From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f170.google.com (mail-pd0-f170.google.com [209.85.192.170]) by kanga.kvack.org (Postfix) with ESMTP id 455876B006C for ; Thu, 23 Oct 2014 04:09:24 -0400 (EDT) Received: by mail-pd0-f170.google.com with SMTP id z10so606756pdj.29 for ; Thu, 23 Oct 2014 01:09:23 -0700 (PDT) Received: from lgeamrelo02.lge.com (lgeamrelo02.lge.com. [156.147.1.126]) by mx.google.com with ESMTP id rs11si915434pab.201.2014.10.23.01.09.21 for ; Thu, 23 Oct 2014 01:09:23 -0700 (PDT) From: Joonsoo Kim Subject: [PATCH v4 0/4] fix freepage count problems in memory isolation Date: Thu, 23 Oct 2014 17:10:17 +0900 Message-Id: <1414051821-12769-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , Tang Chen , Naoya Horiguchi , Bartlomiej Zolnierkiewicz , Wen Congyang , Marek Szyprowski , Michal Nazarewicz , Laura Abbott , Heesub Shin , "Aneesh Kumar K.V" , Ritesh Harjani , t.stanislaws@samsung.com, Gioh Kim , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Changes from v3 to v4 * Patch 1: Add code comment on nr_isolate_pageblock on struct zone (Naoya) Add one more check in free_one_page() that checks whether migratetype is MIGRATE_ISOLATE or not. * Patch 4: Use min() to prevent overflow of buddy merge order (Naoya) * Remove RFC tag * Add stable tag on all patches Changes from v1, v2 to v3 * A lot of comments that lead this patchset to right direction (Vlastimil and Minchan) This is version 4 patchset which is improved and minimized version of version 1 to fix freepage accounting problem during memory isolation. I tried different approach in version 2, but, it looks really complicated so I change my mind to improve version 1. You can see version 1, 2 in following links [1] [2], respectively. IMO, this v3 is better than v2, because this is simpler than v2 so better for maintainance and this doesn't change pageblock isolation logic so it is much easier to backport. This problems are found by testing my patchset [3]. There are some race conditions on pageblock isolation and these race cause incorrect freepage count. Before describing bugs itself, I first explain definition of freepage. 1. pages on buddy list are counted as freepage. 2. pages on isolate migratetype buddy list are *not* counted as freepage. 3. pages on cma buddy list are counted as CMA freepage, too. Now, I describe problems and related patch. Patch 1: There is race conditions on getting pageblock migratetype that it results in misplacement of freepages on buddy list, incorrect freepage count and un-availability of freepage. Patch 2: Freepages on pcp list could have stale cached information to determine migratetype of buddy list to go. This causes misplacement of freepages on buddy list and incorrect freepage count. Patch 4: Merging between freepages on different migratetype of pageblocks will cause freepages accouting problem. This patch fixes it. Without patchset [3], above problem doesn't happens on my CMA allocation test, because CMA reserved pages aren't used at all. So there is no chance for above race. With patchset [3], I did simple CMA allocation test and get below result. - Virtual machine, 4 cpus, 1024 MB memory, 256 MB CMA reservation - run kernel build (make -j16) on background - 30 times CMA allocation(8MB * 30 = 240MB) attempts in 5 sec interval - Result: more than 5000 freepage count are missed With patchset [3] and this patchset, I found that no freepage count are missed so that I conclude that problems are solved. On my simple memory offlining test, these problems also occur on that environment. This patchset is based on v3.18-rc1. Please see individual patches for more information. Thanks. [1]: https://lkml.org/lkml/2014/7/4/79 [2]: lkml.org/lkml/2014/8/6/52 [3]: Aggressively allocate the pages on cma reserved memory https://lkml.org/lkml/2014/5/30/291 Joonsoo Kim (4): mm/page_alloc: fix incorrect isolation behavior by rechecking migratetype mm/page_alloc: add freepage on isolate pageblock to correct buddy list mm/page_alloc: move migratetype recheck logic to __free_one_page() mm/page_alloc: restrict max order of merging on isolated pageblock include/linux/mmzone.h | 9 +++++++++ include/linux/page-isolation.h | 8 ++++++++ mm/page_alloc.c | 29 ++++++++++++++++++++--------- mm/page_isolation.c | 2 ++ 4 files changed, 39 insertions(+), 9 deletions(-) -- 1.7.9.5 -- 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