Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764032AbXLMT0v (ORCPT ); Thu, 13 Dec 2007 14:26:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757501AbXLMT0l (ORCPT ); Thu, 13 Dec 2007 14:26:41 -0500 Received: from brick.kernel.dk ([87.55.233.238]:24568 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756595AbXLMT0k (ORCPT ); Thu, 13 Dec 2007 14:26:40 -0500 Date: Thu, 13 Dec 2007 20:26:35 +0100 From: Jens Axboe To: Mark Lord Cc: Matthew Wilcox , IDE/ATA development list , Linux Kernel , linux-scsi Subject: Re: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Message-ID: <20071213192633.GD10104@kernel.dk> References: <47617B92.6020908@rtr.ca> <47617C07.3020501@rtr.ca> <47617E72.6080504@rtr.ca> <20071213185326.GQ26334@parisc-linux.org> <4761821F.3050602@rtr.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4761821F.3050602@rtr.ca> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1529 Lines: 43 On Thu, Dec 13 2007, Mark Lord wrote: > Matthew Wilcox wrote: > >On Thu, Dec 13, 2007 at 01:48:18PM -0500, Mark Lord wrote: > >>Problem confirmed. 2.6.23.8 regularly generates segments up to 64KB for > >>libata, > >>but 2.6.24 uses only 4KB segments and a *few* 8KB segments. > > > >Just a suspicion ... could this be slab vs slub? ie check your configs > >are the same / similar between the two kernels. > .. > > Mmmm.. a good thought, that one. > But I just rechecked, and both have CONFIG_SLAB=y > > My guess is that something got changed around when Jens > reworked the block layer for 2.6.24. > I'm going to dig around in there now. I didn't rework the block layer for 2.6.24 :-). The core block layer changes since 2.6.23 are: - Support for empty barriers. Not a likely candidate. - Shared tag queue fixes. Totally unlikely. - sg chaining support. Not likely. - The bio changes from Neil. Of the bunch, the most likely suspects in this area, since it changes some of the code involved with merges and blk_rq_map_sg(). - Lots of simple stuff, again very unlikely. Anyway, it sounds odd for this to be a block layer problem if you do see occasional segments being merged. So it sounds more like the input data having changed. Why not just bisect it? -- Jens Axboe -- 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/