On paged systems fork() is usually reasonably fast, but for CGI you do fork()+exec() and while exec() is also reasonably fast, the stuff that the happens in chi

On paged systems fork() is usually reasonably fast, but for CGI you do fork()+exec() and while exec() is also reasonably fast, the stuff that the happens in child process between it's start and entry into main() (ie. dynamic linking, libc initialization) is somewhat on the slower side. (Not to mention interpreter startup for interpreted languages)