Mesa 20.1 Adds A Vulkan Device Selection Layer For Better Handling Multi-GPU Setups

After the merge request was open for more than a half-year, Mesa 20.1 has landed a Vulkan device selection layer for choosing between multiple Vulkan-enabled GPUs on a given system as the default device.

This Vulkan layer allows for picking the default GPU for X11/Wayland/device sessions, similar to DRI PRIME for OpenGL. This Vulkan layer first checks for the MESA_VK_DEVICE_SELECT= environment variable for being pointed towards the GPU/driver to be used, otherwise checks DRI_PRIME and tries to match it to a proper configuration.

This should help out particularly in hybrid GPU setups/laptops. The Vulkan API does support the notion of multi-GPU rendering, but so far on Linux we've seen few (any?) games or prominent software actually employ that technique, so being able to select a given GPU device for use by Vulkan games is important.

The layer is in place for Mesa 20.1 soon to be hitting this quarter's feature freeze. The layer does need to be enabled at build time via the vulkan-device-select-layer Meson option.