Re: profiling latency in large org-mode buffers (under both main & org-fold feature)

[Ihor Radchenko <yantar92@gmail.com>]

Max Nikulin <manikulin@gmail.com> writes:

>> +;; the same purpose.  Overlays are implemented with O(n) complexity in
>> +;; Emacs (as for 2021-03-11).  It means that any attempt to move
>> +;; through hidden text in a file with many invisible overlays will
>> +;; require time scaling with the number of folded regions (the problem
>> +;; Overlays note of the manual warns about).  For curious, historical
>> +;; reasons why overlays are not efficient can be found in
>> +;; https://www.jwz.org/doc/lemacs.html.
>
> The linked document consists of a lot of messages. Could you, please, 
> provide more specific location within the rather long page?

There is no specific location. That thread is an old drama unfolded when
intervals were first implemented by a third-party company (they were called
intervals that time). AFAIU, the fact that intervals are stored in a
list and suffer from O(N) complexity originates from that time. Just
history, as I pointed in the comment.

FYI, a more optimal overlay data structure implementation has been
attempted in feature/noverlay branch (for example, see
https://git.savannah.gnu.org/cgit/emacs.git/commit/?h=feature/noverlay&id=8d7bdfa3fca076b34aaf86548d3243bee11872ad).
But there is no activity on that branch for years.

Best,
Ihor