# Noisy neighbor

## Synopsis

display name: `Noisy Neighbor`

goal: `noisy_neighbor`

> Noisy Neighbor strategy using live migration

> Description

> This strategy can identify and migrate a Noisy Neighbor - a low priority VM that negatively affects performance of a high priority VM in terms of IPC by over utilizing Last Level Cache.

> Requirements

> To enable LLC metric, latest Intel server with CMT support is required.

> Limitations

> This is a proof of concept that is not meant to be used in production

> Spec URL

> http://specs.openstack.org/openstack/watcher-specs/specs/pike/implemented/noisy_neighbor_strategy.html

## Requirements

### Metrics

The noisy_neighbor strategy requires the following metrics:

metric | service name | plugins | comment
--- | --- | --- | ---
`cpu_l3_cache` | ceilometer | none | Intel CMT is required

### Cluster data model

Default Watcher’s Compute cluster data model:

> Nova cluster data model collector

> The Nova cluster data model collector creates an in-memory representation of the resources exposed by the compute service.

### Actions

Default Watcher’s actions:

> action | description
> --- | ---

> `migration`

> Migrates a server to a destination nova-compute host

> This action will allow you to migrate a server to another compute destination host. Migration type ‘live’ can only be used for migrating active VMs. Migration type ‘cold’ can be used for migrating non-active VMs as well active VMs, which will be shut down while migrating.

> The action schema is:

>     schema = Schema({
>      'resource_id': str,  # should be a UUID
>      'migration_type': str,  # choices -> "live", "cold"
>      'destination_node': str,
>      'source_node': str,
>     })

> The resource_id is the UUID of the server to migrate. The source_node and destination_node parameters are respectively the source and the destination compute hostname (list of available compute hosts is returned by this command: `nova service-list --binary nova-compute`).

> Note

> Nova API version must be 2.56 or above if destination_node parameter is given.

### Planner

Default Watcher’s planner:

> Weight planner implementation

> This implementation builds actions with parents in accordance with weights. Set of actions having a higher weight will be scheduled before the other ones. There are two config options to configure: action_weights and parallelization.

> Limitations

> - This planner requires to have action_weights and parallelization configs tuned well.

## Configuration

Strategy parameter is:

parameter | type | default | Value description
--- | --- | --- | ---
`cache_threshold` | Number | 35.0 | Performance drop in L3_cache threshold for migration

## Efficacy Indicator

None

## Algorithm

For more information on the noisy neighbor strategy please refer to: http://specs.openstack.org/openstack/watcher-specs/specs/pike/implemented/noisy_neighbor_strategy.html

## How to use it ?

    $ openstack optimize audittemplate create \
      at1 noisy_neighbor --strategy noisy_neighbor

    $ openstack optimize audit create -a at1 \
      -p cache_threshold=45.0

## External Links

None

this page last updated: 2026-05-26 14:30:00

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