AMD Ryzen 7000 it’s here to compete with Intel’s Raptor Lake generation. While the performance and temperature tests are taking center stage, possibly the biggest surprise comes from the front of Linuxwhere, according to tests conducted by Phoronix, keeping mitigations against Specter V2 improves performance compared to disabling them, which is really surprising.
Meltdown and Specter were published right at the beginning of the year 2018 and appeared like elephants in the china shop. The first, which mainly affected Intel processors, could be definitively resolved in exchange for losing performance, but the second, which also affected AMD and ARM processors, is unsolvable, which has forced mitigations to be piled up at the level of the kernel of the operating system, the microcodes of the processors, the drivers and even the applications, all with the aim of minimizing the chances of success of the attacks.
Aside from hampering attacks, another consequence of applying Spectre-like vulnerability mitigations is performance loss, so Phoronix’s discovery of running Linux on Ryzen 7000 (Zen 4) comes as quite a surprise.
Michael Larabel, head of Phoronix and main developer of the benchmarking suite of the same name, first tried the model Ryzen 9 7950Xand after not believing what he had seen, he decided to do more tests with a Ryzen 5 7600X to discover that it was, that the processors perform better with the default settings than with the mitigations against Specter V2 disabled.
At Phoronix they have used an ASUS ROG CROSSHAIR X670E HERO motherboard with BIOS 0604, 32GB of RAM, a 1TB Sabrent Rocket 4.0 Plus drive and Ubuntu 22.04 LTS with a slightly modified Linux 6 kernel.
Michael Larabel explains that “disabling mitigations helped in a small subset of tests, mainly in the various synthetic kernel benchmarks. OpenJDK Java workloads, database workloads, web browser tests, and many other workloads normally negatively impacted by Specter mitigations actually performed better on this Ryzen 5 7600X system than when disabled the mitigations”. On the other hand, the same person in charge of Phoronix remembers that Ryzen 700 is not affected by the majority of vulnerabilities found in processors in recent years.
It is important to keep in mind that what Phoronix has done are synthetic tests that do not have to represent a real scenario. In other words, possibly an end user, using his computer as usual, does not lose as much performance as the synthetic tests indicate, but results such as those obtained by Linux 6 over Zen 4 go, at least initially, against the logic.
If these results are maintained over time, AMD has many options to score a good goal per squad against Intel. It seems that the red giant has managed to make the mitigations against Specter V2 work for him instead of against him. However, others speculate a possible kernel bug. Surely in the near future we will discover if this is a mirage or reality.
