AMD Posts 11th Iteration Of P-State Preferred Core Patches For Linux

For the past number of months AMD has been actively working on enabling AMD P-State Preferred Core functionality for Linux so that their modern processors can communicate "preferred" cores to the Linux kernel scheduler for making better decisions around task placement and ultimately ensuring best performance of Ryzen and EPYC processors running on Linux. This week they are up to their 11th take on these kernel patches.

As with the AMD P-State CPU frequency scaling driver, P-State Preferred Core functionality also depends upon ACPI CPPC information from the platform for making wiser decisions to maximize performance and power efficiency.

Earlier implementations of amd-pstate preferred core only support a static core ranking and targeted performance. Now it has the ability to dynamically change the preferred core based on the workload and platform conditions and accounting for thermals and aging.

Amd-pstate driver utilizes the functions and data structures provided by the ITMT architecture to enable the scheduler to favor scheduling on cores which can be get a higher frequency with lower voltage. We call it amd-pstate preferred core.
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Amd-pstate driver will provide an initial core ordering at boot time. It relies on the CPPC interface 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.

With AMD P-State Preferred Core already supported on Windows, hopefully the Linux support will get merged soon and work its way into H1'2024 Linux distributions. The new v11 patches this week have just minor changes over the prior revision.

Here's to hoping the work could be ironed out in time for the upcoming Linux 6.8 merge window.