Ubuntu 20.04 Severe Slowdowns From Swap Thrashing

📖 ~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 extremely slow due to constant swap in/out activity.

Environment & Reproduction

High disk IO wait, lagging apps, and delayed terminal response.

Root Cause Analysis

Ubuntu 20.04 devices with low RAM under heavy multitasking workloads.

Quick Triage

Memory pressure exceeds physical RAM and default swappiness worsens latency.

Step-by-Step Diagnosis

Use vmstat, free -h, and top to identify sustained paging activity.

Solution – Primary Fix

Reduce memory-heavy services, tune vm.swappiness, and add RAM or zram where appropriate.

Solution – Alternative Approaches

Interactive performance improves and swap usage stabilizes during normal load.

Verification & Acceptance Criteria

Set workload limits, monitor memory trends, and capacity plan proactively.

Rollback Plan

Escalate when kernel OOM kills persist despite tuning and cleanup.

Prevention & Hardening

Revert sysctl tuning and disable experimental memory features if unstable.

Related Errors & Cross-Refs

Linux VM tuning docs and Ubuntu performance troubleshooting guides.

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

View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Lower swappiness can reduce desktop lag but is not a substitute for adequate RAM.