From owner-freebsd-questions@FreeBSD.ORG Sat Jan 10 02:53:49 2009 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 167A11065674 for ; Sat, 10 Jan 2009 02:53:49 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: from mail-ew0-f21.google.com (mail-ew0-f21.google.com [209.85.219.21]) by mx1.freebsd.org (Postfix) with ESMTP id 72FC48FC0A for ; Sat, 10 Jan 2009 02:53:48 +0000 (UTC) (envelope-from rwmaillists@googlemail.com) Received: by ewy14 with SMTP id 14so11781317ewy.19 for ; Fri, 09 Jan 2009 18:53:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:subject :message-id:in-reply-to:references:x-mailer:mime-version :content-type:content-transfer-encoding; bh=gFRJDXHX1sZC3Ha2SHD1cSy95nJ1IEpxJaHk1UOplng=; b=I4zWCw+kpjX3N5wr0+xSncnl42Q6vjwp0+GX+qVj/vdStSUmdVcZ0f6ZMODyxZTDA3 1/STYmAhZR4puFjAGB3+11qOmBlG981Ol7GMmi6LDo8JObkOkP1sPWHkRH3lzu6g/W5L mbgKSQ6Dw/pBsL2aLZ/O7GyIQ3brEKpj26cQI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=date:from:to:subject:message-id:in-reply-to:references:x-mailer :mime-version:content-type:content-transfer-encoding; b=IWvlM8IKR0rWLCCDjQ8AbMIF06/TGscfo5ZVgUN/YaH1dxsxcEk/arUIky1yIVSa/M Ewzemynk/mAsvojYjoSIrId6l8YF+DiG4sYj6TYi7KNvu2P3FvwItHTG4irdgRyLTySs 5+112ZB8tGyPocVDsVmGScmkZl0S44rwzNYb0= Received: by 10.210.35.17 with SMTP id i17mr7952063ebi.165.1231556027530; Fri, 09 Jan 2009 18:53:47 -0800 (PST) Received: from gumby.homeunix.com (bb-87-81-140-128.ukonline.co.uk [87.81.140.128]) by mx.google.com with ESMTPS id y37sm939817iky.4.2009.01.09.18.53.45 (version=SSLv3 cipher=RC4-MD5); Fri, 09 Jan 2009 18:53:46 -0800 (PST) Date: Sat, 10 Jan 2009 02:53:43 +0000 From: RW To: freebsd-questions@freebsd.org Message-ID: <20090110025343.6f0e95d1@gumby.homeunix.com> In-Reply-To: <443afs49ix.fsf@be-well.ilk.org> References: <2c66535d0901082253k5b8ff098w73234a1944929929@mail.gmail.com> <20090109105458.I8836@wojtek.tensor.gdynia.pl> <49672373.3020704@snaffler.net> <2c66535d0901090340y473ce9dcj74ae2a44e5cc0789@mail.gmail.com> <443afs49ix.fsf@be-well.ilk.org> X-Mailer: Claws Mail 3.5.0 (GTK+ 2.12.11; i386-portbld-freebsd7.1) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: how to use the MFS ? 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: Sat, 10 Jan 2009 02:53:49 -0000 On Fri, 09 Jan 2009 13:30:30 -0500 Lowell Gilbert wrote: > "PstreeM China" writes: > > > i think the option WRKDIRPREFIX is a good idea , and i whill test > > the methon unionfs. > > Definitely benchmark against just using a native local filesystem, > though. Taking away all of that memory that FreeBSD would otherwise > use for *caching* file data could well end up making your builds > *slower* with the MFS than they would have been without it. I've a vague recollection that I tried something like this, a few years ago, and found that the difference was too small to measure. I think that however you do it, you basically end-up with something that looks like: CPU/L1/L2 -> memory -> disk and whether the "memory->disk" part is a cached-file or swap-backed memory is really just a matter of book-keeping - the VM system moves the physical memory around as it likes. The book-keeping differences may be significant, but they are not different in the electronic verses electro-mechanical sense, and such intuitions may not relevant. Poul-Henning Kamp, has an interesting article in this area for the varnish project: "I have spent many years working on the FreeBSD kernel, and only rarely did I venture into userland programming, but when I had occation to do so, I invariably found that people programmed like it was still 1975." http://varnish.projects.linpro.no/wiki/ArchitectNotes [Not that there's anything wrong with 1975.]