Chapter 12. Optimizing memory management for workloads by using huge pages

Procedure

1. Create a hugepages-volume-pod.yaml file that is similar to the following example:

   apiVersion: v1
   kind: Pod
   metadata:
     generateName: hugepages-volume-
     labels:
       app: hugepages-example
   spec:
     containers:
     - securityContext:
         capabilities:
           add: [ "IPC_LOCK" ]
       image: rhel7:latest
       command:
       - sleep
       - inf
       name: example
       volumeMounts:
       - mountPath: /dev/hugepages
         name: hugepage
       - mountPath: /etc/podinfo
         name: podinfo
       resources:
         limits:
           hugepages-1Gi: 2Gi
           memory: "1Gi"
           cpu: "1"
         requests:
           hugepages-1Gi: 2Gi
       env:
       - name: REQUESTS_HUGEPAGES_1GI
         valueFrom:
           resourceFieldRef:
             containerName: example
             resource: requests.hugepages-1Gi
     volumes:
     - name: hugepage
       emptyDir:
         medium: HugePages
     - name: podinfo
       downwardAPI:
         items:
           - path: "hugepages_1G_request" <.>
             resourceFieldRef:
               containerName: example
               resource: requests.hugepages-1Gi
               divisor: 1Gi

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   where:

   spec.containers.securityContext.env.name

   Specifies what resource to read and use from requests.hugepages-1Gi and expose the value as the REQUESTS_HUGEPAGES_1GI environment variable.

   spec.volumes.name.items.path

   Specifies what resource to read and use from requests.hugepages-1Gi and expose the value as the file /etc/podinfo/hugepages_1G_request.

2. Create the pod from the hugepages-volume-pod.yaml file by entering the following command:

   $ oc create -f hugepages-volume-pod.yaml

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Verification

1. Check the value of the REQUESTS_HUGEPAGES_1GI environment variable:

   $ oc exec -it $(oc get pods -l app=hugepages-example -o jsonpath='{.items[0].metadata.name}') \
        -- env | grep REQUESTS_HUGEPAGES_1GI

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   Example output

   REQUESTS_HUGEPAGES_1GI=2147483648

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2. Check the value of the /etc/podinfo/hugepages_1G_request file:

   $ oc exec -it $(oc get pods -l app=hugepages-example -o jsonpath='{.items[0].metadata.name}') \
        -- cat /etc/podinfo/hugepages_1G_request

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   Example output

   2

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Procedure

1. Label all nodes that need the same huge pages setting by a label by entering the following command:

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

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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
     namespace: openshift-cluster-node-tuning-operator
   spec:
     profile:
     - data: |
         [main]
         summary=Boot time configuration for hugepages
         include=openshift-node
         [bootloader]
         cmdline_openshift_node_hugepages=hugepagesz=2M hugepages=50
       name: openshift-node-hugepages
   
     recommend:
     - machineConfigLabels:
         machineconfiguration.openshift.io/role: "worker-hp"
       priority: 30
       profile: openshift-node-hugepages
   # ...

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   where:

   metadata.name

   Specifies the name of the Tuned resource to hugepages.

   spec.profile

   Specifies the profile section to allocate huge pages.

   spec.profile.data

   Specifies the order of parameters. The order is important as some platforms support huge pages of various sizes.

   spec.recommend.machineConfigLabels

   Specifies the enablement of a machine config pool based matching.

3. Create the Tuned hugepages object by entering the following command:

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

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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: ""

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5. Create the machine config pool by entering the following command:

   $ oc create -f hugepages-mcp.yaml

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Procedure

1. Create a file with the following content and name it thp-disable-tuned.yaml:

   apiVersion: tuned.openshift.io/v1
   kind: Tuned
   metadata:
     name: thp-workers-profile
     namespace: openshift-cluster-node-tuning-operator
   spec:
     profile:
     - data: |
         [main]
         summary=Custom tuned profile for OpenShift to turn off THP on worker nodes
         include=openshift-node
   
         [vm]
         transparent_hugepages=never
       name: openshift-thp-never-worker
   
     recommend:
     - match:
       - label: node-role.kubernetes.io/worker
       priority: 25
       profile: openshift-thp-never-worker
   # ...

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2. Create the Tuned object by entering the following command:

   $ oc create -f thp-disable-tuned.yaml

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3. Check the list of active profiles by entering the following command::

   $ oc get profile -n openshift-cluster-node-tuning-operator

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