From owner-freebsd-current@FreeBSD.ORG Fri Jan 5 11:31:30 2007 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 4593E16A407; Fri, 5 Jan 2007 11:31:30 +0000 (UTC) (envelope-from lulf@stud.ntnu.no) Received: from signal.itea.ntnu.no (signal.itea.ntnu.no [129.241.190.231]) by mx1.freebsd.org (Postfix) with ESMTP id F08FD13C455; Fri, 5 Jan 2007 11:31:29 +0000 (UTC) (envelope-from lulf@stud.ntnu.no) Received: from localhost (localhost [127.0.0.1]) by signal.itea.ntnu.no (Postfix) with ESMTP id AFF9333A89; Fri, 5 Jan 2007 12:31:27 +0100 (CET) Received: from webmail.ntnu.no (textus12.itea.ntnu.no [129.241.56.162]) by signal.itea.ntnu.no (Postfix) with ESMTP; Fri, 5 Jan 2007 12:31:27 +0100 (CET) Received: from 53.3.erx-lhm.eidsiva.net (53.3.erx-lhm.eidsiva.net [87.248.3.53]) by webmail.ntnu.no (Horde MIME library) with HTTP; Fri, 5 Jan 2007 12:31:27 +0100 Message-ID: <20070105123127.gnk0v58p44488g48@webmail.ntnu.no> Date: Fri, 5 Jan 2007 12:31:27 +0100 From: lulf@stud.ntnu.no To: Poul-Henning Kamp References: <3763.1167992304@critter.freebsd.dk> In-Reply-To: <3763.1167992304@critter.freebsd.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes"; format="flowed" Content-Disposition: inline Content-Transfer-Encoding: quoted-printable User-Agent: Internet Messaging Program (IMP) H3 (4.1.3) X-Content-Scanned: with sophos and spamassassin at mailgw.ntnu.no. Cc: freebsd-current@freebsd.org, freebsd-geom@freebsd.org Subject: Re: Pluggable Disk Schedulers in GEOM 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: Fri, 05 Jan 2007 11:31:30 -0000 Siterer Poul-Henning Kamp : > In message <20070105015800.s3rqdzgm8k8owk4s@webmail.ntnu.no>, =20 > lulf@stud.ntnu.no > writes: > >> I was wondering if someone have started on the pluggable >> disk-scheduler project >> on the "new ideas"-page yet. >> >> I was thinking on how one could implement this in GEOM by [...] > *snip* > > Here are some ideas: > > Remove disksorting and see if if and how big a difference > it makes today. Test both SCSI, ATA and USB media, and > test both low-level benchmarks and "real-world" workloads. > > Change disksorting to reverse unidirectional elevator > and bidirectional elevator and see if it makes a difference. > (Modern disks store blocks in reverse sector order on > the disk, discover and explain why) > > Capture an I/O trace from a suitably sensible realworld > system, including the detailed timestamps of issuance > and completion of the requests. Treat results statistically > and try to determine a formula for predicting how long > a given request is going to take for the disk. > > It's not that I think that all your ideas are bad, I am just > not sure that the (traditional) view of the hardware they > are based on, is still relevant, and I think your time would > be much better spent addressing that question. > I understand, and I clearly see the point about new hardware being =20 more intelligent in these matters. However, I will look into this a bit more just out of curiosity, and =20 do some actual test on how this can affect performance in the =20 scenarios you describe. And thanks for the tips! --=20 Ulf Lilleengen