linux-kernel - Re: [PATCH v5 1/2] sched/core: Minor optimize ttwu

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Message-ID: <20221221105202.52a0d793@gandalf.local.home>
Date:   Wed, 21 Dec 2022 10:52:02 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
        vschneid@...hat.com, linux-kernel@...r.kernel.org,
        bagasdotme@...il.com, yu.c.chen@...el.com
Subject: Re: [PATCH v5 1/2] sched/core: Minor optimize ttwu_runnable()

On Thu,  8 Dec 2022 11:20:06 +0800
Chengming Zhou <zhouchengming@...edance.com> wrote:

One nit.

> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3718,9 +3718,16 @@ static int ttwu_runnable(struct task_struct *p, int wake_flags)
>  
>  	rq = __task_rq_lock(p, &rf);
>  	if (task_on_rq_queued(p)) {
> -		/* check_preempt_curr() may use rq clock */
> -		update_rq_clock(rq);
> -		ttwu_do_wakeup(rq, p, wake_flags, &rf);
> +		if (!task_on_cpu(rq, p)) {
> +			/*
> +			 * When on_rq && !on_cpu the task is preempted, see if
> +			 * it should preempt whatever is current there now.

			* it should preempt the task that is current now.

Other than that.

Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- Steve

> +			 */
> +			update_rq_clock(rq);
> +			check_preempt_curr(rq, p, wake_flags);
> +		}
> +		WRITE_ONCE(p->__state, TASK_RUNNING);
> +		trace_sched_wakeup(p);
>  		ret = 1;
>  	}
>  	__task_rq_unlock(rq, &rf);