Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753355AbZF1HmT (ORCPT ); Sun, 28 Jun 2009 03:42:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751752AbZF1HmG (ORCPT ); Sun, 28 Jun 2009 03:42:06 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50225 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751617AbZF1HmE (ORCPT ); Sun, 28 Jun 2009 03:42:04 -0400 Message-ID: <4A471F01.7010400@redhat.com> Date: Sun, 28 Jun 2009 10:42:57 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Lightning/1.0pre Thunderbird/3.0b2 MIME-Version: 1.0 To: Linus Walleij CC: Dan Magenheimer , linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com, npiggin@suse.de, chris.mason@oracle.com, kurt.hackel@oracle.com, dave.mccracken@oracle.com, jeremy@goop.org, Rik van Riel , alan@lxorguk.ukuu.org.uk, Rusty Russell , Martin Schwidefsky , akpm@osdl.org, Marcelo Tosatti , Balbir Singh , tmem-devel@oss.oracle.com, sunil.mushran@oracle.com, linux-mm@kvack.org, Himanshu Raj , linux-embedded@vger.kernel.org Subject: Re: [RFC] transcendent memory for Linux References: <63386a3d0906270618h5be01265v759f5acd1f49682f@mail.gmail.com> In-Reply-To: <63386a3d0906270618h5be01265v759f5acd1f49682f@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1989 Lines: 50 On 06/27/2009 04:18 PM, Linus Walleij wrote: > 2009/6/20 Dan Magenheimer: > > >> We call this latter class "transcendent memory" and it >> provides an interesting opportunity to more efficiently >> utilize RAM in a virtualized environment. However this >> "memory but not really memory" may also have applications >> in NON-virtualized environments, such as hotplug-memory >> deletion, SSDs, and page cache compression. Others have >> suggested ideas such as allowing use of highmem memory >> without a highmem kernel, or use of spare video memory. >> > > Here is what I consider may be a use case from the embedded > world: we have to save power as much as possible, so we need > to shut off entire banks of memory. > > Currently people do things like put memory into self-refresh > and then sleep, but for long lapses of time you would > want to compress memory towards lower addresses and > turn as many banks as possible off. > > So we have something like 4x16MB banks of RAM = 64MB RAM, > and the most necessary stuff easily fits in one of them. > If we can shut down 3x16MB we save 3 x power supply of the > RAMs. > > However in embedded we don't have any swap, so we'd need > some call that would attempt to remove a memory by paging > out code and data that has been demand-paged in > from the FS but no dirty pages, these should instead be > moved down to memory which will be retained, and the > call should fail if we didn't succeed to migrate all > dirty pages. > > Would this be possible with transcendent memory? > You could do this with memory defragmentation, which is needed for things like memory hotunplug ayway. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/