From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Nazarewicz Date: Tue, 28 Oct 2014 16:57:45 +0000 Subject: Re: CMA: test_pages_isolated failures in alloc_contig_range Message-Id: List-Id: References: <2457604.k03RC2Mv4q@avalon> <544F9EAA.5010404@hurleysoftware.com> In-Reply-To: <544F9EAA.5010404@hurleysoftware.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Peter Hurley , Laurent Pinchart , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org, Bartlomiej Zolnierkiewicz , Minchan Kim , Andrew Morton > On 10/28/2014 08:38 AM, Michal Nazarewicz wrote: >> 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. On Tue, Oct 28 2014, Peter Hurley wrote: > 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. I think it could be argued both ways. The condition is not an error, since in many cases cma_alloc will be able to continue, but it *is* an undesired state. As such it's not an error but feels to me a bit more then just information, hence a warning. I don't care either way, though. -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +------ooO--(_)--Ooo--