1 files changed, 25 insertions, 3 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3656480e0f79..032b548be0fc 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1764,6 +1764,10 @@ static void pull_task(struct rq *src_rq, struct task_struct *p,
         set_task_cpu(p, this_cpu);
         activate_task(this_rq, p, 0);
         check_preempt_curr(this_rq, p, 0);
+
+        /* re-arm NEWIDLE balancing when moving tasks */
+        src_rq->avg_idle = this_rq->avg_idle = 2*sysctl_sched_migration_cost;
+        this_rq->idle_stamp = 0;
 }
 
 /*
@@ -2030,12 +2034,14 @@ struct sd_lb_stats {
         unsigned long this_load;
         unsigned long this_load_per_task;
         unsigned long this_nr_running;
+        unsigned long this_has_capacity;
 
         /* Statistics of the busiest group */
         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;
 
         int group_imb; /* Is there imbalance in this sd */
 #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
@@ -2058,6 +2064,7 @@ struct sg_lb_stats {
         unsigned long sum_weighted_load; /* Weighted load of group's tasks */
         unsigned long group_capacity;
         int group_imb; /* Is there an imbalance in the group ? */
+        int group_has_capacity; /* Is there extra capacity in the group? */
 };
 
 /**
@@ -2456,6 +2463,9 @@ static inline void update_sg_lb_stats(struct sched_domain *sd,
         sgs->group_capacity = DIV_ROUND_CLOSEST(group->cpu_power, SCHED_LOAD_SCALE);
         if (!sgs->group_capacity)
                 sgs->group_capacity = fix_small_capacity(sd, group);
+
+        if (sgs->group_capacity > sgs->sum_nr_running)
+                sgs->group_has_capacity = 1;
 }
 
 /**
@@ -2554,12 +2564,14 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
                         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;
                 } else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) {
                         sds->max_load = sgs.avg_load;
                         sds->busiest = sg;
                         sds->busiest_nr_running = sgs.sum_nr_running;
                         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->group_imb = sgs.group_imb;
                 }
 
@@ -2756,6 +2768,7 @@ static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
                 return fix_small_imbalance(sds, this_cpu, imbalance);
 
 }
+
 /******* find_busiest_group() helpers end here *********************/
 
 /**
@@ -2807,6 +2820,11 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
          * 4) This group is more busy than the avg busieness at this
          *    sched_domain.
          * 5) The imbalance is within the specified limit.
+         *
+         * Note: when doing newidle balance, if the local group has excess
+         * capacity (i.e. nr_running < group_capacity) and the busiest group
+         * does not have any capacity, we force a load balance to pull tasks
+         * to the local group. In this case, we skip past checks 3, 4 and 5.
          */
         if (!(*balance))
                 goto ret;
@@ -2818,6 +2836,11 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
         if (!sds.busiest || sds.busiest_nr_running == 0)
                 goto out_balanced;
 
+        /*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
+        if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
+                        !sds.busiest_has_capacity)
+                goto force_balance;
+
         if (sds.this_load >= sds.max_load)
                 goto out_balanced;
 
@@ -2829,6 +2852,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
         if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
                 goto out_balanced;
 
+force_balance:
         /* Looks like there is an imbalance. Compute it */
         calculate_imbalance(&sds, this_cpu, imbalance);
         return sds.busiest;
@@ -3162,10 +3186,8 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                 interval = msecs_to_jiffies(sd->balance_interval);
                 if (time_after(next_balance, sd->last_balance + interval))
                         next_balance = sd->last_balance + interval;
-                if (pulled_task) {
-                        this_rq->idle_stamp = 0;
+                if (pulled_task)
                         break;
-                }
         }
 
         raw_spin_lock(&this_rq->lock);