Date: Thu, 10 Mar 2016 11:30:08 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Juri Lelli <juri.lelli@arm.com>, mturquette <mturquette@baylibre.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Steve Muckle <steve.muckle@linaro.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH 6/6] cpufreq: schedutil: New governor based on scheduler
 utilization data
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On Thu, Mar 10, 2016 at 05:23:54PM +0700, Vincent Guittot wrote:

> > No, since its a compile time thing, we can simply do:
> >
> > #ifdef arch_scale_freq_capacity
> >         next_freq = (1 + 1/n) * max_freq * (util / max)
> > #else
> >         next_freq = (1 + 1/n) * current_freq * (util_raw / max)
> > #endif
> 
> selecting formula at compilation is clearly better. I wrongly thought that
> it can't be accepted as a solution.

Well, its bound to get more 'interesting' since I forse implementations
not always actually doing the invariant thing.

Take for example the thing I send:

  lkml.kernel.org/r/20160303162829.GB6375@twins.programming.kicks-ass.net

it both shows why you cannot talk about current_freq but also that the
above needs a little more help (for the !X86_FEATURE_APERFMPERF case).

But the !arch_scale_freq_capacity case should indeed be that simple.