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85 lines
2.2 KiB
Plaintext
85 lines
2.2 KiB
Plaintext
// Module included in the following assemblies:
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//
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// * nodes/nodes-cluster-overcommit.adoc
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// * post_installation_configuration/node-tasks.adoc
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[id="nodes-cluster-overcommit-node-enforcing_{context}"]
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= Disabling or enforcing CPU limits using CPU CFS quotas
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Nodes by default enforce specified CPU limits using the Completely Fair Scheduler (CFS) quota support in
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the Linux kernel.
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.Prerequisites
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. Obtain the label associated with the static Machine Config Pool CRD for the type of node you want to configure.
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Perform one of the following steps:
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.. View the Machine Config Pool:
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+
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[source,terminal]
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----
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$ oc describe machineconfigpool <name>
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----
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+
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For example:
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+
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[source,terminal]
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----
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$ oc describe machineconfigpool worker
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----
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+
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.Example output
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[source,terminal]
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----
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apiVersion: machineconfiguration.openshift.io/v1
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kind: MachineConfigPool
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metadata:
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creationTimestamp: 2019-02-08T14:52:39Z
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generation: 1
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labels:
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custom-kubelet: small-pods <1>
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----
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<1> If a label has been added it appears under `labels`.
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.. If the label is not present, add a key/value pair:
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+
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[source,terminal]
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----
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$ oc label machineconfigpool worker custom-kubelet=small-pods
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----
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.Procedure
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. Create a custom resource (CR) for your configuration change.
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+
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.Sample configuration for a disabling CPU limits
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[source,yaml]
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----
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apiVersion: machineconfiguration.openshift.io/v1
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kind: KubeletConfig
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metadata:
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name: disable-cpu-units <1>
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spec:
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machineConfigPoolSelector:
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matchLabels:
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custom-kubelet: small-pods <2>
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kubeletConfig:
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cpu-cfs-quota: <3>
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- "false"
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----
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<1> Assign a name to CR.
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<2> Specify the label to apply the configuration change.
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<3> Set the `cpu-cfs-quota` parameter to `false`.
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If CPU limit enforcement is disabled, it is important to understand the impact that will have on your node:
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- If a container makes a request for CPU, it will continue to be enforced by CFS
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shares in the Linux kernel.
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- If a container makes no explicit request for CPU, but it does specify a limit,
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the request will default to the specified limit, and be enforced by CFS shares
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in the Linux kernel.
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- If a container specifies both a request and a limit for CPU, the request will
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be enforced by CFS shares in the Linux kernel, and the limit will have no
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impact on the node.
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