From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx153.postini.com [74.125.245.153]) by kanga.kvack.org (Postfix) with SMTP id 2BB676B0078 for ; Wed, 21 Nov 2012 03:36:50 -0500 (EST) Date: Wed, 21 Nov 2012 00:36:43 -0800 From: Andrew Morton Subject: Re: [PATCH v2] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls Message-Id: <20121121003643.97febbdb.akpm@linux-foundation.org> In-Reply-To: <50AC8C14.5050204@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> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 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. -- 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