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 14:53:21 -0500 Message-ID: <47618DB1.6030408@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20071213192633.GD10104@kernel.dk> Sender: linux-scsi-owner@vger.kernel.org To: Jens Axboe Cc: Mark Lord , Matthew Wilcox , IDE/ATA development list , Linux Kernel , linux-scsi , Neil Brown List-Id: linux-ide@vger.kernel.org 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? .. CC'ing Neil Brown.