Re: [PATCH v3 14/22] sched: add sched_policy and it's sysfs interface

[Namhyung Kim <namhyung@kernel.org>]

Hi Alex,

Just a few nitpickings..


On Sat,  5 Jan 2013 16:37:43 +0800, Alex Shi wrote:
> 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)

This line can be combined to the above line.


> +{
> +	return sprintf(buf, "performance balance powersaving\n");
> +}
> +
> +static ssize_t show_current_sched_policy(struct device *dev,
> +		struct device_attribute *attr,
> +		char *buf)

Ditto.


> +{
> +	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:
> + *   */

Unneeded asterisks.

Thanks,
Namhyung


> +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:
>   */