From owner-freebsd-current@FreeBSD.ORG Fri Apr 11 01:38:55 2003 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E5E9B37B404 for ; Fri, 11 Apr 2003 01:38:55 -0700 (PDT) Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16]) by mx1.FreeBSD.org (Postfix) with ESMTP id CCE8243FA3 for ; Fri, 11 Apr 2003 01:38:54 -0700 (PDT) (envelope-from bde@zeta.org.au) Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246]) by mailman.zeta.org.au (8.9.3/8.8.7) with ESMTP id SAA21432; Fri, 11 Apr 2003 18:38:48 +1000 Date: Fri, 11 Apr 2003 18:38:47 +1000 (EST) From: Bruce Evans X-X-Sender: bde@gamplex.bde.org To: Lucky Green In-Reply-To: <20030410230113.M81717@pakastelohi.cypherpunks.to> Message-ID: <20030411182925.A3507@gamplex.bde.org> References: <20030410230113.M81717@pakastelohi.cypherpunks.to> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII cc: freebsd-current@freebsd.org Subject: Re: options NO_SWAPPING, still wants swap X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Apr 2003 08:38:56 -0000 On Thu, 10 Apr 2003, Lucky Green wrote: > I compiled a kernel with "options NO_SWAPPING", yet CURRENT still > attempts to allocate swap space: NO_SWAPPING has nothing to do with not allocating swap space. It prevents swapping of upages and stack pages only. Unfortunately, NOTES' description of NO_SWAPPING says that it disables swapping without explaining what swapping is (it is just swapping of upages and stack, and has nothing to do with generic VM paging). NO_SWAPPING is documented mainlly in the commitlog for the change that added it: %%% RCS file: /home/ncvs/src/sys/vm/vm_pageout.c,v Working file: vm_pageout.c head: 1.228 ... ---------------------------- revision 1.66 date: 1996/02/22 10:57:37; author: davidg; state: Exp; lines: +20 -12 Add a "NO_SWAPPING" option to disable swapping. This was originally done to help diagnose a problem on wcarchive (where the kernel stack was sometimes not present), but is useful in its own right since swapping actually reduces performance on some systems (such as wcarchive). Note: swapping in this context means making the U pages pageable and has nothing to do with generic VM paging, which is unaffected by this option. Reviewed by: ---------------------------- %%% > As a result, everything from make to cp to httpd (on a server with no load > other than random search engine visits) sometimes fails. The machine has > 1GB of RAM, all seen by FreeBSD. Since I ran the same processes on a > machine with 128MB of RAM and 256MB of swap without ever running out of > memory, something seems broken with FreeBSD's use of memory when options > NO_SWAPPING is chosen. I always use it, with and without actual swap, and have had no problems from it. Bruce