Interpreting the three numbers.
WHAT IT MEASURES
The average number of processes running or waiting, over one, five and fifteen minutes.
WHAT IT DOES NOT MEASURE
Processor percentage.
WHY THAT DISTINCTION MATTERS
A machine can show high load with idle processors, if processes are waiting on disk.
WHAT TO COMPARE IT AGAINST
The number of processor cores.
WHAT EQUAL TO THE CORE COUNT MEANS
Fully occupied, with nothing queuing.
WHAT ABOVE IT MEANS
Work is waiting.
HOW TO COUNT CORES
Read the processor information file, or use nproc.
WHAT THE THREE FIGURES TOGETHER TELL YOU
- Rising: the problem is current and growing
- Falling: the peak has passed
- Flat and high: sustained pressure
WHY THE ONE-MINUTE FIGURE ALONE MISLEADS
A brief spike from a backup looks identical to a developing problem.
WHAT TO DO ON SEEING HIGH LOAD
Check the direction before acting.
WHAT TO TREAT AS ROUTINE
Short spikes with a known cause.
WHAT TO INVESTIGATE
Sustained elevation, or a rising trend.
WHAT TO RECORD
What normal looks like at different times of day.
WHY
Without a baseline, every reading is meaningless.
