linux-kernel - Re: cpufreq: intel_pstate: map utilization into the pstate range

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Date:   Thu, 06 Jan 2022 13:55:50 -0800
From:   srinivas pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     Francisco Jerez <currojerez@...eup.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: cpufreq: intel_pstate: map utilization into the pstate range

On Thu, 2022-01-06 at 21:43 +0100, Julia Lawall wrote:
> > > All the turbostat output and graphs I have sent recently were
> > > just
> > > for
> > > continuous spinning:
> > > 
> > > for(;;);
> > > 
> > > Now I am trying running for the percentage of the time
> > > corresponding
> > > to
> > > 10 / P for pstate P (ie 0.5 of the time for pstate 20), and then
> > > sleeping,
> > > to see whether one can just add the sleeping power consumption of
> > > the
> > > machine to compute the efficiency as Rafael suggested.
> > > 
> > Before doing comparison try freezing uncore.
> > 
> > wrmsr -a 0x620 0x0808
> > 
> > to Freeze uncore at 800MHz. Any other value is fine.
> 
> Thanks for the suggestion.  What is the impact of this?
Uncore scales based on its own heuristics based in P-state change and
works in package scope. So to actually see the effect of P-state change
on energy you can remove variability of uncore power.

Thanks,
Srinivas

> 
> julia