compositing enabled with Radeon mobility X300

[Jethro Tull]

I'm using the kernel 4.4.14 with XFCE 4.12, as written in the subject my GPU is a Radeon mobility X300 and the driver used is the open source "radeon". 

I noticed that enabling compositing was resulting in very slow windows manipulations like dragging, resizing, browsing them with Alt + tab. It takes nearly 2 seconds to display the big contextual menu when starting to browse through the windows. And I also noticed that using an extended desktop on a second monitor was leading to some windows not being refreshed resulting in a nearly scrambled desktop after some time of use with several graphical programs. I also noticed some similar problems with the terminal.

Does compositing require some special featured GPU or is that the open source radeon driver not neatly written?