From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx183.postini.com [74.125.245.183]) by kanga.kvack.org (Postfix) with SMTP id A1F4A6B002B for ; Wed, 21 Nov 2012 04:20:14 -0500 (EST) Received: from eusync4.samsung.com (mailout3.w1.samsung.com [210.118.77.13]) by mailout3.w1.samsung.com (Oracle Communications Messaging Server 7u4-24.01(7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTP id <0MDT00FO4ZADAX80@mailout3.w1.samsung.com> for linux-mm@kvack.org; Wed, 21 Nov 2012 09:20:37 +0000 (GMT) Received: from [127.0.0.1] ([106.116.147.30]) by eusync4.samsung.com (Oracle Communications Messaging Server 7u4-24.01 (7.0.4.24.0) 64bit (built Nov 17 2011)) with ESMTPA id <0MDT002XGZ9KX920@eusync4.samsung.com> for linux-mm@kvack.org; Wed, 21 Nov 2012 09:20:12 +0000 (GMT) Message-id: <50AC9CC7.8010103@samsung.com> Date: Wed, 21 Nov 2012 10:20:07 +0100 From: Marek Szyprowski MIME-version: 1.0 Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls References: <20121119144826.f59667b2.akpm@linux-foundation.org> <1353421905-3112-1-git-send-email-m.szyprowski@samsung.com> <20121120113325.dde266ed.akpm@linux-foundation.org> <50AC8C14.5050204@samsung.com> <20121121003643.97febbdb.akpm@linux-foundation.org> In-reply-to: <20121121003643.97febbdb.akpm@linux-foundation.org> Content-type: text/plain; charset=UTF-8; format=flowed Content-transfer-encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-arm-kernel@lists.infradead.org, linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kyungmin Park , Arnd Bergmann , Soren Moch , Thomas Petazzoni , Sebastian Hesselbarth , Andrew Lunn , Jason Cooper , KAMEZAWA Hiroyuki , Michal Hocko , Mel Gorman Hello, On 11/21/2012 9:36 AM, Andrew Morton wrote: > On Wed, 21 Nov 2012 09:08:52 +0100 Marek Szyprowski wrote: > > > Hello, > > > > On 11/20/2012 8:33 PM, Andrew Morton wrote: > > > On Tue, 20 Nov 2012 15:31:45 +0100 > > > Marek Szyprowski wrote: > > > > > > > dmapool always calls dma_alloc_coherent() with GFP_ATOMIC flag, > > > > regardless the flags provided by the caller. This causes excessive > > > > pruning of emergency memory pools without any good reason. Additionaly, > > > > on ARM architecture any driver which is using dmapools will sooner or > > > > later trigger the following error: > > > > "ERROR: 256 KiB atomic DMA coherent pool is too small! > > > > Please increase it with coherent_pool= kernel parameter!". > > > > Increasing the coherent pool size usually doesn't help much and only > > > > delays such error, because all GFP_ATOMIC DMA allocations are always > > > > served from the special, very limited memory pool. > > > > > > > > > > Is this problem serious enough to justify merging the patch into 3.7? > > > And into -stable kernels? > > > > I wonder if it is a good idea to merge such change at the end of current > > -rc period. > > I'm not sure what you mean by this. > > But what we do sometimes if we think a patch needs a bit more > real-world testing before backporting is to merge it into -rc1 in the > normal merge window, and tag it for -stable backporting. That way it > gets a few weeks(?) testing in mainline before getting backported. I just wondered that if it gets merged to v3.7-rc7 there won't be much time for real-world testing before final v3.7 release. This patch is in linux-next for over a week and I'm not aware of any issues, but -rc releases gets much more attention and testing than linux-next tree. If You think it's fine to put such change to v3.7-rc7 I will send a pull request and tag it for stable asap. 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/ . Don't email: email@kvack.org