Emacs 21.2 - Garbage collector frenzy :-)

[pinard@iro.umontreal.ca (François Pinard)]

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In GNU Emacs 21.2.1 (i586-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2002-04-12 on titan
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: POSIX
  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: fr_CA.ISO-8859-1
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

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

This is a difficult bug to report, and in fact, I am asking for help about
how to get useful information to report, yet without using too much of my
free time trying to understand the conditions behind the problem.  Not easy.

The problem is that, at regular intervals (maybe once every fifteen
minutes or so, I did not precisely timed it), Emacs suddenly starts
burning CPU solidly for about 20 seconds, not responding to commands,
and in particular, not responding to `C-g's.  This occurs spontaneously,
and even when I do not actually use Emacs (I'm not typing in this window).
Then, everything comes back to normal, and commands accumulated while
Emacs was burning CPU then execute in a row.  I thought about doing `(setq
garbage-collection-messages t)', and the minibuffer does display "Garbage
collecting..." and "Gargabe collecting...done" maybe 30 times in a row,
each time those CPU frenzies occur. :-)

I tried using a bare Emacs (no `.emacs') and the problem does not occur,
but then, Emacs is not very usable for me in practice.  I progressively
re-inserted sections of my `.emacs', waiting half an hour after each excerpt
to see if the problem seems to be there or not.  Since I have a rather big
`.emacs' setup, this sums up to a many, many hours, and I stopped trying
to get clues after a few days, as I need a full customised Emacs to work
effectively, and cannot let me stop or crawl for many days.  But I do not
see what other technique I could use to get clues more efficiently.

This is with Emacs 21.2 that I thought about checking if the problem is
related to garbage collection, but I remember having observed such CPU
loops in the latest pretest before 21.2, without much to say about them at
the time.  Not that I have so much more to say now...  How could I proceed
towards better reporting the problem?  (the problem occurred twice while
I was composing this message, so it is more frequent than I thought).


Recent input:
C-s C-s C-s C-s C-a C-p C-e C-p <return> C-a C-x g 
g C-n C-k C-p C-e <return> r e t u r n SPC c o m m 
o n . E q ( n o d e [ 1 ] , SPC c o m m o n . V e r 
b a t i m ( ' 0 ' ) ) C-n C-a C-SPC C-n C-n C-n C-n 
C-w M-x e m a c s - b u g <return> <backspace> <backspace> 
<backspace> <backspace> <backspace> <backspace> <backspace> 
<backspace> <backspace> r e p o r <tab> <return>

Recent messages:
/home/pinard/fpub/topy/Topy/scmtopy.py clean
Wrote /home/pinard/fpub/topy/Topy/scmtopy.py
Mark set [2 times]
Closes block: ...def f_member(self, node):
Mark set [3 times]
Auto-saving...done
Mark set
Mark saved where search started
Mark set [2 times]
Loading emacsbug...done

-- 
François Pinard   http://www.iro.umontreal.ca/~pinard