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Commit fd3fc28d authored by Morten Rasmussen's avatar Morten Rasmussen Committed by Chris Redpath
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ANDROID: sched: Add per-cpu max capacity to sched_group_capacity 



struct sched_group_capacity currently represents the compute capacity
sum of all cpus in the sched_group. Unless it is divided by the
group_weight to get the average capacity per cpu it hides differences in
cpu capacity for mixed capacity systems (e.g. high RT/IRQ utilization or
ARM big.LITTLE). But even the average may not be sufficient if the group
covers cpus of different capacities. Instead, by extending struct
sched_group_capacity to indicate max per-cpu capacity in the group a
suitable group for a given task utilization can easily be found such
that cpus with reduced capacity can be avoided for tasks with high
utilization (not implemented by this patch).

Change-Id: I728335d721d14e0b1b1921cbf73734c9f75b9bf6
Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
parent f1f7125e

kernel/sched/fair.c

+5 −1
Original line number Diff line number Diff line
@@ -7722,7 +7722,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 
{

	struct sched_domain *child = sd->child;

	struct sched_group *group, *sdg = sd->groups;

	unsigned long capacity, min_capacity;

	unsigned long capacity, min_capacity, max_capacity;

	unsigned long interval;



	interval = msecs_to_jiffies(sd->balance_interval);
@@ -7736,6 +7736,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 


	capacity = 0;

	min_capacity = ULONG_MAX;

	max_capacity = 0;



	if (child->flags & SD_OVERLAP) {

		/*
@@ -7766,6 +7767,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 
			}



			min_capacity = min(capacity, min_capacity);

			max_capacity = max(capacity, max_capacity);

		}

	} else  {

		/*
@@ -7779,12 +7781,14 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 


			capacity += sgc->capacity;

			min_capacity = min(sgc->min_capacity, min_capacity);

			max_capacity = max(sgc->max_capacity, max_capacity);

			group = group->next;

		} while (group != child->groups);

	}



	sdg->sgc->capacity = capacity;

	sdg->sgc->min_capacity = min_capacity;

	sdg->sgc->max_capacity = max_capacity;

}



/*

kernel/sched/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1073,6 +1073,7 @@ struct sched_group_capacity { 
	 */

	unsigned long capacity;

	unsigned long min_capacity; /* Min per-CPU capacity in group */

	unsigned long max_capacity; /* Max per-CPU capacity in group */

	unsigned long next_update;

	int imbalance; /* XXX unrelated to capacity but shared group state */

kernel/sched/topology.c

+1 −0
Original line number Diff line number Diff line
@@ -716,6 +716,7 @@ static void init_overlap_sched_group(struct sched_domain *sd, 
	sg_span = sched_group_span(sg);

	sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);

	sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;

	sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;

}



static int