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

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Message-ID: <7d1b5bfb-f602-8cf4-2de6-dd186484e55c@virtuozzo.com>
Date:   Mon, 15 Jan 2018 15:30:59 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Michal Hocko <mhocko@...nel.org>
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 01/12/2018 03:24 PM, Michal Hocko wrote:
> 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.
> 

Ok, fair point. But what about livelock than? Don't you think that we should
go back to something like in V1 patch to prevent it?