Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754926Ab1EDAUZ (ORCPT ); Tue, 3 May 2011 20:20:25 -0400 Received: from terminus.zytor.com ([198.137.202.10]:50323 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754683Ab1EDAUY (ORCPT ); Tue, 3 May 2011 20:20:24 -0400 Message-ID: <4DC09BBA.6040906@zytor.com> Date: Tue, 03 May 2011 17:20:10 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: David Rientjes CC: Ingo Molnar , Thomas Gleixner , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch v3] x86: allow ZONE_DMA to be configurable References: <4DA82F33.7080403@ladisch.de> <4DA8A5CE.2010004@zytor.com> <4DAFAD9F.4020809@zytor.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1405 Lines: 37 On 05/03/2011 05:00 PM, David Rientjes wrote: > On Wed, 27 Apr 2011, David Rientjes wrote: > >> ZONE_DMA is unnecessary for a large number of machines that do not >> require addressing in the lower 16MB of memory because they do not use >> devices with 16-bit address registers (plus one page byte register). >> >> This patch allows users to disable ZONE_DMA for x86 if they know they >> will not be using such devices with their kernel. >> >> This prevents the VM from unnecessarily reserving a ratio of memory >> (defaulting to 1/256th of system capacity) with lowmem_reserve_ratio >> for such allocations when it will never be used. >> >> Signed-off-by: David Rientjes > > Peter, is this ready for merge? + DMA memory allocation support allows devices with 16-bit address + registers to allocate memory within the first 16MB of address space. + Disable if no such devices will be used. This is still not correct... this is for devices with less than a 32-bit mask, not just for things that have 24-bit (not 16-bit!) DMA address restrictions. Please get this right. Other than that, I don't have any technical objections. -hpa -- 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/