From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752096Ab1GGEyy (ORCPT ); Thu, 7 Jul 2011 00:54:54 -0400 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:39721 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750791Ab1GGEyv (ORCPT ); Thu, 7 Jul 2011 00:54:51 -0400 Date: Thu, 7 Jul 2011 10:24:20 +0530 From: Ankita Garg To: david@lang.hm Cc: Pekka Enberg , 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, Dave Hansen , "Paul E. McKenney" , KAMEZAWA Hiroyuki , Matthew Garrett , Arjan van de Ven , Christoph Lameter Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management Message-ID: <20110707045420.GA23595@in.ibm.com> Reply-To: Ankita Garg References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110629130038.GA7909@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 06, 2011 at 01:20:55PM -0700, david@lang.hm wrote: > On Wed, 6 Jul 2011, Pekka Enberg wrote: > > >Why does the allocator need to know about address boundaries? Why > >isn't it enough to make the page allocator and reclaim policies favor using > >memory from lower addresses as aggressively as possible? That'd mean > >we'd favor the first memory banks and could keep the remaining ones > >powered off as much as possible. > > > >IOW, why do we need to support scenarios such as this: > > > > bank 0 bank 1 bank 2 bank3 > >| online | offline | online | offline | > > I believe that there are memory allocations that cannot be moved > after they are made (think about regions allocated to DMA from > hardware where the hardware has already been given the address space > to DMA into) > Thats true. These are kernel allocations which are not movable. However, the ZONE_MOVABLE would enable us to create complete movable zones and the ones that have the kernel allocations could be flagged as kernelcore zone. > As a result, you may not be able to take bank 2 offline, so your > option is to either leave banks 0-2 all online, or support emptying > bank 1 and taking it offline. > -- Regards, Ankita Garg (ankita@in.ibm.com) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India