The following commit has been merged into the sched/core branch of tip: Commit-ID: 9d783c8dd112ad4b619e74e4bf57d2be0b400693 Gitweb: https://git.kernel.org/tip/9d783c8dd112ad4b619e74e4bf57d2be0b400693 Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx> AuthorDate: Tue, 19 Oct 2021 14:35:34 +02:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Sun, 31 Oct 2021 11:11:37 +01:00 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 <vincent.guittot@xxxxxxxxxx> Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxx> Link: https://lore.kernel.org/r/20211019123537.17146-3-vincent.guittot@xxxxxxxxxx --- 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 c014567..c4c3686 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);
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