kernel space: finding cpu usage of individual process/thread

kernel space: finding cpu usage of individual process/thread

[Pintu Agarwal]

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

Re: kernel space: finding cpu usage of individual process/thread

[Greg KH]

On Wed, Mar 23, 2022 at 09:15:16PM +0530, Pintu Agarwal wrote:
> 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".

Who is making such a crazy requirement?

Have you looked at how normal tools get this information today?  We have
loads of userspace examples and libraries that provide you this
information, no need to reinvent the wheel.

Unless this is a homework assignment.  Then that's up to you to solve,
not us :)

good luck!

greg k-h