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Graham Whaley
c846e9753d
Add library code that can generate a variety of cpu loads across the cluster. Configuration is via environment variables, documented in the .md file. Signed-off-by: Graham Whaley <graham.whaley@intel.com>
82 lines
3.5 KiB
Markdown
82 lines
3.5 KiB
Markdown
# `cpu-load` stack stresser
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The `cpu-load` stress functionality of the scaling framework allows you to optionally add a constant CPU stress
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load to cluster under test whilst the tests are running. This aids impact analysis of CPU load.
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The `cpu-load` functionality utilises the [`stress-ng`](https://kernel.ubuntu.com/git/cking/stress-ng.git/) tool
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to generate the CPU load. Some of the configuration parameters are taken directoy from the `stress-ng` command line.
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## Configuration
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`cpu-load` is configured via a number of environment variables:
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| Tool | Description |
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| ---- | ----------- |
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| collectd | `collectd` based statistics/metrics gathering daemonset code |
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| lib | General library helper functions for forming and launching workloads, and storing results in a uniform manner to aid later analysis |
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| report | Rmarkdown based report generator, used to produce a PDF comparison report of 1 or more sets of results |
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| scaling | Tests to measure scaling, such as linear or parallel launching of pods |
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| Variable | Description | Default |
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| -------- | ----------- | ------- |
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| `SMF_CPU_LOAD_NODES` | Set to non-empty to deploy `cpu-load` stressor | unset (off) |
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| `SMF_CPU_LOAD_NODES_NCPU` | Number of stressor threads to launch per node | 0 (one per cpu) |
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| `SMF_CPU_LOAD_NODES_PERCENT` | Percentage of CPU to load | unset (100%) |
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| `SMF_CPU_LOAD_NODES_LIMIT` | k8s cpu resource limit to set | unset (none) |
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| `SMF_CPU_LOAD_NODES_REQUEST` | k8s cpu resource request to set | unset (none) |
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| `cpu_load_post_deploy_sleep` | Seconds to sleep for `cpu-load` deployment to settle | 30 |
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`SMF_CPU_LOAD_NODES` must be set to a non-empty string to enable the `cpu-load` functionality. `cpu-load` uses
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a daemonSet to deploy one `stress-ng` single container pod to each active node in the cluster.
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Any of the `SMF_CPU_LOAD_NODES_*` variables can be set, or unset, and the daemonSet pods will be configured
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appropriately.
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## Examples
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The combinations of settings available allow a lot of flexibility. Below are some common example setups:
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### 50% CPU load on all cores of all nodes (`stress-ng`)
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Here we allow `stress-ng` to spawn workers to cover all the CPUs on each node, but ask it to restrict its
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bandwidth use to 50% of the CPU. We do not use the k8s limits.
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```bash
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export SMF_CPU_LOAD_NODES=true
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#export SMF_CPU_LOAD_NODES_NCPU=
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export SMF_CPU_LOAD_NODES_PERCENT=50
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#export SMF_CPU_LOAD_NODES_LIMIT=999m
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#export SMF_CPU_LOAD_NODES_REQUEST=999m
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```
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### 50% CPU load on 1 un-pinned core of all nodes (k8s `limits`)
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Here we set `stress-ng` to run a single worker thread at 100% CPU, but use the k8s resource limits to restrict
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actual CPU usage to 50%. Because the k8s limit and request are not whole interger units, if the static policy is
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in place on the k8s cluster, the pods will be classified as Guaranteed QoS, but will *not* get pinned to a specific
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cpuset.
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```bash
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export SMF_CPU_LOAD_NODES=true
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export SMF_CPU_LOAD_NODES_NCPU=1
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export SMF_CPU_LOAD_NODES_PERCENT=100
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export SMF_CPU_LOAD_NODES_LIMIT=500m
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export SMF_CPU_LOAD_NODES_REQUEST=500m
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```
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### 50% CPU load pinned to 1 core, on all nodes
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Here we set `stress-ng` to run a single worker thread at 50% CPU, and use the k8s resource limits to classify the
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pod as Guaranteed, and as we are using whole integer units of CPU resource requests, if the static policy manager is
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in play, the thread will be pinned to a single cpu cpuset.
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```bash
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export SMF_CPU_LOAD_NODES=true
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export SMF_CPU_LOAD_NODES_NCPU=1
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export SMF_CPU_LOAD_NODES_PERCENT=50
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export SMF_CPU_LOAD_NODES_LIMIT=1
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export SMF_CPU_LOAD_NODES_REQUEST=1
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```
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