Re: A significant slowdown calling font-lock-fontify-buffer from a hook

[Eli Zaretskii <eliz@gnu.org>]

> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Tue, 16 Jul 2013 20:26:56 +0200
> Cc: Emacs developers <emacs-devel@gnu.org>
> 
> > Is the "calling from a hook" an important part of this issue?
> 
> Doing
> 
>   emacs -Q src/xdisp.c
>   M-x font-lock-fontify-buffer <RET>
> 
> I don't see the slowdown.

First, you need to turn off global-font-lock-mode before visiting
xdisp.c.  Second, if you do turn off global-font-lock-mode, invoking
font-lock-fontify-buffer will fail in Emacs 24.3.  You need to do
something like this instead:

  M-: (let ((c-standard-font-lock-fontify-region-function 'font-lock-default-fontify-region)) (font-lock-fontify-buffer)) RET

If I do this in Emacs 24.3 and in the current trunk, I do see a
significant slowdown: it takes 18 sec with 24.3, and 72 sec with the
current trunk.

So I think the invocation from hook is not a factor here, which is a
Good Thing, because debugging this will be much simpler ;-)