From owner-freebsd-performance@FreeBSD.ORG Tue May 3 04:37:24 2005 Return-Path: Delivered-To: freebsd-performance@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id D2FC416A4CE; Tue, 3 May 2005 04:37:24 +0000 (GMT) Received: from silver.he.iki.fi (helenius.fi [193.64.42.241]) by mx1.FreeBSD.org (Postfix) with ESMTP id 1625F43D70; Tue, 3 May 2005 04:37:24 +0000 (GMT) (envelope-from pete@he.iki.fi) Received: from [193.64.42.134] (h86.vuokselantie10.fi [193.64.42.134]) by silver.he.iki.fi (Postfix) with ESMTP id BF3ADBC46; Tue, 3 May 2005 07:37:21 +0300 (EEST) Message-ID: <42770026.80901@he.iki.fi> Date: Tue, 03 May 2005 07:37:58 +0300 From: Petri Helenius User-Agent: Mozilla Thunderbird 1.0.2 (Windows/20050317) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Robert Watson References: <19879.1115061648@critter.freebsd.dk> <20050502214208.M87351@fledge.watson.org> In-Reply-To: <20050502214208.M87351@fledge.watson.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit cc: Steven Hartland cc: Poul-Henning Kamp cc: Eric Anderson cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance on 5.x X-BeenThere: freebsd-performance@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Performance/tuning List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 03 May 2005 04:37:24 -0000 Robert Watson wrote: > > The next thing that would be quite nice to measure is the rate of I/O > transactions per second we can get to the disk using the disk device > directly, with a minimal transaction size. I have a vague > recollection that you have to be careful in Linux because their > character device nodes for disk devices are buffered, and you really > want unbuffered I/O. I noticed that changing vfs.read_max from the default 8 to 16 has a dramatic effect on sequential read performance. Increasing it further did not have measurable effect. Pete