alt Hacker News> OS threads are expensive: an operating system thread typically reserves a megabyte of stack space and takes roughly a millisecond to create.
It's typically less than a hundred kilobytes and (on the systems I've benchmarked using std::thread) it takes 60usec (wall time in userspace) to create and destroy a thread.
Threads have gotten so fast that paying the async function coloring price makes very little sense for most software.
Its the stack space allocated to each thread that prevents you from spawning more than a thousand threads. Strategies like a thread per network connection do not scale.