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Subject[PATCH 1/5] sched/fair: Use for_each_cpu_and for asym-packing nohz kicks
Date
Calling 'nohz_balance_exit_idle(rq)' will always clear 'rq->cpu' from
'nohz.idle_cpus_mask' if it is set. Since it is called at the top of
'nohz_balancer_kick()', 'rq->cpu' will never be set in
'nohz.idle_cpus_mask' if it is accessed in the rest of the function.

"And" the 'sched_domain_span()' with 'nohz.idle_cpus_mask' and drop the
'(i == cpu)' check since 'rq->cpu' will never be iterated over.

While at it, clean up a condition alignment.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/fair.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ca469646ebe1..380a72e42678 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9557,7 +9557,7 @@ static void nohz_balancer_kick(struct rq *rq)
sd = rcu_dereference(rq->sd);
if (sd) {
if ((rq->cfs.h_nr_running >= 1) &&
- check_cpu_capacity(rq, sd)) {
+ check_cpu_capacity(rq, sd)) {
flags = NOHZ_KICK_MASK;
goto unlock;
}
@@ -9565,11 +9565,7 @@ static void nohz_balancer_kick(struct rq *rq)

sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));
if (sd) {
- for_each_cpu(i, sched_domain_span(sd)) {
- if (i == cpu ||
- !cpumask_test_cpu(i, nohz.idle_cpus_mask))
- continue;
-
+ for_each_cpu_and(i, sched_domain_span(sd), nohz.idle_cpus_mask) {
if (sched_asym_prefer(i, cpu)) {
flags = NOHZ_KICK_MASK;
goto unlock;
--
2.20.1
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