linux-kernel - Re: [PATCH 1/7] sched/core: uclamp: add CPU clamp groups accounting

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Message-ID: <20180413111753.GT14248@e110439-lin>
Date:   Fri, 13 Apr 2018 12:17:53 +0100
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>
Subject: Re: [PATCH 1/7] sched/core: uclamp: add CPU clamp groups accounting

On 13-Apr 10:40, Peter Zijlstra wrote:
> On Mon, Apr 09, 2018 at 05:56:09PM +0100, Patrick Bellasi wrote:
> > +static inline void init_uclamp(void)
> 
> WTH is that inline?

You mean I can avoid the attribute?
... or that I should do it in another way?

> > +{
> > +	struct uclamp_cpu *uc_cpu;
> > +	int clamp_id;
> > +	int cpu;
> > +
> > +	mutex_init(&uclamp_mutex);
> > +
> > +	for (clamp_id = 0; clamp_id < UCLAMP_CNT; ++clamp_id) {
> > +		/* Init CPU's clamp groups */
> > +		for_each_possible_cpu(cpu) {
> > +			uc_cpu = &cpu_rq(cpu)->uclamp[clamp_id];
> > +			memset(uc_cpu, UCLAMP_NONE, sizeof(struct uclamp_cpu));
> > +		}
> > +	}
> 
> Those loops are the wrong way around, this shreds your cache. This is a
> slow path so it doesn't much matter, but it is sloppy.

Yess... my bad!... good catch! ;)

> 
> > +}

-- 
#include <best/regards.h>

Patrick Bellasi