bug#4123: 23.1.50; Using Emacs on files with very long lines makes it sluggish

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the [email protected] mailing list.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

1. I start Emacs using "emacs -Q".
2. I find-file to something which doesn't exist, to get a buffer in
fundamental-mode.
3. M-1 M-0 M-0 M-0 M-0 M-0 M-0 A (insert a million As)
4. M-> (end-of-buffer)
5. C-p (previous-line)
6. Watch Emacs take a few seconds to figure out where to put point.

If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
/home/deniz/usr/share/emacs/23.1.50/etc/DEBUG for instructions.


In GNU Emacs 23.1.50.4 (i686-pc-linux-gnu, GTK+ Version 2.16.5)
 of 2009-08-04 on stalin
Windowing system distributor `The X.Org Foundation', version 11.0.10603000
configured using `configure  '--prefix=/home/deniz/usr' '--without-jpeg''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.utf8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
C-n C-n C-n C-n C-n C-n C-n M-> C-p C-e C-p C-p M-<
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-v C-n C-n C-n C-n C-n C-n
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-v C-v C-v
C-v C-v C-v C-v C-v C-v C-v C-n C-n C-n C-n C-v C-v
C-v M-> C-4 C-p C-n C-n C-p M-< C-n C-n C-n C-p C-p
C-n C-n C-n C-v C-p C-p C-p C-p C-v C-v C-v C-v C-v
C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v
C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v C-v
C-v C-v C-v C-v C-v C-v C-v C-p C-p C-p M-x r e p o
r t - e m a c s - b u g <return>

Recent messages:
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