From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.lst.de (verein.lst.de [213.95.11.210]) (using TLSv1 with cipher EDH-RSA-DES-CBC3-SHA (168/168 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 80CB1DDFEF for ; Wed, 30 May 2007 20:13:58 +1000 (EST) Date: Wed, 30 May 2007 12:13:49 +0200 From: Christoph Hellwig To: Geert Uytterhoeven Subject: Re: [patch 6/7] ps3: ROM Storage Driver 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 In-Reply-To: Cc: linuxppc-dev@ozlabs.org, Christoph Hellwig , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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..