Engineers from Canonical have issued a warning regarding regressions in the upcoming update of packages with kernel 7.0.0-28.28, which will be distributed to users of Ubuntu 26.04 and Ubuntu 24.04. The regression specifically affects the amdgpu driver, resulting in a significant decrease in performance for some applications utilizing the AMD ROCm. For instance, the execution time of the Stable Diffusion XL (SDXL) model using ComfyUI has slowed down by 42 times, from 9 seconds to 388 seconds. More information can be found here.
The issue was first identified in the Linux kernel update 7.0.12, upon which the kernel package for Ubuntu version 7.0.0-28.28 is based. Despite containing fixes for critical vulnerabilities, Canonical cannot delay the release due to the regression. Therefore, the decision was made to proceed with the update as is and address the regression in the subsequent corrective release. Users who prioritize addressing the regression over fixing the vulnerabilities have the option to hold off on upgrading to the 7.0.0-28.28 release until the next update. More details can be found here and here.
This issue also affects the 7.0.12 kernel packages distributed for Fedora, CachyOS, and other Linux distributions. The problem has been resolved in the 7.0.13 kernel release. As a temporary workaround to address the regression, users can utilize the “–disable-mmap” flag in ComfyUI. More details on the fix can be found here.