Re: Determining real-time CPU usage of a process

On 14-08-21, Jeremie Courreges-Anglas wrote:
> On Sat, Aug 14 2021, Baptiste Jonglez <baptiste@bitsofnetworks.org> wrote:
> > Hello,
>
> Hi Baptiste, long time no see. :)

Hi jca, indeed, good to talk to you :) Sorry for the late reply.

> > I would like to determine the CPU usage of a process on a "real-time"
> > basis. That is, every few seconds (sampling period), I would like to
> > compute its average CPU usage in the previous period.
>
> Looks like a job for getrusage(2) or the CLOCK_PROCESS_CPUTIME_ID clock
> supported by clock_gettime(2).

Thanks for the pointer.

It seems getrusage() and clock_gettime() apply only to the current
process, while I'm more interested in other processes, like top. That is,
I think the right interface to use is kvm_getprocs().

Besides, getrusage() seems to also use p_{u,s,i}ticks, so it would
probably also suffer from the delayed updates of these fields; that being
said, I haven't tested.

Regards,
Baptiste