Some experience with the igc branch

[Óscar Fuentes]

I've using the igc branch for the past weeks. It was mostly Dart/Flutter
development with lsp-dart / lsp-mode enabled, with all its default
features enabled. On top of that, I use the flx completion algorithm.

This setup puts a lot of stress on GC. To illustrate, on master Emacs
after setting garbage-collection-messages to t, one can see that simply
writing a few characters triggers GC several times, each with its
corresponding pause, which may be very noticeable ("uh! that keypress
didn't register... wait, there it is.") The experience is not great.
Quite miserable, I would say. People suggest playing with
gc-cons-threshold (I have mine set to 10'000'000) but those tricks
simply make things a bit less awful.

With igc the pauses are still there, but they much shorter and
predictable, they no longer distract me from thinking on what I'm
writing, which is a huge improvement. I suspect that some of those
pauses are not related to garbage collection (executing code and moving
data also takes time.)

TL/DR: now I enjoy using Emacs with this setup and I'm no longer tempted
to switch to other editors for this type of work.

A big thank you to all involved on this feature.