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

From: Eli Zaretskii
Subject: Re: new emacs24 settings (was: Re: Performance problems (CPU 100%) with NULs in files)
Date: Fri, 23 Sep 2011 20:58:54 +0300

> Date: Sat, 24 Sep 2011 01:44:03 +0800
> From: Le Wang <>
> Cc:
> > > 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

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

> > 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.

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