[PATCH v3 07/20] sched/fair: Select preferred CPU at wakeup when possible

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Update available_idle_cpu to consider preferred CPUs. This takes care of
lot of decisions at wakeup to use only preferred CPUs. There is no need to
put those explicit checks everywhere.

Only other place where prev_cpu was not preferred and could possibly return
was sched_balance_find_dst_cpu. Put the check there.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 kernel/sched/fair.c  | 3 ++-
 kernel/sched/sched.h | 3 +++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 29fbb5287cfc..a704285ac55a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7743,7 +7743,8 @@ static inline int sched_balance_find_dst_cpu(struct sched_domain *sd, struct tas
 {
 	int new_cpu = cpu;
 
-	if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr))
+	if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr) &&
+	    cpu_preferred(prev_cpu))
 		return prev_cpu;
 
 	/*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index faf36bc7bd12..90743b9e5add 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1418,6 +1418,9 @@ static inline bool available_idle_cpu(int cpu)
 	if (!idle_rq(cpu_rq(cpu)))
 		return 0;
 
+	if (!cpu_preferred(cpu))
+		return 0;
+
 	if (vcpu_is_preempted(cpu))
 		return 0;
 
-- 
2.47.3