From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id EE5246B0012 for ; Wed, 15 Jun 2011 03:37:39 -0400 (EDT) From: Arnd Bergmann Subject: Re: [PATCH 08/10] mm: cma: Contiguous Memory Allocator added Date: Wed, 15 Jun 2011 09:37:18 +0200 References: <1307699698-29369-1-git-send-email-m.szyprowski@samsung.com> <201106142030.07549.arnd@arndb.de> <000501cc2b2b$789a54b0$69cefe10$%szyprowski@samsung.com> In-Reply-To: <000501cc2b2b$789a54b0$69cefe10$%szyprowski@samsung.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201106150937.18524.arnd@arndb.de> Sender: owner-linux-mm@kvack.org List-ID: To: linux-arm-kernel@lists.infradead.org Cc: Marek Szyprowski , 'Michal Nazarewicz' , 'Ankita Garg' , 'Daniel Walker' , 'Jesse Barker' , 'Mel Gorman' , linux-kernel@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, 'Kyungmin Park' , 'KAMEZAWA Hiroyuki' , 'Andrew Morton' , linux-media@vger.kernel.org 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. > 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 -- 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