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Commit bf475ce0 authored by Morten Rasmussen's avatar Morten Rasmussen Committed by Ingo Molnar
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sched/fair: Add per-CPU min 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 min per-CPU
capacity in the group a suitable group for a given task utilization can
more easily be found such that CPUs with reduced capacity can be avoided
for tasks with high utilization (not implemented by this patch).

Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: freedom.tan@mediatek.com
Cc: keita.kobayashi.ym@renesas.com
Cc: mgalbraith@suse.de
Cc: sgurrappadi@nvidia.com
Cc: vincent.guittot@linaro.org
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/1476452472-24740-4-git-send-email-morten.rasmussen@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 6a0b19c0

kernel/sched/core.c

+2 −1
Original line number Diff line number Diff line
@@ -5708,7 +5708,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level, 
		printk(KERN_CONT " %*pbl",

		       cpumask_pr_args(sched_group_cpus(group)));

		if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {

			printk(KERN_CONT " (cpu_capacity = %d)",

			printk(KERN_CONT " (cpu_capacity = %lu)",

				group->sgc->capacity);

		}
@@ -6185,6 +6185,7 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu) 
		 * die on a /0 trap.

		 */

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

		sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;



		/*

		 * Make sure the first group of this domain contains the

kernel/sched/fair.c

+12 −5
Original line number Diff line number Diff line
@@ -6909,13 +6909,14 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) 


	cpu_rq(cpu)->cpu_capacity = capacity;

	sdg->sgc->capacity = capacity;

	sdg->sgc->min_capacity = capacity;

}



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;

	unsigned long capacity, min_capacity;

	unsigned long interval;



	interval = msecs_to_jiffies(sd->balance_interval);
@@ -6928,6 +6929,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 
	}



	capacity = 0;

	min_capacity = ULONG_MAX;



	if (child->flags & SD_OVERLAP) {

		/*
@@ -6952,12 +6954,13 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 
			 */

			if (unlikely(!rq->sd)) {

				capacity += capacity_of(cpu);

				continue;

			}



			} else {

				sgc = rq->sd->groups->sgc;

				capacity += sgc->capacity;

			}



			min_capacity = min(capacity, min_capacity);

		}

	} else  {

		/*

		 * !SD_OVERLAP domains can assume that child groups
@@ -6966,12 +6969,16 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 


		group = child->groups;

		do {

			capacity += group->sgc->capacity;

			struct sched_group_capacity *sgc = group->sgc;



			capacity += sgc->capacity;

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

			group = group->next;

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

	}



	sdg->sgc->capacity = capacity;

	sdg->sgc->min_capacity = min_capacity;

}



/*

kernel/sched/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -892,7 +892,8 @@ struct sched_group_capacity { 
	 * CPU capacity of this group, SCHED_CAPACITY_SCALE being max capacity

	 * for a single CPU.

	 */

	unsigned int capacity;

	unsigned long capacity;

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

	unsigned long next_update;

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