--- a/x.rst	Sat Dec 28 16:16:55 2013 +0200
+++ b/x.rst	Wed Jan 01 12:26:33 2014 +0200
@@ -395,3 +395,22 @@
 
 ``xdotool`` and ``xautomation`` utilities use ``XText`` for emulating user
 actions.
+
+GLX info.
+=========
+
+To determine whether 3D acceleration is working::
+
+  $ apt-get install mesa-utils
+  $ glxinfo | grep render
+
+To see how many frames per second your video card is putting out::
+
+  $ glxgears -info
+
+See:
+
+  https://wiki.debian.org/Mesa
+                Mesa is an open source 3D computer graphics library that
+                provides a generic OpenGL implementation for rendering
+                three-dimensional graphics on multiple platforms.