Running glxgears with the following command

LIBGL_ALWAYS_INDIRECT=1 glxgears

prints 60 FPS on my system, while actual picture updates are about 1-2 FPS. This is due to command buffering I believe. The fix would be something like this:

--- glxgears.c.orig    2014-03-22 16:59:24.000000000 +0400
+++ glxgears.c  2016-07-22 12:24:15.260412891 +0300
@@ -340,6 +340,10 @@
 
    draw_gears();
    glXSwapBuffers(dpy, win);
+   /* Make sure that the whole draw-swap cycle is complete before
+      measurements. Otherwise we'll have rare updates but still
+      report high frame rates with indirect rendering. */
+   glFinish();
 
    frames++;