It's a very different paradigm to wrap your head around, but once you grok the NT kernel's approach to I/O (packet based IRPs, inherently asynchronous, thread-a

It's a very different paradigm to wrap your head around, but once you grok the NT kernel's approach to I/O (packet based IRPs, inherently asynchronous, thread-agnostic), and thread scheduling, I/O completion ports are very powerful constructs. The key difference is that I/O completion ports can be used to achieve asynchronous I/O on any underlying object, e.g. files and sockets, and they have this nifty built-in concept of concurrency, such that the kernel can ensure there is always one running thread per CPU core (which is optimal from a scheduling perspective). You can't use file descriptors with epoll/kqueue, and you certainly can't say "ensure every core only has one active thread running". "The key to understanding what makes asynchronous I/O in Windows special is...": https://speakerdeck.com/trent/pyparallel-how-we-removed-the-gil-and-exploited-all-cores?slide=54 https://speakerdeck.com/trent/pyparallel-how-we-removed-the-... "Thread-agnostic I/O with IOCP": https://speakerdeck.com/trent/pyparallel-how-we-removed-the-gil-and-exploited-all-cores?slide=62 https://speakerdeck.com/trent/pyparallel-how-we-removed-the-...