linux-kernel - [PATCH 1/2] sched/fair: account update_blocked_averages in newidle

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Message-Id: <20211004171451.24090-2-vincent.guittot@linaro.org>
Date:   Mon,  4 Oct 2021 19:14:50 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, linux-kernel@...r.kernel.org,
        tim.c.chen@...ux.intel.com
Cc:     Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 1/2] sched/fair: account update_blocked_averages in newidle_balance cost

The time spent to update the blocked load can be significant depending of
the complexity fo the cgroup hierarchy. Take this time into account when
deciding to stop newidle_balance() because it exceeds the expected idle
time.

Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
---
 kernel/sched/fair.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8943dbb94365..1f78b2e3b71c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10810,7 +10810,7 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
 	int this_cpu = this_rq->cpu;
 	struct sched_domain *sd;
 	int pulled_task = 0;
-	u64 curr_cost = 0;
+	u64 t0, domain_cost, curr_cost = 0;
 
 	update_misfit_status(NULL, this_rq);
 
@@ -10855,11 +10855,14 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
 
 	raw_spin_rq_unlock(this_rq);
 
+	t0 = sched_clock_cpu(this_cpu);
 	update_blocked_averages(this_cpu);
+	domain_cost = sched_clock_cpu(this_cpu) - t0;
+	curr_cost += domain_cost;
+
 	rcu_read_lock();
 	for_each_domain(this_cpu, sd) {
 		int continue_balancing = 1;
-		u64 t0, domain_cost;
 
 		if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) {
 			update_next_balance(sd, &next_balance);
-- 
2.17.1