bug#18522: 24.4.50; mapcar is very slow

[Eli Zaretskii]

> From: Peter Münster <pmlists@free.fr>
> Cc: monnier@iro.umontreal.ca,  18522@debbugs.gnu.org
> Date: Fri, 26 Sep 2014 09:15:01 +0200
> 
> > How come command-execute was called 2464 times in the first profile,
> > and only 303 times in the second? This alone can explain an 8-fold
> > slowdown.
> 
> Sorry, I forgot to label the columns: 303 and 2464 are "CPU samples".

No, it's me that needs to be sorry: I keep forgetting that.

> > Anyway, looks like gnus-summary-read-group-1 takes a lot of CPU in
> > both cases, which is above the mapcar part.  Below mapcar, the most
> > expensive part is parse-time-string, which doesn't really surprise me.
> 
> On line 16, the slow mapcar takes 1090 CPU samples and the fast one 64.
> Below line 16, the profiler outputs are different and I don't know why
> and how to debug further...

I think the conclusion is that parse-time-string takes the blame.  To
see what part in parse-time-string is the culprit, perhaps load
parse-time.el (the source) before the experiment, and maybe the
profile will show more useful info.