bug#14721: slow scrolling on windows 7

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 26 Jun 2013 18:28:46 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 14721@debbugs.gnu.org
> 
> [Please keep the bug address on the CC list, so this whole discussion
> is archived by the bug tracker.]
> 
> > Date: Tue, 25 Jun 2013 22:42:59 -0500
> > From: Mario Valencia <mariovalspi@gmail.com>
> > 
> > Yes, in any file.
> > 
> > Yes, in any mode.
> > 
> > Yes, with emacs -Q, as I said. It scrolls fine with the scroll bar though,
> > as well as with "emacs -nw".
> 
> What CPU do you have there, and what display?
> 
> Also, can you tell what is the frequency of the keyboard auto-repeat
> rate on that machine?
> 
> In which version of Emacs did this start happening?
> 
> (FWIW, I see no such slowdown on the Windows systems I work on.)

Here's an experiment; let me know what you see on your machine.

 emacs -Q
 C-x C-f xdisp.c RET
 M-x fundamental-mode RET

(Use any other large file if you don't have Emacs sources, which is
where xdisp.c comes from.)

Now lean on the PgDn key, and tell me whether Emacs can keep up.

On my Core i7 machine, Emacs keeps up just fine, and on average a
single processing unit is busy 20%, i.e. there's plenty of spare
processing power left.