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Commit 83717be3 authored by Chris Redpath's avatar Chris Redpath
Browse files

ANDROID: refactor select_task_rq_fair et al to be cleaner 



We can move the energy-aware wakeup functionality around
a little and make it clear that it fits into the slow-path
wakeup code. The resulting code is a very close match to
the shape we expect to push upstream for comment.

Change-Id: Icf5a2ae9bdf6db5977240e5a1f1da2ed41e0fad7
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
parent c0ff131c

kernel/sched/fair.c

+46 −23
Original line number Diff line number Diff line
@@ -6637,26 +6637,27 @@ static bool cpu_overutilized(int cpu) 
	return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);

}



static int select_energy_cpu_brute(struct task_struct *p, int prev_cpu, int sync)

/*

 * Needs to be called inside rcu_read_lock critical section.

 * sd is a pointer to the sched domain we wish to use for an

 * energy-aware placement option.

 */

static int find_energy_efficient_cpu(struct sched_domain *sd,

				     struct task_struct *p,

				     int cpu, int prev_cpu,

				     int sync)

{

	int i;

	int min_diff = 0, energy_cpu = prev_cpu, spare_cpu = prev_cpu;

	int energy_cpu = prev_cpu, spare_cpu = prev_cpu;

	unsigned long max_spare = 0;

	struct sched_domain *sd;

	int min_diff = 0;

	int i;



	if (sysctl_sched_sync_hint_enable && sync) {

		int cpu = smp_processor_id();



		if (cpumask_test_cpu(cpu, &p->cpus_allowed)) {

			return cpu;

		}

	}



	sd = rcu_dereference(per_cpu(sd_ea, prev_cpu));



	if (!sd)

		goto unlock;



	for_each_cpu_and(i, &p->cpus_allowed, sched_domain_span(sd)) {

		int diff;

		unsigned long spare;
@@ -6689,7 +6690,6 @@ static int select_energy_cpu_brute(struct task_struct *p, int prev_cpu, int sync 
		}

	}



unlock:

	if (energy_cpu == prev_cpu && !cpu_overutilized(prev_cpu))

		return prev_cpu;
@@ -6729,6 +6729,14 @@ static inline int wake_energy(struct task_struct *p, int prev_cpu, 
	if (sd_overutilized(sd))

		return false;



	/*

	 * we cannot do energy-aware wakeup placement sensibly

	 * for tasks with 0 utilization, so let them be placed

	 * according to the normal strategy.

	 */

	if (unlikely(!task_util(p)))

		return false;



	if(!sched_feat(EAS_PREFER_IDLE)){

		/*

		 * Force prefer-idle tasks into the slow path, this may not happen
@@ -6756,23 +6764,23 @@ static int 
select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags,

		    int sibling_count_hint)

{

	struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;

	struct sched_domain *tmp, *affine_sd = NULL;

	struct sched_domain *sd = NULL, *energy_sd = NULL;

	int cpu = smp_processor_id();

	int new_cpu = prev_cpu;

	int want_affine = 0;

	int want_energy = 0;

	int sync = wake_flags & WF_SYNC;



	rcu_read_lock();



	if (sd_flag & SD_BALANCE_WAKE) {

		record_wakee(p);

		want_affine = !wake_wide(p, sibling_count_hint) && !wake_cap(p, cpu, prev_cpu)

			      && cpumask_test_cpu(cpu, &p->cpus_allowed);

	}



	if (wake_energy(p, prev_cpu, sd_flag, wake_flags)) {

		new_cpu = select_energy_cpu_brute(p, prev_cpu, sync);

		goto unlock;

		want_energy = wake_energy(p, prev_cpu, sd_flag, wake_flags);

		want_affine = !want_energy &&

			      !wake_wide(p, sibling_count_hint) &&

			      !wake_cap(p, cpu, prev_cpu) &&

			      cpumask_test_cpu(cpu, &p->cpus_allowed);

	}



	for_each_domain(cpu, tmp) {
@@ -6789,9 +6797,22 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f 
			break;

		}



		/*

		 * If we are able to try an energy-aware wakeup,

		 * select the highest non-overutilized sched domain

		 * which includes this cpu and prev_cpu

		 *

		 * maybe want to not test prev_cpu and only consider

		 * the current one?

		 */

		if (want_energy &&

		    !sd_overutilized(tmp) &&

		    cpumask_test_cpu(prev_cpu, sched_domain_span(tmp)))

			energy_sd = tmp;



		if (tmp->flags & sd_flag)

			sd = tmp;

		else if (!want_affine)

		else if (!(want_affine || want_energy))

			break;

	}
@@ -6819,10 +6840,12 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f 
			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);



	} else {

		if (energy_sd)

			new_cpu = find_energy_efficient_cpu(energy_sd, p, cpu, prev_cpu, sync);

		else

			new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);

	}



unlock:

	rcu_read_unlock();



#ifdef CONFIG_NO_HZ_COMMON