After A Bumpy Cycle, AMD Performance Will Shine Brighter On Linux 5.11
For those following the saga of the AMD frequency invariance regression on Linux 5.11 since the Christmas investigative benchmarking looking at the performance regressions, everything now looks like it will be buttoned up in time for the Linux 5.11 stable release. As noted yesterday, there was a curve ball this week in that the patch proposed by SUSE's Giovanni Gherdovich in January to address the frequency invariance regression was turned down by the Linux power management maintainer and instead he (Rafael Wysocki of Intel) proposed an alternative patch that instead modified the CPUFreq driver. Given it's getting late into the cycle, it's been a mad rush of re-conducting benchmarks on this new kernel patch and now it looks like that solution will be sent in the coming days for Linux 5.11.
Since noting the change in direction yesterday with the new CPUFreq patch series to replace the prior patch, the rest of my benchmarks have been coming in positively. It's looking good and addresses the performance regression in full noted at the end of December. SUSE's Giovanni Gherdovich who worked on the AMD frequency invariance support also confirmed that in his testing the performance is indeed recovered.
Rafael confirmed this morning that the CPUfreq patches will be sent in as "a post-RC7 late push." Linux 5.11-rc7 is due out on Sunday and it looks like he will wait until after that to send in this CPUFreq change. Depending upon how the timing plays out next week, Linux 5.11 final could be officially released as stable a week from this Sunday unless Linus Torvalds decides for issuing a 5.11-rc8.
While it's coming in as quite a late change for a regression introduced during the Linux 5.11 merge window, the numbers are looking very good and I haven't encountered any fallout from the patched CPUFreq in my constant testing of the new series.
In extreme cases, the Linux 5.11 performance has been heavily regressed on AMD Zen 2 / Zen 3 systems up to this point... Fortunately, the patched CPUFreq addresses this big issue... The benchmarks shown here from a Ryzen 5 4500U notebook.
But it's not just addressing the regression as in some workloads the CPUFreq patched performance is now well in front of even Linux 5.10 stable while using the same CPUFreq governor. (System details and more Ryzen 5 4500U benchmarks over on OpenBenchmarking.org).
In this article are some more benchmarks conducted this week on different AMD systems in confirming the Linux 5.11 performance outlook.