Ubuntu 20.04 LTS – high CPU from kswapd0 due to memory pressure

📖 ~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 becomes sluggish while kswapd consumes significant CPU continuously.

Environment & Reproduction

Triggered by low memory headroom, aggressive caching, or swap thrashing workloads.

Root Cause Analysis

Kernel reclaim loops under memory pressure and spends cycles scanning pages.

Quick Triage

Measure memory, swap, and top memory consumers during incident window.

Step-by-Step Diagnosis

Correlate vmstat, pressure metrics, and process memory growth.

Solution – Primary Fix

Reduce memory pressure, tune swappiness, and add RAM or swap capacity.

Solution – Alternative Approaches

Apply cgroup memory limits to noisy processes and rebalance workload placement.

Verification & Acceptance Criteria

kswapd CPU normalizes and latency returns to acceptable baseline.

Rollback Plan

Undo kernel VM tuning if application throughput drops unexpectedly.

Prevention & Hardening

Implement memory saturation alerts and capacity planning thresholds.

Related Errors & Cross-Refs

kswapd0 100 percent CPU, swapin spikes, and memory pressure stall warnings.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

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Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Linux memory reclaim behavior and Ubuntu performance tuning docs.