From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Srivatsa S. Bhat" Subject: Re: [RFC PATCH v2 00/15][Sorted-buddy] mm: Memory Power Management Date: Thu, 25 Apr 2013 23:27:12 +0530 Message-ID: <51796E78.20203@linux.vnet.ibm.com> References: <20130409214443.4500.44168.stgit@srivatsabhat.in.ibm.com> <517028F1.6000002@sr71.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from e28smtp04.in.ibm.com ([122.248.162.4]:34080 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933155Ab3DYSAU (ORCPT ); Thu, 25 Apr 2013 14:00:20 -0400 Received: from /spool/local by e28smtp04.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 25 Apr 2013 23:25:51 +0530 In-Reply-To: <517028F1.6000002@sr71.net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Dave Hansen Cc: akpm@linux-foundation.org, mgorman@suse.de, matthew.garrett@nebula.com, rientjes@google.com, riel@redhat.com, arjan@linux.intel.com, srinivas.pandruvada@linux.intel.com, maxime.coquelin@stericsson.com, loic.pallardy@stericsson.com, kamezawa.hiroyu@jp.fujitsu.com, lenb@kernel.org, rjw@sisk.pl, gargankita@gmail.com, paulmck@linux.vnet.ibm.com, amit.kachhap@linaro.org, svaidy@linux.vnet.ibm.com, andi@firstfloor.org, wujianguo@huawei.com, kmpark@infradead.org, thomas.abraham@linaro.org, santosh.shilimkar@ti.com, linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 04/18/2013 10:40 PM, Dave Hansen wrote: > On 04/09/2013 02:45 PM, Srivatsa S. Bhat wrote: >> 2. Performance overhead is expected to be low: Since we retain the s= implicity >> of the algorithm in the page allocation path, page allocation can >> potentially remain as fast as it would be without memory regions.= The >> overhead is pushed to the page-freeing paths which are not that c= ritical. >=20 [...] =20 > I still also want to see some hard numbers on: >> However, memory consumes a significant amount of power, potentially = upto >> more than a third of total system power on server systems. Please find below, the reference to the publicly available paper I had = in mind, when I made that statement: C. Lefurgy, K. Rajamani, F. Rawson, W. Felter, M. Kistler, and Tom Kell= er. Energy management for commercial servers. In IEEE Computer, pages 39=E2= =80=9348, Dec 2003. Here is a quick link to the paper: researcher.ibm.com/files/us-lefurgy/computer2003.pdf On page 40, the paper shows the power-consumption breakdown for an IBM = p670 machine, which shows that as much as 40% of the system energy is consum= ed by the memory sub-system in a mid-range server. I admit that the paper is a little old (I'll see if I can find anything= more recent that is publicly available, or perhaps you can verify the same i= f you have data-sheets for other platforms handy), but given the trend of inc= reasing memory speeds and increasing memory density/capacity in computer system= s, the power-consumption of memory is certainly not going to become insignific= ant all of a sudden. IOW, the above data supports the point I was trying to make - Memory ha= rdware contributes to a significant portion of the power consumption of a syst= em. And since the hardware is now exposing ways to reduce the power consumption= , it would be worthwhile to try and exploit it by doing memory power managem= ent. Regards, Srivatsa S. Bhat