AMD Guided Autonomous Mode Submitted For Linux 6.4

As anticipated the AMD P-State driver extension building out the Guided Autonomous Mode of operation has been sent in as part of the CPU frequency scaling / power management changes for the in-development Linux 6.4 kernel.

AMD Linux engineers posted the Guided Autonomous Mode patches back in December and in the months since have been iterating on them so they are up to par for the mainline kernel. This mode of operation for the AMD P-State driver complements the original "passive" mode and the AMD P-State EPP mode added in Linux 6.3. The AMD Guided Autonomous Mode lets the operating system scaling governor specify the minimum and maximum frequencies / performance levels through special registers and then leaves it to the platform firmware to autonomously select an operating frequency within that specified range.

This AMD Guided Autonomous Mode should help AMD Ryzen and especially AMD EPYC servers improve the performance and power efficiency for cases where the platform firmware is able to make better CPU frequency scaling decisions.

Activating the AMD P-State Guided Autonomous Mode on newer AMD platforms can be done using the "amd_pstate=guided" kernel option beginning on Linux 6.4. I'll be running some benchmarks of these different AMD P-State modes soon.

The AMD P-State Guided Autonomous Mode support was sent in as part of the power management updates today for the Linux 6.4 merge window.

Also notable with the power management updates is the change to make the Intel P-State driver enable HWP I/O boost for all server platforms. This should help with slightly better performance for Ice Lake and Sapphire Rapids servers. More details on that change within this prior Phoronix article: Small I/O Performance Boost Coming For Intel Ice Lake & Sapphire Rapids Servers.

Linux power management maintainer Rafael Wysocki also sent out today the ACPI updates for Linux 6.4 as well as the thermal control updates.