Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753803AbYJFDr3 (ORCPT ); Sun, 5 Oct 2008 23:47:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752389AbYJFDrV (ORCPT ); Sun, 5 Oct 2008 23:47:21 -0400 Received: from ipmail04.adl2.internode.on.net ([203.16.214.57]:13730 "EHLO ipmail04.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751835AbYJFDrU (ORCPT ); Sun, 5 Oct 2008 23:47:20 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AqACABMn6Uh5LF82iGdsb2JhbACTWgEBARUipDeBaoMj X-IronPort-AV: E=Sophos;i="4.33,366,1220193000"; d="scan'208";a="220989299" Date: Mon, 6 Oct 2008 14:18:29 +1100 From: Dave Chinner To: Aaron Carroll Cc: Bodo Eggert <7eggert@gmx.de>, Jens Axboe , Andi Kleen , Andrew Morton , Arjan van de Ven , linux-kernel@vger.kernel.org, Alan Cox Subject: Re: [PATCH] Give kjournald a IOPRIO_CLASS_RT io priority Message-ID: <20081006031829.GQ30001@disturbed> Mail-Followup-To: Aaron Carroll , Bodo Eggert <7eggert@gmx.de>, Jens Axboe , Andi Kleen , Andrew Morton , Arjan van de Ven , linux-kernel@vger.kernel.org, Alan Cox References: <20081002233426.GG30001@disturbed> <48E71EFC.7040403@gelato.unsw.edu.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <48E71EFC.7040403@gelato.unsw.edu.au> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1593 Lines: 37 On Sat, Oct 04, 2008 at 05:45:00PM +1000, Aaron Carroll wrote: > Dave Chinner wrote: >> On Thu, Oct 02, 2008 at 05:32:04PM +0200, Bodo Eggert wrote: >>> Sounds like you need a priority class besides sync and async. >> >> There's BIO_META now as well, which I was testing at the same time >> as RT priority. Marking all the metadata I/O as BIO_META did help, >> but once again I never got to determining if that was a result of >> the different tagging or the priority increase. > > What exactly do you want META to mean? Strict prioritisation over > all other non-META requests, or just more frequent and/or larger > dispatches? Should META requests be sorted? The real question is "what was it supposed to mean"? AFAICT, it was added to a couple of filesystems to be used to tag superblock read I/O. Why - I don't know - there's a distinct lack of documentation surrounding these bio flags. :/ Realistically, I'm not sure that having a separate queue for BIO_META will buy us anything, given that noop is quite often the fastest scheduler for XFS because it enables interleaved metadata I/O to be merged with data I/O. Like I said, I was not able to spend the time to determine exactly how BIO_META affected I/O patterns, so I can't really comment on whether it is really necessary or not. Cheers, Dave. -- Dave Chinner david@fromorbit.com -- 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/