linux-kernel - Re: [RFC v3 2/6] Improve the tracking of active utilisation

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Message-ID: <20161118153615.GM3142@twins.programming.kicks-ass.net>
Date:   Fri, 18 Nov 2016 16:36:15 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Luca Abeni <luca.abeni@...tn.it>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@....com>,
        Claudio Scordino <claudio@...dence.eu.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC v3 2/6] Improve the tracking of active utilisation

On Mon, Oct 24, 2016 at 04:06:34PM +0200, Luca Abeni wrote:
> @@ -514,7 +556,20 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
>  	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
>  	struct rq *rq = rq_of_dl_rq(dl_rq);
>  
> +	if (hrtimer_is_queued(&dl_se->inactive_timer)) {
> +		hrtimer_try_to_cancel(&dl_se->inactive_timer);
> +		WARN_ON(dl_task_of(dl_se)->nr_cpus_allowed > 1);

Isn't that always so? That is, DL tasks cannot be but 'global', right?

Also, you could use the return value of hrtimer_try_to_cancel() to
determine hrtimer_is_queued() I suppose.

> +	} else {
> +		/*
> +		 * The "inactive timer" has been cancelled in
> +		 * select_task_rq_dl() (and the acvive utilisation has
> +		 * been decreased). So, increase the active utilisation.
> +		 * If select_task_rq_dl() could not cancel the timer,
> +		 * inactive_task_timer() will * find the task state as
                                             ^^^
superfluous '*'?

> +		 * TASK_RUNNING, and will do nothing, so we are still safe.
> +		 */
> +		add_running_bw(dl_se, dl_rq);
> +	}
>  
>  	if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
>  	    dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {