Spectre-v2 mitigation wreaks havoc on the performance of some Intel CPUs as AMD chips come out largely unscathed
Specter-v2 mitigations don’t tank the performance of AMD CPUs as much Intel processors. According to a report published by Phoronix, some Intel processors suffered performance up to 35% performance degradation in certain workloads. On the other hand, AMD processors don’t suffer a performance impact of more than 10% with the same type of Spectre-v2 mitigations as Intel’s chips.
Initially, AMD took a different route to mitigate the Spectre vulnerability than Intel. Where Intel used a Retpoline approach to protect against the vulnerability, AMD used LFENCE/JMP. After a paper published by a group of researchers from Vrije Universiteit Amsterdam revealed that Intel and ARM are still susceptible to Spectre-v2 vulnerability, Intel’s STORM security team started researching the issue and found out that AMD’s Spectre-v2 mitigation is not bullet-proof.
Responding to this discovery, AMD issued instructions to switch to Retpoline instead of LFENCE/JMP. The switch to Retpoline hit AMD CPUs with some performance penalties. But per Phoronix’s testing, the penalties are way worse on Intel’s chip.
For instance, the networking performance took a 26.7% hit on the Intel Core i9-12900K. On the other hand, AMD Ryzen 9 5950X only lost about 5.3% performance. Similarly, in the storage benchmark, the Core I9-12900K reported 14.5% performance degradation while the Ryzen 9 5950X only dropped by 5%.
The drop was even bigger on previous-gen Intel processors as the Core i7-1185G7 CPU went down as low as 35.6% on OSBench. OSBench tests things like process creation in operating systems.
It is important to note that Phoronix tested the performance of these chips on Linux. We still don’t know what kind of numbers the CPUs will post once they are tested on Windows.