Kube-apiserver memory cleanup mechanism

Cluster information:

Kubernetes version: openshift 4.6.35 / kubernetes version 1.19
Cloud being used: openstack 13
Installation method: openshift IPI installation
Host OS: coreos

Hello everyone, I would like to ask about a strange memory behavior that we encountered in some of our clusters.

After a spike in the memory consumption of the api server, the ram remains in the same level of the top of the spike which means that the kube api server does not free any memory.

Is this behavior normal? Can you guide us to a document that describes the kube api server memory cleanup mechanism?