linux-kernel - Re: [PATCH 0/3] arch_topology, ACPI: populate cpu capacity from CPPC

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Message-ID: <20210519095128.GC21501@arm.com>
Date:   Wed, 19 May 2021 10:51:28 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Valentin Schneider <valentin.schneider@....com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/3] arch_topology, ACPI: populate cpu capacity from CPPC

Hi Valentin,

On Tuesday 18 May 2021 at 14:12:03 (+0100), Valentin Schneider wrote:
> Hi,
> 
> On 14/05/21 10:53, Ionela Voinescu wrote:
> > Hi all,
> >
> > These are a few trivial patches to populate cpu capacity information
> > using performance information from ACPI's CPPC.
> >
> > I've tied this functionality to the existing function
> > init_freq_invariance_cppc() called in acpi_cppc_processor_probe().
> > This function is renamed to a more generic arch_init_invariance_cppc().
> >
> > The patches have been build tested on x86 and more thoroughly tested on
> > Juno R2 (arm64), which uses the new functionality, with the following
> > results:
> >
> >
> > root@...ntu:~# dmesg | grep cpu_capacity
> > [    2.157494] init_cpu_capacity_cppc: CPU0 cpu_capacity=38300 (raw).
> > [    2.163699] init_cpu_capacity_cppc: CPU1 cpu_capacity=38300 (raw).
> > [    2.169899] init_cpu_capacity_cppc: CPU2 cpu_capacity=38300 (raw).
> > [    2.176098] init_cpu_capacity_cppc: CPU3 cpu_capacity=38300 (raw).
> > [    2.182296] init_cpu_capacity_cppc: CPU4 cpu_capacity=102400 (raw).
> > [    2.188581] init_cpu_capacity_cppc: CPU5 cpu_capacity=102400 (raw).
> > [    2.194867] cpu_capacity: capacity_scale=102400
> > [    2.199409] cpu_capacity: CPU0 cpu_capacity=383
> > [    2.203952] cpu_capacity: CPU1 cpu_capacity=383
> > [    2.208495] cpu_capacity: CPU2 cpu_capacity=383
> > [    2.213037] cpu_capacity: CPU3 cpu_capacity=383
> > [    2.217580] cpu_capacity: CPU4 cpu_capacity=1024
> > [    2.222209] cpu_capacity: CPU5 cpu_capacity=1024
> > [    2.226886] init_cpu_capacity_cppc: cpu_capacity initialization done
> >
> > root@...ntu:~# tail -n +1 /sys/devices/system/cpu/cpu*/cpu_capacity
> > ==> /sys/devices/system/cpu/cpu0/cpu_capacity <==
> > 383
> > ==> /sys/devices/system/cpu/cpu1/cpu_capacity <==
> > 383
> > ==> /sys/devices/system/cpu/cpu2/cpu_capacity <==
> > 383
> > ==> /sys/devices/system/cpu/cpu3/cpu_capacity <==
> > 383
> > ==> /sys/devices/system/cpu/cpu4/cpu_capacity <==
> > 1024
> > ==> /sys/devices/system/cpu/cpu5/cpu_capacity <==
> > 1024
> >
> > All works as expected even if ACPI processor support is built as a
> > module.
> >
> 
> Tested on my Ampere eMAG; this all seems to work fine except for some
> scheduler debug stuff that gets confused; see
> 
>   http://lore.kernel.org/r/20210518130725.3563132-1-valentin.schneider@arm.com
> 
> With that in mind:
> Tested-by: Valentin Schneider <valentin.schneider@....com>

Many thanks for testing and fixing the debugfs problem. I'll take a look
over your patch.

Ionela.