Intel Mesa 3D Driver Gets Some Performance Tweaks

At least three commits seeking to improve the performance of Intel's open-source 3D/OpenGL Mesa driver were merged on Monday.

On the same day as bringing GL2 to Intel's i915 Mesa driver, Eric Anholt committed a set of improvements to the Intel i965 driver that supports back from the i965 hardware up through the latest Ivy Bridge, Haswell, and Valley View graphics processors. The performance improvements committed today come down to:

i965/fs: Allow LRPs with uniform registers. This commit by Eric boosts the GLB2.7 performance by just under 1% on a Haswell development system by changing around just a few lines of code.

i965: Disable Z16 on contexts that don't require it.. It turns out that the Z24 texture format on Intel hardware is faster than Z16. OpenGL 3.0+ mandates Z16 texture format support while OpenGL ES doesn't have any explicit requirement, so this commit chooses the performing-layout. Eric notes that the trex performance went up by 10.7% on his Intel Ivy Bridge system with this change.

intel: Be more conservative in disabling tiling to save memory. The third Intel Mesa driver commit today seeking to boost performance is being more conservative with disabling tiling when the width is much smaller than the tile size. Eric notes that this improves the performance on his Ivy Bridge system by just over 1% while his Haswell system is about 3.38% faster.