From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753894AbYIJOx1 (ORCPT ); Wed, 10 Sep 2008 10:53:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751487AbYIJOxT (ORCPT ); Wed, 10 Sep 2008 10:53:19 -0400 Received: from outbound-dub.frontbridge.com ([213.199.154.16]:50341 "EHLO IE1EHSOBE004.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751078AbYIJOxS (ORCPT ); Wed, 10 Sep 2008 10:53:18 -0400 X-BigFish: VPS-30(zz1432R98dR1805M936fQzz10d3izzz32i6bh43j61h) X-Spam-TCS-SCL: 0:0 X-WSS-ID: 0K6ZIO0-03-CTC-01 Date: Wed, 10 Sep 2008 16:52:49 +0200 From: Joerg Roedel To: FUJITA Tomonori CC: linux-kernel@vger.kernel.org, mingo@elte.hu Subject: Re: [PATCH] x86: avoid unnecessary low zone allocation in AMD IOMMU's alloc_coherent Message-ID: <20080910145249.GB24392@amd.com> References: <20080910223735O.fujita.tomonori@lab.ntt.co.jp> <20080910135347.GI6329@amd.com> <20080910232446O.fujita.tomonori@lab.ntt.co.jp> <20080910233819T.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20080910233819T.fujita.tomonori@lab.ntt.co.jp> User-Agent: mutt-ng/devel-r804 (Linux) X-OriginalArrivalTime: 10 Sep 2008 14:52:49.0836 (UTC) FILETIME=[E515C6C0:01C91354] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 10, 2008 at 11:39:00PM +0900, FUJITA Tomonori wrote: > btw, in tip/x86/iommu, GART's alloc_coherent always does virtual > mappings to allocate a size-aligned memory (as DMA-mapping.txt > defines). > > Because someone strongly insisted, I modified GART's alloc_coherent to > do so but as I said again and again, it's completely meaningless (only > POWER IOMMU does it and drivers don't depend on such requirement). > > I guess that it would be better to do virtual mappings only when > necessary as the current mainline does since GART I/O space is > precious in some systems. But I don't care much. What's your opinion > (as a AMD developer)? Very true. My original rewrite did the mapping only when necessary too. What were the reasons to do the mapping always? Joerg -- | AMD Saxony Limited Liability Company & Co. KG Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany System | Register Court Dresden: HRA 4896 Research | General Partner authorized to represent: Center | AMD Saxony LLC (Wilmington, Delaware, US) | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy