This is a tracker entry for a report and patch in an emacs-devel mailing
list thread:

 http://lists.gnu.org/archive/html/emacs-devel/2014-10/msg00727.html

The issue is that auto-revert-mode reacts to modifications on a timer,
even if its backend is event-driven. There is a prototype patch in that
thread, attached here also.

On Linux, the two available backends have issues, so this patch wouldn't
be completely effective until those are resolved.

The gfile backend has a problem where emacs isn't using glib correctly,
and the gfile backend itself, in turn, adds artificial delays in how it
deals with inotify. Those are discussed (and partly patched) here:

 http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18861

The inotify backend has an issue where it doesn't deal with more than
one monitored file in a directory correctly:

 http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18880