The AMD Heterogeneous core design and Hardware Feedback Interface (HFI)
provide behavioral classification and a dynamically updated ranking table
for the scheduler to use when choosing cores for tasks.
Threads are classified during runtime into enumerated classes.
Currently, the driver supports 3 classes (0 through 2). These classes
represent thread performance/power characteristics that may benefit from
special scheduling behaviors. The real-time thread classification is
consumed by the operating system and is used to inform the scheduler of
where the thread should be placed for optimal performance or energy efficiency.
The thread classification helps to select CPU from a ranking table that describes
an efficiency and performance ranking for each classification from two dimensions.
The ranking data provided by the ranking table are numbers ranging from 0 to 255,
where a higher performance value indicates higher performance capability and a higher
efficiency value indicates greater efficiency. All the CPU cores are ranked into
different class IDs. Within each class ranking, the cores may have different ranking
values. Therefore, picking from each classification ID will later allow the scheduler
to select the best core while threads are classified into the specified workload class.
This series was originally submitted by Perry Yuan [1] but he is now doing a different
role and he asked me to take over.
Link: https://lore.kernel.org/all/cover.1724748733.git.perry.yuan@amd.com/
On applicable hardware this series has between a 2% and 5% improvement across various
benchmarks.
There is however a cost associated with clearing history on the process context switch.
On average it increases the delay by 119ns, and also has a wider range in delays
(the standard deviation is 25% greater).
Although this series most prominently has changes to platform-x86 it is based
off of tip x86/cpu due to changes queued up for 6.13-rc1 that are dependencies.
v4->v5:
* Pick up tags
* Modify where setup_hreset() is called
Mario Limonciello (4):
MAINTAINERS: Add maintainer entry for AMD Hardware Feedback Driver
cpufreq/amd-pstate: Disable preferred cores on designs with workload
classification
platform/x86/amd: hfi: Set ITMT priority from ranking data
platform/x86/amd: hfi: Add debugfs support
Perry Yuan (9):
Documentation: x86: Add AMD Hardware Feedback Interface documentation
x86/cpufeatures: add X86_FEATURE_AMD_WORKLOAD_CLASS feature bit
x86/msr-index: define AMD heterogeneous CPU related MSR
platform/x86: hfi: Introduce AMD Hardware Feedback Interface Driver
platform/x86: hfi: parse CPU core ranking data from shared memory
platform/x86: hfi: init per-cpu scores for each class
platform/x86: hfi: add online and offline callback support
platform/x86: hfi: add power management callback
x86/process: Clear hardware feedback history for AMD processors
Documentation/arch/x86/amd-hfi.rst | 129 ++++++
Documentation/arch/x86/index.rst | 1 +
MAINTAINERS | 9 +
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/hreset.h | 6 +
arch/x86/include/asm/msr-index.h | 5 +
arch/x86/kernel/cpu/common.c | 15 +
arch/x86/kernel/cpu/scattered.c | 1 +
arch/x86/kernel/process_32.c | 3 +
arch/x86/kernel/process_64.c | 3 +
drivers/cpufreq/amd-pstate.c | 6 +
drivers/platform/x86/amd/Kconfig | 1 +
drivers/platform/x86/amd/Makefile | 1 +
drivers/platform/x86/amd/hfi/Kconfig | 21 +
drivers/platform/x86/amd/hfi/Makefile | 7 +
drivers/platform/x86/amd/hfi/hfi.c | 547 ++++++++++++++++++++++++++
16 files changed, 756 insertions(+)
create mode 100644 Documentation/arch/x86/amd-hfi.rst
create mode 100644 arch/x86/include/asm/hreset.h
create mode 100644 drivers/platform/x86/amd/hfi/Kconfig
create mode 100644 drivers/platform/x86/amd/hfi/Makefile
create mode 100644 drivers/platform/x86/amd/hfi/hfi.c
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2.43.0