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Commit 88a968ca authored by Ionela Voinescu's avatar Ionela Voinescu Committed by Quentin Perret
Browse files

sched/fair: use min capacity when evaluating idle backup cpus 



When we are calculating what the impact of placing a task on a specific
cpu is, we should include the information that there might be a minimum
capacity imposed upon that cpu which could change the performance and/or
energy cost decisions.

When choosing an idle backup CPU, favour CPUs that won't end up
running at a high OPP due to a min capacity cap imposed by external
actors.

Change-Id: I566623ffb3a7c5b61a23242dcce1cb4147ef8a4a
Signed-off-by: default avatarIonela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
parent 9e1c648c

kernel/sched/fair.c

+20 −1
Original line number Diff line number Diff line
@@ -6711,6 +6711,7 @@ static inline int find_best_target(struct task_struct *p, int *backup_cpu, 
	unsigned long target_max_spare_cap = 0;

	unsigned long target_util = ULONG_MAX;

	unsigned long best_active_util = ULONG_MAX;

	unsigned long target_idle_max_spare_cap = 0;

	int best_idle_cstate = INT_MAX;

	struct sched_domain *sd;

	struct sched_group *sg;
@@ -6746,7 +6747,7 @@ static inline int find_best_target(struct task_struct *p, int *backup_cpu, 
		for_each_cpu_and(i, tsk_cpus_allowed(p), sched_group_cpus(sg)) {

			unsigned long capacity_curr = capacity_curr_of(i);

			unsigned long capacity_orig = capacity_orig_of(i);

			unsigned long wake_util, new_util;

			unsigned long wake_util, new_util, min_capped_util;



			if (!cpu_online(i))

				continue;
@@ -6768,6 +6769,16 @@ static inline int find_best_target(struct task_struct *p, int *backup_cpu, 
			 * than the one required to boost the task.

			 */

			new_util = max(min_util, new_util);



			/*

			 * Include minimum capacity constraint:

			 * new_util contains the required utilization including

			 * boost. min_capped_util also takes into account a

			 * minimum capacity cap imposed on the CPU by external

			 * actors.

			 */

			min_capped_util = max(new_util, capacity_min_of(i));



			if (new_util > capacity_orig)

				continue;
@@ -6890,6 +6901,12 @@ static inline int find_best_target(struct task_struct *p, int *backup_cpu, 
				/* Select idle CPU with lower cap_orig */

				if (capacity_orig > best_idle_min_cap_orig)

					continue;

				/* Favor CPUs that won't end up running at a

				 * high OPP.

				 */

				if ((capacity_orig - min_capped_util) <

					target_idle_max_spare_cap)

					continue;



				/*

				 * Skip CPUs in deeper idle state, but only
@@ -6903,6 +6920,8 @@ static inline int find_best_target(struct task_struct *p, int *backup_cpu, 


				/* Keep track of best idle CPU */

				best_idle_min_cap_orig = capacity_orig;

				target_idle_max_spare_cap = capacity_orig -

							    min_capped_util;

				best_idle_cstate = idle_idx;

				best_idle_cpu = i;

				continue;