linux/mm
Mel Gorman e58469bafd mm: page_alloc: use word-based accesses for get/set pageblock bitmaps
The test_bit operations in get/set pageblock flags are expensive.  This
patch reads the bitmap on a word basis and use shifts and masks to isolate
the bits of interest.  Similarly masks are used to set a local copy of the
bitmap and then use cmpxchg to update the bitmap if there have been no
other changes made in parallel.

In a test running dd onto tmpfs the overhead of the pageblock-related
functions went from 1.27% in profiles to 0.5%.

In addition to the performance benefits, this patch closes races that are
possible between:

a) get_ and set_pageblock_migratetype(), where get_pageblock_migratetype()
   reads part of the bits before and other part of the bits after
   set_pageblock_migratetype() has updated them.

b) set_pageblock_migratetype() and set_pageblock_skip(), where the non-atomic
   read-modify-update set bit operation in set_pageblock_skip() will cause
   lost updates to some bits changed in the set_pageblock_migratetype().

Joonsoo Kim first reported the case a) via code inspection.  Vlastimil
Babka's testing with a debug patch showed that either a) or b) occurs
roughly once per mmtests' stress-highalloc benchmark (although not
necessarily in the same pageblock).  Furthermore during development of
unrelated compaction patches, it was observed that frequent calls to
{start,undo}_isolate_page_range() the race occurs several thousands of
times and has resulted in NULL pointer dereferences in move_freepages()
and free_one_page() in places where free_list[migratetype] is
manipulated by e.g.  list_move().  Further debugging confirmed that
migratetype had invalid value of 6, causing out of bounds access to the
free_list array.

That confirmed that the race exist, although it may be extremely rare,
and currently only fatal where page isolation is performed due to
memory hot remove.  Races on pageblocks being updated by
set_pageblock_migratetype(), where both old and new migratetype are
lower MIGRATE_RESERVE, currently cannot result in an invalid value
being observed, although theoretically they may still lead to
unexpected creation or destruction of MIGRATE_RESERVE pageblocks.
Furthermore, things could get suddenly worse when memory isolation is
used more, or when new migratetypes are added.

After this patch, the race has no longer been observed in testing.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-04 16:54:09 -07:00
..
backing-dev.c arch: Mass conversion of smp_mb__*() 2014-04-18 14:20:48 +02:00
balloon_compaction.c mm: print more details for bad_page() 2014-01-23 16:36:50 -08:00
bootmem.c mm/bootmem.c: remove unused local `map' 2013-11-13 12:09:09 +09:00
cleancache.c mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE 2014-01-23 16:36:50 -08:00
compaction.c mm/compaction: avoid rescanning pageblocks in isolate_freepages 2014-06-04 16:54:07 -07:00
debug-pagealloc.c
dmapool.c mm/dmapool.c: reuse devres_release() to free resources 2014-06-04 16:54:08 -07:00
early_ioremap.c mm: create generic early_ioremap() support 2014-04-07 16:36:15 -07:00
fadvise.c teach SYSCALL_DEFINE<n> how to deal with long long/unsigned long long 2013-03-03 22:46:22 -05:00
failslab.c
filemap_xip.c seqcount: Add lockdep functionality to seqcount/seqlock structures 2013-11-06 12:40:26 +01:00
filemap.c fs/mpage.c: factor page_endio() out of mpage_end_io() 2014-06-04 16:54:02 -07:00
fremap.c mm: softdirty: make freshly remapped file pages being softdirty unconditionally 2014-06-04 16:53:56 -07:00
frontswap.c swap: change swap_list_head to plist, add swap_avail_head 2014-06-04 16:54:07 -07:00
gup.c mm: cleanup __get_user_pages() 2014-06-04 16:54:05 -07:00
highmem.c
huge_memory.c mm/huge_memory.c: complete conversion to pr_foo() 2014-06-04 16:53:58 -07:00
hugetlb_cgroup.c cgroup: drop const from @buffer of cftype->write_string() 2014-03-19 10:23:54 -04:00
hugetlb.c hugetlb: add support for gigantic page allocation at runtime 2014-06-04 16:53:59 -07:00
hwpoison-inject.c mm/hwpoison: add '#' to hwpoison_inject 2014-01-21 16:19:48 -08:00
init-mm.c
internal.h mm: fold mlocked_vma_newpage() into its only call site 2014-06-04 16:54:07 -07:00
interval_tree.c
iov_iter.c take iov_iter stuff to mm/iov_iter.c 2014-04-01 23:19:30 -04:00
Kconfig hugetlb: restrict hugepage_migration_support() to x86_64 2014-06-04 16:53:51 -07:00
Kconfig.debug
kmemcheck.c
kmemleak-test.c
kmemleak.c mem-hotplug: implement get/put_online_mems 2014-06-04 16:53:59 -07:00
ksm.c mm: close PageTail race 2014-03-04 07:55:47 -08:00
list_lru.c mm: keep page cache radix tree nodes in check 2014-04-03 16:21:01 -07:00
maccess.c
madvise.c mm: madvise: fix MADV_WILLNEED on shmem swapouts 2014-05-23 09:37:29 -07:00
Makefile mm: move get_user_pages()-related code to separate file 2014-06-04 16:54:04 -07:00
memblock.c mm/memblock.c: use PFN_DOWN 2014-06-04 16:54:02 -07:00
memcontrol.c memcg: cleanup kmem cache creation/destruction functions naming 2014-06-04 16:54:08 -07:00
memory_hotplug.c mm, migration: add destination page freeing callback 2014-06-04 16:54:06 -07:00
memory-failure.c mm, migration: add destination page freeing callback 2014-06-04 16:54:06 -07:00
memory.c mm: move get_user_pages()-related code to separate file 2014-06-04 16:54:04 -07:00
mempolicy.c mm, migration: add destination page freeing callback 2014-06-04 16:54:06 -07:00
mempool.c mm/mempool: warn about __GFP_ZERO usage 2014-06-04 16:53:58 -07:00
migrate.c mm, migration: add destination page freeing callback 2014-06-04 16:54:06 -07:00
mincore.c mm + fs: prepare for non-page entries in page cache radix trees 2014-04-03 16:21:00 -07:00
mlock.c mm: try_to_unmap_cluster() should lock_page() before mlocking 2014-04-07 16:35:57 -07:00
mm_init.c mm: bring back /sys/kernel/mm 2014-01-27 21:02:39 -08:00
mmap.c mm/mmap.c: remove the first mapping check 2014-06-04 16:54:01 -07:00
mmu_context.c sched/mm: call finish_arch_post_lock_switch in idle_task_exit and use_mm 2014-02-21 08:50:17 +01:00
mmu_notifier.c mm: audit/fix non-modular users of module_init in core code 2014-01-23 16:36:52 -08:00
mmzone.c mm: numa: Change page last {nid,pid} into {cpu,pid} 2013-10-09 14:47:45 +02:00
mprotect.c mm: move mmu notifier call from change_protection to change_pmd_range 2014-04-07 16:35:50 -07:00
mremap.c mm, thp: close race between mremap() and split_huge_page() 2014-05-11 17:55:48 +09:00
msync.c
nobootmem.c mm/nobootmem.c: mark function as static 2014-04-03 16:21:02 -07:00
nommu.c mm: fix 'ERROR: do not initialise globals to 0 or NULL' and coding style 2014-04-07 16:35:55 -07:00
oom_kill.c mm, oom: base root bonus on current usage 2014-01-30 16:56:56 -08:00
page_alloc.c mm: page_alloc: use word-based accesses for get/set pageblock bitmaps 2014-06-04 16:54:09 -07:00
page_cgroup.c mm/page_cgroup.c: mark functions as static 2014-04-03 16:21:02 -07:00
page_io.c swap: use bdev_read_page() / bdev_write_page() 2014-06-04 16:54:02 -07:00
page_isolation.c mm: memory-hotplug: enable memory hotplug to handle hugepage 2013-09-11 15:57:48 -07:00
page-writeback.c mm: replace __get_cpu_var uses with this_cpu_ptr 2014-06-04 16:54:03 -07:00
pagewalk.c mm/pagewalk.c: fix walk_page_range() access of wrong PTEs 2013-10-30 14:27:03 -07:00
percpu-km.c
percpu-vm.c
percpu.c percpu: make pcpu_alloc_chunk() use pcpu_mem_free() instead of kfree() 2014-04-14 16:18:06 -04:00
pgtable-generic.c mm: fix TLB flush race between migration, and change_protection_range 2013-12-18 19:04:51 -08:00
process_vm_access.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-04-12 14:49:50 -07:00
quicklist.c
readahead.c mm/readahead.c: inline ra_submit 2014-04-07 16:35:58 -07:00
rmap.c mm: fold mlocked_vma_newpage() into its only call site 2014-06-04 16:54:07 -07:00
shmem.c mm: Initialize error in shmem_file_aio_read() 2014-04-13 14:10:26 -07:00
slab_common.c slab: delete cache from list after __kmem_cache_shutdown succeeds 2014-06-04 16:54:08 -07:00
slab.c memcg, slab: merge memcg_{bind,release}_pages to memcg_{un}charge_slab 2014-06-04 16:54:01 -07:00
slab.h memcg, slab: merge memcg_{bind,release}_pages to memcg_{un}charge_slab 2014-06-04 16:54:01 -07:00
slob.c slab: get_online_mems for kmem_cache_{create,destroy,shrink} 2014-06-04 16:53:59 -07:00
slub.c mm: replace __get_cpu_var uses with this_cpu_ptr 2014-06-04 16:54:03 -07:00
sparse-vmemmap.c mm/sparse: use memblock apis for early memory allocations 2014-01-21 16:19:47 -08:00
sparse.c mm: use macros from compiler.h instead of __attribute__((...)) 2014-04-07 16:35:54 -07:00
swap_state.c swap: add a simple detector for inappropriate swapin readahead 2014-02-06 13:48:51 -08:00
swap.c mm: introdule compound_head_by_tail() 2014-06-04 16:54:03 -07:00
swapfile.c swap: change swap_list_head to plist, add swap_avail_head 2014-06-04 16:54:07 -07:00
truncate.c mm: filemap: update find_get_pages_tag() to deal with shadow entries 2014-05-06 13:04:59 -07:00
util.c nick kvfree() from apparmor 2014-05-06 14:02:53 -04:00
vmacache.c mm,vmacache: optimize overflow system-wide flushing 2014-06-04 16:53:57 -07:00
vmalloc.c mm/vmalloc.c: replace seq_printf by seq_puts 2014-06-04 16:54:04 -07:00
vmpressure.c arm, pm, vmpressure: add missing slab.h includes 2014-02-03 13:24:01 -05:00
vmscan.c mm: shrinker: add nid to tracepoint output 2014-06-04 16:54:04 -07:00
vmstat.c mm: use the light version __mod_zone_page_state in mlocked_vma_newpage() 2014-06-04 16:54:07 -07:00
workingset.c mm: keep page cache radix tree nodes in check 2014-04-03 16:21:01 -07:00
zbud.c mm/zbud: fix some trivial typos in comments 2013-09-11 15:57:35 -07:00
zsmalloc.c mm: replace __get_cpu_var uses with this_cpu_ptr 2014-06-04 16:54:03 -07:00
zswap.c Merge branch 'akpm' (incoming from Andrew) 2014-04-07 16:38:06 -07:00