Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754393AbaJ1S7y (ORCPT ); Tue, 28 Oct 2014 14:59:54 -0400 Received: from galahad.ideasonboard.com ([185.26.127.97]:48870 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752373AbaJ1S7x (ORCPT ); Tue, 28 Oct 2014 14:59:53 -0400 From: Laurent Pinchart To: Peter Hurley Cc: Michal Nazarewicz , linux-mm@kvack.org, 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 Date: Tue, 28 Oct 2014 20:59:58 +0200 Message-ID: <1703418.04z9xDaRPF@avalon> User-Agent: KMail/4.12.5 (Linux/3.16.5-gentoo; KDE/4.12.5; x86_64; ; ) In-Reply-To: <544F9EAA.5010404@hurleysoftware.com> References: <2457604.k03RC2Mv4q@avalon> <544F9EAA.5010404@hurleysoftware.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Tuesday 28 October 2014 09:48:26 Peter Hurley wrote: > [ +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. [ 94.730000] __test_page_isolated_in_pageblock: failed at pfn 6b845: buddy 0 count 0 migratetype 4 poison 0 [ 94.740000] alloc_contig_range test_pages_isolated(6b845, 6b846) failed (-16) [ 202.140000] __test_page_isolated_in_pageblock: failed at pfn 6b843: buddy 0 count 0 migratetype 4 poison 0 [ 202.150000] alloc_contig_range test_pages_isolated(6b843, 6b844) failed (-16) (4 is MIGRATE_CMA) > 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. The messages got me worried, and if there's nothing to worry about, that's bad :-) -- Regards, Laurent Pinchart -- 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/