I try to run my Archlinux with Glamor acceleration on my RV670 card (AGP), but X server takes a (slight) high CPU usage (~15-18%, on Opteron 185 2600 MHz S939) when i activate it with xorg.conf. Revert back to EXA falls X CPU usage to < 5-6%. Moreover, with Glamor, some gtk2 applications have strong lag for example when i click on a menu in the menu bar, like Thunar, or, when i switch tabs of web pages in Midori. This is strange because i have no problem when i scroll web pages, all run smoothly (better performance than EXA). On other gtk2 applications i haven't this problem. Also, with Glamor enabled the XFCE logout dialog takes about a minute to be shown. Neither Xorg.log nor dmesg show anything about any bug (memory leak or other). X has never crashed.
Here some informations :
glxinfo > OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD RV670
OpenGL core profile version string: 3.1 (Core Profile) Mesa 9.2.1
OpenGL core profile shading language version string: 1.40
OpenGL core profile context flags: (none)
uname > 3.11.4-1-ARCH #1 SMP PREEMPT Sat Oct 5 21:22:51 CEST 2013 x86_64 GNU/Linux
OK, on Libreoffice buttons are paint in black, and the application causes a high X cpu usage (~40 %). When i open a file in Calc, the system is slow down and is very near to hang up.
You should try current git glamor, it has some fixes and speedups.
Exactly same problem with Mesa 10.0.1
*** This bug has been marked as a duplicate of bug 68524 ***