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From:   Thommy Jakobsson <thommyj@gmail.com>
Date:   Fri, 22 Jun 2018 17:09:12 +0200
Message-ID: <CAOTQ16LL_W+RqDWQLzsvnRaYGT_9E9EMN_9hdr-vie8hp83gAA@mail.gmail.com>
Subject: BUG? DOC: Really jiffies in /proc/schedstat?
To:     linux-kernel@vger.kernel.org
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Hi,

I am measuring cpu runtime for a couple of processes, and is using
/proc/schedstat and /proc/[pid]/schedstat to do so. According to the
schedstat doc
(https://www.kernel.org/doc/Documentation/scheduler/sched-stats.txt) the last
three values are in jiffies. Doing something like

root@gvp4-base-pd-b-rev1:~#  cat /proc/schedstat  | grep cpu3; sleep
2; cat /proc/schedstat  | grep cpu3;
cpu3 0 0 0 0 0 0 41155818663320 17173365985560 1011370906
cpu3 0 0 0 0 0 0 41157858979020 17176095339120 1011430425

on a heavy loaded system seems to suggest that at least the sum of running tasks
is in nanoseconds, not jiffies. Which I also think looks correct when
checking the
code.

For /proc/[pid]/schedstat the documentation is a bit vague on unit,
but I interpret it
to be the same as the corresponding global values. Which would mean jiffies.
Also here it looks to be in nanoseconds on my system though.

Am I just confused? is it configuration/system dependent? or is the
doc just plain
wrong?

Thanks,
Thommy Jakobsson