[AMD Official Use Only - General]
-----Original Message----- From: Meng, Li (Jassmine) Li.Meng@amd.com Sent: Wednesday, November 29, 2023 2:55 PM To: Rafael J . Wysocki rafael.j.wysocki@intel.com; Huang, Ray Ray.Huang@amd.com Cc: linux-pm@vger.kernel.org; linux-kernel@vger.kernel.org; x86@kernel.org; linux-acpi@vger.kernel.org; Shuah Khan skhan@linuxfoundation.org; linux- kselftest@vger.kernel.org; Fontenot, Nathan Nathan.Fontenot@amd.com; Sharma, Deepak Deepak.Sharma@amd.com; Deucher, Alexander Alexander.Deucher@amd.com; Limonciello, Mario Mario.Limonciello@amd.com; Huang, Shimmer Shimmer.Huang@amd.com; Yuan, Perry Perry.Yuan@amd.com; Du, Xiaojian Xiaojian.Du@amd.com; Viresh Kumar viresh.kumar@linaro.org; Borislav Petkov bp@alien8.de; Oleksandr Natalenko oleksandr@natalenko.name; Meng, Li (Jassmine) Li.Meng@amd.com; Karny, Wyes Wyes.Karny@amd.com Subject: [PATCH V11 6/7] Documentation: amd-pstate: introduce amd-pstate preferred core
Introduce amd-pstate preferred core.
check preferred core state set by the kernel parameter: $ cat /sys/devices/system/cpu/amd-pstate/prefcore
Tested-by: Oleksandr Natalenko oleksandr@natalenko.name Reviewed-by: Wyes Karny wyes.karny@amd.com Reviewed-by: Mario Limonciello mario.limonciello@amd.com Reviewed-by: Huang Rui ray.huang@amd.com Signed-off-by: Meng Li li.meng@amd.com
Documentation/admin-guide/pm/amd-pstate.rst | 59 ++++++++++++++++++++- 1 file changed, 57 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst index 1cf40f69278c..0b832ff529db 100644 --- a/Documentation/admin-guide/pm/amd-pstate.rst +++ b/Documentation/admin-guide/pm/amd-pstate.rst @@ -300,8 +300,8 @@ platforms. The AMD P-States mechanism is the more performance and energy efficiency frequency management method on AMD processors.
-AMD Pstate Driver Operation Modes
+``amd-pstate`` Driver Operation Modes +======================================
``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode, non-autonomous (passive) mode and guided autonomous (guided) mode. @@ -353,6 +353,48 @@ 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 enables the scheduler to prefer +scheduling on cores that can achieve a higher frequency with lower +voltage. The preferred core rankings can dynamically change based on +the workload, platform conditions, thermals and ageing.
+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-pstate`` Preferred Core Switch +================================= +Kernel Parameters +-----------------
+``amd-pstate`` peferred core`` has two states: enable and disable. +Enable/disable states can be chosen by different kernel parameters. +Default enable ``amd-pstate`` preferred core.
+``amd_prefcore=disable``
+For systems that support ``amd-pstate`` preferred core, the core +rankings will always be advertised by the platform. But OS can choose +to ignore that via the kernel parameter ``amd_prefcore=disable``.
User Space Interface in ``sysfs`` - General
@@ -385,6 +427,19 @@ 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``
Preferred core state of the driver: "enabled" or "disabled"."enabled"Enable the ``amd-pstate`` preferred core."disabled"Disable the ``amd-pstate`` preferred coreThis attribute is read-only to check the state of preferred core setby the kernel parameter.``cpupower`` tool support for ``amd-pstate``
-- 2.34.1
Reviewed-by: Perry Yuan < perry.yuan@amd.com>