From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave C Boutcher Subject: Re: [patch 2/4] ibmvscsi.c: limit size of I/O requests Date: Tue, 30 Nov 2004 09:29:16 -0600 Message-ID: <20041130152916.GA7639@cs.umn.edu> References: <20041129203107.GB31011@cs.umn.edu> <20041130075457.GD10450@suse.de> Reply-To: boutcher@cs.umn.edu Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail.cs.umn.edu ([128.101.35.202]:51597 "EHLO mail.cs.umn.edu") by vger.kernel.org with ESMTP id S262124AbUK3P3Y (ORCPT ); Tue, 30 Nov 2004 10:29:24 -0500 Received: from localhost (localhost [127.0.0.1]) by augustus.cs.umn.edu (Postfix) with ESMTP id 5213E5C385 for ; Tue, 30 Nov 2004 09:29:20 -0600 (CST) Received: from mail.cs.umn.edu ([127.0.0.1]) by localhost (augustus [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 03400-01 for ; Tue, 30 Nov 2004 09:29:18 -0600 (CST) Received: from tera.cs.umn.edu (tera.cs.umn.edu [128.101.35.163]) by mail.cs.umn.edu (Postfix) with ESMTP id 9AF915C37C for ; Tue, 30 Nov 2004 09:29:16 -0600 (CST) Content-Disposition: inline In-Reply-To: <20041130075457.GD10450@suse.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org 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. -- Dave Boutcher