From: Dimitri Sivanich <[email protected]>
commit a1cb2c60ddc98ff4e5246f410558805401ceee67 upstream.
Stable note: Not tracked on Bugzilla. This patch is known to make a big
difference to tmpfs performance on larger machines.
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 <[email protected]>
Acked-by: Christoph Lameter <[email protected]>
Acked-by: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Mel Gorman <[email protected]>
---
mm/vmstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 20c18b7..6559013 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
--
1.7.9.2
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