From owner-freebsd-stable@FreeBSD.ORG Wed Feb 18 08:12:05 2009 Return-Path: Delivered-To: freebsd-stable@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C0554106573B; Wed, 18 Feb 2009 08:12:03 +0000 (UTC) (envelope-from gary.jennejohn@freenet.de) Received: from mout1.freenet.de (mout1.freenet.de [IPv6:2001:748:100:40::2:3]) by mx1.freebsd.org (Postfix) with ESMTP id 5284B8FC0C; Wed, 18 Feb 2009 08:12:03 +0000 (UTC) (envelope-from gary.jennejohn@freenet.de) Received: from [195.4.92.14] (helo=4.mx.freenet.de) by mout1.freenet.de with esmtpa (ID gary.jennejohn@freenet.de) (port 25) (Exim 4.69 #76) id 1LZhX9-0004Dt-1N; Wed, 18 Feb 2009 09:11:55 +0100 Received: from tcc1f.t.pppool.de ([89.55.204.31]:39187 helo=ernst.jennejohn.org) by 4.mx.freenet.de with esmtpa (ID gary.jennejohn@freenet.de) (port 25) (Exim 4.69 #76) id 1LZhX8-0000Lm-OZ; Wed, 18 Feb 2009 09:11:54 +0100 Date: Wed, 18 Feb 2009 09:11:51 +0100 From: Gary Jennejohn To: Scott Long Message-ID: <20090218091151.4d9c2bd7@ernst.jennejohn.org> In-Reply-To: <499B221C.2050804@samsco.org> References: <499981AF.9030204@samsco.org> <20090217164203.4c586f48@ernst.jennejohn.org> <20090218073542.E5200@delplex.bde.org> <499B221C.2050804@samsco.org> X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; amd64-portbld-freebsd8.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: FreeBSD Current , Stable , Bruce Evans , scsi@FreeBSD.org Subject: Re: HEADS UP: More CAM fixes. X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: gary.jennejohn@freenet.de List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Feb 2009 08:12:08 -0000 On Tue, 17 Feb 2009 13:46:20 -0700 Scott Long wrote: > Bruce Evans wrote: > > On Tue, 17 Feb 2009, Gary Jennejohn wrote: > > > >> I tested this with an Adaptec 29160. I saw no real improvement in > >> performance, but also no regressions. > >> > >> I suspect that the old disk I had attached just didn't have enough > >> performance reserves to show an improvement. > >> > >> My test scenario was buildworld. Since /usr/src and /usr/obj were both > >> on the one disk it got a pretty good workout. > > ^^^^ low > >> > >> AMD64 X2 (2.5 GHz) with 4GB of RAM. > > > > Buildworld hardly uses the disk at all. It reads and writes a few hundred > > MB. Ideally the i/o should go at disk speeds of 50-200MB/S and thus take > > between 20 and 5 seconds. In practice, it will take a few more seconds. > > physically but perhaps even less virtually due to parallelism. > > > > Bruce > > Yes, on modern machines, buildworld is bound almost completely by disk > latency, and not at all by disk or controller bandwidth. > > Scott > Maybe I misunderstood something, but I thought the patch was supposed to improve queuing. Seems like all the seeks during a buildowrld would exercise that. All I can say is that the disk did _lots_ of seeking. --- Gary Jennejohn