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Commit f549da84 authored by Suresh Siddha's avatar Suresh Siddha Committed by Ingo Molnar
Browse files

sched: skip updating rq's next_balance under null SD 



Was playing with sched_smt_power_savings/sched_mc_power_savings and
found out that while the scheduler domains are reconstructed when sysfs
settings change, rebalance_domains() can get triggered with null domain
on other cpus, which is setting next_balance to jiffies + 60*HZ.
Resulting in no idle/busy balancing for 60 seconds.

Fix this.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f8700df7

kernel/sched.c

+12 −2
Original line number Diff line number Diff line
@@ -3043,6 +3043,7 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) 
	struct sched_domain *sd;

	/* Earliest time when we have to do rebalance again */

	unsigned long next_balance = jiffies + 60*HZ;

	int update_next_balance = 0;



	for_each_domain(cpu, sd) {

		if (!(sd->flags & SD_LOAD_BALANCE))
@@ -3079,8 +3080,10 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) 
		if (sd->flags & SD_SERIALIZE)

			spin_unlock(&balancing);

out:

		if (time_after(next_balance, sd->last_balance + interval))

		if (time_after(next_balance, sd->last_balance + interval)) {

			next_balance = sd->last_balance + interval;

			update_next_balance = 1;

		}



		/*

		 * Stop the load balance at this level. There is another
@@ -3090,6 +3093,13 @@ static inline void rebalance_domains(int cpu, enum cpu_idle_type idle) 
		if (!balance)

			break;

	}



	/*

	 * next_balance will be updated only when there is a need.

	 * When the cpu is attached to null domain for ex, it will not be

	 * updated.

	 */

	if (likely(update_next_balance))

		rq->next_balance = next_balance;

}