linux-kernel - Re: [PATCH] sched: remove useless code in yield

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Message-ID: <1342118691.7430.39.camel@marge.simpson.net>
Date:	Thu, 12 Jul 2012 20:44:51 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] sched: remove useless code in yield_to

On Thu, 2012-07-12 at 16:07 +0200, Peter Zijlstra wrote: 
> On Tue, 2012-07-03 at 14:34 +0800, Michael Wang wrote:
> > From: Michael Wang <wangyun@...ux.vnet.ibm.com>
> > 
> > it's impossible to enter else branch if we have set skip_clock_update
> > in task_yield_fair(), as yield_to_task_fair() will directly return
> > true after invoke task_yield_fair().
> 
> It helps if you CC the guy who wrote the code.. I think you're right,
> although getting that skip_clock_update crap wrong is annoying.

Getting that crap wrong is ease, so Michael is probably right.

> Mike?

If it looks right to you too, it likely is.  When I have time to look
for nanoseconds again, I can squeak if/when I find some.  In any case,
for normal scheduler citizens, it's chump change, so nuke it.
> > Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
> > ---
> >  kernel/sched/core.c |    7 -------
> >  1 files changed, 0 insertions(+), 7 deletions(-)
> > 
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 9bb7d28..77c14aa 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -4737,13 +4737,6 @@ again:
> >  		 */
> >  		if (preempt && rq != p_rq)
> >  			resched_task(p_rq->curr);
> > -	} else {
> > -		/*
> > -		 * We might have set it in task_yield_fair(), but are
> > -		 * not going to schedule(), so don't want to skip
> > -		 * the next update.
> > -		 */
> > -		rq->skip_clock_update = 0;
> >  	}
> >  
> >  out:
> 
> --
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