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Date: Mon, 12 Mar 2012 15:28:17 -0700
From: Tejun Heo <tj@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>, containers@lists.linux-foundation.org,
        cgroups@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
        Kay Sievers <kay.sievers@vrfy.org>,
        Lennart Poettering <lennart@poettering.net>,
        Frederic Weisbecker <fweisbec@gmail.com>, linux-kernel@vger.kernel.org,
        Vivek Goyal <vgoyal@redhat.com>, Michal Schmidt <mschmidt@redhat.com>
Subject: Re: [RFD] cgroup: about multiple hierarchies
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Hey,

On Mon, Mar 12, 2012 at 11:22:18PM +0100, Peter Zijlstra wrote:
> On Mon, 2012-03-12 at 15:10 -0700, Tejun Heo wrote:
> > 
> > * How to map controllers which aren't aware of full hierarchy is still
> >   an open question but I'm still standing by one active node on any
> >   root-to-leaf path w/ root group serving as the special rest group. 
> 
> What does this mean?

Let's say we have a tree like the following.

         root
      /   |   \
     G1  G2   G3
             /  \
	   G31  G32

So, for cgroups which don't support full hierarchy, it'll be viewed as
either,

         root
      /   |   \
     G1  G2   G3

or

          root
      /   |   |  \
     G1  G2  G31 G32

With root being treated specially, probably as just being a equal
group as other groups, I'm not fully determined about that yet.

Thanks.

-- 
tejun