Date: Fri, 1 Apr 2016 11:20:19 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Steve Muckle <steve.muckle@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, "Rafael J. Wysocki" <rafael@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Juri Lelli <Juri.Lelli@arm.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>,
        Michael Turquette <mturquette@baylibre.com>
Subject: Re: [PATCH 1/2] sched/fair: move cpufreq hook to
 update_cfs_rq_load_avg()
Message-ID: <20160401092019.GN3430@twins.programming.kicks-ass.net>
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 <56F98832.3030207@linaro.org>
 <20160330193544.GD407@worktop>
 <56FC807C.80204@linaro.org>
 <20160331073743.GF3408@twins.programming.kicks-ass.net>
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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..