Patched Linux 5.11 Continues Looking Great For AMD Ryzen/EPYC Performance
Written by Michael Larabel in Software on 25 January 2021. Page 1 of 10. 12 Comments

While the initial AMD Linux 5.11 performance regression written about at the end of last year was of much concern given the performance hits to AMD Zen 2 / Zen 3 processors with the out-of-the-box "Schedutil" governor, with a pending patch the regression is not only addressed but in various workloads we continue seeing better performance than even compared to Linux 5.10. Here is the latest from several more days of extensive performance testing.

As noted last week, a fix has been proposed for that sizable performance regression affecting many workloads stemming from the introduction of AMD CPU frequency invariance support for Zen 2 and newer processors on Linux with the 5.11 kernel. That frequency invariance support is used with the CPUFreq Schedutil governor that on recent kernels is the default for AMD CPUs unless those users/vendors opting instead for the performance governor or another frequency scaling governor.

Last week I posted some patched benchmark results for the AMD EPYC 7702 and Ryzen 9 5950X while through the weekend I have continued with many more benchmarks on more hardware looking at the impact of this patch. That patch (x86,sched: On AMD EPYC set freq_max = max_boost in schedutil invariant formula) hasn't yet been mainlined but given it addresses a very clear performance regression on Linux 5.11, it will hopefully make its way to Linus Torvalds in the coming days.

In today's article are results looking at the performance impact on an AMD Renoir laptop (Ryzen 5 4500U) given users have been curious how well this patch helps "smaller" AMD systems. There are also more benchmarks from the Ryzen 9 5950X. Additionally are also benchmarks on an AMD EPYC 7F72 2P server looking at the performance as well as there looking at the CPU power consumption impact via the AMD_Energy driver.


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