Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754477AbaGDHwr (ORCPT ); Fri, 4 Jul 2014 03:52:47 -0400 Received: from lgeamrelo01.lge.com ([156.147.1.125]:43013 "EHLO lgeamrelo01.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752329AbaGDHwp (ORCPT ); Fri, 4 Jul 2014 03:52:45 -0400 X-Original-SENDERIP: 10.177.220.145 X-Original-MAILFROM: iamjoonsoo.kim@lge.com From: Joonsoo Kim To: Andrew Morton Cc: "Kirill A. Shutemov" , Rik van Riel , Peter Zijlstra , Mel Gorman , Johannes Weiner , Minchan Kim , Yasuaki Ishimatsu , Zhang Yanfei , "Srivatsa S. Bhat" , 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 , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim Subject: [PATCH 00/10] fix freepage count problems due to memory isolation Date: Fri, 4 Jul 2014 16:57:45 +0900 Message-Id: <1404460675-24456-1-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, This patchset aims at fixing problems due to memory isolation found by testing my patchset [1]. These are really subtle problems so I can be wrong. If you find what I am missing, please let me know. 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. 4. pages for guard are *not* counted as freepage. Now, I describe problems and related patch. 1. Patch 2: If guard page are cleared and merged into isolate buddy list, we should not add freepage count. 2. Patch 3: When the page return back from pcp to buddy, we should account it to freepage counter. In this case, we should check the pageblock migratetype of the page and should insert the page into appropriate buddy list. Although we checked it in current code, we didn't insert the page into appropriate buddy list so that freepage counting can be wrong. 3. Patch 4: There is race condition so that some freepages could be on isolate buddy list. If so, we can't use this page until next isolation attempt on this pageblock. 4. Patch 5: There is race condition that page on isolate pageblock can go into non-isolate buddy list. If so, buddy allocator would merge pages on non-isolate buddy list and isolate buddy list, respectively, and freepage count will be wrong. 5. Patch 9: move_freepages(_block) returns *not* number of moved pages. Instead, it returns number of pages linked in that migratetype buddy list. So accouting with this return value makes freepage count wrong. 6. Patch 10: buddy allocator would merge pages on non-isolate buddy list and isolate buddy list, respectively. This leads to freepage counting problem so fix it by stopping merging in this case. Without patchset [1], 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 [1], 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 [1] and this patchset, I found that no freepage count are missed so that I conclude that problems are solved. These problems can be possible on memory hot remove users, although I didn't check it further. Other patches are either for the base to fix these problems or for simple clean-up. Please see individual patches for more information. This patchset is based on linux-next-20140703. Thanks. [1]: Aggressively allocate the pages on cma reserved memory https://lkml.org/lkml/2014/5/30/291 Joonsoo Kim (10): mm/page_alloc: remove unlikely macro on free_one_page() mm/page_alloc: correct to clear guard attribute in DEBUG_PAGEALLOC mm/page_alloc: handle page on pcp correctly if it's pageblock is isolated mm/page_alloc: carefully free the page on isolate pageblock mm/page_alloc: optimize and unify pageblock migratetype check in free path mm/page_alloc: separate freepage migratetype interface mm/page_alloc: store migratetype of the buddy list into freepage correctly mm/page_alloc: use get_onbuddy_migratetype() to get buddy list type mm/page_alloc: fix possible wrongly calculated freepage counter mm/page_alloc: Stop merging pages on non-isolate and isolate buddy list include/linux/mm.h | 30 +++++++-- include/linux/mmzone.h | 5 ++ include/linux/page-isolation.h | 8 +++ mm/page_alloc.c | 138 +++++++++++++++++++++++++++++----------- mm/page_isolation.c | 18 ++---- 5 files changed, 147 insertions(+), 52 deletions(-) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/