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[enterprise-4.5] Limit ranges are being applied with cpu-cfs-quota set to false #29824

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vikram-redhat merged 1 commit into from
Feb 24, 2021
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[enterprise-4.5] Limit ranges are being applied with cpu-cfs-quota set to false #29824

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15 changes: 8 additions & 7 deletions modules/nodes-cluster-overcommit-node-enforcing.adoc
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Expand Up @@ -9,6 +9,12 @@

Nodes by default enforce specified CPU limits using the Completely Fair Scheduler (CFS) quota support in the Linux kernel.

If you disable CPU limit enforcement, it is important to understand the impact on your node:

* If a container has a CPU request, the request continues to be enforced by CFS shares in the Linux kernel.
* If a container does not have a CPU request, but does have a CPU limit, the CPU request defaults to the specified CPU limit, and is enforced by CFS shares in the Linux kernel.
* If a container has both a CPU request and limit, the CPU request is enforced by CFS shares in the Linux kernel, and the CPU limit has no impact on the node.

.Prerequisites

. Obtain the label associated with the static `MachineConfigPool` CRD for the type of node you want to configure. Perform one of the following steps:
Expand Down Expand Up @@ -63,15 +69,10 @@ spec:
matchLabels:
custom-kubelet: small-pods <2>
kubeletConfig:
cpu-cfs-quota: <3>
cpuCfsQuota: <3>
- "false"
----
<1> Assign a name to CR.
<2> Specify the label to apply the configuration change.
<3> Set the `cpu-cfs-quota` parameter to `false`.

If CPU limit enforcement is disabled, it is important to understand the impact that will have on your node:
<3> Set the `cpuCfsQuota` parameter to `false`.

* If a container makes a request for CPU, it will continue to be enforced by CFS shares in the Linux kernel.
* If a container makes no explicit request for CPU, but it does specify a limit, the request will default to the specified limit, and be enforced by CFS shares in the Linux kernel.
* If a container specifies both a request and a limit for CPU, the request will be enforced by CFS shares in the Linux kernel, and the limit will have no impact on the node.