Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752776Ab0DTV7A (ORCPT ); Tue, 20 Apr 2010 17:59:00 -0400 Received: from mail.copilotco.com ([216.105.40.123]:53253 "EHLO mail.copilotco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751976Ab0DTV67 (ORCPT ); Tue, 20 Apr 2010 17:58:59 -0400 Date: Tue, 20 Apr 2010 14:58:59 -0700 From: Tracy Reed To: pasik@iki.fi, xen-devel@lists.xensource.com, Aoetools-discuss@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [Xen-devel] domU is causing misaligned disk writes Message-ID: <20100420215859.GW5660@tracyreed.org> Mail-Followup-To: Tracy Reed , pasik@iki.fi, xen-devel@lists.xensource.com, Aoetools-discuss@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20100420080958.GN5660@tracyreed.org> <20100420084955.GV1878@reaktio.net> <20100420200004.GQ5660@tracyreed.org> <20100420204151.GH1708@kremvax.cs.ubc.ca> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="3m6ZAtymzEdXvUYk" Content-Disposition: inline In-Reply-To: <20100420204151.GH1708@kremvax.cs.ubc.ca> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2614 Lines: 81 --3m6ZAtymzEdXvUYk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Apr 20, 2010 at 01:41:51PM -0700, Brendan Cully spake thusly: > You could also be limited by the size of the block request ring (I > believe the ring is normally only one page) -- the ring needs to be > large enough to handle the bandwidth delay product, and AoE means the > delay is probably higher than normal. Interesting. Any easy way to increase this as a test? > Do you get better performance against a local partition? You mean a local partition on local disk in the dom0 given to a domU as xvd? Let's see... I just created a 20G logical volume on the dom0: # /usr/sbin/lvcreate -n test -L20G sysvg Added it to the domain config file to be /dev/xvdi and rebooted. "phy:/dev/sysvg/test,xvdi,w" I know you can attach block devices on the fly but this has not been entirely reliable for me in the past so I reboot now. In domU against xvdi which is /dev/sysvg/test in dom0: # dd if=3D/dev/zero of=3D/dev/xvdi bs=3D4096 count=3D1000000 1000000+0 records in 1000000+0 records out 4096000000 bytes (4.1 GB) copied, 99.3749 seconds, 41.2 MB/s And iostat on dom0 shows: Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 824.00 4.00 101.00 16.00 39936.00 760.99 3.19 31.31 9.52 100.00 In dom0 against the local disk to demonstrate native performance: # dd if=3D/dev/zero of=3D/dev/sysvg/test bs=3D4096 count=3D1000000 1000000+0 records in 1000000+0 records out 4096000000 bytes (4.1 GB) copied, 84.9047 seconds, 48.2 MB/s Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 7.00 11104.00 5.00 96.00 48.00 48144.00 954.30 133.92 1172.40 9.94 100.40 Virtually no reads happening. This disk seems a bit slow (older 80G sata disk) but otherwise normal. I don't see anything indicating alignment issues. --=20 Tracy Reed http://tracyreed.org --3m6ZAtymzEdXvUYk Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) iD8DBQFLziOj9PIYKZYVAq0RAkp7AJ45PvbdgQX1g1OJ3ke75DXKB+NyhwCgn1ZM HSNBTA4Ev01HfpVOu8Z6Pbo= =JNhH -----END PGP SIGNATURE----- --3m6ZAtymzEdXvUYk-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/