linux-kernel - Re: [RFC PATCH 1/8] memcg: Enable fine-grained control of over memory.high action

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Message-ID: <89179081-697d-232d-a936-697e3c662f65@redhat.com>
Date:   Tue, 18 Aug 2020 15:14:06 -0400
From:   Waiman Long <longman@...hat.com>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Jonathan Corbet <corbet@....net>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-doc@...r.kernel.org,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Cgroups <cgroups@...r.kernel.org>, Linux MM <linux-mm@...ck.org>
Subject: Re: [RFC PATCH 1/8] memcg: Enable fine-grained control of over
 memory.high action

On 8/17/20 12:44 PM, Shakeel Butt wrote:
> On Mon, Aug 17, 2020 at 7:11 AM Waiman Long <longman@...hat.com> wrote:
>> Memory controller can be used to control and limit the amount of
>> physical memory used by a task. When a limit is set in "memory.high"
>> in a non-root memory cgroup, the memory controller will try to reclaim
>> memory if the limit has been exceeded. Normally, that will be enough
>> to keep the physical memory consumption of tasks in the memory cgroup
>> to be around or below the "memory.high" limit.
>>
>> Sometimes, memory reclaim may not be able to recover memory in a rate
>> that can catch up to the physical memory allocation rate especially
>> when rotating disks are used for swapping or writing dirty pages. In
>> this case, the physical memory consumption will keep on increasing.
> Isn't this the real underlying issue? Why not make the guarantees of
> memory.high more strict instead of adding more interfaces and
> complexity?
>
> By the way, have you observed this issue on real workloads or some
> test cases? It would be good to get a repro with simple test cases.
>
As said before, this is from a customer request. I will need to 
re-examine the existing features to see if they can satisfy the customer 
need.

Cheers,
Longman