Gap buffer problem?

[Gerd Möllmann]

Pip Cet via "Emacs development discussions." <emacs-devel@gnu.org>
writes:

> On Tuesday, December 10th, 2024 at 13:39, Óscar Fuentes <ofv@wanadoo.es> 
> wrote:
>> Eli Zaretskii eliz@gnu.org writes:
>> > Maybe so, but why is such a long wait a problem? GC works, and
>> > works well.
>> 
>> Working on certain projects with lsp-mode is a miserable experience due
>> to all the random pauses.
>
> To be fair, part of that may be the gap buffer problem rather than GC.

Could you please tell more about the gap buffer problem?

I've read a little about the tradeoffs between gap buffers, piece
tables, ropes, but I'm wondering if there is something concrete already
known for sure that is a performance problem in Emacs. Maybe a bug that
has been analyzed or something.

(I'm asking because I just recently encountered a performance problem
when adding something to xdisp.c:27339 (with cc-mode, Eglot, Corfu), and
editing there was so slow that it was absolutely no fun, and that on a
an M1 pro. Haven't investigated the reason.)