Hi Vlastimil, FYI, this bug seems still not fixed in linux-next 20130925. commit 7a8010cd36273ff5f6fea5201ef9232f30cebbd9 Author: Vlastimil Babka Date: Wed Sep 11 14:22:35 2013 -0700 mm: munlock: manual pte walk in fast path instead of follow_page_mask() Currently munlock_vma_pages_range() calls follow_page_mask() to obtain each individual struct page. This entails repeated full page table translations and page table lock taken for each page separately. This patch avoids the costly follow_page_mask() where possible, by iterating over ptes within single pmd under single page table lock. The first pte is obtained by get_locked_pte() for non-THP page acquired by the initial follow_page_mask(). The rest of the on-stack pagevec for munlock is filled up using pte_walk as long as pte_present() and vm_normal_page() are sufficient to obtain the struct page. After this patch, a 14% speedup was measured for munlocking a 56GB large memory area with THP disabled. Signed-off-by: Vlastimil Babka Cc: JA?rn Engel Cc: Mel Gorman Cc: Michel Lespinasse Cc: Hugh Dickins Cc: Rik van Riel Cc: Johannes Weiner Cc: Michal Hocko Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [ 89.835504] init: plymouth-upstart-bridge main process (3556) terminated with status 1 [ 89.986606] init: tty6 main process (3529) killed by TERM signal [ 91.414086] BUG: Bad page map in process killall5 pte:cf17e720 pmd:05a22067 [ 91.416626] addr:bfc00000 vm_flags:00100173 anon_vma:cf128c80 mapping: (null) index:bfff0 [ 91.419402] CPU: 0 PID: 3574 Comm: killall5 Not tainted 3.12.0-rc1-00010-g5fbc0a6 #24 [ 91.422171] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 91.423998] 00000000 00000000 c0199e34 c1db5db4 00000000 c0199e54 c10e72d4 000bfff0 [ 91.427933] 00000000 bfc00000 00000000 000cf17e cf17e720 c0199e74 c10e7995 00000000 [ 91.431940] bfc00000 cf1ca190 bfc00000 cf180000 cf1ca190 c0199ee0 c10eb8cf ce6d1900 [ 91.435894] Call Trace: [ 91.436969] [] dump_stack+0x4b/0x66 [ 91.438503] [] print_bad_pte+0x14b/0x162 [ 91.440204] [] vm_normal_page+0x67/0x9b [ 91.441811] [] munlock_vma_pages_range+0xf9/0x176 [ 91.443633] [] exit_mmap+0x86/0xf7 [ 91.445156] [] ? lock_release+0x169/0x1ef [ 91.446795] [] ? rcu_read_unlock+0x17/0x23 [ 91.448465] [] ? exit_aio+0x2b/0x6c [ 91.449990] [] mmput+0x6a/0xcb [ 91.451508] [] do_exit+0x362/0x8be [ 91.453013] [] ? hrtimer_debug_hint+0xd/0xd [ 91.454700] [] do_group_exit+0x51/0x9e [ 91.456296] [] SyS_exit_group+0x16/0x16 [ 91.457901] [] sysenter_do_call+0x12/0x33 [ 91.459553] Disabling lock debugging due to kernel taint git bisect start 272b98c6455f00884f0350f775c5342358ebb73f v3.11 -- git bisect good 57d730924d5cc2c3e280af16a9306587c3a511db # 02:21 495+ Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip git bisect good 3bb22ec53e2bd12a241ed84359bffd591a40ab87 # 12:03 495+ staging/lustre/ptlrpc: convert to new shrinker API git bisect bad a5b7c87f92076352dbff2fe0423ec255e1c9a71b # 12:18 31- vmscan, memcg: do softlimit reclaim also for targeted reclaim git bisect good 3d94ea51c1d8db6f41268a9d2aea5f5771e9a8d3 # 15:40 495+ ocfs2: clean up dead code in ocfs2_acl_from_xattr() git bisect bad d62a201f24cba74e2fbf9f6f7af86ff5f5e276fc # 16:46 79- checkpatch: enforce sane perl version git bisect good 83467efbdb7948146581a56cbd683a22a0684bbb # 01:29 585+ mm: migrate: check movability of hugepage in unmap_and_move_huge_page() git bisect bad 2bff24a3707093c435ab3241c47dcdb5f16e432b # 02:07 148- memcg: fix multiple large threshold notifications git bisect bad 1ecfd533f4c528b0b4cc5bc115c4c47f0b5e4828 # 02:34 64- mm/mremap.c: call pud_free() after fail calling pmd_alloc() git bisect good 0ec3b74c7f5599c8a4d2b33d430a5470af26ebf6 # 13:10 1170+ mm: putback_lru_page: remove unnecessary call to page_lru_base_type() git bisect good 5b40998ae35cf64561868370e6c9f3d3e94b6bf7 # 16:52 1170+ mm: munlock: remove redundant get_page/put_page pair on the fast path git bisect bad 187320932dcece9c4b93f38f56d1f888bd5c325f # 17:11 0- mm/sparse: introduce alloc_usemap_and_memmap git bisect bad 6e543d5780e36ff5ee56c44d7e2e30db3457a7ed # 17:29 2- mm: vmscan: fix do_try_to_free_pages() livelock git bisect bad 7a8010cd36273ff5f6fea5201ef9232f30cebbd9 # 17:59 14- mm: munlock: manual pte walk in fast path instead of follow_page_mask() git bisect good 5b40998ae35cf64561868370e6c9f3d3e94b6bf7 # 22:10 3510+ mm: munlock: remove redundant get_page/put_page pair on the fast path git bisect bad 5fbc0a6263a147cde905affbfb6622c26684344f # 22:10 0- Merge remote-tracking branch 'pinctrl/for-next' into kbuild_tmp git bisect good 87e37036dcf96eb73a8627524be8b722bd1ac526 # 04:31 3510+ Revert "mm: munlock: manual pte walk in fast path instead of follow_page_mask()" git bisect bad 22356f447ceb8d97a4885792e7d9e4607f712e1b # 04:40 48- mm: Place preemption point in do_mlockall() loop git bisect bad 050f4da86e9bdbcc9e11789e0f291aafa57b8a20 # 04:55 133- Add linux-next specific files for 20130925 Thanks, Fengguang