Intel's Open-Source Graphics Driver Lands Another Icelake/Gen11 Performance Optimization

Intel open-source developer Kenneth Graunke who is the lead developer on their "Iris" Gallium3D driver has landed a new performance optimization in Mesa to help their Gen11/Icelake graphics performance.

Ken managed another 1~3% performance boost for Gen11/Icelake. The optimization is using headerless RT writes for MRT cases and is an optimization made to their common compiler code used by i965/Iris/ANV drivers, but Ken's testing is focused on their new Iris OpenGL driver.

He explained in the commit, "Gen11 adds support for specifying the render target index and src0 alpha present bits in the extended message descriptor. Previously, we had to use a message header for this, requiring extra instructions to write the fields, and two registers of extra payload."

This only affects Gen11 and later with this being a new feature of the architecture. With this optimization he found their new OpenGL driver to run 1~3% faster depending upon the workload/application.

Further Intel Linux graphics driver optimizations in general are expected moving forward, per Intel's Lisa Pearce:

Thanks for noticing! We are on a mission to get our Linux graphics stack fully optimized. More to come. 👍 https://t.co/aGRLoG5hRH

— Lisa Pearce (@gfxlisa) August 12, 2019