There has been a lot of writing about the performance impact of Intel based graphical cards under Linux since the rewrite of the kernel driver, up to the point that it's becoming almost impossible to find a decent configuration, especially after some upgrades of your favorite distribution in terms of kernel and x.org. I found 3 modifications in my xorg.conf file which were causing really bad performance on my eeePC. After cleanup, I found myself with the following configuration, which gives me satisfactoring performance :

Section "Device"

	Identifier "Configured Video Device"

	Option "EXAOptimizeMigration" "true"

	Option "MigrationHeuristic" "greedy"

EndSection

Trick is not the be using UXA or tiling, which might be a cause of the performance hit.