On 2016-09-14 05:12 AM, Michal Hocko wrote:
On Tue 13-09-16 13:27:39, Sonny Rao wrote:
On Tue, Sep 13, 2016 at 12:12 AM, Michal Hocko <mho...@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 <mho...@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 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.

Why would you want to separate that?

Given that smaps
doesn't provide this in a straightforward way, what do you think is
the right way to provide this information?

I would be tempted to sneak it into /proc/<pid>/statm because that looks
like a proper place but getting this information is not for free
performance wise so I am not really sure something that relies on this
file would see unexpected stalls. Maybe this could be worked around by
some caching... I would suggest to check who is actually using this file
(top/ps etc...)

What would this caching look like? Can any information be re-used between vma walks?

If this would be unacceptable then a new file could be considered.

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