Subject: bug#15555: Re: bug#15555: 24.3; Bidirectional display very slow with long lines

From: Dmitry Antipov <[email-masked]>
Date: Tue, 18 Feb 2014 16:43:52 +0400

On 10/09/2013 08:59 PM, Eli Zaretskii wrote:

> IOW, this is bug #13675, which has nothing to do with bidi.  As long
> as the basic display algorithms are not changed to fix that bug, I'm
> going to claim that bidi is not the issue here.

Hm... I have two files, with 2000 and 4000 first chars extracted from the beginning
of the monster string from http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15555#5.

The following function:

(defun bug15555 ()
   (interactive)
   (while (not (eobp))
     (right-char 1)
     (redisplay)
     (sleep-for 0.01)))

runs smoothly over 2000.txt, but painfully slow over 4000.txt.  The latter
case also shows the very pathological profile with ~25% CPU spent in memcpy.

Are you sure that bidi_copy_it doesn't add one more bottleneck to the whole
stuff?

Dmitry