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

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Message-ID: <20201215041651.da3ii74xuc5orddp@vireshk-i7>
Date:   Tue, 15 Dec 2020 09:46:51 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Doug Smythies <dsmythies@...us.net>,
        Giovanni Gherdovich <ggherdovich@...e.com>
Subject: Re: [PATCH v2 0/3] cpufreq: Allow drivers to receive more
 information from the governor

On 14-12-20, 21:01, Rafael J. Wysocki wrote:
> 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.

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh