Commit 1af3ed3d authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Unify load_balance{,_newidle}() 



load_balance() and load_balance_newidle() look remarkably similar, one
key point they differ in is the condition on when to active balance.

So split out that logic into a separate function.

One side effect is that previously load_balance_newidle() used to fail
and return -1 under these conditions, whereas now it doesn't. I've not
yet fully figured out the whole -1 return case for either
load_balance{,_newidle}().

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent baa8c110

kernel/sched_fair.c

+59 −56
Original line number Diff line number Diff line
@@ -2816,6 +2816,39 @@ find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle, 
/* Working cpumask for load_balance and load_balance_newidle. */

static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);



static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle)

{

	if (idle == CPU_NEWLY_IDLE) {

		/*

		 * The only task running in a non-idle cpu can be moved to this

		 * cpu in an attempt to completely freeup the other CPU

		 * package.

		 *

		 * The package power saving logic comes from

		 * find_busiest_group(). If there are no imbalance, then

		 * f_b_g() will return NULL. However when sched_mc={1,2} then

		 * f_b_g() will select a group from which a running task may be

		 * pulled to this cpu in order to make the other package idle.

		 * If there is no opportunity to make a package idle and if

		 * there are no imbalance, then f_b_g() will return NULL and no

		 * action will be taken in load_balance_newidle().

		 *

		 * Under normal task pull operation due to imbalance, there

		 * will be more than one task in the source run queue and

		 * move_tasks() will succeed.  ld_moved will be true and this

		 * active balance code will not be triggered.

		 */

		if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&

		    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))

			return 0;



		if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)

			return 0;

	}



	return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);

}



/*

 * Check this_cpu to ensure it is balanced within domain. Attempt to move

 * tasks if there is an imbalance.
@@ -2902,8 +2935,7 @@ redo: 
		schedstat_inc(sd, lb_failed[idle]);

		sd->nr_balance_failed++;



		if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {



		if (need_active_balance(sd, sd_idle, idle)) {

			raw_spin_lock_irqsave(&busiest->lock, flags);



			/* don't kick the migration_thread, if the curr
@@ -3049,46 +3081,17 @@ redo: 
		int active_balance = 0;



		schedstat_inc(sd, lb_failed[CPU_NEWLY_IDLE]);

		if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&

		    !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))

			return -1;



		if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)

			return -1;



		if (sd->nr_balance_failed++ < 2)

			return -1;



		/*

		 * The only task running in a non-idle cpu can be moved to this

		 * cpu in an attempt to completely freeup the other CPU

		 * package. The same method used to move task in load_balance()

		 * have been extended for load_balance_newidle() to speedup

		 * consolidation at sched_mc=POWERSAVINGS_BALANCE_WAKEUP (2)

		 *

		 * The package power saving logic comes from

		 * find_busiest_group().  If there are no imbalance, then

		 * f_b_g() will return NULL.  However when sched_mc={1,2} then

		 * f_b_g() will select a group from which a running task may be

		 * pulled to this cpu in order to make the other package idle.

		 * If there is no opportunity to make a package idle and if

		 * there are no imbalance, then f_b_g() will return NULL and no

		 * action will be taken in load_balance_newidle().

		 *

		 * Under normal task pull operation due to imbalance, there

		 * will be more than one task in the source run queue and

		 * move_tasks() will succeed.  ld_moved will be true and this

		 * active balance code will not be triggered.

		 */

		sd->nr_balance_failed++;



		/* Lock busiest in correct order while this_rq is held */

		if (need_active_balance(sd, sd_idle, CPU_NEWLY_IDLE)) {

			double_lock_balance(this_rq, busiest);



			/*

			 * don't kick the migration_thread, if the curr

			 * task on busiest cpu can't be moved to this_cpu

			 */

		if (!cpumask_test_cpu(this_cpu, &busiest->curr->cpus_allowed)) {

			if (!cpumask_test_cpu(this_cpu,

					      &busiest->curr->cpus_allowed)) {

				double_unlock_balance(this_rq, busiest);

				all_pinned = 1;

				return ld_moved;
@@ -3108,7 +3111,7 @@ redo: 
			if (active_balance)

				wake_up_process(busiest->migration_thread);

			raw_spin_lock(&this_rq->lock);



		}

	} else

		sd->nr_balance_failed = 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE