bug#6964: 23.2; revert-buffer takes 60 times longer than initial read

[Daniel B.]

Reverting a file (executing revert-buffer) takes much (e.g., 60 times)
longer than reading the file initially.

For a 30MB file that originally took about 3 seconds to load, executing
revert-buffer took 179 seconds.




In GNU Emacs 23.2.1 (i386-mingw-nt5.1.2600)
 of 2010-05-08 on G41R2F1
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/xpm/include'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  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: ENU
  value of $XMODIFIERS: nil
  locale-coding-system: cp1252
  default enable-multibyte-characters: t

Major mode: Fundamental

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

Recent input:
s <return> C-y <return> y e s <return> x b l o <tab>
C-g C-x b l <backspace> L o <tab> <return> <escape>
x t a g s <backspace> <backspace> <backspace> <backspace>
v i s <tab> i <tab> t <tab> <return> <return> y e s
<return> y C-n <escape> x r e p e <tab> - m a <return>
s e a <return> y <return> <escape> x s h e l l <return>
C-r > A G S C-e <return> <escape> x r e p e <tab> m
a <backspace> <backspace> - a <backspace> m a <return>
s e a <return> y <return> y e s <return> <help-echo>
<help-echo> C-x 2 C-x C-g C-x b * c <tab> <return>
<escape> > <S-escape> < C-s < < C-n C-s 3 d C-s C-s
C-s C-s C-n C-x o <escape> , <escape> , <escape> ,
<escape> , M-b M-b M-b M-b C-SPC C-e <escape> w <escape>
x t a g s <return> q u e <return> C-y <return> C-y
C-a M-f C-f " I C-d C-d M-f M-f M-f M-f M-f M-b y e
C-d C-d C-e M-b f l C-d C-d <return> C-p <escape> ,
<escape> < <escape> , y C-g <escape> x r e v e r t
<return> y e s <return> <escape> < <escape> , <help-echo>
<help-echo> <help-echo> C-n C-p C-x C-f . <return>
C-x o C-x b <return> C-x o C-s x m l - s c h C-a C-e
f y e s <return> C-x b <return> C-x o C-x k <return>
f y <help-echo> C-x o C-g C-x o C-x k <return> f y
f y <escape> x r e v e t <backspace> r t <return> y
e s <return> <help-echo> <help-echo> <help-echo> <help-echo>
<escape> x r e p o <tab> r <tab> <return>

Recent messages:
Quit [2 times]
Mark set [2 times]
Mark saved where search started
Quit
File L-w3c-xml-schema-comments is large (29MB), really open? (y or n)
Quit
File L-w3c-xml-schema-comments is large (29MB), really open? (y or n)
Quit
File L-w3c-xml-schema-comments is large (29MB), really open? (y or n)
Making completion list...

Load-path shadows:
None found.

Features:
(shadow sort mail-extr message ecomplete rfc822 mml mml-sec
password-cache mm-decode mm-bodies mm-encode mailcap mail-parse rfc2231
rfc2047 rfc2045 qp ietf-drums mailabbrev nnheader gnus-util netrc
time-date mm-util mail-prsvr gmm-utils wid-edit mailheader canlock sha1
hex-util hashcash mail-utils emacsbug dired-aux apropos help-mode view
sh-script executable chistory ansi-color shell mule-util cc-mode
cc-fonts cc-menus cc-cmds etags multi-isearch parse-time vc-cvs
nxml-uchnm rng-xsd xsd-regexp rng-cmpct rng-nxml rng-valid rng-loc
rng-uri rng-parse nxml-parse rng-match rng-dt rng-util rng-pttrn nxml-ns
easymenu nxml-mode nxml-outln nxml-rap nxml-util nxml-glyph nxml-enc
xmltok compile comint ring dired cc-styles cc-align cc-engine cc-vars
cc-defs regexp-opt tooltip ediff-hook vc-hooks lisp-float-type mwheel
dos-w32 disp-table ls-lisp w32-win w32-vars tool-bar dnd fontset image
fringe lisp-mode register page menu-bar rfn-eshadow timer select
scroll-bar mldrag mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
simple abbrev loaddefs button minibuffer faces cus-face files
text-properties overlay md5 base64 format env code-pages mule custom
widget hashtable-print-readable backquote make-network-process multi-tty
emacs)


Daniel