Understanding CPU usage

Roken · 2020-09-25 10:25:21

This may sound trivial, and perhaps I should know after many years of using Linux, but I'm stumped.

I have a conky, part of which includes the top four tasks in terms of CPU usage. The data from this is from an external script, which uses top. Conky typically reports more than 20% CPU usage.

nmon reports CPU usage total at around 4%.

Does top report a percentage of the total CPU, or a percentage of total CPU utilisation at the time (i.e. 20% CPU usage, or 20% of 4% = 0.8% of total)?

If the former, why are they so out of whack with each other?

solskog · 2020-09-25 11:51:08

I think top report 0.25% and that is 0.0025 out of 1.

seth · 2020-09-25 12:33:45

a) depend on the top invocation and it's probably more about how several cores are handled (run top and press "1") - the number in the cpu column is per core, not per CPU
b) Heisenberg problem? Depending on how top is involved (and what other stuff conky runs at the time) it itself could be the cause for the high(er) load

Trilby · 2020-09-25 13:35:55

seth wrote:

[top] itself could be the cause for the high(er) load

This.

I've often figured that "top" got it's name from the position of it's own listing it it's output when sorted by CPU use.

seth · 2020-09-25 14:04:09

To be sure: this script is so fancy that "${top name 1}${top name 2}${top name 3}${top name 4}" won't cut it?

@Trilby, try bashtop - überfancy, but makes top look anorexic ;-)

Arch Linux

#1 2020-09-25 10:25:21

Understanding CPU usage

#2 2020-09-25 11:51:08

Re: Understanding CPU usage

#3 2020-09-25 12:33:45

Re: Understanding CPU usage

#4 2020-09-25 13:35:55

Re: Understanding CPU usage

#5 2020-09-25 14:04:09

Re: Understanding CPU usage

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