IBM AIX 7.3 – Common Problem 014 – Diagnosis and Fix

📖 ~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

topas shows a single thread pinning one logical CPU at 100% sustained.

Environment & Reproduction

IBM AIX 7.3 LPAR exhibiting performance / topas hot CPU issues under standard PowerVM workloads.

topas -P
ps -mo THREAD -p 

Root Cause Analysis

Application bug or spin lock causes a single thread to monopolise an SMT thread.

Quick Triage

Confirm scope with errpt, recent changes, and subsystem state via lssrc.

ps -eo pid,thcount,pcpu | sort -rk3 | head

Step-by-Step Diagnosis

Use procstack and tprof to capture thread-level profile.

procstack 
tprof -x sleep 30

Solution – Primary Fix

Restart the offending process after capturing diagnostic data.

kill -USR1 
stopsrc -s appsubsys && startsrc -s appsubsys

Solution – Alternative Approaches

Bind the process to a CPU set with bindprocessor to contain impact.

Verification & Acceptance Criteria

Confirm subsystem returns to RUNNING state and errpt shows no new entries.

topas -P
lparstat 1 3

Rollback Plan

Restore prior configuration from mksysb or alt_disk_install clone if the fix regresses.

bindprocessor -u 

Prevention & Hardening

Encode the fix in NIM customisation scripts and monitor via topas/nmon.

smtctl -t 4  # right-size SMT

Related Errors & Cross-Refs

errpt LABEL=SCHED_HOG; runaway threads

Related tutorial: View the step-by-step tutorial for aix-7.3.

View all aix-7.3 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

AIX tprof and curt performance tools