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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!news.cs.su.oz.au!metro!metro!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!news.ececs.uc.edu!news.kei.com!news.mathworks.com!news.sprintlink.net!news-peer.sprintlink.net!arclight.uoregon.edu!super.zippo.com!zdc!szdc!szdc-e!news From: "John S. Dyson" <dyson@freebsd.org> Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: 2.2 GAMMA 2/5 results in SWAP FULL? Date: Wed, 12 Feb 1997 11:01:47 -0500 Organization: John S. Dyson's home machine Lines: 28 Message-ID: <3301E96B.41C67EA6@freebsd.org> References: <m267zzxceb.fsf@golfgod.raleigh.ibm.com> <5dqqo2$bhf@bofh.noc.best.net> <5dritf$a1j@dfw-ixnews8.ix.netcom.com> <3301E04A.41C67EA6@halcyon.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (X11; I; FreeBSD 3.0-CURRENT i386) Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:35609 Dave DeLaune wrote: > > After switching from Linux to FreeBSD :) I was surprised at the > differences in swap sizes as well. However I have found that > FreeBSD when given a lot of swap space to work with is more responsive > than Linux under the same conditions. Some unices require more swap and > manage it better. The AIX CAD box I use at work has 128 Megs of ram and > 256 Megs of swap. > David Greenman and I wrote the paging algorithm for FreeBSD, and the basic reason that we allow the code to use swap space aggressively is that the cost of disk is much cheaper than the cost of RAM. In order for RAM to be used more effectively, we readily push unused pages out. It doesn't make sense to me to conserve disk space at $100/GB (for larger IDE drives) compared to $4000/GB for RAM. Resisting paging out unused pages leads to less efficient utilization of memory resources. Instead of swap, for example, we could free text pages preferentially. If those text pages are used more than the dirty data pages that are in disuse, there will be unnesessary paging. If RAM ever becomes cheaper than disk, then I would be willing to revise the paging policy :-). John dyson@freebsd.org