Re: bug-reference-prog-mode slows down CC Mode's scrolling by ~7%

[Eli Zaretskii]

> Date: Sat, 4 Sep 2021 15:32:57 +0000
> From: Alan Mackenzie <acm@muc.de>
> Cc: Eli Zaretskii <eliz@gnu.org>, emacs-devel@gnu.org
> 
> > Maybe to speed things up, another option is to grow the chunk size
> > a bit.
> 
> Maybe.  An advantage of a small chunk size is that fontifying a single
> screen can be done with a maximum 499 bytes "inefficiency" off the end
> of a screen.  If we were to increase jit-lock-chunk-size to, say 2000,
> more of the next screen would be getting fontified, perhaps wastefully.
> I don't know how important this is.  Maybe I should try it.
> 
> Indeed.  With jit-lock-chunk-size at 2000, time-scroll on xdisp.c takes:
> 
> (current code): 16.4s
> (new proposed code): 16.1s
> 
> ..  This speed up may well be particular to CC Mode.
> 
> Let's try jit-lock-chunk-size at 8000:
> 
> (current code): 15.1s
> (new proposed code): 15.1s
> 
> ..  So, yes, it would seem a larger chunk size is advantageous for CC
> Mode.

How large (in lines and columns) is your window?  The above numbers
are only meaningful with the window size.