Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753380AbaJ1Nsc (ORCPT ); Tue, 28 Oct 2014 09:48:32 -0400 Received: from mailout32.mail01.mtsvc.net ([216.70.64.70]:36700 "EHLO n23.mail01.mtsvc.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752404AbaJ1Nsb (ORCPT ); Tue, 28 Oct 2014 09:48:31 -0400 Message-ID: <544F9EAA.5010404@hurleysoftware.com> Date: Tue, 28 Oct 2014 09:48:26 -0400 From: Peter Hurley User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Michal Nazarewicz , Laurent Pinchart , linux-mm@kvack.org CC: linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, Bartlomiej Zolnierkiewicz , Minchan Kim , Andrew Morton Subject: Re: CMA: test_pages_isolated failures in alloc_contig_range References: <2457604.k03RC2Mv4q@avalon> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Authenticated-User: 990527 peter@hurleysoftware.com X-MT-ID: 8FA290C2A27252AACF65DBC4A42F3CE3735FB2A4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ +cc Andrew Morton ] On 10/28/2014 08:38 AM, Michal Nazarewicz wrote: > On Sun, Oct 26 2014, Laurent Pinchart wrote: >> Hello, >> >> I've run into a CMA-related issue while testing a DMA engine driver with >> dmatest on a Renesas R-Car ARM platform. >> >> When allocating contiguous memory through CMA the kernel prints the following >> messages to the kernel log. >> >> [ 99.770000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed >> [ 124.220000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed >> [ 127.550000] alloc_contig_range test_pages_isolated(6b845, 6b846) failed >> [ 132.850000] alloc_contig_range test_pages_isolated(6b845, 6b846) failed >> [ 151.390000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed >> [ 166.490000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed >> [ 181.450000] alloc_contig_range test_pages_isolated(6b845, 6b846) failed >> >> I've stripped the dmatest module down as much as possible to remove any >> hardware dependencies and came up with the following implementation. > > Like Laura wrote, the message is not (should not be) a problem in > itself: [...] > So as you can see cma_alloc will try another part of the cma region if > test_pages_isolated fails. > > Obviously, if CMA region is fragmented or there's enough space for only > one allocation of required size isolation failures will cause allocation > failures, so it's best to avoid them, but they are not always avoidable. > > To debug you would probably want to add more debug information about the > page (i.e. data from struct page) that failed isolation after the > pr_warn in alloc_contig_range. If the message does not indicate an actual problem, then its printk level is too high. These messages have been reported when using 3.16+ distro kernels. Regards, Peter Hurley -- 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/