By admin 
The Ubuntu Kernel Team issued a statement this morning to proactively warn Ubuntu Linux users on Ubuntu 26.04 and Ubuntu 24.04 LTS HWE users that the next kernel point release will contain a performance regression for AMD GPUs in compute-heavy workloads with up to a 42x performance hit. The positive news is that due to this being an upstream regression in a Linux 7.0 point release, upstream stakeholders and other Linux distributions that more quickly shipped the problematic code already have a fix coming down the pipe.
Ubuntu’s forthcoming 7.0.0-28.28 kernel update is what’s carrying this AMDGPU performance regression. It’s described in the Ubuntu Kernel Team statement as:
“Affected users may experience a significant performance regression, particularly when running compute-heavy workloads that utilize ROCm, such as Stable Diffusion XL (SDXL) inference via ComfyUI. This manifests as a drastic increase in processing time—reports indicate slowdowns of up to 42× (e.g., from 9 seconds to 388 seconds). Please note that this is a throughput degradation rather than a system lockup.”
That 42x slower figure stems from this ROCm bug report from mid-June that noted on Fedora 44 moving from Linux 7.0.11 to Linux 7.0.12 had introduced this massive performance regression in ComfyUI.
Separately there was also this ComfyUI bug report noting the extremely slow performance on AMD graphics hardware with Linux 7.0.12.
Thanks to the upstream action, the AMDGPU performance regression is already fixed upstream by this commit found in Linux 7.0.13. The issue and fix pertain to a retry loop in the AMDGPU heterogeneous memory management (HMM) code.
While already fixed in Linux 7.0.13 upstream, due to the alignment of the Ubuntu kernel update timing, they are shipping the Linux 7.0.0-28.28 update that unfortunately has this regression present. The fix in turn will make it to the follow-up Ubuntu kernel release post-7.0.0-28.28. The 7.0.0-28.28 kernel is still being shipped out to provide other important Linux security fixes. But for those making use of AMD ROCm compute, the Ubuntu kernel team is recommending users avoid the 7.0.0-28.28 kernel version.