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    Subject[patch v6 05/21] sched: add sysfs interface for sched_balance_policy selection
    Date
    This patch add the power aware scheduler knob into sysfs:

    $cat /sys/devices/system/cpu/sched_balance_policy/available_sched_balance_policy
    performance powersaving
    $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 | 22 +++++++
    kernel/sched/fair.c | 69 ++++++++++++++++++++++
    2 files changed, 91 insertions(+)

    diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
    index 9c978dc..b602882 100644
    --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
    +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
    @@ -53,6 +53,28 @@ 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 balance policy show and set interface.
    +
    + available_sched_balance_policy: shows there are 2 kinds of
    + policies:
    + performance powersaving.
    + current_sched_balance_policy: shows current scheduler policy.
    + User can change the policy by writing it.
    +
    + Policy decides the CFS scheduler how to balance 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.
    +
    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 61ee178..90106ad 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -6096,6 +6096,75 @@ 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 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");
    + 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
    + 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


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