Most processes that fork know that they are going to fork. Therefore they can pre-fork very early, so as to commit the memory when they only have a bare minimum

Most processes that fork know that they are going to fork. Therefore they can pre-fork very early, so as to commit the memory when they only have a bare minimum allocated. Your typical daemon does this anyway. Some other type of process like an interpreter that can subshell out doesn't know how big the allocation is going to get, would have to pre-fork early on. In this way, you wouldn't "need" overcommit and the Linux horror of OOM. Well, perhaps you don't need it so badly. Programs that use sparse arrays without mmap() probably need overcommit or lots of swap.