Re: [PATCH] mm: memcg: export workingset refault stats for cgroup v1

[Shakeel Butt]

On Tue, Aug 16, 2022 at 7:01 PM Yang Shi <shy828301@xxxxxxxxx> wrote:
>
> On Tue, Aug 16, 2022 at 3:06 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote:
> >
> > On Tue, Aug 16, 2022 at 11:58 AM Yang Shi <shy828301@xxxxxxxxx> wrote:
> > >
> > > Workingset refault stats are important and usefule metrics to measure
> > > how well reclaimer and swapping work and how healthy the services are,
> > > but they are just available for cgroup v2.  There are still plenty users
> > > with cgroup v1, export the stats for cgroup v1.
> > >
> > > Signed-off-by: Yang Shi <shy828301@xxxxxxxxx>
> > > ---
> > > I do understand the development of cgroup v1 is actually stalled and
> > > the community is reluctant to accept new features for v1.  However
> > > the workingset refault stats are really quite useful and exporting
> > > two new stats, which have been supported by v2, seems ok IMHO.  So
> > > hopefully this patch could be considered.  Thanks.
> > >
> >
> > Is just workingset refault good enough for your use-case? What about
> > the other workingset stats? I don't have a strong opinion against
> > adding these to v1 and I think these specific stats should be fine.
>
> The workingset refault is good enough for our usercase, but I don't
> mind adding all the workingset_* stats if nobody has objection.

For now let's just start with what your use-case needs. If in future
there is a need we can add other workingset_* stats as well.

>
> > (There is subtlety in exposing objcg based stats (i.e. reparenting) in
> > v1 due to non-hierarchical stats in v1. I remember Yosry and Muchun
> > were looking into that.)
>
> The workingset_* stats should have nothing to do with obj based stats IIUC.

Yeah, that was just FYI for anyone in future who wants to export such
stat in v1.