When using MESA_copy_sub_buffer for screen updates with DisplayLink activated it creates many artifacts for the mouse cursor in places where the screen updates. The cursor also occasionally begins to flicker (but only on the non-displaylink screen when there is a displaylink screen active).
The issue does not occur when all displaylink devices are unplugged.
The issue also occurs on non-displaylink screens when a displaylink device is connected and active.
Example setup: radeon drivers, compton compositor with glx-use-copysubbuffermesa = true
This setup is also the only one I managed to find that runs displaylink at acceptable performance with a compositor active on XFCE.
Edit: this issue also occurs with the compositor turned off entirely.
Edit2: This appears to be a duplicate of
http://displaylink.org/forum/showthread.php?t=64586 please continue in that thread ^^