Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752760AbYKKUep (ORCPT ); Tue, 11 Nov 2008 15:34:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751635AbYKKUeh (ORCPT ); Tue, 11 Nov 2008 15:34:37 -0500 Received: from nlpi053.sbcis.sbc.com ([207.115.36.82]:51010 "EHLO nlpi053.prodigy.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751160AbYKKUeh (ORCPT ); Tue, 11 Nov 2008 15:34:37 -0500 Date: Tue, 11 Nov 2008 14:34:21 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@quilx.com To: Yasunori Goto cc: "Luck, Tony" , FUJITA Tomonori , linux-ia64@vger.kernel.org, Linux Kernel ML , Joerg Roedel Subject: Re: [Q] Why does dma_alloc_coherent() of ia64 GFP_DMA? In-Reply-To: <20081111141430.D5C7.E1E9C6FF@jp.fujitsu.com> Message-ID: References: <20081110121123.F82A.E1E9C6FF@jp.fujitsu.com> <20081111141430.D5C7.E1E9C6FF@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Spam-Score: -2.6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 744 Lines: 17 On Tue, 11 Nov 2008, Yasunori Goto wrote: > But our box supports both of 32bit I/O and 64bit I/O without IOMMU. > Is it abnormal platform? New interface is necessary for our box like Altix? No its like x86 with the GFP_DMA zone for < 16M addresses. The special memory creates an imbalance that sometimes leads to weird VM behavior. I'd make sure to set GFP_DMA only for devices that actually require < 4GB memory and only use it if no IOMMU like stuff is available. Its best to not use GFP_DMA. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/