From: Vincent Guittot <vincent.guittot@linaro.org>
To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
linux-kernel@vger.kernel.org, tim.c.chen@linux.intel.com
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH 2/2] sched/fair: Skip update_blocked_averages if we are defering load balance
Date: Mon, 4 Oct 2021 19:14:51 +0200 [thread overview]
Message-ID: <20211004171451.24090-3-vincent.guittot@linaro.org> (raw)
In-Reply-To: <20211004171451.24090-1-vincent.guittot@linaro.org>
In newidle_balance(), the scheduler skips load balance to the new idle cpu
when the 1st sd of this_rq is:
this_rq->avg_idle < sd->max_newidle_lb_cost
Doing a costly call to update_blocked_averages() will not be useful and
simply adds overhead when this condition is true.
Check the condition early in newidle_balance() to skip
update_blocked_averages() when possible.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
---
kernel/sched/fair.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1f78b2e3b71c..1294b78503d9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10841,17 +10841,20 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf)
*/
rq_unpin_lock(this_rq, rf);
+ rcu_read_lock();
+ sd = rcu_dereference_check_sched_domain(this_rq->sd);
+
if (this_rq->avg_idle < sysctl_sched_migration_cost ||
- !READ_ONCE(this_rq->rd->overload)) {
+ !READ_ONCE(this_rq->rd->overload) ||
+ (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
- rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq->sd);
if (sd)
update_next_balance(sd, &next_balance);
rcu_read_unlock();
goto out;
}
+ rcu_read_unlock();
raw_spin_rq_unlock(this_rq);
--
2.17.1
next prev parent reply other threads:[~2021-10-04 17:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 17:14 [PATCH 0/2] sched/fair: Improve cost accounting of newidle_balance Vincent Guittot
2021-10-04 17:14 ` [PATCH 1/2] sched/fair: account update_blocked_averages in newidle_balance cost Vincent Guittot
2021-10-05 20:40 ` Peter Zijlstra
2021-10-06 7:52 ` Vincent Guittot
2021-10-06 8:16 ` Vincent Guittot
2021-10-04 17:14 ` Vincent Guittot [this message]
2021-10-05 20:49 ` [PATCH 2/2] sched/fair: Skip update_blocked_averages if we are defering load balance Peter Zijlstra
2021-10-06 8:12 ` Vincent Guittot
2021-10-04 23:06 ` [PATCH 0/2] sched/fair: Improve cost accounting of newidle_balance Tim Chen
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