Comment 9 for bug 996343

Another idea: This could be the known problem with glFinish (in the default rendering path) slowing down rendering. glFinish was introduced to eliminate tearing. To work around it try CCSM > Workarounds > enable "Force full screen redraw (buffer swap) on repaint". That will use the simpler glXSwapBuffers code path which usually provides faster frame rates and much better smoothness. And without tearing.

We have several ideas in mind for ensuring the latter is enabled by default in 12.10 (see bug 901097). But some other code needs to be fixed before we can turn it on for all users.