[IsTom]

> One is that fork() is by definition a very costly operation

Isn't process creation much slower on Windows (not using fork) than forking on Unix-likes?

[tsimionescu]

It is, but there are many other differences between Unix and Windows processes than just fork() VS CreateProcess().

Even disregarding this, the actual fork() syscall has had many hundreds of dev hours poured into it to implement the costly semantics (copy all resources) in an efficient way for the common use case (copy-on-write semantics).