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Subject[PATCH v3 14/22] sched: add sched_policy and it's sysfs interface
Date
This patch add the power aware scheduler knob into sysfs:

$cat /sys/devices/system/cpu/sched_policy/available_sched_policy
performance powersaving balance
$cat /sys/devices/system/cpu/sched_policy/current_sched_policy
powersaving

This means the using sched policy is 'powersaving'.

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

Signed-off-by: Alex Shi <alex.shi@intel.com>
---
Documentation/ABI/testing/sysfs-devices-system-cpu | 24 +++++++
kernel/sched/fair.c | 76 ++++++++++++++++++++++
2 files changed, 100 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 6943133..9c9acbf 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -53,6 +53,30 @@ 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_policy/current_sched_policy
+ /sys/devices/system/cpu/sched_policy/available_sched_policy
+Date: Oct 2012
+Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description: CFS scheduler policy showing and setting interface.
+
+ available_sched_policy shows there are 3 kinds of policy now:
+ performance, balance and powersaving.
+ current_sched_policy shows current scheduler policy. And user
+ can change the policy by writing it.
+
+ Policy decides that CFS scheduler how to distribute tasks onto
+ which CPU unit when tasks number less than LCPU number in system
+
+ performance: try to spread tasks onto more CPU sockets,
+ more CPU cores.
+
+ powersaving: try to shrink tasks onto same core or same CPU
+ until every LCPUs are busy.
+
+ balance: try to shrink tasks onto same core or same CPU
+ until full powered CPUs are busy. This policy also consider
+ system performance when try to save power.
+
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 f24aca6..ee015b8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6102,6 +6102,82 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task

/* The default scheduler policy is 'performance'. */
int __read_mostly sched_policy = SCHED_POLICY_PERFORMANCE;
+
+#ifdef CONFIG_SYSFS
+static ssize_t show_available_sched_policy(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "performance balance powersaving\n");
+}
+
+static ssize_t show_current_sched_policy(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ if (sched_policy == SCHED_POLICY_PERFORMANCE)
+ return sprintf(buf, "performance\n");
+ else if (sched_policy == SCHED_POLICY_POWERSAVING)
+ return sprintf(buf, "powersaving\n");
+ else if (sched_policy == SCHED_POLICY_BALANCE)
+ return sprintf(buf, "balance\n");
+ return 0;
+}
+
+static ssize_t set_sched_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_policy = SCHED_POLICY_PERFORMANCE;
+ else if (!strcmp(str_policy, "powersaving"))
+ sched_policy = SCHED_POLICY_POWERSAVING;
+ else if (!strcmp(str_policy, "balance"))
+ sched_policy = SCHED_POLICY_BALANCE;
+ else
+ return -EINVAL;
+
+ return count;
+}
+
+/*
+ * * Sysfs setup bits:
+ * */
+static DEVICE_ATTR(current_sched_policy, 0644, show_current_sched_policy,
+ set_sched_policy);
+
+static DEVICE_ATTR(available_sched_policy, 0444,
+ show_available_sched_policy, NULL);
+
+static struct attribute *sched_policy_default_attrs[] = {
+ &dev_attr_current_sched_policy.attr,
+ &dev_attr_available_sched_policy.attr,
+ NULL
+};
+static struct attribute_group sched_policy_attr_group = {
+ .attrs = sched_policy_default_attrs,
+ .name = "sched_policy",
+};
+
+int __init create_sysfs_sched_policy_group(struct device *dev)
+{
+ return sysfs_create_group(&dev->kobj, &sched_policy_attr_group);
+}
+
+static int __init sched_policy_sysfs_init(void)
+{
+ return create_sysfs_sched_policy_group(cpu_subsys.dev_root);
+}
+
+core_initcall(sched_policy_sysfs_init);
+#endif /* CONFIG_SYSFS */
+
/*
* All the scheduling class methods:
*/
--
1.7.12


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