From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 7C8AF6B025F for ; Wed, 4 Oct 2017 17:29:13 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id t134so5409204oih.6 for ; Wed, 04 Oct 2017 14:29:13 -0700 (PDT) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id q10sor13032667qtk.10.2017.10.04.14.29.12 for (Google Transport Security); Wed, 04 Oct 2017 14:29:12 -0700 (PDT) Subject: Re: [RFC] mmap(MAP_CONTIG) References: <21f1ec96-2822-1189-1c95-79a2bb491571@oracle.com> From: Laura Abbott Message-ID: <09210624-fb3a-4dc9-5720-49714dbef0f7@redhat.com> Date: Wed, 4 Oct 2017 14:29:08 -0700 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Mike Kravetz , 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 On 10/04/2017 10:08 AM, Mike Kravetz wrote: > 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 dA(C)jA vu. Wasna??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. > I don't think dmabuf as it exists today would help anything here. It's designed to share buffers via fd but you still need some place/driver to actually get the allocation and then export it since there isn't a single interface for allocations. You could convert drivers to take a dma_buf fd if there were appropriate buffers available though. Thanks, Laura -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org