linux-kernel - Re: [PATCH 1/2] sched: recover SD_WAKE_AFFINE in select_task_rq

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Message-ID: <1343295457.6863.43.camel@marge.simpson.net>
Date:	Thu, 26 Jul 2012 11:37:37 +0200
From:	Mike Galbraith <efault@....de>
To:	Alex Shi <alex.shi@...el.com>
Cc:	mingo@...hat.com, peterz@...radead.org,
	linux-kernel@...r.kernel.org, suresh.b.siddha@...el.com
Subject: Re: [PATCH 1/2] sched: recover SD_WAKE_AFFINE in
 select_task_rq_fair and code clean up

On Thu, 2012-07-26 at 13:27 +0800, Alex Shi wrote:

> 	if (affine_sd) {
> -		if (cpu == prev_cpu || wake_affine(affine_sd, p, sync))
> +		if (wake_affine(affine_sd, p, sync))
>  			prev_cpu = cpu;
>  
>  		new_cpu = select_idle_sibling(p, prev_cpu);

Hm, if cpu == prev_cpu, asking wake_affine() if it's ok to put wakee
back where it came from is wasted cycles.. that's where the task is
headed regardless of reply.

-Mike

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