> For the complete documentation index, see [llms.txt](https://kubevirtlegacy.gitbook.io/user-guide/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kubevirtlegacy.gitbook.io/user-guide/docs/virtual_machines/numa.md).

# NUMA

**FEATURE STATE:** KubeVirt v0.43

NUMA support in KubeVirt is at this stage limited to a small set of special use-cases and will improve over time together with improvements made to Kubernetes.

In general, the goal is to map the host NUMA topology as efficiently as possible to the Virtual Machine topology to improve the performance.

The following NUMA mapping strategies can be used:

* [**GuestMappingPassthrough**](/user-guide/docs/virtual_machines/numa.md#GuestMappingPassthrough)

## Preconditions

In order to use current NUMA support, the following preconditions must be met:

* [Dedicated CPU Resources](/user-guide/docs/virtual_machines/dedicated_cpu_resources.md) must be configured.
* [Hugepages](/user-guide/docs/virtual_machines/virtual_hardware.md#Hugepages) need to be allocatable on target

  nodes.
* The `NUMA`

  [feature gate](/user-guide/docs/operations/activating_feature_gates.md#how-to-activate-a-feature-gate)

  must be enabled.

## GuestMappingPassthrough

GuestMappingPassthrough will pass through the node numa topology to the guest. The topology is based on the dedicated CPUs which the VMI got assigned from the kubelet via the CPU Manager. It can be requested by setting `spec.domain.cpu.guestMappingPassthrough` on the VMI.

Since KubeVirt does not know upfront which exclusive CPUs the VMI will get from the kubelet, there are some limitations:

* Guests may see different NUMA topologies when being rescheduled.
* The resulting NUMA topology may be asymmetrical.
* The VMI may fail to start on the node if not enough hugepages are available on

  the assigned NUMA nodes.

While this NUMA modelling strategy has its limitations, aligning the guest's NUMA architecture with the node's can be critical for high-performance applications.

An example VMI may look like this:

```yaml
apiVersion: kubevirt.io/v1
kind: VirtualMachineInstance
metadata:
  name: numavm
spec:
  domain:
    cpu:
      cores: 4
      dedicatedCpuPlacement: true
      numa:
        guestMappingPassthrough: { }
    devices:
      disks:
        - disk:
            bus: virtio
          name: containerdisk
        - disk:
            bus: virtio
          name: cloudinitdisk
    resources:
      requests:
        memory: 64Mi
    memory:
      hugepages:
        pageSize: 2Mi
  volumes:
    - containerDisk:
        image: quay.io/kubevirt/cirros-container-disk-demo
      name: containerdisk
    - cloudInitNoCloud:
        userData: |
          #!/bin/sh
          echo 'printed from cloud-init userdata'
      name: cloudinitdisk
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://kubevirtlegacy.gitbook.io/user-guide/docs/virtual_machines/numa.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.