AMD Radeon R600g Gallium3D: Mesa 8.0.4 vs. 8.1 Git

Starting with Doom 3, for the modern Radeon HD 6000 series graphics cards, there was no real change in performance. However, for the older R700-class Radeon HD 4000 graphics cards, it appears that Mesa 8.1-devel is currently in a regressed state. The Doom 3 OpenGL frame-rate falls from 41 FPS to 34 FPS with a Radeon HD 4870 "RV770" graphics card. The Radeon HD 4670 also falls slightly: 21 to 19 FPS.

With Lightsmark the Radeon HD 4670 frame-rate improves by 18%, the Radeon HD 4870 frame-rate falls dramatically, the Radeon HD 6770 frame-rate is up by 45%, and the Radeon HD 6870 frame-rate is a little bit higher. With this testing it also highlights a regression I have been noticing recently: sometimes when creating a Radeon OpenGL context it ends up being noticeably slower. The Phoronix Test Suite runs each test a minimum of three times for statistical accuracy and recently out of the three runs, at least one of the runs with a recent Radeon Git stack at times will be noticeably slower. I have seen this with multiple graphics cards and multiple tests on Radeon Git in recent weeks and have not encountered this issue in the past with Radeon or other Mesa/Gallium3D drivers. It also is not too predictable with sometimes the first run being slower while other times it might be slower on the second or third run. I have not narrowed it down conclusively but looks like the Radeon DRM kernel code might be to blame.

With the Nexuiz game, the Mesa 8.1-devel R600g performance is much faster for the Radeon HD 4670, HD 4870, and HD 6770 graphics cards. There isn't much of an improvement out of the high-end Radeon HD 6870 that may be hitting a bottleneck elsewhere. With Nexuiz is another test where the Radeon OpenGL performance is sporadic on some runs.