linux-kernel - Re: [RFC V2 1/2] sched: Start tracking SCHED_IDLE tasks count in cfs

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Message-ID: <20190510065531.GF2623@hirez.programming.kicks-ass.net>
Date:   Fri, 10 May 2019 08:55:31 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>, tkjos@...gle.com,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        quentin.perret@...aro.org, chris.redpath@....com,
        Dietmar.Eggemann@....com, linux-kernel@...r.kernel.org
Subject: Re: [RFC V2 1/2] sched: Start tracking SCHED_IDLE tasks count in
 cfs_rq

On Thu, Apr 25, 2019 at 03:07:39PM +0530, Viresh Kumar wrote:
> @@ -5166,6 +5170,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  {
>  	struct cfs_rq *cfs_rq;
>  	struct sched_entity *se = &p->se;
> +	int idle_h_nr_running = unlikely(task_has_idle_policy(p)) ? 1 : 0;
>  
>  	/*
>  	 * The code below (indirectly) updates schedutil which looks at

> @@ -5266,6 +5273,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  	struct cfs_rq *cfs_rq;
>  	struct sched_entity *se = &p->se;
>  	int task_sleep = flags & DEQUEUE_SLEEP;
> +	int idle_h_nr_running = unlikely(task_has_idle_policy(p)) ? 1 : 0;
>  
>  	for_each_sched_entity(se) {
>  		cfs_rq = cfs_rq_of(se);

That's a completely pointless branch there (and I suspect the compiler
will see that too), just write:

	int idle_h_nr_running = task_has_idle_policy(p);