Newsgroups: comp.arch Path: utzoo!henry From: henry@zoo.toronto.edu (Henry Spencer) Subject: Re: Paging page tables Message-ID: <1990Jul6.160004.896@zoo.toronto.edu> Organization: U of Toronto Zoology References: <3300142@m.cs.uiuc.edu> <9758@pt.cs.cmu.edu> <58001@bbn.BBN.COM> <5796@titcce.cc.titech.ac.jp> Date: Fri, 6 Jul 90 16:00:04 GMT In article <5796@titcce.cc.titech.ac.jp> mohta@necom830.cc.titech.ac.jp (Masataka Ohta) writes: >If a large process want to fork(), it requires a large amount of virtual >memory space (twice the size of the process). So, if the process almost >used up virtual memory space, the process can not fork(). Copy-on-write >won't help. Nonsense. There need not be any concept of "using up virtual memory space". Virtual memory is *virtual*; only when those pages need to become real do they consume resources. Forking large processes without needing lots more memory/disk just requires an intelligent implementation. Unfortunately, intelligent implementors are scarce. Vfork is an abomination invented by lazy people; the sooner it goes, the better. (Please don't tell me that hardware problems prevented them from implementing copy-on-write; copy-on-access they *could* have done, and it would have been almost as good.) -- "Either NFS must be scrapped or NFS | Henry Spencer at U of Toronto Zoology must be changed." -John K. Ousterhout | henry@zoo.toronto.edu utzoo!henry