linux-kernel - Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps

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Date:   Mon, 22 Aug 2016 19:47:09 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Sonny Rao <sonnyrao@...omium.org>, Jann Horn <jann@...jh.net>,
        Robert Foss <robert.foss@...labora.com>, corbet@....net,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Hugh Dickins <hughd@...gle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        John Stultz <john.stultz@...aro.org>,
        ross.zwisler@...ux.intel.com, jmarchan@...hat.com,
        Johannes Weiner <hannes@...xchg.org>,
        Kees Cook <keescook@...omium.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Cyrill Gorcunov <gorcunov@...nvz.org>,
        Robin Humble <plaguedbypenguins@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        eric.engestrom@...tec.com, Janis Danisevskis <jdanis@...gle.com>,
        calvinowens@...com, Alexey Dobriyan <adobriyan@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        ldufour@...ux.vnet.ibm.com, linux-doc@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ben Zhang <benzh@...omium.org>,
        Bryan Freed <bfreed@...omium.org>,
        Filipe Brandenburger <filbranden@...omium.org>,
        Mateusz Guzik <mguzik@...hat.com>
Subject: Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps

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.
-- 
Michal Hocko
SUSE Labs