From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH v2] memcg: first step towards hierarchical controller
Date: Wed, 5 Sep 2012 13:12:38 -0700
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To: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
Cc: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Ben Hutchings <ben-/+tVBieCtBitmTQ+vhA3Yw@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Lennart Poettering <lennart-mdGvqq1h2p+GdvJs77BJ7Q@public.gmane.org>, Kay Sievers <kay.sievers-tD+1rO4QERM@public.gmane.org>, Kamezawa Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>

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