Intel Lands Some MSAA Mesa Performance Improvements

A series of commits hitting Mesa's mainline Git this afternoon offer up some multi-sample anti-aliasing (MSAA) improvements for the Intel open-source graphics driver.

Among the commits entering our radar a short time ago include:

Change the winsys MSAA blits from blorp to meta - This change of about 150 lines of code yields the MSAA-forced "citybench" OpenGL test-case to run about 8% faster while DRI2 MSAA-enabled glxgears performance drops by about 13%.

Skip reallocating the private MSAA miptree, unless it's resized - The performance of a micro-benchmark with MSAA was increased by about 1.237%.

Add an env var for forcing window system MSAA - Intel has finally added back an environment variable for forcing multi-sample anti-aliasing. However, Intel is using the INTEL_FORCE_MSAA environment variable for this override by specifying the MSAA sample count, while other drivers use a different approach. The Gallium3D drivers meanwhile use GALLIUM_MSAA and they also support __GL_FSAA_MODE -- with this later environment variable also being what's used by the NVIDIA Linux graphics driver.

There's also been a number of other Intel driver changes landing today for this "classic" DRI driver in Mesa Git.