From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 041019000C2 for ; Thu, 7 Jul 2011 14:00:54 -0400 (EDT) Received: by bwb11 with SMTP id 11so1149473bwb.9 for ; Thu, 07 Jul 2011 11:00:50 -0700 (PDT) Date: Thu, 7 Jul 2011 21:00:44 +0300 (EEST) From: Pekka Enberg Subject: Re: [PATCH 00/10] mm: Linux VM Infrastructure to support Memory Power Management In-Reply-To: Message-ID: 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; format=flowed Sender: owner-linux-mm@kvack.org List-ID: To: david@lang.hm Cc: Ankita Garg , 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 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 | > On Wed, 6 Jul 2011, david@lang.hm wrote: > 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) > > 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. But drivers allocate DMA memory for hardware during module load and stay pinned there until the driver is unloaded, no? So in practice DMA buffers are going to be in banks 0-1? Pekka -- 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