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Commit 18a3885f authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Remove reciprocal for cpu_power 



Its a source of fail, also, now that cpu_power is dynamical,
its a waste of time.

before:
<idle>-0   [000]   132.877936: find_busiest_group: avg_load: 0 group_load: 8241 power: 1

after:
bash-1689  [001]   137.862151: find_busiest_group: avg_load: 10636288 group_load: 10387 power: 1

[ v2: build fix from From: Andreas Herrmann ]

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: default avatarGautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.425896304@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent d899a789

include/linux/sched.h

+2 −8
Original line number Diff line number Diff line
@@ -860,15 +860,9 @@ struct sched_group { 


	/*

	 * CPU power of this group, SCHED_LOAD_SCALE being max power for a

	 * single CPU. This is read only (except for setup, hotplug CPU).

	 * Note : Never change cpu_power without recompute its reciprocal

	 * single CPU.

	 */

	unsigned int __cpu_power;

	/*

	 * reciprocal value of cpu_power to avoid expensive divides

	 * (see include/linux/reciprocal_div.h)

	 */

	u32 reciprocal_cpu_power;

	unsigned int cpu_power;



	/*

	 * The CPUs this group covers.

kernel/sched.c

+34 −67
Original line number Diff line number Diff line
@@ -64,7 +64,6 @@ 
#include <linux/tsacct_kern.h>

#include <linux/kprobes.h>

#include <linux/delayacct.h>

#include <linux/reciprocal_div.h>

#include <linux/unistd.h>

#include <linux/pagemap.h>

#include <linux/hrtimer.h>
@@ -120,30 +119,8 @@ 
 */

#define RUNTIME_INF	((u64)~0ULL)



#ifdef CONFIG_SMP



static void double_rq_lock(struct rq *rq1, struct rq *rq2);



/*

 * Divide a load by a sched group cpu_power : (load / sg->__cpu_power)

 * Since cpu_power is a 'constant', we can use a reciprocal divide.

 */

static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)

{

	return reciprocal_divide(load, sg->reciprocal_cpu_power);

}



/*

 * Each time a sched group cpu_power is changed,

 * we must compute its reciprocal value

 */

static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)

{

	sg->__cpu_power += val;

	sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);

}

#endif



static inline int rt_policy(int policy)

{

	if (unlikely(policy == SCHED_FIFO || policy == SCHED_RR))
@@ -2335,8 +2312,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu) 
		}



		/* Adjust by relative CPU power of the group */

		avg_load = sg_div_cpu_power(group,

				avg_load * SCHED_LOAD_SCALE);

		avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;



		if (local_group) {

			this_load = avg_load;
@@ -3768,7 +3744,6 @@ static void update_cpu_power(struct sched_domain *sd, int cpu) 
	unsigned long weight = cpumask_weight(sched_domain_span(sd));

	unsigned long power = SCHED_LOAD_SCALE;

	struct sched_group *sdg = sd->groups;

	unsigned long old = sdg->__cpu_power;



	/* here we could scale based on cpufreq */
@@ -3783,33 +3758,26 @@ static void update_cpu_power(struct sched_domain *sd, int cpu) 
	if (!power)

		power = 1;



	if (power != old) {

		sdg->__cpu_power = power;

		sdg->reciprocal_cpu_power = reciprocal_value(power);

	}

	sdg->cpu_power = power;

}



static void update_group_power(struct sched_domain *sd, int cpu)

{

	struct sched_domain *child = sd->child;

	struct sched_group *group, *sdg = sd->groups;

	unsigned long power = sdg->__cpu_power;



	if (!child) {

		update_cpu_power(sd, cpu);

		return;

	}



	sdg->__cpu_power = 0;

	sdg->cpu_power = 0;



	group = child->groups;

	do {

		sdg->__cpu_power += group->__cpu_power;

		sdg->cpu_power += group->cpu_power;

		group = group->next;

	} while (group != child->groups);



	if (power != sdg->__cpu_power)

		sdg->reciprocal_cpu_power = reciprocal_value(sdg->__cpu_power);

}



/**
@@ -3889,8 +3857,7 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, 
	}



	/* Adjust by relative CPU power of the group */

	sgs->avg_load = sg_div_cpu_power(group,

			sgs->group_load * SCHED_LOAD_SCALE);

	sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;





	/*
@@ -3902,14 +3869,14 @@ static inline void update_sg_lb_stats(struct sched_domain *sd, 
	 *      normalized nr_running number somewhere that negates

	 *      the hierarchy?

	 */

	avg_load_per_task = sg_div_cpu_power(group,

			sum_avg_load_per_task * SCHED_LOAD_SCALE);

	avg_load_per_task = (sum_avg_load_per_task * SCHED_LOAD_SCALE) /

		group->cpu_power;



	if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)

		sgs->group_imb = 1;



	sgs->group_capacity =

		DIV_ROUND_CLOSEST(group->__cpu_power, SCHED_LOAD_SCALE);

		DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);

}



/**
@@ -3951,7 +3918,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, 
			return;



		sds->total_load += sgs.group_load;

		sds->total_pwr += group->__cpu_power;

		sds->total_pwr += group->cpu_power;



		/*

		 * In case the child domain prefers tasks go to siblings
@@ -4016,28 +3983,28 @@ static inline void fix_small_imbalance(struct sd_lb_stats *sds, 
	 * moving them.

	 */



	pwr_now += sds->busiest->__cpu_power *

	pwr_now += sds->busiest->cpu_power *

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

	pwr_now += sds->this->__cpu_power *

	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);

	tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /

		sds->busiest->cpu_power;

	if (sds->max_load > tmp)

		pwr_move += sds->busiest->__cpu_power *

		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 <

	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);

		tmp = (sds->max_load * sds->busiest->cpu_power) /

			sds->this->cpu_power;

	else

		tmp = sg_div_cpu_power(sds->this,

			sds->busiest_load_per_task * SCHED_LOAD_SCALE);

	pwr_move += sds->this->__cpu_power *

		tmp = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /

			sds->this->cpu_power;

	pwr_move += sds->this->cpu_power *

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

	pwr_move /= SCHED_LOAD_SCALE;
@@ -4072,8 +4039,8 @@ static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu, 
			sds->max_load - sds->busiest_load_per_task);



	/* How much load to actually move to equalise the imbalance */

	*imbalance = min(max_pull * sds->busiest->__cpu_power,

		(sds->avg_load - sds->this_load) * sds->this->__cpu_power)

	*imbalance = min(max_pull * sds->busiest->cpu_power,

		(sds->avg_load - sds->this_load) * sds->this->cpu_power)

			/ SCHED_LOAD_SCALE;



	/*
@@ -4208,7 +4175,7 @@ static unsigned long power_of(int cpu) 
	if (!group)

		return SCHED_LOAD_SCALE;



	return group->__cpu_power;

	return group->cpu_power;

}



/*
@@ -7922,7 +7889,7 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level, 
			break;

		}



		if (!group->__cpu_power) {

		if (!group->cpu_power) {

			printk(KERN_CONT "\n");

			printk(KERN_ERR "ERROR: domain->cpu_power not "

					"set\n");
@@ -7946,9 +7913,9 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level, 
		cpulist_scnprintf(str, sizeof(str), sched_group_cpus(group));



		printk(KERN_CONT " %s", str);

		if (group->__cpu_power != SCHED_LOAD_SCALE) {

			printk(KERN_CONT " (__cpu_power = %d)",

				group->__cpu_power);

		if (group->cpu_power != SCHED_LOAD_SCALE) {

			printk(KERN_CONT " (cpu_power = %d)",

				group->cpu_power);

		}



		group = group->next;
@@ -8233,7 +8200,7 @@ init_sched_build_groups(const struct cpumask *span, 
			continue;



		cpumask_clear(sched_group_cpus(sg));

		sg->__cpu_power = 0;

		sg->cpu_power = 0;



		for_each_cpu(j, span) {

			if (group_fn(j, cpu_map, NULL, tmpmask) != group)
@@ -8491,7 +8458,7 @@ static void init_numa_sched_groups_power(struct sched_group *group_head) 
				continue;

			}



			sg_inc_cpu_power(sg, sd->groups->__cpu_power);

			sg->cpu_power += sd->groups->cpu_power;

		}

		sg = sg->next;

	} while (sg != group_head);
@@ -8528,7 +8495,7 @@ static int build_numa_sched_groups(struct s_data *d, 
		sd->groups = sg;

	}



	sg->__cpu_power = 0;

	sg->cpu_power = 0;

	cpumask_copy(sched_group_cpus(sg), d->nodemask);

	sg->next = sg;

	cpumask_or(d->covered, d->covered, d->nodemask);
@@ -8551,7 +8518,7 @@ static int build_numa_sched_groups(struct s_data *d, 
			       "Can not alloc domain group for node %d\n", j);

			return -ENOMEM;

		}

		sg->__cpu_power = 0;

		sg->cpu_power = 0;

		cpumask_copy(sched_group_cpus(sg), d->tmpmask);

		sg->next = prev->next;

		cpumask_or(d->covered, d->covered, d->tmpmask);
@@ -8629,7 +8596,7 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd) 


	child = sd->child;



	sd->groups->__cpu_power = 0;

	sd->groups->cpu_power = 0;



	if (!child) {

		power = SCHED_LOAD_SCALE;
@@ -8645,7 +8612,7 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd) 
			power /= weight;

			power >>= SCHED_LOAD_SHIFT;

		}

		sg_inc_cpu_power(sd->groups, power);

		sd->groups->cpu_power += power;

		return;

	}
@@ -8654,7 +8621,7 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd) 
	 */

	group = child->groups;

	do {

		sg_inc_cpu_power(sd->groups, group->__cpu_power);

		sd->groups->cpu_power += group->cpu_power;

		group = group->next;

	} while (group != child->groups);

}