Another Intel Gen12 Performance Optimization Coming For Mesa's Vulkan Driver

A small but measurable and seemingly widespread performance optimization is currently being buttoned up for Intel's open-source "ANV" Vulkan driver within Mesa to benefit latest-generation Gen12/Xe Graphics.

A pending merge request is providing 1~3% better performance on Intel Gen12 graphics hardware with the ANV Vulkan driver. Games like Dota 2, Rise of the Tomb Raider, Shadow of the Tomb Raider, Fallout 4, and others have been tested and confirmed to benefit.

The driver change is to reduce the tile and data cache flushes. This change is specific to Gen12+ with the hardware's new unified cache architecture. The driver's current behavior was to flush the tile and data caches at the start of every command buffer and in some cases more times within a command buffer. But by avoiding those unnecessary flushes on Gen12, there's a measurable performance win.

For some games the current driver behavior meant hundreds of tile cache and data cache flushes in a single frame to now only a handful of cache flushes. Shadow of the Tomb Raider for example dropped its TC flushes from 484 to 30 and DC flushes from 309 to 3 with this pending work.

This Intel Gen12 Vulkan driver optimization for Linux users/gamers to enjoy is currently pending with this MR but will hopefully see mainline still ahead of next month's Mesa 21.1 branching.