CPU Load Average Explained

LinuxPerformanceTroubleshooting

Interview Question

What do the 1, 5, and 15 minute load averages indicate on Linux, and how do you interpret them relative to CPU cores?

Key Points to Cover

Load average = runnable + uninterruptible tasks
Compare load to number of CPU cores (e.g., load 8 on 8 cores ≈ full utilization)
Trends (1/5/15) show short vs long-term pressure

Evaluation Rubric

Defines load average correctly34% weight

Relates load to core count33% weight

Explains 1/5/15 significance33% weight

Hints

Common Pitfalls to Avoid

⚠️Confusing load average solely with CPU utilization, neglecting the 'uninterruptible' task component (e.g., I/O wait).
⚠️Failing to consider the number of CPU cores when interpreting the load average, leading to misdiagnosis of system health.
⚠️Ignoring the trend across the 1, 5, and 15 minute values, thus missing whether the load is spiking, decreasing, or sustained.
⚠️Misinterpreting a high load average as always 'bad' without understanding the nature of the workload (e.g., intentional heavy batch processing).
⚠️Not understanding that high load average can be caused by I/O bottlenecks, not just CPU contention.

Potential Follow-up Questions