Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps

[Sonny Rao]

On Tue, Sep 13, 2016 at 12:12 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> On Mon 12-09-16 10:28:53, Sonny Rao wrote:
>> On Mon, Sep 12, 2016 at 10:15 AM, Michal Hocko <mhocko@xxxxxxxxxx> 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