Mesa 21.3 Enables NGG Culling By Default For RDNA2 GPUs

The Radeon Vulkan driver "RADV" within Mesa 21.3 is enabling NGG culling by default for Radeon RX 6000 series (RDNA2) GPUs and newer as another performance win.

NGG culling was added to RADV this summer but initially only exposed as an opt-in feature via environment variable. This NGG-powered removal of unneeded triangles during rendering is also supported on RDNA1 / Navi 1x GPUs but is not being enabled by default -- our own tests with Navi 1x have confirmed the results to be a wash while the support is in good standing for the latest-gen GPUs.

With performance wins in some Vulkan workloads and the good shape for those testing this "NGGC" option the past few months, today's Mesa 21.3-devel code has enabled it while also adding the "RADV_DEBUG=nonggc" option to force disable it for comparison/testing purposes.

New Mesa 21.3-devel benchmarks coming up soon with the feature freeze / code branching being imminent.