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

From: Valentin Schneider <[email-masked]>
Date: Tue, 18 May 2021 14:12:03 +0100

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@ubuntu:~# 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@ubuntu:~# 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/[email-masked]

With that in mind:
Tested-by: Valentin Schneider <[email-masked]>

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