linux-kernel - Re: [PATCH] sched:skip loop non-idle cpus after find an idle cpu while find_idlest

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Message-ID: <20141027080422.GB10867@linux.vnet.ibm.com>
Date:	Mon, 27 Oct 2014 13:34:22 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Yao Dongdong <yaodongdong@...wei.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched:skip loop non-idle cpus after find an idle cpu
 while find_idlest_cpu

* Yao Dongdong <yaodongdong@...wei.com> [2014-10-27 11:13:17]:

> Idle cpu is idler than non-idle cpu, so we needn't loop non-idle cpus after find an idle cpu.
> 

While this check looks good,
I dont see how we are avoiding a loop?

Are you suggesting that we break of the for loop once we set
shallowest_idle_cpu?

-- 
Thanks and Regards
Srikar


> Signed-off-by:yaodongdong@...wei.com
> 
> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0b069bf..2445a23 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4446,7 +4446,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
>                                 latest_idle_timestamp = rq->idle_stamp;
>                                 shallowest_idle_cpu = i;
>                         }
> -               } else {
> +               } else if (shallowest_idle_cpu == -1) {
>                         load = weighted_cpuload(i);
>                         if (load < min_load || (load == min_load && i == this_cpu)) {
>                                 min_load = load;
> --
> 1.8.0.1
> 
> --
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-- 
Thanks and Regards
Srikar Dronamraju

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