linux-kernel - RE: [PATCH v7] cpufreq: intel_pstate: Implement passive mode with HWP enabled

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Date:   Sun, 6 Sep 2020 17:16:32 -0700
From:   "Doug Smythies" <dsmythies@...us.net>
To:     "'Rafael J. Wysocki'" <rjw@...ysocki.net>
Cc:     "'Linux Documentation'" <linux-doc@...r.kernel.org>,
        "'LKML'" <linux-kernel@...r.kernel.org>,
        "'Peter Zijlstra'" <peterz@...radead.org>,
        "'Srinivas Pandruvada'" <srinivas.pandruvada@...ux.intel.com>,
        "'Giovanni Gherdovich'" <ggherdovich@...e.cz>,
        "'Francisco Jerez'" <francisco.jerez.plata@...el.com>,
        "'Viresh Kumar'" <viresh.kumar@...aro.org>,
        "'Linux PM'" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH v7] cpufreq: intel_pstate: Implement passive mode with HWP enabled

Hi Rafael,

On 2020.08.17 14:06 Doug Smythies wrote:
> On 2020.08.06 05:04 Rafael J. Wysocki wrote:
> 
> > Allow intel_pstate to work in the passive mode with HWP enabled and
> > make it set the HWP minimum performance limit (HWP floor) to the
> > P-state value given by the target frequency supplied by the cpufreq
> > governor, so as to prevent the HWP algorithm and the CPU scheduler
> > from working against each other, at least when the schedutil governor
> > is in use, and update the intel_pstate documentation accordingly.
> 
...
> 
> powersave governor:
> acpi-cpufreq: good
> intel_cpufreq hwp: bad
> intel_cpufreq no hwp: good

It occurs to me that my expectations as to what 
is meant by "powersave" might not agree with yours. 

For the powersave governor, this is what we have now:

intel_cpufreq hwp == intel_pstate hwp
intel_cpufreq no hwp == acpi-cpufreq == always minimum freq
intel_pstate no hwp ~= acpi-cpufreq/ondemand

Is that your understanding/intention?

My expectation was/is:

intel_cpufreq hwp == intel_cpufreq no hwp == acpi-cpufreq == always minimum freq
intel_pstate no hwp ~= acpi-cpufreq/ondemand
intel_pstate hwp == Unique. Say, extremely course version of ondemand.

... Doug