An Updated Look At Radeon Gallium3D 2D Color Tiling
In continuation of the Using The New Radeon Gallium3D 2D Color Tiling article from January, here's updated benchmarks of the latest Radeon Linux driver code with this performance-boosting feature enabled.
This latest testing was done using the latest Mesa 8.1-devel Git, xf86-video-ati Git, and drm-next (what will be the Linux 3.4 kernel) as of 15 March 2012. From January's article, "As talked about last week, 2D color tiling has been around for a while now with the R300 driver for providing this speed boost for ATI graphics processors up through the ATI Radeon X1000 (R500) graphics cards, but for the Radeon HD 2000 series and newer the support has been missing. There has been some off-by-default R600 1D color tiling support, but 2D tiling is to produce faster results. The 1D (micro) tiling groups nearby pixels into tiles and so they reside close within the video memory so that color access is faster. The 2D (macro) tiling then locates the adjoining tiles nearby in the video memory."
With the latest open-source Radeon driver code from an Ubuntu 12.04 setup on top of the Intel Core i7 3960X test-bed, several OpenGL tests via the Phoronix Test Suite were run with and without the 2D color tiling support. This was controlled via enabling/disabling the ColorTiling and ColorTiling2D options in the xorg.conf. Swap buffers wait was also disabled the entire time.
The graphics cards used for this benchmarking were a Radeon HD 4890 and Radeon HD 6950. In terms of the overall quality of 2D color tiling at this point for R600+, on most of the graphics cards tested for most OpenGL games, the support was fine and there were no stability or visual problems. The exception to the OpenGL game support was that Doom 3 was always corrupted with this latest stack with 2D color tiling enabled.
With a few graphics processors, the system was less stable and would ultimately lead to a kernel segmentation fault within the Radeon DRM CS. In some cases, there would also be occasional visual rendering issues from the Ubuntu Unity desktop or in particular with the Xonotic first person shooter. The Radeon HD 4890 and Radeon HD 6950 seemed to fair the best with 2D color tiling so those two GPUs were used for this article's performance benchmarking.