sched: Convert the global wake_up_idle flag to a per cluster flag

Since clusters can vary significantly in the power and performance
characteristics, there may be a need to have different CPU selection
policies based on which cluster a task is being placed on. For example
the placement policy can be more aggressive in using idle CPUs on
cluster that are power efficient and less aggressive on clusters
that are geared towards performance. Add support for per cluster
wake_up_idle flag to allow greater flexibility in placement policies.

Change-Id: I18cd3d907cd965db03a13f4655870dc10c07acfe
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>

1 files changed, 19 insertions, 26 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 87538f7d495a..e1c8ec0458b3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -86,14 +86,6 @@ static unsigned int sched_nr_latency = 8;
 unsigned int sysctl_sched_child_runs_first __read_mostly;
 
 /*
- * Controls whether, when SD_SHARE_PKG_RESOURCES is on, if all
- * tasks go to idle CPUs when woken. If this is off, note that the
- * per-task flag PF_WAKE_UP_IDLE can still cause a task to go to an
- * idle CPU upon being woken.
- */
-unsigned int __read_mostly sysctl_sched_wake_to_idle;
-
-/*
  * SCHED_OTHER wake-up granularity.
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  *
@@ -2649,6 +2641,21 @@ struct cluster_cpu_stats {
 	s64 highest_spare_capacity;
 };
 
+/*
+ * Should task be woken to any available idle cpu?
+ *
+ * Waking tasks to idle cpu has mixed implications on both performance and
+ * power. In many cases, scheduler can't estimate correctly impact of using idle
+ * cpus on either performance or power. PF_WAKE_UP_IDLE allows external kernel
+ * module to pass a strong hint to scheduler that the task in question should be
+ * woken to idle cpu, generally to improve performance.
+ */
+static inline int wake_to_idle(struct task_struct *p)
+{
+	return (current->flags & PF_WAKE_UP_IDLE) ||
+		 (p->flags & PF_WAKE_UP_IDLE);
+}
+
 static int spill_threshold_crossed(struct cpu_select_env *env, struct rq *rq)
 {
 	u64 total_load;
@@ -3009,6 +3016,8 @@ static void find_best_cpu_in_cluster(struct sched_cluster *c,
 	if (env->ignore_prev_cpu)
 		cpumask_clear_cpu(env->prev_cpu, &search_cpus);
 
+	env->need_idle = wake_to_idle(env->p) || c->wake_up_idle;
+
 	for_each_cpu(i, &search_cpus) {
 		env->cpu_load = cpu_load_sync(i, env->sync);
 
@@ -3052,21 +3061,6 @@ static inline void init_cluster_cpu_stats(struct cluster_cpu_stats *stats)
 	/* No need to initialize stats->best_load */
 }
 
-/*
- * Should task be woken to any available idle cpu?
- *
- * Waking tasks to idle cpu has mixed implications on both performance and
- * power. In many cases, scheduler can't estimate correctly impact of using idle
- * cpus on either performance or power. PF_WAKE_UP_IDLE allows external kernel
- * module to pass a strong hint to scheduler that the task in question should be
- * woken to idle cpu, generally to improve performance.
- */
-static inline int wake_to_idle(struct task_struct *p)
-{
-	return (current->flags & PF_WAKE_UP_IDLE) ||
-		 (p->flags & PF_WAKE_UP_IDLE) || sysctl_sched_wake_to_idle;
-}
-
 static inline bool env_has_special_flags(struct cpu_select_env *env)
 {
 	if (env->need_idle || env->boost_policy != SCHED_BOOST_NONE ||
@@ -6755,9 +6749,8 @@ static int select_idle_sibling(struct task_struct *p, int target)
 			return i;
 	}
 
-	if (!sysctl_sched_wake_to_idle &&
-	    !(current->flags & PF_WAKE_UP_IDLE) &&
-	    !(p->flags & PF_WAKE_UP_IDLE))
+	if (!(current->flags & PF_WAKE_UP_IDLE) &&
+			!(p->flags & PF_WAKE_UP_IDLE))
 		return target;
 
 	/*