CPU high because IO blocking
Blocking IO causes requests, workers, and threads to pile up. The result often looks like high CPU, but the root cause is stalled progress.
Common symptoms
- CPU high with poor throughput
- Latency rises under storage or network load
- Workers pile up without useful progress
Likely causes
- Disk blocking
- Network waits
- Synchronous IO in hot paths
Evidence to look for
IO metrics worsen during incidents
Processes wait on reads/writes
CPU remains high while work stalls
What it usually means
The system is paying the cost of queueing and contention around blocked IO.
What to do next
- 1Reduce synchronous blocking in hot paths
- 2Improve storage/network latency
- 3Separate compute-heavy and IO-heavy work
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cpum.ai turns CPU, process, disk, and memory signals into plain-English explanations with evidence.
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