linux-kernel - Re: [patch v5 01/15] sched: set initial value for runnable avg of sched entities.

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Date:	Mon, 18 Feb 2013 17:28:43 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Alex Shi <alex.shi@...el.com>
Cc:	torvalds@...ux-foundation.org, mingo@...hat.com,
	peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, bp@...en8.de,
	pjt@...gle.com, namhyung@...nel.org, efault@....de,
	vincent.guittot@...aro.org, gregkh@...uxfoundation.org,
	preeti@...ux.vnet.ibm.com, viresh.kumar@...aro.org,
	linux-kernel@...r.kernel.org, morten.rasmussen@....com
Subject: Re: [patch v5 01/15] sched: set initial value for runnable avg of
 sched entities.

Hello, Alex.

On Mon, Feb 18, 2013 at 01:07:28PM +0800, Alex Shi wrote:
> We need initialize the se.avg.{decay_count, load_avg_contrib} to zero
> after a new task forked.
> Otherwise random values of above variables cause mess when do new task

I think that these are not random values. In arch_dup_task_struct(),
we do '*dst = *src', so, these values come from parent process. If we use
these value appropriately, we can anticipate child process' load easily.
So to initialize the load_avg_contrib to zero is not good idea for me.

Thanks.

> enqueue:
>     enqueue_task_fair
>         enqueue_entity
>             enqueue_entity_load_avg
> 
> Signed-off-by: Alex Shi <alex.shi@...el.com>
> ---
>  kernel/sched/core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 26058d0..1743746 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1559,6 +1559,8 @@ static void __sched_fork(struct task_struct *p)
>  #if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)
>  	p->se.avg.runnable_avg_period = 0;
>  	p->se.avg.runnable_avg_sum = 0;
> +	p->se.avg.decay_count = 0;
> +	p->se.avg.load_avg_contrib = 0;
>  #endif
>  #ifdef CONFIG_SCHEDSTATS
>  	memset(&p->se.statistics, 0, sizeof(p->se.statistics));
> -- 
> 1.7.12
> 
> --
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