Hi:
Could you check MigrationHeuristic setting? And try with "greedy"?
---8<---
Section "Device"
...
Driver "radeon"
...
# Option "MigrationHeuristic" "smart" # Near as slow as with default/always http://nouveau.freedesktop.org/wiki/EXA
Option "MigrationHeuristic" "greedy" # Fast as XAA, X.Org X Server 1.6.5, 2009-10-29 http://lists.freedesktop.org/archives/xorg/2008-May/thread.html#35451
...
EndSection
--->8---
GSR