From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [patch 2/4] ibmvscsi.c: limit size of I/O requests Date: Thu, 2 Dec 2004 21:13:11 +0100 Message-ID: <20041202201310.GC26695@suse.de> References: <20041129203107.GB31011@cs.umn.edu> <20041130075457.GD10450@suse.de> <20041130152916.GA7639@cs.umn.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from ns.virtualhost.dk ([195.184.98.160]:33164 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S261750AbULBUNN (ORCPT ); Thu, 2 Dec 2004 15:13:13 -0500 Content-Disposition: inline In-Reply-To: <20041130152916.GA7639@cs.umn.edu> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org Cc: sleddog@us.ibm.com On Tue, Nov 30 2004, Dave C Boutcher wrote: > On Tue, Nov 30, 2004 at 08:54:58AM +0100, Jens Axboe wrote: > > On Mon, Nov 29 2004, Dave C Boutcher wrote: > > > Description: Limit the size of I/O requests sent by the > > > ibmvscsi adapter. With better I/O scheduling (and thus larger > > > requests) we were breaking some servers. > > > > Nack, why can't you use /dev/block/xxx/queue/max_sectors_kb to control > > this? > > The basic function of this patch is to set host->max_sectors based > on information from the SCSI target. > > There is a default value because two of the existing target implementations > (there are three) don't set the value. > > I confess to making the default value a module parameter because I > took a SWAG at the correct value. I COULD remove the module > parameter part of this patch, though if someone actually cares enough > about performance to tweak it, modprobe.conf seems like a nice place to > set it. I think it's much better to set host->max_sectors to a sane high value, then change it per-target if you need to. This is how other SCSI host adapters work, what makes ibmvscsi different? -- Jens Axboe