Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757707AbbDWOMl (ORCPT ); Thu, 23 Apr 2015 10:12:41 -0400 Received: from resqmta-po-03v.sys.comcast.net ([96.114.154.162]:48978 "EHLO resqmta-po-03v.sys.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756996AbbDWOMk (ORCPT ); Thu, 23 Apr 2015 10:12:40 -0400 Date: Thu, 23 Apr 2015 09:12:38 -0500 (CDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: "Paul E. McKenney" cc: 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, 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 In-Reply-To: <20150422185230.GD5561@linux.vnet.ibm.com> Message-ID: References: <20150421214445.GA29093@linux.vnet.ibm.com> <20150422000538.GB6046@gmail.com> <20150422131832.GU5561@linux.vnet.ibm.com> <20150422170737.GB4062@gmail.com> <20150422185230.GD5561@linux.vnet.ibm.com> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1262 Lines: 27 On Wed, 22 Apr 2015, Paul E. McKenney wrote: > Agreed, the use case that Jerome is thinking of differs from yours. > You would not (and should not) tolerate things like page faults because > it would destroy your worst-case response times. I believe that Jerome > is more interested in throughput with minimal change to existing code. As far as I know Jerome is talkeing about HPC loads and high performance GPU processing. This is the same use case. > Let's suppose that you and Jerome were using GPGPU hardware that had > 32,768 hardware threads. You would want very close to 100% of the full > throughput out of the hardware with pretty much zero unnecessary latency. > In contrast, Jerome might be OK with (say) 20,000 threads worth of > throughput with the occasional latency hiccup. > > And yes, support for both use cases is needed. What you are proposing for High Performacne Computing is reducing the performance these guys trying to get. You cannot sell someone a Volkswagen if he needs the Ferrari. -- 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/