8.5. Configuring your cluster to place pods on overcommitted nodes

You can use resource requests in an overcommitted environment help you ensure that your cluster is properly configured.

For each compute resource, a container can specify a resource request and limit. Scheduling decisions are made based on the request to ensure that a node has enough capacity available to meet the requested value. If a container specifies limits, but omits requests, the requests are defaulted to the limits. A container is not able to exceed the specified limit on the node.

The enforcement of limits is dependent upon the compute resource type. If a container makes no request or limit, the container is scheduled to a node with no resource guarantees. In practice, the container is able to consume as much of the specified resource as is available with the lowest local priority. In low resource situations, containers that specify no resource requests are given the lowest quality of service.

Scheduling is based on resources requested, where quota and hard limits refer to resource limits, which can be set higher than requested resources. The difference between the request and the limit determines the level of overcommit. For example, if a container is given a memory request of 1Gi and a memory limit of 2Gi, the container is scheduled based on the 1Gi request being available on the node, but could use up to 2Gi; so it is 100% overcommitted.