What is a Load Average in Linux and how do you interpret it?
Load average in top or uptime shows three numbers: 1-minute, 5-minute, and 15-minute averages of the number of processes in a runnable or uninterruptible state.
Interpretation depends on the number of CPU cores. On a 4-core server:
- Load average of 4.0 = 100% utilization — every CPU busy but nothing waiting
- Load average of 8.0 = 200% utilization — 4 CPUs busy, 4 processes waiting in queue
- Load average of 0.5 = 12.5% utilization — plenty of headroom
Key insight: High load average is NOT always CPU. Uninterruptible sleep (disk I/O wait) also counts. Check iostat to distinguish CPU saturation from I/O saturation.