linux-kernel - Re: [PATCH 2/8] sched/fair: add margin to utilization update

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Message-ID: <20160315211614.GC6344@twins.programming.kicks-ass.net>
Date:	Tue, 15 Mar 2016 22:16:14 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Michael Turquette <mturquette@...libre.com>
Cc:	rjw@...ysocki.net, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, Juri.Lelli@....com,
	steve.muckle@...aro.org, morten.rasmussen@....com,
	dietmar.eggemann@....com, vincent.guittot@...aro.org,
	Michael Turquette <mturquette+renesas@...libre.com>
Subject: Re: [PATCH 2/8] sched/fair: add margin to utilization update

On Sun, Mar 13, 2016 at 10:22:06PM -0700, Michael Turquette wrote:
> @@ -2840,6 +2853,8 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
>  
>  	if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
>  		unsigned long max = rq->cpu_capacity_orig;
> +		unsigned long cap = cfs_rq->avg.util_avg *
> +			cfs_capacity_margin / max;
>  
>  		/*
>  		 * There are a few boundary cases this might miss but it should
> @@ -2852,8 +2867,7 @@ static inline void update_load_avg(struct sched_entity *se, int update_tg)
>  		 * thread is a different class (!fair), nor will the utilization
>  		 * number include things like RT tasks.
>  		 */
> -		cpufreq_update_util(rq_clock(rq),
> -				    min(cfs_rq->avg.util_avg, max), max);
> +		cpufreq_update_util(rq_clock(rq), min(cap, max), max);
>  	}
>  }

I really don't see why that is here, and not inside whatever uses
cpufreq_update_util().