Re: [PATCH] scheduler: introduce SCHED_RESET_ON_FORK schedulingpolicy flag, fourth try

From: Lennart Poettering
Date: Tue Jun 16 2009 - 12:48:22 EST


On Tue, 16.06.09 11:05, Mike Galbraith (efault@xxxxxx) 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@xxxxxx>
>
> 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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