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Commit 2e6f44ae authored by Gautham R Shenoy's avatar Gautham R Shenoy Committed by Ingo Molnar
Browse files

sched: Create helper to calculate small_imbalance in fbg() 



Impact: cleanup

We have two places in find_busiest_group() where we need to calculate
the minor imbalance before returning the busiest group. Encapsulate
this functionality into a seperate helper function.

Credit: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
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>
LKML-Reference: <20090325091406.13992.54316.stgit@sofia.in.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 37abe198

kernel/sched.c

+70 −61
Original line number Diff line number Diff line
@@ -3484,6 +3484,71 @@ group_next: 
	} while (group != sd->groups);



}



/**

 * fix_small_imbalance - Calculate the minor imbalance that exists

 * 			amongst the groups of a sched_domain, during

 * 			load balancing.

 * @sds: Statistics of the sched_domain whose imbalance is to be calculated.

 * @this_cpu: The cpu at whose sched_domain we're performing load-balance.

 * @imbalance: Variable to store the imbalance.

 */

static inline void fix_small_imbalance(struct sd_lb_stats *sds,

				int this_cpu, unsigned long *imbalance)

{

	unsigned long tmp, pwr_now = 0, pwr_move = 0;

	unsigned int imbn = 2;



	if (sds->this_nr_running) {

		sds->this_load_per_task /= sds->this_nr_running;

		if (sds->busiest_load_per_task >

				sds->this_load_per_task)

			imbn = 1;

	} else

		sds->this_load_per_task =

			cpu_avg_load_per_task(this_cpu);



	if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=

			sds->busiest_load_per_task * imbn) {

		*imbalance = sds->busiest_load_per_task;

		return;

	}



	/*

	 * OK, we don't have enough imbalance to justify moving tasks,

	 * however we may be able to increase total CPU power used by

	 * moving them.

	 */



	pwr_now += sds->busiest->__cpu_power *

			min(sds->busiest_load_per_task, sds->max_load);

	pwr_now += sds->this->__cpu_power *

			min(sds->this_load_per_task, sds->this_load);

	pwr_now /= SCHED_LOAD_SCALE;



	/* Amount of load we'd subtract */

	tmp = sg_div_cpu_power(sds->busiest,

			sds->busiest_load_per_task * SCHED_LOAD_SCALE);

	if (sds->max_load > tmp)

		pwr_move += sds->busiest->__cpu_power *

			min(sds->busiest_load_per_task, sds->max_load - tmp);



	/* Amount of load we'd add */

	if (sds->max_load * sds->busiest->__cpu_power <

		sds->busiest_load_per_task * SCHED_LOAD_SCALE)

		tmp = sg_div_cpu_power(sds->this,

			sds->max_load * sds->busiest->__cpu_power);

	else

		tmp = sg_div_cpu_power(sds->this,

			sds->busiest_load_per_task * SCHED_LOAD_SCALE);

	pwr_move += sds->this->__cpu_power *

			min(sds->this_load_per_task, sds->this_load + tmp);

	pwr_move /= SCHED_LOAD_SCALE;



	/* Move if we gain throughput */

	if (pwr_move > pwr_now)

		*imbalance = sds->busiest_load_per_task;

}

/******* find_busiest_group() helpers end here *********************/



/*
@@ -3547,7 +3612,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
	 */

	if (sds.max_load < sds.avg_load) {

		*imbalance = 0;

		goto small_imbalance;

		fix_small_imbalance(&sds, this_cpu, imbalance);

		goto ret_busiest;

	}



	/* Don't want to pull so many tasks that a group would go idle */
@@ -3565,67 +3631,10 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 
	 * a think about bumping its value to force at least one task to be

	 * moved

	 */

	if (*imbalance < sds.busiest_load_per_task) {

		unsigned long tmp, pwr_now, pwr_move;

		unsigned int imbn;



small_imbalance:

		pwr_move = pwr_now = 0;

		imbn = 2;

		if (sds.this_nr_running) {

			sds.this_load_per_task /= sds.this_nr_running;

			if (sds.busiest_load_per_task >

					sds.this_load_per_task)

				imbn = 1;

		} else

			sds.this_load_per_task =

				cpu_avg_load_per_task(this_cpu);



		if (sds.max_load - sds.this_load +

			sds.busiest_load_per_task >=

				sds.busiest_load_per_task * imbn) {

			*imbalance = sds.busiest_load_per_task;

			return sds.busiest;

		}



		/*

		 * OK, we don't have enough imbalance to justify moving tasks,

		 * however we may be able to increase total CPU power used by

		 * moving them.

		 */



		pwr_now += sds.busiest->__cpu_power *

				min(sds.busiest_load_per_task, sds.max_load);

		pwr_now += sds.this->__cpu_power *

				min(sds.this_load_per_task, sds.this_load);

		pwr_now /= SCHED_LOAD_SCALE;



		/* Amount of load we'd subtract */

		tmp = sg_div_cpu_power(sds.busiest,

				sds.busiest_load_per_task * SCHED_LOAD_SCALE);

		if (sds.max_load > tmp)

			pwr_move += sds.busiest->__cpu_power *

				min(sds.busiest_load_per_task,

						sds.max_load - tmp);



		/* Amount of load we'd add */

		if (sds.max_load * sds.busiest->__cpu_power <

				sds.busiest_load_per_task * SCHED_LOAD_SCALE)

			tmp = sg_div_cpu_power(sds.this,

				sds.max_load * sds.busiest->__cpu_power);

		else

			tmp = sg_div_cpu_power(sds.this,

				sds.busiest_load_per_task * SCHED_LOAD_SCALE);

		pwr_move += sds.this->__cpu_power *

				min(sds.this_load_per_task,

					sds.this_load + tmp);

		pwr_move /= SCHED_LOAD_SCALE;



		/* Move if we gain throughput */

		if (pwr_move > pwr_now)

			*imbalance = sds.busiest_load_per_task;

	}

	if (*imbalance < sds.busiest_load_per_task)

		fix_small_imbalance(&sds, this_cpu, imbalance);



ret_busiest:

	return sds.busiest;



out_balanced: