From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [patch 6/7] ps3: ROM Storage Driver Date: Wed, 30 May 2007 12:13:49 +0200 Message-ID: <20070530101348.GD24586@lst.de> References: <20070525083607.784351000@sonycom.com> <20070525083632.677742000@sonycom.com> <20070529104948.GC29351@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from verein.lst.de ([213.95.11.210]:54958 "EHLO mail.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751578AbXE3KO0 (ORCPT ); Wed, 30 May 2007 06:14:26 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Geert Uytterhoeven Cc: Christoph Hellwig , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org On Tue, May 29, 2007 at 01:11:41PM +0200, Geert Uytterhoeven wrote: > > This looks very inefficient. Just set sg_tablesize of your driver > > to 1 to avoid getting mutiple segments. > > The disadvantage of setting sg_tablesize = 1 is that the driver will get small > requests (PAGE_SIZE) most of the time, which is very bad for performance. If you set .clustering = 1 in your host template you will frequently get larger requests. For any sane hypervisor or hardware the copy should be worth than that. Then again a sane hardware or hypervisor would support SG requests..