Updated Patches For AMD "Fast CPPC" To Yield Higher Performance At Same Power Level

One of the patch series that sadly was not ready in time for the Linux 6.10 merge window and thus will need to wait a few months for at least the next kernel is enabling AMD Fast CPPC support for Zen 4 processors. Fast CPPC aims to allow the processor to deliver higher performance at the same power consumption.

Earlier this year I wrote about AMD's work on enabling Fast CPPC for Linux as a feature new to existing Zen 4 processors. The AMD P-State CPU frequency scaling driver makes use of the ACPI Collaborative Processor Performance Control (CPPC) data for describing performance scales and attributes on a per-CPU basis and in turn the kernel requesting desired performance levels. With some AMD processors beginning with current Zen 4 models, there is the notion of "fast CPPC". The Fast CPPC feature when indicated by a CPU bit allows for a faster CPPC loop thanks to architectural enhancements. In turn leveraging AMD Fast CPPC can make for higher performance at the same power level.

Posted this weekend were the AMD Fast CPPC v4 patches now out for kernel review. The patch series simply sums it up as:

"Some AMD Zen 4 processors support a new feature FAST CPPC which allows for a faster CPPC loop due to internal architectural enhancements. The goal of this faster loop is higher performance at the same power consumption."

The patches when tested on an AMD Ryzen 7 7840HS have pointed to Fast CPPC allowing 0~2% better performance while the performance-per-Watt can see as much as a ~6% benefit.

Here's to hoping this AMD Fast CPPC support for the AMD P-State driver will be ready in time for the Linux 6.11 kernel later in the summer. AMD Core Performance Boost support is another feature also still undergoing review for the AMD P-State Linux driver.