Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758037Ab1FJSsV (ORCPT ); Fri, 10 Jun 2011 14:48:21 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:46853 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757622Ab1FJSsU (ORCPT ); Fri, 10 Jun 2011 14:48:20 -0400 Date: Fri, 10 Jun 2011 11:47:38 -0700 From: "Paul E. McKenney" To: Matthew Garrett Cc: Kyungmin Park , Andrew Morton , Ankita Garg , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-pm@lists.linux-foundation.org, svaidy@linux.vnet.ibm.com, thomas.abraham@linaro.org Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Message-ID: <20110610184738.GG2230@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110609185259.GA29287@linux.vnet.ibm.com> <20110610151121.GA2230@linux.vnet.ibm.com> <20110610155954.GA25774@srcf.ucam.org> <20110610165529.GC2230@linux.vnet.ibm.com> <20110610170535.GC25774@srcf.ucam.org> <20110610171939.GE2230@linux.vnet.ibm.com> <20110610172307.GA27630@srcf.ucam.org> <20110610175248.GF2230@linux.vnet.ibm.com> <20110610180807.GB28500@srcf.ucam.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110610180807.GB28500@srcf.ucam.org> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1667 Lines: 32 On Fri, Jun 10, 2011 at 07:08:07PM +0100, Matthew Garrett wrote: > On Fri, Jun 10, 2011 at 10:52:48AM -0700, Paul E. McKenney wrote: > > On Fri, Jun 10, 2011 at 06:23:07PM +0100, Matthew Garrett wrote: > > > I haven't seen too many ARM servers with 256GB of RAM :) I'm mostly > > > looking at this from an x86 perspective. > > > > But I have seen ARM embedded systems with CPU power consumption in > > the milliwatt range, which greatly reduces the amount of RAM required > > to get significant power savings from this approach. Three orders > > of magnitude less CPU power consumption translates (roughly) to three > > orders of magnitude less memory required -- and embedded devices with > > more than 256MB of memory are quite common. > > I'm not saying that powering down memory isn't a win, just that in the > server market we're not even getting unused memory into self refresh at > the moment. If we can gain that hardware capability then sub-node zoning > means that we can look at allocating (and migrating?) RAM in such a way > as to get a lot of the win that we'd gain from actually cutting the > power, without the added overhead of actually shrinking our working set. Agreed. And if I understand you correctly, then the patches that Ankita posted should help your self-refresh case, along with the originally intended the power-down case and special-purpose use of memory case. Thanx, Paul -- 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/