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

From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Sonny Rao <sonnyrao@chromium.org>, Jann Horn <jann@thejh.net>,
	Robert Foss <robert.foss@collabora.com>,
	corbet@lwn.net, Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Konstantin Khlebnikov <koct9i@gmail.com>,
	Hugh Dickins <hughd@google.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	John Stultz <john.stultz@linaro.org>,
	ross.zwisler@linux.intel.com, jmarchan@redhat.com,
	Johannes Weiner <hannes@cmpxchg.org>,
	Kees Cook <keescook@chromium.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	Robin Humble <plaguedbypenguins@gmail.com>,
	David Rientjes <rientjes@google.com>,
	eric.engestrom@imgtec.com, Janis Danisevskis <jdanis@google.com>,
	calvinowens@fb.com, Alexey Dobriyan <adobriyan@gmail.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	ldufour@linux.vnet.ibm.com, linux-doc@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ben Zhang <benzh@chromium.org>, Bryan Freed <bfreed@chromium.org>,
	Filipe Brandenburger <filbranden@chromium.org>,
	Mateusz Guzik <mguzik@redhat.com>
Subject: Re: [PACTH v2 0/3] Implement /proc/<pid>/totmaps
Date: Tue, 23 Aug 2016 10:26:04 +0200	[thread overview]
Message-ID: <20160823082603.GI23577@dhcp22.suse.cz> (raw)
In-Reply-To: <20160822174709.GD7043@dhcp22.suse.cz>

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