OpenShift Container Platform

Enable 64k pages on the Red Hat Enterprise Linux CoreOS (RHCOS) kernel

You can enable the 64k memory page in the Red Hat Enterprise Linux CoreOS (RHCOS) kernel on the 64-bit ARM compute machines in your cluster. The 64k page size kernel specification can be used for large GPU or high memory workloads.

This configuration is possible by using the Machine Config Operator (MCO), which uses a machine config pool to update the kernel. To enable 64k page sizes on ARM64, create a dedicated MachineConfigPool and apply the 64k kernel configuration to it.

Using 64k pages is exclusive to 64-bit ARM architecture compute nodes or clusters installed on 64-bit ARM machines. If you configure the 64k pages kernel on a machine config pool using 64-bit x86 machines, the machine config pool and the MCO degrades.

Prerequisites

You installed the OpenShift CLI (oc).
You created a cluster with compute nodes of different architecture on one of the supported platforms.

Procedure

Label the nodes where you want to run the 64k page size kernel:

$ oc label node <node_name> <label>

Example command

$ oc label node worker-arm64-01 node-role.kubernetes.io/worker-64k-pages=

Create a machine config pool that contains the worker role that uses the ARM64 architecture and the worker-64k-pages role:

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  name: worker-64k-pages
spec:
  machineConfigSelector:
    matchExpressions:
      - key: machineconfiguration.openshift.io/role
        operator: In
        values:
        - worker
        - worker-64k-pages
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/worker-64k-pages: ""
      kubernetes.io/arch: arm64

Create a machine config on your compute node to enable 64k-pages with the 64k-pages parameter.
```
$ oc create -f <filename>.yaml
```
Example MachineConfig
```
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: "worker-64k-pages"
  name: 99-worker-64kpages
spec:
  kernelType: 64k-pages
```
where:

metadata.labels.machineconfiguration.openshift.io/role

Specifies the value of the machineconfiguration.openshift.io/role label in the custom machine config pool. The example MachineConfig uses the worker-64k-pages label to enable 64k pages in the worker-64k-pages pool.

spec.kernelType

Specifies your desired kernel type. Valid values are 64k-pages and default.

The 64k-pages type is supported on only 64-bit ARM architecture based compute nodes. The realtime type is supported on only 64-bit x86 architecture based compute nodes.

Verification

To view your new worker-64k-pages machine config pool, run the following command:

$ oc get mcp

Example output

NAME     CONFIG                                                                UPDATED   UPDATING   DEGRADED   MACHINECOUNT   READYMACHINECOUNT   UPDATEDMACHINECOUNT   DEGRADEDMACHINECOUNT   AGE
master   rendered-master-9d55ac9a91127c36314e1efe7d77fbf8                      True      False      False      3              3                   3                     0                      361d
worker   rendered-worker-e7b61751c4a5b7ff995d64b967c421ff                      True      False      False      7              7                   7                     0                      361d
worker-64k-pages  rendered-worker-64k-pages-e7b61751c4a5b7ff995d64b967c421ff   True      False      False      2              2                   2                     0                      35m