Linux kernel patch fixes AMD Ryzen AI 9 HX 370 scheduling regression

A patch merged to the Linux kernel recently fixes a performance regression affecting the AMD Ryzen AI 9 HX 370 laptop SoC. Reports say the issue occurred when using Cache Aware Scheduling during Clang full-LTO workloads. On these tasks, processes started on the eight Zen 5C efficiency cores would not move to the four larger Zen 5 performance cores.

Image: Phoronix

The Ryzen AI 9 HX 370 features cores with different specifications. The Zen 5C cores clock up to 3.3GHz and have 8 MB of L3 cache, while the Zen 5 cores reach approximately 5.1GHz and have 16 MB of L3 cache. The patch ensures that asymmetric packing takes priority over LLC balancing for active load balancing. This allows the scheduler to move tasks to higher performing idle cores instead of keeping them on cores with shared cache.

The fix is merged for Linux 7.4 Git and is marked for back-porting to Linux 7.2 and 7.3 stable. This change may also benefit other Ryzen SoCs that use a mix of Zen 5 and Zen 5C cores.