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Date: Wed, 1 Dec 2010 13:01:29 +0800
From: =?utf-8?Q?Am=C3=A9rico?= Wang <xiyou.wangcong@gmail.com>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>, Paul Turner <pjt@google.com>,
        Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4] sched: automated per session task groups
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On Tue, Nov 30, 2010 at 02:36:22PM -0500, Vivek Goyal wrote:
>
>So again, user will think that task is in cgroup test1 and is being
>controlled by the respective weight but that's not the case.
>
>Even if we prevent autogroup task from being visible in cpu controller
>root group, then comes the question what happens if cpu and some other
>controller is comounted. Say cpuset. Now in that case will task be 
>visible in root group task file and can one operate on that. Now showing
>up there does not make much sense as task should still be controllable
>by other controllers and its policies.
>
>So yes, creating a /proc/<pid>/autogroup is dirt cheap and makes the life
>easier in terms of implementation of this patch and it should work well.
>But it is also a new user interface which does not sound too extensible and
>does not seem to cooperate well with cgroup interface.
>
>It also introduces this new notion of niceness for task groups which is sort
>of equivalent to cpu.shares in cpu controller. First of all why should we
>not stick to shares notion even for autogroup. Even if we introduce the notion
>of niceness for groups, IMHO, it should be through cgroup interface instead of
>group niceness for autogroup and shares/weights for cgroup despite the
>fact that in the background they do similar things.
>

Hmm, maybe we can make AUTO_GROUP depend on !CGROUPS?

It seems that autogroup only uses 'struct task_group', no other cgroup things,
so I think that is reasonable and doable.
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