Re: [PATCH V7 0/7] amd-pstate preferred core

[Shuah]

On 9/18/23 11:44, Shuah Khan wrote:
> On 9/18/23 02:14, 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 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.
>
> This series in now in linux-kselftest next branch for Linux 6.7-rc1.
>
> If there are any changes and/or fixes, please send patches on top of
> linux-kselftest next branch.

Sorry for the mix-up. Wrong series - my bad. This series isn't
in linux-kselftest next.

thanks,
-- Shuah