[PATCH 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched

[Mel Gorman]

The target CPU is definitely not idle in both select_idle_core and
select_idle_cpu. For select_idle_core(), the SMT is potentially
checked unnecessarily as the core is definitely not idle if the
target is busy. For select_idle_cpu(), the first CPU checked is
simply a waste.

Signed-off-by: Mel Gorman <mgorman at techsingularity.net>
---
 kernel/sched/fair.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 68dd9cd62fbd..1d8f5c4b4936 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6077,6 +6077,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
 		return -1;
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(core, cpus, target) {
 		bool idle = true;
@@ -6181,6 +6182,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
 	time = cpu_clock(this);
 
 	cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
+	__cpumask_clear_cpu(target, cpus);
 
 	for_each_cpu_wrap(cpu, cpus, target) {
 		schedstat_inc(this_rq()->sis_scanned);
-- 
2.26.2