AMD confirms Linux "performance marginality problem" on Ryzen


— 3:38 PM on August 7, 2017

AMD's Ryzen processors' abundance of CPU cores and threads combined with Linux's ability to efficiently use them seems like a match made in heaven. Even the strongest marriages have some ups and downs, though, and Michael Larabel at Phoronix was able to uncover a consistent sore point between Ryzen and Linux. The site's compilation test consistently causes segmentation faults (usually known as "segfaults," causing application crashes) on Ryzen CPUs. Larabel contacted AMD and the company's engineers confirmed the issue, describing it as "a performance marginality problem exclusive to certain workloads on Linux." AMD's engineers went on to explain that the problem is unique to Ryzen desktop chips and is not present in the upcoming Ryzen Threadripper high-end desktop CPU line or in the Epyc server processors.

The scenarios present in the torture test suite seem unlikely to be reproduced in most real-world situations, and isolating the crashes apparently wasn't a straightforward process. Larabel's initial testing shows that Ryzen CPUs would exhibit a segfault during the compilation portion of the script, approximately 85 seconds after it started. Phoronix readers then reported segfaults on non-AMD CPUs in a different portion of the script, leading to the hypothesis that the problem was with the test itself. Larabel proceeded to update the script and reported that the Clang crashes are indeed unique to Ryzen systems. The reviewer then reached out to AMD, whose engineers have confirmed the issue and said that the problem is also not confined to any particular motherboard vendor.

Research into the problem seems to be in a preliminary state and it remains unclear as to whether the issue extends beyond Linux and into other Unix-like operating systems like FreeBSD. Ryzen CPU owners whose work has been affected by the problem can contact AMD Customer Care. According to Phoronix, AMD will add more rigorous testing and QA under Linux when developing future products. The silicon manufacturer says its upcoming Threadripper and Epyc CPUs aren't affected and that Ryzen desktop chips do not exhibit the same problem in a Windows environment.

Tip: You can use the A/Z keys to walk threads.
View options

This discussion is now closed.