FAILED: patch "[PATCH] mm, numa: really disable NUMA balancing by default on single" failed to apply to 3.10-stable tree

The patch below does not apply to the 3.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Mel Gorman <[email protected]>
Date: Thu, 14 May 2015 15:17:09 -0700
Subject: [PATCH] mm, numa: really disable NUMA balancing by default on single
node machines

NUMA balancing is meant to be disabled by default on UMA machines but the check is using nr_node_ids (highest node) instead of num_online_nodes (online nodes).

The consequences are that a UMA machine with a node ID of 1 or higher will enable NUMA balancing. This will incur useless overhead due to minor faults with the impact depending on the workload. These are the impact on the stats when running a kernel build on a single node machine whose node ID happened to be 1:

vanilla patched

  NUMA base PTE updates          5113158           0
  NUMA huge PMD updates              643           0
  NUMA page range updates        5442374           0
  NUMA hint faults               2109622           0
  NUMA hint local faults         2109622           0

NUMA hint local percent 100 100
NUMA pages migrated 0 0

index ede26291d4aa..747743237d9f 100644
@@ -2518,7 +2518,7 @@ static void __init check_numabalancing_enable(void)
 	if (numabalancing_override)
 		set_numabalancing_state(numabalancing_override == 1);
 
-	if (nr_node_ids > 1 && !numabalancing_override) {
+	if (num_online_nodes() > 1 && !numabalancing_override) {
 		pr_info("%s automatic NUMA balancing. "
 			"Configure with numa_balancing= or the "
 			"kernel.numa_balancing sysctl",