Radeon Vulkan Driver Gets A Significant Performance Optimization For Pre-4.20 Kernels
Fresh out of our Radeon Vulkan Driver Benchmarks: AMDVLK 2018.4.2 vs. AMDGPU-PRO 18.40 vs. Mesa 18.2/19.0, RADV driver co-founder Bas Nieuwenhuizen has posted a patch to help further the performance of the Mesa RADV driver.
Bas reported in the forums today that they are seeing much better numbers with Linux 4.20. It turns out that is due to an AMDGPU DRM change by AMD's Christian König for trying to allocate video RAM as a power of two.
Nieuwenhuizen has made a similar change to the AMDGPU RADV Winsys code for trying to help pre-4.20 kernels with a similar move. The RADV change is algining large buffers to the fragment size.
The two line patch improves the performance of Talos Principle by about 15% and also offers "significant improvements" for other games like Rise of the Tomb Raider when using Linux 4.19 and older.
As the patch is very simple, Bas is looking to have it back-ported to current Mesa stable series too rather than having to wait for users to switch to Mesa 19.0. As since by the time Mesa 19.0 is widespread among Linux gamers, they will likely be on Linux 4.20+ kernels too.
I'm currently working on some AMDGPU kernel comparison benchmarks with RADV and should have them out later today.