https://bugs.freedesktop.org/show_bug.cgi?id=34929
--- Comment #4 from Fabio Pedretti fabio.ped@libero.it 2011-03-03 02:06:34 PST --- (In reply to comment #3)
I can't see a significant performance difference with the games you mentioned. openarena fps went from 93 to 91 with threading. glxgears frames went from 15k to 17k. Torcs fps went from 23 to 27. There is no visible difference in supertuxkart. I don't say it always improves performance, but it should mostly be a win.
Without gdb torcs is about the same but I definitively get a slowdown with glxgears:
$ vblank_mode=0 RADEON_THREAD=0 glxgears 2>&1 | grep FPS 8445 frames in 5.0 seconds = 1688.847 FPS 8196 frames in 5.0 seconds = 1639.119 FPS 8197 frames in 5.0 seconds = 1639.396 FPS
$ vblank_mode=0 glxgears 2>&1 | grep FPS 6789 frames in 5.0 seconds = 1357.671 FPS 6878 frames in 5.0 seconds = 1375.596 FPS 6879 frames in 5.0 seconds = 1375.797 FPS
Did you try running some apps under gdb? The problem is hugely amplified with it. Example:
$ vblank_mode=0 RADEON_THREAD=0 gdb glxgears 2>&1 | grep FPS 8171 frames in 5.0 seconds = 1634.191 FPS 8258 frames in 5.0 seconds = 1651.503 FPS 8544 frames in 5.0 seconds = 1708.673 FPS
$ vblank_mode=0 gdb glxgears 2>&1 | grep FPS 1216 frames in 5.0 seconds = 242.979 FPS 1131 frames in 5.0 seconds = 226.024 FPS 862 frames in 5.0 seconds = 172.242 FPS
It looks like opening/exiting threads has a noticeable overhead.