linux-kernel - Re: [PATCH] memcg: provide reclaim stats via 'memory.reclaim'

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Message-ID: <CAJD7tkb7DRK_9wtiSFPiV6zsZGYYxs_JGECODtP+pta4k4MaiA@mail.gmail.com>
Date:   Wed, 25 May 2022 13:31:42 -0700
From:   Yosry Ahmed <yosryahmed@...gle.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>,
        Cgroups <cgroups@...r.kernel.org>, linux-doc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>, Tejun Heo <tj@...nel.org>,
        Zefan Li <lizefan.x@...edance.com>,
        Jonathan Corbet <corbet@....net>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH] memcg: provide reclaim stats via 'memory.reclaim'

On Wed, May 25, 2022 at 1:59 AM Michal Hocko <mhocko@...e.com> wrote:
>
> On Tue 24-05-22 12:01:01, Yosry Ahmed wrote:
> > On Tue, May 24, 2022 at 4:45 AM Johannes Weiner <hannes@...xchg.org> wrote:
> > >
> > > On Mon, May 23, 2022 at 03:50:34PM -0700, Yosry Ahmed wrote:
> > > > I think it might be useful to have a dedicated entry in memory.stat
> > > > for proactively reclaimed memory. A case where this would be useful is
> > > > tuning and evaluating userspace proactive reclaimers. For instance, if
> > > > a userspace agent is asking the kernel to reclaim 100M, but it could
> > > > only reclaim 10M, then most probably the proactive reclaimer is not
> > > > using a good methodology to figure out how much memory do we need to
> > > > reclaim.
> > > >
> > > > IMO this is more useful, and a superset of just reading the last
> > > > reclaim request status through memory.reclaim (read stat before and
> > > > after).
> > >
> > > +1
> >
> > It might also be useful to have a breakdown of this by memory type:
> > file, anon, or shrinkers.
> >
> > It would also fit in nicely with a potential type=file/anon/shrinker
> > argument to memory.reclaim. Thoughts on this?
>
> Can we start simple and see what real usecases actually will need?

Agreed. Let's start with a single proactively reclaimed memory stat
and then add subcategories if/when needed.

> --
> Michal Hocko
> SUSE Labs