Re: Emacs design and architecture. How about copy-on-write?

[Eli Zaretskii]

> Date: Wed, 20 Sep 2023 22:22:53 +0300
> Cc: yantar92@posteo.net, acm@muc.de, incal@dataswamp.org, emacs-devel@gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> Okay, here's a question that I should have started with: what kind of 
> parallelism are we discussing?

Not clear yet.

> A) Initially I figured it's the ability to render a single window using 
> multiple threads of execution. It's the one my mind immediately went to, 
> but might the hardest of the bunch because it would require us to 
> parallelize the display algorithm for a single buffer.
> 
> B) Being able to render different windows/buffers fully in parallel. I 
> think that requires us to implement concurrent Lisp threads, at the very 
> least. That's likely to drag down the single-thread performance (though 
> it's hard to predict by how much).
> 
> C) Having only a separate (not Lisp) thread for GUI might help with 
> responsiveness somewhat (by throttling certain expensive windows down, 
> for example), but overall it might not improve by much. Though I suppose 
> it could render in parallel those buffers which don't need to run Lisp 
> to display? Anyway it would be synchronized to the one Lisp interpreter.

All of the above need some fundamental issues to be resolved to enable
any of them.  I think at this point it is best to try to look for
solutions for those fundamental issues, and only after that see which
of the above are possible and worth our while.