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Commit d987fc7f authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

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: default avatarMike Galbraith <mgalbraith@suse.de>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Lei Wen <leiwen@marvell.com>
Link: http://lkml.kernel.org/n/tip-vmme4f49psirp966pklm5l9j@git.kernel.org


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent de91b9cb

kernel/sched/fair.c

+18 −7
Original line number Diff line number Diff line
@@ -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)))) {

		/*

		 * 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.

 */