Subject: bug#11943: 24.1.50; Emacs unusably slow when looking at large files (bidi support at fault)

From: Dima Kogan <[email-masked]>
Date: Sat, 14 Jul 2012 17:50:51 -0700

I'm observing that when some large text files are loaded, emacs slows to
a crawl. As an example, I have a 14MB file open (with emacs -Q). Every
time I do (next-line) or (previous-line) it takes a few seconds. This is
a > 2GHz Core2 machine, so there's no reason for this to happen. 'M-x
benchmark' says that (previous-line) takes >2s each time. I discovered
that if I do (setq bidi-display-reordering nil) then emacs is snappy
again, with previous-line taking <1ms.

The specific file I'm using to exhibit the bug consists of many repeated
stanzas such as

=========================
{
 {2.222222,2.222222,2.222222,2.2},
 {-2.222222,2.222222,2.222222},
 {-22.222222,22.222222,2.222222}
},
=========================

without the =. Saving a stanza into a file called 'snippet', the 14MB
file can be made with

$ for i in `seq 17`; do cat snippet snippet > xxx; mv xxx snippet; done

Thanks.

In GNU Emacs 24.1.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.4.2)
 of 2012-06-29 on zelenka, modified by Debian
 (emacs-snapshot package, version 2:20120629-1)
Windowing system distributor `The X.Org Foundation', version 11.0.11201902
Configured using:
 `configure '--build' 'x86_64-linux-gnu' '--host' 'x86_64-linux-gnu'
 '--prefix=/usr' '--sharedstatedir=/var/lib' '--libexecdir=/usr/lib'
 '--localstatedir=/var' '--infodir=/usr/share/info'
 '--mandir=/usr/share/man' '--with-pop=yes'
 '--enable-locallisppath=/etc/emacs-snapshot:/etc/emacs:/usr/local/share/emacs/24.1.50/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.1.50/site-lisp:/usr/share/emacs/site-lisp'
 '--without-compress-info' '--with-crt-dir=/usr/lib/x86_64-linux-gnu/'
 '--with-x=yes' '--with-x-toolkit=gtk3' '--with-imagemagick=yes'
 'build_alias=x86_64-linux-gnu' 'host_alias=x86_64-linux-gnu'
 'CFLAGS=-DDEBIAN -DSITELOAD_PURESIZE_EXTRA=5000 -g -O2' 'LDFLAGS=-g
 -Wl,--as-needed -znocombreloc' 'CPPFLAGS=-D_FORTIFY_SOURCE=2''

Important settings:
  value of $LC_ALL: C
  value of $LANG: C
  locale-coding-system: nil
  default enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  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-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
y <down> <down> <down> <down> <down> <down> <up> M-x 
b e n c h m a r k <return> ( p r e v i o u s - l i 
n e ) <return> <help-echo> <help-echo> M-x r e p o 
r t SPC b u g <return>

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
File snippet is large (13.1M), really open? (y or n)  y
Elapsed time: 2.232054s

Load-path shadows:
/usr/share/emacs/24.1.50/site-lisp/cscope/xcscope hides /usr/share/emacs/site-lisp/xcscope
/usr/share/emacs/24.1.50/site-lisp/cmake-data/cmake-mode hides /usr/share/emacs/site-lisp/cmake-mode
/usr/share/emacs/24.1.50/site-lisp/easypg/epg hides /usr/share/emacs/24.1.50/lisp/epg
/usr/share/emacs/24.1.50/site-lisp/easypg/epa-dired hides /usr/share/emacs/24.1.50/lisp/epa-dired
/usr/share/emacs/24.1.50/site-lisp/easypg/epg-config hides /usr/share/emacs/24.1.50/lisp/epg-config
/usr/share/emacs/24.1.50/site-lisp/easypg/epa hides /usr/share/emacs/24.1.50/lisp/epa
/usr/share/emacs/24.1.50/site-lisp/easypg/epa-file hides /usr/share/emacs/24.1.50/lisp/epa-file
/usr/share/emacs/24.1.50/site-lisp/easypg/epa-mail hides /usr/share/emacs/24.1.50/lisp/epa-mail
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-list hides /usr/share/emacs/24.1.50/lisp/org/org-list
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-screen hides /usr/share/emacs/24.1.50/lisp/org/ob-screen
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-protocol hides /usr/share/emacs/24.1.50/lisp/org/org-protocol
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-footnote hides /usr/share/emacs/24.1.50/lisp/org/org-footnote
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-docview hides /usr/share/emacs/24.1.50/lisp/org/org-docview
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-pcomplete hides /usr/share/emacs/24.1.50/lisp/org/org-pcomplete
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-sh hides /usr/share/emacs/24.1.50/lisp/org/ob-sh
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-irc hides /usr/share/emacs/24.1.50/lisp/org/org-irc
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-maxima hides /usr/share/emacs/24.1.50/lisp/org/ob-maxima
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mac-message hides /usr/share/emacs/24.1.50/lisp/org/org-mac-message
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-bibtex hides /usr/share/emacs/24.1.50/lisp/org/org-bibtex
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-asymptote hides /usr/share/emacs/24.1.50/lisp/org/ob-asymptote
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-bbdb hides /usr/share/emacs/24.1.50/lisp/org/org-bbdb
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob hides /usr/share/emacs/24.1.50/lisp/org/ob
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-lilypond hides /usr/share/emacs/24.1.50/lisp/org/ob-lilypond
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-exp-blocks hides /usr/share/emacs/24.1.50/lisp/org/org-exp-blocks
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-icalendar hides /usr/share/emacs/24.1.50/lisp/org/org-icalendar
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-gnuplot hides /usr/share/emacs/24.1.50/lisp/org/ob-gnuplot
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-src hides /usr/share/emacs/24.1.50/lisp/org/org-src
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-w3m hides /usr/share/emacs/24.1.50/lisp/org/org-w3m
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-css hides /usr/share/emacs/24.1.50/lisp/org/ob-css
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-ledger hides /usr/share/emacs/24.1.50/lisp/org/ob-ledger
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-wl hides /usr/share/emacs/24.1.50/lisp/org/org-wl
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mew hides /usr/share/emacs/24.1.50/lisp/org/org-mew
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mks hides /usr/share/emacs/24.1.50/lisp/org/org-mks
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-python hides /usr/share/emacs/24.1.50/lisp/org/ob-python
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-shen hides /usr/share/emacs/24.1.50/lisp/org/ob-shen
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-tangle hides /usr/share/emacs/24.1.50/lisp/org/ob-tangle
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-haskell hides /usr/share/emacs/24.1.50/lisp/org/ob-haskell
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-eval hides /usr/share/emacs/24.1.50/lisp/org/ob-eval
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-rmail hides /usr/share/emacs/24.1.50/lisp/org/org-rmail
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-habit hides /usr/share/emacs/24.1.50/lisp/org/org-habit
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-exp hides /usr/share/emacs/24.1.50/lisp/org/org-exp
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-mscgen hides /usr/share/emacs/24.1.50/lisp/org/ob-mscgen
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-gnus hides /usr/share/emacs/24.1.50/lisp/org/org-gnus
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-plantuml hides /usr/share/emacs/24.1.50/lisp/org/ob-plantuml
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-ascii hides /usr/share/emacs/24.1.50/lisp/org/org-ascii
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-octave hides /usr/share/emacs/24.1.50/lisp/org/ob-octave
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-entities hides /usr/share/emacs/24.1.50/lisp/org/org-entities
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-dot hides /usr/share/emacs/24.1.50/lisp/org/ob-dot
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-latex hides /usr/share/emacs/24.1.50/lisp/org/ob-latex
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-java hides /usr/share/emacs/24.1.50/lisp/org/ob-java
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-indent hides /usr/share/emacs/24.1.50/lisp/org/org-indent
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-table hides /usr/share/emacs/24.1.50/lisp/org/org-table
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-eshell hides /usr/share/emacs/24.1.50/lisp/org/org-eshell
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-org hides /usr/share/emacs/24.1.50/lisp/org/ob-org
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-exp hides /usr/share/emacs/24.1.50/lisp/org/ob-exp
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-keys hides /usr/share/emacs/24.1.50/lisp/org/ob-keys
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-install hides /usr/share/emacs/24.1.50/lisp/org/org-install
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-ref hides /usr/share/emacs/24.1.50/lisp/org/ob-ref
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-id hides /usr/share/emacs/24.1.50/lisp/org/org-id
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-sass hides /usr/share/emacs/24.1.50/lisp/org/ob-sass
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-picolisp hides /usr/share/emacs/24.1.50/lisp/org/ob-picolisp
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-sqlite hides /usr/share/emacs/24.1.50/lisp/org/ob-sqlite
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-xoxo hides /usr/share/emacs/24.1.50/lisp/org/org-xoxo
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-calc hides /usr/share/emacs/24.1.50/lisp/org/ob-calc
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mhe hides /usr/share/emacs/24.1.50/lisp/org/org-mhe
/usr/share/emacs/24.1.50/site-lisp/org-mode/org hides /usr/share/emacs/24.1.50/lisp/org/org
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-docbook hides /usr/share/emacs/24.1.50/lisp/org/org-docbook
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mouse hides /usr/share/emacs/24.1.50/lisp/org/org-mouse
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-html hides /usr/share/emacs/24.1.50/lisp/org/org-html
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-ditaa hides /usr/share/emacs/24.1.50/lisp/org/ob-ditaa
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-ocaml hides /usr/share/emacs/24.1.50/lisp/org/ob-ocaml
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-lisp hides /usr/share/emacs/24.1.50/lisp/org/ob-lisp
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-jsinfo hides /usr/share/emacs/24.1.50/lisp/org/org-jsinfo
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-odt hides /usr/share/emacs/24.1.50/lisp/org/org-odt
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-macs hides /usr/share/emacs/24.1.50/lisp/org/org-macs
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-freemind hides /usr/share/emacs/24.1.50/lisp/org/org-freemind
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-archive hides /usr/share/emacs/24.1.50/lisp/org/org-archive
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-latex hides /usr/share/emacs/24.1.50/lisp/org/org-latex
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-crypt hides /usr/share/emacs/24.1.50/lisp/org/org-crypt
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-emacs-lisp hides /usr/share/emacs/24.1.50/lisp/org/ob-emacs-lisp
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-clojure hides /usr/share/emacs/24.1.50/lisp/org/ob-clojure
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-lparse hides /usr/share/emacs/24.1.50/lisp/org/org-lparse
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-colview hides /usr/share/emacs/24.1.50/lisp/org/org-colview
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-taskjuggler hides /usr/share/emacs/24.1.50/lisp/org/org-taskjuggler
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-matlab hides /usr/share/emacs/24.1.50/lisp/org/ob-matlab
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-faces hides /usr/share/emacs/24.1.50/lisp/org/org-faces
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-table hides /usr/share/emacs/24.1.50/lisp/org/ob-table
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-capture hides /usr/share/emacs/24.1.50/lisp/org/org-capture
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-js hides /usr/share/emacs/24.1.50/lisp/org/ob-js
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-mobile hides /usr/share/emacs/24.1.50/lisp/org/org-mobile
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-agenda hides /usr/share/emacs/24.1.50/lisp/org/org-agenda
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-sql hides /usr/share/emacs/24.1.50/lisp/org/ob-sql
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-special-blocks hides /usr/share/emacs/24.1.50/lisp/org/org-special-blocks
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-beamer hides /usr/share/emacs/24.1.50/lisp/org/org-beamer
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-fortran hides /usr/share/emacs/24.1.50/lisp/org/ob-fortran
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-timer hides /usr/share/emacs/24.1.50/lisp/org/org-timer
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-perl hides /usr/share/emacs/24.1.50/lisp/org/ob-perl
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-R hides /usr/share/emacs/24.1.50/lisp/org/ob-R
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-ctags hides /usr/share/emacs/24.1.50/lisp/org/org-ctags
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-ruby hides /usr/share/emacs/24.1.50/lisp/org/ob-ruby
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-compat hides /usr/share/emacs/24.1.50/lisp/org/org-compat
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-feed hides /usr/share/emacs/24.1.50/lisp/org/org-feed
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-publish hides /usr/share/emacs/24.1.50/lisp/org/org-publish
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-remember hides /usr/share/emacs/24.1.50/lisp/org/org-remember
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-C hides /usr/share/emacs/24.1.50/lisp/org/ob-C
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-vm hides /usr/share/emacs/24.1.50/lisp/org/org-vm
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-datetree hides /usr/share/emacs/24.1.50/lisp/org/org-datetree
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-awk hides /usr/share/emacs/24.1.50/lisp/org/ob-awk
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-plot hides /usr/share/emacs/24.1.50/lisp/org/org-plot
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-scheme hides /usr/share/emacs/24.1.50/lisp/org/ob-scheme
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-attach hides /usr/share/emacs/24.1.50/lisp/org/org-attach
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-lob hides /usr/share/emacs/24.1.50/lisp/org/ob-lob
/usr/share/emacs/24.1.50/site-lisp/org-mode/ob-comint hides /usr/share/emacs/24.1.50/lisp/org/ob-comint
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-inlinetask hides /usr/share/emacs/24.1.50/lisp/org/org-inlinetask
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-clock hides /usr/share/emacs/24.1.50/lisp/org/org-clock
/usr/share/emacs/24.1.50/site-lisp/org-mode/org-info hides /usr/share/emacs/24.1.50/lisp/org/org-info

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils benchmark time-date tooltip ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode register page
menu-bar rfn-eshadow timer select scroll-bar 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 minibuffer loaddefs
button faces cus-face files text-properties overlay sha1 md5 base64
format env code-pages mule custom widget hashtable-print-readable
backquote make-network-process dbusbind dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty emacs)