A very interesting slide deck comparing sync and async IO

[Brad Anderson via Digitalmars-d]

On Thursday, 3 March 2016 at 17:31:59 UTC, Andrei Alexandrescu 
wrote:
> https://www.mailinator.com/tymaPaulMultithreaded.pdf
>
> Andrei

Related to this, I watched a talk about user-level threads by 
another Google engineer awhile back (also named Paul but not the 
same person).

https://www.youtube.com/watch?v=KXuZi9aeGTw

It's been awhile so I may have this a bit wrong but as I remember 
it the gist was that OSes don't have enough information for 
efficient scheduling and context switching of threads but if the 
OS lets the application handle it the context switching cost 
drops significantly (down to roughly 200ns).

I came across it while following some Rust development which was 
a very interesting read:
https://mail.mozilla.org/pipermail/rust-dev/2013-November/006550.html

It's a bit over two years old now so I'm not sure what path Rust 
took.