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From: Sonny Rao <sonnyrao@chromium.org>
Date: Tue, 13 Sep 2016 13:27:39 -0700
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Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
To: Michal Hocko <mhocko@kernel.org>
Cc: Robert Foss <robert.foss@collabora.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
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On Tue, Sep 13, 2016 at 12:12 AM, Michal Hocko <mhocko@kernel.org> wrote:
> 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.

Yes your description of what we want is pretty good.  Having a
reasonable lower bound on the estimate is fine, though we probably
want to break out swapped out memory separately.  Given that smaps
doesn't provide this in a straightforward way, what do you think is
the right way to provide this information?

> --
> Michal Hocko
> SUSE Labs

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sonny Rao <sonnyrao@chromium.org>
Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
Date: Tue, 13 Sep 2016 13:27:39 -0700
Message-ID: <CAPz6YkXq_QPffYgBJZGxZG9SboTVoCEH2qqCgAuB6YYj1e95ig@mail.gmail.com>
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> <CAPz6YkVs5OjYY6bWzUh5sshrMRS+aFG9=F0ptLsmUb_RD3=pzg@mail.gmail.com>
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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 <seth.forshee@canonical>
List-Id: linux-api@vger.kernel.org

On Tue, Sep 13, 2016 at 12:12 AM, Michal Hocko <mhocko@kernel.org> wrote:
> 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.

Yes your description of what we want is pretty good.  Having a
reasonable lower bound on the estimate is fine, though we probably
want to break out swapped out memory separately.  Given that smaps
doesn't provide this in a straightforward way, what do you think is
the right way to provide this information?

> --
> Michal Hocko
> SUSE Labs