From mboxrd@z Thu Jan 1 00:00:00 1970 From: ankita@in.ibm.com (Ankita Garg) Date: Thu, 7 Jul 2011 10:24:20 +0530 Subject: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management In-Reply-To: References: <1306499498-14263-1-git-send-email-ankita@in.ibm.com> <20110629130038.GA7909@in.ibm.com> Message-ID: <20110707045420.GA23595@in.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Jul 06, 2011 at 01:20:55PM -0700, david at 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 at in.ibm.com) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India