The Linux 3.5 kernel is capable of delivering some massive performance gains for some of the more recent generations of ATI/AMD Radeon graphics processors. Here's some benchmarks showing the hefty performance gains found when using the latest kernel that is still being developed.
For any members of the Phoronix Forums, in recent days you likely have come across several comments concerning how the Linux 3.5 kernel has vastly sped up the open-source Radeon Linux graphics driver. It seems the 3.5 Radeon DRM has a big impact on performance for some of the newer GPUs, even more so than say Hierarchical-Z, based upon these forum comments. Alex Deucher of AMD also said in the forums, "Kernel 3.5 should see a nice boost in performance on evergreen and NI with the backendmap fixes." Now that I'm back in America, as soon as returning, I fired up the Intel Ivy Bridge test system while swapping out different Radeon graphics cards and testing out some of the recent kernel releases.
What we have in this article is the Radeon HD 5750, Radeon HD 5830, Radeon HD 6450, Radeon HD 6770, and Radeon HD 6870 graphics cards all being compared with the latest open-source driver code. The Mesa (8.1-devel), xf86-video-ati, and libdrm were all fetched from Git on 6 June 2012. Besides comparing the different graphics cards, with each GPU the Linux 3.2, Linux 3.4, and Linux 3.5 kernels (as of 6 June) were compared to see the impact that this latest Linux 3.5 Radeon DRM code has on the overall performance for this Evergreen and Northern Islands hardware. The Linux 3.2 kernel was tested since that is what is in use by Ubuntu 12.04 LTS and other Linux distributions at this time as a common version.