sched: Define structure to store the sched_domain statistics for fbg()

Impact: cleanup

Currently we use a lot of local variables in find_busiest_group()
to capture the various statistics related to the sched_domain.
Group them together into a single data structure.

This will help us to offload the job of updating the sched_domain
statistics to a helper function.

Credit: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Acked-by: Peter 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: <20090325091356.13992.25970.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 121 insertions, 86 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 1893d5562f5f..8198dbe8e4aa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3190,6 +3190,37 @@ static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
         return 0;
 }
 /********** 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;
+
+        /* Statistics of the busiest group */
+        unsigned long max_load;
+        unsigned long busiest_load_per_task;
+        unsigned long busiest_nr_running;
+
+        int group_imb; /* Is there imbalance in this sd */
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+        int power_savings_balance; /* Is powersave balance needed for this sd */
+        struct sched_group *group_min; /* Least loaded group in sd */
+        struct sched_group *group_leader; /* Group which relieves group_min */
+        unsigned long min_load_per_task; /* load_per_task in group_min */
+        unsigned long leader_nr_running; /* Nr running of group_leader */
+        unsigned long min_nr_running; /* Nr running of group_min */
+#endif
+};
 
 /**
  * sg_lb_stats - stats of a sched_group required for load_balancing
@@ -3346,23 +3377,16 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
                    unsigned long *imbalance, enum cpu_idle_type idle,
                    int *sd_idle, const struct cpumask *cpus, int *balance)
 {
-        struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
-        unsigned long max_load, avg_load, total_load, this_load, total_pwr;
+        struct sd_lb_stats sds;
+        struct sched_group *group = sd->groups;
         unsigned long max_pull;
-        unsigned long busiest_load_per_task, busiest_nr_running;
-        unsigned long this_load_per_task, this_nr_running;
-        int load_idx, group_imb = 0;
+        int load_idx;
+
+        memset(&sds, 0, sizeof(sds));
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
-        int power_savings_balance = 1;
-        unsigned long leader_nr_running = 0, min_load_per_task = 0;
-        unsigned long min_nr_running = ULONG_MAX;
-        struct sched_group *group_min = NULL, *group_leader = NULL;
+        sds.power_savings_balance = 1;
+        sds.min_nr_running = ULONG_MAX;
 #endif
-
-        max_load = this_load = total_load = total_pwr = 0;
-        busiest_load_per_task = busiest_nr_running = 0;
-        this_load_per_task = this_nr_running = 0;
-
         load_idx = get_sd_load_idx(sd, idle);
 
         do {
@@ -3378,22 +3402,22 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
                 if (balance && !(*balance))
                         goto ret;
 
-                total_load += sgs.group_load;
-                total_pwr += group->__cpu_power;
+                sds.total_load += sgs.group_load;
+                sds.total_pwr += group->__cpu_power;
 
                 if (local_group) {
-                        this_load = sgs.avg_load;
-                        this = group;
-                        this_nr_running = sgs.sum_nr_running;
-                        this_load_per_task = sgs.sum_weighted_load;
-                } else if (sgs.avg_load > max_load &&
+                        sds.this_load = sgs.avg_load;
+                        sds.this = group;
+                        sds.this_nr_running = sgs.sum_nr_running;
+                        sds.this_load_per_task = sgs.sum_weighted_load;
+                } else if (sgs.avg_load > sds.max_load &&
                            (sgs.sum_nr_running > sgs.group_capacity ||
                                 sgs.group_imb)) {
-                        max_load = sgs.avg_load;
-                        busiest = group;
-                        busiest_nr_running = sgs.sum_nr_running;
-                        busiest_load_per_task = sgs.sum_weighted_load;
-                        group_imb = sgs.group_imb;
+                        sds.max_load = sgs.avg_load;
+                        sds.busiest = group;
+                        sds.busiest_nr_running = sgs.sum_nr_running;
+                        sds.busiest_load_per_task = sgs.sum_weighted_load;
+                        sds.group_imb = sgs.group_imb;
                 }
 
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
@@ -3409,15 +3433,16 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
                  * If the local group is idle or completely loaded
                  * no need to do power savings balance at this domain
                  */
-                if (local_group && (this_nr_running >= sgs.group_capacity ||
-                                    !this_nr_running))
-                        power_savings_balance = 0;
+                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 (!power_savings_balance ||
+                if (!sds.power_savings_balance ||
                         sgs.sum_nr_running >= sgs.group_capacity ||
                         !sgs.sum_nr_running)
                         goto group_next;
@@ -3427,12 +3452,13 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
                  * This is the group from where we need to pick up the load
                  * for saving power
                  */
-                if ((sgs.sum_nr_running < min_nr_running) ||
-                    (sgs.sum_nr_running == min_nr_running &&
-                     group_first_cpu(group) > group_first_cpu(group_min))) {
-                        group_min = group;
-                        min_nr_running = sgs.sum_nr_running;
-                        min_load_per_task = sgs.sum_weighted_load /
+                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;
                 }
 
@@ -3444,29 +3470,32 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
                 if (sgs.sum_nr_running > sgs.group_capacity - 1)
                         goto group_next;
 
-                if (sgs.sum_nr_running > leader_nr_running ||
-                    (sgs.sum_nr_running == leader_nr_running &&
-                     group_first_cpu(group) < group_first_cpu(group_leader))) {
-                        group_leader = group;
-                        leader_nr_running = sgs.sum_nr_running;
+                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
                 group = group->next;
         } while (group != sd->groups);
 
-        if (!busiest || this_load >= max_load || busiest_nr_running == 0)
+        if (!sds.busiest || sds.this_load >= sds.max_load
+                || sds.busiest_nr_running == 0)
                 goto out_balanced;
 
-        avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
+        sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
 
-        if (this_load >= avg_load ||
-                        100*max_load <= sd->imbalance_pct*this_load)
+        if (sds.this_load >= sds.avg_load ||
+                        100*sds.max_load <= sd->imbalance_pct * sds.this_load)
                 goto out_balanced;
 
-        busiest_load_per_task /= busiest_nr_running;
-        if (group_imb)
-                busiest_load_per_task = min(busiest_load_per_task, avg_load);
+        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);
 
         /*
          * We're trying to get all the cpus to the average_load, so we don't
@@ -3479,7 +3508,7 @@ group_next:
          * by pulling tasks to us. Be careful of negative numbers as they'll
          * appear as very large values with unsigned longs.
          */
-        if (max_load <= busiest_load_per_task)
+        if (sds.max_load <= sds.busiest_load_per_task)
                 goto out_balanced;
 
         /*
@@ -3487,17 +3516,18 @@ group_next:
          * max load less than avg load(as we skip the groups at or below
          * its cpu_power, while calculating max_load..)
          */
-        if (max_load < avg_load) {
+        if (sds.max_load < sds.avg_load) {
                 *imbalance = 0;
                 goto small_imbalance;
         }
 
         /* Don't want to pull so many tasks that a group would go idle */
-        max_pull = min(max_load - avg_load, max_load - busiest_load_per_task);
+        max_pull = min(sds.max_load - sds.avg_load,
+                        sds.max_load - sds.busiest_load_per_task);
 
         /* How much load to actually move to equalise the imbalance */
-        *imbalance = min(max_pull * busiest->__cpu_power,
-                                (avg_load - this_load) * this->__cpu_power)
+        *imbalance = min(max_pull * sds.busiest->__cpu_power,
+                        (sds.avg_load - sds.this_load) * sds.this->__cpu_power)
                         / SCHED_LOAD_SCALE;
 
         /*
@@ -3506,24 +3536,27 @@ group_next:
          * a think about bumping its value to force at least one task to be
          * moved
          */
-        if (*imbalance < busiest_load_per_task) {
+        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 (this_nr_running) {
-                        this_load_per_task /= this_nr_running;
-                        if (busiest_load_per_task > this_load_per_task)
+                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
-                        this_load_per_task = cpu_avg_load_per_task(this_cpu);
-
-                if (max_load - this_load + busiest_load_per_task >=
-                                        busiest_load_per_task * imbn) {
-                        *imbalance = busiest_load_per_task;
-                        return busiest;
+                        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;
                 }
 
                 /*
@@ -3532,52 +3565,54 @@ small_imbalance:
                  * moving them.
                  */
 
-                pwr_now += busiest->__cpu_power *
-                                min(busiest_load_per_task, max_load);
-                pwr_now += this->__cpu_power *
-                                min(this_load_per_task, this_load);
+                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(busiest,
-                                busiest_load_per_task * SCHED_LOAD_SCALE);
-                if (max_load > tmp)
-                        pwr_move += busiest->__cpu_power *
-                                min(busiest_load_per_task, max_load - tmp);
+                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 (max_load * busiest->__cpu_power <
-                                busiest_load_per_task * SCHED_LOAD_SCALE)
-                        tmp = sg_div_cpu_power(this,
-                                        max_load * 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);
                 else
-                        tmp = sg_div_cpu_power(this,
-                                busiest_load_per_task * SCHED_LOAD_SCALE);
-                pwr_move += this->__cpu_power *
-                                min(this_load_per_task, this_load + tmp);
+                        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 = busiest_load_per_task;
+                        *imbalance = sds.busiest_load_per_task;
         }
 
-        return busiest;
+        return sds.busiest;
 
 out_balanced:
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
         if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
                 goto ret;
 
-        if (this != group_leader || group_leader == group_min)
+        if (sds.this != sds.group_leader || sds.group_leader == sds.group_min)
                 goto ret;
 
-        *imbalance = min_load_per_task;
+        *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(group_leader);
+                        group_first_cpu(sds.group_leader);
         }
-        return group_min;
+        return sds.group_min;
 
 #endif
 ret: