linux-kernel - Re: [PATCH v4 1/7] sched: Unify runtime accounting across classes

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Date:   Fri, 15 Sep 2023 17:41:20 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Daniel Bristot de Oliveira <bristot@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joel Fernandes <joel@...lfernandes.org>,
        Vineeth Pillai <vineeth@...byteword.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v4 1/7] sched: Unify runtime accounting across classes

On Thu, 31 Aug 2023 22:28:52 +0200
Daniel Bristot de Oliveira <bristot@...nel.org> wrote:

As I have a vested interest in this work, I started a deep dive into the
code.

> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1299,9 +1299,8 @@ static void update_curr_dl(struct rq *rq)
>  {
>  	struct task_struct *curr = rq->curr;
>  	struct sched_dl_entity *dl_se = &curr->dl;
> -	u64 delta_exec, scaled_delta_exec;
> +	s64 delta_exec, scaled_delta_exec;
>  	int cpu = cpu_of(rq);
> -	u64 now;
>  
>  	if (!dl_task(curr) || !on_dl_rq(dl_se))
>  		return;
> @@ -1314,21 +1313,13 @@ static void update_curr_dl(struct rq *rq)
>  	 * natural solution, but the full ramifications of this
>  	 * approach need further study.
>  	 */
> -	now = rq_clock_task(rq);
> -	delta_exec = now - curr->se.exec_start;
> -	if (unlikely((s64)delta_exec <= 0)) {
> +	delta_exec = update_curr_common(rq);

I have to say, mapping the update_curr_common() to the removed code below,
wasn't as easy as I thought it would be, as the above function is broken up
slightly differently.

But the conclusion does appear to be pretty much the same.

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

-- Steve


> +	if (unlikely(delta_exec <= 0)) {
>  		if (unlikely(dl_se->dl_yielded))
>  			goto throttle;
>  		return;
>  	}
>  
> -	schedstat_set(curr->stats.exec_max,
> -		      max(curr->stats.exec_max, delta_exec));
> -
> -	trace_sched_stat_runtime(curr, delta_exec, 0);
> -
> -	update_current_exec_runtime(curr, now, delta_exec);
> -
>  	if (dl_entity_is_special(dl_se))
>  		return;
>