Why is CPU usage high?
High CPU usage usually means one of a few things: a hot process, disk bottlenecks, memory pressure, lock contention, or runaway loops.
Common symptoms
- Server feels slow or unresponsive
- Fans ramp up or thermal throttling starts
- Latency spikes under load
Likely causes
- A single process is dominating CPU
- Disk contention is backing up worker threads
- Memory pressure is causing swap activity
- Too many threads or context switching overhead
Evidence to look for
CPU stays above 80% for more than 60 seconds
One process accounts for more than 40% CPU
iowait rises above normal baseline
What it usually means
High CPU is a symptom, not always the root cause. You need to distinguish true CPU-bound work from waiting on disk, memory, or scheduling.
What to do next
- 1Identify the top process by CPU and profile it
- 2Check iowait, disk utilization, and swap activity
- 3Reduce concurrency if context switching is excessive
See what's causing your CPU
cpum.ai turns CPU, process, disk, and memory signals into plain-English explanations with evidence.
Open cpum.ai