mm: numa: limit scope of lock for NUMA migrate rate limiting

NUMA migrate rate limiting protects a migration counter and window using
a lock but in some cases this can be a contended lock.  It is not
critical that the number of pages be perfect, lost updates are
acceptable.  Reduce the importance of this lock.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 4 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 67ab5febabf7..5f2052c83154 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -764,10 +764,7 @@ typedef struct pglist_data {
         int kswapd_max_order;
         enum zone_type classzone_idx;
 #ifdef CONFIG_NUMA_BALANCING
-        /*
-         * Lock serializing the per destination node AutoNUMA memory
-         * migration rate limiting data.
-         */
+        /* Lock serializing the migrate rate limiting window */
         spinlock_t numabalancing_migrate_lock;
 
         /* Rate limiting time interval */