Re: Reliable after-change-functions (via: Using incremental parsing in Emacs)

[Eli Zaretskii]

> Date: Sat, 4 Apr 2020 12:36:13 +0000
> Cc: Eli Zaretskii <address@hidden>, address@hidden, address@hidden,
>   address@hidden, address@hidden
> From: Alan Mackenzie <address@hidden>
> 
> > > (time-it (find-file "..../src/xdisp.c") (sit-for 0))
> 
> > It might be valuable if you evaluated exactly the same form I did. And 
> > made sure that the buffer is not visited in advance. And did that in an 
> > 'emacs -Q' session.
> 
> Fair point:
> 
>     M-: (benchmark 1 '(progn (find-file "src/xdisp.c")))
> 
>     "Elapsed time: 1.249904s (0.165570s in 7 GCs)"
> 
> , in a build with the CLAGS and gtk toolkit like you said.  That's in
> agreement with your timing, given my slightly slower machine.

I don't believe these results.  It's night impossible for a -O2
optimized program to be 5 times faster than a -Og optimized.  And
benchmark.el doesn't seem to be so different from time-it, modulo the
function call.  Moreover, Alan's method does time redisplay, whereas
Dmitry's method does not.

So there's some other factor at work here that explains the
difference.

> I think it does explain the difference.  I repeated my previous timing,
> which was 0.18s on an optimised build, and it came out at 1.16s.  That's
> a factor of 6 different.  CFLAGS='-Og -g3' is a slow build.

It cannot be that slow.  Especially since some I/O is involved, and
you also measure redisplay.  More detailed data would be necessary to
explain the difference.