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Commit 6d973a43 authored by Olav Haugan's avatar Olav Haugan Committed by Gerrit - the friendly Code Review server
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sched/fair: Add irq load awareness to the tick CPU selection logic 



IRQ load is not taken into account when determining whether a task
should be migrated to a different CPU.  A task that runs for a long time
could get stuck on CPU with high IRQ load causing degraded performance.

Add irq load awareness to the tick CPU selection logic.

CRs-fixed: 809119
Change-Id: I7969f7dd947fb5d66fce0bedbc212bfb2d42c8c1
Signed-off-by: default avatarOlav Haugan <ohaugan@codeaurora.org>
parent 13e54426

kernel/sched/fair.c

+18 −10
Original line number Diff line number Diff line
@@ -1906,9 +1906,10 @@ static int best_small_task_cpu(struct task_struct *p, int sync) 
	return best_fallback_cpu;

}



#define MOVE_TO_BIG_CPU			1

#define MOVE_TO_LITTLE_CPU		2

#define MOVE_TO_POWER_EFFICIENT_CPU	3

#define UP_MIGRATION		1

#define DOWN_MIGRATION		2

#define EA_MIGRATION		3

#define IRQLOAD_MIGRATION	4



static int skip_cpu(struct task_struct *p, int cpu, int reason)

{
@@ -1923,18 +1924,22 @@ static int skip_cpu(struct task_struct *p, int cpu, int reason) 
		return 1;



	switch (reason) {

	case MOVE_TO_BIG_CPU:

	case UP_MIGRATION:

		skip = (rq->capacity <= task_rq->capacity);

		break;



	case MOVE_TO_LITTLE_CPU:

	case DOWN_MIGRATION:

		skip = (rq->capacity >= task_rq->capacity);

		break;



	case MOVE_TO_POWER_EFFICIENT_CPU:

	case EA_MIGRATION:

		skip = rq->capacity < task_rq->capacity  ||

			power_cost(p, cpu) >  power_cost(p,  task_cpu(p));

		break;



	case IRQLOAD_MIGRATION:

		/* Purposely fall through */



	default:

		skip = (cpu == task_cpu(p));

		break;
@@ -2699,7 +2704,7 @@ static inline int migration_needed(struct rq *rq, struct task_struct *p) 


	if (sched_boost()) {

		if (rq->capacity != max_capacity)

			return MOVE_TO_BIG_CPU;

			return UP_MIGRATION;



		return 0;

	}
@@ -2707,18 +2712,21 @@ static inline int migration_needed(struct rq *rq, struct task_struct *p) 
	if (is_small_task(p))

		return 0;



	if (sched_cpu_high_irqload(cpu_of(rq)))

		return IRQLOAD_MIGRATION;



	if ((nice > sched_upmigrate_min_nice || upmigrate_discouraged(p)) &&

			 rq->capacity > min_capacity)

		return MOVE_TO_LITTLE_CPU;

		return DOWN_MIGRATION;



	if (!task_will_fit(p, cpu_of(rq)))

		return MOVE_TO_BIG_CPU;

		return UP_MIGRATION;



	if (sysctl_sched_enable_power_aware &&

	    !is_task_migration_throttled(p) &&

	    is_cpu_throttling_imminent(cpu_of(rq)) &&

	    lower_power_cpu_available(p, cpu_of(rq)))

		return MOVE_TO_POWER_EFFICIENT_CPU;

		return EA_MIGRATION;



	return 0;

}