docs/doc/source/usertasks/using-kubernetes-cpu-manager-static-policy.rst

Use Kubernetes CPU Manager Static Policy

You can launch a container pinned to a particular set of CPU cores using a Kubernetes CPU manager static policy.

You will need to enable this CPU management mechanism before applying a policy.

1. Define a container running a CPU stress command.

   Note

   • The pod will be pinned to the allocated set of CPUs on the host and have exclusive use of those CPUs if <resource:request:cpu> is equal to <resource:cpulimit>.
   • Resource memory must also be specified for guaranteed resource allocation.
   • Processes within the pod can float across the set of CPUs allocated to the pod, unless the application in the pod explicitly pins them to a subset of the CPUs.

   For example:

   % cat <<EOF > stress-cpu-pinned.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: stress-ng-cpu
   spec:
     containers:
     - name: stress-ng-app
       image: alexeiled/stress-ng
       imagePullPolicy: IfNotPresent
       command: ["/stress-ng"]
       args: ["--cpu", "10", "--metrics-brief", "-v"]
       resources:
         requests:
           cpu: 2
           memory: "2Gi"
         limits:
           cpu: 2
           memory: "2Gi"
     nodeSelector:
       kubernetes.io/hostname: worker-1
   EOF

   You will likely need to adjust some values shown above to reflect your deployment configuration. For example, on an AIO-SX or AIO-DX system. worker-1 would probably become controller-0 or controller-1.

   The significant addition to this definition in support of CPU pinning, is the resources section , which sets a CPU resource request and limit of 2.

2. Apply the definition.

   % kubectl apply -f stress-cpu-pinned.yaml

   You can SSH to the worker node and run top, and type '1' to see CPU details per core:

3. Describe the pod or node to see the CPU Request, CPU Limits and that it is in the "Guaranteed" QoS Class.

   For example:

   % kubectl describe <node>
   Namespace                  Name           CPU Requests  CPU Limits  Memory Requests  Memory Limits  AGE
   ---------                  ----           ------------  ----------  ---------------  -------------  ---
   default                    stress-ng-cpu  2 (15%)       2 (15%)     2Gi (7%)         2Gi (7%)       9m31s
   
   % kubectl describe <pod> stress-ng-cpu
   ...
   QoS Class: Guaranteed

4. Delete the container.

   % kubectl delete -f stress-cpu-pinned.yaml