From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx145.postini.com [74.125.245.145]) by kanga.kvack.org (Postfix) with SMTP id 5EFB16B0062 for ; Mon, 2 Jul 2012 03:56:23 -0400 (EDT) Received: by dakp5 with SMTP id p5so8606458dak.14 for ; Mon, 02 Jul 2012 00:56:22 -0700 (PDT) Message-ID: <4FF15417.8020609@gmail.com> Date: Mon, 02 Jul 2012 15:56:07 +0800 From: Nai Xia Reply-To: nai.xia@gmail.com MIME-Version: 1.0 Subject: Re: [PATCH 13/40] autonuma: CPU follow memory algorithm References: <1340888180-15355-1-git-send-email-aarcange@redhat.com> <1340888180-15355-14-git-send-email-aarcange@redhat.com> <1340895238.28750.49.camel@twins> <20120629125517.GD32637@gmail.com> <4FEDDD0C.60609@redhat.com> <1340995986.28750.114.camel@twins> <20120630012338.GY6676@redhat.com> <20120630124816.GZ6676@redhat.com> <4FEF1703.1070506@gmail.com> <4FF14F62.2040702@redhat.com> In-Reply-To: <4FF14F62.2040702@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: Andrea Arcangeli , Peter Zijlstra , dlaor@redhat.com, Ingo Molnar , Hillf Danton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dan Smith , Linus Torvalds , Andrew Morton , Thomas Gleixner , Ingo Molnar , Paul Turner , Suresh Siddha , Mike Galbraith , "Paul E. McKenney" , Lai Jiangshan , Bharata B Rao , Lee Schermerhorn , Johannes Weiner , Srivatsa Vaddagiri , Christoph Lameter , Alex Shi , Mauricio Faria de Oliveira , Konrad Rzeszutek Wilk , Don Morris , Benjamin Herrenschmidt On 2012a1'07ae??02ae?JPY 15:36, Rik van Riel wrote: > On 06/30/2012 11:10 AM, Nai Xia wrote: > >> Yes, pte_numa or pte_young works the same way and they both can >> answer the problem of "which pages were accessed since last scan". >> For LRU, it's OK, it's quite enough. But for numa balancing it's NOT. > > Getting LRU right may be much more important than getting > NUMA balancing right. > > Retrieving wrongly evicted data from disk can be a million > of times slower than fetching data from RAM, while the > penalty for accessing a remote NUMA node is only 20% or so. > >> We also should care about the hotness of the page sets, since if the >> workloads are complex we should NOT be expecting that "if this page >> is accessed once, then it's always in my CPU cache during the whole >> last scan interval". >> >> The difference between LRU and the problem you are trying to deal >> with looks so obvious to me, I am so worried that you are still >> messing them up :( > > For autonuma, it may be fine to have a lower likelyhood of > obtaining an optimum result, because the penalty for getting > it wrong is so much lower. I said, I am actually want to see some detailed analysis showing that this sampling is really playing an important role in benchmarks as it claims to be. Not a quick "lower likelyhood than optimum" conclusion..... Please, Rik, I know your points, you don't have to explain anymore. But I just cannot follow without research data. If you think I am wrong. It's ok to ignore me from now..... -- 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