linux-kernel - Re: [PATCH v2 2/2] sched/fair, cpufreq: Introduce 'runnable boosting'

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Date:   Sat, 13 May 2023 11:32:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Qais Yousef <qyousef@...alina.io>,
        Kajetan Puchalski <kajetan.puchalski@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Vincent Donnefort <vdonnefort@...gle.com>,
        Quentin Perret <qperret@...gle.com>,
        Abhijeet Dharmapurikar <adharmap@...cinc.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] sched/fair, cpufreq: Introduce 'runnable boosting'

On Fri, May 12, 2023 at 04:39:51PM +0200, Dietmar Eggemann wrote:
> On 12/05/2023 13:22, Peter Zijlstra wrote:
> > On Fri, May 12, 2023 at 12:10:29PM +0200, Dietmar Eggemann wrote:
> > 
> >> -static unsigned long cpu_util(int cpu, struct task_struct *p, int dst_cpu)
> >> +static unsigned long
> >> +cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost)
> >>  {
> >>  	struct cfs_rq *cfs_rq = &cpu_rq(cpu)->cfs;
> >>  	unsigned long util = READ_ONCE(cfs_rq->avg.util_avg);
> >> +	unsigned long runnable;
> >> +
> >> +	runnable = boost ? READ_ONCE(cfs_rq->avg.runnable_avg) : 0;
> >> +	util = max(util, runnable);
> >>  
> > 	if (boost)
> > 		util = max(util, READ_ONCE(cfs_rq->avg.runnable_avg));
> 
> I need the util_est = max(util_est, runnable) further down as well. Just
> want to fetch runnable only once.

Ah, fair enought; but still, please use a regular if().