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Date: Wed, 16 Mar 2016 17:44:28 +0800 From: Hanjun Guo <guohanjun@...wei.com> To: Joonsoo Kim <iamjoonsoo.kim@....com>, Vlastimil Babka <vbabka@...e.cz> CC: "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>, Laura Abbott <labbott@...hat.com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, Sasha Levin <sasha.levin@...cle.com>, Laura Abbott <lauraa@...eaurora.org>, qiuxishi <qiuxishi@...wei.com>, Catalin Marinas <Catalin.Marinas@....com>, Will Deacon <will.deacon@....com>, Arnd Bergmann <arnd@...db.de>, dingtinahong <dingtianhong@...wei.com>, <chenjie6@...wei.com>, "linux-mm@...ck.org" <linux-mm@...ck.org> Subject: Re: Suspicious error for CMA stress test 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 <pageblock_order iterations at the expense of the >>>> 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? Thanks Hanjun
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