Re: new emacs24 settings (was: Re: Performance problems (CPU 100%) with NULs in files)

[Eli Zaretskii]

> Date: Sat, 24 Sep 2011 01:44:03 +0800
> From: Le Wang <l26wang@gmail.com>
> Cc: help-gnu-emacs@gnu.org
> 
> > > This helped me with my slow scroll issues.  Holding down arrow on a fully
> > > maximized frame on a 1080p monitor was spiking my duo-core CPU to 20-25%.
> > > Scrolling text.  50% of one CPU.  Just to scroll text.
> >
> > Scrolling how (by what commands)?
> 
> 
> next-line

What was the value of line-move-visual?  Under the default non-nil
setting, next-line is pretty expensive.

> >  What kind of text?  What was the major mode in that buffer?
> 
> emacs-lisp large file

How large?

Does it matter whether you are close to the file's beginning or to its
end?

Does anything change if, after visiting the file, you first type

  M-: (font-lock-default-fontify-buffer) RET

and only then try scrolling?

> I also use full font-lock salad colors with "Consolas" font on Windows.
> Also I use several minor-modes that add pre or post-command-hooks.

If you remove those pre/post-command hooks, does the scrolling speed
improve significantly?  Can you find a hook that has the most profound
effect?

> > Does it behave better if you set redisplay-dont-pause to a non-nil
> > value?  This will be the default in Emacs 24.
> >
> 
> It's not making a noticeable difference.

With or without bidi-display-reordering?  I asked about its effect
when bidi-display-reordering is left at its default t value.

> To be clear, I get perfectly smooth scrolling now with bidi-display-ordering
> set to nil.  And my CPU usage doesn't exceed 12% while scrolling.  So things
> are good now.

I encourage you to provide more details about this slowdown, so that
bidirectional display in Emacs 24 could be sped up.  Turning off
bidi-display-reordering is not a supported mode, that is an internal
variable that is not designed to be toggled by users.