Adds hugepages config guide to explain defaults and config settings (#1061)

* Adds hugepages config guide to explain defaults and config settings Closes #1005 Signed-off-by: Adams, Eric <eric.adams@intel.com> * Made revisions per feedback from reviewer. Signed-off-by: Adams, Eric <eric.adams@intel.com>
2026-08-26 18:36:02 +00:00 · 2020-03-06 15:26:02 -08:00
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+.. _enable-huge-pages:
+
+Configure Huge Pages
+########################
+
+In |CL| hugepages are enabled by default. The default hugepage size is 2MB. 
+The total number of hugepages is set to 0 by default. This guide shows you how
+to add hugepages to the system and how to change the default hugepage size. 
+
+#. To check the enabled state, run the following command.
+
+   .. code-block:: bash
+   
+      cat /sys/kernel/mm/transparent_hugepage/enabled
+
+   The output will look like
+ 
+   .. code-block:: console
+
+      [always] madvise never
+
+   .. note::
+      
+      The active option is enclosed in brackets. In this case, always is active, 
+      which means hugepages are enabled for every process. The `madvise` 
+      option means that hugepages are enabled for processes that explicitely 
+      call `madvise`_. 
+
+#. To check the size of hugepages, run the below command.
+
+   .. code-block:: bash
+
+      cat /proc/meminfo | grep Huge
+
+   The output should look similar to the following. Although hugepages is 
+   enabled, there are no hugepages available to allocate.
+
+   .. code-block:: console
+
+      AnonHugePages:    624640 kB
+      ShmemHugePages:        0 kB
+      FileHugePages:         0 kB
+      HugePages_Total:       0
+      HugePages_Free:        0
+      HugePages_Rsvd:        0
+      HugePages_Surp:        0
+      Hugepagesize:       2048 kB
+      Hugetlb:               0 kB
+
+#. If you need 1GB (1,048,576 bytes) of hugepages enabled, then `HugePages_Total`
+   should be set to 512. Enable it temporarily using the following.
+
+   .. code-block:: bash
+
+      echo 512 | sudo tee /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
+
+   To view the change, run the command in the previous setp again.
+
+#. Changing hugepages from the default 2MB to 1GB must be done at system boot
+   through kernel boot parameters. In this example, we configure the size and 
+   number of allocatable huge pages at boot.
+
+   .. code-block:: bash
+    
+      sudo mkdir -p /etc/kernel/cmdline.d
+      cat << EOF | sudo tee -a /etc/kernel/cmdline.d/hugepages.conf
+      default_hugepagesz=1G
+      hugepagesz=1G
+      hugepages=10
+      EOF
+      sudo clr-boot-manager update
+      sudo reboot
+
+   .. _madvise: https://linux.die.net/man/2/madvise