linux-kernel - Re: [PATCH 2/2 v4] sched: Rewrite per entity runnable load average tracking

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Date:	Mon, 28 Jul 2014 14:01:25 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Yuyang Du <yuyang.du@...el.com>
Cc:	mingo@...hat.com, linux-kernel@...r.kernel.org, pjt@...gle.com,
	bsegall@...gle.com, arjan.van.de.ven@...el.com,
	len.brown@...el.com, rafael.j.wysocki@...el.com,
	alan.cox@...el.com, mark.gross@...el.com, fengguang.wu@...el.com
Subject: Re: [PATCH 2/2 v4] sched: Rewrite per entity runnable load average
 tracking

On Fri, Jul 18, 2014 at 07:26:06AM +0800, Yuyang Du wrote:
> -static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update)
> +/* Add the load generated by se into cfs_rq's load average */
> +static inline void enqueue_entity_load_avg(struct sched_entity *se)
>  {
> +	struct sched_avg *sa = &se->avg;
> +	struct cfs_rq *cfs_rq = cfs_rq_of(se);
> +	u64 now = cfs_rq_clock_task(cfs_rq);
> +	int migrated = 0, decayed;
>  
> +	if (sa->last_update_time == 0) {
> +		sa->last_update_time = now;
>  
> +		if (entity_is_task(se))
> +			migrated = 1;
>  	}
> +	else
> +		__update_load_avg(now, sa, se->on_rq * se->load.weight);

That's a coding style fail, that should look like:

	if () {
	} else {
	}

>  
> +	decayed = update_cfs_rq_load_avg(now, cfs_rq);
>  
> +	if (migrated) {
> +		cfs_rq->avg.load_avg += sa->load_avg;
> +		cfs_rq->avg.load_sum += sa->load_sum;
>  	}
>  
> +	if (decayed || migrated)
> +		update_tg_load_avg(cfs_rq);
>  }


> @@ -2764,7 +2595,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
>  	 * Update run-time statistics of the 'current'.
>  	 */
>  	update_curr(cfs_rq);
> -	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
> +	enqueue_entity_load_avg(se);
>  	account_entity_enqueue(cfs_rq, se);
>  	update_cfs_shares(cfs_rq);
>  

Why did you remove the cfs_rq argumetn only to have to re-compute it?

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