bug#18522: 24.4.50; mapcar is very slow

[Peter Münster]

On Mon, Feb 22 2016, Eli Zaretskii wrote:

> I think the next step is to profile the code below "let".  Can you try
> using 'perf' for that purpose?

Slow emacs: almost all time is spent in Fset_default (96%)

Fast emacs:
  25.36%  emacs         emacs                          [.] eval_sub
  10.73%  emacs         emacs                          [.] Fset_default
   9.63%  emacs         emacs                          [.] Flength
   6.54%  emacs         emacs                          [.] unbind_to
   5.44%  emacs         emacs                          [.] hash_lookup
   4.53%  emacs         emacs                          [.] Flet

You can try it too on your running sessions: "perf record -p PID" and
then "perf report". (just use something like "dotimes (i 1000000000)")

-- 
           Peter