From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754679AbbDXOOM (ORCPT ); Fri, 24 Apr 2015 10:14:12 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:49137 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752246AbbDXOOJ (ORCPT ); Fri, 24 Apr 2015 10:14:09 -0400 Date: Fri, 24 Apr 2015 07:13:59 -0700 From: "Paul E. McKenney" To: Christoph Lameter 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 Message-ID: <20150424141359.GX5561@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20150422000538.GB6046@gmail.com> <20150422131832.GU5561@linux.vnet.ibm.com> <20150422170737.GB4062@gmail.com> <20150422185230.GD5561@linux.vnet.ibm.com> <20150423192456.GQ5561@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15042414-0005-0000-0000-00000A5067E3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 24, 2015 at 09:01:47AM -0500, Christoph Lameter wrote: > On Thu, 23 Apr 2015, Paul E. McKenney wrote: > > > > As far as I know Jerome is talkeing about HPC loads and high performance > > > GPU processing. This is the same use case. > > > > The difference is sensitivity to latency. You have latency-sensitive > > HPC workloads, and Jerome is talking about HPC workloads that need > > high throughput, but are insensitive to latency. > > Those are correlated. In some cases, yes. But are you -really- claiming that -all- HPC workloads are highly sensitive to latency? That would be quite a claim! > > > 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. > > > > You do need the low-latency Ferrari. But others are best served by a > > high-throughput freight train. > > The problem is that they want to run 2000 trains at the same time > and they all must arrive at the destination before they can be send on > their next trip. 1999 trains will be sitting idle because they need > to wait of the one train that was delayed. This reduces the troughput. > People really would like all 2000 trains to arrive on schedule so that > they get more performance. Yes, there is some portion of the market that needs both high throughput and highly predictable latencies. You are claiming that the -entire- HPC market has this sort of requirement? Again, this would be quite a claim! Thanx, Paul