linux/mm
Waiman Long f8303c2582 mm, thp: move invariant bug check out of loop in __split_huge_page_map
In __split_huge_page_map(), the check for page_mapcount(page) is
invariant within the for loop.  Because of the fact that the macro is
implemented using atomic_read(), the redundant check cannot be optimized
away by the compiler leading to unnecessary read to the page structure.

This patch moves the invariant bug check out of the loop so that it will
be done only once.  On a 3.16-rc1 based kernel, the execution time of a
microbenchmark that broke up 1000 transparent huge pages using munmap()
had an execution time of 38,245us and 38,548us with and without the
patch respectively.  The performance gain is about 1%.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Scott J Norton <scott.norton@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-08-06 18:01:16 -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
cma.c mm, CMA: clean-up log message 2014-08-06 18:01:16 -07:00
compaction.c mm, compaction: properly signal and act upon lock and need_sched() contention 2014-06-04 16:54:11 -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 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-08-04 16:23:30 -07:00
fremap.c mm: mark remap_file_pages() syscall as deprecated 2014-06-06 16:08:17 -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, thp: move invariant bug check out of loop in __split_huge_page_map 2014-08-06 18:01:16 -07:00
hugetlb_cgroup.c cgroup: replace cgroup_add_cftypes() with cgroup_add_legacy_cftypes() 2014-07-15 11:05:09 -04:00
hugetlb.c kexec: export free_huge_page to VMCOREINFO 2014-07-30 17:16:13 -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/internal.h: use nth_page 2014-08-06 18:01:16 -07:00
interval_tree.c
iov_iter.c bio_vec-backed iov_iter 2014-05-06 17:39:45 -04:00
Kconfig CMA: generalize CMA reserved area management functionality 2014-08-06 18:01:16 -07:00
Kconfig.debug
kmemcheck.c
kmemleak-test.c mm/kmemleak-test.c: use pr_fmt for logging 2014-06-06 16:08:18 -07:00
kmemleak.c mm: introduce kmemleak_update_trace() 2014-06-06 16:08:17 -07:00
ksm.c sched: Remove proliferation of wait_on_bit() action functions 2014-07-16 15:10:39 +02:00
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 CMA: generalize CMA reserved area management functionality 2014-08-06 18:01:16 -07:00
memblock.c mm/memblock.c: call kmemleak directly from memblock_(alloc|free) 2014-06-06 16:08:17 -07:00
memcontrol.c Merge branch 'for-3.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-08-04 10:11:28 -07:00
memory_hotplug.c mem-hotplug: introduce MMOP_OFFLINE to replace the hard coding -1 2014-08-06 18:01:16 -07:00
memory-failure.c hwpoison: call action_result() in failure path of hwpoison_user_mappings() 2014-07-30 17:16:13 -07:00
memory.c mm/memory.c: use entry = ACCESS_ONCE(*pte) in handle_pte_fault() 2014-08-06 18:01:15 -07:00
mempolicy.c Merge branch 'for-3.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-07-10 11:38:23 -07:00
mempool.c mm/mempool.c: update the kmemleak stack trace for mempool allocations 2014-06-06 16:08:17 -07:00
migrate.c mm: fix direct reclaim writeback regression 2014-07-26 14:38:50 -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: convert some level-less printks to pr_* 2014-06-06 16:08:18 -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 msync: fix incorrect fstart calculation 2014-07-03 09:21:53 -07:00
nobootmem.c mm/memblock.c: call kmemleak directly from memblock_(alloc|free) 2014-06-06 16:08:17 -07:00
nommu.c mm: nommu: per-thread vma cache fix 2014-06-23 16:47:43 -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: simplify drain_zone_pages by using min() 2014-08-06 18:01:16 -07:00
page_cgroup.c mm/page_cgroup.c: mark functions as static 2014-04-03 16:21:02 -07:00
page_io.c fix __swap_writepage() compile failure on old gcc versions 2014-06-14 19:30:48 -05:00
page_isolation.c mm: memory-hotplug: enable memory hotplug to handle hugepage 2013-09-11 15:57:48 -07:00
page-writeback.c mm/page-writeback.c: fix divide by zero in bdi_dirty_limits() 2014-07-30 17:16:13 -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: Use ALIGN macro instead of hand coding alignment calculation 2014-06-19 11:00:27 -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 start adding the tag to iov_iter 2014-05-06 17:32:49 -04:00
quicklist.c
readahead.c mm/readahead.c: remove unused file_ra_state from count_history_pages 2014-08-06 18:01:15 -07:00
rmap.c mm/rmap.c: fix pgoff calculation to handle hugepage correctly 2014-07-23 15:10:54 -07:00
shmem.c shmem: fix splicing from a hole while it's punched 2014-07-23 15:10:55 -07:00
slab_common.c mm: move slab related stuff from util.c to slab_common.c 2014-08-06 18:01:15 -07:00
slab.c mm/slab.c: fix comments 2014-08-06 18:01:15 -07:00
slab.h slab: convert last use of __FUNCTION__ to __func__ 2014-08-06 18:01:15 -07:00
slob.c slab: get_online_mems for kmem_cache_{create,destroy,shrink} 2014-06-04 16:53:59 -07:00
slub.c slab: fix the alias count (via sysfs) of slab cache 2014-08-06 18:01:15 -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 mm: page_alloc: convert hot/cold parameter and immediate callers to bool 2014-06-04 16:54:09 -07:00
swap.c mm: non-atomically mark page accessed during page cache allocation where possible 2014-06-04 16:54:10 -07:00
swapfile.c mm/swapfile.c: delete the "last_in_cluster < scan_base" loop in the body of scan_swap_map() 2014-06-04 16:54:12 -07:00
truncate.c mm/fs: fix pessimization in hole-punching pagecache 2014-07-23 15:10:55 -07:00
util.c mm: move slab related stuff from util.c to slab_common.c 2014-08-06 18:01:15 -07:00
vmacache.c mm,vmacache: optimize overflow system-wide flushing 2014-06-04 16:53:57 -07:00
vmalloc.c vmalloc: use rcu list iterator to reduce vmap_area_lock contention 2014-08-06 18:01:15 -07:00
vmpressure.c arm, pm, vmpressure: add missing slab.h includes 2014-02-03 13:24:01 -05:00
vmscan.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2014-06-12 10:30:18 -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.c: make size unsigned like unique callsite 2014-06-04 16:54:13 -07:00
zsmalloc.c zsmalloc: fixup trivial zs size classes value in comments 2014-06-04 16:54:13 -07:00
zswap.c mm/zswap: NUMA aware allocation for zswap_dstmem 2014-06-04 16:54:14 -07:00