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Hugh Dickins 3d470fc385 mm: munlock use mapcount to avoid terrible overhead 
A process spent 30 minutes exiting, just munlocking the pages of a large
anonymous area that had been alternately mprotected into page-sized vmas:
for every single page there's an anon_vma walk through all the other
little vmas to find the right one.

A general fix to that would be a lot more complicated (use prio_tree on
anon_vma?), but there's one very simple thing we can do to speed up the
common case: if a page to be munlocked is mapped only once, then it is our
vma that it is mapped into, and there's no need whatever to walk through
all the others.

Okay, there is a very remote race in munlock_vma_pages_range(), if between
its follow_page() and lock_page(), another process were to munlock the
same page, then page reclaim remove it from our vma, then another process
mlock it again.  We would find it with page_mapcount 1, yet it's still
mlocked in another process.  But never mind, that's much less likely than
the down_read_trylock() failure which munlocking already tolerates (in
try_to_unmap_one()): in due course page reclaim will discover and move the
page to unevictable instead.

[akpm@linux-foundation.org: add comment]
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2011-10-31 17:30:51 -07:00
..
Kconfig memblock: add NO_BOOTMEM config symbol 2011-10-31 17:30:47 -07:00
Kconfig.debug mm: debug-pagealloc: fix kconfig dependency warning 2011-03-22 17:44:02 -07:00
Makefile Cross Memory Attach 2011-10-31 17:30:44 -07:00
backing-dev.c mm-add-comment-explaining-task-state-setting-in-bdi_forker_thread-fix 2011-10-31 17:30:49 -07:00
bootmem.c crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn 2011-03-23 19:47:19 -07:00
bounce.c bounce: call flush_dcache_page() after bounce_copy_vec() 2010-09-09 18:57:25 -07:00
cleancache.c mm: cleancache core ops functions and config 2011-05-26 10:01:36 -06:00
compaction.c mm: compaction: make compact_zone_order() static 2011-10-31 17:30:49 -07:00
debug-pagealloc.c debug-pagealloc: add support for highmem pages 2011-10-31 17:30:48 -07:00
dmapool.c devres: fix possible use after free 2011-07-25 20:57:14 -07:00
fadvise.c readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM 2010-03-06 11:26:25 -08:00
failslab.c fault-injection: add ability to export fault_attr in arbitrary directory 2011-08-03 14:25:20 -10:00
filemap.c vfs: iov_iter: have iov_iter_advance decrement nr_segs appropriately 2011-10-28 13:55:08 +02:00
filemap_xip.c mm: Convert i_mmap_lock to a mutex 2011-05-25 08:39:18 -07:00
fremap.c mm: don't access vm_flags as 'int' 2011-05-26 09:20:31 -07:00
highmem.c mm: fix kunmap_high() comment 2011-10-31 17:30:49 -07:00
huge_memory.c mm/huge_memory: fix typo when updating mmu cache 2011-10-31 17:30:51 -07:00
hugetlb.c mm: hugetlb: fix coding style issues 2011-07-25 20:57:09 -07:00
hwpoison-inject.c Fix common misspellings 2011-03-31 11:26:23 -03:00
init-mm.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
internal.h mm: nommu: sort mm->mmap list properly 2011-05-25 08:39:05 -07:00
kmemcheck.c kmemcheck: Fix build errors due to missing slab.h 2010-03-30 22:02:32 +09:00
kmemleak-test.c kmemleak: remove memset by using kzalloc 2011-01-27 18:31:51 +00:00
kmemleak.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
ksm.c oom: fix race while temporarily setting current's oom_score_adj 2011-10-31 17:30:45 -07:00
maccess.c maccess,probe_kernel: Make write/read src const void * 2011-05-25 19:56:23 -04:00
madvise.c fs: kill i_alloc_sem 2011-07-20 20:47:46 -04:00
memblock.c mm/memblock.c: quiet sparse noise 2011-10-31 17:30:50 -07:00
memcontrol.c mm: change isolate mode from #define to bitwise type 2011-10-31 17:30:44 -07:00
memory-failure.c HWPOISON: convert pr_debug()s to pr_info()s 2011-10-31 17:30:49 -07:00
memory.c mm/futex: fix futex writes on archs with SW tracking of dirty & young 2011-07-25 20:57:11 -07:00
memory_hotplug.c mm: extend memory hotplug API to allow memory hotplug in virtual machines 2011-07-25 20:57:08 -07:00
mempolicy.c mm/mempolicy.c: quiet sparse noise 2011-10-31 17:30:50 -07:00
mempool.c mm: remove broken 'kzalloc' mempool 2009-09-22 07:17:35 -07:00
migrate.c mm: migration: clean up unmap_and_move() 2011-10-31 17:30:45 -07:00
mincore.c mm: clarify the radix_tree exceptional cases 2011-08-03 14:25:24 -10:00
mlock.c mm: munlock use mapcount to avoid terrible overhead 2011-10-31 17:30:51 -07:00
mm_init.c mm: mminit_loglevel cannot be __meminitdata anymore 2008-08-20 15:40:30 -07:00
mmap.c mm/mmap.c: eliminate the ret variable from mm_take_all_locks() 2011-10-31 17:30:49 -07:00
mmu_context.c exit: fix oops in sync_mm_rss 2010-03-24 16:31:21 -07:00
mmu_notifier.c thp: mmu_notifier_test_young 2011-01-13 17:32:46 -08:00
mmzone.c mm: page allocator: adjust the per-cpu counter threshold when memory is low 2011-01-13 17:32:31 -08:00
mprotect.c thp: mprotect: transparent huge page support 2011-01-13 17:32:44 -08:00
mremap.c thp: mremap support and TLB optimization 2011-10-31 17:30:48 -07:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nobootmem.c memblock/nobootmem: remove unneeded code from alloc_bootmem_node_high() 2011-05-25 08:39:31 -07:00
nommu.c mmap: fix and tidy up overcommit page arithmetic 2011-07-25 20:57:09 -07:00
oom_kill.c oom: fix race while temporarily setting current's oom_score_adj 2011-10-31 17:30:45 -07:00
page-writeback.c mm/page-writeback.c: document bdi_min_ratio 2011-10-31 17:30:45 -07:00
page_alloc.c mm: neaten warn_alloc_failed 2011-10-31 17:30:48 -07:00
page_cgroup.c mm: Convert vmalloc/memset to vzalloc 2011-09-15 13:56:56 +02:00
page_io.c block: kill off REQ_UNPLUG 2011-03-10 08:52:27 +01:00
page_isolation.c mm: page_isolation: codeclean fix comment and rm unneeded val init 2010-10-26 16:52:11 -07:00
pagewalk.c pagewalk: fix code comment for THP 2011-07-25 20:57:09 -07:00
percpu-km.c percpu: clear memory allocated with the km allocator 2010-10-02 10:28:42 +03:00
percpu-vm.c mm: remove gfp mask from pcpu_get_vm_areas 2011-01-13 17:32:34 -08:00
percpu.c Merge branch 'for-2.6.40' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2011-05-24 11:53:42 -07:00
pgtable-generic.c mm/pgtable-generic.c: fix CONFIG_SWAP=n build 2011-01-26 10:49:58 +10:00
prio_tree.c sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00
process_vm_access.c Cross Memory Attach 2011-10-31 17:30:44 -07:00
quicklist.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
readahead.c readahead: readahead page allocations are OK to fail 2011-05-25 08:39:25 -07:00
rmap.c ksm: fix the comment of try_to_unmap_one() 2011-10-31 17:30:49 -07:00
shmem.c vmscan: add barrier to prevent evictable page in unevictable list 2011-10-31 17:30:50 -07:00
slab.c mm: restrict access to slab files under procfs and sysfs 2011-09-27 22:59:27 +03:00
slob.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
slub.c lib/string.c: introduce memchr_inv() 2011-10-31 17:30:47 -07:00
sparse-vmemmap.c tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
sparse.c mm: make some struct page's const 2011-07-25 20:57:07 -07:00
swap.c mm: batch activate_page() to reduce lock contention 2011-05-25 08:39:37 -07:00
swap_state.c block: remove per-queue plugging 2011-03-10 08:52:07 +01:00
swapfile.c oom: fix race while temporarily setting current's oom_score_adj 2011-10-31 17:30:45 -07:00
thrash.c mm/thrash.c: quiet sparse noise 2011-10-31 17:30:50 -07:00
truncate.c mm: a few small updates for radix-swap 2011-08-03 14:25:24 -10:00
util.c mm: nommu: sort mm->mmap list properly 2011-05-25 08:39:05 -07:00
vmalloc.c mm/vmalloc.c: report more vmalloc failures 2011-10-31 17:30:48 -07:00
vmscan.c vmscan: abort reclaim/compaction if compaction can proceed 2011-10-31 17:30:50 -07:00
vmstat.c mm: vmscan: immediately reclaim end-of-LRU dirty pages when writeback completes 2011-10-31 17:30:47 -07:00