linux-kernel - Re: [RFC PATCH] sched: select_idle

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Date:	Thu, 16 Jan 2014 21:13:25 +0800
From:	Alex Shi <alex.shi@...aro.org>
To:	mingo@...hat.com, peterz@...radead.org, morten.rasmussen@....com,
	vincent.guittot@...aro.org, daniel.lezcano@...aro.org
CC:	wangyun@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Alex Shi <alex.shi@...aro.org>, Mike Galbraith <efault@....de>
Subject: Re: [RFC PATCH] sched: select_idle_sibling macro optimize

Add Mike Galbraith.

Any one like to give some comments?

On 01/15/2014 10:23 PM, Alex Shi wrote:
> If the sd domain just has one group, then we must be caught the
> 	i == target later, and then goes to deeper level domain.
> So just skip this domain checking to save some instructions.
> 
> Signed-off-by: Alex Shi <alex.shi@...aro.org>
> ---
>  kernel/sched/fair.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index c7395d9..3265fbc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4196,6 +4196,11 @@ static int select_idle_sibling(struct task_struct *p, int target)
>  	sd = rcu_dereference(per_cpu(sd_llc, target));
>  	for_each_lower_domain(sd) {
>  		sg = sd->groups;
> +
> +		/* skip single group domain */
> +		if (sg == sg->next)
> +			continue;
> +
>  		do {
>  			if (!cpumask_intersects(sched_group_cpus(sg),
>  						tsk_cpus_allowed(p)))
> 


-- 
Thanks
    Alex
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