Managing the maximum number of pods per node

Exceeding these values can result in:

Increased CPU utilization by OKD.
Slow pod scheduling.
Potential out-of-memory scenarios, depending on the amount of memory in the node.
Exhausting the IP address pool.
Resource overcommitting, leading to poor user application performance.

The parameter limits the number of pods the node can run based on the number of processor cores on the node. For example, if podsPerCore is set to 10 on a node with 4 processor cores, the maximum number of pods allowed on the node is 40.

Two parameters control the maximum number of pods that can be scheduled to a node: podsPerCore and maxPods. If you use both options, the lower of the two limits the number of pods on a node.

For example, if podsPerCore is set to 10 on a node with 4 processor cores, the maximum number of pods allowed on the node will be 40.

Prerequisites

Obtain the label associated with the static MachineConfigPool CRD for the type of node you want to configure. Perform one of the following steps:
1. View the machine config pool:
  
  For example:
```
$ oc describe machineconfigpool worker
```
  Example output
```
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfigPool
  creationTimestamp: 2019-02-08T14:52:39Z
  generation: 1
    custom-kubelet: small-pods (1)
```
2. If the label is not present, add a key/value pair:

Create a custom resource (CR) for your configuration change.

Sample configuration for a max-pods CR
```
apiVersion: machineconfiguration.openshift.io/v1
kind: KubeletConfig
metadata:
  name: set-max-pods (1)
spec:
    matchLabels:
      custom-kubelet: small-pods (2)
  kubeletConfig:
    podsPerCore: 10 (3)
    maxPods: 250 (4)
```
In the above example, the default value for podsPerCore is 10 and the default value for maxPods is 250. This means that unless the node has 25 cores or more, by default, podsPerCore will be the limiting factor.
List the MachineConfigPool CRDs to see if the change is applied. The UPDATING column reports True if the change is picked up by the Machine Config Controller:
```
$ oc get machineconfigpools
```
Example output

Once the change is complete, the UPDATED column reports True.
```
$ oc get machineconfigpools
```
Example output
```
NAME     CONFIG                        UPDATED   UPDATING   DEGRADED
worker   worker-8cecd1236b33ee3f8a5e   True      False      False
```

Managing the maximum number of Pods per Node

Managing the maximum number of pods per node