High CPU Usage by kswapd on RHEL 9

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

System shows persistent high CPU due to kswapd activity and memory reclaim churn.

Environment & Reproduction

Load average rises, application latency increases, and vmstat indicates heavy paging.

Root Cause Analysis

Insufficient RAM for workload, oversized cache footprint, memory leaks, or aggressive overcommit.

Quick Triage

Collect free -m, vmstat 1, top, and pressure stall information from /proc/pressure/memory.

Step-by-Step Diagnosis

Identify top memory consumers and reduce footprint via service tuning or scaling.

Solution – Primary Fix

Adjust vm.swappiness and related kernel parameters conservatively, then monitor impact.

Solution – Alternative Approaches

Use systemd limits and cgroup controls to isolate noisy workloads.

Verification & Acceptance Criteria

SELinux is usually not causal here; focus on memory profile and kernel reclaim behavior.

Rollback Plan

Confirm sustained drop in kswapd CPU and reduced paging under normal traffic.

Prevention & Hardening

Revert sysctl changes if they degrade stability or increase OOM risk.

Related Errors & Cross-Refs

Track memory trends and plan capacity before sustained reclaim pressure appears.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

vmstat 1; free -m; journalctl -k -b –no-pager