Messages in this thread | | | Subject | Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps | From | Robert Foss <> | Date | Mon, 19 Sep 2016 11:16:31 -0400 |
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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 <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. > > 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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