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Date:   Thu, 13 Feb 2020 17:36:36 +0100
From:   Michal Hocko <mhocko@kernel.org>
To:     Tejun Heo <tj@kernel.org>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>, linux-mm@kvack.org,
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Subject: Re: [PATCH v2 3/3] mm: memcontrol: recursive memory.low protection
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On Thu 13-02-20 10:52:49, Tejun Heo wrote:
> Hello,
> 
> On Thu, Feb 13, 2020 at 04:47:31PM +0100, Michal Hocko wrote:
> > Well, I would tend to agree but I can see an existing cgroup hierarchy
> > imposed by systemd and that is more about "logical" organization of
> > processes based on their purpose than anything resembling resources.
> > So what can we do about that to make it all work?
> 
> systemd right now isn't configuring any resource control by default,
> so I'm not sure why it is relevant in this discussion.

AFAIK systemd already offers knobs to configure resource controls [1].
Besides that we are talking about memcg features which are available only
unified hieararchy and that is what systemd is using already.

> You gotta
> change the layout to configure resource control no matter what and
> it's pretty easy to do. systemd folks are planning to integrate higher
> level resource control features, so my expectation is that the default
> layout is gonna change as it develops.

Do you have any pointers to those discussions? I am not really following
systemd development.

Anyway, I am skeptical that systemd can do anything much more clever
than placing cgroups with a resource control under the root cgroup. At
least not without some tagging which workloads are somehow related.

That being said, I do not really blame systemd here. We are not making
their life particularly easy TBH.

[1] https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html
-- 
Michal Hocko
SUSE Labs