linux-kernel - Re: [PATCH V2] sched, autogroup: always show autogroup name in sched

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Date:	Tue, 22 Feb 2011 22:32:59 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH V2] sched, autogroup: always show autogroup name in
 sched_debug

On Tue, Feb 22, 2011 at 03:02:00PM +0100, Mike Galbraith wrote:
> On Tue, 2011-02-22 at 20:10 +0800, Yong Zhang wrote:
> > On Tue, Feb 22, 2011 at 10:56:06AM +0100, Peter Zijlstra wrote:
> > > On Tue, 2011-02-22 at 11:13 +0800, Yong Zhang wrote:
> > > > So show autogroup name always. But for the root group,
> > > > its name will dance between "cfs_rq[cpu]:" and
> > > > "cfs_rq[cpu]:/autogroup-0" according to
> > > > sysctl_sched_autogroup_enabled. 
> > > 
> > > Would it make sense to force the root group to always be a !autogroup?
> > 
> > Hmmm, I think it's ok.
> 
> Yup, it's not an autogroup, so let's stop claiming it.
> 
> sched, autogroup: stop claiming ownership of the root task group.
> 
> Disown it, and only display autogroup association if one exists.
> 
> Signed-off-by: Mike Galbraith <efault@....de>

Ah, I like this one better :)
Actually I misunderstanded what Peter mean.

Reviewed-by: Yong Zhang <yong.zhang0@...il.com>

Thanks,
Yong
> 
> diff --git a/kernel/sched_autogroup.c b/kernel/sched_autogroup.c
> index 9fb6562..506faa0 100644
> --- a/kernel/sched_autogroup.c
> +++ b/kernel/sched_autogroup.c
> @@ -12,7 +12,6 @@ static atomic_t autogroup_seq_nr;
>  static void __init autogroup_init(struct task_struct *init_task)
>  {
>  	autogroup_default.tg = &root_task_group;
> -	root_task_group.autogroup = &autogroup_default;
>  	kref_init(&autogroup_default.kref);
>  	init_rwsem(&autogroup_default.lock);
>  	init_task->signal->autogroup = &autogroup_default;
> @@ -130,7 +129,7 @@ task_wants_autogroup(struct task_struct *p, struct task_group *tg)
>  
>  static inline bool task_group_is_autogroup(struct task_group *tg)
>  {
> -	return tg != &root_task_group && tg->autogroup;
> +	return !!tg->autogroup;
>  }
>  
>  static inline struct task_group *
> @@ -247,10 +246,14 @@ void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
>  {
>  	struct autogroup *ag = autogroup_task_get(p);
>  
> +	if (!task_group_is_autogroup(ag->tg))
> +		goto out;
> +
>  	down_read(&ag->lock);
>  	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
>  	up_read(&ag->lock);
>  
> +out:
>  	autogroup_kref_put(ag);
>  }
>  #endif /* CONFIG_PROC_FS */
> @@ -258,9 +261,7 @@ void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
>  #ifdef CONFIG_SCHED_DEBUG
>  static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
>  {
> -	int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
> -
> -	if (!enabled || !tg->autogroup)
> +	if (!task_group_is_autogroup(tg))
>  		return 0;
>  
>  	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
> 
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