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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>
This commit is contained in:
Dimitri Sivanich 2011-10-31 17:09:46 -07:00 committed by Linus Torvalds
parent 3d470fc385
commit a1cb2c60dd
1 changed files with 1 additions and 1 deletions
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2
mm/vmstat.c
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@ -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