linux-kernel - Re: [RFC 5/6] sched: pack the idle load balance

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Message-ID: <50880774.5090605@ti.com>
Date:	Wed, 24 Oct 2012 20:51:24 +0530
From:	Santosh Shilimkar <santosh.shilimkar@...com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linaro-dev@...ts.linaro.org>, <peterz@...radead.org>,
	<mingo@...hat.com>, <pjt@...gle.com>, <linux@....linux.org.uk>
Subject: Re: [RFC 5/6] sched: pack the idle load balance

On Sunday 07 October 2012 01:13 PM, Vincent Guittot wrote:
> Look for an idle CPU close the pack buddy CPU whenever possible.
s/close/close to
> The goal is to prevent the wake up of a CPU which doesn't share the power
> line of the pack CPU
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>   kernel/sched/fair.c |   18 ++++++++++++++++++
>   1 file changed, 18 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6df53b5..f76acdc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5158,7 +5158,25 @@ static struct {
>
>   static inline int find_new_ilb(int call_cpu)
>   {
> +	struct sched_domain *sd;
>   	int ilb = cpumask_first(nohz.idle_cpus_mask);
> +	int buddy = per_cpu(sd_pack_buddy, call_cpu);
> +
> +	/*
> +	 * If we have a pack buddy CPU, we try to run load balance on a CPU
> +	 * that is close to the buddy.
> +	 */
> +	if (buddy != -1)
> +		for_each_domain(buddy, sd) {
> +			if (sd->flags & SD_SHARE_CPUPOWER)
> +				continue;
Do you mean SD_SHARE_POWERLINE here ?
> +
> +			ilb = cpumask_first_and(sched_domain_span(sd),
> +					nohz.idle_cpus_mask);
> +
> +			if (ilb < nr_cpu_ids)
> +				break;
> +		}
>
>   	if (ilb < nr_cpu_ids && idle_cpu(ilb))
>   		return ilb;
>
Can you please expand "idle CPU _close_ the pack buddy CPU" ?

Regards
santosh
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