A New CPU Frequency Control Mechanism on Linux

Explore a comprehensive conference talk on the new CPU frequency control mechanism for Linux, focusing on AMD processors. Delve into the evolution from ACPI-based CPU frequency drivers to the more power-efficient AMD P-State kernel CPUFreq driver introduced for Zen2 and later CPUs. Learn about the fine-grain frequency control using ACPI CPPC, its implementation in kernel 5.17, and subsequent additions in kernel 5.18. Discover the design, implementation, usage, existing issues, and future work planned for AMD CPU platforms. Gain insights into the frequency control algorithm in SMU firmware, CPPC performance capabilities, and various governors in the Linux kernel. Examine the AMD P-State core design, trace event implementation, tracer tool support, sysfs attributes, and unit test support. Compare performance benchmarks between AMD P-State and ACPI CPUFreq using TBench, Gitsource, and Speedometer tests.

Intro
Background
Legacy CPUFreq Design and Potential Conflict
New AMD CPUFreq Design Proposal
Frequency Control Algorithm in SMU Firmware
CPPC Performance Capability
CPPC Performance Control
Frequency Control Governors in Linux Kernel
Existing Firmware Component
Existing Kernel Component
New AMD P-State Core Design and Implementation (1)
AMD P-State Trace Event Design and Implementation
AMD P-State Tracer Tool Support
AMD P-State Sysfs Attributes Design and Implementation
AMD P-State Unit Test Support
RAPL Perf Support for AMD Processor
Performance Per Watt Calculation
TBench CPU Benchmark for AMD P-State vs ACPI CPUFreq
Gitsource CPU Benchmark for AMD P-State vs ACPI CPUFreq
Speedometer CPU Benchmark for AMD P-State vs ACPI CPUFreq