linux-kernel - Re: [PATCH] mm/memcontrol: add per-memcg pgpgin/pswpin counter

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Message-ID: <idy4zi4d5xk2sk7qxczmkdnxw35bohr6o5exj6oeee4lipm3dk@pbw35acxapov>
Date: Fri, 13 Sep 2024 09:58:26 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: jingxiang zeng <jingxiangzeng.cas@...il.com>
Cc: Jingxiang Zeng <linuszeng@...cent.com>, linux-mm@...ck.org, 
	Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Muchun Song <muchun.song@...ux.dev>, 
	Andrew Morton <akpm@...ux-foundation.org>, cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memcontrol: add per-memcg pgpgin/pswpin counter

On Fri, Sep 13, 2024 at 04:05:51PM GMT, jingxiang zeng wrote:
> On Tue, 10 Sept 2024 at 15:10, Shakeel Butt <shakeel.butt@...ux.dev> wrote:
> >
> > On Fri, Aug 30, 2024 at 04:22:44PM GMT, Jingxiang Zeng wrote:
> > > From: Jingxiang Zeng <linuszeng@...cent.com>
> > >
> > > In proactive memory reclamation scenarios, it is necessary to
> > > estimate the pswpin and pswpout metrics of the cgroup to
> > > determine whether to continue reclaiming anonymous pages in
> > > the current batch. This patch will collect these metrics and
> > > expose them.
> >
> > Please explain a bit more on how these metrics will be used to make
> > a decision to continue to do proactive reclaim or not.
> 
> Currently there is simply no way to know exactly how many anon page
> was faulted in through SWAP for each cgroup. One may use
> workingset refault as an indicator but it is inaccurate due to shadow reclaim.
> 
> We have a proactive reclaim agent that sets a forced swappiness
> dynamically for each reclaim, so we can reclaim file or anon pages striclty.
> Knowing the anon page swapin status is a huge win for estimating the
> workload status.
> 
> And the swapout info is also important for getting an idea of how much
> swapout is effective for a cgroup.
> 

Please add all these details on your proactive reclaim agent in the
commit message. It would be beneficial to others doing proactive
reclaim.