Ref: http://lists.gnu.org/archive/html/emacs-devel/2012-11/msg00377.html
** New sampling-based Elisp profiler.
Try M-x profiler-start, do some work, and then call M-x profiler-report.
When finished, use M-x profiler-stop. The sampling rate can be based on
-CPU time (only supported on some systems) or memory allocations.
+CPU time or memory allocations.
+++
** CL-style generalized variables are now in core Elisp.