linux-kernel - Re: [RFC][PATCH] sched: Avoid select_idle_sibling() for wake

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Message-ID: <20130926100511.GJ26785@twins.programming.kicks-ass.net>
Date:	Thu, 26 Sep 2013 12:05:11 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mike Galbraith <bitbucket@...ine.de>
Cc:	Ingo Molnar <mingo@...nel.org>, Paul Turner <pjt@...gle.com>,
	Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] sched: Avoid select_idle_sibling() for
 wake_affine(.sync=true)

On Thu, Sep 26, 2013 at 11:58:12AM +0200, Peter Zijlstra wrote:
> @@ -3429,6 +3440,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
>  	int want_affine = 0;
>  	int sync = wake_flags & WF_SYNC;
>  
> +	if (sync)
> +		p->se.last_sync_wakeup = sched_clock_cpu(cpu);
> +
>  	if (p->nr_cpus_allowed == 1)
>  		return prev_cpu;
>  

Oh, I suppose something like:

 if (sync && !p->se.last_sync_wakeup)
 	p->se.last_sync_wakeup = sched_clock_cpu(cpu);

is also a nice variation to try..
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