[S390] cpu topology: introduce kernel parameter

Introduce a topology=[on|off] kernel parameter which allows to switch cpu topology on/off. Default will be off, since it looks like that for some workloards this doesn't behave very well (on s390). Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

[S390] cpu topology: introduce kernel parameter
Introduce a topology=[on|off] kernel parameter which allows to switch cpu topology on/off. Default will be off, since it looks like that for some workloards this doesn't behave very well (on s390). Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Heiko Carstens · Martin Schwidefsky
1 parent 9fee8db222
Showing 2 changed files with 19 additions and 1 deletions Side-by-side Diff
Documentation/kernel-parameters.txt
arch/s390/kernel/topology.c
@@ -2252,6 +2252,14 @@
 			See comment before function dc390_setup() in
 			drivers/scsi/tmscsim.c.
  
+	topology=	[S390]
+			Format: {off | on}
+			Specify if the kernel should make use of the cpu
+			topology informations if the hardware supports these.
+			The scheduler will make use of these informations and
+			e.g. base its process migration decisions on it.
+			Default is off.
+
 	tp720=		[HW,PS2]
  
 	trix=		[HW,OSS] MediaTrix AudioTrix Pro
@@ -58,6 +58,7 @@
 	cpumask_t mask;
 };
  
+static int topology_enabled;
 static void topology_work_fn(struct work_struct *work);
 static struct tl_info *tl_info;
 static struct core_info core_info;
@@ -78,7 +79,7 @@
 	cpumask_t mask;
  
 	cpus_clear(mask);
-	if (!machine_has_topology)
+	if (!topology_enabled || !machine_has_topology)
 		return cpu_possible_map;
 	spin_lock_irqsave(&topology_lock, flags);
 	while (core) {
@@ -262,6 +263,15 @@
 {
 	schedule_work(&topology_work);
 }
+
+static int __init early_parse_topology(char *p)
+{
+	if (strncmp(p, "on", 2))
+		return 0;
+	topology_enabled = 1;
+	return 0;
+}
+early_param("topology", early_parse_topology);
  
 static int __init init_topology_update(void)
 {
...	...	@@ -2252,6 +2252,14 @@
2252	2252	See comment before function dc390_setup() in
2253	2253	drivers/scsi/tmscsim.c.
2254	2254
	2255	+ topology= [S390]
	2256	+ Format: {off \| on}
	2257	+ Specify if the kernel should make use of the cpu
	2258	+ topology informations if the hardware supports these.
	2259	+ The scheduler will make use of these informations and
	2260	+ e.g. base its process migration decisions on it.
	2261	+ Default is off.
	2262	+
2255	2263	tp720= [HW,PS2]
2256	2264
2257	2265	trix= [HW,OSS] MediaTrix AudioTrix Pro
...	...	@@ -58,6 +58,7 @@
58	58	cpumask_t mask;
59	59	};
60	60
	61	+static int topology_enabled;
61	62	static void topology_work_fn(struct work_struct *work);
62	63	static struct tl_info *tl_info;
63	64	static struct core_info core_info;
...	...	@@ -78,7 +79,7 @@
78	79	cpumask_t mask;
79	80
80	81	cpus_clear(mask);
81		- if (!machine_has_topology)
	82	+ if (!topology_enabled \|\| !machine_has_topology)
82	83	return cpu_possible_map;
83	84	spin_lock_irqsave(&topology_lock, flags);
84	85	while (core) {
...	...	@@ -262,6 +263,15 @@
262	263	{
263	264	schedule_work(&topology_work);
264	265	}
	266	+
	267	+static int __init early_parse_topology(char *p)
	268	+{
	269	+ if (strncmp(p, "on", 2))
	270	+ return 0;
	271	+ topology_enabled = 1;
	272	+ return 0;
	273	+}
	274	+early_param("topology", early_parse_topology);
265	275
266	276	static int __init init_topology_update(void)
267	277	{