Problem

On RHEL 8 systems, it is possible to observe high or fully utilized swap space even when a significant amount of physical memory remains free. This behavior occurs because the Linux kernel may proactively move inactive or rarely used memory pages to swap. The intention is to keep RAM available for active processes and file system caching, which can enhance overall system responsiveness.

This behavior typically does not result in performance issues. However, the ST JVM may experience latency or performance degradation if it frequently accesses memory pages that have been swapped out.

Resolution

Red Hat has provided updates to address scenarios where swap was used more aggressively than expected under cgroup v2. The recommended solution is to apply the latest kernel update and enable the parameter:

vm.swappiness=1
vm.force_cgroup_v2_swappiness=1

This setting helps ensure more predictable and conservative swapping behavior for cgroup-managed workloads.

More details about the fix and its background can be found in the corresponding RHEL Knowledgebase article.