Chapter 12. What huge pages do and how they are consumed by applications

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

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

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

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

   Example output

   REQUESTS_HUGEPAGES_1GI=2147483648

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

   Example output

   2

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 object

   $ 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

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

2. Create the Tuned object:

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

3. Check the list of active profiles:

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