Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966367AbbDWQEX (ORCPT ); Thu, 23 Apr 2015 12:04:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47854 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965646AbbDWQEV (ORCPT ); Thu, 23 Apr 2015 12:04:21 -0400 Message-ID: <553917F4.4080300@redhat.com> Date: Thu, 23 Apr 2015 12:04:04 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Christoph Lameter , Jerome Glisse CC: "Paul E. McKenney" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, mgorman@suse.de, aarcange@redhat.com, airlied@redhat.com, benh@kernel.crashing.org, aneesh.kumar@linux.vnet.ibm.com, Cameron Buschardt , Mark Hairgrove , Geoffrey Gerfin , John McKenna , akpm@linux-foundation.org Subject: Re: Interacting with coherent memory on external devices References: <20150421214445.GA29093@linux.vnet.ibm.com> <20150422000538.GB6046@gmail.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1403 Lines: 27 On 04/21/2015 08:50 PM, Christoph Lameter wrote: > On Tue, 21 Apr 2015, Jerome Glisse wrote: >> So big use case here, let say you have an application that rely on a >> scientific library that do matrix computation. Your application simply >> use malloc and give pointer to this scientific library. Now let say >> the good folks working on this scientific library wants to leverage >> the GPU, they could do it by allocating GPU memory through GPU specific >> API and copy data in and out. For matrix that can be easy enough, but >> still inefficient. What you really want is the GPU directly accessing >> this malloced chunk of memory, eventualy migrating it to device memory >> while performing the computation and migrating it back to system memory >> once done. Which means that you do not want some kind of filesystem or >> anything like that. > > With a filesystem the migration can be controlled by the application. Which is absolutely the wrong thing to do when using the "GPU" (or whatever co-processor it is) transparently from libraries, without the applications having to know about it. Your use case is legitimate, but so is this other case. -- 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/