For putting the open-source GeForce GTX 900 driver performance into better perspective from the results this week with the new support found on Linux 4.6 and compared to NVIDIA's proprietary driver, hare are some benchmark results when comparing the Nouveau driver performance of the GTX 900 "Maxwell" graphics cards to that of the GTX 600/700 "Kepler" graphics cards with their experimental re-clocking support.
While the previous article was an open vs. closed-source NVIDIA Linux driver comparison, this article is just looking at the Nouveau driver performance between the GTX 600, 700, and 900 series. As mentioned in the earlier article, the GTX 900 Nouveau support doesn't yet have re-clocking support and that's unlikely to come anytime soon. However, the GTX 600/700 series does have experimental re-clocking support via debugfs but you must re-clock the graphics card manually, your results may vary, and there isn't yet support for any dynamic re-clocking.
The Maxwell cards tested of the GTX 950, GTX 960, GTX 980, and GTX 980 Ti graphics cards were compared against the GTX 680, GTX 760, and GTX 780 graphics cards. With the Kepler cards tested today, they were run both "out of the box" and then manually re-clocked to the 0f performance state via debugfs.
The same software stack was used during testing of Ubuntu 16.04 x86_64 with the Linux 4.6 Git kernel following the DRM-Next merge, xf86-video-nouveau 1.0.12 DDX, and Mesa 11.3-devel Git from the Oibaf PPA as of last week. All of the OpenGL benchmarks in this article were carried out in a fully-automated and reproducible manner using the open-source Phoronix Test Suite benchmarking software.