From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f176.google.com (mail-ig0-f176.google.com [209.85.213.176]) by kanga.kvack.org (Postfix) with ESMTP id 2B6176B0005 for ; Thu, 17 Mar 2016 02:53:16 -0400 (EDT) Received: by mail-ig0-f176.google.com with SMTP id av4so7893120igc.1 for ; Wed, 16 Mar 2016 23:53:16 -0700 (PDT) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id k96si8852497ioi.161.2016.03.16.23.53.13 for ; Wed, 16 Mar 2016 23:53:15 -0700 (PDT) Date: Thu, 17 Mar 2016 15:54:26 +0900 From: Joonsoo Kim Subject: Re: Suspicious error for CMA stress test Message-ID: <20160317065426.GA10315@js1304-P5Q-DELUXE> References: <56DD38E7.3050107@huawei.com> <56DDCB86.4030709@redhat.com> <56DE30CB.7020207@huawei.com> <56DF7B28.9060108@huawei.com> <56E2FB5C.1040602@suse.cz> <20160314064925.GA27587@js1304-P5Q-DELUXE> <56E662E8.700@suse.cz> <20160314071803.GA28094@js1304-P5Q-DELUXE> <56E92AFC.9050208@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56E92AFC.9050208@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Hanjun Guo Cc: Vlastimil Babka , "Leizhen (ThunderTown)" , Laura Abbott , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Andrew Morton , Sasha Levin , Laura Abbott , qiuxishi , Catalin Marinas , Will Deacon , Arnd Bergmann , dingtinahong , chenjie6@huawei.com, "linux-mm@kvack.org" On Wed, Mar 16, 2016 at 05:44:28PM +0800, Hanjun Guo wrote: > On 2016/3/14 15:18, Joonsoo Kim wrote: > > On Mon, Mar 14, 2016 at 08:06:16AM +0100, Vlastimil Babka wrote: > >> On 03/14/2016 07:49 AM, Joonsoo Kim wrote: > >>> On Fri, Mar 11, 2016 at 06:07:40PM +0100, Vlastimil Babka wrote: > >>>> On 03/11/2016 04:00 PM, Joonsoo Kim wrote: > >>>> > >>>> How about something like this? Just and idea, probably buggy (off-by-one etc.). > >>>> Should keep away cost from >>>> relatively fewer >pageblock_order iterations. > >>> Hmm... I tested this and found that it's code size is a little bit > >>> larger than mine. I'm not sure why this happens exactly but I guess it would be > >>> related to compiler optimization. In this case, I'm in favor of my > >>> implementation because it looks like well abstraction. It adds one > >>> unlikely branch to the merge loop but compiler would optimize it to > >>> check it once. > >> I would be surprised if compiler optimized that to check it once, as > >> order increases with each loop iteration. But maybe it's smart > >> enough to do something like I did by hand? Guess I'll check the > >> disassembly. > > Okay. I used following slightly optimized version and I need to > > add 'max_order = min_t(unsigned int, MAX_ORDER, pageblock_order + 1)' > > to yours. Please consider it, too. > > Hmm, this one is not work, I still can see the bug is there after applying > this patch, did I miss something? I may find that there is a bug which was introduced by me some time ago. Could you test following change in __free_one_page() on top of Vlastimil's patch? -page_idx = pfn & ((1 << max_order) - 1); +page_idx = pfn & ((1 << MAX_ORDER) - 1); Thanks. -- 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