AMD P-State EPP Patches Spun An 8th Time For Helping Out Linux Performance & Efficiency

AMD kicked off Christmas week by posting an eighth version of their P-State EPP driver patches for implementing the AMD Energy Performance Preference handling within their recent processors/SoCs for software to hint a performance or energy efficiency hint. P-State EPP can address some of the shortcomings with AMD's original P-State driver implementation merged nearly a year ago and has been showing good results in numbers posted by AMD engineers.

Over the past year and few months AMD Linux engineers have been working a lot on the AMD P-State driver code for a proper CPU frequency scaling driver for Zen 2 and newer hardware that supports ACPI CPPC. AMD P-State aims to deliver better performance and power efficiency than the generic ACPI CPUFreq driver used on AMD processors to this point.

Benchmark numbers by AMD show P-State EPP addressing some of the gaps with the initial P-State driver.

The AMD P-State driver that premiered in Linux 5.17 showed at times to have some performance regressions compared to ACPI CPUFreq but the P-State EPP functionality will hopefully clear that up. AMD engineers also recently started working on a P-State Guided Autonomous Mode too.

AMD P-State EPP sadly isn't ready for Linux 6.2 but that delay allowed time for a v8 patch-set to be published. This morning's AMD P-State EPP v8 patches make various low-level code changes, address other upstream review feedback, remove the I/O wait boost code, and other small changes. Nothing too dramatic and from the sounds of prior LKML discussions, it sounds like the AMD P-State EPP code will likely soon be picked up by the power management subsystem's "for-next" branch for additional exposure ahead of the Linux 6.3 cycle.

Once this AMD P-State EPP code settles down ahead of mainline I'll be around with some benchmarks for this CPU frequency scaling driver on AMD Ryzen desktops/laptops and EPYC server platforms.