Even in 2011, the Mesa / Gallium3D drivers for the recent ATI Radeon graphics cards are still far from being comparable to the official Catalyst Linux driver in terms of performance. This though is not a huge surprise, but is unfortunate. The OpenGL support is still also well behind with the Catalyst driver supporting OpenGL 3.3/4.1 while all of the Mesa-based drivers are still bound to OpenGL 2.1.
One of the other interesting takeaways from this large Linux graphics comparison was with the VDrift results where a few of the ATI graphics cards being controlled by the Gallium3D driver actually outperformed the Catalyst driver. However, from the numbers it looks more along the lines of the Catalyst driver hitting a show-stopping bug.
If looking at the geometric mean for all of the test results in this article for all of the graphics cards excluding the R500-based Radeon X1950PRO (as for the open-source side it's using R300g/c rather than R600g/c and it's unsupported by Catalyst 10.12) and then averaging them, it shows the Catalyst driver on Linux is roughly five times faster (5.18x to be exact) than the ATI Gallium3D driver for the Radeon HD 2000/3000/4000/5000 series. That's under this OpenGL workload of tests that work with the open-source drivers and not the demanding workloads that will work only with Catalyst at this point (i.e. the Unigine Engine tech demos and games). Again, this is with the latest upstream code at this time for the Linux 2.6.37 kernel, Mesa 7.10-devel, and xf86-video-ati 6.13.99.
There has been much progress over the past year to the open-source ATI drivers and the Linux graphics stack in general, but it still has a ways to improve. Our similar set of results for the NVIDIA side with the open-source Nouveau Gallium3D driver will be out in a few days. Also worth noting is that at this time only the R300 class Gallium3D driver is enabled by default in Mesa (and most Linux distributions) while the R600 classic Mesa driver is still used rather than its newer Gallium3D driver. Based upon the faster performance, minimal regressions (just Nexuiz with Evergreen ASICs and a few other areas), the superior architecture (support for state trackers, etc), better OpenGL 2.1 support, and other benefits, hopefully in Mesa 7.11 we will see R600g by default and it being utilized by most Linux distributions upon their next major update.