The Spectre Mitigation Performance Impact On AMD Ryzen 5000 "Zen 3" Processors
Written by Michael Larabel in Processors on 2 December 2020. Page 6 of 6. 8 Comments

When taking the geometric mean of all these benchmarks conducted, disabling mitigations on the Ryzen 5 5600X improved the performance by about 6.8% for these workloads affected by the ongoing Spectre mitigations. Meanwhile for the Ryzen 5 3600XT when booting with mitigations=off there was just a 4% difference -- likely due to the STIBP handing difference plus any other architectural changes in the name of improving security.

In any case with these tests going from the Ryzen 5 3600XT to Ryzen 5 5600X on this system yielded a 24.5% uplift in performance. If you are one to not believe in the relevance or severity of Spectre and boot your system with "mitigations=off" or otherwise running your hardware in an environment of only trusted code execution, comparing the unmitigated performance from the 3600XT to 5600X is a 28% generational improvement. We'll see though if a future CPU microcode update ends up making the STIBP handling conditional based on task, which would mean even better out-of-the-box performance, or if AMD is keeping it always-on as a precaution for better security.

The latest public STIBP guidance I've seen from AMD is this documentation. For CPUs indicating the STIBP always-on mode, they recommend it "always on" to reduce the performance impact of the WRMSR at necessary toggle points. But that same undated document also states AMD is not recommending STIBP currently as a performant mitigtion in Windows and Linux for Spectre V2.

In any case, the Zen 3 CPU performance continues to be terrific - those wanting to compare their own system's performance against the results in this article can be carried out in a fully-automated, side-by-side manner by installing the Phoronix Test Suite and running phoronix-test-suite benchmark 2012011-HA-AMDRYZENM28. Regardless of if you run your system at the mitigated defaults or prefer running your system with mitigations disabled, the performance to find with the Ryzen 5000 series is incredible.

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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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