https://bugs.freedesktop.org/show_bug.cgi?id=50616
--- Comment #4 from Michel Dänzer michel@daenzer.net 2012-06-05 03:46:52 PDT --- (In reply to comment #3)
It improved the average a tiny bit, but the long ones were still there.
Did you try it with vblank_mode=0 as well?
Calling glFinish() instead of glFlush() before glXSwapBuffers() might give a better idea of where the time is actually spent.
P.S. Please attach files here directly instead of referencing external sites.