Question: what is the differences in cpuloads and which ones do we need to verify?
1. Show cpuload
This CLI uses a direct kernel interface to return a pre-calculated average of CPU usage across all the control plane CPUs. Kernel on every timer interrupt keeps such statistics which this CLI uses and displays.
It can be used to get a knowledge of system usage as a whole. In this we don’t try to demarcate what processes in what space (user or kernel) are taking up the CPU.
It just tells how much, system as a whole, is busy and where.
2. Show cpuload current
This CLI uses top2 command internal to display the stats.
top2 command works on sampling per CPU usage. Thus is need 1 or 2 consecution runs to come to an exact system load.
The CLI runs the command in single-shot mode and displayes the output. As a result of which, the 3rd line doesn’t give correct system usage. If you run top2 command from the shell prompt, without any options, you will see that first display shows incorrect usage in 3rd line. But in further displays it will converge and come to correct value.
This CLI should be used to check the exact per-process CPU utilisation. This also is instantaneous but it decouples per-CPU process scheduling and usage. Hence tells exact CPU usage each process is having in SMP systems.
3. Show processes sort-by cpu
This CLI uses the ps command to show the output.
The CPU utilization here should be at par with “show cpuload current”. But this command also works on instantaneous samplings. In case of momentary peak or a delay between runs of “show cpuload current” and this CLI.