Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757516AbXKVD5d (ORCPT ); Wed, 21 Nov 2007 22:57:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753724AbXKVD5Z (ORCPT ); Wed, 21 Nov 2007 22:57:25 -0500 Received: from mailgate-out2.mysql.com ([213.136.52.68]:39778 "EHLO mailgate.mysql.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752477AbXKVD5Y (ORCPT ); Wed, 21 Nov 2007 22:57:24 -0500 X-Greylist: delayed 1753 seconds by postgrey-1.27 at vger.kernel.org; Wed, 21 Nov 2007 22:57:24 EST Subject: Re: [PATCH 2/9]: Reduce Log I/O latency From: Stewart Smith To: David Chinner Cc: Andi Kleen , xfs-oss , lkml In-Reply-To: <20071122011214.GR114266761@sgi.com> References: <20071122003339.GH114266761__34694.2978365861$1195691722$gmane$org@sgi.com> <20071122011214.GR114266761@sgi.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-WAjZXbGIUan1gQIlUjdm" Organization: MySQL AB Date: Thu, 22 Nov 2007 14:28:43 +1100 Message-Id: <1195702123.8369.78.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.12.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2541 Lines: 62 --=-WAjZXbGIUan1gQIlUjdm Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Thu, 2007-11-22 at 12:12 +1100, David Chinner wrote: > In all the cases that I know of where ppl are using what could > be considered real-time I/O (e.g. media environments where they > do real-time ingest and playout from the same filesystem) the > real-time ingest processes create the files and do pre-allocation > before doing their I/O. This I/O can get held up behind another > process that is not real time that has issued log I/O.=20 >=20 > Given there is no I/O priority inheritence and having log I/O stall > will stall the entire filesystem, we cannot allow log I/O to > stall in real-time environments. Hence it must have the highest > possible priority to prevent this. FWIW from a "real time" database POV this seems to make sense to me... in fact, we probably rely on filesystem metadata way too much (historically it's just "worked".... although we do seem to get issues on ext3). I have a (casually stupid) simulation program... although I've observed little to no problems on all my XFS tests using it. --=20 Stewart Smith, Senior Software Engineer (MySQL Cluster) MySQL AB, www.mysql.com Office: +14082136540 Ext: 6616 VoIP: 6616@sip.us.mysql.com Mobile: +61 4 3 8844 332 --=-WAjZXbGIUan1gQIlUjdm Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iQIVAwUAR0T3a73yNwHyU3DLAQLp7Q/+PaPp6lTGjHwPBvP8RvoPzEvajjlj9JhM 5jWPDFv8xJcK2zIMCSvzV7gV4FLVTLT6mX4ZOW3dQ7aItbGEM0KzT9P/T82pjDyf T9j2HRuN45bVEMGuqpkyuwCKuLK+XJv+nKio6+5pZgMpXulWM1xY1pPDaXW/OkP4 ZwgU3CkYkBC0u7bTmCb7fndFmmOtXGXox/4GSTU+J1Ez6SPblcTt66EThCD1ad7d UfsF08LaEnUNoDfWDNSd2WxnD6A3p4EL3KoUla2lBk7a7FyOOV04zeK9LulinqpA KceXVgy2J8BUyFeZdlCI02J8QhMJXpG2qgCjpRlmbjZT+dLLCvES2O6I6NqqCNW+ Z/H00c9TWAhpjuWqga5wz0F0xROGec/Nn5rs/3XKz13HmaKny32Dyv2xm9t/1qFr 4GSkHWQtJrovJwA+A6pBIzIJJ4EUbnVanu4pHZ0gL925dqQRCl/49/GsiGuMBQme gk4Izdf+2sAdQF7lnPAquQXu5g9U19zhLog25jVLr5R4H8gY1hpqKWO3ftC4UOsW fFjV2aGI+CMb9Fg2lhkgeHyvJFy4Rx+5Luh4OkWDdz9aqknJgR+tthGN5LlWUCZJ V3HOOHNJrsKIG/0yZ6u/ek++3/+gIuNn1ZGTLQHgvqGGKmrt0GjR0nagNeB6JdtH uD3ce+3Rq7o= =KdGI -----END PGP SIGNATURE----- --=-WAjZXbGIUan1gQIlUjdm-- - 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/