sched: Clean-up struct sd_lb_stat

There is no reason to maintain separate variables for this_group
and busiest_group in sd_lb_stat, except saving some space.
But this structure is always allocated in stack, so this saving
isn't really benificial [peterz: reducing stack space is good; in this
case readability increases enough that I think its still beneficial]

This patch unify these variables, so IMO, readability may be improved.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
[ Rename this to local -- avoids confusion between this_cpu and the C++ this pointer. ]
Reviewed-by: Paul  Turner <pjt@google.com>
[ Lots of style edits, a few fixes and a rename. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1375778203-31343-4-git-send-email-iamjoonsoo.kim@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 114 insertions, 115 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9a6daf86a76a..2da80a55827b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4232,36 +4232,6 @@ static unsigned long task_h_load(struct task_struct *p)
 
 /********** Helpers for find_busiest_group ************************/
 /*
- * sd_lb_stats - Structure to store the statistics of a sched_domain
- *              during load balancing.
- */
-struct sd_lb_stats {
-        struct sched_group *busiest; /* Busiest group in this sd */
-        struct sched_group *this;  /* Local group in this sd */
-        unsigned long total_load;  /* Total load of all groups in sd */
-        unsigned long total_pwr;   /*   Total power of all groups in sd */
-        unsigned long avg_load;    /* Average load across all groups in sd */
-
-        /** Statistics of this group */
-        unsigned long this_load;
-        unsigned long this_load_per_task;
-        unsigned long this_nr_running;
-        unsigned long this_has_capacity;
-        unsigned int  this_idle_cpus;
-
-        /* Statistics of the busiest group */
-        unsigned int  busiest_idle_cpus;
-        unsigned long max_load;
-        unsigned long busiest_load_per_task;
-        unsigned long busiest_nr_running;
-        unsigned long busiest_group_capacity;
-        unsigned long busiest_has_capacity;
-        unsigned int  busiest_group_weight;
-
-        int group_imb; /* Is there imbalance in this sd */
-};
-
-/*
  * sg_lb_stats - stats of a sched_group required for load_balancing
  */
 struct sg_lb_stats {
@@ -4269,6 +4239,7 @@ struct sg_lb_stats {
         unsigned long group_load; /* Total load over the CPUs of the group */
         unsigned long sum_nr_running; /* Nr tasks running in the group */
         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
+        unsigned long load_per_task;
         unsigned long group_capacity;
         unsigned long idle_cpus;
         unsigned long group_weight;
@@ -4276,6 +4247,21 @@ struct sg_lb_stats {
         int group_has_capacity; /* Is there extra capacity in the group? */
 };
 
+/*
+ * sd_lb_stats - Structure to store the statistics of a sched_domain
+ *               during load balancing.
+ */
+struct sd_lb_stats {
+        struct sched_group *busiest;    /* Busiest group in this sd */
+        struct sched_group *local;      /* Local group in this sd */
+        unsigned long total_load;       /* Total load of all groups in sd */
+        unsigned long total_pwr;        /* Total power of all groups in sd */
+        unsigned long avg_load; /* Average load across all groups in sd */
+
+        struct sg_lb_stats local_stat;  /* Statistics of the local group */
+        struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */
+};
+
 /**
  * get_sd_load_idx - Obtain the load index for a given sched domain.
  * @sd: The sched_domain whose load_idx is to be obtained.
@@ -4490,6 +4476,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
                         load = target_load(i, load_idx);
                 } else {
                         load = source_load(i, load_idx);
+
                         if (load > max_cpu_load)
                                 max_cpu_load = load;
                         if (min_cpu_load > load)
@@ -4531,10 +4518,12 @@ static inline void update_sg_lb_stats(struct lb_env *env,
             (max_nr_running - min_nr_running) > 1)
                 sgs->group_imb = 1;
 
-        sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power,
-                                                SCHED_POWER_SCALE);
+        sgs->group_capacity =
+                DIV_ROUND_CLOSEST(group->sgp->power, SCHED_POWER_SCALE);
+
         if (!sgs->group_capacity)
                 sgs->group_capacity = fix_small_capacity(env->sd, group);
+
         sgs->group_weight = group->group_weight;
 
         if (sgs->group_capacity > sgs->sum_nr_running)
@@ -4556,7 +4545,7 @@ static bool update_sd_pick_busiest(struct lb_env *env,
                                    struct sched_group *sg,
                                    struct sg_lb_stats *sgs)
 {
-        if (sgs->avg_load <= sds->max_load)
+        if (sgs->avg_load <= sds->busiest_stat.avg_load)
                 return false;
 
         if (sgs->sum_nr_running > sgs->group_capacity)
@@ -4593,7 +4582,7 @@ static inline void update_sd_lb_stats(struct lb_env *env,
 {
         struct sched_domain *child = env->sd->child;
         struct sched_group *sg = env->sd->groups;
-        struct sg_lb_stats sgs;
+        struct sg_lb_stats tmp_sgs;
         int load_idx, prefer_sibling = 0;
 
         if (child && child->flags & SD_PREFER_SIBLING)
@@ -4602,14 +4591,17 @@ static inline void update_sd_lb_stats(struct lb_env *env,
         load_idx = get_sd_load_idx(env->sd, env->idle);
 
         do {
+                struct sg_lb_stats *sgs = &tmp_sgs;
                 int local_group;
 
                 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg));
-                memset(&sgs, 0, sizeof(sgs));
-                update_sg_lb_stats(env, sg, load_idx, local_group, &sgs);
+                if (local_group) {
+                        sds->local = sg;
+                        sgs = &sds->local_stat;
+                }
 
-                sds->total_load += sgs.group_load;
-                sds->total_pwr += sg->sgp->power;
+                memset(sgs, 0, sizeof(*sgs));
+                update_sg_lb_stats(env, sg, load_idx, local_group, sgs);
 
                 /*
                  * In case the child domain prefers tasks go to siblings
@@ -4621,26 +4613,17 @@ static inline void update_sd_lb_stats(struct lb_env *env,
                  * heaviest group when it is already under-utilized (possible
                  * with a large weight task outweighs the tasks on the system).
                  */
-                if (prefer_sibling && !local_group && sds->this_has_capacity)
-                        sgs.group_capacity = min(sgs.group_capacity, 1UL);
+                if (prefer_sibling && !local_group &&
+                                sds->local && sds->local_stat.group_has_capacity)
+                        sgs->group_capacity = min(sgs->group_capacity, 1UL);
 
-                if (local_group) {
-                        sds->this_load = sgs.avg_load;
-                        sds->this = sg;
-                        sds->this_nr_running = sgs.sum_nr_running;
-                        sds->this_load_per_task = sgs.sum_weighted_load;
-                        sds->this_has_capacity = sgs.group_has_capacity;
-                        sds->this_idle_cpus = sgs.idle_cpus;
-                } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) {
-                        sds->max_load = sgs.avg_load;
+                /* Now, start updating sd_lb_stats */
+                sds->total_load += sgs->group_load;
+                sds->total_pwr += sg->sgp->power;
+
+                if (!local_group && update_sd_pick_busiest(env, sds, sg, sgs)) {
                         sds->busiest = sg;
-                        sds->busiest_nr_running = sgs.sum_nr_running;
-                        sds->busiest_idle_cpus = sgs.idle_cpus;
-                        sds->busiest_group_capacity = sgs.group_capacity;
-                        sds->busiest_load_per_task = sgs.sum_weighted_load;
-                        sds->busiest_has_capacity = sgs.group_has_capacity;
-                        sds->busiest_group_weight = sgs.group_weight;
-                        sds->group_imb = sgs.group_imb;
+                        sds->busiest_stat = *sgs;
                 }
 
                 sg = sg->next;
@@ -4684,8 +4667,8 @@ static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
         if (env->dst_cpu > busiest_cpu)
                 return 0;
 
-        env->imbalance = DIV_ROUND_CLOSEST(
-                sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE);
+        env->imbalance = DIV_ROUND_CLOSEST(sds->busiest_stat.avg_load *
+                                sds->busiest->sgp->power, SCHED_POWER_SCALE);
 
         return 1;
 }
@@ -4703,24 +4686,23 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
         unsigned long tmp, pwr_now = 0, pwr_move = 0;
         unsigned int imbn = 2;
         unsigned long scaled_busy_load_per_task;
+        struct sg_lb_stats *local, *busiest;
 
-        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(env->dst_cpu);
-        }
+        local = &sds->local_stat;
+        busiest = &sds->busiest_stat;
 
-        scaled_busy_load_per_task = sds->busiest_load_per_task
-                                         * SCHED_POWER_SCALE;
-        scaled_busy_load_per_task /= sds->busiest->sgp->power;
+        if (!local->sum_nr_running)
+                local->load_per_task = cpu_avg_load_per_task(env->dst_cpu);
+        else if (busiest->load_per_task > local->load_per_task)
+                imbn = 1;
 
-        if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
-                        (scaled_busy_load_per_task * imbn)) {
-                env->imbalance = sds->busiest_load_per_task;
+        scaled_busy_load_per_task =
+                (busiest->load_per_task * SCHED_POWER_SCALE) /
+                sds->busiest->sgp->power;
+
+        if (busiest->avg_load - local->avg_load + scaled_busy_load_per_task >=
+            (scaled_busy_load_per_task * imbn)) {
+                env->imbalance = busiest->load_per_task;
                 return;
         }
 
@@ -4731,33 +4713,36 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
          */
 
         pwr_now += sds->busiest->sgp->power *
-                        min(sds->busiest_load_per_task, sds->max_load);
-        pwr_now += sds->this->sgp->power *
-                        min(sds->this_load_per_task, sds->this_load);
+                        min(busiest->load_per_task, busiest->avg_load);
+        pwr_now += sds->local->sgp->power *
+                        min(local->load_per_task, local->avg_load);
         pwr_now /= SCHED_POWER_SCALE;
 
         /* Amount of load we'd subtract */
-        tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
+        tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
                 sds->busiest->sgp->power;
-        if (sds->max_load > tmp)
+        if (busiest->avg_load > tmp) {
                 pwr_move += sds->busiest->sgp->power *
-                        min(sds->busiest_load_per_task, sds->max_load - tmp);
+                            min(busiest->load_per_task,
+                                busiest->avg_load - tmp);
+        }
 
         /* Amount of load we'd add */
-        if (sds->max_load * sds->busiest->sgp->power <
-                sds->busiest_load_per_task * SCHED_POWER_SCALE)
-                tmp = (sds->max_load * sds->busiest->sgp->power) /
-                        sds->this->sgp->power;
-        else
-                tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) /
-                        sds->this->sgp->power;
-        pwr_move += sds->this->sgp->power *
-                        min(sds->this_load_per_task, sds->this_load + tmp);
+        if (busiest->avg_load * sds->busiest->sgp->power <
+            busiest->load_per_task * SCHED_POWER_SCALE) {
+                tmp = (busiest->avg_load * sds->busiest->sgp->power) /
+                        sds->local->sgp->power;
+        } else {
+                tmp = (busiest->load_per_task * SCHED_POWER_SCALE) /
+                        sds->local->sgp->power;
+        }
+        pwr_move += sds->local->sgp->power *
+                        min(local->load_per_task, local->avg_load + tmp);
         pwr_move /= SCHED_POWER_SCALE;
 
         /* Move if we gain throughput */
         if (pwr_move > pwr_now)
-                env->imbalance = sds->busiest_load_per_task;
+                env->imbalance = busiest->load_per_task;
 }
 
 /**
@@ -4769,11 +4754,22 @@ void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds)
 {
         unsigned long max_pull, load_above_capacity = ~0UL;
+        struct sg_lb_stats *local, *busiest;
+
+        local = &sds->local_stat;
+        if (local->sum_nr_running) {
+                local->load_per_task =
+                        local->sum_weighted_load / local->sum_nr_running;
+        }
 
-        sds->busiest_load_per_task /= sds->busiest_nr_running;
-        if (sds->group_imb) {
-                sds->busiest_load_per_task =
-                        min(sds->busiest_load_per_task, sds->avg_load);
+        busiest = &sds->busiest_stat;
+        /* busiest must have some tasks */
+        busiest->load_per_task =
+                busiest->sum_weighted_load / busiest->sum_nr_running;
+
+        if (busiest->group_imb) {
+                busiest->load_per_task =
+                        min(busiest->load_per_task, sds->avg_load);
         }
 
         /*
@@ -4781,20 +4777,19 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
          * max load less than avg load(as we skip the groups at or below
          * its cpu_power, while calculating max_load..)
          */
-        if (sds->max_load < sds->avg_load) {
+        if (busiest->avg_load < sds->avg_load) {
                 env->imbalance = 0;
                 return fix_small_imbalance(env, sds);
         }
 
-        if (!sds->group_imb) {
+        if (!busiest->group_imb) {
                 /*
                  * Don't want to pull so many tasks that a group would go idle.
                  */
-                load_above_capacity = (sds->busiest_nr_running -
-                                                sds->busiest_group_capacity);
+                load_above_capacity =
+                        (busiest->sum_nr_running - busiest->group_capacity);
 
                 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE);
-
                 load_above_capacity /= sds->busiest->sgp->power;
         }
 
@@ -4808,12 +4803,14 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
          * Be careful of negative numbers as they'll appear as very large values
          * with unsigned longs.
          */
-        max_pull = min(sds->max_load - sds->avg_load, load_above_capacity);
+        max_pull = min(busiest->avg_load - sds->avg_load,
+                       load_above_capacity);
 
         /* How much load to actually move to equalise the imbalance */
-        env->imbalance = min(max_pull * sds->busiest->sgp->power,
-                (sds->avg_load - sds->this_load) * sds->this->sgp->power)
-                        / SCHED_POWER_SCALE;
+        env->imbalance = min(
+                max_pull * sds->busiest->sgp->power,
+                (sds->avg_load - local->avg_load) * sds->local->sgp->power
+        ) / SCHED_POWER_SCALE;
 
         /*
          * if *imbalance is less than the average load per runnable task
@@ -4821,9 +4818,8 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
          * a think about bumping its value to force at least one task to be
          * moved
          */
-        if (env->imbalance < sds->busiest_load_per_task)
+        if (env->imbalance < busiest->load_per_task)
                 return fix_small_imbalance(env, sds);
-
 }
 
 /******* find_busiest_group() helpers end here *********************/
@@ -4845,9 +4841,9 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
  *                 return the least loaded group whose CPUs can be
  *                 put to idle by rebalancing its tasks onto our group.
  */
-static struct sched_group *
-find_busiest_group(struct lb_env *env)
+static struct sched_group *find_busiest_group(struct lb_env *env)
 {
+        struct sg_lb_stats *local, *busiest;
         struct sd_lb_stats sds;
 
         memset(&sds, 0, sizeof(sds));
@@ -4857,13 +4853,15 @@ find_busiest_group(struct lb_env *env)
          * this level.
          */
         update_sd_lb_stats(env, &sds);
+        local = &sds.local_stat;
+        busiest = &sds.busiest_stat;
 
         if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
             check_asym_packing(env, &sds))
                 return sds.busiest;
 
         /* There is no busy sibling group to pull tasks from */
-        if (!sds.busiest || sds.busiest_nr_running == 0)
+        if (!sds.busiest || busiest->sum_nr_running == 0)
                 goto out_balanced;
 
         sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr;
@@ -4873,26 +4871,26 @@ find_busiest_group(struct lb_env *env)
          * work because they assumes all things are equal, which typically
          * isn't true due to cpus_allowed constraints and the like.
          */
-        if (sds.group_imb)
+        if (busiest->group_imb)
                 goto force_balance;
 
         /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
-        if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
-                        !sds.busiest_has_capacity)
+        if (env->idle == CPU_NEWLY_IDLE && local->group_has_capacity &&
+            !busiest->group_has_capacity)
                 goto force_balance;
 
         /*
          * If the local group is more busy than the selected busiest group
          * don't try and pull any tasks.
          */
-        if (sds.this_load >= sds.max_load)
+        if (local->avg_load >= busiest->avg_load)
                 goto out_balanced;
 
         /*
          * Don't pull any tasks if this group is already above the domain
          * average load.
          */
-        if (sds.this_load >= sds.avg_load)
+        if (local->avg_load >= sds.avg_load)
                 goto out_balanced;
 
         if (env->idle == CPU_IDLE) {
@@ -4902,15 +4900,16 @@ find_busiest_group(struct lb_env *env)
                  * there is no imbalance between this and busiest group
                  * wrt to idle cpu's, it is balanced.
                  */
-                if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) &&
-                    sds.busiest_nr_running <= sds.busiest_group_weight)
+                if ((local->idle_cpus < busiest->idle_cpus) &&
+                    busiest->sum_nr_running <= busiest->group_weight)
                         goto out_balanced;
         } else {
                 /*
                  * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use
                  * imbalance_pct to be conservative.
                  */
-                if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load)
+                if (100 * busiest->avg_load <=
+                                env->sd->imbalance_pct * local->avg_load)
                         goto out_balanced;
         }