13.3. Configuring huge pages

Nodes must pre-allocate huge pages used in an OpenShift Container Platform cluster. There are two ways of reserving huge pages: at boot time and at run time. Reserving at boot time increases the possibility of success because the memory has not yet been significantly fragmented. The Node Tuning Operator currently supports boot time allocation of huge pages on specific nodes.

13.3.1. At boot time

Procedure

To minimize node reboots, the order of the steps below needs to be followed:

  1. Label all nodes that need the same huge pages setting by a label. 

    $ oc label node <node_using_hugepages> node-role.kubernetes.io/worker-hp=

  2. Create a file with the following content and name it hugepages-tuned-boottime.yaml: 

    apiVersion: tuned.openshift.io/v1
kind: Tuned
metadata:
  name: hugepages 1
  namespace: openshift-cluster-node-tuning-operator
spec:
  profile: 2
  - data: |
      [main]
      summary=Boot time configuration for hugepages
      include=openshift-node
      [bootloader]
      cmdline_openshift_node_hugepages=hugepagesz=2M hugepages=50 3
    name: openshift-node-hugepages

  recommend:
  - machineConfigLabels: 4
      machineconfiguration.openshift.io/role: "worker-hp"
    priority: 30
    profile: openshift-node-hugepages
    1
    Set the name of the Tuned resource to hugepages.
    2
    Set the profile section to allocate huge pages.
    3
    Note the order of parameters is important as some platforms support huge pages of various sizes.
    4
    Enable machine config pool based matching.

  3. Create the Tuned hugepages profile 

    $ oc create -f hugepages-tuned-boottime.yaml

  4. Create a file with the following content and name it hugepages-mcp.yaml: 

    apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
metadata:
  name: worker-hp
  labels:
    worker-hp: ""
spec:
  machineConfigSelector:
    matchExpressions:
      - {key: machineconfiguration.openshift.io/role, operator: In, values: [worker,worker-hp]}
  nodeSelector:
    matchLabels:
      node-role.kubernetes.io/worker-hp: ""

  5. Create the machine config pool: 

    $ oc create -f hugepages-mcp.yaml

Given enough non-fragmented memory, all the nodes in the worker-hp machine config pool should now have 50 2Mi huge pages allocated. 

$ oc get node <node_using_hugepages> -o jsonpath="{.status.allocatable.hugepages-2Mi}"
100Mi
警告

This functionality is currently only supported on Red Hat Enterprise Linux CoreOS (RHCOS) 8.x worker nodes. On Red Hat Enterprise Linux (RHEL) 7.x worker nodes the Tuned [bootloader] plug-in is currently not supported.