diff -up mutter-3.14.4/src/backends/x11/meta-backend-x11.c.threaded-swap-wait mutter-3.14.4/src/backends/x11/meta-backend-x11.c

--- mutter-3.14.4/src/backends/x11/meta-backend-x11.c.threaded-swap-wait	2016-06-29 15:25:56.267633457 -0400

+++ mutter-3.14.4/src/backends/x11/meta-backend-x11.c	2016-06-29 15:26:35.800269586 -0400

@@ -696,6 +696,15 @@ meta_backend_x11_class_init (MetaBackend

 static void

 meta_backend_x11_init (MetaBackendX11 *x11)

 {

+  /* Set up things so that if the INTEL_swap_event extension is not present,

+   * but the driver is known to have good thread support, we use an extra

+   * thread and call glXWaitVideoSync() in the thread. This allows idles

+   * to work properly, even when Mutter is constantly redrawing new frames;

+   * otherwise, without INTEL_swap_event, we'll just block in glXSwapBuffers().

+   */

+  XInitThreads();

+  clutter_x11_enable_threaded_swap_wait ();

+

   clutter_x11_request_reset_on_video_memory_purge ();

   /* We do X11 event retrieval ourselves */