linux-kernel - Re: [PATCH] scheduler: introduce SCHED_RESET_ON

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Date:	Tue, 16 Jun 2009 18:47:42 +0200
From:	Lennart Poettering <mzxreary@...inter.de>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scheduler: introduce SCHED_RESET_ON_FORK scheduling
	policy flag, fourth try

On Tue, 16.06.09 11:05, Mike Galbraith (efault@....de) wrote:

> I think it's cleaner to keep reset_on_fork functionality separate.
> Thoughts on the below?

Looks good to me!

Lennart

> Make SCHED_RESET_ON_FORK to DTRT for reniced tasks, and make the sched_fork()
> SCHED_RESET_ON_FORK bits a self-contained unlikely code block.
> 
> Signed-off-by: Mike Galbraith <efault@....de>
> 
>  kernel/sched.c |   39 +++++++++++++++++++++++----------------
>  1 files changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 80636ed..cb6bbc6 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -2613,28 +2613,35 @@ void sched_fork(struct task_struct *p, int clone_flags)
>  	set_task_cpu(p, cpu);
>  
>  	/*
> -	 * Revert to default priority/policy on fork if requested. Make sure we
> -	 * do not leak PI boosting priority to the child.
> +	 * Make sure we do not leak PI boosting priority to the child.
>  	 */
> -	if (current->sched_reset_on_fork &&
> -			(p->policy == SCHED_FIFO || p->policy == SCHED_RR))
> -		p->policy = SCHED_NORMAL;
> +	p->prio = current->normal_prio;
>  
> -	if (current->sched_reset_on_fork &&
> -			(current->normal_prio < DEFAULT_PRIO))
> -		p->prio = DEFAULT_PRIO;
> -	else
> -		p->prio = current->normal_prio;
> +	/*
> +	 * Revert to default priority/policy on fork if requested.
> +	 */
> +	if (unlikely(p->sched_reset_on_fork)) {
> +		if (p->policy == SCHED_FIFO || p->policy == SCHED_RR)
> +			p->policy = SCHED_NORMAL;
> +
> +		if (p->normal_prio < DEFAULT_PRIO)
> +			p->prio = DEFAULT_PRIO;
> +
> +		if (PRIO_TO_NICE(p->static_prio) < 0) {
> +			p->static_prio = NICE_TO_PRIO(0);
> +			set_load_weight(p);
> +		}
> +
> +		/*
> +		 * We don't need the reset flag anymore after the fork. It has
> +		 * fulfilled its duty:
> +		 */
> +		p->sched_reset_on_fork = 0;
> +	}
>  
>  	if (!rt_prio(p->prio))
>  		p->sched_class = &fair_sched_class;
>  
> -	/*
> -	 * We don't need the reset flag anymore after the fork. It has
> -	 * fulfilled its duty:
> -	 */
> -	p->sched_reset_on_fork = 0;
> -
>  #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
>  	if (likely(sched_info_on()))
>  		memset(&p->sched_info, 0, sizeof(p->sched_info));
> 


Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4
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