Re: Fwd: Serious performace problems on Windows XP with new(!) GNU Emacs v22 (both patched and unpatched EmacsW32 were tried)

[Richard Stallman]

    So if you could find the reason of this strange difference related to
    (point), then there would be no performace problem with whitespace.

I suspect this has to do with the way overlays are stored -- in two lists,
those before the "center" and those after the "center".
(The center can be any position in the buffer.)

Try adding this before the beginning of the loop:

    (overlay-recenter (point-max))