Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!uunet!timbuk!shamash!uc!noc.MR.NET!gacvx2.gac.edu!gacvx2.gac.edu!scott From: scott@mcs-server.gac.edu (Scott Hess) Newsgroups: comp.sys.next Subject: Re: 8MB Blues (or M'ma vs VM) Message-ID: Date: 5 Mar 91 20:29:21 GMT References: <1991Mar3.055657.3212@math.ucla.edu> <6863@idunno.Princeton.EDU> Distribution: na Organization: Gustavus Adolphus College Lines: 38 Nntp-Posting-Host: 138.236.10.1 In-reply-to: tvz@phoenix.Princeton.EDU's message of 5 Mar 91 12:26:37 GMTLines: 38 In article <6863@idunno.Princeton.EDU> tvz@phoenix.Princeton.EDU (Timothy Van Zandt) writes: In article <1991Mar3.055657.3212@math.ucla.edu> barry@pico.math.ucla.edu (Barry Merriman) writes: >to avoid these unsightly VM failures, get some more memory. >A total of 20MB RAM would appear sufficient for a single user >(i.e. add 4 x 4MB). Also, remember you'll need to allow >for a bigger swapfile as well on your hard disk. Why does increasing memory increase the required size of the swap file? I heard this mentioned before, but it seems like the opposite should be true. [This may or may not be true for Mach/Unix on the NeXT - it is true for regular Unix, and I'd give odds that it was for Mach/Unix, also] All memory used by processes must have space in the swapfile. This space is allocated when the memory is allocated, needed or not. In this way, you don't have programs run for a couple minutes then die when they are inactive and the swapper attempts to swap some of their data out so that another process can use memory - and there is no room. The generally recommended configuration for swapfiles is to allocate 2x the real memory size for the minimum size of the swapfile (obviously, it can grow to fill the disk it's on, under Mach). You don't have to do this - it's just a recommendation. In general, if you need 20M of memory, you'll probably end up with a 40M swapfile, anyhow. You cannot count on disk space freed up by shrinking the lowater size of the swapfile, because almost certainly you will need it back at some point in the future, anyhow. Later -- scott hess scott@gac.edu Independent NeXT Developer GAC Undergrad "Tried anarchy, once. Found it had too many constraints . . ." "I smoke the nose Lucifer . . . Bannana, banna."