Re: Emacs 23.0 is much slower starting than Emacs 22.3

[David De La Harpe Golden]

Alan Mackenzie wrote:

> However, the current function isn't that slow.  I timed it for 100
> iterations on a file 2,927,889 bytes big.  It's taking 0.72s for this
> file, i.e. about 0.25s per megabyte, and that's on my 1.2 GHz Athlon.
>
> So on emacs/src's 118 files.c, total size 8772802, that function would
> take only 2.5s, again, on my Athlon.  On your machine it would be ~0.5s.
>
> Besides, in my original measurements, I was executing the same CC Mode
> in Emacs 22 and Emacs 23.
>
> c-neutralize-syntax-in-CPP isn't the problem.

Probably not, or at least not the slowdown you're seeing i.e. your 
relative emacs22/23 problem.  N.B. It wasn't intended as a slight - I do 
appreciate C is a relative pain to parse, syntax-highlight and deal with 
in general, I'm_ not_ saying c-mode's apparently associated overhead is 
necessarily unreasonable,  but it may explain why stuff I was generally 
doing in emacs day-to-day seemed to load a little bit faster than this 
particular test case (if you recall, I was surprised at the result) - I 
relatively seldom edit c files!  But c-mode as a whole _does_ account 
for a significant chunk of the startup time on the 180 .c files I was 
testing with:

time emacs -l fftest.el -f kill-emacs
with in .emacs  a sneaky
(setq auto-mode-alist (cons (cons "\\.c\\'" 'text-mode)       auto-mode-alist))

emacs c-mode    realtime
22      on      4.951
23      on      7.388
22      off     2.830
23      off     4.089