Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754016Ab3IZSGk (ORCPT ); Thu, 26 Sep 2013 14:06:40 -0400 Received: from mga02.intel.com ([134.134.136.20]:17839 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753097Ab3IZSGi (ORCPT ); Thu, 26 Sep 2013 14:06:38 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.90,987,1371106800"; d="scan'208";a="409925495" Message-ID: <524477AC.9090400@linux.intel.com> Date: Thu, 26 Sep 2013 11:06:36 -0700 From: Arjan van de Ven User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: "Srivatsa S. Bhat" CC: Andrew Morton , Andi Kleen , mgorman@suse.de, dave@sr71.net, hannes@cmpxchg.org, tony.luck@intel.com, matthew.garrett@nebula.com, riel@redhat.com, srinivas.pandruvada@linux.intel.com, willy@linux.intel.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl, gargankita@gmail.com, paulmck@linux.vnet.ibm.com, svaidy@linux.vnet.ibm.com, isimatu.yasuaki@jp.fujitsu.com, santosh.shilimkar@ti.com, kosaki.motohiro@gmail.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, maxime.coquelin@stericsson.com, loic.pallardy@stericsson.com, thomas.abraham@linaro.org, amit.kachhap@linaro.org Subject: Re: [Results] [RFC PATCH v4 00/40] mm: Memory Power Management References: <20130925231250.26184.31438.stgit@srivatsabhat.in.ibm.com> <52437128.7030402@linux.vnet.ibm.com> <20130925164057.6bbaf23bdc5057c42b2ab010@linux-foundation.org> <20130925234734.GK18242@two.firstfloor.org> <52438AA9.3020809@linux.intel.com> <20130925182129.a7db6a0fd2c7cc3b43fda92d@linux-foundation.org> <20130926015016.GM18242@two.firstfloor.org> <20130925195953.826a9f7d.akpm@linux-foundation.org> <524439D5.8020306@linux.vnet.ibm.com> <52445993.7050608@linux.intel.com> <52446841.2030301@linux.vnet.ibm.com> In-Reply-To: <52446841.2030301@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1906 Lines: 48 >>>> >>> >>> Arjan, are you referring to the fact that Intel/SNB systems can exploit >>> memory self-refresh only when the entire system goes idle? Is that why >>> this >>> patchset won't turn out to be that useful on those platforms? >> >> no we can use other things (CKE and co) all the time. >> > > Ah, ok.. > >> just that we found that statistical grouping gave 95%+ of the benefit, >> without the cost of being aggressive on going to a 100.00% grouping >> > > And how do you do that statistical grouping? Don't you need patches similar > to those in this patchset? Or are you saying that the existing vanilla > kernel itself does statistical grouping somehow? so the way I scanned your patchset.. half of it is about grouping, the other half (roughly) is about moving stuff. the grouping makes total sense to me. actively moving is the part that I am very worried about; that part burns power to do (and performance).... for which the ROI is somewhat unclear to me (but... data speaks. I can easily be convinced with data that proves one way or the other) is moving stuff around the 95%-of-the-work-for-the-last-5%-of-the-theoretical-gain or is statistical grouping enough to get > 95% of the gain... without the cost of moving. > > Also, I didn't fully understand how NUMA policy will help in this case.. > If you want to group memory allocations/references into fewer memory regions > _within_ a node, will NUMA policy really help? For example, in this patchset, > everything (all the allocation/reference shaping) is done _within_ the > NUMA boundary, assuming that the memory regions are subsets of a NUMA node. > > Regards, > Srivatsa S. Bhat > -- 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/