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Commit 88d06052 authored by Patrick Bellasi's avatar Patrick Bellasi Committed by Dmitry Shmidt
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ANDROID: sched/fair: filter energy_diff() based on energy_payoff value 



Once the SchedTune support is enabled and the CPU bandwidth demand of a
task is boosted, we could expect increased energy consumptions which are
balanced by corresponding increases of tasks performance.
However, the current implementation of the energy_diff() function
accepts all and _only_ the schedule candidates which results into a
reduced expected system energy, which works against the boosting
strategy.

This patch links the energy_diff() function with the "energy payoff"
engine provided by SchedTune. The energy variation computed by the
energy_diff() function is now filtered using the SchedTune support to
evaluated the energy payoff for a boosted task.

With that patch, the energy_diff() function is going to reported as
"acceptable schedule candidate" only the schedule candidate which
corresponds to a positive energy_payoff.

Signed-off-by: default avatarPatrick Bellasi <patrick.bellasi@arm.com>
Signed-off-by: default avatarAndres Oportus <andresoportus@google.com>
parent 2f369bb2

kernel/sched/fair.c

+45 −2
Original line number Diff line number Diff line
@@ -5161,9 +5161,12 @@ struct energy_env { 
	int			src_cpu;

	int			dst_cpu;

	int			energy;

	int			payoff;

	struct task_struct	*task;

	struct {

		int before;

		int after;

		int delta;

		int diff;

	} nrg;

	struct {
@@ -5384,6 +5387,44 @@ static inline bool cpu_in_sg(struct sched_group *sg, int cpu) 
	return cpu != -1 && cpumask_test_cpu(cpu, sched_group_cpus(sg));

}



#ifdef CONFIG_SCHED_TUNE

static int energy_diff_evaluate(struct energy_env *eenv)

{

	unsigned int boost;

	int nrg_delta;



	/* Return energy diff when boost margin is 0 */

#ifdef CONFIG_CGROUP_SCHEDTUNE

	boost = schedtune_task_boost(eenv->task);

#else

	boost = get_sysctl_sched_cfs_boost();

#endif

	if (boost == 0)

		return eenv->nrg.diff;



	/* Compute normalized energy diff */

	nrg_delta = schedtune_normalize_energy(eenv->nrg.diff);

	eenv->nrg.delta = nrg_delta;



	eenv->payoff = schedtune_accept_deltas(

			eenv->nrg.delta,

			eenv->cap.delta,

			eenv->task);



	/*

	 * When SchedTune is enabled, the energy_diff() function will return

	 * the computed energy payoff value. Since the energy_diff() return

	 * value is expected to be negative by its callers, this evaluation

	 * function return a negative value each time the evaluation return a

	 * positive payoff, which is the condition for the acceptance of

	 * a scheduling decision

	 */

	return -eenv->payoff;

}

#else /* CONFIG_SCHED_TUNE */

#define energy_diff_evaluate(eenv) eenv->nrg.diff

#endif



/*

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

 * distribution. eenv specifies the change: utilisation amount, source, and
@@ -5401,7 +5442,7 @@ static int energy_diff(struct energy_env *eenv) 
		.util_delta	= 0,

		.src_cpu	= eenv->src_cpu,

		.dst_cpu	= eenv->dst_cpu,

		.nrg		= { 0, 0, 0 },

		.nrg		= { 0, 0, 0, 0},

		.cap		= { 0, 0, 0 },

	};
@@ -5437,8 +5478,9 @@ static int energy_diff(struct energy_env *eenv) 
	eenv->nrg.before = energy_before;

	eenv->nrg.after = energy_after;

	eenv->nrg.diff = eenv->nrg.after - eenv->nrg.before;

	eenv->payoff = 0;



	return eenv->nrg.diff;

	return energy_diff_evaluate(eenv);

}



/*
@@ -6138,6 +6180,7 @@ static int energy_aware_wake_cpu(struct task_struct *p, int target) 
			.util_delta	= task_util(p),

			.src_cpu	= task_cpu(p),

			.dst_cpu	= target_cpu,

			.task		= p,

		};



		/* Not enough spare capacity on previous cpu */