Messages in this thread Patch in this message |  | | From | Vincent Guittot <> | Subject | [PATCH v3 2/5] sched/fair: Skip update_blocked_averages if we are defering load balance | Date | Tue, 19 Oct 2021 14:35:34 +0200 |
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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 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); -- 2.17.1
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