From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751500AbdJDRJR (ORCPT ); Wed, 4 Oct 2017 13:09:17 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:17746 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751240AbdJDRJP (ORCPT ); Wed, 4 Oct 2017 13:09:15 -0400 Subject: Re: [RFC] mmap(MAP_CONTIG) To: Michal Nazarewicz , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org Cc: Marek Szyprowski , "Aneesh Kumar K.V" , Joonsoo Kim , Guy Shattah , Christoph Lameter References: <21f1ec96-2822-1189-1c95-79a2bb491571@oracle.com> From: Mike Kravetz Message-ID: Date: Wed, 4 Oct 2017 10:08:50 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Source-IP: userv0021.oracle.com [156.151.31.71] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/04/2017 04:54 AM, Michal Nazarewicz wrote: > On Tue, Oct 03 2017, Mike Kravetz wrote: >> At Plumbers this year, Guy Shattah and Christoph Lameter gave a presentation >> titled 'User space contiguous memory allocation for DMA' [1]. The slides >> point out the performance benefits of devices that can take advantage of >> larger physically contiguous areas. > > Issue I have is that kind of memory needed may depend on a device. Some > may require contiguous blocks. Some may support scatter-gather. Some > may be behind IO-MMU and not care either way. > > Furthermore, I feel déjà vu. Wasn’t dmabuf supposed to address this > issue? Thanks Michal, I was unaware of dmabuf and am just now looking at capabilities. The question is whether or not the IB driver writers requesting mmap(MAP_CONTIG) functionality could make use of dmabuf. That is out of my are of expertise, so I will let them reply. -- Mike Kravetz