For this round of testing I'll be using kernel 2.6.28-rc5 and libdrm, mesa and xf86-drv-ati all from git as of Feb 16, 2011 8:30am GMT - 7. About 2 years ago I did some 2d tests of the Linux driver on the r600g and got some good results. The performance of gtkperf has went up and down over time, but generally has hovered around 33-38 seconds on my machine when run with gtkperf -c 500 -a.
The recent radeon patches have enabled linear aligned performance and according to the changelog
linear aligned is supposedly more performant, but more importantly, linear general only works on the CB without slices. The texture blocks technically don't support linear general although, I think linear general gets upgraded to linear aligned in the hw which is why it currently works.
This change required changes to the kernel module as well, and those changes appeared in the 2.6.38-rc5 kernel. At this point I have also enabled color tiling, but it is currently only 1d color tiling at this point. Alex Deucher has stated that he would like to have 2d color tiling working before color tiling is enabled by default on the r6xx chips.
So the results of the test are
GtkPerf 0.40 - Starting testing: Wed Feb 16 08:56:58 2011
GtkEntry - time: 0.09
GtkComboBox - time: 2.54
GtkComboBoxEntry - time: 2.13
GtkSpinButton - time: 0.79
GtkProgressBar - time: 0.61
GtkToggleButton - time: 0.48
GtkCheckButton - time: 0.35
GtkRadioButton - time: 0.56
GtkTextView - Add text - time: 3.48
GtkTextView - Scroll - time: 1.20
GtkDrawingArea - Lines - time: 5.16
GtkDrawingArea - Circles - time: 6.67
GtkDrawingArea - Text - time: 4.16
GtkDrawingArea - Pixbufs - time: 0.42
Total time: 28.63
I did this test a couple of times and always got results below 30 on my machine, which means that 2d performance has roughly increased by 10%. Please note that gtkperf is not a very good benchmark and so you can consider this test garbage if you want, but I have found the results useful at times.
gtkperf is very sensitive to other applications updating the screen, so be sure you have minimal applications running when performing this test.