Messages in this thread | | | Subject | Re: PATCH(?): linux-2.4.4-pre2: fork should run child first | From | John Fremlin <> | Date | 13 Apr 2001 22:08:33 +0100 |
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"Adam J. Richter" <adam@yggdrasil.com> writes:
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> It turned out that the particular unix-like system on which > these benchmarks were taken had a version of fork that did not run > the child first. As it was explained to me then, most of the time, > the child process from a fork will do just a few things and then do > an exec(), releasing its copy-on-write references to the parent's > pages, and that is the big win of copy-on-write for fork() in practice. > This oversight was considered a big embarassment for the operating > system in question, so I won't name it here. > > Guess why you're seeing this email. That's right. Linux-2.4.3's > fork() does not run the child first.
Not always, if I understand correctly. Setting to always is putting policy in kernel in a small way. If an app wants to fork and exec, it should use *vfork* and exec, which is a performance win across many OSs because the COW mappings don't even have to be set up, IIRC.
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