From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755194AbXKSTzj (ORCPT ); Mon, 19 Nov 2007 14:55:39 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751660AbXKSTzb (ORCPT ); Mon, 19 Nov 2007 14:55:31 -0500 Received: from gate.crashing.org ([63.228.1.57]:33169 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751496AbXKSTza (ORCPT ); Mon, 19 Nov 2007 14:55:30 -0500 Subject: Re: SCSI breakage on non-cache coherent architectures From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: James Bottomley Cc: Matthew Wilcox , Linux Kernel list , linux-scsi , Russell King In-Reply-To: <1195484964.3283.4.camel@localhost.localdomain> References: <1195450523.7022.37.camel@pasglop> <20071119123240.GA12494@parisc-linux.org> <1195484964.3283.4.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 20 Nov 2007 06:55:16 +1100 Message-Id: <1195502116.6970.5.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > I'd like to be rid of it inside the command for various reasons: every > command has one of these, and they're expensive in the allocation (at 96 > bytes). There's no reason we have to allocate and free that amount of > space with every command. In theory, the number of these is bounded at > the queue depth, in practice, there's usually only one, and this DMA > alignment issue does requires most drivers to double copy. Do you have a plan for short term here ? I'd like something fixed for .25, so I may have to introduce a __dma_aligned macro of some sort to deal with that in the meantime... Ben.