Spectre Mitigation Performance Impact For Intel's Rocket Lake
The Firefox (and Chrome) web browser benchmarks showed the most significant difference from disabling these mitigations on Intel Rocket Lake. Firefox was commonly ~10%+ faster in various web browser benchmarks with the Spectre V1/V2/V4 mitigations disabled. There were several other workloads showing a difference in the 2~4% range when disabling the mitigations for the Cypress Cove cores.
Out of 96 different tests ran (see all the data in full over on OpenBenchmarking.org) in the default and then mitigations=off state on the Core i9 11900K, there was 2% difference overall for the geometric mean. The overhead of these mitigations on Rocket Lake is less than what was seen with older generations of Intel CPUs requiring more software mitigations but as shown there can be a sizable difference depending upon the workload. In any case, with Rocket Lake having launched, the mitigated/default state is what users have been seeing out of benchmarks and reviews rather than being introduced after launch, but now you have an idea for the impact if you have been curious about Rocket Lake or if you dare risk disabling the mitigations in the name of greater performance.
For those wondering about the ongoing Spectre mitigation costs with AMD Zen 3 processors, back in December I ran some Ryzen 5000 series mitigation benchmarks as well.
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