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authorDimitri Sivanich <sivanich@sgi.com>2011-10-31 17:09:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-10-31 17:30:51 -0700
commita1cb2c60ddc98ff4e5246f410558805401ceee67 (patch)
tree49e3e620ff2974dc78fad8df0b343b07b75be407 /mm/vmstat.c
parent3d470fc385defa60d9af610f05db8e7f8b4f2f5e (diff)
downloadlinux-a1cb2c60ddc98ff4e5246f410558805401ceee67.tar.gz
mm/vmstat.c: cache align vm_stat
Avoid false sharing of the vm_stat array. This was found to adversely affect tmpfs I/O performance. Tests run on a 640 cpu UV system. With 120 threads doing parallel writes, each to different tmpfs mounts: No patch: ~300 MB/sec With vm_stat alignment: ~430 MB/sec Signed-off-by: Dimitri Sivanich <sivanich@sgi.com> Acked-by: Christoph Lameter <cl@gentwo.org> Acked-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmstat.c')
-rw-r--r--mm/vmstat.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 56e529a4051..8fd603b1665 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -78,7 +78,7 @@ void vm_events_fold_cpu(int cpu)
*
* vm_stat contains the global counters
*/
-atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];
+atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS] __cacheline_aligned_in_smp;
EXPORT_SYMBOL(vm_stat);
#ifdef CONFIG_SMP