From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerhard Schneider Subject: Re: SCSI tape access on 2.6 kernels? Date: Tue, 24 Jan 2006 22:01:04 +0100 Message-ID: <43D69590.5050003@ilsb.tuwien.ac.at> References: <43D604AD.6050607@ilsb.tuwien.ac.at> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig70A47EC1F126287215560BB4" Return-path: Received: from gh-gw1.ilsb.tuwien.ac.at ([128.130.23.14]:63634 "EHLO gh-gw1.ilsb.tuwien.ac.at") by vger.kernel.org with ESMTP id S1750708AbWAXVBN (ORCPT ); Tue, 24 Jan 2006 16:01:13 -0500 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kai Makisara Cc: linux-scsi@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig70A47EC1F126287215560BB4 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Kai Makisara schrieb: > The only thing that could be seen in Gerhard's tests with try_direct_io= =3D0=20 > should be higher CPU load. It probably won't have any effect on the spe= ed=20 > in these tests. >=20 > Disabling direct i/o helps in fixed block mode if the application's rea= d()=20 > and write() byte counts are small, e.g., 10 kB. With 64 kB it should no= t=20 > have any effect. Additionally, Gerhard is probably using variable block= =20 > mode and there is no read-ahead. There is write-behind which is disable= d=20 > when doing direct i/o but this should have no effect since if the HBA i= s=20 > able to sustain the speed the drive requires. >=20 I fear you're right. There hasn't been any significant difference in write/read speed when enabling/disabling direct i/o (significant doesn't mean a speedup of 20-100% - I want to see more than 40MB/s on a LTO-3 tape drive, and not 1.2).. Different fixed and variable block sizes didn't show significant speed increases, too.. - and I still expect a kernel problem, not a tape problem.. Tomorrow I will compile a kernel < 2.6.12 and redo testing.. GS --=20 Gerhard Schneider Institute of Lightweight Design and e-Mail: gs@ilsb.tuwien.ac.at Structural Biomechanics (E317) Tel.: +43 1 58801 31716 Vienna University of Technology / Austria Fax: +43 1 58801 31799 A-1040 Wien, Gusshausstrasse 27-29 http://www.ilsb.tuwien.ac.at/~gs/ --------------enig70A47EC1F126287215560BB4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFD1pWUE6e53f4wQG4RAs4eAKC6qki5Rlo/h2KOuoM76C1HPYnTNgCeMIRQ 1Bm/Tp7RALulwcU53Hu2hhY= =kzHe -----END PGP SIGNATURE----- --------------enig70A47EC1F126287215560BB4--