From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f179.google.com (mail-pf0-f179.google.com [209.85.192.179]) by kanga.kvack.org (Postfix) with ESMTP id 0C0EA6B0005 for ; Mon, 14 Mar 2016 03:17:02 -0400 (EDT) Received: by mail-pf0-f179.google.com with SMTP id n5so91972802pfn.2 for ; Mon, 14 Mar 2016 00:17:02 -0700 (PDT) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id v11si1930803par.167.2016.03.14.00.17.00 for ; Mon, 14 Mar 2016 00:17:01 -0700 (PDT) Date: Mon, 14 Mar 2016 16:18:03 +0900 From: Joonsoo Kim Subject: Re: Suspicious error for CMA stress test Message-ID: <20160314071803.GA28094@js1304-P5Q-DELUXE> References: <56D93ABE.9070406@huawei.com> <20160307043442.GB24602@js1304-P5Q-DELUXE> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56E662E8.700@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: "Leizhen (ThunderTown)" , Laura Abbott , Hanjun Guo , "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 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. Thanks. ------------------------>8------------------------