From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id E38B96B002C for ; Tue, 11 Oct 2011 03:34:35 -0400 (EDT) Message-ID: <4E93F088.60006@stericsson.com> Date: Tue, 11 Oct 2011 09:30:16 +0200 From: Maxime Coquelin MIME-Version: 1.0 Subject: Re: [Linaro-mm-sig] [PATCHv16 0/9] Contiguous Memory Allocator References: <1317909290-29832-1-git-send-email-m.szyprowski@samsung.com> <4E92E003.4060901@stericsson.com> <00b001cc87e5$dc818cc0$9584a640$%szyprowski@samsung.com> In-Reply-To: <00b001cc87e5$dc818cc0$9584a640$%szyprowski@samsung.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Marek Szyprowski Cc: "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "linux-media@vger.kernel.org" , "linux-mm@kvack.org" , "linaro-mm-sig@lists.linaro.org" , 'Daniel Walker' , 'Russell King' , 'Arnd Bergmann' , 'Jonathan Corbet' , 'Mel Gorman' , 'Chunsang Jeong' , 'Michal Nazarewicz' , 'Dave Hansen' , 'Jesse Barker' , 'Kyungmin Park' , 'Ankita Garg' , 'Andrew Morton' , 'KAMEZAWA Hiroyuki' , "benjamin.gaignard@linaro.org" , Ludovic BARRE , "vincent.guittot@linaro.org" On 10/11/2011 09:17 AM, Marek Szyprowski wrote: > On Monday, October 10, 2011 2:08 PM Maxime Coquelin wrote: > > During our stress tests, we encountered some problems : > > 1) Contiguous allocation lockup: > When system RAM is full of Anon pages, if we try to allocate a > contiguous buffer greater than the min_free value, we face a > dma_alloc_from_contiguous lockup. > The expected result would be dma_alloc_from_contiguous() to fail. > The problem is reproduced systematically on our side. > Thanks for the report. Do you use Android's lowmemorykiller? I haven't > tested CMA on Android kernel yet. I have no idea how it will interfere > with Android patches. > The software used for this test (v16) is a generic 3.0 Kernel and a minimal filesystem using Busybox. With v15 patchset, I also tested it with Android. IIRC, sometimes the lowmemorykiller succeed to get free space and the contiguous allocation succeed, sometimes we faced the lockup. >> 2) Contiguous allocation fail: >> We have developed a small driver and a shell script to >> allocate/release contiguous buffers. >> Sometimes, dma_alloc_from_contiguous() fails to allocate the >> contiguous buffer (about once every 30 runs). >> We have 270MB Memory passed to the kernel in our configuration, >> and the CMA pool is 90MB large. >> In this setup, the overall memory is either free or full of >> reclaimable pages. > Yeah. We also did such stress tests recently and faced this issue. I've > spent some time investigating it but I have no solution yet. > > The problem is caused by a page, which is put in the CMA area. This page > is movable, but it's address space provides no 'migratepage' method. In > such case mm subsystem uses fallback_migrate_page() function. Sadly this > function only returns -EAGAIN. The migration loops a few times over it > and fails causing the fail in the allocation procedure. > > We are investing now which kernel code created/allocated such problematic > pages and how to add real migration support for them. > Ok, thanks for pointing this out. Regards, Maxime -- 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