# Topology Manager

The Topology Manager incorporates data from the CPU Manager and other device plugins when making decisions about pod placement. Without topology manager, CPU Manager and Device Manager make decisions independently and this can result in pod placements that are undesirable.

PMK now supports configuration of Topology Manager. The following fields are added to the cluster create API of **qbert**:

{% tabs %}
{% tab title="JSON" %}

```json
cpuManagerPolicy: {type: string, description: "options: none, static; default: none"},

topologyManagerPolicy: {type: string, description: "options: none, best-effort, restricted, single-numa-node; default: none"},

reservedCPUs: {type: string, description: "list of CPUs to be reserved for the system. Ex: 1-3,5"}
```

{% endtab %}
{% endtabs %}

The default value of the "cpuManagerPolicy" : "`none"` and will work for most applications.

When "`cpuManagerPolicy": "static"`turns on CPU Manager. This is required for Topology Manager to work.

Furthermore the `"topologyManagerPolicy"` supports the following options:

`* none`: Topology Manager is turned off

`* best-effort`: Kubelet uses hint providers to determine the best placement location for a pod. The pod is scheduled even if all affinity requirements are not met.

`* restricted`: Kubelet uses hint providers to determine the best placement location for a pod. The pod is terminated if such a node matching all affinity requirements are not met

`* single-numa-node`: Kubelet uses hint providers to find a single numa node that meets all affinity requirements. The pod is scheduled if such a node exists, it is moved to a terminated state otherwise. \\

You can read more about these policies [here](https://kubernetes.io/docs/tasks/administer-cluster/topology-manager/#topology-manager-policies).

`"reservedCPUs"` is a list of CPUs reserved for general purpose system use. Kubelet will not schedule pods to run on these CPUs.


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