linux-kernel - Re: [PATCH] sched: fix how RT task is pulled

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Message-ID: <BANLkTikPhwajRBZ-dx46NnobOu10AmXoSg@mail.gmail.com>
Date:	Tue, 17 May 2011 10:35:37 +0800
From:	Yong Zhang <yong.zhang0@...il.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH] sched: fix how RT task is pulled

On Sun, May 15, 2011 at 10:50 AM, Hillf Danton <dhillf@...il.com> wrote:
> When pulling RT task for a given runqueue, if it is already overloaded
> with RT tasks, the pull operation could be avoided at the moment.
>
> btw, it looks like a typo?

No.

Below is how rt_overloaded() is realized:
static inline int rt_overloaded(struct rq *rq)
{
        return atomic_read(&rq->rd->rto_count);
}

You can notice it's about the overload of the very root_domain.

Thanks,
Yong

>
> Signed-off-by: Hillf Danton <dhillf@...il.com>
> ---
>  kernel/sched_rt.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
> index 19ecb31..14c764b 100644
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -1440,7 +1440,7 @@ static int pull_rt_task(struct rq *this_rq)
>        struct task_struct *p;
>        struct rq *src_rq;
>
> -       if (likely(!rt_overloaded(this_rq)))
> +       if (unlikely(rt_overloaded(this_rq)))
>                return 0;
>
>        for_each_cpu(cpu, this_rq->rd->rto_mask) {
>



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