diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index af120e88720f..9afe0c69a3c1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12441,20 +12441,29 @@ static void nohz_balancer_kick(struct rq *rq) */ nohz_balance_exit_idle(rq); - /* - * None are in tickless mode and hence no need for NOHZ idle load - * balancing: - */ - if (likely(!atomic_read(&nohz.nr_cpus))) - return; - if (READ_ONCE(nohz.has_blocked_load) && time_after(now, READ_ONCE(nohz.next_blocked))) flags = NOHZ_STATS_KICK; + /* + * Most of the time system is not 100% busy. i.e nohz.nr_cpus > 0 + * Skip the read if time is not due. + * + * If none are in tickless mode, there maybe a narrow window + * (28 jiffies, HZ=1000) where flags maybe set and kick_ilb called. + * But idle load balancing is not done as find_new_ilb fails. + * That's very rare. So read nohz.nr_cpus only if time is due. + */ if (time_before(now, nohz.next_balance)) goto out; + /* + * None are in tickless mode and hence no need for NOHZ idle load + * balancing: + */ + if (likely(!atomic_read(&nohz.nr_cpus))) + return; + if (rq->nr_running >= 2) { flags = NOHZ_STATS_KICK | NOHZ_BALANCE_KICK; goto out; |