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Commit 369bcbba authored by Todd Kjos's avatar Todd Kjos Committed by John Stultz
Browse files

sched/fair: optimize idle cpu selection for boosted tasks 

find_best_target CPU selection is biased towards lower CPU IDs. Bias
towards higher CPUs for boosted tasks. For boosted tasks unconditionally
use the idle CPU returned by find_best_target.

BUG: 29512132
Change-Id: I3d650051752163fcf3dc7909751d1fde3f9d17c0

Conflicts:
	kernel/sched/fair.c
parent af14760e

kernel/sched/fair.c

+36 −34
Original line number Diff line number Diff line
@@ -5569,32 +5569,30 @@ done: 
	return target;

}



static inline int find_best_target(struct task_struct *p)

static inline int find_best_target(struct task_struct *p, bool boosted)

{

	int i, boosted;

	int iter_cpu;

	int target_cpu = -1;

	int target_capacity = 0;

	int backup_capacity = 0;

	int idle_cpu = -1;

	int best_idle_cpu = -1;

	int best_idle_cstate = INT_MAX;

	int backup_cpu = -1;

	unsigned long task_util_boosted, new_util;



	task_util_boosted = boosted_task_util(p);

	for (iter_cpu = 0; iter_cpu < NR_CPUS; iter_cpu++) {

		int cur_capacity;

		struct rq *rq;

		int idle_idx;



		/*

	 * Favor 1) busy cpu with most capacity at current OPP

	 *       2) idle_cpu with capacity at current OPP

	 *       3) busy cpu with capacity at higher OPP

		 * favor higher cpus for boosted tasks

		 */

#ifdef CONFIG_CGROUP_SCHEDTUNE

	boosted = schedtune_task_boost(p);

#else

	boosted = 0;

#endif

	task_util_boosted = boosted_task_util(p);

	for_each_cpu(i, tsk_cpus_allowed(p)) {

		int cur_capacity = capacity_curr_of(i);

		struct rq *rq = cpu_rq(i);

		int idle_idx = idle_get_state_idx(rq);

		int i = boosted ? NR_CPUS-iter_cpu-1 : iter_cpu;



		if (!cpu_online(i) || !cpumask_test_cpu(i, tsk_cpus_allowed(p)))

			continue;



		/*

		 * p's blocked utilization is still accounted for on prev_cpu
@@ -5615,46 +5613,43 @@ static inline int find_best_target(struct task_struct *p) 
		 * For boosted tasks we favor idle cpus unconditionally to

		 * improve latency.

		 */

		if (idle_idx >= 0 && boosted) {

			if (idle_cpu < 0 ||

				(sysctl_sched_cstate_aware &&

				 best_idle_cstate > idle_idx)) {

				best_idle_cstate = idle_idx;

				idle_cpu = i;

			}

		if (idle_cpu(i) && boosted) {

			if (best_idle_cpu < 0)

				best_idle_cpu = i;

			continue;

		}



		cur_capacity = capacity_curr_of(i);

		rq = cpu_rq(i);

		idle_idx = idle_get_state_idx(rq);



		if (new_util < cur_capacity) {

			if (cpu_rq(i)->nr_running) {

				if (target_capacity == 0 ||

					target_capacity > cur_capacity) {

					/* busy CPU with most capacity at current OPP */

					target_cpu = i;

					target_capacity = cur_capacity;

				}

			} else if (!boosted) {

				if (idle_cpu < 0 ||

				if (best_idle_cpu < 0 ||

					(sysctl_sched_cstate_aware &&

						best_idle_cstate > idle_idx)) {

					best_idle_cstate = idle_idx;

					idle_cpu = i;

					best_idle_cpu = i;

				}

			}

		} else if (backup_capacity == 0 ||

				backup_capacity > cur_capacity) {

			/* first busy CPU with capacity at higher OPP */

			backup_capacity = cur_capacity;

			backup_cpu = i;

		}

	}



	if (!boosted && target_cpu < 0) {

		target_cpu = idle_cpu >= 0 ? idle_cpu : backup_cpu;

	}

	if (boosted && best_idle_cpu >= 0)

		target_cpu = best_idle_cpu;

	else if (target_cpu < 0)

		target_cpu = best_idle_cpu >= 0 ? best_idle_cpu : backup_cpu;



	if (boosted && idle_cpu >= 0)

		target_cpu = idle_cpu;

	return target_cpu;

}
@@ -5740,9 +5735,16 @@ static int energy_aware_wake_cpu(struct task_struct *p, int target, int sync) 
		/*

		 * Find a cpu with sufficient capacity

		 */

		int tmp_target = find_best_target(p);

#ifdef CONFIG_CGROUP_SCHEDTUNE

		bool boosted = schedtune_task_boost(p) > 0;

#else

		bool boosted = 0;

#endif

		int tmp_target = find_best_target(p, boosted);

		if (tmp_target >= 0)

			target_cpu = tmp_target;

			if (boosted && idle_cpu(target_cpu))

				return target_cpu;

	}



	if (target_cpu != task_cpu(p)) {