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Commit 926b2e98 authored by Brendan Jackman's avatar Brendan Jackman Committed by Chris Redpath
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UPSTREAM: sched/fair: Move select_task_rq_fair() slow-path into its own function 



In preparation for changes that would otherwise require adding a new
level of indentation to the while(sd) loop, create a new function
find_idlest_cpu() which contains this loop, and rename the existing
find_idlest_cpu() to find_idlest_group_cpu().

Code inside the while(sd) loop is unchanged. @new_cpu is added as a
variable in the new function, with the same initial value as the
@new_cpu in select_task_rq_fair().

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarBrendan Jackman <brendan.jackman@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
Reviewed-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20171005114516.18617-2-brendan.jackman@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Change-Id: Ic94a5165e85b6ae254b36cd7891001a45b5be756
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
parent 8e3019ac

kernel/sched/fair.c

+48 −35
Original line number Diff line number Diff line
@@ -5942,10 +5942,10 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, 
}



/*

 * find_idlest_cpu - find the idlest cpu among the cpus in group.

 * find_idlest_group_cpu - find the idlest cpu among the cpus in group.

 */

static int

find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)

find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)

{

	unsigned long load, min_load = ULONG_MAX;

	unsigned int min_exit_latency = UINT_MAX;
@@ -5994,6 +5994,50 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 
	return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;

}



static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p,

				  int cpu, int prev_cpu, int sd_flag)

{

	int new_cpu = prev_cpu;



	while (sd) {

		struct sched_group *group;

		struct sched_domain *tmp;

		int weight;



		if (!(sd->flags & sd_flag)) {

			sd = sd->child;

			continue;

		}



		group = find_idlest_group(sd, p, cpu, sd_flag);

		if (!group) {

			sd = sd->child;

			continue;

		}



		new_cpu = find_idlest_group_cpu(group, p, cpu);

		if (new_cpu == -1 || new_cpu == cpu) {

			/* Now try balancing at a lower domain level of cpu */

			sd = sd->child;

			continue;

		}



		/* Now try balancing at a lower domain level of new_cpu */

		cpu = new_cpu;

		weight = sd->span_weight;

		sd = NULL;

		for_each_domain(cpu, tmp) {

			if (weight <= tmp->span_weight)

				break;

			if (tmp->flags & sd_flag)

				sd = tmp;

		}

		/* while loop will break here if sd == NULL */

	}



	return new_cpu;

}



#ifdef CONFIG_SCHED_SMT



static inline void set_idle_cores(int cpu, int val)
@@ -6385,39 +6429,8 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f 
		if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */

			new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);



	} else while (sd) {

		struct sched_group *group;

		int weight;



		if (!(sd->flags & sd_flag)) {

			sd = sd->child;

			continue;

		}



		group = find_idlest_group(sd, p, cpu, sd_flag);

		if (!group) {

			sd = sd->child;

			continue;

		}



		new_cpu = find_idlest_cpu(group, p, cpu);

		if (new_cpu == -1 || new_cpu == cpu) {

			/* Now try balancing at a lower domain level of cpu */

			sd = sd->child;

			continue;

		}



		/* Now try balancing at a lower domain level of new_cpu */

		cpu = new_cpu;

		weight = sd->span_weight;

		sd = NULL;

		for_each_domain(cpu, tmp) {

			if (weight <= tmp->span_weight)

				break;

			if (tmp->flags & sd_flag)

				sd = tmp;

		}

		/* while loop will break here if sd == NULL */

	} else {

		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);

	}



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