mm: sched: numa: Control enabling and disabling of NUMA balancing

This patch adds Kconfig options and kernel parameters to allow the
enabling and disabling of automatic NUMA balancing. The existance
of such a switch was and is very important when debugging problems
related to transparent hugepages and we should have the same for
automatic NUMA placement.

Signed-off-by: Mel Gorman <mgorman@suse.de>
diff --git a/init/Kconfig b/init/Kconfig
index 9f00f00..18e2a59 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -720,6 +720,14 @@
 	depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
 	depends on NUMA_BALANCING
 
+config NUMA_BALANCING_DEFAULT_ENABLED
+	bool "Automatically enable NUMA aware memory/task placement"
+	default y
+	depends on NUMA_BALANCING
+	help
+	  If set, autonumic NUMA balancing will be enabled if running on a NUMA
+	  machine.
+
 config NUMA_BALANCING
 	bool "Memory placement aware NUMA scheduler"
 	default y