Direct answer

Swap is slower backing storage for memory pages. The important signal is ongoing swapping or memory pressure during server activity—not merely a nonzero swap-used number.

How to check it

  1. Check free -h, swapon --show and vmstat 1 5; inspect sustained si and so rates.
  2. Check whether background backups, multiple Java processes, or other services are competing for physical RAM.
  3. Compare JVM heap allocation and any cgroup memory limit with actual host available memory.

What to change

free -h
swapon --show
vmstat 1 5
  1. Reduce competing workloads or lower an oversized Java heap only after checking GC and normal workload headroom.
  2. If host memory is genuinely insufficient, add RAM or move the workload; do not treat swap as a substitute for enough physical memory.
  3. Do not disable swap blindly on a machine at risk of OOM kills.

Software and version notes

Compatibility and safety

Linux free shows memory accounting, not only memory the process owns. Some managed hosts prohibit viewing swap or place the server in a container with its own limits.

Verify the result

During equivalent peak load, sustained swap-in/swap-out should decrease and MSPT spikes should become less frequent.

References