Path: utzoo!attcan!uunet!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!sunybcs!rutgers!njin!limonce From: limonce@pilot.njin.net (Tom Limoncelli) Newsgroups: comp.arch Subject: Re: vfork (was Re: Paging page tables) Message-ID: Date: 14 Jul 90 18:12:33 GMT References: <920@dgis.dtic.dla.mil> <5830@titcce.cc.titech.ac.jp> Organization: Drew University/NJIN Lines: 33 In article <5830@titcce.cc.titech.ac.jp> mohta@necom830.cc.titech.ac.jp (Masataka Ohta) writes: > As for UNIX, there are three alternatives to treat forking: > 1) An utterly broken implementation where some important system ^^^^^^^ or maybe an "udderly"? > process (such as inetd, ypbind or sendmail) may killed if there > is not enough swap space. I won't say what side I'm on, but at the Jan '90 Usenix a paper was presented on SVR4's implementation of COW. They reached a good solution if you ask me. They implemented COW, but found that each COW is slower than the usual page-in by some huge factor. So, they did some more research (*) and found that when you fork a new shell you almost always COW the same couple of pages immediately. So, on every fork they page in those pages automatically. That avoids (something like) 10-20 COWs. They call the algorithm "bovophobic" because it tries to avoid COWs. The presentation was GREAT. The paper was in the the procedings if you want to read it. -Tom (*) -- Sorry for using that word. It implies "science" and we all know that using scientific analysis to solve a problem is something that NO programmer would get caught doing. That's for those "computer science" types that never get anything done. Right? -- tlimonce@drew.edu Tom Limoncelli tlimonce@drew.uucp +1 201 408 5389 tlimonce@drew.Bitnet "You'd better move ovah limonce@pilot.njin.net ...here comes a supernova" -The B-52's.