linux-kernel - Re: [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load

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Message-ID: <20160401092019.GN3430@twins.programming.kicks-ass.net>
Date:	Fri, 1 Apr 2016 11:20:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steve Muckle <steve.muckle@...aro.org>
Cc:	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Juri Lelli <Juri.Lelli@....com>,
	Patrick Bellasi <patrick.bellasi@....com>,
	Michael Turquette <mturquette@...libre.com>
Subject: Re: [PATCH 1/2] sched/fair: move cpufreq hook to
 update_cfs_rq_load_avg()

On Thu, Mar 31, 2016 at 02:26:06PM -0700, Steve Muckle wrote:
> > Can't, the way the wakeup path is constructed we would be sending the
> > IPI way before we know about utilization.
> 
> Sorry I thought we were referring to the possibility of sending an IPI
> to just run the cpufreq driver rather than to conduct the whole wakeup
> operation.
> 
> My thinking was in CFS we get rid of the (cpu == smp_processor_id())
> condition for calling the cpufreq hook.
> 
> The sched governor can then calculate utilization and frequency required
> for cpu. If (cpu == smp_processor_id()), the update is processed
> normally. If (cpu != smp_processor_id()) and the new frequency is higher
> than cpu's Fcur, the sched gov IPIs cpu to continue running the update
> operation. Otherwise, the update is dropped.
> 
> Does that sound plausible?

Can be done I suppose..