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Subject: Re: [RFC PATCH 1/8] memcg: Enable fine-grained control of over
 memory.high action
To:     Shakeel Butt <shakeelb@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-doc@vger.kernel.org,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Cgroups <cgroups@vger.kernel.org>, Linux MM <linux-mm@kvack.org>
References: <20200817140831.30260-1-longman@redhat.com>
 <20200817140831.30260-2-longman@redhat.com>
 <CALvZod5V3N3K9-tDoaq=JgkeuAK=0TkRf97Vua0khXL+Lxw+Pg@mail.gmail.com>
From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
Message-ID: <89179081-697d-232d-a936-697e3c662f65@redhat.com>
Date:   Tue, 18 Aug 2020 15:14:06 -0400
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On 8/17/20 12:44 PM, Shakeel Butt wrote:
> On Mon, Aug 17, 2020 at 7:11 AM Waiman Long <longman@redhat.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