Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!husc6!necntc!ames!lll-tis!lll-lcc!lll-winken!csustan!csun!aeusesef From: aeusesef@csun.UUCP Newsgroups: comp.unix.wizards Subject: Re: Free Software Foundation (was: R Message-ID: <782@csun.UUCP> Date: Thu, 1-Oct-87 15:54:29 EDT Article-I.D.: csun.782 Posted: Thu Oct 1 15:54:29 1987 Date-Received: Sat, 3-Oct-87 09:03:41 EDT References: <9510@brl-adm.ARPA> Reply-To: aeusesef@csun.UUCP (Sean Eric Fagan) Organization: California State University, Northridge Lines: 28 Keywords: Copy-on-write Unix Cray In article <9510@brl-adm.ARPA> aglew%xenurus@gswd-vms.Gould.COM (Andy Glew) writes: >>Doug Gwyn : >> >>>preston@felix.UUCP (Preston Bannister): >>>The fork call is going to be awefully expensive, as a copy of the >>>entire data space of the parent will be made. >> [some comments about cow and using it for the current topic] >(3) COW depends on precise interrupts, as does any type of page faulting. > Big machines like Cray don't have virtual memory; Since a Cray doesn't have cirtual memory, you can't do a COW at all. Copying the entire address/data space of the parent isn't all that painfull, either, unless you only have one process running. Cray's, like CDC 6600 etc. machines, have hardware that can shuffle memory around VERY quickly. In fact, an easy way to copy the parent is to: swap parent out to disk (this takes little CPU time); load wherever you wish, and then load the child wherever you wish. Very simple, quick, and the CPU doens't have to do much work (although te PPU does...). >Andy "Krazy" Glew. Gould CSD-Urbana. USEnet: ihnp4!uiucdcs!ccvaxa!aglew ----- Sean Eric Fagan Office of Computing/Communications Resources (213) 852 5742 Suite 2600 1GTLSEF@CALSTATE.BITNET 5670 Wilshire Boulevard Los Angeles, CA 90036 {litvax, rdlvax, psivax, hplabs, ihnp4}!csun!aeusesef