5 files changed, 135 insertions, 57 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 52288a647692..639241f4f3d1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -829,11 +829,14 @@ struct sched_class {
         void (*put_prev_task) (struct rq *rq, struct task_struct *p);
 
         unsigned long (*load_balance) (struct rq *this_rq, int this_cpu,
-                        struct rq *busiest,
-                        unsigned long max_nr_move, unsigned long max_load_move,
+                        struct rq *busiest, unsigned long max_load_move,
                         struct sched_domain *sd, enum cpu_idle_type idle,
                         int *all_pinned, int *this_best_prio);
 
+        int (*move_one_task) (struct rq *this_rq, int this_cpu,
+                              struct rq *busiest, struct sched_domain *sd,
+                              enum cpu_idle_type idle);
+
         void (*set_curr_task) (struct rq *rq);
         void (*task_tick) (struct rq *rq, struct task_struct *p);
         void (*task_new) (struct rq *rq, struct task_struct *p);
diff --git a/kernel/sched.c b/kernel/sched.c
index cc9cd5b710a6..8607795fad69 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -838,11 +838,35 @@ struct rq_iterator {
         struct task_struct *(*next)(void *);
 };
 
-static int balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                      unsigned long max_nr_move, unsigned long max_load_move,
-                      struct sched_domain *sd, enum cpu_idle_type idle,
-                      int *all_pinned, unsigned long *load_moved,
-                      int *this_best_prio, struct rq_iterator *iterator);
+#ifdef CONFIG_SMP
+static unsigned long
+balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
+              unsigned long max_load_move, struct sched_domain *sd,
+              enum cpu_idle_type idle, int *all_pinned,
+              int *this_best_prio, struct rq_iterator *iterator);
+
+static int
+iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                   struct sched_domain *sd, enum cpu_idle_type idle,
+                   struct rq_iterator *iterator);
+#else
+static inline unsigned long
+balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
+              unsigned long max_load_move, struct sched_domain *sd,
+              enum cpu_idle_type idle, int *all_pinned,
+              int *this_best_prio, struct rq_iterator *iterator)
+{
+        return 0;
+}
+
+static inline int
+iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                   struct sched_domain *sd, enum cpu_idle_type idle,
+                   struct rq_iterator *iterator)
+{
+        return 0;
+}
+#endif
 
 #include "sched_stats.h"
 #include "sched_idletask.c"
@@ -2224,17 +2248,17 @@ int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
         return 1;
 }
 
-static int balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                      unsigned long max_nr_move, unsigned long max_load_move,
-                      struct sched_domain *sd, enum cpu_idle_type idle,
-                      int *all_pinned, unsigned long *load_moved,
-                      int *this_best_prio, struct rq_iterator *iterator)
+static unsigned long
+balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
+              unsigned long max_load_move, struct sched_domain *sd,
+              enum cpu_idle_type idle, int *all_pinned,
+              int *this_best_prio, struct rq_iterator *iterator)
 {
         int pulled = 0, pinned = 0, skip_for_load;
         struct task_struct *p;
         long rem_load_move = max_load_move;
 
-        if (max_nr_move == 0 || max_load_move == 0)
+        if (max_load_move == 0)
                 goto out;
 
         pinned = 1;
@@ -2267,7 +2291,7 @@ next:
          * We only want to steal up to the prescribed number of tasks
          * and the prescribed amount of weighted load.
          */
-        if (pulled < max_nr_move && rem_load_move > 0) {
+        if (rem_load_move > 0) {
                 if (p->prio < *this_best_prio)
                         *this_best_prio = p->prio;
                 p = iterator->next(iterator->arg);
@@ -2275,7 +2299,7 @@ next:
         }
 out:
         /*
-         * Right now, this is the only place pull_task() is called,
+         * Right now, this is one of only two places pull_task() is called,
          * so we can safely collect pull_task() stats here rather than
          * inside pull_task().
          */
@@ -2283,8 +2307,8 @@ out:
 
         if (all_pinned)
                 *all_pinned = pinned;
-        *load_moved = max_load_move - rem_load_move;
-        return pulled;
+
+        return max_load_move - rem_load_move;
 }
 
 /*
@@ -2306,7 +2330,7 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
         do {
                 total_load_moved +=
                         class->load_balance(this_rq, this_cpu, busiest,
-                                ULONG_MAX, max_load_move - total_load_moved,
+                                max_load_move - total_load_moved,
                                 sd, idle, all_pinned, &this_best_prio);
                 class = class->next;
         } while (class && max_load_move > total_load_moved);
@@ -2314,6 +2338,32 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
         return total_load_moved > 0;
 }
 
+static int
+iter_move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                   struct sched_domain *sd, enum cpu_idle_type idle,
+                   struct rq_iterator *iterator)
+{
+        struct task_struct *p = iterator->start(iterator->arg);
+        int pinned = 0;
+
+        while (p) {
+                if (can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) {
+                        pull_task(busiest, p, this_rq, this_cpu);
+                        /*
+                         * Right now, this is only the second place pull_task()
+                         * is called, so we can safely collect pull_task()
+                         * stats here rather than inside pull_task().
+                         */
+                        schedstat_inc(sd, lb_gained[idle]);
+
+                        return 1;
+                }
+                p = iterator->next(iterator->arg);
+        }
+
+        return 0;
+}
+
 /*
  * move_one_task tries to move exactly one task from busiest to this_rq, as
  * part of active balancing operations within "domain".
@@ -2325,12 +2375,9 @@ static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
                          struct sched_domain *sd, enum cpu_idle_type idle)
 {
         const struct sched_class *class;
-        int this_best_prio = MAX_PRIO;
 
         for (class = sched_class_highest; class; class = class->next)
-                if (class->load_balance(this_rq, this_cpu, busiest,
-                                        1, ULONG_MAX, sd, idle, NULL,
-                                        &this_best_prio))
+                if (class->move_one_task(this_rq, this_cpu, busiest, sd, idle))
                         return 1;
 
         return 0;
@@ -3267,18 +3314,6 @@ static inline void idle_balance(int cpu, struct rq *rq)
 {
 }
 
-/* Avoid "used but not defined" warning on UP */
-static int balance_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                      unsigned long max_nr_move, unsigned long max_load_move,
-                      struct sched_domain *sd, enum cpu_idle_type idle,
-                      int *all_pinned, unsigned long *load_moved,
-                      int *this_best_prio, struct rq_iterator *iterator)
-{
-        *load_moved = 0;
-
-        return 0;
-}
-
 #endif
 
 DEFINE_PER_CPU(struct kernel_stat, kstat);
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 166ed6db600b..a90d0457d603 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -936,12 +936,11 @@ static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
 
 static unsigned long
 load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                  unsigned long max_nr_move, unsigned long max_load_move,
+                  unsigned long max_load_move,
                   struct sched_domain *sd, enum cpu_idle_type idle,
                   int *all_pinned, int *this_best_prio)
 {
         struct cfs_rq *busy_cfs_rq;
-        unsigned long load_moved, total_nr_moved = 0, nr_moved;
         long rem_load_move = max_load_move;
         struct rq_iterator cfs_rq_iterator;
 
@@ -969,25 +968,47 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
 #else
 # define maxload rem_load_move
 #endif
-                /* pass busy_cfs_rq argument into
+                /*
+                 * pass busy_cfs_rq argument into
                  * load_balance_[start|next]_fair iterators
                  */
                 cfs_rq_iterator.arg = busy_cfs_rq;
-                nr_moved = balance_tasks(this_rq, this_cpu, busiest,
-                                max_nr_move, maxload, sd, idle, all_pinned,
-                                &load_moved, this_best_prio, &cfs_rq_iterator);
-
-                total_nr_moved += nr_moved;
-                max_nr_move -= nr_moved;
-                rem_load_move -= load_moved;
+                rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
+                                               maxload, sd, idle, all_pinned,
+                                               this_best_prio,
+                                               &cfs_rq_iterator);
 
-                if (max_nr_move <= 0 || rem_load_move <= 0)
+                if (rem_load_move <= 0)
                         break;
         }
 
         return max_load_move - rem_load_move;
 }
 
+static int
+move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                   struct sched_domain *sd, enum cpu_idle_type idle)
+{
+        struct cfs_rq *busy_cfs_rq;
+        struct rq_iterator cfs_rq_iterator;
+
+        cfs_rq_iterator.start = load_balance_start_fair;
+        cfs_rq_iterator.next = load_balance_next_fair;
+
+        for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
+                /*
+                 * pass busy_cfs_rq argument into
+                 * load_balance_[start|next]_fair iterators
+                 */
+                cfs_rq_iterator.arg = busy_cfs_rq;
+                if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
+                                       &cfs_rq_iterator))
+                    return 1;
+        }
+
+        return 0;
+}
+
 /*
  * scheduler tick hitting a task of our scheduling class:
  */
@@ -1064,6 +1085,7 @@ static const struct sched_class fair_sched_class = {
         .put_prev_task          = put_prev_task_fair,
 
         .load_balance           = load_balance_fair,
+        .move_one_task          = move_one_task_fair,
 
         .set_curr_task          = set_curr_task_fair,
         .task_tick              = task_tick_fair,
diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index 6e2ead41516e..586b06ca30aa 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -39,9 +39,16 @@ static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
 
 static unsigned long
 load_balance_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                        unsigned long max_nr_move, unsigned long max_load_move,
-                        struct sched_domain *sd, enum cpu_idle_type idle,
-                        int *all_pinned, int *this_best_prio)
+                  unsigned long max_load_move,
+                  struct sched_domain *sd, enum cpu_idle_type idle,
+                  int *all_pinned, int *this_best_prio)
+{
+        return 0;
+}
+
+static int
+move_one_task_idle(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                   struct sched_domain *sd, enum cpu_idle_type idle)
 {
         return 0;
 }
@@ -70,6 +77,7 @@ const struct sched_class idle_sched_class = {
         .put_prev_task          = put_prev_task_idle,
 
         .load_balance           = load_balance_idle,
+        .move_one_task          = move_one_task_idle,
 
         .set_curr_task          = set_curr_task_idle,
         .task_tick              = task_tick_idle,
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index d0097a0634e5..e9395b7119e6 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -172,13 +172,11 @@ static struct task_struct *load_balance_next_rt(void *arg)
 
 static unsigned long
 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
-                        unsigned long max_nr_move, unsigned long max_load_move,
-                        struct sched_domain *sd, enum cpu_idle_type idle,
-                        int *all_pinned, int *this_best_prio)
+                unsigned long max_load_move,
+                struct sched_domain *sd, enum cpu_idle_type idle,
+                int *all_pinned, int *this_best_prio)
 {
-        int nr_moved;
         struct rq_iterator rt_rq_iterator;
-        unsigned long load_moved;
 
         rt_rq_iterator.start = load_balance_start_rt;
         rt_rq_iterator.next = load_balance_next_rt;
@@ -187,11 +185,22 @@ load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
          */
         rt_rq_iterator.arg = busiest;
 
-        nr_moved = balance_tasks(this_rq, this_cpu, busiest, max_nr_move,
-                        max_load_move, sd, idle, all_pinned, &load_moved,
-                        this_best_prio, &rt_rq_iterator);
+        return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd,
+                             idle, all_pinned, this_best_prio, &rt_rq_iterator);
+}
+
+static int
+move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
+                 struct sched_domain *sd, enum cpu_idle_type idle)
+{
+        struct rq_iterator rt_rq_iterator;
+
+        rt_rq_iterator.start = load_balance_start_rt;
+        rt_rq_iterator.next = load_balance_next_rt;
+        rt_rq_iterator.arg = busiest;
 
-        return load_moved;
+        return iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
+                                  &rt_rq_iterator);
 }
 
 static void task_tick_rt(struct rq *rq, struct task_struct *p)
@@ -237,6 +246,7 @@ const struct sched_class rt_sched_class = {
         .put_prev_task          = put_prev_task_rt,
 
         .load_balance           = load_balance_rt,
+        .move_one_task          = move_one_task_rt,
 
         .set_curr_task          = set_curr_task_rt,
         .task_tick              = task_tick_rt,