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Date: Tue, 13 Sep 2016 09:12:08 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Sonny Rao <sonnyrao@chromium.org>
Cc: Robert Foss <robert.foss@collabora.com>,
        Jonathan Corbet <corbet@lwn.net>,
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        Jacek Anaszewski <j.anaszewski@samsung.com>
Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
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On Mon 12-09-16 10:28:53, Sonny Rao wrote:
> On Mon, Sep 12, 2016 at 10:15 AM, Michal Hocko <mhocko@kernel.org> wrote:
> > On Mon 12-09-16 08:31:36, Sonny Rao wrote:
[...]
> >> but how about the other fields like Swap, Private_Dirty and
> >> Private_Shared?
> >
> > Private_Shared can be pretty confusing as well without the whole context
> > as well see my other emails in the original thread (just to remind
> > shmem/tmpfs makes all this really confusing).
> 
> But this is exactly the issue -- RSS is can be just as confusing if
> you don't know something about the application.

I agree that rss can be confusing but we will not make the situation any
better if we add yet another confusing metric.

> I think the issue is
> how common that situation is, and you seem to believe that it's so
> uncommon that it's actually better to keep the information more
> difficult to get for those of us who know something about our systems.
> 
> That's fine, I guess we just have to disagree here, thanks for look at this.

I think you should just step back and think more about what exactly
you expect from the counter(s). I believe what you want is an
estimate of a freeable memory when the particular process dies or is
killed. That would mean resident single mapped private anonymous memory
+ unlinked single mapped shareable mappings + single mapped swapped out
memory. Maybe I've missed something but it should be something along
those lines. Definitely something that the current smaps infrastructure
doesn't give you, though.
-- 
Michal Hocko
SUSE Labs

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
Date: Tue, 13 Sep 2016 09:12:08 +0200
Message-ID: <20160913071208.GC31898@dhcp22.suse.cz>
References: <1473106449-12847-1-git-send-email-robert.foss@collabora.com>
 <20160912120248.GK14524@dhcp22.suse.cz>
 <CAPz6YkVRcCkwv7WvdTQMH-UHhLK_k51QtNNOmNw7ySk7pfgD8w@mail.gmail.com>
 <20160912171503.GB14997@dhcp22.suse.cz>
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To: Sonny Rao <sonnyrao@chromium.org>
Cc: Robert Foss <robert.foss@collabora.com>, Jonathan Corbet <corbet@lwn.net>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Hugh Dickins <hughd@google.com>, Konstantin Khlebnikov <koct9i@gmail.com>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, John Stultz <john.stultz@linaro.org>, Minchan Kim <minchan@kernel.org>, ross.zwisler@linux.intel.com, jmarchan@redhat.com, Johannes Weiner <hannes@cmpxchg.org>, Kees Cook <keescook@chromium.org>, oleg@redhat.com, Al Viro <viro@zeniv.linux.org.uk>, Mateusz Guzik <mguzik@redhat.com>, Janis Danisevskis <jdanis@google.com>, calvinowens@fb.com, Alexey Dobriyan <adobriyan@gmail.com>, ebiederm@xmission.com, seth.forshee@canonical.com, tixxdz@g
List-Id: linux-api@vger.kernel.org

On Mon 12-09-16 10:28:53, Sonny Rao wrote:
> On Mon, Sep 12, 2016 at 10:15 AM, Michal Hocko <mhocko@kernel.org> wrote:
> > On Mon 12-09-16 08:31:36, Sonny Rao wrote:
[...]
> >> but how about the other fields like Swap, Private_Dirty and
> >> Private_Shared?
> >
> > Private_Shared can be pretty confusing as well without the whole context
> > as well see my other emails in the original thread (just to remind
> > shmem/tmpfs makes all this really confusing).
> 
> But this is exactly the issue -- RSS is can be just as confusing if
> you don't know something about the application.

I agree that rss can be confusing but we will not make the situation any
better if we add yet another confusing metric.

> I think the issue is
> how common that situation is, and you seem to believe that it's so
> uncommon that it's actually better to keep the information more
> difficult to get for those of us who know something about our systems.
> 
> That's fine, I guess we just have to disagree here, thanks for look at this.

I think you should just step back and think more about what exactly
you expect from the counter(s). I believe what you want is an
estimate of a freeable memory when the particular process dies or is
killed. That would mean resident single mapped private anonymous memory
+ unlinked single mapped shareable mappings + single mapped swapped out
memory. Maybe I've missed something but it should be something along
those lines. Definitely something that the current smaps infrastructure
doesn't give you, though.
-- 
Michal Hocko
SUSE Labs