linux-kernel - [PATCH 1/5] sched/fair: Use for_each_cpu

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Message-Id: <20190117153411.2390-2-valentin.schneider@arm.com>
Date:   Thu, 17 Jan 2019 15:34:07 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
        morten.rasmussen@....com, Dietmar.Eggemann@....com
Subject: [PATCH 1/5] sched/fair: Use for_each_cpu_and for asym-packing nohz kicks

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@....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