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: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Acked-by: Gautham R Shenoy <ego@in.ibm.com>
Cc: Balbir Singh <balbir@in.ibm.com>
LKML-Reference: <20090901083826.425896304@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 34 insertions, 67 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index e1ebf9b00f5d..b53785346850 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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);
 }