[S390] topology: add SCHED_MC config option

This allows us to easily check for performance differences seen with
!CONFIG_SCHED_MC and topology=off.
Actually there shouldn't be any (besides a small overhead because of
additional code).
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -196,9 +196,18 @@ config HOTPLUG_CPU
 	  can be controlled through /sys/devices/system/cpu/cpu#.
 	  Say N if you want to disable CPU hotplug.
 
+config SCHED_MC
+	def_bool y
+	prompt "Multi-core scheduler support"
+	depends on SMP
+	help
+	  Multi-core scheduler support improves the CPU scheduler's decision
+	  making when dealing with multi-core CPU chips at a cost of slightly
+	  increased overhead in some places.
+
 config SCHED_BOOK
 	bool "Book scheduler support"
-	depends on SMP
+	depends on SMP && SCHED_MC
 	help
 	  Book scheduler support improves the CPU scheduler's decision making
 	  when dealing with machines that have several books.

arch/s390/kernel/sysinfo.c

@@ -106,11 +106,13 @@ static int stsi_15_1_x(struct sysinfo_15_1_x *info, char *page, int len)
 	for (i = 0; i < TOPOLOGY_NR_MAG; i++)
 		len += sprintf(page + len, " %d", info->mag[i]);
 	len += sprintf(page + len, "\n");
+#ifdef CONFIG_SCHED_MC
 	store_topology(info);
 	len += sprintf(page + len, "CPU Topology SW:     ");
 	for (i = 0; i < TOPOLOGY_NR_MAG; i++)
 		len += sprintf(page + len, " %d", info->mag[i]);
 	len += sprintf(page + len, "\n");
+#endif
 	return len;
 }