From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id D17276B00EE for ; Wed, 29 Jun 2011 13:43:21 -0400 (EDT) Received: from d23relay05.au.ibm.com (d23relay05.au.ibm.com [202.81.31.247]) by e23smtp03.au.ibm.com (8.14.4/8.13.1) with ESMTP id p5THcB2s000839 for ; Thu, 30 Jun 2011 03:38:11 +1000 Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5THfwk41269794 for ; Thu, 30 Jun 2011 03:41:58 +1000 Received: from d23av01.au.ibm.com (loopback [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5THhH6x006195 for ; Thu, 30 Jun 2011 03:43:17 +1000 Date: Wed, 29 Jun 2011 23:12:20 +0530 From: Ankita Garg Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Message-ID: <20110629174220.GA9152@in.ibm.com> Reply-To: Ankita Garg References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110629130038.GA7909@in.ibm.com> <1309367184.11430.594.camel@nimitz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1309367184.11430.594.camel@nimitz> Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: 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, "Paul E. McKenney" , KAMEZAWA Hiroyuki , Matthew Garrett , Arjan van de Ven Hi, On Wed, Jun 29, 2011 at 10:06:24AM -0700, Dave Hansen wrote: > I was kinda hoping for something a bit simpler than that. I'd boil down > what you were saying to this: > > 1. The kernel must be aware of how the pieces of hardware are > mapped in to the system's physical address space > 2. The kernel must have a mechanism in place to minimize access to > specific pieces of hardware > 3. For destructive power-down operations, the kernel should have a > mechanism in place to ensure that no valuable data is contained > in the memory to be powered down. > 4. The kernel must have a mechanism to maintain utilization statistics pertaining to a piece of hardware, so that it can trigger the hardware to power it off 5. Being able to group these pieces of hardware for purpose of higher savings. > Is that complete? > > On Wed, 2011-06-29 at 18:30 +0530, Ankita Garg wrote: > > 1) Dynamic Power Transition: The memory controller can have the ability > > to automatically transition regions of memory into lower power states > > when they are devoid of references for a pre-defined threshold amount of > > time. Memory contents are preserved in the low power states and accessing > > memory that is at a low power state takes a latency hit. > > > > 2) Dynamic Power Off: If a region is free/unallocated, the software can > > indicate to the controller to completely turn off power to a certain > > region. Memory contents are lost and hence the software has to be > > absolutely sure about the usage statistics of the particular region. This > > is a runtime capability, where the required amount of memory can be > > powered 'ON' to match the workload demands. > > > > 3) Partial Array Self-Refresh (PASR): If a certain regions of memory is > > free/unallocated, the software can indicate to the controller to not > > refresh that region when the system goes to suspend-to-ram state and > > thereby save standby power consumption. > > (3) is simply a subset of (2), but with the additional restriction that > the power off can only occur during a suspend operation. > > Let's say we fully implemented support for (2). What would be missing > to support PASR? > Yes, PASR is a subset of (2) from implementation perspective. -- Regards, Ankita Garg (ankita@in.ibm.com) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India -- 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