From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 6D96C6B00EB for ; Thu, 16 Jun 2011 00:20:59 -0400 (EDT) Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [202.81.31.246]) by e23smtp09.au.ibm.com (8.14.4/8.13.1) with ESMTP id p5G4KnCY032679 for ; Thu, 16 Jun 2011 14:20:49 +1000 Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p5G4JumA1351846 for ; Thu, 16 Jun 2011 14:19:57 +1000 Received: from d23av02.au.ibm.com (loopback [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p5G4KmVx016822 for ; Thu, 16 Jun 2011 14:20:48 +1000 Date: Thu, 16 Jun 2011 09:50:44 +0530 From: Ankita Garg Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Message-ID: <20110616042044.GA28563@in.ibm.com> Reply-To: Ankita Garg References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110613134701.2b23b8d8.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110613134701.2b23b8d8.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki 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 Hi, On Mon, Jun 13, 2011 at 01:47:01PM +0900, KAMEZAWA Hiroyuki wrote: > On Fri, 27 May 2011 18:01:28 +0530 > Ankita Garg wrote: > > > Hi, > > > > I'm sorry if you've answered already. > > Is memory hotplug is too bad and cannot be enhanced for this purpose ? > > I wonder > - make section-size smaller (IIUC, IBM's system has 16MB section size) > > - add per section statistics > > - add a kind of balloon driver which does software memory offline > (which means making a contiguous chunk of free pages of section_size > by page migration) in background with regard to memory usage statistics. > If system says "need more memory!", balloon driver can online pages. > > can work for your purpose. It can allow you page isolatation and > controls in 16MB unit. If you need whole rework of memory hotplug, I think > it's better to rewrite memory hotplug, too. > Interesting idea, but a few issues - - Correctly predicting memory pressure is difficult and thereby being able to online the required pages at the right time could be a challenge - Memory hotplug is a heavy operation, so the overhead involved may be high - Powering off memory is just one of the ways in which memory power could be saved. The platform can also dynamically transition areas of memory into a content-preserving lower power state if it is not referenced for a pre-defined threshold of time. In such a case, we would need a mechanism to soft offline the pages - i.e, no new allocations to be directed to that memory -- 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