[dalias]

I have a sequence of tweets here summarizing basic measurements I did on musl's posix_spawn versus fork+exec:

https://twitter.com/RichFelker/status/602313644026761216

There are still plenty of applications that use fork semantically, to keep the same process image in the child, which benefit somewhat from a fast fork. But most places where fork affects performance now are things that are already pessimized by using fork+exec instead of posix_spawn: the shell, make, cgi, etc. (GCC still uses vfork, but GNU make recently switched from vfork to fork because of vfork-related bugs.) Regardless of how fast or slow fork is on midipix (but I expect it to be fairly fast, much faster than cygwin), they would benefit a lot more from just switching to using posix_spawn.

[dalias]

To clarify, the numbers in my tweets are measured on Linux, comparing musl libc's posix_spawn (with CLONE_VM) to plain fork+exec (which should be independent of libc). I just posted the test program on our mailing list: http://www.openwall.com/lists/musl/2015/06/04/1