From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lord Subject: Re: QUEUE_FLAG_CLUSTER: not working in 2.6.24 ? Date: Thu, 13 Dec 2007 14:32:20 -0500 Message-ID: <476188C4.9030802@rtr.ca> References: <47617B92.6020908@rtr.ca> <47617C07.3020501@rtr.ca> <47617E72.6080504@rtr.ca> <20071213185326.GQ26334@parisc-linux.org> <4761821F.3050602@rtr.ca> <20071213192633.GD10104@kernel.dk> <4761883A.7050908@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4761883A.7050908@rtr.ca> Sender: linux-kernel-owner@vger.kernel.org To: Mark Lord Cc: Jens Axboe , Matthew Wilcox , IDE/ATA development list , Linux Kernel , linux-scsi List-Id: linux-ide@vger.kernel.org Mark Lord wrote: > Jens Axboe wrote: >> 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? > .. > > Because the early 2.6.24 series failed to boot on this machine > due to bugs in the block layer -- so the code that caused this regression > is probably in the stuff from before the kernels became usable here. .. That sounds more harsh than intended --> the earlier 2.6.24 kernels (up to the first couple of -rc* ones failed here because of incompatibilities between the block/bio changes and libata. That's better, I think! Cheers