RADV Vulkan Driver Begins Landing Optimizations For AMD Smart Access Memory

Written by Michael Larabel in Radeon on 4 January 2021 at 08:41 AM EST. 10 Comments
Following RadeonSI seeing optimizations around AMD Smart Access Memory (Resizable BAR) support last month, the Radeon Vulkan driver "RADV" within Mesa 21.0 is also seeing similar treatment.

Linux has been seeing more work in recent weeks around Smart Access Memory / Resizable BAR support and that continued this morning with Mesa 21.0 Git seeing the initial RADV support.

MR 7979 merged today to Mesa 21.0 now makes use of vRAM for the command submission and upload buffer if all vRAM is CPU visible (SAM / resizable BR being enabled). RADV co-founder Bas Nieuwenhuizen spearheaded the patches. With the support enabled, Bas found the patches to help the Basemark Vulkan benchmark by about 3% while for Shadow of the Tomb Raider it was around 2% faster.

This functionality is enabled only for discrete GPUs with Smart Access Memory enabled and isn't enabled for APUs due to memory pressure concerns. The new code also adds a RADV debug flag of "nosam" to force-disable the functionality if wanting to compare the new code path's performance.
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