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Re: Display performance degradation

From: Kenichi Handa
Subject: Re: Display performance degradation
Date: Fri, 18 Dec 2009 14:46:14 +0900

In article <address@hidden>, Jan Djärv <address@hidden> writes:

> How much is extremely, do you have figures?  I haven't noticed any change, 
> maybe it only manifests itself for certain locales.

Actually, "extremely" was a too strong word.  The following test:

  (switch-to-buffer "TUTORIAL.ja")
  (goto-char (point-min))
  (benchmark-run 1
      (sit-for 0)
    (while (condition-case nil
               (progn (scroll-up) (sit-for 0))
             (error nil)))))

shows that the latest Emacs is about 1.45 times slower (I
turned off all of tool-bar-mode, menu-bar-mode,
scrool-bar-mode, line-number-mode).

But, the perceived difference is much more.

With the previous code, when I type C-v in TUTORIAL.ja
buffer, the upper and middle part of the window (40 lines)
is updated almost instantly, and I notice the redrawing
process only at the bottom few lines.  So, I feel no
frustration.  But, with the current code, with C-v, I see
that the middle part is still under construction.  It's a
big difference in human's perception.

Kenichi Handa

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