linux-kernel - Re: [PATCH V3 0/7] AMD Pstate Preferred Core

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Message-ID: <597bea76-b638-4ed2-9238-9b0518d379b2@amd.com>
Date:   Wed, 23 Aug 2023 21:23:39 -0500
From:   Mario Limonciello <mario.limonciello@....com>
To:     Meng Li <li.meng@....com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Huang Rui <ray.huang@....com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-acpi@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>,
        linux-kselftest@...r.kernel.org,
        Nathan Fontenot <nathan.fontenot@....com>,
        Deepak Sharma <deepak.sharma@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Shimmer Huang <shimmer.huang@....com>,
        Perry Yuan <Perry.Yuan@....com>,
        Xiaojian Du <Xiaojian.Du@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH V3 0/7] AMD Pstate Preferred Core

On 8/23/2023 21:12, Meng Li wrote:
> Hi all:
> 
> The core frequency is subjected to the process variation in semiconductors.
> Not all cores are able to reach the maximum frequency respecting the
> infrastructure limits. Consequently, AMD has redefined the concept of
> maximum frequency of a part. This means that a fraction of cores can reach
> maximum frequency. To find the best process scheduling policy for a given
> scenario, OS needs to know the core ordering informed by the platform through
> highest performance capability register of the CPPC interface.
> 
> Earlier implementations of AMD Pstate Preferred Core only support a static
> core ranking and targeted performance. Now it has the ability to dynamically
> change the preferred core based on the workload and platform conditions and
> accounting for thermals and aging.
> 
> AMD Pstate driver utilizes the functions and data structures provided by
> the ITMT architecture to enable the scheduler to favor scheduling on cores
> which can be get a higher frequency with lower voltage.
> We call it AMD Pstate Preferrred Core.
> 
> Here sched_set_itmt_core_prio() is called to set priorities and
> sched_set_itmt_support() is called to enable ITMT feature.
> AMD Pstate driver uses the highest performance value to indicate
> the priority of CPU. The higher value has a higher priority.
> 
> AMD Pstate driver will provide an initial core ordering at boot time.
> It relies on the CPPC interface to communicate the core ranking to the
> operating system and scheduler to make sure that OS is choosing the cores
> with highest performance firstly for scheduling the process. When AMD Pstate
> driver receives a message with the highest performance change, it will
> update the core ranking.
> 
> Changes form V2->V3:
> - x86:
> - - Modify kconfig and description.
> - cpufreq: amd-pstate:
> - - Add Co-developed-by tag in commit message.
> - cpufreq:
> - - Modify commit message.
> - Documentation: amd-pstate:
> - - Modify inappropriate descriptions.
> 
> Changes form V1->V2:
> - acpi: cppc:
> - - Add reference link.
> - cpufreq:
> - - Moidfy link error.
> - cpufreq: amd-pstate:
> - - Init the priorities of all online CPUs
> - - Use a single variable to represent the status of Preferred Core.
> - Documentation:
> - - Default enabled preferred core.
> - Documentation: amd-pstate:
> - - Modify inappropriate descriptions.
> - - Default enabled preferred core.
> - - Use a single variable to represent the status of Preferred Core.
> 
> Meng Li (7):
>    x86: Drop CPU_SUP_INTEL from SCHED_MC_PRIO for the expansion.
>    acpi: cppc: Add get the highest performance cppc control
>    cpufreq: amd-pstate: Enable AMD Pstate Preferred Core Supporting.
>    cpufreq: Add a notification message that the highest perf has changed
>    cpufreq: amd-pstate: Update AMD Pstate Preferred Core ranking
>      dynamically
>    Documentation: amd-pstate: introduce AMD Pstate Preferred Core
>    Documentation: introduce AMD Pstate Preferrd Core mode kernel command
>      line options
> 
>   .../admin-guide/kernel-parameters.txt         |   5 +
>   Documentation/admin-guide/pm/amd-pstate.rst   |  53 ++++++
>   arch/x86/Kconfig                              |   5 +-
>   drivers/acpi/cppc_acpi.c                      |  13 ++
>   drivers/acpi/processor_driver.c               |   6 +
>   drivers/cpufreq/amd-pstate.c                  | 152 ++++++++++++++++--
>   drivers/cpufreq/cpufreq.c                     |  13 ++
>   include/acpi/cppc_acpi.h                      |   5 +
>   include/linux/amd-pstate.h                    |   1 +
>   include/linux/cpufreq.h                       |   4 +
>   10 files changed, 239 insertions(+), 18 deletions(-)
> 
Reviewed-by: Mario Limonciello <mario.limonciello@....com>