Partial Revert: "WIP: sched: Add cpu capacity awareness to wakeup balancing"

Revert the changes in find_idlest_cpu() and find_idlest_group().

Keep the infrastructure bits which are used in following EAS patches.

Change-Id: Id516ca5f3e51b9a13db1ebb8de2df3aa25f9679b
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>

1 files changed, 3 insertions, 31 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 12bb2ae026f5..2150edce955a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5384,11 +5384,6 @@ static inline bool task_fits_max(struct task_struct *p, int cpu)
 	return __task_fits(p, cpu, 0);
 }
 
-static inline bool task_fits_spare(struct task_struct *p, int cpu)
-{
-	return __task_fits(p, cpu, cpu_util(cpu));
-}
-
 static bool cpu_overutilized(int cpu)
 {
 	return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
@@ -5509,9 +5504,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
 		  int this_cpu, int sd_flag)
 {
 	struct sched_group *idlest = NULL, *group = sd->groups;
-	struct sched_group *fit_group = NULL;
 	unsigned long min_load = ULONG_MAX, this_load = 0;
-	unsigned long fit_capacity = ULONG_MAX;
 	int load_idx = sd->forkexec_idx;
 	int imbalance = 100 + (sd->imbalance_pct-100)/2;
 
@@ -5542,15 +5535,6 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
 				load = target_load(i, load_idx);
 
 			avg_load += load;
-
-			/*
-			 * Look for most energy-efficient group that can fit
-			 * that can fit the task.
-			 */
-			if (capacity_of(i) < fit_capacity && task_fits_spare(p, i)) {
-				fit_capacity = capacity_of(i);
-				fit_group = group;
-			}
 		}
 
 		/* Adjust by relative CPU capacity of the group */
@@ -5564,9 +5548,6 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p,
 		}
 	} while (group = group->next, group != sd->groups);
 
-	if (fit_group)
-		return fit_group;
-
 	if (!idlest || 100*this_load < imbalance*min_load)
 		return NULL;
 	return idlest;
@@ -5587,7 +5568,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 
 	/* Traverse only the allowed CPUs */
 	for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) {
-		if (task_fits_spare(p, i)) {
+		if (idle_cpu(i)) {
 			struct rq *rq = cpu_rq(i);
 			struct cpuidle_state *idle = idle_get_state(rq);
 			if (idle && idle->exit_latency < min_exit_latency) {
@@ -5599,8 +5580,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 				min_exit_latency = idle->exit_latency;
 				latest_idle_timestamp = rq->idle_stamp;
 				shallowest_idle_cpu = i;
-			} else if (idle_cpu(i) &&
-				   (!idle || idle->exit_latency == min_exit_latency) &&
+			} else if ((!idle || idle->exit_latency == min_exit_latency) &&
 				   rq->idle_stamp > latest_idle_timestamp) {
 				/*
 				 * If equal or no active idle state, then
@@ -5609,13 +5589,6 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
 				 */
 				latest_idle_timestamp = rq->idle_stamp;
 				shallowest_idle_cpu = i;
-			} else if (shallowest_idle_cpu == -1) {
-				/*
-				 * If we haven't found an idle CPU yet
-				 * pick a non-idle one that can fit the task as
-				 * fallback.
-				 */
-				shallowest_idle_cpu = i;
 			}
 		} else if (shallowest_idle_cpu == -1) {
 			load = weighted_cpuload(i);
@@ -5943,8 +5916,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
 	int sync = wake_flags & WF_SYNC;
 
 	if (sd_flag & SD_BALANCE_WAKE)
-		want_affine = (!wake_wide(p) && task_fits_max(p, cpu) &&
-			      cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
+		want_affine = (!wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) ||
 			      energy_aware();
 
 	rcu_read_lock();