From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] block: set the bounce_pfn to the actual DMA limit rather than to max memory Date: Fri, 24 Sep 2010 21:26:03 +0200 Message-ID: <4C9CFB4B.10404@fusionio.com> References: <4C9CAE68.4060706@fusionio.com> <20100924170532.GA29071@us.ibm.com> <4C9CEDE5.902@fusionio.com> <20100924192059.GA550@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100924192059.GA550@us.ibm.com> Sender: linux-scsi-owner@vger.kernel.org To: Malahal Naineni Cc: "dm-devel@redhat.com" , "linux-scsi@vger.kernel.org" List-Id: dm-devel.ids On 2010-09-24 21:20, Malahal Naineni wrote: > Jens Axboe [jaxboe@fusionio.com] wrote: >>> This patch also _fixed_ our problem. So we are fine with either patch, >>> but this patch is preferred as it enables more request merges. Also, >>> both patches maybe needed for some configurations. >> >> Plus it doesn't needlessly bounce, that's the real problem you want to >> fix. I have applied this thread patch to for-2.6.37/core, thanks. > > There is a shortcut check in blk_queue_bounce() that uses blk_max_pfn to > return without doing anything. blk_max_pfn is not updated when we do > hot-plug memory add, so bounce buffers are NOT really used in our case > (thankfully)! Any reason we can't just add a hot mem add notifier and update the block copies when we need to? -- Jens Axboe