Step-by-Step Guide to Diagnose High CPU Usage on Linux

The article provides a practical checklist for diagnosing high CPU usage on a Linux system, detailing which commands to run and how to interpret their output.

1. Check CPU Usage

Use top or htop to view per‑process CPU consumption. If overall CPU usage exceeds 80 %, further investigation is warranted.

2. Check System Load

Run uptime to see the load averages. A load higher than twice the number of CPU cores generally indicates overload.

3. Inspect Resource Usage per Process

Identify resource‑hungry processes with pidstat -p <pid> 1, which prints CPU, memory, and other metrics for the specified PID every second.

4. Trace Problematic Processes

If a process shows excessive usage, use strace -p <pid> to monitor its system calls and return values, helping pinpoint the root cause.

5. Review System Logs

Examine recent entries in /var/log/messages and /var/log/syslog with tail -f /var/log/messages /var/log/syslog to catch errors or events related to the issue.

6. Identify Performance Bottlenecks

Utilize the perf tool, e.g., perf top, to see which functions consume the most CPU time in real time, revealing deeper performance bottlenecks.

By following these steps, administrators can systematically narrow down the cause of high CPU usage and apply appropriate remediation.