linux-kernel - Re: [RESEND PATCH 2/3 v5] sched: Rewrite per entity runnable load average tracking

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Message-ID: <20141021145652.GB23531@worktop.programming.kicks-ass.net>
Date:	Tue, 21 Oct 2014 16:56:52 +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: [RESEND PATCH 2/3 v5] sched: Rewrite per entity runnable load
 average tracking

On Fri, Oct 10, 2014 at 10:21:56AM +0800, Yuyang Du wrote:
>  static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
>  {
> -	long tg_weight;
> -
> -	/*
> -	 * Use this CPU's actual weight instead of the last load_contribution
> -	 * to gain a more accurate current total weight. See
> -	 * update_cfs_rq_load_contribution().
> -	 */
> -	tg_weight = atomic_long_read(&tg->load_avg);
> -	tg_weight -= cfs_rq->tg_load_contrib;
> -	tg_weight += cfs_rq->load.weight;
> -
> -	return tg_weight;
> +	return atomic_long_read(&tg->load_avg);

Since you're now also delaying updating load_avg, why not retain this
slightly better approximation?
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