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  1. OpenShift Bugs
  2. OCPBUGS-4362

Hard eviction thresholds is different with k8s default when PAO is enabled

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    • Previously, kubelet hard eviction thresholds were different from k8s defaults when a Performance profile was applied to a node. With this release, the defaults have been updated to match the expected kubernetes defaults.
    • Bug Fix
    • 12/19: per Martin, there's a simple workaround for this - just need to close on if that needs to be release noted or if the fix will land for 4.12

      This is a clone of issue OCPBUGS-2209. The following is the description of the original issue:
      —
      Description of problem:

      Hard eviction thresholds is different with k8s default when PAO is enabled. 

According to https://kubernetes.io/docs/concepts/scheduling-eviction/node-pressure-eviction/#hard-eviction-thresholds, the default Hard eviction thresholds in k8s are: 
memory.available<100Mi nodefs.available<10% imagefs.available<15% nodefs.inodesFree<5% (Linux nodes), but when PAO is enabled, the default setting is changed to memory.available<100Mi: https://github.com/openshift/cluster-node-tuning-operator/blob/master/pkg/performanceprofile/controller/performanceprofile/components/kubeletconfig/kubeletconfig.go#L59-L64

There is no doc mentioned this difference, considering 'nodefs.available<10%' will impact the calculation of node allocatable ephemeral-storage, the customer is seeing different allocatable ephemeral-storage with/without PAO enabled which brought confusions.

Considering there was no special reason to overwrite the default settings except that the kubeconfig needs a non-nil value as a default, and there is doc to describe that PAO would change the default behavior, this should be addressed.

      Version-Release number of selected component (if applicable):

       

      How reproducible:

      Always

      Steps to Reproduce:

      1. Prepare a OCP cluster
2. Install the PAO operator and create a performanceprofile
3.

      Actual results:

      The kubelet config contains a settings of  "evictionHard": { "memory.available": "100Mi"  }

      Expected results:

      The kubelet config should not change the k8s default evictionHard settings unless there is a reason

      Additional info:

       

              msivak@redhat.com Martin Sivak
              openshift-crt-jira-prow OpenShift Prow Bot
              Mallapadi Niranjan Mallapadi Niranjan
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                Created:
                Updated:
                Resolved: