From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 430A46B00EE for ; Wed, 29 Jun 2011 13:59:21 -0400 (EDT) Received: from d01relay07.pok.ibm.com (d01relay07.pok.ibm.com [9.56.227.147]) by e4.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p5THbRRb029103 for ; Wed, 29 Jun 2011 13:37:27 -0400 Received: from d01av03.pok.ibm.com (d01av03.pok.ibm.com [9.56.224.217]) by d01relay07.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5THxHuc1503444 for ; Wed, 29 Jun 2011 13:59:17 -0400 Received: from d01av03.pok.ibm.com (loopback [127.0.0.1]) by d01av03.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5TDx4kh025553 for ; Wed, 29 Jun 2011 10:59:05 -0300 Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management From: Dave Hansen In-Reply-To: <20110629174220.GA9152@in.ibm.com> References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110629130038.GA7909@in.ibm.com> <1309367184.11430.594.camel@nimitz> <20110629174220.GA9152@in.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 29 Jun 2011 10:59:02 -0700 Message-ID: <1309370342.11430.604.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ankita Garg 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 On Wed, 2011-06-29 at 23:12 +0530, Ankita Garg wrote: > 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 Having statistics like this would certainly be nice, but how important _is_ it? Is it really a show-stopper? There's some stuff today, like the NPT/EPT support in KVM where we don't even have visibility in to when a given page is referenced. It's also going to be a pain to track kernel references. On x86, our kernel linear mapping uses 1GB pages when it can, and those are greater than the 512MB granularity that we've been talking about here. It's even larger on powerpc. I'm also pretty sure we don't even _look_ at the referenced bits in the kernel page tables. We'll definitely need some infrastructure to do that. > 5. Being able to group these pieces of hardware for purpose of > higher savings. Do you really mean group, or do you mean "turn as many off as possible"? -- Dave -- 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