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Commit 79e3a4a2 authored by Chris Redpath's avatar Chris Redpath Committed by Quentin Perret
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ANDROID: sched: Unconditionally honor sync flag for energy-aware wakeups 



Since we don't do energy-aware wakeups when we are overutilized, always
honoring sync wakeups in this state does not prevent wake-wide mechanics
overruling the flag as normal.

This patch is based upon previous work to build EAS for android products.

sync-hint code taken from commit 4a5e890ec60d
"sched/fair: add tunable to force selection at cpu granularity" written
by Juri Lelli <juri.lelli@arm.com>

Change-Id: I4b3d79141fc8e53dc51cd63ac11096c2e3cb10f5
Signed-off-by: default avatarChris Redpath <chris.redpath@arm.com>
(cherry-picked from commit f1ec666a62dec1083ed52fe1ddef093b84373aaf)
[ Moved the feature to find_energy_efficient_cpu() and removed the
  sysctl knob ]
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>
parent b61876ed

kernel/sched/fair.c

+8 −2
Original line number Diff line number Diff line
@@ -6336,7 +6336,7 @@ compute_energy(struct task_struct *p, int dst_cpu, struct perf_domain *pd) 
 * other use-cases too. So, until someone finds a better way to solve this,

 * let's keep things simple by re-using the existing slow path.

 */

static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)

static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu, int sync)

{

	unsigned long prev_delta = ULONG_MAX, best_delta = ULONG_MAX;

	struct root_domain *rd = cpu_rq(smp_processor_id())->rd;
@@ -6350,6 +6350,12 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) 
	if (!pd || READ_ONCE(rd->overutilized))

		goto fail;



	cpu = smp_processor_id();

	if (sync && cpumask_test_cpu(cpu, p->cpus_ptr)) {

		rcu_read_unlock();

		return cpu;

	}



	/*

	 * Energy-aware wake-up happens on the lowest sched_domain starting

	 * from sd_asym_cpucapacity spanning over this_cpu and prev_cpu.
@@ -6461,7 +6467,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f 
		record_wakee(p);



		if (sched_energy_enabled()) {

			new_cpu = find_energy_efficient_cpu(p, prev_cpu);

			new_cpu = find_energy_efficient_cpu(p, prev_cpu, sync);

			if (new_cpu >= 0)

				return new_cpu;

			new_cpu = prev_cpu;