From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f70.google.com (mail-oi0-f70.google.com [209.85.218.70]) by kanga.kvack.org (Postfix) with ESMTP id A7B006B025F for ; Tue, 16 Aug 2016 06:30:49 -0400 (EDT) Received: by mail-oi0-f70.google.com with SMTP id s207so200977951oie.1 for ; Tue, 16 Aug 2016 03:30:49 -0700 (PDT) Received: from dfwrgout.huawei.com (dfwrgout.huawei.com. [206.16.17.72]) by mx.google.com with ESMTPS id a185si3072532oib.167.2016.08.16.03.30.42 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 16 Aug 2016 03:30:49 -0700 (PDT) Message-ID: <57B2E8F8.8080408@huawei.com> Date: Tue, 16 Aug 2016 18:20:40 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [PATCH 1/3] mm: fix set pageblock migratetype in deferred struct page init References: <57A325CA.9050707@huawei.com> <57A3260F.4050709@huawei.com> <20160816084132.GA17417@dhcp22.suse.cz> <57B2D556.5030201@huawei.com> <20160816092345.GB17417@dhcp22.suse.cz> In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka , Michal Hocko Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Mel Gorman , Andrew Morton , David Rientjes , Joonsoo Kim , Taku Izumi , "'Kirill A . Shutemov'" , Kamezawa Hiroyuki , Linux MM , LKML On 2016/8/16 18:12, Vlastimil Babka wrote: > On 08/16/2016 11:23 AM, Michal Hocko wrote: >> On Tue 16-08-16 16:56:54, Xishi Qiu wrote: >>> On 2016/8/16 16:41, Michal Hocko wrote: >>> >>>> On Thu 04-08-16 19:25:03, Xishi Qiu wrote: >>>>> MAX_ORDER_NR_PAGES is usually 4M, and a pageblock is usually 2M, so we only >>>>> set one pageblock's migratetype in deferred_free_range() if pfn is aligned >>>>> to MAX_ORDER_NR_PAGES. >>>> >>>> Do I read the changelog correctly and the bug causes leaking unmovable >>>> allocations into movable zones? >>> >>> Hi Michal, >>> >>> This bug will cause uninitialized migratetype, you can see from >>> "cat /proc/pagetypeinfo", almost half blocks are Unmovable. >> >> Please add that information to the changelog. Leaking unmovable >> allocations to the movable zones defeats the whole purpose of the >> movable zone so I guess we really want to mark this for stable. > > Note that it's not as severe. Pageblock migratetype is just heuristic against fragmentation. It should not allow unmovable allocations from movable zones (although I can't find what really does govern it). > Yes, leaking unmovable migratetype to movable zone is fine for mem-offline, we will check every page in offline_pages(). But as I pointed that we missed to free the last block in deferred_init_memmap(), this will lead to mem-offline fail. Thanks, Xishi Qiu >> AFAICS it should also note: >> Fixes: ac5d2539b238 ("mm: meminit: reduce number of times pageblocks are set during struct page init") >> and stable 4.2+ > > > > > . > -- 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