Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753589Ab1FOHil (ORCPT ); Wed, 15 Jun 2011 03:38:41 -0400 Received: from moutng.kundenserver.de ([212.227.17.9]:54195 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753007Ab1FOHik (ORCPT ); Wed, 15 Jun 2011 03:38:40 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 08/10] mm: cma: Contiguous Memory Allocator added Date: Wed, 15 Jun 2011 09:37:18 +0200 User-Agent: KMail/1.13.6 (Linux/3.0.0-rc1nosema+; KDE/4.6.3; x86_64; ; ) 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 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> X-Provags-ID: V02:K0:seWrADaN+nWac43q5MaUu3druobV+Rm/7Nu9GkJZ+/k eTXUa37QM2bH74yZ6RWmmRTkKnDwwCA9oi3ExGPfjZHuH7XNvH RI3g+v2H80VtblH/pfvqoBhlxwkam/9XXsZNVhoYlg1uNtQ773 bh7rUA2nXplZ5KElpI9cLh1PcE2hkzZ2RIal2Zr1J9na/B9vXG 9w5KHAuLq576hoYJ/7Mbg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1581 Lines: 32 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 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/