From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id B26A16B002C for ; Tue, 11 Oct 2011 03:17:54 -0400 (EDT) Received: from euspt1 (mailout2.w1.samsung.com [210.118.77.12]) by mailout2.w1.samsung.com (iPlanet Messaging Server 5.2 Patch 2 (built Jul 14 2004)) with ESMTP id <0LSW00MFU49RG9@mailout2.w1.samsung.com> for linux-mm@kvack.org; Tue, 11 Oct 2011 08:17:51 +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 <0LSW0018L49QKH@spt1.w1.samsung.com> for linux-mm@kvack.org; Tue, 11 Oct 2011 08:17:51 +0100 (BST) Date: Tue, 11 Oct 2011 09:17:40 +0200 From: Marek Szyprowski Subject: RE: [Linaro-mm-sig] [PATCHv16 0/9] Contiguous Memory Allocator In-reply-to: <4E92E003.4060901@stericsson.com> Message-id: <00b001cc87e5$dc818cc0$9584a640$%szyprowski@samsung.com> MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-language: pl Content-transfer-encoding: 7BIT References: <1317909290-29832-1-git-send-email-m.szyprowski@samsung.com> <4E92E003.4060901@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, 'frq09524' , vincent.guittot@linaro.org Hello, On Monday, October 10, 2011 2:08 PM Maxime Coquelin wrote: > On 10/06/2011 03:54 PM, Marek Szyprowski wrote: > > Welcome everyone again, > > > > Once again I decided to post an updated version of the Contiguous Memory > > Allocator patches. > > > > This version provides mainly a bugfix for a very rare issue that might > > have changed migration type of the CMA page blocks resulting in dropping > > CMA features from the affected page block and causing memory allocation > > to fail. Also the issue reported by Dave Hansen has been fixed. > > > > This version also introduces basic support for x86 architecture, what > > allows wide testing on KVM/QEMU emulators and all common x86 boxes. I > > hope this will result in wider testing, comments and easier merging to > > mainline. > > > > I've also dropped an examplary patch for s5p-fimc platform device > > private memory declaration and added the one from real life. CMA device > > private memory regions are defined for s5p-mfc device to let it allocate > > buffers from two memory banks. > > > > ARM integration code has not been changed since last version, it > > provides implementation of all the ideas that has been discussed during > > Hello Marek, > > We are currently testing CMA (v16) on Snowball platform. > This feature is very promising, thanks for pushing it! > > 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. > > 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. > For now, we didn't had time to investigate further theses problems. > Have you already faced this kind of issues? > Could someone testing CMA on other boards confirm/infirm theses > problems? 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