CPU high due to disk
When disk is slow, threads waiting on IO pile up. This creates scheduling overhead and makes CPU charts spike — even though the system is not truly compute-bound.
Evidence to look for
Disk utilization above 80%
Disk await times above 20ms
iowait rises alongside CPU
What it usually means
The CPU is not doing useful compute. It is spending time context-switching between threads that are all waiting on disk.
What to do next
- 1Move to faster storage
- 2Reduce concurrent disk operations
- 3Add application-level caching to avoid unnecessary reads
See what's causing your CPU
cpum.ai turns CPU, process, disk, and memory signals into plain-English explanations with evidence.
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