Comment by chubot

Yes I think the argument is that Android (and Chrome) could use something like vfork or posix_spawn().

I'm not sure which, if any; I'd like to see an analysis of that... The issue is what kernel state is preserved/shared across the process creation call.

Every process sort of has a "mirror" in kernel memory. The user memory is CoW, and I suppose you also have to choose whether to copy or reference every kernel data structure as well --- open files in FD tables which point to disk/pipes/sockets, locks which seem to be nonsensical, etc.

But probably you can get the "warmup" property without the full semantics of fork(). That is the CoW of user memory is a somewhat separate choice from the kernel data structures.

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As far as the shell .... In the recent linked thread, Ninja uses posix_spawn because it has a simple use of subprocesses: https://news.ycombinator.com/item?id=31743230