emacs-async

That "99% of standard usage" is the kicker, isn't it? The greybeards who opposed multithreading since the beginning tend to say that the remaining 1% of use cases is best done in an external process, ideally not even written in Emacs Lisp, so that Vimmers and the rest of the free software community can benefit. The GNU Global you mention embodies that ideal exactly. I suppose if you still want that program to be written with Emacs Lisp, you could use async.el (https://github.com/jwiegley/emacs-async/) and there's finally an use-case for the threads: it'll be relatively safe to run those 16 threads only in the external Emacs-process.

How timely - I, too, got frustrated by the fact that org-babel src block evaluation is synchronous, so I built ob-async [1]. Rather than target a specific babel language, it aims to support any flavor of src block. It uses jwiegley's async [2] to execute the block in a second Emacs process and then inserts the results in the buffer when complete. There are still some rough edges (no :session support, for example), but it's worked well for my somewhat limited use cases so far. [1] https://github.com/astahlman/ob-async [2] https://github.com/jwiegley/emacs-async