linux-kernel - Re: [PATCH] sched: don't call task_group() many times in set_task

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Date:	Fri, 11 Nov 2011 13:26:05 -0800
From:	Paul Turner <pjt@...gle.com>
To:	Andrew Vagin <avagin@...nvz.org>
CC:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: Re: [PATCH] sched: don't call task_group() many times in set_task_rq()

On 11/11/2011 06:04 AM, Andrew Vagin wrote:
> It improves perfomance, especially if autogroup enabled.
>
> The size of set_task_rq() was 0x180 and now it is 0xa0.

A slightly more verbose commit message would be helpful here.

>
> Signed-off-by: Andrew Vagin<avagin@...nvz.org>

Signed-off-by: Paul Turner <pjt@...gle.com>

> ---
>   kernel/sched.c |   12 ++++++++----
>   1 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched.c b/kernel/sched.c
> index d87c6e5..a740eec 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -766,14 +766,18 @@ static inline struct task_group *task_group(struct task_struct *p)
>   /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
>   static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
>   {
> +#if defined(CONFIG_FAIR_GROUP_SCHED) || defined(CONFIG_RT_GROUP_SCHED)
> +	struct task_group *tg = task_group(p);
> +#endif
> +
>   #ifdef CONFIG_FAIR_GROUP_SCHED
> -	p->se.cfs_rq = task_group(p)->cfs_rq[cpu];
> -	p->se.parent = task_group(p)->se[cpu];
> +	p->se.cfs_rq = tg->cfs_rq[cpu];
> +	p->se.parent = tg->se[cpu];
>   #endif
>
>   #ifdef CONFIG_RT_GROUP_SCHED
> -	p->rt.rt_rq  = task_group(p)->rt_rq[cpu];
> -	p->rt.parent = task_group(p)->rt_se[cpu];
> +	p->rt.rt_rq  = tg->rt_rq[cpu];
> +	p->rt.parent = tg->rt_se[cpu];
>   #endif
>   }
>

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