From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.geekisp.com ([216.168.135.169]:41456 "EHLO starfish.geekisp.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753399Ab1FPAy6 (ORCPT ); Wed, 15 Jun 2011 20:54:58 -0400 Message-ID: <4DF952CC.4010301@balister.org> Date: Wed, 15 Jun 2011 17:48:12 -0700 From: Philip Balister MIME-Version: 1.0 To: Arnd Bergmann CC: linux-arm-kernel@lists.infradead.org, 'Daniel Walker' , linux-mm@kvack.org, 'Mel Gorman' , linux-kernel@vger.kernel.org, 'Michal Nazarewicz' , linaro-mm-sig@lists.linaro.org, 'Jesse Barker' , 'Kyungmin Park' , 'Ankita Garg' , 'Andrew Morton' , linux-media@vger.kernel.org, 'KAMEZAWA Hiroyuki' Subject: Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added References: <1307699698-29369-1-git-send-email-m.szyprowski@samsung.com> <201106142030.07549.arnd@arndb.de> <000501cc2b2b$789a54b0$69cefe10$%szyprowski@samsung.com> <201106150937.18524.arnd@arndb.de> In-Reply-To: <201106150937.18524.arnd@arndb.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-ID: Sender: On 06/15/2011 12:37 AM, Arnd Bergmann wrote: > On Wednesday 15 June 2011 09:11:39 Marek Szyprowski wrote: >> I see your concerns, but I really wonder how to determine the properties >> of the global/default cma pool. You definitely don't want to give all >> available memory o CMA, because it will have negative impact on kernel >> operation (kernel really needs to allocate unmovable pages from time to >> time). > > Exactly. This is a hard problem, so I would prefer to see a solution for > coming up with reasonable defaults. Is this a situation where passing the information from device tree might help? I know this does not help short term, but I am trying to understand the sorts of problems device tree can help solve. Philip > >> The only solution I see now is to provide Kconfig entry to determine >> the size of the global CMA pool, but this still have some issues, >> especially for multi-board kernels (each board probably will have >> different amount of RAM and different memory-consuming devices >> available). It looks that each board startup code still might need to >> tweak the size of CMA pool. I can add a kernel command line option for >> it, but such solution also will not solve all the cases (afair there >> was a discussion about kernel command line parameters for memory >> configuration and the conclusion was that it should be avoided). > > The command line option can be a last resort if the heuristics fail, > but it's not much better than a fixed Kconfig setting. > > How about a Kconfig option that defines the percentage of memory > to set aside for contiguous allocations? > > Arnd > > _______________________________________________ > Linaro-mm-sig mailing list > Linaro-mm-sig@lists.linaro.org > http://lists.linaro.org/mailman/listinfo/linaro-mm-sig >