From owner-freebsd-questions Thu Aug 29 16:15:49 1996 Return-Path: owner-questions Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id QAA14801 for questions-outgoing; Thu, 29 Aug 1996 16:15:49 -0700 (PDT) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by freefall.freebsd.org (8.7.5/8.7.3) with ESMTP id QAA14781 for ; Thu, 29 Aug 1996 16:15:42 -0700 (PDT) Received: (from root@localhost) by dyson.iquest.net (8.7.5/8.6.9) id SAA00793; Thu, 29 Aug 1996 18:14:24 -0500 (EST) From: "John S. Dyson" Message-Id: <199608292314.SAA00793@dyson.iquest.net> Subject: Re: FreeBSD 2.1.0 CRASH! To: scott@statsci.com Date: Thu, 29 Aug 1996 18:14:24 -0500 (EST) Cc: dwhite@resnet.uoregon.edu, Eric.Berenguier@sycomore.fr, questions@FreeBSD.ORG In-Reply-To: from "Scott Blachowicz" at Aug 29, 96 11:47:07 am Reply-To: dyson@FreeBSD.ORG X-Mailer: ELM [version 2.4 PL24 ME8] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-questions@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > the swap area is the total virtual address space or just an extension of > the RAM (i.e. > > sizeof(virtual addr space) == sizeof(RAM)+ sizeof(swap) > > instead of just > > sizeof(virtual addr space) == sizeof(swap) > > ). If on a system doing the latter, 20Mb is definitely not enough swap for > 16Mb of RAM. I don't really know which category FreeBSD falls into (it > could be that any recent OS uses the former method...I don't know). > FreeBSD uses the latter -- therefore it is not necessary or desirable to free swap space everytime pages are paged in. (The only time that we do it is when memory (total virtual address space free) is low.) IMO, it is best to keep swap space in contiguous chunks. I guess that it would be possible to do so if all paging in operations read an entire chunk, but anyway disk is very very cheap. (20MBytes of extra disk calculates out to be about $5 to $10, maybe less, maybe more...) John