From mboxrd@z Thu Jan  1 00:00:00 1970
From: Glauber Costa <glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
Subject: Re: [PATCH v4 cgroup/for-3.7] cgroup: mark subsystems with broken
	hierarchy support and whine if cgroups are nested for them
Date: Fri, 14 Sep 2012 13:17:14 +0400
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Neil Horman <nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, "Aneesh Kumar K.V" <aneesh.kumar-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Arnaldo Carvalho de Melo <acme-f8uhVLnGfZaxAyOMLChx1axOck334EZe@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Thomas Graf <tgraf-G/eBtMaohhA@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On 09/14/2012 01:14 PM, Glauber Costa wrote:
> On 09/14/2012 12:03 AM, Tejun Heo wrote:
>> Hello, Vivek.
>>
>> On Thu, Sep 13, 2012 at 03:41:11PM -0400, Vivek Goyal wrote:
>>> I think for blkio controller, first level of creation itself is wrong if
>>> hierarchy is not supported. 
>>>
>>> 				root
>>> 			       / | \ 
>>>                               T1 T2 G1
>>>
> 
> I side with Vivek, and I think we should warn first level. It just tends
> to be wrong. If memcg is a special case, just special case it.
> _but_, I see no reason not to do it.
> 
> While I agree with Michal point that this is not necessary, I don't
> think being noisier than we need to be is a crime. Less noisy certainly
> can be.
> 

To add to that: If it is "all the same", hierarchy should be set to 1.
If anything else, this will make people switch it to shut up the
warning, and prevent a potentially broken use case to appear in the future.