From owner-freebsd-current@FreeBSD.ORG Thu May 27 07:09:45 2004 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 507B316A4DE for ; Thu, 27 May 2004 07:09:45 -0700 (PDT) Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8E43E43D31 for ; Thu, 27 May 2004 07:09:44 -0700 (PDT) (envelope-from ticso@cicely12.cicely.de) Received: from cicely5.cicely.de (cicely5.cicely.de [IPv6:3ffe:400:8d0:301:200:92ff:fe9b:20e7]) (authenticated bits=0) i4RE8HDv082926 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=OK); Thu, 27 May 2004 16:08:21 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (cicely12.cicely.de [IPv6:3ffe:400:8d0:301::12]) by cicely5.cicely.de (8.12.10/8.12.10) with ESMTP id i4RE7lUi041995 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 27 May 2004 16:07:48 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (localhost [127.0.0.1]) by cicely12.cicely.de (8.12.11/8.12.11) with ESMTP id i4RE7lSB019026; Thu, 27 May 2004 16:07:47 +0200 (CEST) (envelope-from ticso@cicely12.cicely.de) Received: (from ticso@localhost) by cicely12.cicely.de (8.12.11/8.12.11/Submit) id i4RE7jHY019025; Thu, 27 May 2004 16:07:45 +0200 (CEST) (envelope-from ticso) Date: Thu, 27 May 2004 16:07:45 +0200 From: Bernd Walter To: Ivan Voras Message-ID: <20040527140744.GW63479@cicely12.cicely.de> References: <40B4ECC8.50808@fer.hr> <20040526202849.GA37162@freebie.xs4all.nl> <40B519DA.7000708@fer.hr> <20040527120819.B8434@gamplex.bde.org> <40B5DE26.4040901@fer.hr> <20040527124512.GV63479@cicely12.cicely.de> <40B5E66F.7000507@fer.hr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <40B5E66F.7000507@fer.hr> X-Operating-System: FreeBSD cicely12.cicely.de 5.2-CURRENT alpha User-Agent: Mutt/1.5.6i X-Spam-Status: No, hits=-4.9 required=3.0 tests=BAYES_00 autolearn=ham version=2.63 X-Spam-Report: * -4.9 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on cicely12.cicely.de cc: ticso@cicely.de cc: current@freebsd.org Subject: Re: Softupdates a mount option? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: ticso@cicely.de List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 May 2004 14:09:45 -0000 On Thu, May 27, 2004 at 03:00:31PM +0200, Ivan Voras wrote: > Bernd Walter wrote: > > >>>It makes sense to never enable soft updates on a memory drive, since soft > >>>updates uses extra CPU cycles to try to speed up i/o to real drives (and > >> > >>Then maybe the default should be changed? > >> > >>From 'man mdmfs': > >> By default, mdmfs creates a swap-based (MD_SWAP) disk with > >> soft-updates > >> enabled and mounts it on mount-point. > > > > > >swap != ram > >SU makes perfectly sense for swap backed md drives. > > I always thought the "swap backed" meant the memory is allocated from the > same pool as for userland applications, e.g. they only get swapped out if > memory is scarce. Is this wrong? You are right, but md(4) doesn't know about the filesystem and therefor can't know which blocks have content to keep and which are unused. SU now allows files that are deleted quite fast to never touch the block device and md never need to write those blocks into swap storage as they never got dirty. The memory can be reclaimed without the need for a physical write. The story is different with type malloc where there is not physical device and we only have ram. -- B.Walter BWCT http://www.bwct.de bernd@bwct.de info@bwct.de