From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Anderson Subject: Re: Possible explanation for SCSI benchmark problems in 2.5 Date: Sun, 29 Sep 2002 14:32:46 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20020929213246.GA3743@beaverton.ibm.com> References: <200209292048.g8TKmN424799@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <200209292048.g8TKmN424799@localhost.localdomain> List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: linux-scsi@vger.kernel.org, Andrew Morton , Jens Axboe James Bottomley [James.Bottomley@steeleye.com] wrote: > Hi All, > > While looking at other code (OK, how to get the MCA drivers not to use bounce > buffers...) I discovered that the way scsi_scan.c calls > scsi_initialize_merge_fn() guarantees (on an x86) that the > blk_queue_bounce_limit is always called with BLK_BOUNCE_HIGH. This will > probably hurt benchmarks on machines with 1Gb or more of memory. > > The problem is that scsi_initialize_merge_fn() checks sdev->type, but this is > always -1 in scsi_alloc_sdev, and thus it never uses the pci dma mask for disk > devices. > > The attached patch moves the initialisation to after sdev->type has the > correct value. I thought this was previously discussed on this thread. http://marc.theaimsgroup.com/?l=linux-kernel&m=103064539622958&w=2 and I believe the comment from Jens was that this could be killed off in 2.5 if someone did a check for safety on all the devices. -andmike -- Michael Anderson andmike@us.ibm.com