[PATCH 1/3] sched, balancing: Update rq->max_idle_balance_cost whenever newidle balance is attempted

[Jason Low]

Commit e5fc6611 can potentially cause rq->max_idle_balance_cost to not be
updated, even when load_balance(NEWLY_IDLE) is attempted and the per-sd
max cost value is updated.

In this patch, we update the rq->max_idle_balance_cost regardless of
whether or not a task has been enqueued while browsing the domains.

Signed-off-by: Jason Low <jason.low2@xxxxxx>
---
 kernel/sched/fair.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 43232b8..3e3ffb8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6658,6 +6658,7 @@ static int idle_balance(struct rq *this_rq)
 	int this_cpu = this_rq->cpu;
 
 	idle_enter_fair(this_rq);
+
 	/*
 	 * We must set idle_stamp _before_ calling idle_balance(), such that we
 	 * measure the duration of idle_balance() as idle time.
@@ -6710,9 +6711,12 @@ static int idle_balance(struct rq *this_rq)
 
 	raw_spin_lock(&this_rq->lock);
 
+	if (curr_cost > this_rq->max_idle_balance_cost)
+		this_rq->max_idle_balance_cost = curr_cost;
+
 	/*
 	 * While browsing the domains, we released the rq lock.
-	 * A task could have be enqueued in the meantime
+	 * A task could have been enqueued in the meantime.
 	 */
 	if (this_rq->cfs.h_nr_running && !pulled_task) {
 		pulled_task = 1;
@@ -6727,9 +6731,6 @@ static int idle_balance(struct rq *this_rq)
 		this_rq->next_balance = next_balance;
 	}
 
-	if (curr_cost > this_rq->max_idle_balance_cost)
-		this_rq->max_idle_balance_cost = curr_cost;
-
 out:
 	/* Is there a task of a high priority class? */
 	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
-- 
1.7.1

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