From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id A33566B002C for ; Tue, 11 Oct 2011 06:50:38 -0400 (EDT) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=us-ascii Received: from euspt1 ([210.118.77.13]) by mailout3.w1.samsung.com (Sun Java(tm) System Messaging Server 6.3-8.04 (built Jul 29 2009; 32bit)) with ESMTP id <0LSW009NBE4AW630@mailout3.w1.samsung.com> for linux-mm@kvack.org; Tue, 11 Oct 2011 11:50:34 +0100 (BST) Received: from linux.samsung.com ([106.116.38.10]) by spt1.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTPA id <0LSW0049CE49U6@spt1.w1.samsung.com> for linux-mm@kvack.org; Tue, 11 Oct 2011 11:50:34 +0100 (BST) Date: Tue, 11 Oct 2011 12:50:23 +0200 From: Marek Szyprowski Subject: RE: [Linaro-mm-sig] [PATCHv16 0/9] Contiguous Memory Allocator In-reply-to: <4E93F088.60006@stericsson.com> Message-id: <00b301cc8803$93b5b3e0$bb211ba0$%szyprowski@samsung.com> Content-language: pl References: <1317909290-29832-1-git-send-email-m.szyprowski@samsung.com> <4E92E003.4060901@stericsson.com> <00b001cc87e5$dc818cc0$9584a640$%szyprowski@samsung.com> <4E93F088.60006@stericsson.com> Sender: owner-linux-mm@kvack.org List-ID: To: 'Maxime Coquelin' 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 Hello, On Tuesday, October 11, 2011 9:30 AM Maxime Coquelin wrote: > 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. I'm really surprised. Could you elaborate a bit how to trigger this issue? I've did several tests and I never get a lockup. Allocation failed from time to time though. > 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 s/investing/investigating > > pages and how to add real migration support for them. > > > > Ok, thanks for pointing this out. We found this issue very recently. I'm still surprised that we did not notice it during system testing. Best regards -- Marek Szyprowski Samsung Poland R&D Center -- 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