Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031190AbbDWWh7 (ORCPT ); Thu, 23 Apr 2015 18:37:59 -0400 Received: from gate.crashing.org ([63.228.1.57]:33688 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031006AbbDWWh5 (ORCPT ); Thu, 23 Apr 2015 18:37:57 -0400 Message-ID: <1429828650.4915.51.camel@kernel.crashing.org> Subject: Re: Interacting with coherent memory on external devices From: Benjamin Herrenschmidt To: Austin S Hemmelgarn Cc: Christoph Lameter , "Paul E. McKenney" , Jerome Glisse , linux-kernel@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com, mgorman@suse.de, aarcange@redhat.com, riel@redhat.com, airlied@redhat.com, aneesh.kumar@linux.vnet.ibm.com, Cameron Buschardt , Mark Hairgrove , Geoffrey Gerfin , John McKenna , akpm@linux-foundation.org Date: Fri, 24 Apr 2015 08:37:30 +1000 In-Reply-To: <55390EE1.8020304@gmail.com> References: <20150421214445.GA29093@linux.vnet.ibm.com> <20150422000538.GB6046@gmail.com> <20150422131832.GU5561@linux.vnet.ibm.com> <1429756200.4915.19.camel@kernel.crashing.org> <55390EE1.8020304@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.10-0ubuntu1~14.10.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1487 Lines: 32 On Thu, 2015-04-23 at 11:25 -0400, Austin S Hemmelgarn wrote: > Looking at this whole conversation, all I see is two different views on > how to present the asymmetric multiprocessing arrangements that have > become commonplace in today's systems to userspace. Your model favors > performance, while CAPI favors simplicity for userspace. I would say it differently.... when you say "CAPI favors..." it's not CAPI, it's the usage model we are proposing as an option for CAPI and other similar technology (there's at least one other I can't quite talk about yet), but basically anything that has the characteristics defined in the document Paul posted. CAPI is just one such example. On another hand, CAPI can also perfectly be used as Christoph describes. The ability to transparently handle and migrate memory is not exclusive with the ability for an application to explicitly decide where to allocate its memory and explicitly move the data around. Both options will be provided. Before the thread degraded into a debate on usage model, this was an attempt at discussing the technical details of what would be the best approach to implement the "transparent" model in Linux. I'd like to go back to it if possible ... Cheers, Ben. -- 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/