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Commit 931bd823 authored by Morten Rasmussen's avatar Morten Rasmussen Committed by Dmitry Shmidt
Browse files

ANDROID: sched: Estimate energy impact of scheduling decisions 



Adds a generic energy-aware helper function, energy_diff(), that
calculates energy impact of adding, removing, and migrating utilization
in the system.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarAndres Oportus <andresoportus@google.com>
parent a455fa7b

kernel/sched/fair.c

+52 −0
Original line number Diff line number Diff line
@@ -5346,6 +5346,58 @@ static int sched_group_energy(struct energy_env *eenv) 
	return 0;

}



static inline bool cpu_in_sg(struct sched_group *sg, int cpu)

{

	return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));

}



/*

 * energy_diff(): Estimate the energy impact of changing the utilization

 * distribution. eenv specifies the change: utilisation amount, source, and

 * destination cpu. Source or destination cpu may be -1 in which case the

 * utilization is removed from or added to the system (e.g. task wake-up). If

 * both are specified, the utilization is migrated.

 */

static int energy_diff(struct energy_env *eenv)

{

	struct sched_domain *sd;

	struct sched_group *sg;

	int sd_cpu = -1, energy_before = 0, energy_after = 0;



	struct energy_env eenv_before = {

		.util_delta	= 0,

		.src_cpu	= eenv->src_cpu,

		.dst_cpu	= eenv->dst_cpu,

	};



	if (eenv->src_cpu == eenv->dst_cpu)

		return 0;



	sd_cpu = (eenv->src_cpu != -1) ? eenv->src_cpu : eenv->dst_cpu;

	sd = rcu_dereference(per_cpu(sd_ea, sd_cpu));



	if (!sd)

		return 0; /* Error */



	sg = sd->groups;



	do {

		if (cpu_in_sg(sg, eenv->src_cpu) || cpu_in_sg(sg, eenv->dst_cpu)) {

			eenv_before.sg_top = eenv->sg_top = sg;



			if (sched_group_energy(&eenv_before))

				return 0; /* Invalid result abort */

			energy_before += eenv_before.energy;



			if (sched_group_energy(eenv))

				return 0; /* Invalid result abort */

			energy_after += eenv->energy;

		}

	} while (sg = sg->next, sg != sd->groups);



	return energy_after-energy_before;

}



/*

 * Detect M:N waker/wakee relationships via a switching-frequency heuristic.

 *