8.5.3.3. Understanding swap memory and QoS

Review the following information to learn how swap memory and QoS interact in an overcommitted environment to help you ensure that your cluster is properly configured.

You can disable swap by default on your nodes to preserve quality of service (QoS) guarantees. Otherwise, physical resources on a node can oversubscribe, affecting the resource guarantees the Kubernetes scheduler makes during pod placement.

For example, if two guaranteed pods have reached their memory limit, each container could start using swap memory. Eventually, if there is not enough swap space, processes in the pods can be terminated due to the system being oversubscribed.

Failing to disable swap causes nodes to not recognize that they are experiencing MemoryPressure, resulting in pods not receiving the memory they made in their scheduling request. As a result, additional pods are placed on the node to further increase memory pressure, ultimately increasing your risk of experiencing a system out of memory (OOM) event.