linux-kernel - Re: [PATCH] sched: remove redundant check in select_task_rq

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Message-ID: <1307442043.3625.6.camel@marge.simson.net>
Date:	Tue, 07 Jun 2011 12:20:43 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>, mingo@...e.hu,
	linux-kernel@...r.kernel.org,
	Suresh Siddha <suresh.b.siddha@...el.com>
Subject: Re: [PATCH] sched: remove redundant check in select_task_rq_fair

On Tue, 2011-06-07 at 12:09 +0200, Peter Zijlstra wrote:
> On Tue, 2011-06-07 at 15:34 +0530, Nikunj A. Dadhania wrote:
> > On Tue, 07 Jun 2011 11:53:34 +0200, Peter Zijlstra <peterz@...radead.org> wrote:
> > > On Tue, 2011-06-07 at 15:18 +0530, Nikunj A. Dadhania wrote:
> > > > When balancing for wakeup affinity, a redundant check can removed.
> > > 
> > > Yes, tempting, but no, now you've got an extra call to wake_affine(),
> > > which is more expensive.
> 
> > Ah, got that. How about this, it is more readable. Other options would
> > be to add a comment.
> 
> > -		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
> > +		if (cpu != prev_cpu && wake_affine(affine_sd, p, sync))
> >  			prev_cpu = cpu;
> 
> I guess that depends on which way your head is wired and how strong your
> boolean algebra is.. Suresh, Mike any preference? I don't much care
> either way.

Me either.

	-Mike


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