From owner-freebsd-fs@FreeBSD.ORG Fri Dec 7 14:11:53 2007 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8F54616A418 for ; Fri, 7 Dec 2007 14:11:53 +0000 (UTC) (envelope-from freebsd-fs@m.gmane.org) Received: from ciao.gmane.org (main.gmane.org [80.91.229.2]) by mx1.freebsd.org (Postfix) with ESMTP id 44D9013C4CC for ; Fri, 7 Dec 2007 14:11:53 +0000 (UTC) (envelope-from freebsd-fs@m.gmane.org) Received: from list by ciao.gmane.org with local (Exim 4.43) id 1J0dvO-00041n-3y for freebsd-fs@freebsd.org; Fri, 07 Dec 2007 14:11:30 +0000 Received: from lara.cc.fer.hr ([161.53.72.113]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 07 Dec 2007 14:11:30 +0000 Received: from ivoras by lara.cc.fer.hr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 07 Dec 2007 14:11:30 +0000 X-Injected-Via-Gmane: http://gmane.org/ To: freebsd-fs@freebsd.org From: Ivan Voras Date: Fri, 07 Dec 2007 15:16:30 +0100 Lines: 40 Message-ID: References: <868x46u0lz.fsf@ds4.des.no> <20071207133700.GO10459@cicely12.cicely.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig51AF23534A84605A6ACA3557" X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: lara.cc.fer.hr User-Agent: Thunderbird 2.0.0.6 (X11/20070801) In-Reply-To: <20071207133700.GO10459@cicely12.cicely.de> X-Enigmail-Version: 0.95.3 Sender: news Subject: Re: readv: parallel or sequential? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 07 Dec 2007 14:11:53 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig51AF23534A84605A6ACA3557 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Bernd Walter wrote: > I wonder if the kernel can read a single file in parallel, because > disk heads can't be on multiple positions at the same time. They can be in case of RAID0 and similar schemes. > ZFS does fill read cache in parallel if it knowns that there are enough= > spindels, but in every other case the FS doesn't know about multiple > spindels. > In case of ZFS you don't have to care much about it in you application > because the next sequentiel fileread will use the previously parallel > prefilled cache. Yes, ZFS is supposed to be doing marvelous things with IO prediction and scheduling, but I think even basic "ladder" scheduling done in FreeBSD could in theory help in tight spots with multiple requests. --------------enig51AF23534A84605A6ACA3557 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.4-svn0 (GNU/Linux) iD8DBQFHWVXEldnAQVacBcgRAmfeAKDWpfk14QJvaSWHgOHFZM0L/5k4AwCdFhsX RTEJji9qv9pHDC07XEGEtpg= =IAO/ -----END PGP SIGNATURE----- --------------enig51AF23534A84605A6ACA3557--