULL) {
-        bindUnsafePark(VMStructs::_unsafe_park);
+    if (_orig_Unsafe_park != NULL) {
+        bindUnsafePark(_orig_Unsafe_park);
    }
 }

+void LockTracer::initialize() {
+    jvmtiEnv* jvmti = VM::jvmti();
+    JNIEnv* env = VM::jni();
+
+    // Try JDK 9+ package first, then fallback to JDK 8 package
+    jclass unsafe = env->FindClass("jdk/internal/misc/Unsafe");
+    if (unsafe == NULL) {
+        env->ExceptionClear();
+        if ((unsafe = env->FindClass("sun/misc/Unsafe")) == NULL) {
+            env->ExceptionClear();
+            return;
+        }
+    }
+
+    _UnsafeClass = (jclass)env->NewGlobalRef(unsafe);
+    jmethodID register_natives = env->GetStaticMethodID(_UnsafeClass, "registerNatives", "()V");
+    jniNativeInterface* jni_functions;
+    if (register_natives != NULL && jvmti->GetJNIFunctionTable(&jni_functions) == 0) {
+        _orig_RegisterNatives = jni_functions->RegisterNatives;
+        jni_functions->RegisterNatives = RegisterNativesHook;
+        jvmti->SetJNIFunctionTable(jni_functions);
+
+        // Trace Unsafe.registerNatives() to find the original address of Unsafe.park() native  
+        env->CallStaticVoidMethod(_UnsafeClass, register_natives);
+
+        jni_functions->RegisterNatives = _orig_RegisterNatives;
+        jvmti->SetJNIFunctionTable(jni_functions);
+    }
+
+    _LockSupport = (jclass)env->NewGlobalRef(env->FindClass("java/util/concurrent/locks/LockSupport"));
+    _getBlocker = env->GetStaticMethodID(_LockSupport, "getBlocker", "(Ljava/lang/Thread;)Ljava/lang/Object;");
+
+    env->ExceptionClear();
+    _initialized = true;
+}
+
 void JNICALL LockTracer::MonitorContendedEnter(jvmtiEnv* jvmti, JNIEnv* env, jthread thread, jobject object) {
-    jlong enter_time = OS::nanotime();
+    jlong enter_time = TSC::ticks();
    jvmti->SetTag(thread, enter_time);
 }

 void JNICALL LockTracer::MonitorContendedEntered(jvmtiEnv* jvmti, JNIEnv* env, jthread thread, jobject object) {
-    jlong entered_time = OS::nanotime();
+    jlong entered_time = TSC::ticks();
    jlong enter_time;
    jvmti->GetTag(thread, &enter_time);

    // Time is meaningless if lock attempt has started before profiling
-    if (_enabled && enter_time >= _start_time) {
+    if (_enabled && entered_time - enter_time >= _threshold && enter_time >= _start_time) {
        char* lock_name = getLockName(jvmti, env, object);
        recordContendedLock(BCI_LOCK, enter_time, entered_time, lock_name, object, 0);
        jvmti->Deallocate((unsigned char*)lock_name);
    }
 }

-void JNICALL LockTracer::UnsafeParkTrap(JNIEnv* env, jobject instance, jboolean isAbsolute, jlong time) {
+jint JNICALL LockTracer::RegisterNativesHook(JNIEnv* env, jclass cls, const JNINativeMethod* methods, jint nMethods) {
+    if (env->IsSameObject(cls, _UnsafeClass)) {
+        for (jint i = 0; i < nMethods; i++) {
+            if (strcmp(methods[i].name, "park") == 0 && strcmp(methods[i].signature, "(ZJ)V") == 0) {
+                _orig_Unsafe_park = (UnsafeParkFunc)methods[i].fnPtr;
+                break;
+            } 
+        }
+        return 0;
+    }
+    return _orig_RegisterNatives(env, cls, methods, nMethods);
+}
+
+void JNICALL LockTracer::UnsafeParkHook(JNIEnv* env, jobject instance, jboolean isAbsolute, jlong time) {
    jvmtiEnv* jvmti = VM::jvmti();
    jobject park_blocker = _enabled ? getParkBlocker(jvmti, env) : NULL;
    jlong park_start_time, park_end_time;

    if (park_blocker != NULL) {
-        park_start_time = OS::nanotime();
+        park_start_time = TSC::ticks();
    }

-    VMStructs::_unsafe_park(env, instance, isAbsolute, time);
+    _orig_Unsafe_park(env, instance, isAbsolute, time);

    if (park_blocker != NULL) {
-        park_end_time = OS::nanotime();
-
-        char* lock_name = getLockName(jvmti, env, park_blocker);
-        if (lock_name == NULL || isConcurrentLock(lock_name)) {
-            recordContendedLock(BCI_PARK, park_start_time, park_end_time, lock_name, park_blocker, time);
+        park_end_time = TSC::ticks();
+        if (park_end_time - park_start_time >= _threshold) {
+            char* lock_name = getLockName(jvmti, env, park_blocker);
+            if (lock_name == NULL || isConcurrentLock(lock_name)) {
+                recordContendedLock(BCI_PARK, park_start_time, park_end_time, lock_name, park_blocker, time);
+            }
+            jvmti->Deallocate((unsigned char*)lock_name);
        }
-        jvmti->Deallocate((unsigned char*)lock_name);
    }
 }

@@ -134,26 +190,20 @@ void LockTracer::recordContendedLock(int event_type, u64 start_time, u64 end_tim

    if (lock_name != NULL) {
        if (lock_name[0] == 'L') {
-            event._class_id = Profiler::_instance.classMap()->lookup(lock_name + 1, strlen(lock_name) - 2);
+            event._class_id = Profiler::instance()->classMap()->lookup(lock_name + 1, strlen(lock_name) - 2);
        } else {
-            event._class_id = Profiler::_instance.classMap()->lookup(lock_name);
+            event._class_id = Profiler::instance()->classMap()->lookup(lock_name);
        }
    }

-    Profiler::_instance.recordSample(NULL, end_time - start_time, event_type, &event);
+    u64 duration_nanos = (u64)((end_time - start_time) * _ticks_to_nanos);
+    Profiler::instance()->recordSample(NULL, duration_nanos, event_type, &event);
 }

 void LockTracer::bindUnsafePark(UnsafeParkFunc entry) {
    JNIEnv* env = VM::jni();
-
-    // Try JDK 9+ package first, then fallback to JDK 8 package
-    jclass unsafe = env->FindClass("jdk/internal/misc/Unsafe");
-    if (unsafe == NULL) unsafe = env->FindClass("sun/misc/Unsafe");
-
-    if (unsafe != NULL) {
-        const JNINativeMethod unsafe_park = {(char*)"park", (char*)"(ZJ)V", (void*)entry};
-        env->RegisterNatives(unsafe, &unsafe_park, 1);
+    const JNINativeMethod park = {(char*)"park", (char*)"(ZJ)V", (void*)entry};
+    if (env->RegisterNatives(_UnsafeClass, &park, 1) != 0) {
+        env->ExceptionClear();
    }
-
-    env->ExceptionClear();
 }
--- a/src/lockTracer.h
+++ b/src/lockTracer.h
@@ -22,13 +22,26 @@
 #include "engine.h"


+typedef jint (JNICALL *RegisterNativesFunc)(JNIEnv*, jclass, const JNINativeMethod*, jint);
 typedef void (JNICALL *UnsafeParkFunc)(JNIEnv*, jobject, jboolean, jlong);

 class LockTracer : public Engine {
  private:
+    static double _ticks_to_nanos;
+    static jlong _threshold;
    static jlong _start_time;
+    static jclass _UnsafeClass;
    static jclass _LockSupport;
    static jmethodID _getBlocker;
+    static bool _initialized;
+
+    static void initialize();
+
+    static RegisterNativesFunc _orig_RegisterNatives;
+    static jint JNICALL RegisterNativesHook(JNIEnv* env, jclass cls, const JNINativeMethod* methods, jint nMethods);
+
+    static UnsafeParkFunc _orig_Unsafe_park;
+    static void JNICALL UnsafeParkHook(JNIEnv* env, jobject instance, jboolean isAbsolute, jlong time);

    static jobject getParkBlocker(jvmtiEnv* jvmti, JNIEnv* env);
    static char* getLockName(jvmtiEnv* jvmti, JNIEnv* env, jobject lock);
@@ -38,24 +51,19 @@ class LockTracer : public Engine {
    static void bindUnsafePark(UnsafeParkFunc entry);

  public:
-    const char* name() {
-        return "lock";
+    const char* title() {
+        return "Lock profile";
    }

    const char* units() {
        return "ns";
    }

-    CStack cstack() {
-        return CSTACK_NO;
-    }
-
    Error start(Arguments& args);
    void stop();

    static void JNICALL MonitorContendedEnter(jvmtiEnv* jvmti, JNIEnv* env, jthread thread, jobject object);
    static void JNICALL MonitorContendedEntered(jvmtiEnv* jvmti, JNIEnv* env, jthread thread, jobject object);
-    static void JNICALL UnsafeParkTrap(JNIEnv* env, jobject instance, jboolean isAbsolute, jlong time);
 };

 #endif // _LOCKTRACER_H
--- a/src/log.cpp
+++ b/src/log.cpp
@@ -0,0 +1,127 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <string.h>
+#include "log.h"
+#include "profiler.h"
+
+
+const char* const Log::LEVEL_NAME[] = {
+    "TRACE",
+    "DEBUG",
+    "INFO",
+    "WARN",
+    "ERROR",
+    "NONE"
+};
+
+FILE* Log::_file = stdout;
+LogLevel Log::_level = LOG_TRACE;
+
+
+void Log::open(Arguments& args) {
+    open(args._log, args._loglevel);
+
+    if (args._unknown_arg != NULL) {
+       warn("Unknown argument: %s", args._unknown_arg);
+    }
+}
+
+void Log::open(const char* file_name, const char* level) {
+    if (_file != stdout && _file != stderr) {
+        fclose(_file);
+    }
+
+    if (file_name == NULL || strcmp(file_name, "stdout") == 0) {
+        _file = stdout;
+    } else if (strcmp(file_name, "stderr") == 0) {
+        _file = stderr;
+    } else if ((_file = fopen(file_name, "w")) == NULL) {
+        _file = stdout;
+        warn("Could not open log file: %s", file_name);
+    }
+
+    LogLevel l = LOG_TRACE;
+    if (level != NULL) {
+        for (int i = LOG_TRACE; i <= LOG_NONE; i++) {
+            if (strcasecmp(LEVEL_NAME[i], level) == 0) {
+                l = (LogLevel)i;
+                break;
+            }
+        }
+    }
+    __atomic_store_n(&_level, l, __ATOMIC_RELEASE);
+}
+
+void Log::close() {
+    if (_file != stdout && _file != stderr) {
+        fclose(_file);
+        _file = stdout;
+    }
+}
+
+void Log::log(LogLevel level, const char* msg, va_list args) {
+    char buf[1024];
+    size_t len = vsnprintf(buf, sizeof(buf), msg, args);
+    if (len >= sizeof(buf)) {
+        len = sizeof(buf) - 1;
+        buf[len] = 0;
+    }
+
+    if (level < LOG_ERROR) {
+        Profiler::instance()->writeLog(level, buf, len);
+    }
+
+    if (level >= _level) {
+        fprintf(_file, "[%s] %s\n", LEVEL_NAME[level], buf);
+        fflush(_file);
+    }
+}
+
+void Log::trace(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    log(LOG_TRACE, msg, args);
+    va_end(args);
+}
+
+void Log::debug(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    log(LOG_DEBUG, msg, args);
+    va_end(args);
+}
+
+void Log::info(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    log(LOG_INFO, msg, args);
+    va_end(args);
+}
+
+void Log::warn(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    log(LOG_WARN, msg, args);
+    va_end(args);
+}
+
+void Log::error(const char* msg, ...) {
+    va_list args;
+    va_start(args, msg);
+    log(LOG_ERROR, msg, args);
+    va_end(args);
+}
--- a/src/log.h
+++ b/src/log.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _LOG_H
+#define _LOG_H
+
+#include <stdarg.h>
+#include <stdio.h>
+
+#ifdef __GNUC__
+#define ATTR_FORMAT __attribute__((format(printf, 1, 2)))
+#else
+#define ATTR_FORMAT
+#endif
+
+
+enum LogLevel {
+    LOG_TRACE,
+    LOG_DEBUG,
+    LOG_INFO,
+    LOG_WARN,
+    LOG_ERROR,
+    LOG_NONE
+};
+
+
+class Arguments;
+
+class Log {
+  private:
+    static FILE* _file;
+    static LogLevel _level;
+
+  public:
+    static const char* const LEVEL_NAME[];
+
+    static void open(Arguments& args);
+    static void open(const char* file_name, const char* level);
+    static void close();
+
+    static void log(LogLevel level, const char* msg, va_list args);
+
+    static void ATTR_FORMAT trace(const char* msg, ...);
+    static void ATTR_FORMAT debug(const char* msg, ...);
+    static void ATTR_FORMAT info(const char* msg, ...);
+    static void ATTR_FORMAT warn(const char* msg, ...);
+    static void ATTR_FORMAT error(const char* msg, ...);
+};
+
+#endif // _LOG_H
--- a/src/objectSampler.cpp
+++ b/src/objectSampler.cpp
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <string.h>
+#include "objectSampler.h"
+#include "profiler.h"
+
+
+u64 ObjectSampler::_interval;
+volatile u64 ObjectSampler::_allocated_bytes;
+
+
+void ObjectSampler::SampledObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                       jobject object, jclass object_klass, jlong size) {
+    if (_enabled) {
+        recordAllocation(jvmti, BCI_ALLOC, object_klass, size);
+    }
+}
+
+void ObjectSampler::recordAllocation(jvmtiEnv* jvmti, int event_type, jclass object_klass, jlong size) {
+    AllocEvent event;
+    event._class_id = 0;
+    event._total_size = size > _interval ? size : _interval;
+    event._instance_size = size;
+
+    char* class_name;
+    if (jvmti->GetClassSignature(object_klass, &class_name, NULL) == 0) {
+        if (class_name[0] == 'L') {
+            event._class_id = Profiler::instance()->classMap()->lookup(class_name + 1, strlen(class_name) - 2);
+        } else {
+            event._class_id = Profiler::instance()->classMap()->lookup(class_name);
+        }
+        jvmti->Deallocate((unsigned char*)class_name);
+    }
+
+    Profiler::instance()->recordSample(NULL, size, event_type, &event);
+}
+
+Error ObjectSampler::check(Arguments& args) {
+    if (!VM::canSampleObjects()) {
+        return Error("SampledObjectAlloc is not supported on this JVM");
+    }
+    return Error::OK;
+}
+
+Error ObjectSampler::start(Arguments& args) {
+    Error error = check(args);
+    if (error) {
+        return error;
+    }
+
+    _interval = args._alloc > 0 ? args._alloc : DEFAULT_ALLOC_INTERVAL;
+
+    jvmtiEnv* jvmti = VM::jvmti();
+    jvmti->SetHeapSamplingInterval(_interval);
+    jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_SAMPLED_OBJECT_ALLOC, NULL);
+
+    return Error::OK;
+}
+
+void ObjectSampler::stop() {
+    jvmtiEnv* jvmti = VM::jvmti();
+    jvmti->SetEventNotificationMode(JVMTI_DISABLE, JVMTI_EVENT_SAMPLED_OBJECT_ALLOC, NULL);
+}
--- a/src/objectSampler.h
+++ b/src/objectSampler.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _OBJECTSAMPLER_H
+#define _OBJECTSAMPLER_H
+
+#include <jvmti.h>
+#include "arch.h"
+#include "engine.h"
+
+
+class ObjectSampler : public Engine {
+  protected:
+    static u64 _interval;
+    static volatile u64 _allocated_bytes;
+
+    static void recordAllocation(jvmtiEnv* jvmti, int event_type, jclass object_klass, jlong size);
+
+  public:
+    const char* title() {
+        return "Allocation profile";
+    }
+
+    const char* units() {
+        return "bytes";
+    }
+
+    Error check(Arguments& args);
+    Error start(Arguments& args);
+    void stop();
+
+    static void JNICALL SampledObjectAlloc(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread,
+                                           jobject object, jclass object_klass, jlong size);
+};
+
+#endif // _OBJECTSAMPLER_H
--- a/src/os.h
+++ b/src/os.h
@@ -19,9 +19,17 @@

 #include <signal.h>
 #include <stddef.h>
+#include <sys/types.h>
 #include "arch.h"


+typedef void (*SigAction)(int, siginfo_t*, void*);
+typedef void (*SigHandler)(int);
+typedef void (*TimerCallback)(void*);
+
+// Interrupt threads with this signal. The same signal is used inside JDK to interrupt I/O operations.
+const int WAKEUP_SIGNAL = SIGIO;
+
 enum ThreadState {
    THREAD_INVALID,
    THREAD_RUNNING,
@@ -29,10 +37,6 @@ enum ThreadState {
 };


-class Timer {
-};
-
-
 class ThreadList {
  public:
    virtual ~ThreadList() {}
@@ -42,16 +46,27 @@ class ThreadList {
 };


-class OS {
+// W^X memory support
+class JitWriteProtection {
  private:
-    typedef void (*SigAction)(int, siginfo_t*, void*);
-    typedef void (*SigHandler)(int);
-    typedef void (*TimerCallback)(void*);
+    u64 _prev;
+    bool _restore;

  public:
+    JitWriteProtection(bool enable);
+    ~JitWriteProtection();
+};
+
+
+class OS {
+  public:
+    static const size_t page_size;
+    static const size_t page_mask;
+
    static u64 nanotime();
-    static u64 millis();
+    static u64 micros();
    static u64 processStartTime();
+    static void sleep(u64 nanos);

    static u64 hton64(u64 x);
    static u64 ntoh64(u64 x);
@@ -59,24 +74,26 @@ class OS {
    static int getMaxThreadId();
    static int processId();
    static int threadId();
+    static const char* schedPolicy(int thread_id);
    static bool threadName(int thread_id, char* name_buf, size_t name_len);
    static ThreadState threadState(int thread_id);
    static ThreadList* listThreads();

    static bool isJavaLibraryVisible();

-    static void installSignalHandler(int signo, SigAction action, SigHandler handler = NULL);
+    static SigAction installSignalHandler(int signo, SigAction action, SigHandler handler = NULL);
+    static SigAction replaceCrashHandler(SigAction action);
    static bool sendSignalToThread(int thread_id, int signo);

    static void* safeAlloc(size_t size);
    static void safeFree(void* addr, size_t size);

-    static Timer* startTimer(u64 interval, TimerCallback callback, void* arg);
-    static void stopTimer(Timer* timer);
-
    static bool getCpuDescription(char* buf, size_t size);
    static u64 getProcessCpuTime(u64* utime, u64* stime);
    static u64 getTotalCpuTime(u64* utime, u64* stime);
+
+    static void copyFile(int src_fd, int dst_fd, off_t offset, size_t size);
+    static void freePageCache(int fd, off_t start_offset);
 };

 #endif // _OS_H
--- a/src/os_linux.cpp
+++ b/src/os_linux.cpp
@@ -20,10 +20,12 @@
 #include <byteswap.h>
 #include <dirent.h>
 #include <fcntl.h>
+#include <sched.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/sendfile.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <sys/time.h>
@@ -107,16 +109,28 @@ class LinuxThreadList : public ThreadList {
 };


-u64 OS::nanotime() {
-    struct timespec tp;
-    clock_gettime(CLOCK_MONOTONIC, &tp);
-    return (u64)tp.tv_sec * 1000000000 + tp.tv_nsec;
+JitWriteProtection::JitWriteProtection(bool enable) {
+    // Not used on Linux
 }

-u64 OS::millis() {
+JitWriteProtection::~JitWriteProtection() {
+    // Not used on Linux
+}
+
+
+const size_t OS::page_size = sysconf(_SC_PAGESIZE);
+const size_t OS::page_mask = OS::page_size - 1;
+
+u64 OS::nanotime() {
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    return (u64)ts.tv_sec * 1000000000 + ts.tv_nsec;
+}
+
+u64 OS::micros() {
    struct timeval tv;
    gettimeofday(&tv, NULL);
-    return (u64)tv.tv_sec * 1000 + tv.tv_usec / 1000;
+    return (u64)tv.tv_sec * 1000000 + tv.tv_usec;
 }

 u64 OS::processStartTime() {
@@ -135,6 +149,11 @@ u64 OS::processStartTime() {
    return start_time;
 }

+void OS::sleep(u64 nanos) {
+    struct timespec ts = {(time_t)(nanos / 1000000000), (long)(nanos % 1000000000)};
+    nanosleep(&ts, NULL);
+}
+
 u64 OS::hton64(u64 x) {
    return htonl(1) == 1 ? x : bswap_64(x);
 }
@@ -164,6 +183,14 @@ int OS::threadId() {
    return syscall(__NR_gettid);
 }

+const char* OS::schedPolicy(int thread_id) {
+    int sched_policy = sched_getscheduler(thread_id);
+    if (sched_policy >= SCHED_BATCH) {
+        return sched_policy >= SCHED_IDLE ? "SCHED_IDLE" : "SCHED_BATCH"; 
+    }
+    return "SCHED_OTHER";
+}
+
 bool OS::threadName(int thread_id, char* name_buf, size_t name_len) {
    char buf[64];
    sprintf(buf, "/proc/self/task/%d/comm", thread_id);
@@ -208,8 +235,9 @@ bool OS::isJavaLibraryVisible() {
    return false;
 }

-void OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
+SigAction OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
    struct sigaction sa;
+    struct sigaction oldsa;
    sigemptyset(&sa.sa_mask);

    if (handler != NULL) {
@@ -220,7 +248,17 @@ void OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
        sa.sa_flags = SA_SIGINFO | SA_RESTART;
    }

-    sigaction(signo, &sa, NULL);
+    sigaction(signo, &sa, &oldsa);
+    return oldsa.sa_sigaction;
+}
+
+SigAction OS::replaceCrashHandler(SigAction action) {
+    struct sigaction sa;
+    sigaction(SIGSEGV, NULL, &sa);
+    SigAction old_action = sa.sa_sigaction;
+    sa.sa_sigaction = action;
+    sigaction(SIGSEGV, &sa, NULL);
+    return old_action;
 }

 bool OS::sendSignalToThread(int thread_id, int signo) {
@@ -241,30 +279,6 @@ void OS::safeFree(void* addr, size_t size) {
    syscall(__NR_munmap, addr, size);
 }

-Timer* OS::startTimer(u64 interval, TimerCallback callback, void* arg) {
-    struct sigevent sev;
-    sev.sigev_notify = SIGEV_THREAD;
-    sev.sigev_value.sival_ptr = arg;
-    sev.sigev_notify_function = (void (*)(union sigval)) callback;
-    sev.sigev_notify_attributes = NULL;
-
-    timer_t timer;
-    if (timer_create(CLOCK_MONOTONIC, &sev, &timer) != 0) {
-        return NULL;
-    }
-
-    struct itimerspec spec;
-    spec.it_interval.tv_sec = spec.it_value.tv_sec = interval / 1000000000;
-    spec.it_interval.tv_nsec = spec.it_value.tv_nsec = interval % 1000000000;
-    timer_settime(timer, 0, &spec, NULL);
-
-    return (Timer*)timer;
-}
-
-void OS::stopTimer(Timer* timer) {
-    timer_delete((timer_t)timer);
-}
-
 bool OS::getCpuDescription(char* buf, size_t size) {
    int fd = open("/proc/cpuinfo", O_RDONLY);
    if (fd == -1) {
@@ -316,4 +330,19 @@ u64 OS::getTotalCpuTime(u64* utime, u64* stime) {
    return real;
 }

+void OS::copyFile(int src_fd, int dst_fd, off_t offset, size_t size) {
+    // copy_file_range() is probably better, but not supported on all kernels
+    while (size > 0) {
+        ssize_t bytes = sendfile(dst_fd, src_fd, &offset, size);
+        if (bytes <= 0) {
+            break;
+        }
+        size -= (size_t)bytes;
+    }
+}
+
+void OS::freePageCache(int fd, off_t start_offset) {
+    posix_fadvise(fd, start_offset & ~page_mask, 0, POSIX_FADV_DONTNEED);
+}
+
 #endif // __linux__
--- a/src/os_macos.cpp
+++ b/src/os_macos.cpp
@@ -16,7 +16,6 @@

 #ifdef __APPLE__

-#include <dispatch/dispatch.h>
 #include <libkern/OSByteOrder.h>
 #include <libproc.h>
 #include <mach/mach.h>
@@ -28,6 +27,8 @@
 #include <sys/sysctl.h>
 #include <sys/time.h>
 #include <sys/times.h>
+#include <time.h>
+#include <unistd.h>
 #include "os.h"


@@ -81,6 +82,39 @@ class MacThreadList : public ThreadList {
 };


+JitWriteProtection::JitWriteProtection(bool enable) {
+#ifdef __aarch64__
+    // Mimic pthread_jit_write_protect_np(), but save the previous state
+    u64 val = enable ? *(volatile u64*)0xfffffc118 : *(volatile u64*)0xfffffc110;
+    u64 prev;
+    asm volatile("mrs %0, s3_6_c15_c1_5" : "=r" (prev) : : );
+    if (prev != val) {
+        _prev = prev;
+        _restore = true;
+        asm volatile("msr s3_6_c15_c1_5, %0\n"
+                     "isb"
+                     : "+r" (val) : : "memory");
+    } else {
+        _restore = false;
+    }
+#endif
+}
+
+JitWriteProtection::~JitWriteProtection() {
+#ifdef __aarch64__
+    if (_restore) {
+        u64 prev = _prev;
+        asm volatile("msr s3_6_c15_c1_5, %0\n"
+                     "isb"
+                     : "+r" (prev) : : "memory");
+    }
+#endif
+}
+
+
+const size_t OS::page_size = sysconf(_SC_PAGESIZE);
+const size_t OS::page_mask = OS::page_size - 1;
+
 static mach_timebase_info_data_t timebase = {0, 0};

 u64 OS::nanotime() {
@@ -90,10 +124,15 @@ u64 OS::nanotime() {
    return (u64)mach_absolute_time() * timebase.numer / timebase.denom;
 }

-u64 OS::millis() {
+u64 OS::micros() {
    struct timeval tv;
    gettimeofday(&tv, NULL);
-    return (u64)tv.tv_sec * 1000 + tv.tv_usec / 1000;
+    return (u64)tv.tv_sec * 1000000 + tv.tv_usec;
+}
+
+void OS::sleep(u64 nanos) {
+    struct timespec ts = {(time_t)(nanos / 1000000000), (long)(nanos % 1000000000)};
+    nanosleep(&ts, NULL);
 }

 u64 OS::processStartTime() {
@@ -135,6 +174,11 @@ int OS::threadId() {
    return (int)port;
 }

+const char* OS::schedPolicy(int thread_id) {
+    // Not used on macOS
+    return "SCHED_OTHER";
+}
+
 bool OS::threadName(int thread_id, char* name_buf, size_t name_len) {
    pthread_t thread = pthread_from_mach_thread_np(thread_id);
    return thread && pthread_getname_np(thread, name_buf, name_len) == 0 && name_buf[0] != 0;
@@ -157,8 +201,9 @@ bool OS::isJavaLibraryVisible() {
    return true;
 }

-void OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
+SigAction OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
    struct sigaction sa;
+    struct sigaction oldsa;
    sigemptyset(&sa.sa_mask);

    if (handler != NULL) {
@@ -169,16 +214,37 @@ void OS::installSignalHandler(int signo, SigAction action, SigHandler handler) {
        sa.sa_flags = SA_SIGINFO | SA_RESTART;
    }

-    sigaction(signo, &sa, NULL);
+    sigaction(signo, &sa, &oldsa);
+    return oldsa.sa_sigaction;
+}
+
+SigAction OS::replaceCrashHandler(SigAction action) {
+    struct sigaction sa;
+    sigaction(SIGBUS, NULL, &sa);
+    SigAction old_action = sa.sa_sigaction;
+    sa.sa_sigaction = action;
+    sigaction(SIGBUS, &sa, NULL);
+    return old_action;
 }

 bool OS::sendSignalToThread(int thread_id, int signo) {
-   int result;
-   asm volatile("syscall"
-                : "=a" (result)
-                : "a" (0x2000148), "D" (thread_id), "S" (signo)
-                : "rcx", "r11", "memory");
-   return result == 0;
+#ifdef __aarch64__
+    register long x0 asm("x0") = thread_id;
+    register long x1 asm("x1") = signo;
+    register long x16 asm("x16") = 328;
+    asm volatile("svc #0x80"
+                 : "+r" (x0)
+                 : "r" (x1), "r" (x16)
+                 : "memory");
+    return x0 == 0;
+#else
+    int result;
+    asm volatile("syscall"
+                 : "=a" (result)
+                 : "a" (0x2000148), "D" (thread_id), "S" (signo)
+                 : "rcx", "r11", "memory");
+    return result == 0;
+#endif
 }

 void* OS::safeAlloc(size_t size) {
@@ -195,26 +261,6 @@ void OS::safeFree(void* addr, size_t size) {
    munmap(addr, size);
 }

-Timer* OS::startTimer(u64 interval, TimerCallback callback, void* arg) {
-    dispatch_queue_t queue = dispatch_get_global_queue(QOS_CLASS_UTILITY, 0);
-    dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
-    if (source != NULL) {
-        dispatch_source_set_timer(source, dispatch_time(DISPATCH_TIME_NOW, interval), interval, 0);
-        dispatch_source_set_event_handler_f(source, callback);
-        dispatch_set_context(source, arg);
-        dispatch_resume(source);
-    }
-    return (Timer*)source;
-}
-
-void OS::stopTimer(Timer* timer) {
-    dispatch_source_t source = (dispatch_source_t)timer;
-    if (source != NULL) {
-        dispatch_source_cancel(source);
-        dispatch_release(source);
-    }
-}
-
 bool OS::getCpuDescription(char* buf, size_t size) {
    return sysctlbyname("machdep.cpu.brand_string", buf, &size, NULL, 0) == 0;
 }
@@ -255,4 +301,26 @@ u64 OS::getTotalCpuTime(u64* utime, u64* stime) {
    return user + system + idle;
 }

+void OS::copyFile(int src_fd, int dst_fd, off_t offset, size_t size) {
+    char* buf = (char*)mmap(NULL, size + offset, PROT_READ, MAP_PRIVATE, src_fd, 0);
+    if (buf == NULL) {
+        return;
+    }
+
+    while (size > 0) {
+        ssize_t bytes = write(dst_fd, buf + offset, size < 262144 ? size : 262144);
+        if (bytes <= 0) {
+            break;
+        }
+        offset += (size_t)bytes;
+        size -= (size_t)bytes;
+    }
+
+    munmap(buf, offset);
+}
+
+void OS::freePageCache(int fd, off_t start_offset) {
+    // Not supported on macOS
+}
+
 #endif // __APPLE__
--- a/src/perfEvents.h
+++ b/src/perfEvents.h
@@ -18,11 +18,13 @@
 #define _PERFEVENTS_H

 #include <signal.h>
+#include "arch.h"
 #include "engine.h"


 class PerfEvent;
 class PerfEventType;
+class StackContext;

 class PerfEvents : public Engine {
  private:
@@ -32,28 +34,27 @@ class PerfEvents : public Engine {
    static long _interval;
    static Ring _ring;
    static CStack _cstack;
-    static bool _print_extended_warning;
+    static bool _use_mmap_page;

+    static u64 readCounter(siginfo_t* siginfo, void* ucontext);
    static void signalHandler(int signo, siginfo_t* siginfo, void* ucontext);
+    static void signalHandlerJ9(int signo, siginfo_t* siginfo, void* ucontext);

  public:
-    const char* name() {
-        return "perf";
-    }
-
-    const char* units();
-
    Error check(Arguments& args);
    Error start(Arguments& args);
    void stop();

-    int getNativeTrace(void* ucontext, int tid, const void** callchain, int max_depth,
-                       CodeCache* java_methods, CodeCache* runtime_stubs);
+    const char* title();
+    const char* units();
+
+    static int walk(int tid, void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx);
+    static void resetBuffer(int tid);

    static bool supported();
    static const char* getEventName(int event_id);

-    static bool createForThread(int tid);
+    static int createForThread(int tid);
    static void destroyForThread(int tid);
 };

--- a/src/perfEvents_linux.cpp
+++ b/src/perfEvents_linux.cpp
@@ -25,18 +25,24 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <errno.h>
+#include <pthread.h>
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
 #include <linux/perf_event.h>
 #include "arch.h"
+#include "j9StackTraces.h"
+#include "log.h"
 #include "os.h"
 #include "perfEvents.h"
+#include "fdtransferClient.h"
 #include "profiler.h"
 #include "spinLock.h"
 #include "stackFrame.h"
+#include "stackWalker.h"
 #include "symbols.h"
+#include "vmStructs.h"


 // Ancient fcntl.h does not define F_SETOWN_EX constants and structures
@@ -59,7 +65,18 @@ enum {
 };


-static const unsigned long PERF_PAGE_SIZE = sysconf(_SC_PAGESIZE);
+static int fetchInt(const char* file_name) {
+    int fd = open(file_name, O_RDONLY);
+    if (fd == -1) {
+        return 0;
+    }
+
+    char num[16] = "0";
+    ssize_t r = read(fd, num, sizeof(num) - 1);
+    (void) r;
+    close(fd);
+    return atoi(num);
+}

 // Get perf_event_attr.config numeric value of the given tracepoint name
 // by reading /sys/kernel/debug/tracing/events/<name>/id file
@@ -71,16 +88,94 @@ static int findTracepointId(const char* name) {

    *strchr(buf, ':') = '/';  // make path from event name

+    return fetchInt(buf);
+}
+
+// Get perf_event_attr.type for the given event source
+// by reading /sys/bus/event_source/devices/<name>/type
+static int findDeviceType(const char* name) {
+    char buf[256];
+    if ((size_t)snprintf(buf, sizeof(buf), "/sys/bus/event_source/devices/%s/type", name) >= sizeof(buf)) {
+        return 0;
+    }
+    return fetchInt(buf);
+}
+
+// Convert pmu/event-name/ to pmu/param1=N,param2=M/
+static void resolvePmuEventName(const char* device, char* event, size_t size) {
+    char buf[256];
+    if ((size_t)snprintf(buf, sizeof(buf), "/sys/bus/event_source/devices/%s/events/%s", device, event) >= sizeof(buf)) {
+        return;
+    }
+
    int fd = open(buf, O_RDONLY);
    if (fd == -1) {
+        return;
+    }
+
+    ssize_t r = read(fd, event, size);
+    if (r > 0 && (r == size || event[r - 1] == '\n')) {
+        event[r - 1] = 0;
+    }
+    close(fd);
+}
+
+// Set a PMU parameter (such as umask) to the corresponding config field
+static bool setPmuConfig(const char* device, const char* param, __u64* config, __u64 val) {
+    char buf[256];
+    if ((size_t)snprintf(buf, sizeof(buf), "/sys/bus/event_source/devices/%s/format/%s", device, param) >= sizeof(buf)) {
+        return false;
+    }
+
+    int fd = open(buf, O_RDONLY);
+    if (fd == -1) {
+        return false;
+    }
+
+    ssize_t r = read(fd, buf, sizeof(buf));
+    close(fd);
+
+    if (r > 0 && r < sizeof(buf)) {
+        if (strncmp(buf, "config:", 7) == 0) {
+            config[0] |= val << atoi(buf + 7);
+            return true;
+        } else if (strncmp(buf, "config1:", 8) == 0) {
+            config[1] |= val << atoi(buf + 8);
+            return true;
+        } else if (strncmp(buf, "config2:", 8) == 0) {
+            config[2] |= val << atoi(buf + 8);
+            return true;
+        }
+    }
+    return false;
+}
+
+
+static void** _pthread_entry = NULL;
+
+// Intercept thread creation/termination by patching libjvm's GOT entry for pthread_setspecific().
+// HotSpot puts VMThread into TLS on thread start, and resets on thread end.
+static int pthread_setspecific_hook(pthread_key_t key, const void* value) {
+    if (key != VMThread::key()) {
+        return pthread_setspecific(key, value);
+    }
+    if (pthread_getspecific(key) == value) {
        return 0;
    }

-    char id[16] = "0";
-    ssize_t r = read(fd, id, sizeof(id) - 1);
-    (void) r;
-    close(fd);
-    return atoi(id);
+    if (value != NULL) {
+        int result = pthread_setspecific(key, value);
+        PerfEvents::createForThread(OS::threadId());
+        return result;
+    } else {
+        PerfEvents::destroyForThread(OS::threadId());
+        return pthread_setspecific(key, value);
+    }
+}
+
+static void** lookupThreadEntry() {
+    CodeCache* lib = Profiler::instance()->findJvmLibrary("libj9thr");
+    return lib != NULL ? lib->findGlobalOffsetEntry((void*)&pthread_setspecific) : NULL;
 }


@@ -94,13 +189,25 @@ struct PerfEventType {
    long default_interval;
    __u32 type;
    __u64 config;
-    __u32 bp_type;
-    __u32 bp_len;
+    __u64 config1;
+    __u64 config2;
    int counter_arg;

+    enum {
+        IDX_PREDEFINED = 12,
+        IDX_RAW,
+        IDX_PMU,
+        IDX_BREAKPOINT,
+        IDX_TRACEPOINT,
+        IDX_KPROBE,
+        IDX_UPROBE,
+    };
+
    static PerfEventType AVAILABLE_EVENTS[];
    static FunctionWithCounter KNOWN_FUNCTIONS[];

+    static char probe_func[256];
+
    // Find which argument of a known function serves as a profiling counter,
    // e.g. the first argument of malloc() is allocation size
    static int findCounterArg(const char* name) {
@@ -112,22 +219,22 @@ struct PerfEventType {
        return 0;
    }

-    static PerfEventType* findByType(__u32 type) {
-        for (PerfEventType* event = AVAILABLE_EVENTS; ; event++) {
-            if (event->type == type) {
-                return event;
-            }
-        }
-    }
-
-    // Breakpoint format: func[+offset][/len][:rwx]
+    // Breakpoint format: func[+offset][/len][:rwx][{arg}]
    static PerfEventType* getBreakpoint(const char* name, __u32 bp_type, __u32 bp_len) {
        char buf[256];
        strncpy(buf, name, sizeof(buf) - 1);
        buf[sizeof(buf) - 1] = 0;

+        // Parse counter arg [{arg}]
+        int counter_arg = 0;
+        char* c = strrchr(buf, '{');
+        if (c != NULL && c[1] >= '1' && c[1] <= '9') {
+            *c++ = 0;
+            counter_arg = atoi(c);
+        }
+
        // Parse access type [:rwx]
-        char* c = strrchr(buf, ':');
+        c = strrchr(buf, ':');
        if (c != NULL && c != name && c[-1] != ':') {
            *c++ = 0;
            if (strcmp(c, "r") == 0) {
@@ -164,7 +271,11 @@ struct PerfEventType {
        } else {
            addr = (__u64)(uintptr_t)dlsym(RTLD_DEFAULT, buf);
            if (addr == 0) {
-                addr = (__u64)(uintptr_t)Profiler::_instance.resolveSymbol(buf);
+                addr = (__u64)(uintptr_t)Profiler::instance()->resolveSymbol(buf);
+            }
+            if (c == NULL) {
+                // If offset is not specified explicitly, add the default breakpoint offset
+                offset = BREAKPOINT_OFFSET;
            }
        }

@@ -172,21 +283,113 @@ struct PerfEventType {
            return NULL;
        }

-        PerfEventType* breakpoint = findByType(PERF_TYPE_BREAKPOINT);
-        breakpoint->config = addr + offset;
-        breakpoint->bp_type = bp_type;
-        breakpoint->bp_len = bp_len;
-        breakpoint->counter_arg = bp_type == HW_BREAKPOINT_X ? findCounterArg(buf) : 0;
+        PerfEventType* breakpoint = &AVAILABLE_EVENTS[IDX_BREAKPOINT];
+        breakpoint->config = bp_type;
+        breakpoint->config1 = addr + offset;
+        breakpoint->config2 = bp_len;
+        breakpoint->counter_arg = bp_type == HW_BREAKPOINT_X && counter_arg == 0 ? findCounterArg(buf) : counter_arg;
        return breakpoint;
    }

    static PerfEventType* getTracepoint(int tracepoint_id) {
-        PerfEventType* tracepoint = findByType(PERF_TYPE_TRACEPOINT);
+        PerfEventType* tracepoint = &AVAILABLE_EVENTS[IDX_TRACEPOINT];
        tracepoint->config = tracepoint_id;
        return tracepoint;
    }

+    static PerfEventType* getProbe(PerfEventType* probe, const char* type, const char* name, __u64 ret) {
+        strncpy(probe_func, name, sizeof(probe_func) - 1);
+        probe_func[sizeof(probe_func) - 1] = 0;
+
+        if (probe->type == 0 && (probe->type = findDeviceType(type)) == 0) {
+            return NULL;
+        }
+
+        long long offset = 0;
+        char* c = strrchr(probe_func, '+');
+        if (c != NULL) {
+            *c++ = 0;
+            offset = strtoll(c, NULL, 0);
+        }
+
+        probe->config = ret;
+        probe->config1 = (__u64)(uintptr_t)probe_func;
+        probe->config2 = offset;
+        return probe;
+    }
+
+    static PerfEventType* getRawEvent(__u64 config) {
+        PerfEventType* raw = &AVAILABLE_EVENTS[IDX_RAW];
+        raw->config = config;
+        return raw;
+    }
+
+    static PerfEventType* getPmuEvent(const char* name) {
+        char buf[256];
+        strncpy(buf, name, sizeof(buf) - 1);
+        buf[sizeof(buf) - 1] = 0;
+
+        char* descriptor = strchr(buf, '/');
+        *descriptor++ = 0;
+        descriptor[strlen(descriptor) - 1] = 0;
+
+        PerfEventType* raw = &AVAILABLE_EVENTS[IDX_PMU];
+        if ((raw->type = findDeviceType(buf)) == 0) {
+            return NULL;
+        }
+
+        // pmu/rNNN/
+        if (descriptor[0] == 'r' && descriptor[1] >= '0') {
+            char* end;
+            raw->config = strtoull(descriptor + 1, &end, 16);
+            if (*end == 0) {
+                return raw;
+            }
+        }
+
+        // Resolve event name to the list of parameters
+        resolvePmuEventName(buf, descriptor, sizeof(buf) - (descriptor - buf));
+
+        raw->config = 0;
+        raw->config1 = 0;
+        raw->config2 = 0;
+
+        // Parse parameters
+        while (descriptor != NULL && descriptor[0]) {
+            char* p = descriptor;
+            if ((descriptor = strchr(p, ',')) != NULL || (descriptor = strchr(p, ':')) != NULL) {
+                *descriptor++ = 0;
+            }
+
+            __u64 val = 1;
+            char* eq = strchr(p, '=');
+            if (eq != NULL) {
+                *eq++ = 0;
+                val = strtoull(eq, NULL, 0);
+            }
+
+            if (strcmp(p, "config") == 0) {
+                raw->config = val;
+            } else if (strcmp(p, "config1") == 0) {
+                raw->config1 = val;
+            } else if (strcmp(p, "config2") == 0) {
+                raw->config2 = val;
+            } else if (!setPmuConfig(buf, p, &raw->config, val)) {
+                return NULL;
+            }
+        }
+
+        return raw;
+    }
+
    static PerfEventType* forName(const char* name) {
+        // Look through the table of predefined perf events
+        for (int i = 0; i < IDX_PREDEFINED; i++) {
+            if (strcmp(name, AVAILABLE_EVENTS[i].name) == 0) {
+                return &AVAILABLE_EVENTS[i];
+            }
+        }
+
        // Hardware breakpoint
        if (strncmp(name, "mem:", 4) == 0) {
            return getBreakpoint(name + 4, HW_BREAKPOINT_RW, 1);
@@ -198,16 +401,38 @@ struct PerfEventType {
            return tracepoint_id > 0 ? getTracepoint(tracepoint_id) : NULL;
        }

-        // Look through the table of predefined perf events
-        for (PerfEventType* event = AVAILABLE_EVENTS; event->name != NULL; event++) {
-            if (strcmp(name, event->name) == 0) {
-                return event;
+        // kprobe or uprobe
+        if (strncmp(name, "kprobe:", 7) == 0) {
+            return getProbe(&AVAILABLE_EVENTS[IDX_KPROBE], "kprobe", name + 7, 0);
+        }
+        if (strncmp(name, "uprobe:", 7) == 0) {
+            return getProbe(&AVAILABLE_EVENTS[IDX_UPROBE], "uprobe", name + 7, 0);
+        }
+        if (strncmp(name, "kretprobe:", 10) == 0) {
+            return getProbe(&AVAILABLE_EVENTS[IDX_KPROBE], "kprobe", name + 10, 1);
+        }
+        if (strncmp(name, "uretprobe:", 10) == 0) {
+            return getProbe(&AVAILABLE_EVENTS[IDX_UPROBE], "uprobe", name + 10, 1);
+        }
+
+        // Raw PMU register: rNNN
+        if (name[0] == 'r' && name[1] >= '0') {
+            char* end;
+            __u64 reg = strtoull(name + 1, &end, 16);
+            if (*end == 0) {
+                return getRawEvent(reg);
            }
        }

+        // Raw perf event descriptor: pmu/event-descriptor/
+        const char* s = strchr(name, '/');
+        if (s > name && s[1] != 0 && s[strlen(s) - 1] == '/') {
+            return getPmuEvent(name);
+        }
+
        // Kernel tracepoints defined in debugfs
-        const char* c = strchr(name, ':');
-        if (c != NULL && c[1] != ':') {
+        s = strchr(name, ':');
+        if (s != NULL && s[1] != ':') {
            int tracepoint_id = findTracepointId(name);
            if (tracepoint_id > 0) {
                return getTracepoint(tracepoint_id);
@@ -232,7 +457,7 @@ PerfEventType PerfEventType::AVAILABLE_EVENTS[] = {
    {"instructions",          1000000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_INSTRUCTIONS},
    {"cache-references",      1000000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_REFERENCES},
    {"cache-misses",             1000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_CACHE_MISSES},
-    {"branches",              1000000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_INSTRUCTIONS},
+    {"branch-instructions",   1000000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_INSTRUCTIONS},
    {"branch-misses",            1000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_BRANCH_MISSES},
    {"bus-cycles",            1000000, PERF_TYPE_HARDWARE, PERF_COUNT_HW_BUS_CYCLES},

@@ -240,15 +465,20 @@ PerfEventType PerfEventType::AVAILABLE_EVENTS[] = {
    {"LLC-load-misses",          1000, PERF_TYPE_HW_CACHE, LOAD_MISS(PERF_COUNT_HW_CACHE_LL)},
    {"dTLB-load-misses",         1000, PERF_TYPE_HW_CACHE, LOAD_MISS(PERF_COUNT_HW_CACHE_DTLB)},

-    {"mem:breakpoint",              1, PERF_TYPE_BREAKPOINT, 0},
-    {"trace:tracepoint",            1, PERF_TYPE_TRACEPOINT, 0},
+    {"rNNN",                     1000, PERF_TYPE_RAW, 0}, /* IDX_RAW */
+    {"pmu/event-descriptor/",    1000, PERF_TYPE_RAW, 0}, /* IDX_PMU */

-    {NULL}
+    {"mem:breakpoint",              1, PERF_TYPE_BREAKPOINT, 0}, /* IDX_BREAKPOINT */
+    {"trace:tracepoint",            1, PERF_TYPE_TRACEPOINT, 0}, /* IDX_TRACEPOINT */
+
+    {"kprobe:func",                 1, 0, 0}, /* IDX_KPROBE */
+    {"uprobe:path",                 1, 0, 0}, /* IDX_UPROBE */
 };

 FunctionWithCounter PerfEventType::KNOWN_FUNCTIONS[] = {
    {"malloc",   1},
    {"mmap",     2},
+    {"munmap",   2},
    {"read",     3},
    {"write",    3},
    {"send",     3},
@@ -258,6 +488,8 @@ FunctionWithCounter PerfEventType::KNOWN_FUNCTIONS[] = {
    {NULL}
 };

+char PerfEventType::probe_func[256];
+

 class RingBuffer {
  private:
@@ -266,21 +498,21 @@ class RingBuffer {

  public:
    RingBuffer(struct perf_event_mmap_page* page) {
-        _start = (const char*)page + PERF_PAGE_SIZE;
+        _start = (const char*)page + OS::page_size;
    }

    struct perf_event_header* seek(u64 offset) {
-        _offset = (unsigned long)offset & (PERF_PAGE_SIZE - 1);
+        _offset = (unsigned long)offset & OS::page_mask;
        return (struct perf_event_header*)(_start + _offset);
    }

    u64 next() {
-        _offset = (_offset + sizeof(u64)) & (PERF_PAGE_SIZE - 1);
+        _offset = (_offset + sizeof(u64)) & OS::page_mask;
        return *(u64*)(_start + _offset);
    }

    u64 peek(unsigned long words) {
-        unsigned long peek_offset = (_offset + words * sizeof(u64)) & (PERF_PAGE_SIZE - 1);
+        unsigned long peek_offset = (_offset + words * sizeof(u64)) & OS::page_mask;
        return *(u64*)(_start + peek_offset);
    }
 };
@@ -301,17 +533,23 @@ PerfEventType* PerfEvents::_event_type = NULL;
 long PerfEvents::_interval;
 Ring PerfEvents::_ring;
 CStack PerfEvents::_cstack;
-bool PerfEvents::_print_extended_warning;
+bool PerfEvents::_use_mmap_page;

-bool PerfEvents::createForThread(int tid) {
+int PerfEvents::createForThread(int tid) {
    if (tid >= _max_events) {
-        fprintf(stderr, "WARNING: tid[%d] > pid_max[%d]. Restart profiler after changing pid_max\n", tid, _max_events);
-        return false;
+        Log::warn("tid[%d] > pid_max[%d]. Restart profiler after changing pid_max", tid, _max_events);
+        return -1;
    }

    PerfEventType* event_type = _event_type;
    if (event_type == NULL) {
-        return false;
+        return -1;
+    }
+
+    // Mark _events[tid] early to prevent duplicates. Real fd will be put later.
+    if (!__sync_bool_compare_and_swap(&_events[tid]._fd, 0, -1)) {
+        // Lost race. The event is created either from PerfEvents::start() or from pthread hook.
+        return -1;
    }

    struct perf_event_attr attr = {0};
@@ -319,12 +557,12 @@ bool PerfEvents::createForThread(int tid) {
    attr.type = event_type->type;

    if (attr.type == PERF_TYPE_BREAKPOINT) {
-        attr.bp_addr = event_type->config;
-        attr.bp_type = event_type->bp_type;
-        attr.bp_len = event_type->bp_len;
+        attr.bp_type = event_type->config;
    } else {
        attr.config = event_type->config;
    }
+    attr.config1 = event_type->config1;
+    attr.config2 = event_type->config2;

    // Hardware events may not always support zero skid
    if (attr.type == PERF_TYPE_SOFTWARE) {
@@ -342,6 +580,10 @@ bool PerfEvents::createForThread(int tid) {
        attr.exclude_user = 1;
    }

+    if (_cstack == CSTACK_FP || _cstack == CSTACK_DWARF) {
+        attr.exclude_callchain_user = 1;
+    }
+
 #ifdef PERF_ATTR_SIZE_VER5
    if (_cstack == CSTACK_LBR) {
        attr.sample_type |= PERF_SAMPLE_BRANCH_STACK | PERF_SAMPLE_REGS_USER;
@@ -353,31 +595,27 @@ bool PerfEvents::createForThread(int tid) {
 #warning "Compiling without LBR support. Kernel headers 4.1+ required"
 #endif

-    int fd = syscall(__NR_perf_event_open, &attr, tid, -1, -1, 0);
+    int fd;
+    if (FdTransferClient::hasPeer()) {
+        fd = FdTransferClient::requestPerfFd(&tid, &attr);
+    } else {
+        fd = syscall(__NR_perf_event_open, &attr, tid, -1, -1, 0);
+    }
+
    if (fd == -1) {
        int err = errno;
-        perror("perf_event_open failed");
-        if (err == EACCES && _print_extended_warning) {
-            fprintf(stderr, "Due to permission restrictions, you cannot collect kernel events.\n"
-                            "Try with --all-user option, or 'echo 1 > /proc/sys/kernel/perf_event_paranoid'\n");
-            _print_extended_warning = false;
-        }
-        return false;
+        Log::warn("perf_event_open for TID %d failed: %s", tid, strerror(errno));
+        return err;
    }

-    if (!__sync_bool_compare_and_swap(&_events[tid]._fd, 0, fd)) {
-        // Lost race. The event is created either from start() or from onThreadStart()
-        close(fd);
-        return false;
-    }
-
-    void* page = mmap(NULL, 2 * PERF_PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    void* page = _use_mmap_page ? mmap(NULL, 2 * OS::page_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0) : NULL;
    if (page == MAP_FAILED) {
-        perror("perf_event mmap failed");
+        Log::warn("perf_event mmap failed: %s", strerror(errno));
        page = NULL;
    }

    _events[tid].reset();
+    _events[tid]._fd = fd;
    _events[tid]._page = (struct perf_event_mmap_page*)page;

    struct f_owner_ex ex;
@@ -391,7 +629,7 @@ bool PerfEvents::createForThread(int tid) {
    ioctl(fd, PERF_EVENT_IOC_RESET, 0);
    ioctl(fd, PERF_EVENT_IOC_REFRESH, 1);

-    return true;
+    return 0;
 }

 void PerfEvents::destroyForThread(int tid) {
@@ -401,18 +639,31 @@ void PerfEvents::destroyForThread(int tid) {

    PerfEvent* event = &_events[tid];
    int fd = event->_fd;
-    if (fd != 0 && __sync_bool_compare_and_swap(&event->_fd, fd, 0)) {
+    if (fd > 0 && __sync_bool_compare_and_swap(&event->_fd, fd, 0)) {
        ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
        close(fd);
    }
    if (event->_page != NULL) {
        event->lock();
-        munmap(event->_page, 2 * PERF_PAGE_SIZE);
+        munmap(event->_page, 2 * OS::page_size);
        event->_page = NULL;
        event->unlock();
    }
 }

+u64 PerfEvents::readCounter(siginfo_t* siginfo, void* ucontext) {
+    switch (_event_type->counter_arg) {
+        case 1: return StackFrame(ucontext).arg0();
+        case 2: return StackFrame(ucontext).arg1();
+        case 3: return StackFrame(ucontext).arg2();
+        case 4: return StackFrame(ucontext).arg3();
+        default: {
+            u64 counter;
+            return read(siginfo->si_fd, &counter, sizeof(counter)) == sizeof(counter) ? counter : 1;
+        }
+    }
+}
+
 void PerfEvents::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
    if (siginfo->si_code <= 0) {
        // Looks like an external signal; don't treat as a profiling event
@@ -420,41 +671,61 @@ void PerfEvents::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
    }

    if (_enabled) {
-        u64 counter;
-        switch (_event_type->counter_arg) {
-            case 1: counter = StackFrame(ucontext).arg0(); break;
-            case 2: counter = StackFrame(ucontext).arg1(); break;
-            case 3: counter = StackFrame(ucontext).arg2(); break;
-            case 4: counter = StackFrame(ucontext).arg3(); break;
-            default:
-                if (read(siginfo->si_fd, &counter, sizeof(counter)) != sizeof(counter)) {
-                    counter = 1;
-                }
-        }
-
+        u64 counter = readCounter(siginfo, ucontext);
        ExecutionEvent event;
-        Profiler::_instance.recordSample(ucontext, counter, 0, &event);
+        Profiler::instance()->recordSample(ucontext, counter, 0, &event);
+    } else {
+        resetBuffer(OS::threadId());
    }

    ioctl(siginfo->si_fd, PERF_EVENT_IOC_RESET, 0);
    ioctl(siginfo->si_fd, PERF_EVENT_IOC_REFRESH, 1);
 }

-const char* PerfEvents::units() {
-    if (_event_type == NULL || _event_type->name == EVENT_CPU) {
-        return "ns";
-    } else if (_event_type->type == PERF_TYPE_BREAKPOINT || _event_type->type == PERF_TYPE_TRACEPOINT) {
-        return "events";
+void PerfEvents::signalHandlerJ9(int signo, siginfo_t* siginfo, void* ucontext) {
+    if (siginfo->si_code <= 0) {
+        // Looks like an external signal; don't treat as a profiling event
+        return;
    }

-    const char* dash = strrchr(_event_type->name, '-');
-    return dash != NULL ? dash + 1 : _event_type->name;
+    if (_enabled) {
+        u64 counter = readCounter(siginfo, ucontext);
+        J9StackTraceNotification notif;
+        StackContext java_ctx;
+        notif.num_frames = _cstack == CSTACK_NO ? 0 : walk(OS::threadId(), ucontext, notif.addr, MAX_J9_NATIVE_FRAMES, &java_ctx);
+        J9StackTraces::checkpoint(counter, &notif);
+    } else {
+        resetBuffer(OS::threadId());
+    }
+
+    ioctl(siginfo->si_fd, PERF_EVENT_IOC_RESET, 0);
+    ioctl(siginfo->si_fd, PERF_EVENT_IOC_REFRESH, 1);
+}
+
+const char* PerfEvents::title() {
+    if (_event_type == NULL || _event_type->name == EVENT_CPU) {
+        return "CPU profile";
+    } else if (_event_type->type == PERF_TYPE_SOFTWARE || _event_type->type == PERF_TYPE_HARDWARE || _event_type->type == PERF_TYPE_HW_CACHE) {
+        return _event_type->name;
+    } else {
+        return "Flame Graph";
+    }
+}
+
+const char* PerfEvents::units() {
+    return _event_type == NULL || _event_type->name == EVENT_CPU ? "ns" : "total";
 }

 Error PerfEvents::check(Arguments& args) {
-    PerfEventType* event_type = PerfEventType::forName(args._event_desc);
+    PerfEventType* event_type = PerfEventType::forName(args._event);
    if (event_type == NULL) {
        return Error("Unsupported event type");
+    } else if (event_type->counter_arg > 4) {
+        return Error("Only arguments 1-4 can be counted");
+    }
+
+    if (_pthread_entry == NULL && (_pthread_entry = lookupThreadEntry()) == NULL) {
+        return Error("Could not set pthread hook");
    }

    struct perf_event_attr attr = {0};
@@ -462,12 +733,12 @@ Error PerfEvents::check(Arguments& args) {
    attr.type = event_type->type;

    if (attr.type == PERF_TYPE_BREAKPOINT) {
-        attr.bp_addr = event_type->config;
-        attr.bp_type = event_type->bp_type;
-        attr.bp_len = event_type->bp_len;
+        attr.bp_type = event_type->config;
    } else {
        attr.config = event_type->config;
    }
+    attr.config1 = event_type->config1;
+    attr.config2 = event_type->config2;

    attr.sample_period = event_type->default_interval;
    attr.sample_type = PERF_SAMPLE_CALLCHAIN;
@@ -478,10 +749,14 @@ Error PerfEvents::check(Arguments& args) {
    } else if (args._ring == RING_KERNEL) {
        attr.exclude_user = 1;
    } else if (!Symbols::haveKernelSymbols()) {
-        Profiler::_instance.updateSymbols(true);
+        Profiler::instance()->updateSymbols(true);
        attr.exclude_kernel = Symbols::haveKernelSymbols() ? 0 : 1;
    }

+    if (_cstack == CSTACK_FP || _cstack == CSTACK_DWARF) {
+        attr.exclude_callchain_user = 1;
+    }
+
 #ifdef PERF_ATTR_SIZE_VER5
    if (args._cstack == CSTACK_LBR) {
        attr.sample_type |= PERF_SAMPLE_BRANCH_STACK | PERF_SAMPLE_REGS_USER;
@@ -501,9 +776,15 @@ Error PerfEvents::check(Arguments& args) {
 }

 Error PerfEvents::start(Arguments& args) {
-    _event_type = PerfEventType::forName(args._event_desc);
+    _event_type = PerfEventType::forName(args._event);
    if (_event_type == NULL) {
        return Error("Unsupported event type");
+    } else if (_event_type->counter_arg > 4) {
+        return Error("Only arguments 1-4 can be counted");
+    }
+
+    if (_pthread_entry == NULL && (_pthread_entry = lookupThreadEntry()) == NULL) {
+        return Error("Could not set pthread hook");
    }

    if (args._interval < 0) {
@@ -513,13 +794,13 @@ Error PerfEvents::start(Arguments& args) {

    _ring = args._ring;
    if (_ring != RING_USER && !Symbols::haveKernelSymbols()) {
-        fprintf(stderr, "WARNING: Kernel symbols are unavailable due to restrictions. Try\n"
-                        "  echo 0 > /proc/sys/kernel/kptr_restrict\n"
-                        "  echo 1 > /proc/sys/kernel/perf_event_paranoid\n");
+        Log::warn("Kernel symbols are unavailable due to restrictions. Try\n"
+                  "  sysctl kernel.kptr_restrict=0\n"
+                  "  sysctl kernel.perf_event_paranoid=1");
        _ring = RING_USER;
    }
    _cstack = args._cstack;
-    _print_extended_warning = _ring != RING_USER;
+    _use_mmap_page = _cstack != CSTACK_NO && (_ring != RING_USER || _cstack == CSTACK_DEFAULT || _cstack == CSTACK_LBR);

    int max_events = OS::getMaxThreadId();
    if (max_events != _max_events) {
@@ -528,34 +809,52 @@ Error PerfEvents::start(Arguments& args) {
        _max_events = max_events;
    }

-    OS::installSignalHandler(SIGPROF, signalHandler);
+    if (VM::isOpenJ9()) {
+        if (_cstack == CSTACK_DEFAULT) _cstack = CSTACK_DWARF;
+        OS::installSignalHandler(SIGPROF, signalHandlerJ9);
+        Error error = J9StackTraces::start(args);
+        if (error) {
+            return error;
+        }
+    } else {
+        OS::installSignalHandler(SIGPROF, signalHandler);
+    }

-    // Enable thread events before traversing currently running threads
-    Profiler::_instance.switchThreadEvents(JVMTI_ENABLE);
+    // Enable pthread hook before traversing currently running threads
+    __atomic_store_n(_pthread_entry, (void*)pthread_setspecific_hook, __ATOMIC_RELEASE);

    // Create perf_events for all existing threads
+    int err;
    bool created = false;
    ThreadList* thread_list = OS::listThreads();
    for (int tid; (tid = thread_list->next()) != -1; ) {
-        created |= createForThread(tid);
+        if ((err = createForThread(tid)) == 0) {
+            created = true;
+        }
    }
    delete thread_list;

    if (!created) {
-        Profiler::_instance.switchThreadEvents(JVMTI_DISABLE);
-        return Error("Perf events unavailable. See stderr of the target process.");
+        __atomic_store_n(_pthread_entry, (void*)pthread_setspecific, __ATOMIC_RELEASE);
+        J9StackTraces::stop();
+        if (err == EACCES || err == EPERM) {
+            return Error("No access to perf events. Try --fdtransfer or --all-user option or 'sysctl kernel.perf_event_paranoid=1'");
+        } else {
+            return Error("Perf events unavailable");
+        }
    }
    return Error::OK;
 }

 void PerfEvents::stop() {
+    __atomic_store_n(_pthread_entry, (void*)pthread_setspecific, __ATOMIC_RELEASE);
    for (int i = 0; i < _max_events; i++) {
        destroyForThread(i);
    }
+    J9StackTraces::stop();
 }

-int PerfEvents::getNativeTrace(void* ucontext, int tid, const void** callchain, int max_depth,
-                               CodeCache* java_methods, CodeCache* runtime_stubs) {
+int PerfEvents::walk(int tid, void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx) {
    PerfEvent* event = &_events[tid];
    if (!event->tryLock()) {
        return 0;  // the event is being destroyed
@@ -579,8 +878,9 @@ int PerfEvents::getNativeTrace(void* ucontext, int tid, const void** callchain,
                    u64 ip = ring.next();
                    if (ip < PERF_CONTEXT_MAX) {
                        const void* iptr = (const void*)ip;
-                        if (java_methods->contains(iptr) || runtime_stubs->contains(iptr) || depth >= max_depth) {
+                        if (CodeHeap::contains(iptr) || depth >= max_depth) {
                            // Stop at the first Java frame
+                            java_ctx->pc = iptr;
                            goto stack_complete;
                        }
                        callchain[depth++] = iptr;
@@ -592,7 +892,8 @@ int PerfEvents::getNativeTrace(void* ucontext, int tid, const void** callchain,

                    // Last userspace PC is stored right after branch stack
                    const void* pc = (const void*)ring.peek(bnr * 3 + 2);
-                    if (java_methods->contains(pc) || runtime_stubs->contains(pc) || depth >= max_depth) {
+                    if (CodeHeap::contains(pc) || depth >= max_depth) {
+                        java_ctx->pc = pc;
                        goto stack_complete;
                    }
                    callchain[depth++] = pc;
@@ -602,12 +903,14 @@ int PerfEvents::getNativeTrace(void* ucontext, int tid, const void** callchain,
                        const void* to = (const void*)ring.next();
                        ring.next();

-                        if (java_methods->contains(to) || runtime_stubs->contains(to) || depth >= max_depth) {
+                        if (CodeHeap::contains(to) || depth >= max_depth) {
+                            java_ctx->pc = to;
                            goto stack_complete;
                        }
                        callchain[depth++] = to;

-                        if (java_methods->contains(from) || runtime_stubs->contains(from) || depth >= max_depth) {
+                        if (CodeHeap::contains(from) || depth >= max_depth) {
+                            java_ctx->pc = from;
                            goto stack_complete;
                        }
                        callchain[depth++] = from;
@@ -624,9 +927,32 @@ stack_complete:
    }

    event->unlock();
+
+    if (_cstack == CSTACK_FP) {
+        depth += StackWalker::walkFP(ucontext, callchain + depth, max_depth - depth, java_ctx);
+    } else if (_cstack == CSTACK_DWARF) {
+        depth += StackWalker::walkDwarf(ucontext, callchain + depth, max_depth - depth, java_ctx);
+    }
+
    return depth;
 }

+void PerfEvents::resetBuffer(int tid) {
+    PerfEvent* event = &_events[tid];
+    if (!event->tryLock()) {
+        return;  // the event is being destroyed
+    }
+
+    struct perf_event_mmap_page* page = event->_page;
+    if (page != NULL) {
+        u64 head = page->data_head;
+        rmb();
+        page->data_tail = head;
+    }
+
+    event->unlock();
+}
+
 bool PerfEvents::supported() {
    // The official way of knowing if perf_event_open() support is enabled
    // is checking for the existence of the file /proc/sys/kernel/perf_event_paranoid
--- a/src/perfEvents_macos.cpp
+++ b/src/perfEvents_macos.cpp
@@ -24,14 +24,25 @@ PerfEvent* PerfEvents::_events;
 PerfEventType* PerfEvents::_event_type;
 long PerfEvents::_interval;
 Ring PerfEvents::_ring;
-bool PerfEvents::_print_extended_warning;
+CStack PerfEvents::_cstack;
+bool PerfEvents::_use_mmap_page;

+u64 PerfEvents::readCounter(siginfo_t* siginfo, void* ucontext) {
+    return 0;
+}

 void PerfEvents::signalHandler(int signo, siginfo_t* siginfo, void* ucontext) {
 }

+void PerfEvents::signalHandlerJ9(int signo, siginfo_t* siginfo, void* ucontext) {
+}
+
+const char* PerfEvents::title() {
+    return Engine::title();
+}
+
 const char* PerfEvents::units() {
-    return "ns";
+    return Engine::units();
 }

 Error PerfEvents::check(Arguments& args) {
@@ -45,11 +56,13 @@ Error PerfEvents::start(Arguments& args) {
 void PerfEvents::stop() {
 }

-int PerfEvents::getNativeTrace(void* ucontext, int tid, const void** callchain, int max_depth,
-                               CodeCache* java_methods, CodeCache* runtime_stubs) {
+int PerfEvents::walk(int tid, void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx) {
    return 0;
 }

+void PerfEvents::resetBuffer(int tid) {
+}
+
 bool PerfEvents::supported() {
    return false;
 }
@@ -58,8 +71,8 @@ const char* PerfEvents::getEventName(int event_id) {
    return NULL;
 }

-bool PerfEvents::createForThread(int tid) {
-    return false;
+int PerfEvents::createForThread(int tid) {
+    return -1;
 }

 void PerfEvents::destroyForThread(int tid) {
--- a/src/profiler.cpp
+++ b/src/profiler.cpp
--- a/src/profiler.h
+++ b/src/profiler.h
@@ -28,6 +28,7 @@
 #include "engine.h"
 #include "event.h"
 #include "flightRecorder.h"
+#include "log.h"
 #include "mutex.h"
 #include "spinLock.h"
 #include "threadFilter.h"
@@ -41,18 +42,9 @@ const char FULL_VERSION_STRING[] =

 const int MAX_NATIVE_FRAMES = 128;
 const int RESERVED_FRAMES   = 4;
-const int MAX_NATIVE_LIBS   = 2048;
 const int CONCURRENCY_LEVEL = 16;


-enum AddressType {
-    ADDR_UNKNOWN,
-    ADDR_JIT,
-    ADDR_STUB,
-    ADDR_NATIVE
-};
-
-
 union CallTraceBuffer {
    ASGCT_CallFrame _asgct_frames[1];
    jvmtiFrameInfo _jvmti_frames[1];
@@ -60,8 +52,11 @@ union CallTraceBuffer {


 class FrameName;
+class NMethod;
+class StackContext;

 enum State {
+    NEW,
    IDLE,
    RUNNING,
    TERMINATED
@@ -83,8 +78,12 @@ class Profiler {
    CallTraceStorage _call_trace_storage;
    FlightRecorder _jfr;
    Engine* _engine;
-    int _events;
+    Engine* _alloc_engine;
+    int _event_mask;
+
    time_t _start_time;
+    volatile bool _timer_is_running;
+    pthread_t _timer_thread;

    u64 _total_samples;
    u64 _failures[ASGCT_FAILURE_TYPES];
@@ -95,38 +94,25 @@ class Profiler {
    int _safe_mode;
    CStack _cstack;
    bool _add_thread_frame;
+    bool _add_sched_frame;
    bool _update_thread_names;
    volatile bool _thread_events_state;

-    SpinLock _jit_lock;
    SpinLock _stubs_lock;
-    CodeCache _java_methods;
-    NativeCodeCache _runtime_stubs;
-    NativeCodeCache* _native_libs[MAX_NATIVE_LIBS];
-    volatile int _native_lib_count;
+    CodeCache _runtime_stubs;
+    CodeCacheArray _native_libs;
+    const void* _call_stub_begin;
+    const void* _call_stub_end;

-    // Support for intercepting NativeLibrary.load() / NativeLibraries.load()
-    JNINativeMethod _load_method;
-    void* _original_NativeLibrary_load;
-    void* _trapped_NativeLibrary_load;
-    static jboolean JNICALL NativeLibraryLoadTrap(JNIEnv* env, jobject self, jstring name, jboolean builtin);
-    static jboolean JNICALL NativeLibrariesLoadTrap(JNIEnv* env, jobject self, jobject lib, jstring name, jboolean builtin, jboolean jni);
-    void bindNativeLibraryLoad(JNIEnv* env, bool enable);
-
-    // Support for intercepting Thread.setNativeName()
-    void* _original_Thread_setNativeName;
-    static void JNICALL ThreadSetNativeNameTrap(JNIEnv* env, jobject self, jstring name);
-    void bindThreadSetNativeName(JNIEnv* env, bool enable);
-
-    void switchNativeMethodTraps(bool enable);
+    // dlopen() hook support
+    void** _dlopen_entry;
+    static void* dlopen_hook(const char* filename, int flags);
+    void switchLibraryTrap(bool enable);

    Error installTraps(const char* begin, const char* end);
    void uninstallTraps();
-    static void trapHandler(int signo, siginfo_t* siginfo, void* ucontext);
-    void trapHandlerImpl(void* ucontext);

    void addJavaMethod(const void* address, int length, jmethodID method);
-    void removeJavaMethod(const void* address, jmethodID method);
    void addRuntimeStub(const void* address, int length, const char* name);

    void onThreadStart(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread);
@@ -134,12 +120,13 @@ class Profiler {

    const char* asgctError(int code);
    u32 getLockIndex(int tid);
-    int getNativeTrace(void* ucontext, ASGCT_CallFrame* frames, int tid);
-    int getJavaTraceAsync(void* ucontext, ASGCT_CallFrame* frames, int max_depth);
-    int getJavaTraceJvmti(jvmtiFrameInfo* jvmti_frames, ASGCT_CallFrame* frames, int max_depth);
-    int makeEventFrame(ASGCT_CallFrame* frames, jint event_type, uintptr_t id);
-    bool fillTopFrame(const void* pc, ASGCT_CallFrame* frame);
-    AddressType getAddressType(instruction_t* pc);
+    bool isAddressInCode(uintptr_t addr);
+    int getNativeTrace(void* ucontext, ASGCT_CallFrame* frames, int event_type, int tid, StackContext* java_ctx);
+    int getJavaTraceAsync(void* ucontext, ASGCT_CallFrame* frames, int max_depth, StackContext* java_ctx);
+    int getJavaTraceJvmti(jvmtiFrameInfo* jvmti_frames, ASGCT_CallFrame* frames, int start_depth, int max_depth);
+    int getJavaTraceInternal(jvmtiFrameInfo* jvmti_frames, ASGCT_CallFrame* frames, int max_depth);
+    int convertFrames(jvmtiFrameInfo* jvmti_frames, ASGCT_CallFrame* frames, int num_frames);
+    void fillFrameTypes(ASGCT_CallFrame* frames, int num_frames, NMethod* nmethod);
    void setThreadInfo(int tid, const char* name, jlong java_thread_id);
    void updateThreadName(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread);
    void updateJavaThreadNames();
@@ -147,83 +134,106 @@ class Profiler {
    bool excludeTrace(FrameName* fn, CallTrace* trace);
    void mangle(const char* name, char* buf, size_t size);
    Engine* selectEngine(const char* event_name);
+    Engine* selectAllocEngine(long alloc_interval);
+    Engine* activeEngine();
    Error checkJvmCapabilities();

-  public:
-    static Profiler _instance;
+    time_t addTimeout(time_t start, int timeout);
+    void startTimer(int timeout);
+    void stopTimer();
+    void timerLoop(int timeout);
+    static void* timerThreadEntry(void* arg);

+    void lockAll();
+    void unlockAll();
+
+    void dumpCollapsed(std::ostream& out, Arguments& args);
+    void dumpFlameGraph(std::ostream& out, Arguments& args, bool tree);
+    void dumpText(std::ostream& out, Arguments& args);
+
+    static Profiler* const _instance;
+
+  public:
    Profiler() :
-        _state(IDLE),
-        _begin_trap(),
-        _end_trap(),
+        _state(NEW),
+        _begin_trap(2),
+        _end_trap(3),
        _thread_filter(),
        _call_trace_storage(),
        _jfr(),
        _start_time(0),
+        _timer_is_running(false),
        _max_stack_depth(0),
        _safe_mode(0),
        _thread_events_state(JVMTI_DISABLE),
-        _jit_lock(),
        _stubs_lock(),
-        _java_methods(),
        _runtime_stubs("[stubs]"),
-        _native_lib_count(0),
-        _original_NativeLibrary_load(NULL) {
+        _native_libs(),
+        _call_stub_begin(NULL),
+        _call_stub_end(NULL),
+        _dlopen_entry(NULL) {

        for (int i = 0; i < CONCURRENCY_LEVEL; i++) {
            _calltrace_buffer[i] = NULL;
        }
    }

+    static Profiler* instance() {
+        return _instance;
+    }
+
    u64 total_samples() { return _total_samples; }
    time_t uptime()     { return time(NULL) - _start_time; }

    Dictionary* classMap() { return &_class_map; }
    ThreadFilter* threadFilter() { return &_thread_filter; }

-    void run(Arguments& args);
-    void runInternal(Arguments& args, std::ostream& out);
+    Error run(Arguments& args);
+    Error runInternal(Arguments& args, std::ostream& out);
+    Error restart(Arguments& args);
    void shutdown(Arguments& args);
    Error check(Arguments& args);
    Error start(Arguments& args, bool reset);
    Error stop();
+    Error flushJfr();
+    Error dump(std::ostream& out, Arguments& args);
    void switchThreadEvents(jvmtiEventMode mode);
-    void dump(std::ostream& out, Arguments& args);
-    void dumpCollapsed(std::ostream& out, Arguments& args);
-    void dumpFlameGraph(std::ostream& out, Arguments& args, bool tree);
-    void dumpFlat(std::ostream& out, Arguments& args);
-    ThreadState getThreadState(void* ucontext);
+    int convertNativeTrace(int native_frames, const void** callchain, ASGCT_CallFrame* frames);
    void recordSample(void* ucontext, u64 counter, jint event_type, Event* event);
+    void recordExternalSample(u64 counter, Event* event, int tid, int num_frames, ASGCT_CallFrame* frames);
+    void writeLog(LogLevel level, const char* message);
+    void writeLog(LogLevel level, const char* message, size_t len);

    void updateSymbols(bool kernel_symbols);
    const void* resolveSymbol(const char* name);
-    NativeCodeCache* findNativeLibrary(const void* address);
+    const char* getLibraryName(const char* native_symbol);
+    CodeCache* findJvmLibrary(const char* lib_name);
+    CodeCache* findNativeLibrary(const void* address);
    const char* findNativeMethod(const void* address);

+    void trapHandler(int signo, siginfo_t* siginfo, void* ucontext);
+    static void segvHandler(int signo, siginfo_t* siginfo, void* ucontext);
+    static void setupSignalHandlers();
+
    // CompiledMethodLoad is also needed to enable DebugNonSafepoints info by default
    static void JNICALL CompiledMethodLoad(jvmtiEnv* jvmti, jmethodID method,
                                           jint code_size, const void* code_addr,
                                           jint map_length, const jvmtiAddrLocationMap* map,
                                           const void* compile_info) {
-        _instance.addJavaMethod(code_addr, code_size, method);
-    }
-
-    static void JNICALL CompiledMethodUnload(jvmtiEnv* jvmti, jmethodID method,
-                                             const void* code_addr) {
-        _instance.removeJavaMethod(code_addr, method);
+        instance()->addJavaMethod(code_addr, code_size, method);
    }

    static void JNICALL DynamicCodeGenerated(jvmtiEnv* jvmti, const char* name,
                                             const void* address, jint length) {
-        _instance.addRuntimeStub(address, length, name);
+        instance()->addRuntimeStub(address, length, name);
    }

    static void JNICALL ThreadStart(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread) {
-        _instance.onThreadStart(jvmti, jni, thread);
+        instance()->onThreadStart(jvmti, jni, thread);
    }

    static void JNICALL ThreadEnd(jvmtiEnv* jvmti, JNIEnv* jni, jthread thread) {
-        _instance.onThreadEnd(jvmti, jni, thread);
+        instance()->onThreadEnd(jvmti, jni, thread);
    }

    friend class Recording;
--- a/src/safeAccess.h
+++ b/src/safeAccess.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _SAFEACCESS_H
+#define _SAFEACCESS_H
+
+#include <stdint.h>
+#include "arch.h"
+
+
+#ifdef __clang__
+#  define NOINLINE __attribute__((noinline))
+#else
+#  define NOINLINE __attribute__((noinline,noclone))
+#endif
+
+
+class SafeAccess {
+  public:
+    NOINLINE __attribute__((aligned(16)))
+    static void* load(void** ptr) {
+        return *ptr;
+    }
+
+    static uintptr_t skipFaultInstruction(uintptr_t pc) {
+        if (pc - (uintptr_t)load < 16) {
+#if defined(__x86_64__)
+            return *(u16*)pc == 0x8b48 ? 3 : 0;  // mov rax, [reg]
+#elif defined(__i386__)
+            return *(u8*)pc == 0x8b ? 2 : 0;     // mov eax, [reg]
+#elif defined(__arm__) || defined(__thumb__)
+            return (*(instruction_t*)pc & 0x0e50f000) == 0x04100000 ? 4 : 0;  // ldr r0, [reg]
+#elif defined(__aarch64__)
+            return (*(instruction_t*)pc & 0xffc0001f) == 0xf9400000 ? 4 : 0;  // ldr x0, [reg]
+#else
+            return sizeof(instruction_t);
+#endif
+        }
+        return 0;
+    }
+};
+
+#endif // _SAFEACCESS_H
--- a/src/spinLock.h
+++ b/src/spinLock.h
@@ -51,9 +51,19 @@ class SpinLock {
        __sync_fetch_and_sub(&_lock, 1);
    }

+    bool tryLockShared() {
+        int value;
+        while ((value = _lock) <= 0) {
+            if (__sync_bool_compare_and_swap(&_lock, value, value - 1)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
    void lockShared() {
        int value;
-        while ((value = _lock) == 1 || !__sync_bool_compare_and_swap(&_lock, value, value - 1)) {
+        while ((value = _lock) > 0 || !__sync_bool_compare_and_swap(&_lock, value, value - 1)) {
            spinPause();
        }
    }
--- a/src/stackFrame.h
+++ b/src/stackFrame.h
@@ -38,13 +38,11 @@ class StackFrame {
    }

    void restore(uintptr_t saved_pc, uintptr_t saved_sp, uintptr_t saved_fp) {
-        pc() = saved_pc;
-        sp() = saved_sp;
-        fp() = saved_fp;
-    }
-
-    bool validSP() {
-        return withinCurrentStack(sp());
+        if (_ucontext != NULL) {
+            pc() = saved_pc;
+            sp() = saved_sp;
+            fp() = saved_fp;
+        }
    }

    uintptr_t stackAt(int slot) {
@@ -55,7 +53,7 @@ class StackFrame {
    uintptr_t& sp();
    uintptr_t& fp();

-    uintptr_t retval();
+    uintptr_t& retval();
    uintptr_t arg0();
    uintptr_t arg1();
    uintptr_t arg2();
@@ -63,18 +61,11 @@ class StackFrame {

    void ret();

-    bool pop(bool trust_frame_pointer);
+    bool popStub(instruction_t* entry, const char* name);
+    bool popMethod(instruction_t* entry);

    bool checkInterruptedSyscall();

-    // Look that many stack slots for a return address candidate.
-    // 0 = do not use stack snooping heuristics.
-    static int callerLookupSlots();
-
-    // Check if PC looks like a valid return address (i.e. the previous instruction is a CALL).
-    // It's safe to return false to skip return address heuristics.
-    static bool isReturnAddress(instruction_t* pc);
-
    // Check if PC points to a syscall instruction
    static bool isSyscall(instruction_t* pc);
 };
--- a/src/stackFrame_aarch64.cpp
+++ b/src/stackFrame_aarch64.cpp
@@ -1,6 +1,5 @@
 /*
- * Copyright 2017 Andrei Pangin
- * Copyright 2017 BellSoft LLC
+ * Copyright 2021 Andrei Pangin
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -13,85 +12,123 @@
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
- *
- * Author: Dmitry Samersoff
 */

-#if defined(__aarch64__)
+#ifdef __aarch64__

 #include <errno.h>
+#include <string.h>
+#include <sys/syscall.h>
 #include "stackFrame.h"


-#define REG_FP 29
-#define REG_LR 30
+#ifdef __APPLE__
+#  define REG(l, m)  _ucontext->uc_mcontext->__ss.__##m
+#else
+#  define REG(l, m)  _ucontext->uc_mcontext.l
+#endif
+

 uintptr_t& StackFrame::pc() {
-    return (uintptr_t&)_ucontext->uc_mcontext.pc;
+    return (uintptr_t&)REG(pc, pc);
 }

 uintptr_t& StackFrame::sp() {
-    return (uintptr_t&)_ucontext->uc_mcontext.sp;
+    return (uintptr_t&)REG(sp, sp);
 }

 uintptr_t& StackFrame::fp() {
-    return (uintptr_t&)_ucontext->uc_mcontext.regs[REG_FP];
+    return (uintptr_t&)REG(regs[29], fp);
 }

-uintptr_t StackFrame::retval() {
-    return (uintptr_t)_ucontext->uc_mcontext.regs[0];
+uintptr_t& StackFrame::retval() {
+    return (uintptr_t&)REG(regs[0], x[0]);
 }

 uintptr_t StackFrame::arg0() {
-    return (uintptr_t)_ucontext->uc_mcontext.regs[0];
+    return (uintptr_t)REG(regs[0], x[0]);
 }

 uintptr_t StackFrame::arg1() {
-    return (uintptr_t)_ucontext->uc_mcontext.regs[1];
+    return (uintptr_t)REG(regs[1], x[1]);
 }

 uintptr_t StackFrame::arg2() {
-    return (uintptr_t)_ucontext->uc_mcontext.regs[2];
+    return (uintptr_t)REG(regs[2], x[2]);
 }

 uintptr_t StackFrame::arg3() {
-    return (uintptr_t)_ucontext->uc_mcontext.regs[3];
+    return (uintptr_t)REG(regs[3], x[3]);
 }

 void StackFrame::ret() {
-    _ucontext->uc_mcontext.pc = _ucontext->uc_mcontext.regs[REG_LR];
+    pc() = REG(regs[30], lr);
 }

-bool StackFrame::pop(bool trust_frame_pointer) {
-    if (fp() == sp()) {
-        // Expected frame layout:
-        // sp   000000nnnnnnnnnn  [stack]
-        // sp+8 000000nnnnnnnnnn  [link]
-        fp() = stackAt(0);
-        pc() = stackAt(1);
-        sp() += 16;
-    } else {
-        // Hope LR holds correct value
-        pc() = _ucontext->uc_mcontext.regs[REG_LR];
+
+bool StackFrame::popStub(instruction_t* entry, const char* name) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip == entry || *ip == 0xd65f03c0
+        || strncmp(name, "itable", 6) == 0
+        || strncmp(name, "vtable", 6) == 0
+        || strncmp(name, "compare_long_string_", 20) == 0
+        || strcmp(name, "zero_blocks") == 0
+        || strcmp(name, "forward_copy_longs") == 0
+        || strcmp(name, "backward_copy_longs") == 0
+        || strcmp(name, "InlineCacheBuffer") == 0)
+    {
+        ret();
+        return true;
+    } else if (entry != NULL && entry[0] == 0xa9bf7bfd) {
+        // The stub begins with
+        //   stp  x29, x30, [sp, #-16]!
+        //   mov  x29, sp
+        if (ip == entry + 1) {
+            sp() += 16;
+            ret();
+            return true;
+        } else if (entry[1] == 0x910003fd && withinCurrentStack(fp())) {
+            sp() = fp() + 16;
+            fp() = stackAt(-2);
+            pc() = stackAt(-1);
+            return true;
+        }
    }
+    return false;
+}
+
+bool StackFrame::popMethod(instruction_t* entry) {
+    instruction_t* ip = (instruction_t*)pc();
+    if ((*ip & 0xffe07fff) == 0xa9007bfd) {
+        // stp x29, x30, [sp, #offset]
+        // SP has been adjusted, but FP not yet stored in a new frame
+        unsigned int offset = (*ip >> 12) & 0x1f8;
+        sp() += offset + 16;
+    }
+    ret();
    return true;
 }

 bool StackFrame::checkInterruptedSyscall() {
+#ifdef __APPLE__
+    // We are not interested in syscalls that do not check error code, e.g. semaphore_wait_trap
+    if (*(instruction_t*)pc() == 0xd65f03c0) {
+        return true;
+    }
+    // If carry flag is set, the error code is in low byte of x0
+    if (REG(pstate, cpsr) & (1 << 29)) {
+        return (retval() & 0xff) == EINTR || (retval() & 0xff) == ETIMEDOUT;
+    } else {
+        return retval() == (uintptr_t)-EINTR; 
+    }
+#else
    return retval() == (uintptr_t)-EINTR;
-}
-
-int StackFrame::callerLookupSlots() {
-    return 0;
-}
-
-bool StackFrame::isReturnAddress(instruction_t* pc) {
-    return false;
+#endif
 }

 bool StackFrame::isSyscall(instruction_t* pc) {
-    // svc #0
-    return *pc == 0xd4000001;
+    // svc #0 or svc #80
+    return (*pc & 0xffffefff) == 0xd4000001;
 }

-#endif // defined(__aarch64__)
+#endif // __aarch64__
--- a/src/stackFrame_arm.cpp
+++ b/src/stackFrame_arm.cpp
@@ -17,6 +17,7 @@
 #if defined(__arm__) || defined(__thumb__)

 #include <errno.h>
+#include <string.h>
 #include "stackFrame.h"


@@ -32,8 +33,8 @@ uintptr_t& StackFrame::fp() {
    return (uintptr_t&)_ucontext->uc_mcontext.arm_fp;
 }

-uintptr_t StackFrame::retval() {
-    return (uintptr_t)_ucontext->uc_mcontext.arm_r0;
+uintptr_t& StackFrame::retval() {
+    return (uintptr_t&)_ucontext->uc_mcontext.arm_r0;
 }

 uintptr_t StackFrame::arg0() {
@@ -56,22 +57,45 @@ void StackFrame::ret() {
    _ucontext->uc_mcontext.arm_pc = _ucontext->uc_mcontext.arm_lr;
 }

-bool StackFrame::pop(bool trust_frame_pointer) {
+bool StackFrame::popStub(instruction_t* entry, const char* name) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip == entry || *ip == 0xe12fff1e
+        || strncmp(name, "itable", 6) == 0
+        || strncmp(name, "vtable", 6) == 0
+        || strcmp(name, "InlineCacheBuffer") == 0)
+    {
+        ret();
+        return true;
+    }
    return false;
 }

+bool StackFrame::popMethod(instruction_t* entry) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip > entry && ip <= entry + 4 && (*ip & 0xffffff00) == 0xe24dd000) {
+        //    push  {r11, lr}
+        //    mov   r11, sp (optional)
+        // -> sub   sp, sp, #offs
+        fp() = stackAt(0);
+        pc() = stackAt(1);
+        sp() += 8;
+        return true;
+    } else if (*ip == 0xe8bd4800) {
+        //    add   sp, sp, #offs
+        // -> pop   {r11, lr}
+        fp() = stackAt(0);
+        pc() = stackAt(1);
+        sp() += 8;
+        return true;
+    }
+    ret();
+    return true;
+}
+
 bool StackFrame::checkInterruptedSyscall() {
    return retval() == (uintptr_t)-EINTR;
 }

-int StackFrame::callerLookupSlots() {
-    return 0;
-}
-
-bool StackFrame::isReturnAddress(instruction_t* pc) {
-    return false;
-}
-
 bool StackFrame::isSyscall(instruction_t* pc) {
    // swi #0
    return *pc == 0xef000000;
--- a/src/stackFrame_i386.cpp
+++ b/src/stackFrame_i386.cpp
@@ -17,6 +17,7 @@
 #ifdef __i386__

 #include <errno.h>
+#include <string.h>
 #include "stackFrame.h"


@@ -32,8 +33,8 @@ uintptr_t& StackFrame::fp() {
    return (uintptr_t&)_ucontext->uc_mcontext.gregs[REG_EBP];
 }

-uintptr_t StackFrame::retval() {
-    return (uintptr_t)_ucontext->uc_mcontext.gregs[REG_EAX];
+uintptr_t& StackFrame::retval() {
+    return (uintptr_t&)_ucontext->uc_mcontext.gregs[REG_EAX];
 }

 uintptr_t StackFrame::arg0() {
@@ -57,13 +58,44 @@ void StackFrame::ret() {
    sp() += 4;
 }

-bool StackFrame::pop(bool trust_frame_pointer) {
-    if (trust_frame_pointer && withinCurrentStack(fp())) {
-        sp() = fp() + 8;
-        fp() = stackAt(-2);
-        pc() = stackAt(-1);
+bool StackFrame::popStub(instruction_t* entry, const char* name) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip == entry || *ip == 0xc3
+        || strncmp(name, "itable", 6) == 0
+        || strncmp(name, "vtable", 6) == 0
+        || strcmp(name, "InlineCacheBuffer") == 0)
+    {
+        pc() = stackAt(0);
+        sp() += 4;
        return true;
-    } else if (fp() == sp() || withinCurrentStack(stackAt(0))) {
+    } else if (entry != NULL && entry[0] == 0x55 && entry[1] == 0x8b && entry[2] == 0xec) {
+        // The stub begins with
+        //   push ebp
+        //   mov  ebp, esp
+        if (ip == entry + 1) {
+            pc() = stackAt(1);
+            sp() += 8;
+            return true;
+        } else if (withinCurrentStack(fp())) {
+            sp() = fp() + 8;
+            fp() = stackAt(-2);
+            pc() = stackAt(-1);
+            return true;
+        }
+    }
+    return false;
+}
+
+bool StackFrame::popMethod(instruction_t* entry) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip <= entry || *ip == 0xc3 || *ip == 0x55        // ret or push ebp
+        || (((uintptr_t)ip & 0xfff) && ip[-1] == 0x5d))  // after pop ebp
+    {
+        pc() = stackAt(0);
+        sp() += 4;
+        return true;
+    } else if (*ip == 0x5d) {
+        // pop ebp
        fp() = stackAt(0);
        pc() = stackAt(1);
        sp() += 8;
@@ -76,21 +108,6 @@ bool StackFrame::checkInterruptedSyscall() {
    return retval() == (uintptr_t)-EINTR;
 }

-int StackFrame::callerLookupSlots() {
-    return 7;
-}
-
-bool StackFrame::isReturnAddress(instruction_t* pc) {
-    if (pc[-5] == 0xe8) {
-        // call rel32
-        return true;
-    } else if (pc[-2] == 0xff && ((pc[-1] & 0xf0) == 0xd0 || (pc[-1] & 0xf0) == 0x10)) {
-        // call reg or call [reg]
-        return true;
-    }
-    return false;
-}
-
 bool StackFrame::isSyscall(instruction_t* pc) {
    // int 0x80
    return pc[0] == 0xcd && pc[1] == 0x80;
--- a/src/stackFrame_ppc64.cpp
+++ b/src/stackFrame_ppc64.cpp
@@ -0,0 +1,133 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Authors: Andrei Pangin and Gunter Haug
+ */
+
+#if defined(__PPC64__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+
+#include <errno.h>
+#include <signal.h>
+#include "stackFrame.h"
+
+
+uintptr_t& StackFrame::pc() {
+    return (uintptr_t&)_ucontext->uc_mcontext.regs->nip;
+}
+
+uintptr_t& StackFrame::sp() {
+    return (uintptr_t&)_ucontext->uc_mcontext.regs->gpr[1];
+}
+
+uintptr_t& StackFrame::fp() {
+    return *((uintptr_t*)_ucontext->uc_mcontext.regs->gpr[1]);
+}
+
+uintptr_t& StackFrame::retval() {
+    return (uintptr_t&)_ucontext->uc_mcontext.regs->gpr[3];
+}
+
+uintptr_t StackFrame::arg0() {
+    return (uintptr_t)_ucontext->uc_mcontext.regs->gpr[3];
+}
+
+uintptr_t StackFrame::arg1() {
+    return (uintptr_t)_ucontext->uc_mcontext.regs->gpr[4];
+}
+
+uintptr_t StackFrame::arg2() {
+    return (uintptr_t)_ucontext->uc_mcontext.regs->gpr[5];
+}
+
+uintptr_t StackFrame::arg3() {
+    return (uintptr_t)_ucontext->uc_mcontext.regs->gpr[6];
+}
+
+void StackFrame::ret() {
+    _ucontext->uc_mcontext.regs->nip = _ucontext->uc_mcontext.regs->link;
+}
+
+static inline bool inC1EpilogueCrit(uintptr_t pc) {
+    if (!(pc & 0xfff)) {
+        // Make sure we are not at the page boundary, so that reading [pc - 1] is safe
+        return false;
+    }
+    // C1 epilogue and critical section (posX)
+    //        3821**** add     r1,r1,xx
+    // pos3   xxxxxxxx
+    // pos2   1000e1eb ld      r31,16(r1)
+    // pos1   a603e87f mtlr    r31
+    //        xxxxxxxx
+    //        2000804e blr
+    instruction_t* inst = (instruction_t*)pc;
+    if (inst[ 1] == 0xebe10010 && inst[2] == 0x7fe803a6 ||
+        inst[ 0] == 0xebe10010 && inst[1] == 0x7fe803a6 ||
+        inst[-1] == 0xebe10010 && inst[0] == 0x7fe803a6) {
+        return true;
+    }
+
+    return false; // not in critical section
+}
+
+static inline bool inC2PrologueCrit(uintptr_t pc) {
+    // C2 prologue and critical section
+    //        f821**** stdu    r1, (xx)r1
+    // pos1   fa950010 std     r20,16(r21)
+    instruction_t* inst = (instruction_t*)pc;
+    if (inst[0] == 0xfa950010 && (inst[-1] & 0xffff0000) == 0xf8210000) {
+        return true;
+    }
+
+    return false; // not in critical section
+}
+
+
+bool StackFrame::popStub(instruction_t* entry, const char* name) {
+    pc() = _ucontext->uc_mcontext.regs->link;
+    return true;
+}
+
+bool StackFrame::popMethod(instruction_t* entry) {
+    // On PPC there is a valid back link to the previous frame at all times. The callee stores
+    // the return address in the caller's frame before it constructs its own frame. After it
+    // has destroyed its frame it restores the link register and returns. A problematic sequence
+    // is the prologue/epilogue of a compiled method before/after frame construction/destruction.
+    // Therefore popping the frame would not help here, as it is not yet/anymore present, rather
+    // more adjusting the pc to the callers pc does the trick. There are two exceptions to this,
+    // One in the prologue of C2 compiled methods and one in the epilogue of C1 compiled methods.
+    if (inC1EpilogueCrit(pc())) {
+        // lr not yet set: use the value stored in the frame
+        pc() = stackAt(2);
+    } else if (inC2PrologueCrit(pc())) {
+        // frame constructed but lr not yet stored in it: just do it here
+        *(((unsigned long *) _ucontext->uc_mcontext.regs->gpr[21]) + 2) = (unsigned long) _ucontext->uc_mcontext.regs->gpr[20];
+    } else {
+        // most probably caller's framer is still on top but pc is already in callee: use caller's pc
+        pc() = _ucontext->uc_mcontext.regs->link;
+    }
+
+    return true;
+}
+
+bool StackFrame::checkInterruptedSyscall() {
+    return retval() == (uintptr_t)-EINTR;
+}
+
+bool StackFrame::isSyscall(instruction_t* pc) {
+    // sc/svc
+    return (*pc & 0x1f) == 17;
+}
+
+#endif // defined(__PPC64__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
--- a/src/stackFrame_x64.cpp
+++ b/src/stackFrame_x64.cpp
@@ -17,47 +17,48 @@
 #ifdef __x86_64__

 #include <errno.h>
+#include <string.h>
 #include <sys/syscall.h>
 #include "stackFrame.h"


 #ifdef __APPLE__
-#  define REG(l, m)  _ucontext->uc_mcontext->__ss.m
+#  define REG(l, m)  _ucontext->uc_mcontext->__ss.__##m
 #else
-#  define REG(l, m)  _ucontext->uc_mcontext.gregs[l]
+#  define REG(l, m)  _ucontext->uc_mcontext.gregs[REG_##l]
 #endif


 uintptr_t& StackFrame::pc() {
-    return (uintptr_t&)REG(REG_RIP, __rip);
+    return (uintptr_t&)REG(RIP, rip);
 }

 uintptr_t& StackFrame::sp() {
-    return (uintptr_t&)REG(REG_RSP, __rsp);
+    return (uintptr_t&)REG(RSP, rsp);
 }

 uintptr_t& StackFrame::fp() {
-    return (uintptr_t&)REG(REG_RBP, __rbp);
+    return (uintptr_t&)REG(RBP, rbp);
 }

-uintptr_t StackFrame::retval() {
-    return (uintptr_t)REG(REG_RAX, __rax);
+uintptr_t& StackFrame::retval() {
+    return (uintptr_t&)REG(RAX, rax);
 }

 uintptr_t StackFrame::arg0() {
-    return (uintptr_t)REG(REG_RDI, __rdi);
+    return (uintptr_t)REG(RDI, rdi);
 }

 uintptr_t StackFrame::arg1() {
-    return (uintptr_t)REG(REG_RSI, __rsi);
+    return (uintptr_t)REG(RSI, rsi);
 }

 uintptr_t StackFrame::arg2() {
-    return (uintptr_t)REG(REG_RDX, __rdx);
+    return (uintptr_t)REG(RDX, rdx);
 }

 uintptr_t StackFrame::arg3() {
-    return (uintptr_t)REG(REG_RCX, __rcx);
+    return (uintptr_t)REG(RCX, rcx);
 }

 void StackFrame::ret() {
@@ -66,41 +67,59 @@ void StackFrame::ret() {
 }


-static inline bool isFramePrologueEpilogue(uintptr_t pc) {
-    if (pc & 0xfff) {
-        // Make sure we are not at the page boundary, so that reading [pc - 1] is safe
-        unsigned int opcode = *(unsigned int*)(pc - 1);
-        if (opcode == 0xec834855) {
-            // push rbp
-            // sub  rsp, $const
+bool StackFrame::popStub(instruction_t* entry, const char* name) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip == entry || *ip == 0xc3
+        || strncmp(name, "itable", 6) == 0
+        || strncmp(name, "vtable", 6) == 0
+        || strcmp(name, "InlineCacheBuffer") == 0)
+    {
+        pc() = stackAt(0);
+        sp() += 8;
+        return true;
+    } else if (entry != NULL && *(unsigned int*)entry == 0xec8b4855) {
+        // The stub begins with
+        //   push rbp
+        //   mov  rbp, rsp
+        if (ip == entry + 1) {
+            pc() = stackAt(1);
+            sp() += 16;
            return true;
-        } else if (opcode == 0xec8b4855) {
-            // push rbp
-            // mov  rbp, rsp
+        } else if (withinCurrentStack(fp())) {
+            sp() = fp() + 16;
+            fp() = stackAt(-2);
+            pc() = stackAt(-1);
            return true;
        }
    }
-
-    if (*(unsigned char*)pc == 0x5d && *(unsigned short*)(pc + 1) == 0x0585) {
-        // pop  rbp
-        // test [polling_page], eax
-        return true;
-    }
-
    return false;
 }

-bool StackFrame::pop(bool trust_frame_pointer) {
-    if (trust_frame_pointer && withinCurrentStack(fp())) {
-        sp() = fp() + 16;
-        fp() = stackAt(-2);
-        pc() = stackAt(-1);
+bool StackFrame::popMethod(instruction_t* entry) {
+    instruction_t* ip = (instruction_t*)pc();
+    if (ip <= entry || *ip == 0xc3 || *ip == 0x55                               // ret or push rbp
+        || (((uintptr_t)ip & 0xfff) && ip[-1] == 0x5d)                          // after pop rbp
+        || (ip[0] == 0x41 && ip[1] == 0x85 && ip[2] == 0x02 && ip[3] == 0xc3))  // poll return
+    {
+        pc() = stackAt(0);
+        sp() += 8;
        return true;
-    } else if (fp() == sp() || withinCurrentStack(stackAt(0)) || isFramePrologueEpilogue(pc())) {
+    } else if (*ip == 0x5d) {
+        // pop rbp
        fp() = stackAt(0);
        pc() = stackAt(1);
        sp() += 16;
        return true;
+    } else if (ip <= entry + 15 && ((uintptr_t)ip & 0xfff) && ip[-1] == 0x55) {
+        // push rbp
+        pc() = stackAt(1);
+        sp() += 16;
+        return true;
+    } else if (ip <= entry + 7 && ip[0] == 0x48 && ip[1] == 0x89 && ip[2] == 0x6c && ip[3] == 0x24) {
+        // mov [rsp + #off], rbp
+        sp() += ip[4] + 16;
+        pc() = stackAt(-1);
+        return true;
    }
    return false;
 }
@@ -113,7 +132,7 @@ bool StackFrame::checkInterruptedSyscall() {
    }
    // If CF is set, the error code is in low byte of eax,
    // some other syscalls (ulock_wait) do not set CF when interrupted
-    if (REG(REG_EFL, __rflags) & 1) {
+    if (REG(EFL, rflags) & 1) {
        return (retval() & 0xff) == EINTR || (retval() & 0xff) == ETIMEDOUT;
    } else {
        return retval() == (uintptr_t)-EINTR; 
@@ -122,7 +141,7 @@ bool StackFrame::checkInterruptedSyscall() {
    if (retval() == (uintptr_t)-EINTR) {
        // Workaround for JDK-8237858: restart the interrupted poll() manually.
        // Check if the previous instruction is mov eax, SYS_poll with infinite timeout
-        if (arg2() == (uintptr_t)-1) {
+        if ((int)arg2() == -1) {
            uintptr_t pc = this->pc();
            if ((pc & 0xfff) >= 7 && *(unsigned char*)(pc - 7) == 0xb8 && *(int*)(pc - 6) == SYS_poll) {
                this->pc() = pc - 7;
@@ -134,21 +153,6 @@ bool StackFrame::checkInterruptedSyscall() {
 #endif
 }

-int StackFrame::callerLookupSlots() {
-    return 7;
-}
-
-bool StackFrame::isReturnAddress(instruction_t* pc) {
-    if (pc[-5] == 0xe8) {
-        // call rel32
-        return true;
-    } else if (pc[-2] == 0xff && ((pc[-1] & 0xf0) == 0xd0 || (pc[-1] & 0xf0) == 0x10)) {
-        // call reg or call [reg]
-        return true;
-    }
-    return false;
-}
-
 bool StackFrame::isSyscall(instruction_t* pc) {
    return pc[0] == 0x0f && pc[1] == 0x05;
 }
--- a/src/stackWalker.cpp
+++ b/src/stackWalker.cpp
@@ -0,0 +1,154 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "stackWalker.h"
+#include "dwarf.h"
+#include "profiler.h"
+#include "safeAccess.h"
+#include "stackFrame.h"
+#include "vmStructs.h"
+
+
+const intptr_t MIN_VALID_PC = 0x1000;
+const intptr_t MAX_WALK_SIZE = 0x100000;
+const intptr_t MAX_FRAME_SIZE = 0x40000;
+
+
+int StackWalker::walkFP(void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx) {
+    const void* pc;
+    uintptr_t fp;
+    uintptr_t sp;
+    uintptr_t bottom = (uintptr_t)&sp + MAX_WALK_SIZE;
+
+    if (ucontext == NULL) {
+        pc = __builtin_return_address(0);
+        fp = (uintptr_t)__builtin_frame_address(1);
+        sp = (uintptr_t)__builtin_frame_address(0);
+    } else {
+        StackFrame frame(ucontext);
+        pc = (const void*)frame.pc();
+        fp = frame.fp();
+        sp = frame.sp();
+    }
+
+    int depth = 0;
+
+    // Walk until the bottom of the stack or until the first Java frame
+    while (depth < max_depth) {
+         if (CodeHeap::contains(pc)) {
+            java_ctx->set(pc, sp, fp);
+            break;
+         }
+
+        callchain[depth++] = pc;
+
+        // Check if the next frame is below on the current stack
+        if (fp < sp || fp >= sp + MAX_FRAME_SIZE || fp >= bottom) {
+            break;
+        }
+
+        // Frame pointer must be word aligned
+        if ((fp & (sizeof(uintptr_t) - 1)) != 0) {
+            break;
+        }
+
+        pc = stripPointer(SafeAccess::load((void**)fp + FRAME_PC_SLOT));
+        if (pc < (const void*)MIN_VALID_PC || pc > (const void*)-MIN_VALID_PC) {
+            break;
+        }
+
+        sp = fp + (FRAME_PC_SLOT + 1) * sizeof(void*);
+        fp = *(uintptr_t*)fp;
+    }
+
+    return depth;
+}
+
+int StackWalker::walkDwarf(void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx) {
+    const void* pc;
+    uintptr_t fp;
+    uintptr_t sp;
+    uintptr_t prev_sp;
+    uintptr_t bottom = (uintptr_t)&sp + MAX_WALK_SIZE;
+
+    if (ucontext == NULL) {
+        pc = __builtin_return_address(0);
+        fp = (uintptr_t)__builtin_frame_address(1);
+        sp = (uintptr_t)__builtin_frame_address(0);
+    } else {
+        StackFrame frame(ucontext);
+        pc = (const void*)frame.pc();
+        fp = frame.fp();
+        sp = frame.sp();
+    }
+
+    int depth = 0;
+    Profiler* profiler = Profiler::instance();
+
+    // Walk until the bottom of the stack or until the first Java frame
+    while (depth < max_depth) {
+         if (CodeHeap::contains(pc)) {
+            java_ctx->set(pc, sp, fp);
+            break;
+         }
+
+        callchain[depth++] = pc;
+        prev_sp = sp;
+
+        FrameDesc* f;
+        CodeCache* cc = profiler->findNativeLibrary(pc);
+        if (cc == NULL || (f = cc->findFrameDesc(pc)) == NULL) {
+            f = &FrameDesc::default_frame;
+        }
+
+        u8 cfa_reg = (u8)f->cfa;
+        int cfa_off = f->cfa >> 8;
+        if (cfa_reg == DW_REG_SP) {
+            sp = sp + cfa_off;
+        } else if (cfa_reg == DW_REG_FP) {
+            sp = fp + cfa_off;
+        } else if (cfa_reg == DW_REG_PLT) {
+            sp += ((uintptr_t)pc & 15) >= 11 ? cfa_off * 2 : cfa_off;
+        } else {
+            break;
+        }
+
+        // Check if the next frame is below on the current stack
+        if (sp < prev_sp || sp >= prev_sp + MAX_FRAME_SIZE || sp >= bottom) {
+            break;
+        }
+
+        // Stack pointer must be word aligned
+        if ((sp & (sizeof(uintptr_t) - 1)) != 0) {
+            break;
+        }
+
+        if (f->fp_off & DW_PC_OFFSET) {
+            pc = (const char*)pc + (f->fp_off >> 1);
+        } else {
+            if (f->fp_off != DW_SAME_FP && f->fp_off < MAX_FRAME_SIZE && f->fp_off > -MAX_FRAME_SIZE) {
+                fp = (uintptr_t)SafeAccess::load((void**)(sp + f->fp_off));
+            }
+            pc = stripPointer(SafeAccess::load((void**)sp - 1));
+        }
+
+        if (pc < (const void*)MIN_VALID_PC || pc > (const void*)-MIN_VALID_PC) {
+            break;
+        }
+    }
+
+    return depth;
+}
--- a/src/stackWalker.h
+++ b/src/stackWalker.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2021 Andrei Pangin
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef _STACKWALKER_H
+#define _STACKWALKER_H
+
+#include <stdint.h>
+
+
+struct StackContext {
+    const void* pc;
+    uintptr_t sp;
+    uintptr_t fp;
+
+    void set(const void* pc, uintptr_t sp, uintptr_t fp) {
+        this->pc = pc;
+        this->sp = sp;
+        this->fp = fp;
+    }
+};
+
+class StackWalker {
+  public:
+    static int walkFP(void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx);
+    static int walkDwarf(void* ucontext, const void** callchain, int max_depth, StackContext* java_ctx);
+};
+
+#endif // _STACKWALKER_H
--- a/src/symbols.h
+++ b/src/symbols.h
@@ -29,8 +29,10 @@ class Symbols {
    static bool _have_kernel_symbols;

  public:
-    static void parseKernelSymbols(NativeCodeCache* cc);
-    static void parseLibraries(NativeCodeCache** array, volatile int& count, int size, bool kernel_symbols);
+    static void parseKernelSymbols(CodeCache* cc);
+    static void parseLibraries(CodeCacheArray* array, bool kernel_symbols);
+
+    static void makePatchable(CodeCache* cc);

    static bool haveKernelSymbols() {
        return _have_kernel_symbols;
--- a/src/symbols_linux.cpp
+++ b/src/symbols_linux.cpp
@@ -27,11 +27,11 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <linux/limits.h>
-#include <fstream>
-#include <iostream>
-#include <string>
 #include "symbols.h"
-#include "arch.h"
+#include "dwarf.h"
+#include "fdtransferClient.h"
+#include "log.h"
+#include "os.h"


 class SymbolDesc {
@@ -76,7 +76,8 @@ class MemoryMapDesc {
      }

      const char* file()    { return _file; }
-      bool isExecutable()   { return _perm[0] == 'r' && _perm[2] == 'x'; }
+      bool isReadable()     { return _perm[0] == 'r'; }
+      bool isExecutable()   { return _perm[2] == 'x'; }
      const char* addr()    { return (const char*)strtoul(_addr, NULL, 16); }
      const char* end()     { return (const char*)strtoul(_end, NULL, 16); }
      unsigned long offs()  { return strtoul(_offs, NULL, 16); }
@@ -88,30 +89,40 @@ class MemoryMapDesc {
 const unsigned char ELFCLASS_SUPPORTED = ELFCLASS64;
 typedef Elf64_Ehdr ElfHeader;
 typedef Elf64_Shdr ElfSection;
+typedef Elf64_Phdr ElfProgramHeader;
 typedef Elf64_Nhdr ElfNote;
 typedef Elf64_Sym  ElfSymbol;
 typedef Elf64_Rel  ElfRelocation;
+typedef Elf64_Dyn  ElfDyn;
 #define ELF_R_SYM  ELF64_R_SYM
 #else
 const unsigned char ELFCLASS_SUPPORTED = ELFCLASS32;
 typedef Elf32_Ehdr ElfHeader;
 typedef Elf32_Shdr ElfSection;
+typedef Elf32_Phdr ElfProgramHeader;
 typedef Elf32_Nhdr ElfNote;
 typedef Elf32_Sym  ElfSymbol;
 typedef Elf32_Rel  ElfRelocation;
+typedef Elf32_Dyn  ElfDyn;
 #define ELF_R_SYM  ELF32_R_SYM
 #endif // __LP64__

+#ifdef __musl__
+#  define DYN_BASE _base
+#else
+#  define DYN_BASE 0
+#endif // __musl__
+

 class ElfParser {
  private:
-    NativeCodeCache* _cc;
+    CodeCache* _cc;
    const char* _base;
    const char* _file_name;
    ElfHeader* _header;
    const char* _sections;

-    ElfParser(NativeCodeCache* cc, const char* base, const void* addr, const char* file_name = NULL) {
+    ElfParser(CodeCache* cc, const char* base, const void* addr, const char* file_name = NULL) {
        _cc = cc;
        _base = base;
        _file_name = file_name;
@@ -119,7 +130,7 @@ class ElfParser {
        _sections = (const char*)addr + _header->e_shoff;
    }

-    bool valid_header() {
+    bool validHeader() {
        unsigned char* ident = _header->e_ident;
        return ident[0] == 0x7f && ident[1] == 'E' && ident[2] == 'L' && ident[3] == 'F'
            && ident[4] == ELFCLASS_SUPPORTED && ident[5] == ELFDATA2LSB && ident[6] == EV_CURRENT
@@ -134,8 +145,15 @@ class ElfParser {
        return (const char*)_header + section->sh_offset;
    }

-    ElfSection* findSection(uint32_t type, const char* name);
+    const char* at(ElfProgramHeader* pheader) {
+        return _header->e_type == ET_EXEC ? (const char*)pheader->p_vaddr : (const char*)_header + pheader->p_vaddr;
+    }

+    ElfSection* findSection(uint32_t type, const char* name);
+    ElfProgramHeader* findProgramHeader(uint32_t type);
+
+    void parseDynamicSection();
+    void parseDwarfInfo();
    void loadSymbols(bool use_debug);
    bool loadSymbolsUsingBuildId();
    bool loadSymbolsUsingDebugLink();
@@ -143,8 +161,9 @@ class ElfParser {
    void addRelocationSymbols(ElfSection* reltab, const char* plt);

  public:
-    static bool parseFile(NativeCodeCache* cc, const char* base, const char* file_name, bool use_debug);
-    static void parseMem(NativeCodeCache* cc, const char* base);
+    static void parseProgramHeaders(CodeCache* cc, const char* base);
+    static bool parseFile(CodeCache* cc, const char* base, const char* file_name, bool use_debug);
+    static void parseMem(CodeCache* cc, const char* base);
 };


@@ -163,7 +182,20 @@ ElfSection* ElfParser::findSection(uint32_t type, const char* name) {
    return NULL;
 }

-bool ElfParser::parseFile(NativeCodeCache* cc, const char* base, const char* file_name, bool use_debug) {
+ElfProgramHeader* ElfParser::findProgramHeader(uint32_t type) {
+    const char* pheaders = (const char*)_header + _header->e_phoff;
+
+    for (int i = 0; i < _header->e_phnum; i++) {
+        ElfProgramHeader* pheader = (ElfProgramHeader*)(pheaders + i * _header->e_phentsize);
+        if (pheader->p_type == type) {
+            return pheader;
+        }
+    }
+
+    return NULL;
+}
+
+bool ElfParser::parseFile(CodeCache* cc, const char* base, const char* file_name, bool use_debug) {
    int fd = open(file_name, O_RDONLY);
    if (fd == -1) {
        return false;
@@ -174,30 +206,91 @@ bool ElfParser::parseFile(NativeCodeCache* cc, const char* base, const char* fil
    close(fd);

    if (addr == MAP_FAILED) {
-        if (strcmp(file_name, "/") == 0) {
-            // https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1843018
-            fprintf(stderr, "Could not parse symbols due to the OS bug\n");
-        } else {
-            fprintf(stderr, "Could not parse symbols from %s: %s\n", file_name, strerror(errno));
-        }
+        Log::warn("Could not parse symbols from %s: %s", file_name, strerror(errno));
    } else {
        ElfParser elf(cc, base, addr, file_name);
-        elf.loadSymbols(use_debug);
+        if (elf.validHeader()) {
+            elf.loadSymbols(use_debug);
+        }
        munmap(addr, length);
    }
    return true;
 }

-void ElfParser::parseMem(NativeCodeCache* cc, const char* base) {
+void ElfParser::parseMem(CodeCache* cc, const char* base) {
    ElfParser elf(cc, base, base);
-    elf.loadSymbols(false);
+    if (elf.validHeader()) {
+        elf.loadSymbols(false);
+    }
+}
+
+void ElfParser::parseProgramHeaders(CodeCache* cc, const char* base) {
+    ElfParser elf(cc, base, base);
+    if (elf.validHeader()) {
+        cc->setTextBase(base);
+        elf.parseDynamicSection();
+        elf.parseDwarfInfo();
+    }
+}
+
+void ElfParser::parseDynamicSection() {
+   ElfProgramHeader* dynamic = findProgramHeader(PT_DYNAMIC);
+    if (dynamic != NULL) {
+        void** got_start = NULL;
+        size_t pltrelsz = 0;
+        size_t relsz = 0;
+        size_t relent = 0;
+        size_t relcount = 0;
+
+        const char* dyn_start = at(dynamic);
+        const char* dyn_end = dyn_start + dynamic->p_memsz;
+        for (ElfDyn* dyn = (ElfDyn*)dyn_start; dyn < (ElfDyn*)dyn_end; dyn++) {
+            switch (dyn->d_tag) {
+                case DT_PLTGOT:
+                    got_start = (void**)(DYN_BASE + dyn->d_un.d_ptr) + 3;
+                    break;
+                case DT_PLTRELSZ:
+                    pltrelsz = dyn->d_un.d_val;
+                    break;
+                case DT_RELASZ:
+                case DT_RELSZ:
+                    relsz = dyn->d_un.d_val;
+                    break;
+                case DT_RELAENT:
+                case DT_RELENT:
+                    relent = dyn->d_un.d_val;
+                    break;
+                case DT_RELACOUNT:
+                case DT_RELCOUNT:
+                    relcount = dyn->d_un.d_val;
+                    break;
+            }
+        }
+
+        if (got_start != NULL && relent != 0) {
+            if (pltrelsz != 0) {
+                // The number of entries in .got.plt section matches the number of entries in .rela.plt
+                _cc->setGlobalOffsetTable(got_start, pltrelsz / relent);
+            } else if (relsz != 0) {
+                // RELRO technique: .got.plt has been merged into .got and made read-only.
+                // Count the number of entries in .rela.dyn, excluding R_X86_64_RELATIVE.
+                _cc->setGlobalOffsetTable(got_start, relsz / relent - relcount);
+            }
+        }
+    }
+}
+
+void ElfParser::parseDwarfInfo() {
+    if (!DWARF_SUPPORTED) return;
+
+    ElfProgramHeader* eh_frame_hdr = findProgramHeader(PT_GNU_EH_FRAME);
+    if (eh_frame_hdr != NULL) {
+        DwarfParser dwarf(_cc->name(), _base, at(eh_frame_hdr));
+        _cc->setDwarfTable(dwarf.table(), dwarf.count());
+    }
 }

 void ElfParser::loadSymbols(bool use_debug) {
-    if (!valid_header()) {
-        return;
-    }
-
    // Look for debug symbols in the original .so
    ElfSection* section = findSection(SHT_SYMTAB, ".symtab");
    if (section != NULL) {
@@ -219,8 +312,8 @@ void ElfParser::loadSymbols(bool use_debug) {
    }

 loaded:
-    // Synthesize names for PLT stubs
    if (use_debug) {
+        // Synthesize names for PLT stubs
        ElfSection* plt = findSection(SHT_PROGBITS, ".plt");
        ElfSection* reltab = findSection(SHT_RELA, ".rela.plt");
        if (reltab == NULL) {
@@ -307,7 +400,10 @@ void ElfParser::loadSymbolTable(ElfSection* symtab) {
    for (; symbols < symbols_end; symbols += symtab->sh_entsize) {
        ElfSymbol* sym = (ElfSymbol*)symbols;
        if (sym->st_name != 0 && sym->st_value != 0) {
-            _cc->add(_base + sym->st_value, (int)sym->st_size, strings + sym->st_name);
+            // Skip special AArch64 mapping symbols: $x and $d
+            if (sym->st_size != 0 || sym->st_info != 0 || strings[sym->st_name] != '$') {
+                _cc->add(_base + sym->st_value, (int)sym->st_size, strings + sym->st_name);
+            }
        }
    }
 }
@@ -344,13 +440,32 @@ Mutex Symbols::_parse_lock;
 std::set<const void*> Symbols::_parsed_libraries;
 bool Symbols::_have_kernel_symbols = false;

-void Symbols::parseKernelSymbols(NativeCodeCache* cc) {
-    std::ifstream maps("/proc/kallsyms");
-    std::string str;
+void Symbols::parseKernelSymbols(CodeCache* cc) {
+    int fd;
+    if (FdTransferClient::hasPeer()) {
+        fd = FdTransferClient::requestKallsymsFd();
+    } else {
+        fd = open("/proc/kallsyms", O_RDONLY);
+    }

-    while (std::getline(maps, str)) {
-        str += "_[k]";
-        SymbolDesc symbol(str.c_str());
+    if (fd == -1) {
+        Log::warn("open(\"/proc/kallsyms\"): %s", strerror(errno));
+        return;
+    }
+
+    FILE* f = fdopen(fd, "r");
+    if (f == NULL) {
+        Log::warn("fdopen(): %s", strerror(errno));
+        close(fd);
+        return;
+    }
+
+    char str[256];
+    while (fgets(str, sizeof(str) - 8, f) != NULL) {
+        size_t len = strlen(str) - 1; // trim the '\n'
+        strcpy(str + len, "_[k]");
+
+        SymbolDesc symbol(str);
        char type = symbol.type();
        if (type == 'T' || type == 't' || type == 'W' || type == 'w') {
            const char* addr = symbol.addr();
@@ -360,48 +475,83 @@ void Symbols::parseKernelSymbols(NativeCodeCache* cc) {
            }
        }
    }
+
+    fclose(f);
 }

-void Symbols::parseLibraries(NativeCodeCache** array, volatile int& count, int size, bool kernel_symbols) {
+void Symbols::parseLibraries(CodeCacheArray* array, bool kernel_symbols) {
    MutexLocker ml(_parse_lock);

    if (kernel_symbols && !haveKernelSymbols()) {
-        NativeCodeCache* cc = new NativeCodeCache("[kernel]");
+        CodeCache* cc = new CodeCache("[kernel]");
        parseKernelSymbols(cc);

        if (haveKernelSymbols()) {
            cc->sort();
-            array[count] = cc;
-            atomicInc(count);
+            array->add(cc);
        } else {
            delete cc;
        }
    }

-    std::ifstream maps("/proc/self/maps");
-    std::string str;
+    FILE* f = fopen("/proc/self/maps", "r");
+    if (f == NULL) {
+        return;
+    }

-    while (count < size && std::getline(maps, str)) {
-        MemoryMapDesc map(str.c_str());
-        if (map.isExecutable() && map.file() != NULL && map.file()[0] != 0) {
-            const char* image_base = map.addr();
+    const char* last_readable_base = NULL;
+    const char* image_end = NULL;
+    char* str = NULL;
+    size_t str_size = 0;
+    ssize_t len;
+
+    while ((len = getline(&str, &str_size, f)) > 0) {
+        str[len - 1] = 0;
+
+        MemoryMapDesc map(str);
+        if (!map.isReadable() || map.file() == NULL || map.file()[0] == 0) {
+            continue;
+        }
+
+        const char* image_base = map.addr();
+        if (image_base != image_end) last_readable_base = image_base;
+        image_end = map.end();
+
+        if (map.isExecutable()) {
            if (!_parsed_libraries.insert(image_base).second) {
                continue;  // the library was already parsed
            }

-            NativeCodeCache* cc = new NativeCodeCache(map.file(), image_base, map.end());
+            int count = array->count();
+            if (count >= MAX_NATIVE_LIBS) {
+                break;
+            }
+
+            CodeCache* cc = new CodeCache(map.file(), count, image_base, image_end);

            if (map.inode() != 0) {
-                ElfParser::parseFile(cc, image_base - map.offs(), map.file(), true);
+                // Be careful: executable file is not always ELF, e.g. classes.jsa
+                if ((image_base -= map.offs()) >= last_readable_base) {
+                    ElfParser::parseProgramHeaders(cc, image_base);
+                }
+                ElfParser::parseFile(cc, image_base, map.file(), true);
            } else if (strcmp(map.file(), "[vdso]") == 0) {
                ElfParser::parseMem(cc, image_base);
            }

            cc->sort();
-            array[count] = cc;
-            atomicInc(count);
+            array->add(cc);
        }
    }
+
+    free(str);
+    fclose(f);
+}
+
+void Symbols::makePatchable(CodeCache* cc) {
+    uintptr_t got_start = (uintptr_t)cc->gotStart() & ~OS::page_mask;
+    uintptr_t got_size = ((uintptr_t)cc->gotEnd() - got_start + OS::page_mask) & ~OS::page_mask;
+    mprotect((void*)got_start, got_size, PROT_READ | PROT_WRITE);
 }

 #endif // __linux__
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Andrei Pangin	4a88ee445f	Release 2.8	2022-05-10 04:17:09 +03:00
Andrei Pangin	ce0fc0a2d9	Fixed musl	2022-05-10 04:04:05 +03:00
Andrei Pangin	768b437593	Missing headers	2022-05-09 22:56:41 +03:00
Andrei Pangin	20fa8564c4	Do not merge source files when building fat binary on macOS	2022-05-09 20:21:42 +03:00
Andrei Pangin	aaf24effe8	ARM32 and x86 pop frame support	2022-05-09 20:00:44 +03:00
Andrei Pangin	3bbeed6267	ARM64 pop frame support	2022-05-09 14:57:51 +03:00
Andrei Pangin	cb51be8eb3	Merge different frame types of the same method on the Flame Graph	2022-05-09 02:44:21 +03:00
Andrei Pangin	7749b72e73	Tree view colors	2022-05-08 18:27:42 +03:00
Andrei Pangin	7112bc14e5	Stack recovery fixes	2022-05-08 17:45:38 +03:00
Andrei Pangin	56ca88677b	Release 2.8-ea	2022-04-26 08:55:33 +03:00
Andrei Pangin	8a258d31a5	Show C1 compiled frames. Merge different compilation types on a flame graph.	2022-04-26 08:43:56 +03:00
Andrei Pangin	e33a01e0c6	Re-implemented stack recovery. Unwind native stacks manually before AGCT.	2022-04-26 08:37:22 +03:00
Andrei Pangin	5d5138ea61	Allow profiler server only at JVM startup	2022-04-24 16:15:31 +03:00
Andrei Pangin	10b5ad0ee5	#512 : Simple HTTP server for managing async-profiler	2022-04-24 03:10:49 +03:00
Andrei Pangin	b5258cca2c	JVM TI based allocation profiling fine tuning	2022-04-14 03:02:26 +03:00
Andrei Pangin	0718a09e0e	#169 : JVM TI based allocation profiling for JDK >= 11	2022-04-14 01:46:48 +03:00
Andrei Pangin	fe173c4101	#561 , #579 : Fixed concurrency issues when collecting samples / restarting profiler	2022-04-11 01:49:34 +03:00
Andrei Pangin	8032daa49d	--cpu converter option to extract CPU profile from the wall-clock output	2022-03-31 03:05:22 +03:00
Andrei Pangin	fa8b8f8072	#569 : Distinguish runnable/sleeping threads in OpenJ9 wall-clock profiler	2022-03-31 01:34:48 +03:00
Andrei Pangin	85f3a68c56	#570 : Display an error when using 'jfrsync' on JDK without Flight Recorder	2022-03-30 23:47:26 +03:00
Andrei Pangin	60ce15569a	#572 : Careful parsing of ELF Program Headers	2022-03-29 04:24:06 +03:00
Andrei Pangin	9838ddb693	#572 : CodeCache refactoring + parseProgramHeaders() fixes	2022-03-28 04:44:15 +03:00
Andrei Pangin	2f341043ef	#571 , #572 : Locate DWARF info and GOT/PLT from ELF Program Headers	2022-03-27 22:09:08 +03:00
Andrei Pangin	ee55fbe17b	#557 : Do not fail on unknown argument	2022-03-10 01:01:29 +03:00
Andrei Pangin	d7a2a4fc8b	Mark top methods as interpreted/compiled/inlined (#553 )	2022-02-21 04:58:19 +03:00
Andrei Pangin	e9b7747015	Do not mmap perf page in --all-user mode. cstack=fp forces manual stack walking.	2022-02-19 23:05:55 +03:00
Andrei Pangin	b96e07b001	List loglevel argument	2022-02-16 03:17:34 +03:00
Ludovic Henry	ba00ca26c1	Add loglevel argument (#551 )	2022-02-16 02:00:22 +03:00
Andrei Pangin	9ed175d73e	Updated links to 2.7 binaries	2022-02-14 02:29:33 +03:00
Andrei Pangin	b287816559	Release 2.7	2022-02-14 00:57:18 +03:00
Andrei Pangin	9a979a712d	OpenJ9-related fixes	2022-02-13 23:48:45 +03:00
Andrei Pangin	42442ed593	Fixed AllocTracer on ARM32	2022-02-13 21:59:59 +03:00
Andrei Pangin	432d622aa4	Follow-up to #537 : added a few comments	2022-02-13 20:36:46 +03:00
Gunter Haug	f477f8d4c0	Look in plt sections for the global offset table too (#537 ) Co-authored-by: Johannes Bechberger	2022-02-13 20:34:44 +03:00
Andrei Pangin	456ff57115	OpenJ9 fixes	2022-02-09 04:26:40 +03:00
Andrei Pangin	5ec28a86b2	#548 : syntax error in profiler.sh	2022-02-08 20:49:47 +03:00
Andrei Pangin	e7cd6ee6fb	OpenJ9 support	2022-02-01 16:04:48 +03:00
Andrei Pangin	8ba8fc748c	Minor DWARF fix	2022-01-28 03:42:19 +03:00
Andrei Pangin	5f37bf3ad6	DWARF unwinding used incorrect symbol base	2022-01-26 18:11:41 +03:00
Andrei Pangin	26e9c7aef2	DWARF stack walking fixes	2022-01-25 03:53:14 +03:00
Andrei Pangin	8efba10acc	JfrReader backward compatibility	2022-01-25 01:56:33 +03:00
Andrei Pangin	e894420119	#531 : Rewrite StackMapTable correctly	2022-01-23 01:23:25 +03:00
Andrei Pangin	2ddd4d230c	#416 : Improve reliability of stack recovery from [not_walkable_not_Java]	2022-01-21 08:55:09 +03:00
Andrei Pangin	1398e7ef75	#215 : DWARF stack unwinding	2022-01-20 03:45:37 +03:00
Andrei Pangin	3456dd3d90	Patch Global Offset Table to hook libc functions	2022-01-19 02:48:36 +03:00
Andrei Pangin	c0d45fecec	Updated links to version 2.6	2022-01-11 00:10:49 +03:00
Yonatan Goldschmidt	7e5f8a03f3	Fail arguments parsing upon unknown argument (#503 )	2022-01-10 03:58:33 +03:00
Andrei Pangin	ce91abe6d9	Do not show 'GC_active' for compiler threads	2022-01-10 01:48:13 +03:00
Andrei Pangin	4ba7524d7c	Release 2.6	2022-01-09 21:10:30 +03:00
Andrei Pangin	734ef03ebf	Include shared library names in JFR output	2022-01-08 04:08:24 +03:00
Andrei Pangin	cf17e5efc3	#513 : Protect native stack walking from crashes	2022-01-06 05:20:15 +03:00
Andrei Pangin	35b420a941	Compute FlameGraph depth when minwidth > 0	2022-01-06 01:35:27 +03:00
Andrei Pangin	ee4cd8e2b6	Revived workaround for slow JVM TI functions	2022-01-05 23:39:51 +03:00
Andrei Pangin	6f3134e99f	Pass chunksize & jstackdepth options to the Flight Recorder in jfrsync mode	2022-01-05 22:21:44 +03:00
Andrei Pangin	c537b8298d	Do not spoil VM.log decorators	2022-01-05 05:56:59 +03:00
Andrei Pangin	605550cf96	Off-by-one bug	2022-01-05 03:55:23 +03:00
Andrei Pangin	a57bbf3587	Optimize compilation with -fwhole-program	2022-01-04 02:17:30 +03:00
Andrei Pangin	9131344d61	Minor build system improvements	2022-01-01 21:54:39 +03:00
Andrei Pangin	2d0b9c9921	Avoid JVM crashes related to CompiledMethodLoad bugs and stack walking during GC	2022-01-01 21:34:01 +03:00
Andrei Pangin	30905fda4c	Faster compilation, smaller binary	2021-12-26 04:35:04 +03:00
Andrei Pangin	5a11a71db9	Fixed races between flush/stop. Possibility to set timeout as hh:mm:ss	2021-12-19 21:47:11 +03:00
Andrei Pangin	d79a82935f	Renamed 'duration' to 'timeout'	2021-12-15 03:41:39 +03:00
Andrei Pangin	995048c2fd	#71 : Continuous profiling	2021-12-15 03:28:24 +03:00
Andrei Pangin	7331e30ed5	JFR duration should be in nanos, not ticks	2021-12-12 03:06:20 +03:00
Andrei Pangin	1f5e4ca8aa	Parse recording settings in JfrReader	2021-12-12 03:05:16 +03:00
Andrei Pangin	7ebed4e8e1	Fixed links to 2.5.1 binaries	2021-12-07 03:09:43 +03:00
Andrei Pangin	170451990b	Release 2.5.1	2021-12-05 23:53:26 +03:00
Andrei Pangin	11a1d6d308	Read kernel symbols only for perf_events	2021-12-04 00:05:53 +03:00
Yonatan Goldschmidt	955413db8d	Remove double close() call (#514 )	2021-12-03 23:41:06 +03:00
Andrei Pangin	8a701b41e3	Fixed unsafe access to Recording fields	2021-12-03 04:09:14 +03:00
Andrei Pangin	dccd4c326a	Mark native functions. Redo ZeroInterpreter support.	2021-11-29 04:17:36 +03:00
Andrei Pangin	8771888d28	Make sure async-profiler DSO cannot be unloaded	2021-11-28 22:07:00 +03:00
Andrei Pangin	7d25210d2c	#506 : Throw exception if output size exceeds string limit	2021-11-27 20:29:30 +03:00
Yonatan Goldschmidt	9087bc57d8	Mmap perf_events pages in fdtransfer (#475 )	2021-11-15 23:47:03 +03:00
Andrei Pangin	3e1e1c614a	Fixed RedefineClasses recursion when loading via JNI	2021-11-02 16:02:46 +03:00
Yonatan Goldschmidt	b80d163699	Escape backslashes in flamegraph frame names (#487 )	2021-11-01 23:30:11 +03:00
Andrei Pangin	9705b66864	Minor rewording in README	2021-10-31 20:32:09 +03:00
Krzysztof Ślusarski	3c33c6aa47	Update README regarding the CodeCache flushing on Java method instrumentation (#483 )	2021-10-31 20:15:29 +03:00
Andrei Pangin	4af6b65268	Merge event types (avoid duplicate categories) in jfrsync mode	2021-10-20 02:38:38 +03:00
Andrei Pangin	03c7b36bca	Fixed deadlock between Profiler::stop() and flushJfr()	2021-10-20 01:36:17 +03:00
Aleksey Shipilëv	f8b15526b1	Handle OpenJDK C++ Interpreter (#474 )	2021-10-11 22:38:27 +03:00
Andrey Pangin	e519fd84c4	Allow JMC to read incomplete JFR recordings	2021-10-01 22:46:12 +03:00
Andrey Pangin	79e1017088	Fixed link to macOS binaries	2021-10-01 05:28:21 +03:00
Andrey Pangin	edbb9e7c03	Release 2.5	2021-10-01 05:22:27 +03:00
Andrey Pangin	7eb15cfcf0	Canvas height should not be more than 32767px	2021-10-01 04:38:18 +03:00
Andrey Pangin	eafbbaea8b	Avoid use of certain libstdc++ symbols	2021-10-01 02:42:33 +03:00
Andrey Pangin	d8228a1fec	#462 : An option to prepend library name to native symbols	2021-09-30 04:40:40 +03:00
Andrey Pangin	8a447481f8	#405 : Resolve symlinks to profiler.sh	2021-09-30 02:54:18 +03:00
Andrey Pangin	791077354e	Fixed wrong TSC frequency problem. Removed misleading CPUTimeStampCounter event.	2021-09-29 03:15:57 +03:00
Andrey Pangin	e071b9fa14	Use global CodeCache boundaries instead of _java_methods/_runtime_stubs where possible	2021-09-28 21:17:21 +03:00
Andrey Pangin	cc340923b9	#458 : Wrong 'Matched %' when searching flame graphs with large values	2021-09-23 01:05:59 +03:00
Andrey Pangin	9c333219b5	Parse incomplete JFR files	2021-09-23 01:03:23 +03:00
Andrey Pangin	9acf8c1648	Ticks vs. nanos fixes	2021-09-23 00:24:34 +03:00
Andrey Pangin	5570afed9d	Use RDTSC for JFR timestamps when possible	2021-09-21 05:33:22 +03:00
Andrey Pangin	975a506d83	Read JFR chunks lazily; support combined recordings	2021-09-20 01:42:42 +03:00
Andrey Pangin	09fb14bd87	Combine JFR recording with async-profiler samples in a single .jfr file	2021-09-19 22:45:01 +03:00
Andrey Pangin	3256d824de	The workaround for #295 didn't work sometimes	2021-09-16 01:05:23 +03:00
Andrey Pangin	cc98710a6f	[ppc64] Fixed native stack walking in wall-clock profiler	2021-09-12 02:44:58 +03:00
Gunter Haug	452f14c3d2	Port async-profiler 2.0 to Power Linux little endian (linuxppc64le) (#459 )	2021-09-11 16:54:26 +03:00
Andrey Pangin	be8bba1900	Fixed application termination during JFR profiling	2021-09-10 01:05:11 +03:00
Andrey Pangin	65b5356ace	Fixed sendfile() not working on 5.10+ kernels	2021-09-08 23:42:57 +03:00
Andrey Pangin	e91363c05a	Fixed compiler warning	2021-09-08 21:19:58 +03:00
Andrey Pangin	3e47bf7551	#454 : SCAN_STACK recovery results in impossible stack traces	2021-09-08 02:41:37 +03:00
Kirill Timofeev	9447068af3	`DCEVM` is also hotspot (#457 )	2021-09-07 19:11:27 +03:00
Andrey Pangin	7e750825da	Add lines/bci information in a Flame Graph	2021-09-06 03:57:48 +03:00
Andrey Pangin	eda5779552	Smallish naming and stylistic changes	2021-09-06 01:26:32 +03:00
Yonatan Goldschmidt	fc3b1ca84f	Profile low-privileged processes with perf_events (#411 )	2021-09-05 22:13:01 +03:00
Andrey Pangin	d13de48c0a	#402 : Changes in shared code required for ppc64le port	2021-09-05 21:15:46 +03:00
Andrey Pangin	552c699687	Fix package names for hidden/anonymous classes	2021-09-01 22:36:52 +03:00
Andrey Pangin	0fcc4d9bac	#360 : Chunked JFR. Support JFR files more than 2 GB.	2021-09-01 01:08:54 +03:00
Andrey Pangin	868bfec2a5	Dump results while profiling session is running. Switch JFR chunks.	2021-08-20 03:32:21 +03:00
Andrey Pangin	4a77d68bcb	Sync with jattach 2.0: psutil interface, better container support, Open9 VMs	2021-08-11 23:41:54 +03:00
Andrey Pangin	a38a375dc6	Compatibility with debug builds of JDK 8	2021-08-01 02:59:33 +03:00
Andrey Pangin	6bcd23fcf0	An option to group threads by scheduling policy	2021-07-29 01:06:04 +03:00
Andrey Pangin	8d2847a032	Updated the list of supported platforms	2021-07-28 01:20:12 +03:00
Andrey Pangin	e0998af713	Rework VM shutdown issue: avoid calling Profiler destructor	2021-07-19 02:42:31 +03:00
Andrey Pangin	01b3e6c517	Use standard JVM TI stack walker where possible. Record BCI in alloc/lock events	2021-07-11 20:13:27 +03:00
Andrey Pangin	def6eb4b1c	Profile concurrent locks without JVM symbols	2021-07-11 16:57:04 +03:00
Andrey Pangin	4032c56caf	Extend CompiledMethodLoad bug workaround to JDK < 11	2021-07-07 02:12:06 +03:00
Andrey Pangin	9b789f6516	Workaround JDK bug related to posting CompiledMethodLoad event	2021-07-07 00:28:34 +03:00
Andrey Pangin	6ddaf9ab71	Log messages in JFR. List native libraries in JFR.	2021-07-01 03:12:49 +03:00
Andrey Pangin	11131499ab	One more fix of the race condition during VM shutdown	2021-06-30 02:47:23 +03:00
Andrey Pangin	d2abac1c30	Fixed 'check' command for multi-event profiling	2021-06-14 23:50:17 +03:00
Andrey Pangin	b7e9079b52	Fixed possible access to freed memory caused by a race during VM shutdown	2021-06-14 00:11:44 +03:00
Andrey Pangin	ff49ccccb7	#390 : Fixes for macOS/M1 build. Sign macOS package.	2021-06-13 15:05:05 +03:00
Andrey Pangin	7dd075cca6	#440 : Fixed crash when RetransformClasses is called with invalid arguments	2021-06-09 19:30:11 +03:00
Simon Legner	bd8078bc11	Enable GitHub Actions (#435 )	2021-06-06 23:59:01 +03:00
Simon Legner	1622fe5d72	Travis CI: use Ubuntu 18.04 (Bionic Beaver) (#434 )	2021-06-06 22:46:07 +03:00
Andrey Pangin	44d7941728	#390 : Run profiler natively on Apple M1 chip	2021-05-30 20:07:15 +03:00
Andrey Pangin	d23b40048b	Removed stackFrame_aarch64 (to be re-implemented from scratch)	2021-05-30 20:03:10 +03:00
Andrey Pangin	3b2db709ff	#433 : Skip AArch64 mapping symbols	2021-05-30 02:26:14 +03:00
Andrey Pangin	096fc88c82	Attempt to read temporary output file through /proc/[pid]/root	2021-05-17 01:45:40 +03:00
Yonatan Goldschmidt	4b0303916d	Read log file via /proc/pid/root on Linux (#413 )	2021-05-17 01:33:17 +03:00
Andrey Pangin	9fb2ca800a	#414 : Warn about conflict with another agent	2021-05-12 23:50:57 +03:00
Andrey Pangin	d917cfdb63	#415 : Fixed escaping of ' character	2021-05-12 20:38:18 +03:00
Uri Baghin	f2006f3da1	Use time types instead of long. (#428 )	2021-05-09 23:09:17 +03:00
Andrey Pangin	c30b22f204	#419 : Count the specified argument of a function. Added munmap to the list of known functions	2021-05-03 03:04:27 +03:00
Andrey Pangin	f48ebcc72b	#418 : Cap Flame Graph height to 32767px	2021-05-03 00:10:55 +03:00
Andrey Pangin	339aee5cfc	#379 : Generate Flame Graph title depending on the event and --total	2021-05-02 23:37:15 +03:00
Andrey Pangin	cde3fae978	#423 : Use Java 6 target only when building 'release'	2021-04-29 04:14:19 +03:00
Andrey Pangin	91eab91634	#414 : Fixed infinite CodeCache growth	2021-04-11 22:44:00 +03:00
Andrey Pangin	3df00e3439	#150 : jfr2flame can produce Allocation and Lock flame graphs	2021-04-11 21:47:15 +03:00
Andrey Pangin	c66ac2cfd0	Removed unused function	2021-04-04 21:15:08 +03:00
Andrei Pangin	f236482228	Raw PMU events; kprobes & uprobes (#406 )	2021-03-28 23:35:08 +03:00
Andrey Pangin	3ff315ea8f	Release 2.0	2021-03-14 20:19:13 +03:00
Andrey Pangin	308074a9eb	Print error if JVM does not support Tool Interface (e.g. minimal VM)	2021-03-14 16:49:11 +03:00
Andrey Pangin	685da8d84f	Update native thread names on Zing	2021-03-14 16:29:26 +03:00
Andrey Pangin	bd7bf9726e	Add [unknown_Java] frame in safe mode	2021-03-14 15:22:34 +03:00
Andrey Pangin	034677435d	Fixed handling of some profiler.sh arguments	2021-03-14 14:49:17 +03:00
Andrey Pangin	89f7d34456	Added new safe mode for troubleshooting	2021-03-14 01:03:41 +03:00
Andrey Pangin	ec8a40431a	An alias for time-to-safepoint profiling: --ttsp	2021-03-13 01:17:19 +03:00
Andrey Pangin	81bc1f2df2	Support appending JFR profiles on 'resume' command	2021-03-13 00:46:43 +03:00
Andrey Pangin	40ff09a14f	Combine async-profiler recording with JDK Flight Recording	2021-03-13 00:14:52 +03:00
Andrey Pangin	d6de541799	Corrected README links	2021-03-04 00:44:33 +03:00
Andrey Pangin	b807987f1d	2.0 Release Candidate	2021-03-04 00:22:42 +03:00
Andrey Pangin	02875138f1	Updated README	2021-03-03 23:52:30 +03:00
Andrey Pangin	d1c19d1904	Updated CHANGELOG. New FlameGraph example	2021-03-03 04:14:51 +03:00
Andrey Pangin	cc2307b92c	'cstack' option now correctly works in multievent profiles	2021-03-03 00:39:47 +03:00
Andrey Pangin	b5d89fef29	--begin/--end compatibility with allocation profiling	2021-03-02 05:11:46 +03:00
Andrey Pangin	646a92e2a0	Improved CLI experience	2021-03-02 02:35:29 +03:00
Andrey Pangin	bcd2375f39	Merge branch 'master' into v2.0 # Conflicts: # CHANGELOG.md # Makefile # README.md	2021-03-01 04:49:53 +03:00
Andrey Pangin	3cbe6aec2f	Multievent fixes; 'alloc=bytes' and 'lock=duration' options	2021-03-01 04:41:00 +03:00
Andrey Pangin	2d51c07b23	Output profile in text format: traces + flat	2021-02-28 19:51:24 +03:00
Andrey Pangin	32ead969c1	Graceful handling of storage overflow	2021-02-28 00:38:00 +03:00
Andrey Pangin	de55fadbba	JFR writer fixes	2021-02-25 00:33:20 +03:00
Andrey Pangin	da0ac08c64	Correct PerfEvents stack traces when begin/end options are set	2021-02-24 08:02:13 +03:00
Andrey Pangin	5dd9e86a1d	Release 1.8.4	2021-02-24 02:50:58 +03:00
Andrey Pangin	81583b9af3	Merge branch 'master' into v2.0 # Conflicts: # src/profiler.cpp	2021-02-24 02:34:48 +03:00
Andrey Pangin	7ec5c195e7	Better error handling	2021-02-24 02:31:48 +03:00
Andrey Pangin	cb0f1eb72d	Fixed JDK 7 crash during wall-clock profiling	2021-02-20 03:41:37 +03:00
Andrey Pangin	051424890a	Recover stack traces below C1 Runtime stubs	2021-02-03 02:08:59 +03:00
Andrey Pangin	34daf4f540	#386 : Added a note about IntelliJ IDEA	2021-02-01 19:11:59 +03:00
				`@@ -0,0 +1 @@`
				`202,254,186,190,0,0,0,50,0,11,10,0,3,0,8,7,0,9,7,0,10,1,0,6,60,105,110,105,116,62,1,0,3,40,41,86,1,0,4,67,111,100,101,1,0,12,114,101,99,111,114,100,83,97,109,112,108,101,12,0,4,0,5,1,0,23,111,110,101,47,112,114,111,102,105,108,101,114,47,73,110,115,116,114,117,109,101,110,116,1,0,16,106,97,118,97,47,108,97,110,103,47,79,98,106,101,99,116,0,33,0,2,0,3,0,0,0,0,0,2,0,2,0,4,0,5,0,1,0,6,0,0,0,17,0,1,0,1,0,0,0,5,42,183,0,1,177,0,0,0,0,1,9,0,7,0,5,0,0,0,0,`