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Date: Tue, 23 Aug 2016 10:26:04 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
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Subject: Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps
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On Mon 22-08-16 19:47:09, Michal Hocko wrote:
> On Mon 22-08-16 19:29:36, Michal Hocko wrote:
> > On Mon 22-08-16 18:45:54, Michal Hocko wrote:
> > [...]
> > > I have no idea why those numbers are so different on my laptop
> > > yet. It surely looks suspicious. I will try to debug this further
> > > tomorrow.
> > 
> > Hmm, so I've tried to use my version of awk on other machine and vice
> > versa and it didn't make any difference. So this is independent on the
> > awk version it seems. So I've tried to strace /usr/bin/time and
> > wait4(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, {ru_utime={0, 0}, ru_stime={0, 688438}, ...}) = 9128
> > 
> > so the kernel indeed reports 0 user time for some reason. Note I
> > was testing with 4.7 and right now with 4.8.0-rc3 kernel (no local
> > modifications). The other machine which reports non-0 utime is 3.12
> > SLES kernel. Maybe I am hitting some accounting bug. At first I was
> > suspecting CONFIG_NO_HZ_FULL because that is the main difference between
> > my and the other machine but then I've noticed that the tests I was
> > doing in kvm have this disabled too.. so it must be something else.
> 
> 4.5 reports non-0 while 4.6 zero utime. NO_HZ configuration is the same
> in both kernels.

and one more thing. It is not like utime accounting would be completely
broken and always report 0. Other commands report non-0 values even on
4.6 kernels. I will try to bisect this down later today.
-- 
Michal Hocko
SUSE Labs