[v2 PATCH 3/4] timers: sysfs hook to enable timer migration

[Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx>]

* Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx> [2009-03-04 17:42:49]:

This patch creates the necessary sysfs interface for timer migration.

The interface is located at
/sys/devices/system/cpu/enable_timer_migration

This enables timer migration.

        echo 1 > /sys/devices/system/cpu/enable_timer_migration

similarly,

	echo 0 > /sys/devices/system/cpu/enable_timer_migration

disables timer migration.


Signed-off-by: Arun R Bharadwaj <arun@xxxxxxxxxxxxxxxxxx>
---
 include/linux/sched.h |    1 +
 kernel/sched.c        |   28 ++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

Index: linux.trees.git/include/linux/sched.h
===================================================================
--- linux.trees.git.orig/include/linux/sched.h
+++ linux.trees.git/include/linux/sched.h
@@ -803,6 +803,7 @@ enum powersavings_balance_level {
 };
 
 extern int sched_mc_power_savings, sched_smt_power_savings;
+extern int enable_timer_migration;
 
 static inline int sd_balance_for_mc_power(void)
 {
Index: linux.trees.git/kernel/sched.c
===================================================================
--- linux.trees.git.orig/kernel/sched.c
+++ linux.trees.git/kernel/sched.c
@@ -7445,6 +7445,7 @@ static void sched_domain_node_span(int n
 #endif /* CONFIG_NUMA */
 
 int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
+int enable_timer_migration;
 
 /*
  * The cpus mask in sched_group and sched_domain hangs off the end.
@@ -8317,6 +8318,29 @@ static SYSDEV_CLASS_ATTR(sched_smt_power
 		   sched_smt_power_savings_store);
 #endif
 
+static ssize_t timer_migration_show(struct sysdev_class *class,
+					   char *page)
+{
+	return sprintf(page, "%u\n", enable_timer_migration);
+}
+static ssize_t timer_migration_store(struct sysdev_class *class,
+					    const char *buf, size_t count)
+{
+	unsigned int level = 0;
+
+	if (sscanf(buf, "%u", &level) != 1)
+		return -EINVAL;
+
+	if (level > 1)
+		return -EINVAL;
+
+	enable_timer_migration = level;
+
+	return count;
+}
+static SYSDEV_CLASS_ATTR(enable_timer_migration, 0644,
+			 timer_migration_show,
+			 timer_migration_store);
 int __init sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
 {
 	int err = 0;
@@ -8331,6 +8355,10 @@ int __init sched_create_sysfs_power_savi
 		err = sysfs_create_file(&cls->kset.kobj,
 					&attr_sched_mc_power_savings.attr);
 #endif
+	if (!err)
+		err = sysfs_create_file(&cls->kset.kobj,
+					&attr_enable_timer_migration.attr);
+
 	return err;
 }
 #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
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