From mboxrd@z Thu Jan  1 00:00:00 1970
From: peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org
Subject: Re: [RFC PATCH 0/8] memcg: Enable fine-grained per process memory
 control
Date: Tue, 18 Aug 2020 11:59:10 +0200
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To: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
Cc: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>, Alexey Dobriyan <adobriyan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Vincent Guittot <vincent.guittot-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-doc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org

On Tue, Aug 18, 2020 at 11:26:17AM +0200, Michal Hocko wrote:
> On Tue 18-08-20 11:14:53, Peter Zijlstra wrote:
> > On Mon, Aug 17, 2020 at 10:08:23AM -0400, Waiman Long 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 v2 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. In this case,
> > > the physical memory consumption will keep on increasing. 
> > 
> > Then slow down the allocator? That's what we do for dirty pages too, we
> > slow down the dirtier when we run against the limits.
> 
> This is what we actually do. Have a look at mem_cgroup_handle_over_high.

But then how can it run-away like Waiman suggested?

/me goes look... and finds MEMCG_MAX_HIGH_DELAY_JIFFIES.

That's a fail... :-(