| Message ID | 20230808081001.2215240-6-li.meng@amd.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | AMD Pstate Preferred Core | expand |
On 8/8/2023 03:10, Meng Li wrote: > Introduce AMD Pstate Preferred Core. > > check preferred core state: > $ cat /sys/devices/system/cpu/amd-pstate/prefcore_state > > Signed-off-by: Meng Li <li.meng@amd.com> > --- > Documentation/admin-guide/pm/amd-pstate.rst | 55 +++++++++++++++++++++ > 1 file changed, 55 insertions(+) > > diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst > index 1cf40f69278c..4a30cf235425 100644 > --- a/Documentation/admin-guide/pm/amd-pstate.rst > +++ b/Documentation/admin-guide/pm/amd-pstate.rst > @@ -353,6 +353,49 @@ is activated. In this mode, driver requests minimum and maximum performance > level and the platform autonomously selects a performance level in this range > and appropriate to the current workload. > > +AMD Pstate Preferred Core > +================================= > + > +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. > + > +``AMD Pstate Preferred Core`` use ITMT arch provides functions and data structures > +for enabling the scheduler to favor scheduling on cores can be get a higher frequency > +with lower voltage under preferred core. This sentence was useful for the commit message, but I don't think it should be in the user facing documentation. > And it has the ability to dynamically > +change the preferred core based on the workload and platform conditions and > +accounting for thermals and aging. > + > +The priority metric will be initialized by the AMD Pstate driver. The AMD Pstate > +driver will also determine whether or not ``AMD Pstate Preferred Core`` is > +supported by the platform. > + > +AMD Pstate driver will provide an initial core ordering when the system boots. > +The platform uses the CPPC interfaces 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 and set the cpu's priority. > + > +AMD Preferred Core Switch > +================================= > +Kernel Parameters > +----------------- > + > +``AMD Pstate Preferred Core`` has two states: enable and disable. > +Enable/disable states can be chosen by different kernel parameters. > +Default disable ``AMD Pstate Preferred Core``. Why default disable? > + > +``amd_prefcore=enable`` > + > +If ``amd_prefcore=enable`` is passed to kernel command line option > +then enable ``AMD Pstate Preferred Core`` if the processor and power > +firmware can support preferred core feature. This can be simplified as "platform can support the preferred core feature". > + > User Space Interface in ``sysfs`` - General > =========================================== > > @@ -385,6 +428,18 @@ control its functionality at the system level. They are located in the > to the operation mode represented by that string - or to be > unregistered in the "disable" case. > > +``prefcore_state`` > + Preferred Core state of the driver: "enabled" or "disabled". > + > + "enabled" > + Enable the AMD Preferred Core. > + > + "disabled" > + Disable the AMD Preferred Core > + > + > + This attribute is read-only to check the state of Preferred Core. As the attribute is read only and won't change at runtime, I don't think it makes sense to include the word "state" in the sysfs file name. You can just rename it to "prefcore". > + > ``cpupower`` tool support for ``amd-pstate`` > =============================================== >
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 1cf40f69278c..4a30cf235425 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -353,6 +353,49 @@ is activated. In this mode, driver requests minimum and maximum performance level and the platform autonomously selects a performance level in this range and appropriate to the current workload. +AMD Pstate Preferred Core +================================= + +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. + +``AMD Pstate Preferred Core`` use ITMT arch provides functions and data structures +for enabling the scheduler to favor scheduling on cores can be get a higher frequency +with lower voltage under preferred core. And it has the ability to dynamically +change the preferred core based on the workload and platform conditions and +accounting for thermals and aging. + +The priority metric will be initialized by the AMD Pstate driver. The AMD Pstate +driver will also determine whether or not ``AMD Pstate Preferred Core`` is +supported by the platform. + +AMD Pstate driver will provide an initial core ordering when the system boots. +The platform uses the CPPC interfaces 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 and set the cpu's priority. + +AMD Preferred Core Switch +================================= +Kernel Parameters +----------------- + +``AMD Pstate Preferred Core`` has two states: enable and disable. +Enable/disable states can be chosen by different kernel parameters. +Default disable ``AMD Pstate Preferred Core``. + +``amd_prefcore=enable`` + +If ``amd_prefcore=enable`` is passed to kernel command line option +then enable ``AMD Pstate Preferred Core`` if the processor and power +firmware can support preferred core feature. + User Space Interface in ``sysfs`` - General =========================================== @@ -385,6 +428,18 @@ control its functionality at the system level. They are located in the to the operation mode represented by that string - or to be unregistered in the "disable" case. +``prefcore_state`` + Preferred Core state of the driver: "enabled" or "disabled". + + "enabled" + Enable the AMD Preferred Core. + + "disabled" + Disable the AMD Preferred Core + + + This attribute is read-only to check the state of Preferred Core. + ``cpupower`` tool support for ``amd-pstate`` ===============================================
Introduce AMD Pstate Preferred Core. check preferred core state: $ cat /sys/devices/system/cpu/amd-pstate/prefcore_state Signed-off-by: Meng Li <li.meng@amd.com> --- Documentation/admin-guide/pm/amd-pstate.rst | 55 +++++++++++++++++++++ 1 file changed, 55 insertions(+)