From: Mike Galbraith <efault@gmx.de>
To: bharata@linux.vnet.ibm.com
Cc: Yong Zhang <yong.zhang0@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org
Subject: Re: [patch] Re: autogroup: sched_setscheduler() fails
Date: Wed, 12 Jan 2011 08:24:41 +0100 [thread overview]
Message-ID: <1294817081.8370.60.camel@marge.simson.net> (raw)
In-Reply-To: <20110112063543.GD2723@in.ibm.com>
On Wed, 2011-01-12 at 12:05 +0530, Bharata B Rao wrote:
> On Wed, Jan 12, 2011 at 01:40:32PM +0800, Yong Zhang wrote:
> > IMHO, task->cgroups will not change when autogroup take effect.
>
> Yes and I believe this is cause for some of the weird semantics I see
> with autogroup and cgroups. I am not sure if this has already been
> discussed ealier, may be I need to go back and check the archives, but
> consider this:
>
> I have cpu cgroup mounted at /cgroup and see that all the tasks in the
> system are listed in /cgroup/tasks file.
>
> Now I start a task like this:
>
> # ./while1 &
> [1] 2761
>
> and see that this task belongs to root cgroup.
Yes, cgroups sees cgroup associations, not autogroup associations.
> # grep 2761 /cgroup/tasks
> 2671
>
> But we know that this task really belongs to an autogroup and is not
> sitting directly on root_task_group.
Yup, cgroups doesn't want it, so autogroup (if enabled) claims it.
> # cat /proc/2761/autogroup
> /autogroup-49 nice 0
>
> So we have a task in an autogroup (which is a sub group of root_task_group)
> but is being shown as part of root_task_group. Is this by design ?
Yes, it's supposed to be transparent to cgroups.
> Now say I create a sub cgroup and move this task to it.
>
> # mkdir /cgroup/1
> # echo 2671 > /cgroup/1/tasks
>
> So now the task moved to a real cgroup.
>
> # cat /cgroup/1/tasks
> 2761
>
> But the /proc/2761/autogroup isn't updated. It still shows
> /autogroup-49 nice 0
The proc interface shows task->autogroup associations, which always
exist. This is autogroups' view of the world, just as cgroup/tasks is
cgroups' view of it's world.
> May be this was all discussed earlier as I noted in the beginning, but I find
> this semantics a bit unusual.
Makes perfect sense to me.
-Mike
next prev parent reply other threads:[~2011-01-12 7:24 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-10 9:16 Bharata B Rao
2011-01-10 10:29 ` [patch] " Mike Galbraith
2011-01-10 10:59 ` Peter Zijlstra
2011-01-10 16:42 ` Mike Galbraith
2011-01-11 17:10 ` Bharata B Rao
2011-01-11 18:48 ` Mike Galbraith
2011-01-12 3:37 ` Bharata B Rao
2011-01-12 5:40 ` Yong Zhang
2011-01-12 6:35 ` Bharata B Rao
2011-01-12 7:24 ` Mike Galbraith [this message]
2011-01-12 8:06 ` Bharata B Rao
2011-01-12 8:47 ` Mike Galbraith
2011-01-12 9:26 ` Bharata B Rao
2011-01-12 6:17 ` Mike Galbraith
2011-01-12 6:42 ` Bharata B Rao
2011-01-12 5:40 ` Mike Galbraith
2011-01-12 6:32 ` Yong Zhang
2011-01-12 8:55 ` Mike Galbraith
2011-01-13 3:54 ` Mike Galbraith
2011-01-13 5:59 ` Yong Zhang
2011-01-13 6:02 ` Yong Zhang
2011-01-13 6:13 ` Mike Galbraith
2011-01-13 8:46 ` Bharata B Rao
2011-01-17 13:16 ` Peter Zijlstra
2011-02-15 15:46 ` torbenh
2011-02-15 16:43 ` Mike Galbraith
2011-02-18 11:09 ` torbenh
2011-02-18 12:50 ` Mike Galbraith
2011-02-18 13:40 ` torbenh
2011-02-22 12:24 ` torbenh
2011-02-22 14:47 ` Mike Galbraith
2011-02-28 17:53 ` torbenh
2011-02-28 18:29 ` Mike Galbraith
2011-02-28 19:10 ` torbenh
2011-03-01 4:02 ` Mike Galbraith
2011-03-01 4:21 ` Mike Galbraith
2011-03-01 15:59 ` torbenh
2011-01-18 19:05 ` [tip:sched/urgent] sched, autogroup: Fix CONFIG_RT_GROUP_SCHED sched_setscheduler() failure tip-bot for Mike Galbraith
2011-01-12 5:43 ` [patch] Re: autogroup: sched_setscheduler() fails Yong Zhang
2011-01-12 6:25 ` Mike Galbraith
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