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Subject[PATCH 1/2] sched/fair: skip newidle update stats
Date
In case we skip the newly idle LB entirely or we abort it because we are
going to exceed the avg_idle, we have to make sure to not start an update
of the blocked load when entering idle

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 13950beb01a2..a162b0ec8963 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10861,7 +10861,7 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
int this_cpu = this_rq->cpu;
u64 t0, t1, curr_cost = 0;
struct sched_domain *sd;
- int pulled_task = 0;
+ int pulled_task = 0, early_stop = 0;

update_misfit_status(NULL, this_rq);

@@ -10898,8 +10898,16 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
if (!READ_ONCE(this_rq->rd->overload) ||
(sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {

- if (sd)
+ if (sd) {
update_next_balance(sd, &next_balance);
+
+ /*
+ * We skip new idle LB because there is not enough
+ * time before next wake up. Make sure that we will
+ * not kick NOHZ_NEWILB_KICK
+ */
+ early_stop = 1;
+ }
rcu_read_unlock();

goto out;
@@ -10918,8 +10926,10 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)

update_next_balance(sd, &next_balance);

- if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost)
+ if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
+ early_stop = 1;
break;
+ }

if (sd->flags & SD_BALANCE_NEWIDLE) {

@@ -10969,7 +10979,7 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)

if (pulled_task)
this_rq->idle_stamp = 0;
- else
+ else if (!early_stop)
nohz_newidle_balance(this_rq);

rq_repin_lock(this_rq, rf);
--
2.17.1
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