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Date: Wed, 5 Sep 2012 13:12:38 -0700
From: Tejun Heo <tj@kernel.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: Glauber Costa <glommer@parallels.com>, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, linux-mm@kvack.org,
        Dave Jones <davej@redhat.com>, Ben Hutchings <ben@decadent.org.uk>,
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        Lennart Poettering <lennart@poettering.net>,
        Kay Sievers <kay.sievers@vrfy.org>,
        Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH v2] memcg: first step towards hierarchical controller
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Hello, Michal.

On Wed, Sep 05, 2012 at 04:49:42PM +0200, Michal Hocko wrote:
> Can we settle on the following 3 steps?
> 1) warn about "flat" hierarchies (give it X releases) - I will push it
>    to as many Suse code streams as possible (hope other distributions
>    could do the same)

I think I'm just gonna trigger WARN from cgroup core if anyone tries
to create hierarchy with a controller which doesn't support full
hierarchy.  WARN_ON_ONCE() at first and then WARN_ON() on each
creation later on.

> 2) flip the default on the root cgroup & warn when somebody tries to
>    change it to 0 (give it another X releases) that the knob will be
>    removed
> 3) remove the knob and the whole nonsese
> 4) revert 3 if somebody really objects

If we can get to 3, I don't think 4 would be a problem.

Thanks.

-- 
tejun