Ryzen 9 7950X Performance With The New AMD P-State Default Of Linux 6.5

Written by Michael Larabel in Software on 24 August 2023. Page 1 of 4. 20 Comments

The Linux 6.5 kernel is expected to be released as stable this weekend barring any last minute issues from being raised. One of the notable changes with this new kernel version is Linux now defaulting to the AMD P-State "EPP" active driver configuration for modern Ryzen systems rather than the long-used generic ACPI CPUFreq driver default. In some cases this can mean better performance but particularly should yield a nice improvement to the power efficiency of Ryzen Zen 2 and newer platforms, especially laptops and other portable Linux systems like the Steam Deck and ROG Ally. I am working on some fresh AMD Ryzen Linux laptop comparison benchmarks but for this article is a look at Linux 6.5 on the desktop side with the AMD Ryzen 9 7950X.

AMD P-State on Ryzen 9 7950X

The purposes of today's testing is quite simple and is looking at the out-of-the-box change when going from Linux 6.4 (the v6.4.11 point release as the latest and carries the same CPU security mitigations as found in 6.5/Git) against Linux 6.5 Git. Out-of-the-box like on Ubuntu Linux with a standard kernel build it means going from ACPI CPUFreq Schedutil as has been the default on v6.4 and prior kernels to now defaulting to AMD P-State with the EPP/active mode with the powersave governor.

On the same AMD Ryzen 9 7950X desktop, various benchmarks were carried out on Linux 6.4.11 and then repeated on Linux 6.5 Git as of this week to look for any performance changes with the most prominent change this cycle for AMD Linux customers being that P-State default migration. AMD EPYC server platforms though aren't yet defaulting to AMD P-State.

Linux 6.5 AMD Ryzen 9 7950X

For easy reproducibility by anyone, both the Linux 6.4 and 6.5 Git x86_64 kernels were obtained from the Ubuntu Mainline Kernel PPA.

Again I'll have some laptop benchmarks soon and a broader comparison looking at the different CPU frequency scaling driver/governor combinations as well: such detailed benchmark combinations have been looked at with prior kernel versions in Ryzen Mobile Power/Performance With Linux 6.3's New AMD P-State EPP Driver and AMD P-State EPP Performance With EPYC On Linux 6.3. Besides looking at the raw performance result, the CPU power consumption and performance-per-Watt impact was also looked at using the exposed PowerCap/RAPL sysfs data.

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