Spectre Mitigation Performance Impact Benchmarks On AMD Ryzen 3700X / 3900X Against Intel

The socket activity test is another example of the Zen 2 CPUs appearing to take a greater hit from the mitigations than Zen 1. The Ryzen 7 2700X saw a 5% hit to the socket performance with the out-of-the-box mitigations while the Ryzen 7 3700X was at 11%, but at least it still came out faster than its predecessor.

The ctx_clock micro-benchmark for measuring out the time to perform a context switch shows roughly the same performance between Zen+ and Zen 2.

In browser tests, the Core i9 9900K mitigation hit was around 15% to the Ryzen 9 3900X at 11% or the Ryzen 7 2700X at 9%.

If looking at the geometric mean for these various mitigation-sensitive benchmarks, the default mitigations on the Core i9 9900K amounted to a 28% hit while the Ryzen 7 2700X saw a 5% hit with its default Spectre mitigations and the new Ryzen 7 3700X came in at 6% and the Ryzen 9 3900X at just over 5%. Keep in mind these benchmarks ran for this article were a good portion of synthetic tests and focused on workloads affected by Spectre/Meltdown/L1TF/Zombieload. Many of these particular tests aren't multi-threaded and that's why you don't see as much of a difference between these HEDT and desktop CPUs as in our more normal benchmarks.

We'll update if hearing back from AMD on whether any software mitigation changes are expected for AMD Zen 2 processors given their hardware mitigations or if they still recommend these same conservative defaults as it currently stands in the Linux 5.2 kernel.