From d987fc7f3228bf94cb6b21313ebab1d64ee637ad Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Mon, 5 Dec 2011 10:01:47 +0100 Subject: sched, nohz: Exclude isolated cores from load balancing The user explicitly disabled load balancing, else this core would not be disconnected. Don't add these to nohz.idle_cpus_mask. Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra Cc: Lei Wen Link: http://lkml.kernel.org/n/tip-vmme4f49psirp966pklm5l9j@git.kernel.org Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7982faf..a3a41c61 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6788,6 +6788,11 @@ out_unlock: return 0; } +static inline int on_null_domain(struct rq *rq) +{ + return unlikely(!rcu_dereference_sched(rq->sd)); +} + #ifdef CONFIG_NO_HZ_COMMON /* * idle load balancing details @@ -6842,8 +6847,13 @@ static void nohz_balancer_kick(void) static inline void nohz_balance_exit_idle(int cpu) { if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { - cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); - atomic_dec(&nohz.nr_cpus); + /* + * Completely isolated CPUs don't ever set, so we must test. + */ + if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { + cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); + atomic_dec(&nohz.nr_cpus); + } clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); } } @@ -6897,6 +6907,12 @@ void nohz_balance_enter_idle(int cpu) if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) return; + /* + * If we're a completely isolated CPU, we don't play. + */ + if (on_null_domain(cpu_rq(cpu))) + return; + cpumask_set_cpu(cpu, nohz.idle_cpus_mask); atomic_inc(&nohz.nr_cpus); set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); @@ -7159,11 +7175,6 @@ static void run_rebalance_domains(struct softirq_action *h) nohz_idle_balance(this_rq, idle); } -static inline int on_null_domain(struct rq *rq) -{ - return !rcu_dereference_sched(rq->sd); -} - /* * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. */ -- cgit v1.1