From owner-freebsd-questions@FreeBSD.ORG Wed Jan 16 17:28:21 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 94E5D16A41A for ; Wed, 16 Jan 2008 17:28:21 +0000 (UTC) (envelope-from bruce@cran.org.uk) Received: from muon.bluestop.org (unknown [IPv6:2001:41c8:1:548a::2]) by mx1.freebsd.org (Postfix) with ESMTP id 34DE913C442 for ; Wed, 16 Jan 2008 17:28:21 +0000 (UTC) (envelope-from bruce@cran.org.uk) Received: from [IPv6:2a01:348:10f:0:213a:ffc2:e142:33d9] (unknown [IPv6:2a01:348:10f:0:213a:ffc2:e142:33d9]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by muon.bluestop.org (Postfix) with ESMTP id 82C583031E; Wed, 16 Jan 2008 17:28:19 +0000 (GMT) Message-ID: <478E3E98.10001@cran.org.uk> Date: Wed, 16 Jan 2008 17:27:52 +0000 From: Bruce Cran User-Agent: Thunderbird 2.0.0.9 (Windows/20071031) MIME-Version: 1.0 To: Dan Nelson References: <20080116150454.GP89314@pcjas.obspm.fr> <20080116162805.GH97708@dan.emsphone.com> In-Reply-To: <20080116162805.GH97708@dan.emsphone.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Albert Shih , freebsd-questions@freebsd.org Subject: Re: How manu swap ? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Jan 2008 17:28:21 -0000 Dan Nelson wrote: > In the last episode (Jan 16), Albert Shih said: > >> Hi all >> >> I known it's classic question. >> >> Long time ago when I install a FreeBSD x86 32 bits when I have N Go >> of Ram the installer take 2xN Go for the swap partition. >> >> Now I just install two machine with FreeBSD amd64 version with 8Go of >> Ram and FreeBSD installer take 4 Go of swap. >> >> Is a bug in the installer or now FreeBSD don't need 2xRam of swap ? >> > > When was the last time you saw your swap partition with more than 2GB > in use? On an 8GB system, you probably will either never have enough > processes to require swapping at all, or you will have one or two > processes so big that if they ever swap, it's a sign you need more RAM, > not more swap :) In systems with that much RAM, swap is pretty much > only used for crashdumps, and with minidumps enabled by default, you > don't need much. On small systems, the 2x-swap rule was because once > you allocated enough processes to require that much swap, you were > pretty much thrashing your system anyway I've read that the VM system in FreeBSD is optimized such that if you do start swapping it'll work best if your swap space is at least 2x RAM. Is that still valid on recent releases of FreeBSD? -- Bruce Cran