Shaohua Li ff36b80162 shmem: reduce pagefault lock contention ... I'm running a shmem pagefault test case (see attached file) under a 64 CPU system. Profile shows shmem_inode_info->lock is heavily contented and 100% CPUs time are trying to get the lock. In the pagefault (no swap) case, shmem_getpage gets the lock twice, the last one is avoidable if we prealloc a page so we could reduce one time of locking. This is what below patch does. The result of the test case: 2.6.35-rc3: ~20s 2.6.35-rc3 + patch: ~12s so this is 40% improvement. One might argue if we could have better locking for shmem. But even shmem is lockless, the pagefault will soon have pagecache lock heavily contented because shmem must add new page to pagecache. So before we have better locking for pagecache, improving shmem locking doesn't have too much improvement. I did a similar pagefault test against a ramfs file, the test result is ~10.5s. [akpm@linux-foundation.org: fix comment, clean up code layout, elimintate code duplication] Signed-off-by: Shaohua Li <shaohua.li@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: "Zhang, Yanmin" <yanmin.zhang@intel.com> Cc: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2010-08-09 20:44:58 -07:00
..
backing-dev.c	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip	2010-08-06 09:23:07 -07:00
bootmem.c	x86,nobootmem: make alloc_bootmem_node fall back to other node when 32bit numa is used	2010-07-20 16:25:40 -07:00
bounce.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
compaction.c	mm: compaction: add a tunable that decides when memory should be compacted and when it should be reclaimed	2010-05-25 08:06:59 -07:00
debug-pagealloc.c
dmapool.c
fadvise.c	readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM	2010-03-06 11:26:25 -08:00
failslab.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
filemap.c	gcc-4.6: mm: fix unused but set warnings	2010-08-09 20:44:58 -07:00
filemap_xip.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
fremap.c	mm: clean up mm_counter	2010-03-06 11:26:23 -08:00
highmem.c	mm,kdb,kgdb: Add a debug reference for the kdb kmap usage	2010-08-05 09:22:24 -05:00
hugetlb.c	hugetlb: call mmu notifiers on hugepage cow	2010-08-09 20:44:54 -07:00
hwpoison-inject.c
init-mm.c	mm: provide init_mm mm_context initializer	2010-08-09 20:44:54 -07:00
internal.h
Kconfig	lmb: rename to memblock	2010-07-14 17:14:00 +10:00
Kconfig.debug
kmemcheck.c	kmemcheck: Fix build errors due to missing slab.h	2010-03-30 22:02:32 +09:00
kmemleak-test.c
kmemleak.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
ksm.c	mm: extend KSM refcounts to the anon_vma root	2010-08-09 20:44:55 -07:00
maccess.c
madvise.c
Makefile	lmb: rename to memblock	2010-07-14 17:14:00 +10:00
memblock.c	lmb: rename to memblock	2010-07-14 17:14:00 +10:00
memcontrol.c	memcg: fix wake up in oom wait queue	2010-06-29 15:29:30 -07:00
memory-failure.c	KVM: Fix a race condition for usage of is_hwpoison_address()	2010-08-01 10:47:11 +03:00
memory.c	gcc-4.6: mm: fix unused but set warnings	2010-08-09 20:44:58 -07:00
memory_hotplug.c	mem-hotplug: fix potential race while building zonelist for new populated zone	2010-05-25 08:07:02 -07:00
mempolicy.c	mempolicy: reduce stack size of migrate_pages()	2010-08-09 20:44:58 -07:00
mempool.c
migrate.c	mm: extend KSM refcounts to the anon_vma root	2010-08-09 20:44:55 -07:00
mincore.c	mincore: do nested page table walks	2010-05-25 08:06:58 -07:00
mlock.c	x86, perf, bts, mm: Delete the never used BTS-ptrace code	2010-03-26 11:33:55 +01:00
mm_init.c
mmap.c	mm: always lock the root (oldest) anon_vma	2010-08-09 20:44:55 -07:00
mmu_context.c	exit: fix oops in sync_mm_rss	2010-03-24 16:31:21 -07:00
mmu_notifier.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
mmzone.c
mprotect.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
mremap.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
msync.c	sanitize vfs_fsync calling conventions	2010-05-21 18:31:21 -04:00
nommu.c	nommu: allow private mappings of read-only devices	2010-05-26 08:19:23 -07:00
oom_kill.c	oom: fold __out_of_memory into out_of_memory	2010-08-09 20:44:57 -07:00
page-writeback.c	writeback: remove writeback_inodes_wbc	2010-07-06 08:54:03 +02:00
page_alloc.c	mm: rename try_set_zone_oom() to try_set_zonelist_oom()	2010-08-09 20:44:57 -07:00
page_cgroup.c	kmemleak: Annotate false positive in init_section_page_cgroup()	2010-07-19 11:54:14 +01:00
page_io.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
page_isolation.c
pagewalk.c	pagemap: fix pfn calculation for hugepage	2010-04-07 08:38:04 -07:00
percpu-km.c	percpu: implement kernel memory based chunk allocation	2010-05-01 08:30:50 +02:00
percpu-vm.c	percpu: move vmalloc based chunk management into percpu-vm.c	2010-05-01 08:30:50 +02:00
percpu.c	percpu: allow limited allocation before slab is online	2010-06-27 18:50:00 +02:00
percpu_up.c	percpu: don't implicitly include slab.h from percpu.h	2010-03-30 22:02:32 +09:00
prio_tree.c
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.c: fix comment	2010-05-25 08:07:00 -07:00
rmap.c	mm: extend KSM refcounts to the anon_vma root	2010-08-09 20:44:55 -07:00
shmem.c	shmem: reduce pagefault lock contention	2010-08-09 20:44:58 -07:00
slab.c	gcc-4.6: mm: fix unused but set warnings	2010-08-09 20:44:58 -07:00
slob.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6	2010-08-06 11:44:08 -07:00
slub.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6	2010-08-06 11:44:08 -07:00
sparse-vmemmap.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
sparse.c	sparsemem: on no vmemmap path put mem_map on node high too	2010-05-25 08:06:56 -07:00
swap.c	mm: export lru_cache_add_*() to modules	2010-05-25 15:06:06 +02:00
swap_state.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
swapfile.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging-2.6	2010-05-21 15:26:46 -07:00
thrash.c
truncate.c	fs: introduce new truncate sequence	2010-05-27 22:15:33 -04:00
util.c	mm: use memdup_user	2010-08-09 20:44:54 -07:00
vmalloc.c	mm: use ERR_CAST	2010-08-09 20:44:54 -07:00
vmscan.c	mm/vmscan.c: fix mapping use after free	2010-07-20 16:25:40 -07:00
vmstat.c	mm: use for_each_online_cpu() in vmstat	2010-08-09 20:44:57 -07:00