Linux 5.11 Is Regressing Hard For AMD Performance With Schedutil
Written by Michael Larabel in Software on 25 December 2020. Page 2 of 6. 32 Comments

First up is a look at the CPUFreq performance and schedutil governors across Linux 5.10 and 5.11 Git for an AMD EPYC 7702 1P setup.

For many workloads, the performance is unchanged from Linux 5.10 to 5.11 for either governor...

But for some like Intel's OSPray ray-tracing engine, moving to Linux 5.11 yields a measurable performance loss. Yes, OSPray doesn't involve much I/O or kernel interactions for that matter that led my initial thinking was due to the frequency invariance with Schedutil. Now with the "performance" governor run, we see this to be the case. The performance governor led to unchanged results from Linux 5.10 to 5.11 while the Schedutil governor sees the big drop in performance.

With the x265 video encoding workload is another case of seeing Linux 5.11 with Schedutil lead to a measurable and reproducible reduction in performance while under the performance governor it actually improved slightly on Linux 5.11.

Intel's Open Image Denoise denoising library that is part of their oneAPI rendering toolkit saw a big drop to performance with Linux 5.11 under Schedutil while the performance governor saw no change in performance.

The CPU power consumption of the EPYC 7702 was lower with Linux 5.11 Schedutil but on a performance-per-Watt basis was behind the Linux 5.10 efficiency.

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