bug#71644: 30.0.50; Severe slowdown in larger files with markers beginning in emacs 29+

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

One other thing I notice: If I use Emacs-29 but with Org-9.5.5 (i.e., the
version included in Emacs-28.2) the recipe doesn't show the slowdown.

There's still a good chance that the slow behavior is due to
chars<->bytes conversion (there's no doubt that this code's performance
can be quite poor), but I suspect the reason for the change of behavior
between Emacs-28 and Emacs-29 lies in Org rather than in Emacs's C code.
If someone more familiar with the changes that occurred in Org around
that time could try and track down the specific change that triggers the
problem, that would be appreciated.


        Stefan