Re: [PATCH V2 6/7] Documentation: amd-pstate: introduce AMD Pstate Preferred Core

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 8/15/2023 01:15, 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@xxxxxxx>
---
  Documentation/admin-guide/pm/amd-pstate.rst | 54 +++++++++++++++++++++
  1 file changed, 54 insertions(+)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 1cf40f69278c..ef2b69935311 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -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`` enable 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 enable ``AMD Pstate Preferred Core``.
+ > +``amd_prefcore=disable``
+
+If ``amd_prefcore=disable`` is passed to kernel command line option
+then disable ``AMD Pstate Preferred Core`` if platform can support
+the Preferred Core feature.
This all seems needlessly wordy.  Here's my suggestion.

"``AMD Pstate preferred core`` will be enabled if the underlying platform supports it. It can be disabled by kernel parameter:

``amd_prefcore=disable``

+
  User Space Interface in ``sysfs`` - General
  ===========================================
@@ -385,6 +427,18 @@ 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``
+	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``
  ===============================================




[Index of Archives]     [Linux IBM ACPI]     [Linux Power Management]     [Linux Kernel]     [Linux Laptop]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]
  Powered by Linux