From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id D6CF66B0012 for ; Sat, 11 Jun 2011 13:08:32 -0400 (EDT) Received: from d01relay04.pok.ibm.com (d01relay04.pok.ibm.com [9.56.227.236]) by e3.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p5BGk23i018604 for ; Sat, 11 Jun 2011 12:46:02 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay04.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5BH8Vdl114312 for ; Sat, 11 Jun 2011 13:08:31 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5BH8U9r027932 for ; Sat, 11 Jun 2011 13:08:31 -0400 Date: Sat, 11 Jun 2011 10:08:29 -0700 From: "Paul E. McKenney" Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Message-ID: <20110611170829.GB2212@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110528005640.9076c0b1.akpm@linux-foundation.org> <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> <20110610173345.GA8434@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110610173345.GA8434@in.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Ankita Garg Cc: Matthew Garrett , Kyungmin Park , linux-kernel@vger.kernel.org, linux-mm@kvack.org, thomas.abraham@linaro.org, Andrew Morton , svaidy@linux.vnet.ibm.com, linux-pm@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org On Fri, Jun 10, 2011 at 11:03:45PM +0530, Ankita Garg wrote: > On Fri, Jun 10, 2011 at 10:19:39AM -0700, Paul E. McKenney wrote: > > On Fri, Jun 10, 2011 at 06:05:35PM +0100, Matthew Garrett wrote: > > > On Fri, Jun 10, 2011 at 09:55:29AM -0700, Paul E. McKenney wrote: > > > > On Fri, Jun 10, 2011 at 04:59:54PM +0100, Matthew Garrett wrote: > > > > > For the server case, the low hanging fruit would seem to be > > > > > finer-grained self-refresh. At best we seem to be able to do that on a > > > > > per-CPU socket basis right now. The difference between active and > > > > > self-refresh would seem to be much larger than the difference between > > > > > self-refresh and powered down. > > > > > > > > By "finer-grained self-refresh" you mean turning off refresh for banks > > > > of memory that are not being used, right? If so, this is supported by > > > > the memory-regions support provided, at least assuming that the regions > > > > can be aligned with the self-refresh boundaries. > > > > > > I mean at the hardware level. As far as I know, the best we can do at > > > the moment is to put an entire node into self refresh when the CPU hits > > > package C6. > > > > But this depends on the type of system and CPU family, right? If you > > can say, which hardware are you thinking of? (I am thinking of ARM.) > > > > And also whether the memory controller is on-chip or off-chip ? As > package could be in C6, but other packages could be refering memory > connected to this socket right ? And as Paul mentioned, at this point > the ARM SoCs that have support for memory power management, have only a > single node. I suspect that this will be changing shortly, and that finer-grained control might be available. However, there are also use cases where contiguous memory is required from time to time by media codecs, and being able to use that memory for other purposes when the media codec is not in use reduced the total amount of memory required, which reduces power consumption all the time, right? ;-) Thanx, Paul -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org