website/content/en/docs/tasks/manage-hugepages/scheduling-hugepages.md

reviewers	title	content_template
derekwaynecarr	Manage HugePages	templates/task

{{% capture overview %}} {{< feature-state state="stable" >}}

Kubernetes supports the allocation and consumption of pre-allocated huge pages by applications in a Pod as a GA feature. This page describes how users can consume huge pages and the current limitations.

{{% /capture %}}

{{% capture prerequisites %}}

1. Kubernetes nodes must pre-allocate huge pages in order for the node to report its huge page capacity. A node may only pre-allocate huge pages for a single size.

The nodes will automatically discover and report all huge page resources as a schedulable resource.

{{% /capture %}}

{{% capture steps %}}

API

Huge pages can be consumed via container level resource requirements using the resource name hugepages-<size>, where size is the most compact binary notation using integer values supported on a particular node. For example, if a node supports 2048KiB page sizes, it will expose a schedulable resource hugepages-2Mi. Unlike CPU or memory, huge pages do not support overcommit. Note that when requesting hugepage resources, either memory or CPU resources must be requested as well.

apiVersion: v1
kind: Pod
metadata:
  generateName: hugepages-volume-
spec:
  containers:
  - image: fedora:latest
    command:
    - sleep
    - inf
    name: example
    volumeMounts:
    - mountPath: /hugepages
      name: hugepage
    resources:
      limits:
        hugepages-2Mi: 100Mi
        memory: 100Mi
      requests:
        memory: 100Mi      
  volumes:
  - name: hugepage
    emptyDir:
      medium: HugePages

• Huge page requests must equal the limits. This is the default if limits are specified, but requests are not.
• Huge pages are isolated at a pod scope, container isolation is planned in a future iteration.
• EmptyDir volumes backed by huge pages may not consume more huge page memory than the pod request.
• Applications that consume huge pages via shmget() with SHM_HUGETLB must run with a supplemental group that matches proc/sys/vm/hugetlb_shm_group.
• Huge page usage in a namespace is controllable via ResourceQuota similar to other compute resources like cpu or memory using the hugepages-<size> token.

Future

• Support container isolation of huge pages in addition to pod isolation.
• NUMA locality guarantees as a feature of quality of service.
• LimitRange support.

{{% /capture %}}