linux-kernel - kernel space: finding cpu usage of individual process/thread

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Message-ID: <CAOuPNLhB8pojv4wqv6d4FvhoBbNvUxD19ciK-6E8HtbbrnjF9g@mail.gmail.com>
Date:   Wed, 23 Mar 2022 21:15:16 +0530
From:   Pintu Agarwal <pintu.ping@...il.com>
To:     open list <linux-kernel@...r.kernel.org>,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>,
        Johannes Weiner <hannes@...xchg.org>, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com
Subject: kernel space: finding cpu usage of individual process/thread

Hi,

For one of my requirements I need to find cpu usage or load_avg of an
individual process or thread using "for_each_process_thread(process,
thread)" where process/thread is a pointer to "task_struct".

But, currently I am not able to figure out which is the right field
from task_struct to get this value, or how to manipulate it.

I see some fields there but I'm not sure if these values are correct.
a) sched_entity -> sched_avg -> load/load_avg/load_sum/util_avg/etc.
b) stime + utime : What time I get from here ?
c) prev_cputime
d) vtime
e) acct_timexpd
f) ???

It will be good if I can get some references in kernel space.

When I use (a) above (load_avg) I get this value:
pid=2 , comm=kthread, load=51
pid=96, comm=cat , load=1024
etc...

When I use (stime + utime) I get:
pid=2 , comm=kthread, load=3978848
pid=96, comm=cat , load=11786176

So, not sure which one is correct ?

Thanks,
Pintu