linux-kernel - Re: [RFC/RFT][PATCH 0/4] cpufreq / sched: iowait boost in intel

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Date:   Mon, 05 Sep 2016 01:54:40 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Doug Smythies <dsmythies@...us.net>
Cc:     'Linux PM list' <linux-pm@...r.kernel.org>,
        'Linux Kernel Mailing List' <linux-kernel@...r.kernel.org>,
        'Srinivas Pandruvada' <srinivas.pandruvada@...ux.intel.com>,
        'Peter Zijlstra' <peterz@...radead.org>,
        'Viresh Kumar' <viresh.kumar@...aro.org>,
        'Ingo Molnar' <mingo@...hat.com>,
        'Vincent Guittot' <vincent.guittot@...aro.org>,
        'Morten Rasmussen' <morten.rasmussen@....com>,
        'Juri Lelli' <Juri.Lelli@....com>,
        'Dietmar Eggemann' <dietmar.eggemann@....com>,
        'Steve Muckle' <smuckle@...aro.org>,
        'Doug Smythies' <doug.smythies@...il.com>
Subject: Re: [RFC/RFT][PATCH 0/4] cpufreq / sched: iowait boost in intel_pstate and schedutil

On Sunday, September 04, 2016 08:54:49 AM Doug Smythies wrote:
> Hi Rafael,
> 
> On 2016.09.02 17:57 Rafael J. Wysocki wrote:
> 
> > This is a new version of the "iowait boost" series I posted a few weeks
> > ago.  Since the first two patches from that series have been reworked and
> > are in linux-next now, I've rebased this series on top of my linux-next
> > branch.
> >
> > In addition to that I took the Doug's feedback into account in the
> > intel_pstate patches [2-3/4].
> 
> You got ahead of me a little.
> Recall the suggestion for the addition of some filtering was based
> on energy savings. And further that it might make sense to use
> average pstate as input to the filter (your new patch 3 of 4).
> In my testing (of the old patch set) I have been finding that some
> of those energy savings are being given back by the average pstate
> method, putting its value added into question.
> 
> Switching to the new patch set, I made two kernels (based on 4.8-rc4
> + your pre-requisite 2 patches):
> rfc4: has all 4 patches.
> rfc2: has patches 1, 2, 4. (does not have the average pstate change)
> 
> Using my SpecPower simulator test at 20% load I get:
> 
> Unpatched (reference): ~5905 Joules
> rfc4: ~ 6232 Joules (+5.5%)
> rfc2: ~ 6075 Joules (+2.9%)
> Old rfc, no filter (restated): ~7197 Joules (+21.9%)
> Old rfc + old iir filter V2: ~5967 Joules (+1%)
> Old rfc + old ave pstate method: ~6275 Joules (+6.3%)
> 
> Srinivas was getting considerably different, but still
> encouraging, numbers on the real SpecPower test beds.
> 
> I would like to suggest/ask that those real SpecPower tests be done
> first so as to decide a preferred way forward. I'll also re-do my
> simulator tests over a longer time period and at some other loads
> (currently 20% is hard coded).

The reason I made patch [3/4] separate was to make it easier to test without
that change.  That is, apply [1-2/4] and see what difference it makes.

I'd like to see the results from that if poss.

Thanks,
Rafael