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Enabling Linux control group version 1 (cgroup v1)

As of OpenShift Container Platform 4.14, OpenShift Container Platform uses Linux control group version 2 (cgroup v2) in your cluster. If you are using cgroup v1 on OpenShift Container Platform 4.13 or earlier, migrating to OpenShift Container Platform 4.14 will not automatically update your cgroup configuration to version 2. A fresh installation of OpenShift Container Platform 4.14 will use cgroup v2 by default. However, you can enable Linux control group version 1 (cgroup v1) upon installation. Enabling cgroup v1 in OpenShift Container Platform disables all cgroup v2 controllers and hierarchies in your cluster.

cgroup v2 is the current version of the Linux cgroup API. cgroup v2 offers several improvements over cgroup v1, including a unified hierarchy, safer sub-tree delegation, new features such as Pressure Stall Information, and enhanced resource management and isolation. However, cgroup v2 has different CPU, memory, and I/O management characteristics than cgroup v1. Therefore, some workloads might experience slight differences in memory or CPU usage on clusters that run cgroup v2.

You can switch between cgroup v1 and cgroup v2, as needed, by editing the node.config object. For more information, see "Configuring the Linux cgroup on your nodes" in the "Additional resources" of this section.

Enabling Linux cgroup v1 during installation

You can enable Linux control group version 1 (cgroup v1) when you install a cluster by creating installation manifests.

Procedure

  1. Create or edit the node.config object to specify the v1 cgroup:

    apiVersion: config.openshift.io/v1
kind: Node
metadata:
  name: cluster
spec:
  cgroupMode: "v2"

  2. Proceed with the installation as usual.

Additional resources