linux-kernel - Re: [PATCH] mm: per-cgroup memory reclaim stats

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Date:   Wed, 17 May 2017 16:50:42 +0100
From:   Roman Gushchin <guro@...com>
To:     Balbir Singh <bsingharora@...il.com>
CC:     Johannes Weiner <hannes@...xchg.org>, Tejun Heo <tj@...nel.org>,
        Li Zefan <lizefan@...wei.com>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH] mm: per-cgroup memory reclaim stats

On Wed, May 17, 2017 at 08:03:03AM +1000, Balbir Singh wrote:
> On Sat, May 13, 2017 at 2:42 AM, Johannes Weiner <hannes@...xchg.org> wrote:
> > On Fri, May 12, 2017 at 12:25:22PM +1000, Balbir Singh wrote:
> >>
> >> It sounds like memcg accumlates both global and memcg reclaim driver
> >> counts -- is this what we want?
> >
> > Yes.
> >
> > Consider a fully containerized system that is using only memory.low
> > and thus exclusively global reclaim to enforce the partitioning, NOT
> > artificial limits and limit reclaim. In this case, we still want to
> > know how much reclaim activity each group is experiencing.
> 
> But its also confusing to see memcg.stat's value being greater
> than the global value? At-least for me. For example PGSTEAL_DIRECT
> inside a memcg > global value of PGSTEAL_DIRECT. Do we make
> memcg.stat values sum of all impact on memcg or local to memcg?

Yes, I think that global counters should include both results of
global and per-cgroup reclaim. I will prepare a separate patch for this.

Thank you!

Roman