linux-kernel - [PATCH v2 0/3] cpufreq: Allow drivers to receive more information from the governor

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Date:   Mon, 14 Dec 2020 21:01:52 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Doug Smythies <dsmythies@...us.net>,
        Giovanni Gherdovich <ggherdovich@...e.com>
Subject: [PATCH v2 0/3] cpufreq: Allow drivers to receive more information from the governor

Hi,

The timing of this is not perfect (sorry about that), but here's a refresh
of this series.

The majority of the previous cover letter still applies:

On Monday, December 7, 2020 5:25:38 PM CET Rafael J. Wysocki wrote:
> 
> This is based on the RFC posted a few days ago:
> 
> https://lore.kernel.org/linux-pm/1817571.2o5Kk4Ohv2@kreacher/
> 
>  Using intel_pstate in the passive mode with HWP enabled, in particular under
>  the schedutil governor, is still kind of problematic, because it has to assume
>  that it should not allow the frequency to fall below the one requested by the
>  governor.  For this reason, it translates the target frequency into HWP.REQ.MIN
>  which generally causes the processor to run a bit too fast.
> 
>  Moreover, this allows the HWP algorithm to use any frequency between the target
>  one and HWP.REQ.MAX that corresponds to the policy max limit and some workloads
>  cause it to go for the max turbo frequency prematurely which hurts energy-
>  efficiency without improving performance, even though the schedutil governor
>  itself would not allow the frequency to ramp up so fast.
> 
>  This patch series attempts to improve the situation by introducing a new driver
>  callback allowing the driver to receive more information from the governor.  In
>  particular, this allows the min (required) and target (desired) performance
>  levels to be passed to it and those can be used to give better hints to the
>  hardware.

In this second revision there are three patches (one preparatory patch for
schedutil that hasn't changed since the v1, the introduction of the new
callback and schedutil changes in patch [2/3] and the intel_pstate changes
in patch [3/3] that are the same as before.

Please see patch changelogs for details.

Thanks!