> I always thought vfork was introduced because > copy-on-write hadn't been invented yet. > > It's the only logical explanation.
no, it was because they chose not to implement copy on write. it had been invented long before that. in fact, i found copy on write at least as easy to do for unix as the grunge required for vfork (and it was more generally useful). on some architectures you need to use copy on reference. their paging data structures might have made it more difficult, i suppose; they had them upside down compared to unix's requirements. vfork also was specified so that if you relied on the sharing except to implement a non-sharing fork, the effect was undefined.
