linux-kernel - Re: [PATCH 7/7] sched/fair: Rename weighted_cpuload() to cpu

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Date:   Mon, 27 May 2019 12:24:07 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Quentin Perret <quentin.perret@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] sched/fair: Rename weighted_cpuload() to cpu_load()

On Mon, 2019-05-27 at 07:21 +0100, Dietmar Eggemann wrote:
> This is done to align the per cpu (i.e. per rq) load with the util
> counterpart (cpu_util(int cpu)). The term 'weighted' is not needed
> since there is no 'unweighted' load to distinguish it from.

I can see why you want to make cpu_util() and cpu_load()
have the same parameter, but ...

> @@ -7931,7 +7928,7 @@ static inline void update_sg_lb_stats(struct
> lb_env *env,
>  		if ((env->flags & LBF_NOHZ_STATS) &&
> update_nohz_stats(rq, false))
>  			env->flags |= LBF_NOHZ_AGAIN;
>  
> -		sgs->group_load += weighted_cpuload(rq);
> +		sgs->group_load += cpu_load(i);
>  		sgs->group_util += cpu_util(i);
>  		sgs->sum_nr_running += rq->cfs.h_nr_running;

... now we end up dereferencing cpu_rq(cpu) 3 times.

I guess per-cpu variables are so cheap that we should
never notice, but I thought I'd ask anyway while looking
over these patches :)

Thank you for removing a bunch of code that slowed down
my understanding of fair.c

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