[patch v5 05/15] sched: add sysfs interface for sched_balance_policy selection

Alex Shi
2013-02-18T05:10:56Z

This patch add the power aware scheduler knob into sysfs:

$cat /sys/devices/system/cpu/sched_balance_policy/available_sched_balance_policy
performance powersaving balance
$cat /sys/devices/system/cpu/sched_balance_policy/current_sched_balance_policy
powersaving

This means the using sched balance policy is 'powersaving'.

User can change the policy by commend 'echo':
echo performance > /sys/devices/system/cpu/sched_balance_policy/current_sched_balance_policy

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
Documentation/ABI/testing/sysfs-devices-system-cpu | 26 ++++++++
kernel/sched/fair.c | 73 ++++++++++++++++++++++
2 files changed, 99 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 6943133..3283a86 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -53,6 +53,32 @@ Description: Dynamic addition and removal of CPU's. This is not hotplug
the system. Information writtento the file to remove CPU's
is architecture specific.

+What: /sys/devices/system/cpu/sched_balance_policy/current_sched_balance_policy
+ /sys/devices/system/cpu/sched_balance_policy/available_sched_balance_policy
+Date: Oct 2012
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description: CFS scheduler policy showing and setting interface.
+
+ available_sched_balance_policy shows there are 3 kinds of
+ policies:
+ performance, balance and powersaving.
+ current_sched_balance_policy shows current scheduler policy.
+ User can change the policy by writing it.
+
+ Policy decides the CFS scheduler how to distribute tasks onto
+ different CPU unit.
+
+ performance: try to spread tasks onto more CPU sockets,
+ more CPU cores. performance oriented.
+
+ powersaving: try to pack tasks onto same core or same CPU
+ until every LCPUs are busy in the core or CPU socket.
+ powersaving oriented.
+
+ balance: try to pack tasks onto same core or same CPU
+ until full powered CPUs are busy.
+ balance between performance and powersaving.
+
What: /sys/devices/system/cpu/cpu#/node
Date: October 2009
Contact: Linux memory management mailing list <linux-mm@kvack.org>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2f98ffb..fcdb21f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6108,6 +6108,79 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task
/* The default scheduler policy is 'performance'. */
int __read_mostly sched_balance_policy = SCHED_POLICY_PERFORMANCE;

+#ifdef CONFIG_SYSFS
+static ssize_t show_available_sched_balance_policy(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ return sprintf(buf, "performance balance powersaving\n");
+}
+
+static ssize_t show_current_sched_balance_policy(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ if (sched_balance_policy == SCHED_POLICY_PERFORMANCE)
+ return sprintf(buf, "performance\n");
+ else if (sched_balance_policy == SCHED_POLICY_POWERSAVING)
+ return sprintf(buf, "powersaving\n");
+ else if (sched_balance_policy == SCHED_POLICY_BALANCE)
+ return sprintf(buf, "balance\n");
+ return 0;
+}
+
+static ssize_t set_sched_balance_policy(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ unsigned int ret = -EINVAL;
+ char str_policy[16];
+
+ ret = sscanf(buf, "%15s", str_policy);
+ if (ret != 1)
+ return -EINVAL;
+
+ if (!strcmp(str_policy, "performance"))
+ sched_balance_policy = SCHED_POLICY_PERFORMANCE;
+ else if (!strcmp(str_policy, "powersaving"))
+ sched_balance_policy = SCHED_POLICY_POWERSAVING;
+ else if (!strcmp(str_policy, "balance"))
+ sched_balance_policy = SCHED_POLICY_BALANCE;
+ else
+ return -EINVAL;
+
+ return count;
+}
+
+/*
+ * * Sysfs setup bits:
+ * */
+static DEVICE_ATTR(current_sched_balance_policy, 0644,
+ show_current_sched_balance_policy, set_sched_balance_policy);
+
+static DEVICE_ATTR(available_sched_balance_policy, 0444,
+ show_available_sched_balance_policy, NULL);
+
+static struct attribute *sched_balance_policy_default_attrs[] = {
+ &dev_attr_current_sched_balance_policy.attr,
+ &dev_attr_available_sched_balance_policy.attr,
+ NULL
+};
+static struct attribute_group sched_balance_policy_attr_group = {
+ .attrs = sched_balance_policy_default_attrs,
+ .name = "sched_balance_policy",
+};
+
+int __init create_sysfs_sched_balance_policy_group(struct device *dev)
+{
+ return sysfs_create_group(&dev->kobj, &sched_balance_policy_attr_group);
+}
+
+static int __init sched_balance_policy_sysfs_init(void)
+{
+ return create_sysfs_sched_balance_policy_group(cpu_subsys.dev_root);
+}
+
+core_initcall(sched_balance_policy_sysfs_init);
+#endif /* CONFIG_SYSFS */
+
/*
* All the scheduling class methods:
*/
--
1.7.12