linux-kernel - Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

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Date:   Fri, 22 Dec 2017 12:46:18 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     Juri Lelli <juri.lelli@...hat.com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

On Fri, Dec 22, 2017 at 11:02:06AM +0000, Patrick Bellasi wrote:
> > @@ -315,8 +315,8 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
> >  		unsigned long j_util, j_max;
> >  		s64 delta_ns;
> >  
> > -		if (j_sg_cpu != sg_cpu)
> > -			sugov_get_util(j_sg_cpu);
> > +		if (idle_cpu(j))
> > +			continue;
> 
> That should work to skip IDLE CPUs... however I'm missing where now we
> get the sugov_get_util(j_sg_cpu) for active CPUs. It has been moved
> somewhere else I guess...

No, I'm just an idiot... lemme fix that.

> Moreover, that way don't we completely disregard CFS blocked load for
> IDLE CPUs... as well as DL reserved utilization, which should be
> released only at the 0-lag time?

I was thinking that since dl is a 'global' scheduler the reservation
would be too and thus the freq just needs a single CPU to be observed;
but I suppose there's nothing stopping anybody from splitting a clock
domain down the middle scheduling wise. So yes, good point.

Blergh that'd make a mess of things again.