From mboxrd@z Thu Jan  1 00:00:00 1970
From: Waiman Long <longman@redhat.com>
Subject: Re: [RFC PATCH 1/8] memcg: Enable fine-grained control of over
 memory.high action
Date: Tue, 18 Aug 2020 15:12:22 -0400
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To: Chris Down <chris@chrisdown.name>, 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>

On 8/17/20 12:56 PM, Chris Down wrote:
> Shakeel Butt writes:
>>> 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?
>
> Oh, thanks Shakeel for bringing this up. I missed this in the original 
> changelog and I'm surprised that it's mentioned, since we do have 
> protections against that.
>
> Waiman, we already added artificial throttling if memory reclaim is 
> not sufficiently achieved in 0e4b01df8659 ("mm, memcg: throttle 
> allocators when failing reclaim over memory.high"), which has been 
> present since v5.4. This should significantly inhibit physical memory 
> consumption from increasing. What problems are you having with that? :-)
>
Oh, I think I overlooked your patch. You are right. There are already 
throttling in place. So I need to re-examine my patch to see if it is 
still necessary or reduce the scope of the patch.

Thanks,
Longman