From owner-freebsd-current@FreeBSD.ORG Wed Mar 1 20:59:17 2006 Return-Path: X-Original-To: current@freebsd.org 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 C165016A424; Wed, 1 Mar 2006 20:59:17 +0000 (GMT) (envelope-from rink@charm.il.fontys.nl) Received: from mail.unilogicnetworks.net (mail-out.unilogicnetworks.net [62.133.192.42]) by mx1.FreeBSD.org (Postfix) with ESMTP id 150E943D6E; Wed, 1 Mar 2006 20:59:12 +0000 (GMT) (envelope-from rink@charm.il.fontys.nl) Received: from mail.il.fontys.nl (mx0.il.fontys.nl [194.26.13.7]) by mail.unilogicnetworks.net (Postfix) with ESMTP id 42D03EF14A; Wed, 1 Mar 2006 21:59:11 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by mail.il.fontys.nl (Postfix/VSRI) with ESMTP id 69F0717042; Wed, 1 Mar 2006 22:04:10 +0100 (CET) Received: from mail.il.fontys.nl ([127.0.0.1]) by localhost (sukke.il.fontys.nl [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 71143-07; Wed, 1 Mar 2006 22:04:09 +0100 (CET) Received: from charm.il.fontys.nl (charm.il.fontys.nl [194.26.13.34]) by mail.il.fontys.nl (Postfix) with ESMTP; Wed, 1 Mar 2006 22:04:09 +0100 (CET) Received: by charm.il.fontys.nl (Postfix, from userid 1678) id B978840B5; Wed, 1 Mar 2006 21:57:07 +0100 (CET) Date: Wed, 1 Mar 2006 21:57:07 +0100 From: Rink Springer To: Julian Elischer Message-ID: <20060301205707.GA65200@il.fontys.nl> References: <200603010505.k2155HfQ003205@aldan.algebra.com> <20060301144124.GA14411@uk.tiscali.com> <4405EFE9.6030807@elischer.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4405EFE9.6030807@elischer.org> X-Editor: Vim http://www.vim.org/ X-Info: http://rink.nu/ X-Operating-System: FreeBSD 6.0-STABLE i386 User-Agent: Mutt/1.5.11 X-Virus-Scanned: amavisd-new at il.fontys.nl Cc: current@freebsd.org, sos@freebsd.org, "Mikhail T." , Brian Candler Subject: Re: pitiful performance of an SATA150 drive X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 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: Wed, 01 Mar 2006 20:59:17 -0000 > I believe that linux uses bufferring in their 'raw' disks so that you > may be actually doing larger > reads and writes than you know.. (of course my knowledge of Linux is a > bit old so > they may have changed that) Linux 2.5+ will always queue I/O requests in PAGE_SIZE chunks (4KB on i386) or less. These tiny requests will be concatinated by the disk elevator if possible; for example, reading 64KB from block 0 once would result in requesting 16 times 4KB, which will be translated to a single "Read 64KB from block 0" request. Therefore, the PAGE_SIZE cache (also known as the buffer cache, which was merged with the page cache in the 2.5 tree) does not hurt performance one bit. I have no clue what FreeBSD does on this end. -- Rink P.W. Springer - http://rink.nu "Richter: Tribute? You steal men's souls, and make them your slaves! Dracula: Perhaps the same could be said of all religions." - Castlevania: Symphony of the Night