sched: revise sched_boost to make the best of big cluster CPUs

At present sched_boost changes scheduler to place tasks on the least
loaded CPU under the assumption both big and little clusters capacities
are same at the same level of frequency.  This is suboptimal for the
big.Little system that doesn't have such a symmetrical capacity between
big and little CPUs.

Fix sched_boost to place tasks on the big CPUs for the non-symmetrical
capacity target.

CRs-fixed: 1006303
Change-Id: I752f020acf1a76580edb5cd0e5ad283b62edfeed
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>

kernel/sched/fair.c

@@ -2675,6 +2675,12 @@ struct cpu_pwr_stats __weak *get_cpu_pwr_stats(void)
 	return NULL;
 }
 
+enum sched_boost_type {
+	SCHED_BOOST_NONE,
+	SCHED_BOOST_ON_BIG,
+	SCHED_BOOST_ON_ALL,
+};
+
 #ifdef CONFIG_SCHED_HMP
 
 /* Initial task load. Newly created tasks are assigned this load. */
@@ -2995,31 +3001,46 @@ done:
  * tasks with load close to the upmigrate threshold
  */
 
-static int task_load_will_fit(struct task_struct *p, u64 task_load, int cpu)
+static int task_load_will_fit(struct task_struct *p, u64 task_load, int cpu,
+			      enum sched_boost_type boost_type)
 {
 	int upmigrate;
 
 	if (cpu_capacity(cpu) == max_capacity)
 		return 1;
 
-	if (task_nice(p) > sched_upmigrate_min_nice || upmigrate_discouraged(p))
-		return 1;
+	if (boost_type != SCHED_BOOST_ON_BIG) {
+		if (task_nice(p) > sched_upmigrate_min_nice ||
+		    upmigrate_discouraged(p))
+			return 1;
 
-	upmigrate = sched_upmigrate;
-	if (cpu_capacity(task_cpu(p)) > cpu_capacity(cpu))
-		upmigrate = sched_downmigrate;
+		upmigrate = sched_upmigrate;
+		if (cpu_capacity(task_cpu(p)) > cpu_capacity(cpu))
+			upmigrate = sched_downmigrate;
 
-	if (task_load < upmigrate)
-		return 1;
+		if (task_load < upmigrate)
+			return 1;
+	}
 
 	return 0;
 }
 
+static enum sched_boost_type sched_boost_type(void)
+{
+	if (sched_boost()) {
+		if (min_possible_efficiency != max_possible_efficiency)
+			return SCHED_BOOST_ON_BIG;
+		else
+			return SCHED_BOOST_ON_ALL;
+	}
+	return SCHED_BOOST_NONE;
+}
+
 static int task_will_fit(struct task_struct *p, int cpu)
 {
 	u64 tload = scale_load_to_cpu(task_load(p), cpu);
 
-	return task_load_will_fit(p, tload, cpu);
+	return task_load_will_fit(p, tload, cpu, sched_boost_type());
 }
 
 int group_will_fit(struct sched_cluster *cluster,
@@ -3123,9 +3144,9 @@ struct cpu_select_env {
 	u8 reason;
 	u8 need_idle:1;
 	u8 need_waker_cluster:1;
-	u8 boost:1;
 	u8 sync:1;
 	u8 ignore_prev_cpu:1;
+	enum sched_boost_type boost_type;
 	int prev_cpu;
 	DECLARE_BITMAP(candidate_list, NR_CPUS);
 	DECLARE_BITMAP(backup_list, NR_CPUS);
@@ -3272,7 +3293,8 @@ select_least_power_cluster(struct cpu_select_env *env)
 
 			env->task_load = scale_load_to_cpu(task_load(env->p),
 									 cpu);
-			if (task_load_will_fit(env->p, env->task_load, cpu))
+			if (task_load_will_fit(env->p, env->task_load, cpu,
+					       env->boost_type))
 				return cluster;
 
 			__set_bit(cluster->id, env->backup_list);
@@ -3507,7 +3529,8 @@ static void find_best_cpu_in_cluster(struct sched_cluster *c,
 		update_spare_capacity(stats, env, i, c->capacity,
 				      env->cpu_load);
 
-		if (env->boost || env->need_waker_cluster ||
+		if (env->boost_type == SCHED_BOOST_ON_ALL ||
+		    env->need_waker_cluster ||
 		    sched_cpu_high_irqload(i) ||
 		    spill_threshold_crossed(env, cpu_rq(i)))
 			continue;
@@ -3550,8 +3573,8 @@ bias_to_prev_cpu(struct cpu_select_env *env, struct cluster_cpu_stats *stats)
 	struct task_struct *task = env->p;
 	struct sched_cluster *cluster;
 
-	if (env->boost || env->reason || env->need_idle ||
-				!sched_short_sleep_task_threshold)
+	if (env->boost_type != SCHED_BOOST_NONE || env->reason ||
+	    env->need_idle || !sched_short_sleep_task_threshold)
 		return false;
 
 	prev_cpu = env->prev_cpu;
@@ -3572,7 +3595,8 @@ bias_to_prev_cpu(struct cpu_select_env *env, struct cluster_cpu_stats *stats)
 	env->task_load = scale_load_to_cpu(task_load(task), prev_cpu);
 	cluster = cpu_rq(prev_cpu)->cluster;
 
-	if (!task_load_will_fit(task, env->task_load, prev_cpu)) {
+	if (!task_load_will_fit(task, env->task_load, prev_cpu,
+				sched_boost_type())) {
 
 		__set_bit(cluster->id, env->backup_list);
 		__clear_bit(cluster->id, env->candidate_list);
@@ -3625,7 +3649,7 @@ static int select_best_cpu(struct task_struct *p, int target, int reason,
 		.reason			= reason,
 		.need_idle		= wake_to_idle(p),
 		.need_waker_cluster	= 0,
-		.boost			= sched_boost(),
+		.boost_type		= sched_boost_type(),
 		.sync			= sync,
 		.prev_cpu		= target,
 		.ignore_prev_cpu	= 0,
@@ -4203,6 +4227,12 @@ static inline int migration_needed(struct task_struct *p, int cpu)
 	if (task_will_be_throttled(p))
 		return 0;
 
+	if (sched_boost_type() == SCHED_BOOST_ON_BIG) {
+		if (cpu_capacity(cpu) != max_capacity)
+			return UP_MIGRATION;
+		return 0;
+	}
+
 	if (sched_cpu_high_irqload(cpu))
 		return IRQLOAD_MIGRATION;
 
@@ -4297,7 +4327,8 @@ unsigned int cpu_temp(int cpu)
 struct cpu_select_env;
 struct sched_cluster;
 
-static inline int task_will_fit(struct task_struct *p, int cpu)
+static inline int task_will_fit(struct task_struct *p, int cpu,
+				enum sched_boost_type boost_type)
 {
 	return 1;
 }