RE: [PATCH V8 0/7] amd-pstate preferred core

[Meng, Li (Jassmine)]

[AMD Official Use Only - General]

Hi Oleksandr:

> -----Original Message-----
> From: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
> Sent: Monday, October 9, 2023 2:55 PM
> To: Rafael J . Wysocki <rafael.j.wysocki@xxxxxxxxx>; Huang, Ray
> <Ray.Huang@xxxxxxx>; Meng, Li (Jassmine) <Li.Meng@xxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; Shuah Khan
> <skhan@xxxxxxxxxxxxxxxxxxx>; linux-kselftest@xxxxxxxxxxxxxxx; Fontenot,
> Nathan <Nathan.Fontenot@xxxxxxx>; Sharma, Deepak
> <Deepak.Sharma@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>; Limonciello, Mario
> <Mario.Limonciello@xxxxxxx>; Huang, Shimmer
> <Shimmer.Huang@xxxxxxx>; Yuan, Perry <Perry.Yuan@xxxxxxx>; Du,
> Xiaojian <Xiaojian.Du@xxxxxxx>; Viresh Kumar <viresh.kumar@xxxxxxxxxx>;
> Borislav Petkov <bp@xxxxxxxxx>; Meng, Li (Jassmine) <Li.Meng@xxxxxxx>
> Subject: Re: [PATCH V8 0/7] amd-pstate preferred core
>
> Hello.
>
> On pondělí 9. října 2023 4:49:25 CEST 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 preferred 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 V7->V8:
> > - all:
> > - - pick up Review-By flag added by Mario and Ray.
> > - cpufreq: amd-pstate:
> > - - use hw_prefcore embeds into cpudata structure.
> > - - delete preferred core init from cpu online/off.
>
> Could you please let me know if this change means a fix for the report I've
> sent previously? [1]
>
[Meng, Li (Jassmine)] Yes.
I have deleted online handle function of amd pstate driver.
It doesn't re-initialize preferred core.
This online function will set incorrect des perf value.

> Would you also be able to Cc me on the next iteration of this patchset?
[Meng, Li (Jassmine)] OK.
>
> Thank you!
>
> [1] https://lore.kernel.org/lkml/5973628.lOV4Wx5bFT@xxxxxxxxxxxxxx/
>
> >
> > Changes form V6->V7:
> > - x86:
> > - - Modify kconfig about X86_AMD_PSTATE.
> > - cpufreq: amd-pstate:
> > - - modify incorrect comments about scheduler_work().
> > - - convert highest_perf data type.
> > - - modify preferred core init when cpu init and online.
> > - acpi: cppc:
> > - - modify link of CPPC highest performance.
> > - cpufreq:
> > - - modify link of CPPC highest performance changed.
> >
> > Changes form V5->V6:
> > - cpufreq: amd-pstate:
> > - - modify the wrong tag order.
> > - - modify warning about hw_prefcore sysfs attribute.
> > - - delete duplicate comments.
> > - - modify the variable name cppc_highest_perf to prefcore_ranking.
> > - - modify judgment conditions for setting highest_perf.
> > - - modify sysfs attribute for CPPC highest perf to pr_debug message.
> > - Documentation: amd-pstate:
> > - - modify warning: title underline too short.
> >
> > Changes form V4->V5:
> > - cpufreq: amd-pstate:
> > - - modify sysfs attribute for CPPC highest perf.
> > - - modify warning about comments
> > - - rebase linux-next
> > - cpufreq:
> > - - Moidfy warning about function declarations.
> > - Documentation: amd-pstate:
> > - - align with ``amd-pstat``
> >
> > Changes form V3->V4:
> > - Documentation: amd-pstate:
> > - - Modify inappropriate descriptions.
> >
> > 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   |  59 +++++-
> >  arch/x86/Kconfig                              |   5 +-
> >  drivers/acpi/cppc_acpi.c                      |  13 ++
> >  drivers/acpi/processor_driver.c               |   6 +
> >  drivers/cpufreq/amd-pstate.c                  | 186 ++++++++++++++++--
> >  drivers/cpufreq/cpufreq.c                     |  13 ++
> >  include/acpi/cppc_acpi.h                      |   5 +
> >  include/linux/amd-pstate.h                    |  10 +
> >  include/linux/cpufreq.h                       |   5 +
> >  10 files changed, 285 insertions(+), 22 deletions(-)
> >
> >
>
>
> --
> Oleksandr Natalenko (post-factum)