linux-kernel - Re: [PATCH v4] mm/memcg: try harder to decrease [memory,memsw].limit_in

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Message-ID: <20180112122405.GK1732@dhcp22.suse.cz>
Date:   Fri, 12 Jan 2018 13:24:05 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH v4] mm/memcg: try harder to decrease
 [memory,memsw].limit_in_bytes

On Fri 12-01-18 00:59:38, Andrey Ryabinin wrote:
> On 01/11/2018 07:29 PM, Michal Hocko wrote:
[...]
> > I do not think so. Consider that this reclaim races with other
> > reclaimers. Now you are reclaiming a large chunk so you might end up
> > reclaiming more than necessary. SWAP_CLUSTER_MAX would reduce the over
> > reclaim to be negligible.
> > 
> 
> I did consider this. And I think, I already explained that sort of race in previous email.
> Whether "Task B" is really a task in cgroup or it's actually a bunch of reclaimers,
> doesn't matter. That doesn't change anything.

I would _really_ prefer two patches here. The first one removing the
hard coded reclaim count. That thing is just dubious at best. If you
_really_ think that the higher reclaim target is meaningfull then make
it a separate patch. I am not conviced but I will not nack it it either.
But it will make our life much easier if my over reclaim concern is
right and we will need to revert it. Conceptually those two changes are
independent anywa.

-- 
Michal Hocko
SUSE Labs