diff --git a/Doc/whatsnew/2.7.rst b/Doc/whatsnew/2.7.rst
index e44a42b3539..9148743dc05 100644
--- a/Doc/whatsnew/2.7.rst
+++ b/Doc/whatsnew/2.7.rst
@@ -129,6 +129,18 @@ A few performance enhancements have been added:
   (Suggested by Martin von Loewis and implemented by Antoine Pitrou;
   :issue:`4074`.)
 
+* The garbage collector tries to avoid tracking simple containers which
+  can't be part of a cycle. As of now, this is true for tuples and dicts
+  containing atomic types (such as ints, strings, etc.). Transitively, a dict
+  containing tuples of atomic types won't be tracked either. This helps bring
+  down the individual cost of each garbage collection, since it decreases the
+  number of objects to be considered and traversed by the collector.
+
+  To help diagnosing this optimization, a new function in the :mod:`gc`
+  module, :func:`is_tracked`, returns True if a given instance is tracked
+  by the garbage collector, False otherwise.
+  (Contributed by Antoine Pitrou; :issue:`4688`.)
+
 
 .. ======================================================================