linux-kernel - Re: [PATCH v2] sched/deadline: remove useless param from setup_new_dl

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Date:	Tue, 5 Jul 2016 12:47:40 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	peterz@...radead.org, linux-kernel@...r.kernel.org,
	mingo@...hat.com, luca.abeni@...tn.it
Subject: Re: [PATCH v2] sched/deadline: remove useless param from
 setup_new_dl_entity

On Tue, 5 Jul 2016 15:39:33 +0100
Juri Lelli <juri.lelli@....com> wrote:

		return;
> > >  
> > >  	/*
> > > +	 * Use the scheduling parameters of the top pi-waiter task,
> > > +	 * if we have one from which we can inherit a deadline.
> > > +	 */
> > > +	if (pi_task && dl_se->dl_boosted && dl_prio(pi_task->normal_prio))
> > > +		pi_se = &pi_task->dl;
> > > +  
> > 
> > OK, I'm micro-optimizing now, but hey, isn't this a fast path?
> > 
> > What about changing the above to:
> > 
> > 	struct task_struct *pi_task;
> > 	[...]
> > 
> > 	if (dl_se->dl_boosted && dl_prio(pi_task->normal_prio &&  
>                                     ^
> OK, we need to reorder these two
>                                     V
> > 	    (pi_task = rt_mutex_get_top_task(dl_task_of(dl_se)))
> > 		pe_se = &pi_task->dl;

Opps, you're right.

> > 
> > This way we don't need to do any work of looking at
> > rt_mutex_get_top_task() for the normal case.
> >   
> 
> But, yes. Looks good to me. I'll shoot a v3 ASAP.

I have to ask, should there be any check if the dl_se has a shorter
deadline than the pi one?

-- Steve