Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752686Ab0HZEpM (ORCPT ); Thu, 26 Aug 2010 00:45:12 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:35851 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750906Ab0HZEpK (ORCPT ); Thu, 26 Aug 2010 00:45:10 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Thu, 26 Aug 2010 13:39:54 +0900 From: KAMEZAWA Hiroyuki To: =?UTF-8?B?TWljaGHFgg==?= Nazarewicz Cc: FUJITA Tomonori , Daniel Walker , Russell King , Jonathan Corbet , Peter Zijlstra , Pawel Osciak , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, Mel Gorman , Hans Verkuil , linux-mm@kvack.org, Kyungmin Park , Zach Pfeffer , Mark Brown , Andrew Morton , Marek Szyprowski , linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org Subject: Re: [PATCH/RFCv4 0/6] The Contiguous Memory Allocator framework Message-Id: <20100826133954.4433fdf2.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <1282310110.2605.976.camel@laptop> <20100825155814.25c783c7.akpm@linux-foundation.org> <20100826095857.5b821d7f.kamezawa.hiroyu@jp.fujitsu.com> <20100826115017.04f6f707.kamezawa.hiroyu@jp.fujitsu.com> <20100826124434.6089630d.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2623 Lines: 70 On Thu, 26 Aug 2010 06:01:56 +0200 Michał Nazarewicz wrote: > KAMEZAWA Hiroyuki wrote: > > 128MB...too big ? But it's depend on config. > > On embedded systems it may be like half of the RAM. Or a quarter. So bigger > granularity could be desired on some platforms. > > > IBM's ppc guys used 16MB section, and recently, a new interface to shrink > > the number of /sys files are added, maybe usable. > > > > Something good with this approach will be you can create "cma" memory > > before installing driver. > > That's how CMA works at the moment. But if I understand you correctly, what > you are proposing would allow to reserve memory *at* *runtime* long after system > has booted. This would be a nice feature as well though. > Yes, my proposal is that. > > But yes, complicated and need some works. > > > Ah, I need to clarify what I want to say. > > > > With compaction, it's helpful, but you can't get contiguous memory larger > > than MAX_ORDER, I think. To get memory larger than MAX_ORDER on demand, > > memory hot-plug code has almost all necessary things. > > I'll try to look at it then. > mm/memory_hotplug.c::offline_pages() does 1. disallow new allocation of memory in [start_pfn...end_pfn) 2. move all LRU pages to other regions than [start_pfn...end_pfn) 3. finally, mark all pages as PG_reserved (see __offline_isolated_pages()) What's required for cma will be a. remove _section_ limitation, which is done as BUG_ON(). b. replace 'step 3' with cma code. Maybe you can do similar just using compaction logic. The biggest difference will be 'step 1'. > > BTW, just curious...the memory for cma need not to be saved at > > hibernation ? Or drivers has to write its own hibernation ops by driver suspend > > udev or some ? > > Hibernation was not considered as of yet but I think it's device driver's > responsibility more then CMA's especially since it may make little sense to save > some of the buffers -- ie. no need to keep a frame from camera since it'll be > overwritten just after system wakes up from hibernation. It may also be better > to stop playback and resume it later on rather than trying to save decoder's > state. Again though, I haven't thought about hibernation as of yet. > Hmm, ok, use-case dependent and it's a job of a driver. Thanks, -Kame -- 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/