There is a lot of great info about operating systems - specifically ring0 vs ring1 for the context switch overhead.
Meanwhile, only Python and Ruby had GILs. Async/await became popular through JavaScript and C#. Now very popular in Rust as well. None of these runtimes have a GIL.
Async/await or Fibers (C++, Go, Java 21) are entirely about context switching overhead.
To be fair, while typical JS implementations do not have a GIL, it's usually unnecessary due to the runtime being single-threaded.
In case anyone else is curious when the above languages grew this feature:
(F# piloted this in the 1.x days, back in 2009 or earlier.)
It seems like C# developed this feature first in 5.0 in 2012, followed by JS (Dec 2016 in Chrome, widely supported across other major browsers within a few months). Python 3.7 came out in 2018, Ruby 3.0 came out in 2020.
Async/await landed in C++20 via coroutines, and Java 21 landed last month. Rust grew this feature in 2018, which landed in the stable channel in 1.39 (Nov 2019). Golang has had goroutines / channels since day 1.
Yeah, "we avoid a GIL because we don't offer threads at all" is, like pre-1.9 Ruby's, "we don't have a GIL because are threads are 1:N green threads" both technically "no GIL" but also worse for thread-based parallelism, then "we have native threads, but there is a GIL, which native code can release".
> Ruby 3.0 came out in 2020.
Ruby 3.0 doesn't have async/await, though. There's a third-party colorless Async gem, and built in constructs (that require a scheduler implementation) for lower-friction asynchronous programming (async as an approach has been popular for Ruby for quite a while), but not with async/await syntax in either case.
(I haven't written anything in Ruby in roughly a decade, so I'm happy to defer to anyone who's actually followed the language the whole time)
That's fair. I had skimmed and found some reference to the async gem relying on Fiber::SchedulerInterface which was introduced in 3.0, although it apparently existed back in 2017.
There's similarly the async-await gem by the same org (also first released in 2017), which at least partially supports that syntax. But in either case, it's not a native language feature.
P.S. C++ async is entirely about running on embedded hardware, not about "overhead".
P.P.S. All garbage-collected languages have a GIL of some sort. This is the real reason GC languages aren't used in systems programming, not GC pauses.