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Commit c071df18 authored by Gautham R Shenoy's avatar Gautham R Shenoy Committed by Ingo Molnar
Browse files

sched: Refactor the power savings balance code 



Impact: cleanup

Create seperate helper functions to initialize the
power-savings-balance related variables, to update them and
to check if we have a scope for performing power-savings balance.

Add no-op inline functions for the !(CONFIG_SCHED_MC || CONFIG_SCHED_SMT)
case.

This will eliminate all the #ifdef jungle in find_busiest_group() and the
other helper functions.

Signed-off-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "Balbir Singh" <balbir@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "Dhaval Giani" <dhaval@linux.vnet.ibm.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: "Vaidyanathan Srinivasan" <svaidy@linux.vnet.ibm.com>
LKML-Reference: <20090325091422.13992.73616.stgit@sofia.in.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a021dc03

kernel/sched.c

+153 −83
Original line number Diff line number Diff line
@@ -3270,6 +3270,151 @@ static inline int get_sd_load_idx(struct sched_domain *sd, 
}





#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)

/**

 * init_sd_power_savings_stats - Initialize power savings statistics for

 * the given sched_domain, during load balancing.

 *

 * @sd: Sched domain whose power-savings statistics are to be initialized.

 * @sds: Variable containing the statistics for sd.

 * @idle: Idle status of the CPU at which we're performing load-balancing.

 */

static inline void init_sd_power_savings_stats(struct sched_domain *sd,

	struct sd_lb_stats *sds, enum cpu_idle_type idle)

{

	/*

	 * Busy processors will not participate in power savings

	 * balance.

	 */

	if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))

		sds->power_savings_balance = 0;

	else {

		sds->power_savings_balance = 1;

		sds->min_nr_running = ULONG_MAX;

		sds->leader_nr_running = 0;

	}

}



/**

 * update_sd_power_savings_stats - Update the power saving stats for a

 * sched_domain while performing load balancing.

 *

 * @group: sched_group belonging to the sched_domain under consideration.

 * @sds: Variable containing the statistics of the sched_domain

 * @local_group: Does group contain the CPU for which we're performing

 * 		load balancing ?

 * @sgs: Variable containing the statistics of the group.

 */

static inline void update_sd_power_savings_stats(struct sched_group *group,

	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)

{



	if (!sds->power_savings_balance)

		return;



	/*

	 * If the local group is idle or completely loaded

	 * no need to do power savings balance at this domain

	 */

	if (local_group && (sds->this_nr_running >= sgs->group_capacity ||

				!sds->this_nr_running))

		sds->power_savings_balance = 0;



	/*

	 * If a group is already running at full capacity or idle,

	 * don't include that group in power savings calculations

	 */

	if (!sds->power_savings_balance ||

		sgs->sum_nr_running >= sgs->group_capacity ||

		!sgs->sum_nr_running)

		return;



	/*

	 * Calculate the group which has the least non-idle load.

	 * This is the group from where we need to pick up the load

	 * for saving power

	 */

	if ((sgs->sum_nr_running < sds->min_nr_running) ||

	    (sgs->sum_nr_running == sds->min_nr_running &&

	     group_first_cpu(group) > group_first_cpu(sds->group_min))) {

		sds->group_min = group;

		sds->min_nr_running = sgs->sum_nr_running;

		sds->min_load_per_task = sgs->sum_weighted_load /

						sgs->sum_nr_running;

	}



	/*

	 * Calculate the group which is almost near its

	 * capacity but still has some space to pick up some load

	 * from other group and save more power

	 */

	if (sgs->sum_nr_running > sgs->group_capacity - 1)

		return;



	if (sgs->sum_nr_running > sds->leader_nr_running ||

	    (sgs->sum_nr_running == sds->leader_nr_running &&

	     group_first_cpu(group) < group_first_cpu(sds->group_leader))) {

		sds->group_leader = group;

		sds->leader_nr_running = sgs->sum_nr_running;

	}

}



/**

 * check_power_save_busiest_group - Check if we have potential to perform

 *	some power-savings balance. If yes, set the busiest group to be

 *	the least loaded group in the sched_domain, so that it's CPUs can

 *	be put to idle.

 *

 * @sds: Variable containing the statistics of the sched_domain

 *	under consideration.

 * @this_cpu: Cpu at which we're currently performing load-balancing.

 * @imbalance: Variable to store the imbalance.

 *

 * Returns 1 if there is potential to perform power-savings balance.

 * Else returns 0.

 */

static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,

					int this_cpu, unsigned long *imbalance)

{

	if (!sds->power_savings_balance)

		return 0;



	if (sds->this != sds->group_leader ||

			sds->group_leader == sds->group_min)

		return 0;



	*imbalance = sds->min_load_per_task;

	sds->busiest = sds->group_min;



	if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {

		cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =

			group_first_cpu(sds->group_leader);

	}



	return 1;



}

#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */

static inline void init_sd_power_savings_stats(struct sched_domain *sd,

	struct sd_lb_stats *sds, enum cpu_idle_type idle)

{

	return;

}



static inline void update_sd_power_savings_stats(struct sched_group *group,

	struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)

{

	return;

}



static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,

					int this_cpu, unsigned long *imbalance)

{

	return 0;

}

#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */





/**

 * update_sg_lb_stats - Update sched_group's statistics for load balancing.

 * @group: sched_group whose statistics are to be updated.
@@ -3385,19 +3530,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, 
	struct sg_lb_stats sgs;

	int load_idx;



#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)

	/*

	 * Busy processors will not participate in power savings

	 * balance.

	 */

	if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))

		sds->power_savings_balance = 0;

	else {

		sds->power_savings_balance = 1;

		sds->min_nr_running = ULONG_MAX;

		sds->leader_nr_running = 0;

	}

#endif

	init_sd_power_savings_stats(sd, sds, idle);

	load_idx = get_sd_load_idx(sd, idle);



	do {
@@ -3430,61 +3563,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, 
			sds->group_imb = sgs.group_imb;

		}



#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)



		if (!sds->power_savings_balance)

			goto group_next;



		/*

		 * If the local group is idle or completely loaded

		 * no need to do power savings balance at this domain

		 */

		if (local_group &&

			(sds->this_nr_running >= sgs.group_capacity ||

			!sds->this_nr_running))

			sds->power_savings_balance = 0;



		/*

		 * If a group is already running at full capacity or idle,

		 * don't include that group in power savings calculations

		 */

		if (!sds->power_savings_balance ||

			sgs.sum_nr_running >= sgs.group_capacity ||

			!sgs.sum_nr_running)

			goto group_next;



		/*

		 * Calculate the group which has the least non-idle load.

		 * This is the group from where we need to pick up the load

		 * for saving power

		 */

		if ((sgs.sum_nr_running < sds->min_nr_running) ||

		    (sgs.sum_nr_running == sds->min_nr_running &&

		     group_first_cpu(group) >

			group_first_cpu(sds->group_min))) {

			sds->group_min = group;

			sds->min_nr_running = sgs.sum_nr_running;

			sds->min_load_per_task = sgs.sum_weighted_load /

						sgs.sum_nr_running;

		}



		/*

		 * Calculate the group which is almost near its

		 * capacity but still has some space to pick up some load

		 * from other group and save more power

		 */

		if (sgs.sum_nr_running > sgs.group_capacity - 1)

			goto group_next;



		if (sgs.sum_nr_running > sds->leader_nr_running ||

		    (sgs.sum_nr_running == sds->leader_nr_running &&

		     group_first_cpu(group) <

			group_first_cpu(sds->group_leader))) {

			sds->group_leader = group;

			sds->leader_nr_running = sgs.sum_nr_running;

		}

group_next:

#endif

		update_sd_power_savings_stats(group, sds, local_group, &sgs);

		group = group->next;

	} while (group != sd->groups);
@@ -3655,21 +3734,12 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
	return sds.busiest;



out_balanced:

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)

	if (!sds.power_savings_balance)

		goto ret;



	if (sds.this != sds.group_leader || sds.group_leader == sds.group_min)

		goto ret;



	*imbalance = sds.min_load_per_task;

	if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {

		cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =

			group_first_cpu(sds.group_leader);

	}

	return sds.group_min;



#endif

	/*

	 * There is no obvious imbalance. But check if we can do some balancing

	 * to save power.

	 */

	if (check_power_save_busiest_group(&sds, this_cpu, imbalance))

		return sds.busiest;

ret:

	*imbalance = 0;

	return NULL;