linux-kernel - Re: [PATCH 0/4] consolidate and cleanup CPU capacity

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Message-ID: <CAKfTPtC+qBEjnwketZRdF6Lgbr9aCYNW1sqSVe5-TJfUq25p8w@mail.gmail.com>
Date:   Mon, 25 Sep 2023 14:05:43 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, sudeep.holla@....com,
        gregkh@...uxfoundation.org, rafael@...nel.org, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        viresh.kumar@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-pm@...r.kernel.org, conor.dooley@...rochip.com,
        suagrfillet@...il.com, ajones@...tanamicro.com, lftan@...nel.org
Subject: Re: [PATCH 0/4] consolidate and cleanup CPU capacity

On Thu, 21 Sept 2023 at 12:12, Ionela Voinescu <ionela.voinescu@....com> wrote:
>
> On Friday 01 Sep 2023 at 15:03:08 (+0200), Vincent Guittot wrote:
> > This is the 1st part of consolidating how the max compute capacity is
> > used in the scheduler and how we calculate the frequency for a level of
> > utilization.
> >
> > Fix some unconsistancy when computing frequency for an utilization. There
> > can be a mismatch between energy model and schedutil.
>
> There are a few more pieces of functionality that would be worth
> consolidating in this set as well, if you'd like to consider them:
>
> - arch_set_freq_scale() still uses policy->cpuinfo.max_freq. It might be
>   good to use the boot time stored max_freq here as well. Given that
>   arch_scale_cpu_capacity() would be based on that stored value, if
>   arch_scale_freq_capacity() ends up using a different value, it could
>   have interesting effects on the utilization signals in case of
>   boosting.

That's a good point, I will have a look at this part too. From a quick
look, this seems to be only used by  architecture that are using
arch_topology.c too


>
> - As Pierre mentioned in a previous comment, there is already a
>   cpufreq_get_hw_max_freq() weak function that returns
>   policy->cpuinfo.max_freq and it's only used at boot time by
>   the setup code for AMU use for frequency invariance. I'm tempted to
>   suggest to use this to initialize what is now "freq_factor" as my
>   intention when I created that function was to provide platform
>   providers with the possibility to implement their own and decide on
>   the frequency they choose as their maximum. This could have been an
>   arch_ function as well, but as you mentioned before, mobile and server
>   platforms might want to choose different maximum values even if they
>   are using the same architecture.
>
> Thanks,
> Ionela.
>
> >
> > Next step will be to make a difference between the original
> > max compute capacity of a CPU and what is currently available when
> > there is a capping applying forever (i.e. seconds or more).
> >
> > Vincent Guittot (4):
> >   sched: consolidate and cleanup access to CPU's max compute capacity
> >   topology: add a new arch_scale_freq_reference
> >   cpufreq/schedutil: use a fixed reference frequency
> >   energy_model: use a fixed reference frequency
> >
> >  arch/arm/include/asm/topology.h   |  1 +
> >  arch/arm64/include/asm/topology.h |  1 +
> >  arch/riscv/include/asm/topology.h |  1 +
> >  drivers/base/arch_topology.c      |  9 +++------
> >  include/linux/arch_topology.h     |  7 +++++++
> >  include/linux/energy_model.h      | 20 +++++++++++++++++---
> >  kernel/sched/core.c               |  2 +-
> >  kernel/sched/cpudeadline.c        |  2 +-
> >  kernel/sched/cpufreq_schedutil.c  | 29 +++++++++++++++++++++++++++--
> >  kernel/sched/deadline.c           |  4 ++--
> >  kernel/sched/fair.c               | 18 ++++++++----------
> >  kernel/sched/rt.c                 |  2 +-
> >  kernel/sched/sched.h              |  6 ------
> >  kernel/sched/topology.c           |  7 +++++--
> >  14 files changed, 75 insertions(+), 34 deletions(-)
> >
> > --
> > 2.34.1
> >
> >