Merge "sched: Consider PF_WAKE_UP_IDLE in select_best_cpu()"

This is a per-cpu parameter. If non-zero for a cpu which is part of a cluster

and cluster current frequency is less than this threshold, then scheduler will

poack all tasks on a single cpu in cluster. The cpu chosen is the first most

pack all tasks on a single cpu in cluster. The cpu chosen is the first most

power-efficient cpu found while scanning cluster's online cpus.

- PF_WAKE_UP_IDLE

	Any task that has this flag set in its 'task_struct.flags' field will be

always woken to idle cpu. Further any task woken by such tasks will be also

placed on idle cpu.

For some low band of frequency, spread of task on all available cpus can be

groslly power-inefficient. As an example, consider two tasks that each need

500MHz. Packing them on one cpu could lead to 1GHz. In spread case, we incur

	return target;

}

/*

 * Should task be woken to any available idle cpu?

 *

 * Waking tasks to idle cpu has mixed implications on both performance and

 * power. In many cases, scheduler can't estimate correctly impact of using idle

 * cpus on either performance or power. PF_WAKE_UP_IDLE allows external kernel

 * module to pass a strong hint to scheduler that the task in question should be

 * woken to idle cpu, generally to improve performance.

 */

static inline int wake_to_idle(struct task_struct *p)

{

	return (current->flags & PF_WAKE_UP_IDLE) ||

			 (p->flags & PF_WAKE_UP_IDLE);

}

/* return cheapest cpu that can fit this task */

static int select_best_cpu(struct task_struct *p, int target, int reason,

	int cstate, min_cstate = INT_MAX;

	int prefer_idle = reason ? 1 : sysctl_sched_prefer_idle;

	int curr_cpu = smp_processor_id();

	int prefer_idle_override = 0;

	if (wake_to_idle(p)) {

		prefer_idle = 1;

		prefer_idle_override = 1;

		small_task = 0;

	}

	trace_sched_task_load(p, small_task, boost, reason, sync, prefer_idle);

			best_cpu = fallback_idle_cpu;

	}

	if (cpu_rq(best_cpu)->mostly_idle_freq)

	if (cpu_rq(best_cpu)->mostly_idle_freq && !prefer_idle_override)

		best_cpu = select_packing_target(p, best_cpu);

	return best_cpu;