Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755795Ab2KUTRO (ORCPT ); Wed, 21 Nov 2012 14:17:14 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:50983 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755734Ab2KUTRN (ORCPT ); Wed, 21 Nov 2012 14:17:13 -0500 Date: Wed, 21 Nov 2012 11:17:11 -0800 From: Andrew Morton To: Marek Szyprowski 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 Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls Message-Id: <20121121111711.fe915265.akpm@linux-foundation.org> In-Reply-To: <50AC9CC7.8010103@samsung.com> 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> <50AC9CC7.8010103@samsung.com> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2473 Lines: 56 On Wed, 21 Nov 2012 10:20:07 +0100 Marek Szyprowski wrote: > 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. > What I'm suggesting is that it be merged for 3.8-rc1 with a -stable tag, then it will be backported into 3.7.x later on. -- 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/