Landing this week in Mesa 17.0-devel Git was OpenGL 4.3 for NVC0 Maxwell and a big performance boost as well for these GeForce GTX 750 / 900 series NVIDIA "Maxwell" graphics processors. Here are some before/after benchmarks of the performance improvements, which the patch cited as "1.5~3.5x better", when testing a GeForce GTX 750 Ti and GTX 980.
These patches that hit Mesa Git last week were published last month by Samuel Pitoiset and allowed for Maxwell hardware on the NVC0 Gallium3D driver to go from OpenGL 4.1 to OpenGL 4.3 compliance, similar to the Fermi/Kepler state for this open-source reverse-engineered NVIDIA 3D driver.
Then the big and exciting part was the "increase performance on Maxwell GPUs by, at least, x1.5 up to x3.5 for some benchmarks." Those gains come from instruction pipelining improvements for Maxwell in the NVC0 code. But while those numbers are exciting, keep in mind the GeForce GTX 900 (Maxwell) cards currently cannot re-clock with Nouveau on the Linux 4.10 kernel. Thus they are stuck to their boot frequencies and mean rather low performance.
So for these before/after benchmarks I used a GTX 750 Ti and GTX 980. The good thing about the GTX 750 Ti is that it's the last NVIDIA GPU without needing any signed firmware blobs with being an original Maxwell part and Nouveau developers even have re-clocking support for the GTX 750 series. Thus for these tests, the GTX 750 Ti actually performs better than the GTX 980 on the Nouveau driver since the budget "GM107" card can be re-clocked with this driver.
A variety of OpenGL benchmarks were run for this article using the open-source Phoronix Test Suite benchmarking software. This article is just looking at the Nouveau performance while I will have some NVIDIA binary driver results for at least the GTX 750 Ti for reference in the next few days.