From 9d783c8dd112ad4b619e74e4bf57d2be0b400693 Mon Sep 17 00:00:00 2001 From: Vincent Guittot Date: Tue, 19 Oct 2021 14:35:34 +0200 Subject: [PATCH] sched/fair: Skip update_blocked_averages if we are defering load balance 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 Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dietmar Eggemann Acked-by: Mel Gorman Link: https://lore.kernel.org/r/20211019123537.17146-3-vincent.guittot@linaro.org --- 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 c0145677ee99..c4c36865321b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10873,17 +10873,20 @@ 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); -- 2.34.1