undo mechanism (was Re: turning off (or enhancing) a couple of new features)

[Joe Corneli]

      It seems to mostly have to do with shell buffers, commands that
      generate lots of output, and yes, editing/manipulating large (I
      wouldn't say huge) text files.

   If you kept `undo-outer-limit' at its default value of 3M, I would
   suspect problems in undo handling by processes.  (On the other hand,
   if you handle 4M files, the warning is not surprising.)  When this
   first came up we noticed and dealt with several bugs related to how
   timers handled undo.  I told Richard then that I was worried that
   there might be similar problems with processes.

   What shell commands are involved and are there reproducible examples?

I think that running ogg123 on a .ogg file in the shell will do it.  I
think running wget asynchronously to download a big file will do it.

Just anything really verbose.

The messages also seem to appear when I edit (using emacs lisp) a file
that is only ~700k in size (at the end of the day), but in which I'm
doing a lot of programmed manipulation.

Maybe also when editing thousands of smaller text files (even though
they are killed off right away after the editing is done)?

To deal with this, when I'm doing a lot of programmatic editing, I
just turn undo off.

(defadvice set-buffer (around no-undo activate)
  "Disable undo for every new buffer."
    ad-do-it
    (buffer-disable-undo))

I could post the particular code in question if you're interested (I
was actually planning to release it fairly soon anyway).