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Commit 92819a68 authored by Morten Rasmussen's avatar Morten Rasmussen Committed by Quentin Perret
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UPSTREAM: sched/fair: Add sched_group per-CPU max capacity 



The current sg->min_capacity tracks the lowest per-CPU compute capacity
available in the sched_group when rt/irq pressure is taken into account.
Minimum capacity isn't the ideal metric for tracking if a sched_group
needs offloading to another sched_group for some scenarios, e.g. a
sched_group with multiple CPUs if only one is under heavy pressure.
Tracking maximum capacity isn't perfect either but a better choice for
some situations as it indicates that the sched_group definitely compute
capacity constrained either due to rt/irq pressure on all CPUs or
asymmetric CPU capacities (e.g. big.LITTLE).

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: gaku.inami.xh@renesas.com
Cc: valentin.schneider@arm.com
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/1530699470-29808-4-git-send-email-morten.rasmussen@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
(cherry picked from commit e3d6d0cb66f2351cbfd09fbae04eb9804afe9577)
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>

Change-Id: I56324d1543d8d0d052a66cd94c7f8e5083bd9c28
parent bca5744a

kernel/sched/fair.c

+20 −4
Original line number Diff line number Diff line
@@ -7651,13 +7651,14 @@ 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;

	sdg->sgc->max_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, min_capacity;

	unsigned long capacity, min_capacity, max_capacity;

	unsigned long interval;



	interval = msecs_to_jiffies(sd->balance_interval);
@@ -7671,6 +7672,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 


	capacity = 0;

	min_capacity = ULONG_MAX;

	max_capacity = 0;



	if (child->flags & SD_OVERLAP) {

		/*
@@ -7701,6 +7703,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu) 
			}



			min_capacity = min(capacity, min_capacity);

			max_capacity = max(capacity, max_capacity);

		}

	} else  {

		/*
@@ -7714,12 +7717,14 @@ 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;

}



/*
@@ -7815,16 +7820,27 @@ group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) 
}



/*

 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller

 * group_smaller_min_cpu_capacity: Returns true if sched_group sg has smaller

 * per-CPU capacity than sched_group ref.

 */

static inline bool

group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref)

group_smaller_min_cpu_capacity(struct sched_group *sg, struct sched_group *ref)

{

	return sg->sgc->min_capacity * capacity_margin <

						ref->sgc->min_capacity * 1024;

}



/*

 * group_smaller_max_cpu_capacity: Returns true if sched_group sg has smaller

 * per-CPU capacity_orig than sched_group ref.

 */

static inline bool

group_smaller_max_cpu_capacity(struct sched_group *sg, struct sched_group *ref)

{

	return sg->sgc->max_capacity * capacity_margin <

						ref->sgc->max_capacity * 1024;

}



static inline enum

group_type group_classify(struct sched_group *group,

			  struct sg_lb_stats *sgs)
@@ -7970,7 +7986,7 @@ static bool update_sd_pick_busiest(struct lb_env *env, 
	 * power/energy consequences are not considered.

	 */

	if (sgs->sum_nr_running <= sgs->group_weight &&

	    group_smaller_cpu_capacity(sds->local, sg))

	    group_smaller_min_cpu_capacity(sds->local, sg))

		return false;



asym_packing:

kernel/sched/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1200,6 +1200,7 @@ 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

+2 −0
Original line number Diff line number Diff line
@@ -693,6 +693,7 @@ 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
@@ -852,6 +853,7 @@ static struct sched_group *get_group(int cpu, struct sd_data *sdd) 


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

	sg->sgc->min_capacity = SCHED_CAPACITY_SCALE;

	sg->sgc->max_capacity = SCHED_CAPACITY_SCALE;



	return sg;

}