linux-kernel - Re: [PATCH v3] mm: memcg: Use larger batches for proactive reclaim

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Message-ID: <ZcFQMru5_oATGbuP@tiehlicka>
Date: Mon, 5 Feb 2024 22:16:34 +0100
From: Michal Hocko <mhocko@...e.com>
To: "T.J. Mercier" <tjmercier@...gle.com>
Cc: Johannes Weiner <hannes@...xchg.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Shakeel Butt <shakeelb@...gle.com>,
	Muchun Song <muchun.song@...ux.dev>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Efly Young <yangyifei03@...ishou.com>, android-mm@...gle.com,
	yuzhao@...gle.com, mkoutny@...e.com,
	Yosry Ahmed <yosryahmed@...gle.com>, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mm: memcg: Use larger batches for proactive reclaim

On Mon 05-02-24 12:47:47, T.J. Mercier wrote:
> On Mon, Feb 5, 2024 at 12:36 PM Michal Hocko <mhocko@...e.com> wrote:
[...]
> > This of something like
> > timeout $TIMEOUT echo $TARGET > $MEMCG_PATH/memory.reclaim
> > where timeout acts as a stop gap if the reclaim cannot finish in
> > TIMEOUT.
> 
> Yeah I get the desired behavior, but using sc->nr_reclaimed to achieve
> it is what's bothering me.

I am not really happy about this subtlety. If we have a better way then
let's do it. Better in its own patch, though.

> It's already wired up that way though, so if you want to make this
> change now then I can try to test for the difference using really
> large reclaim targets.

Yes, please. If you want it a separate patch then no objection from me
of course. If you do no like the nr_to_reclaim bailout then maybe we can
go with a simple break out flag in scan_control.

Thanks!
-- 
Michal Hocko
SUSE Labs