How to get exclusive core for Pod in Kubernetes?-CodePudding

I have a cluster and set up kubelet on a node (name is myNode) with the static CPU Manager Policy. So I've started kubelet with --cpu-manager-policy=static (to set the static policy) and --reserved-cpus=1 (to make sure kubelet has one core to run on exclusively) as explained here.

Checking /var/lib/kubelet/cpu_manager_state it gives me

cat /var/lib/kubelet/cpu_manager_state
{"policyName":"static","defaultCpuSet":"0-3","checksum":611748604}

which should be fine. I then start a pod with the following pod spec

apiVersion: v1
kind: Pod
metadata:
  name: wl
  labels:
    app: wl
spec:
  containers:
  - name: wl
    image: docker.io/polinux/stress:latest
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c"]
    args: ["echo 'workload' && stress --cpu 4"]
    resources:
      requests:
        cpu: 1
      limits:
        cpu: 1
  nodeName: myNode

and start it. It get's scheduled on the desired node "myNode". I then check for the processes with

ps aux | grep stress
root     2966141  0.2  0.0    780     4 ?        Ss   10:54   0:00 stress --cpu 4
root     2966154 27.1  0.0    780    36 ?        R    10:54   0:02 stress --cpu 4
root     2966155 26.7  0.0    780    36 ?        R    10:54   0:02 stress --cpu 4
root     2966156 28.6  0.0    780    36 ?        R    10:54   0:02 stress --cpu 4
root     2966157 27.3  0.0    780    36 ?        R    10:54   0:02 stress --cpu 4

and then which CPUs they are running on with

ps -o pid,psr,comm -p 2966154 2966155 2966156 2966157
    PID PSR COMMAND
2966154   0 stress
2966155   1 stress
2966156   2 stress
2966157   3 stress

It looks like there are 4 processes running, but all of them on different CPUs. I would have expected that the Pod fails to run since it's allowed to only run on one core while the stress --cpu 4 wants to start 4 threads on 4 CPUs. With the default CPU Manager Policy, this would be the expected behavior, but I've configured the static one.

Any hint what the problem could be?

CodePudding user response：

You also need to provide memory request and limit in order to qualify for the Guaranteed tier and exclusive cores:

apiVersion: v1
kind: Pod
metadata:
  name: wl
  labels:
    app: wl
spec:
  containers:
  - name: wl
    image: docker.io/polinux/stress:latest
    imagePullPolicy: IfNotPresent
    command: ["/bin/sh","-c"]
    args: ["echo 'workload' && stress --cpu 4"]
    resources:
      requests:
        cpu: "1"
        memory: "200Mi"
      limits:
        cpu: "1"
        memory: "200Mi"
  nodeName: myNode

Verify the Pod by kubectl describe pod wl