[PATCH v13 9/9] lib/nodemask: Optimize node_random for nodemask with single NUMA node

["Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>]

The most common case for certain node_random usage (demotion nodemask) is with
nodemask weight 1. We can avoid calling get_random_init() in that case and
always return the only node set in the nodemask.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
---
 lib/nodemask.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/nodemask.c b/lib/nodemask.c
index e22647f5181b..c91a6b0404a5 100644
--- a/lib/nodemask.c
+++ b/lib/nodemask.c
@@ -20,12 +20,21 @@ EXPORT_SYMBOL(__next_node_in);
  */
 int node_random(const nodemask_t *maskp)
 {
-	int w, bit = NUMA_NO_NODE;
+	int w, bit;
 
 	w = nodes_weight(*maskp);
-	if (w)
+	switch (w) {
+	case 0:
+		bit = NUMA_NO_NODE;
+		break;
+	case 1:
+		bit = __first_node(maskp);
+		break;
+	default:
 		bit = bitmap_ord_to_pos(maskp->bits,
-			get_random_int() % w, MAX_NUMNODES);
+					get_random_int() % w, MAX_NUMNODES);
+		break;
+	}
 	return bit;
 }
 #endif
-- 
2.37.1