An Early Look At The AMD P-State CPPC Driver Performance vs. ACPI CPUFreq
Written by Michael Larabel in Software on 22 September 2021. Page 6 of 6. 25 Comments

Wondering if the AMD P-State ondemand/schedutil poor showing was due to the high-end Ryzen 9 5950X processor or other system/BIOS issue around ACPI CPPC, I also turned to running some tests on an AMD Ryzen 9 5900HX ASUS notebook.

There were some regressions on this AMD Zen 3 notebook too but tended to not be as bad as bad as the Ryzen 9 5950X system.

But it also didn't lead to any measurable improvement in power efficiency either for this ASUS notebook.

I've seen similar results on other AMD Zen 3 systems tried so far of either being largely comparable to ACPI CPUFreq or in some workloads having a negative performance impact but where the power savings didn't offset the difference to actually yield better power efficiency. Granted, this AMD P-State driver is still in the early stages and it's possible there could be some quirks and other issues to deal with given AMD hasn't been supporting ACPI CPPC usage on Linux, but we'll see in the weeks ahead. When trying Zen 3 desktop APUs for instance the driver currently didn't work and similarly AMD doesn't yet support Zen 2 hardware with this new driver. In any case as the amd_pstate Linux driver matures I'll be back around with plenty more benchmarks and remain hopeful that in the end this will be a nice improvement for the AMD Linux ecosystem.

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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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