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Date: Wed, 6 Sep 2017 18:40:43 +0100
From: Roman Gushchin <guro@fb.com>
Subject: Re: [v7 5/5] mm, oom: cgroup v2 mount option to disable cgroup-aware
 OOM killer
Message-ID: <20170906174043.GA12579@castle.DHCP.thefacebook.com>
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To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org, Vladimir Davydov <vdavydov.dev@gmail.com>, Johannes Weiner <hannes@cmpxchg.org>, Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>, David Rientjes <rientjes@google.com>, Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>, kernel-team@fb.com, cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org

sOn Wed, Sep 06, 2017 at 10:42:42AM +0200, Michal Hocko wrote:
> On Tue 05-09-17 20:16:09, Roman Gushchin wrote:
> > On Tue, Sep 05, 2017 at 05:12:51PM +0200, Michal Hocko wrote:
> [...]
> > > > Then we should probably hide corresponding
> > > > cgroup interface (oom_group and oom_priority knobs) by default,
> > > > and it feels as unnecessary complication and is overall against
> > > > cgroup v2 interface design.
> > > 
> > > Why. If we care enough, we could simply return EINVAL when those knobs
> > > are written while the corresponding strategy is not used.
> > 
> > It doesn't look as a nice default interface.
> 
> I do not have a strong opinion on this. A printk_once could explain why
> the knob is ignored and instruct the admin how to enable the feature
> completely.
>  
> > > > > I think we should instead go with
> > > > > oom_strategy=[alloc_task,biggest_task,cgroup]
> > > > 
> > > > It would be a really nice interface; although I've no idea how to implement it:
> > > > "alloc_task" is an existing sysctl, which we have to preserve;
> > > 
> > > I would argue that we should simply deprecate and later drop the sysctl.
> > > I _strongly_ suspect anybody is using this. If yes it is not that hard
> > > to change the kernel command like rather than select the sysctl.
> > 
> > I agree. And if so, why do we need a new interface for an useless feature?
> 
> Well, I won't be opposed just deprecating the sysfs and only add a
> "real" kill-allocate strategy if somebody explicitly asks for it.


I think we should select this approach.
Let's check that nobody actually uses it.

Thanks!

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