[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20110112080620.GG2723@in.ibm.com>
Date: Wed, 12 Jan 2011 13:36:20 +0530
From: Bharata B Rao <bharata@...ux.vnet.ibm.com>
To: Mike Galbraith <efault@....de>
Cc: Yong Zhang <yong.zhang0@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [patch] Re: autogroup: sched_setscheduler() fails
On Wed, Jan 12, 2011 at 08:24:41AM +0100, Mike Galbraith wrote:
> 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.
If cgroups doesn't want that task and if its transparent to cgroups,
why is it shown as part of /cgroups/tasks ? The task really doesn't
belong in there. Its not on the runqueue of root_task_group.
So basically I feel that a task consumed by autogroup shouldn't ideally be
shown in root cgroup's tasks file.
Regards,
Bharata.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists