Merge master.kernel.org:/home/rmk/linux-2.6-arm
[linux-2.6.git] / kernel / sched_fair.c
index a32df15..5a5ea2c 100644 (file)
@@ -21,6 +21,7 @@
  */
 
 #include <linux/latencytop.h>
+#include <linux/sched.h>
 
 /*
  * Targeted preemption latency for CPU-bound tasks:
  *  run vmstat and monitor the context-switches (cs) field)
  */
 unsigned int sysctl_sched_latency = 5000000ULL;
+unsigned int normalized_sysctl_sched_latency = 5000000ULL;
+
+/*
+ * The initial- and re-scaling of tunables is configurable
+ * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
+ *
+ * Options are:
+ * SCHED_TUNABLESCALING_NONE - unscaled, always *1
+ * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
+ * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
+ */
+enum sched_tunable_scaling sysctl_sched_tunable_scaling
+       = SCHED_TUNABLESCALING_LOG;
 
 /*
  * Minimal preemption granularity for CPU-bound tasks:
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
 unsigned int sysctl_sched_min_granularity = 1000000ULL;
+unsigned int normalized_sysctl_sched_min_granularity = 1000000ULL;
 
 /*
  * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
@@ -70,6 +85,7 @@ unsigned int __read_mostly sysctl_sched_compat_yield;
  * have immediate wakeup/sleep latencies.
  */
 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
+unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
 
 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
 
@@ -383,11 +399,12 @@ static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
  */
 
 #ifdef CONFIG_SCHED_DEBUG
-int sched_nr_latency_handler(struct ctl_table *table, int write,
+int sched_proc_update_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *lenp,
                loff_t *ppos)
 {
        int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+       int factor = get_update_sysctl_factor();
 
        if (ret || !write)
                return ret;
@@ -395,6 +412,14 @@ int sched_nr_latency_handler(struct ctl_table *table, int write,
        sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
                                        sysctl_sched_min_granularity);
 
+#define WRT_SYSCTL(name) \
+       (normalized_sysctl_##name = sysctl_##name / (factor))
+       WRT_SYSCTL(sched_min_granularity);
+       WRT_SYSCTL(sched_latency);
+       WRT_SYSCTL(sched_wakeup_granularity);
+       WRT_SYSCTL(sched_shares_ratelimit);
+#undef WRT_SYSCTL
+
        return 0;
 }
 #endif
@@ -485,6 +510,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
        curr->sum_exec_runtime += delta_exec;
        schedstat_add(cfs_rq, exec_clock, delta_exec);
        delta_exec_weighted = calc_delta_fair(delta_exec, curr);
+
        curr->vruntime += delta_exec_weighted;
        update_min_vruntime(cfs_rq);
 }
@@ -740,16 +766,26 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
        se->vruntime = vruntime;
 }
 
+#define ENQUEUE_WAKEUP 1
+#define ENQUEUE_MIGRATE 2
+
 static void
-enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
+enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 {
        /*
+        * Update the normalized vruntime before updating min_vruntime
+        * through callig update_curr().
+        */
+       if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATE))
+               se->vruntime += cfs_rq->min_vruntime;
+
+       /*
         * Update run-time statistics of the 'current'.
         */
        update_curr(cfs_rq);
        account_entity_enqueue(cfs_rq, se);
 
-       if (wakeup) {
+       if (flags & ENQUEUE_WAKEUP) {
                place_entity(cfs_rq, se, 0);
                enqueue_sleeper(cfs_rq, se);
        }
@@ -803,6 +839,14 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
                __dequeue_entity(cfs_rq, se);
        account_entity_dequeue(cfs_rq, se);
        update_min_vruntime(cfs_rq);
+
+       /*
+        * Normalize the entity after updating the min_vruntime because the
+        * update can refer to the ->curr item and we need to reflect this
+        * movement in our normalized position.
+        */
+       if (!sleep)
+               se->vruntime -= cfs_rq->min_vruntime;
 }
 
 /*
@@ -822,6 +866,26 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
                 * re-elected due to buddy favours.
                 */
                clear_buddies(cfs_rq, curr);
+               return;
+       }
+
+       /*
+        * Ensure that a task that missed wakeup preemption by a
+        * narrow margin doesn't have to wait for a full slice.
+        * This also mitigates buddy induced latencies under load.
+        */
+       if (!sched_feat(WAKEUP_PREEMPT))
+               return;
+
+       if (delta_exec < sysctl_sched_min_granularity)
+               return;
+
+       if (cfs_rq->nr_running > 1) {
+               struct sched_entity *se = __pick_next_entity(cfs_rq);
+               s64 delta = curr->vruntime - se->vruntime;
+
+               if (delta > ideal_runtime)
+                       resched_task(rq_of(cfs_rq)->curr);
        }
 }
 
@@ -861,12 +925,18 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
 {
        struct sched_entity *se = __pick_next_entity(cfs_rq);
+       struct sched_entity *left = se;
+
+       if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
+               se = cfs_rq->next;
 
-       if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1)
-               return cfs_rq->next;
+       /*
+        * Prefer last buddy, try to return the CPU to a preempted task.
+        */
+       if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
+               se = cfs_rq->last;
 
-       if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1)
-               return cfs_rq->last;
+       clear_buddies(cfs_rq, se);
 
        return se;
 }
@@ -983,17 +1053,24 @@ static inline void hrtick_update(struct rq *rq)
  * increased. Here we update the fair scheduling stats and
  * then put the task into the rbtree:
  */
-static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
+static void
+enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup, bool head)
 {
        struct cfs_rq *cfs_rq;
        struct sched_entity *se = &p->se;
+       int flags = 0;
+
+       if (wakeup)
+               flags |= ENQUEUE_WAKEUP;
+       if (p->state == TASK_WAKING)
+               flags |= ENQUEUE_MIGRATE;
 
        for_each_sched_entity(se) {
                if (se->on_rq)
                        break;
                cfs_rq = cfs_rq_of(se);
-               enqueue_entity(cfs_rq, se, wakeup);
-               wakeup = 1;
+               enqueue_entity(cfs_rq, se, flags);
+               flags = ENQUEUE_WAKEUP;
        }
 
        hrtick_update(rq);
@@ -1069,6 +1146,14 @@ static void yield_task_fair(struct rq *rq)
 
 #ifdef CONFIG_SMP
 
+static void task_waking_fair(struct rq *rq, struct task_struct *p)
+{
+       struct sched_entity *se = &p->se;
+       struct cfs_rq *cfs_rq = cfs_rq_of(se);
+
+       se->vruntime -= cfs_rq->min_vruntime;
+}
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /*
  * effective_load() calculates the load change as seen from the root_task_group
@@ -1333,20 +1418,16 @@ select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target)
         * test in select_task_rq_fair) and the prev_cpu is idle then that's
         * always a better target than the current cpu.
         */
-       if (target == cpu) {
-               if (!cpu_rq(prev_cpu)->cfs.nr_running)
-                       target = prev_cpu;
-       }
+       if (target == cpu && !cpu_rq(prev_cpu)->cfs.nr_running)
+               return prev_cpu;
 
        /*
         * Otherwise, iterate the domain and find an elegible idle cpu.
         */
-       if (target == -1 || target == cpu) {
-               for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
-                       if (!cpu_rq(i)->cfs.nr_running) {
-                               target = i;
-                               break;
-                       }
+       for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {
+               if (!cpu_rq(i)->cfs.nr_running) {
+                       target = i;
+                       break;
                }
        }
 
@@ -1381,8 +1462,10 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                new_cpu = prev_cpu;
        }
 
-       rcu_read_lock();
        for_each_domain(cpu, tmp) {
+               if (!(tmp->flags & SD_LOAD_BALANCE))
+                       continue;
+
                /*
                 * If power savings logic is enabled for a domain, see if we
                 * are not overloaded, if so, don't balance wider.
@@ -1407,7 +1490,12 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                                want_sd = 0;
                }
 
-               if (want_affine && (tmp->flags & SD_WAKE_AFFINE)) {
+               /*
+                * While iterating the domains looking for a spanning
+                * WAKE_AFFINE domain, adjust the affine target to any idle cpu
+                * in cache sharing domains along the way.
+                */
+               if (want_affine) {
                        int target = -1;
 
                        /*
@@ -1420,17 +1508,15 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                        /*
                         * If there's an idle sibling in this domain, make that
                         * the wake_affine target instead of the current cpu.
-                        *
-                        * XXX: should we possibly do this outside of
-                        * WAKE_AFFINE, in case the shared cache domain is
-                        * smaller than the WAKE_AFFINE domain?
                         */
-                       if (tmp->flags & SD_PREFER_SIBLING)
+                       if (tmp->flags & SD_SHARE_PKG_RESOURCES)
                                target = select_idle_sibling(p, tmp, target);
 
                        if (target >= 0) {
-                               affine_sd = tmp;
-                               want_affine = 0;
+                               if (tmp->flags & SD_WAKE_AFFINE) {
+                                       affine_sd = tmp;
+                                       want_affine = 0;
+                               }
                                cpu = target;
                        }
                }
@@ -1459,10 +1545,8 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                        update_shares(tmp);
        }
 
-       if (affine_sd && wake_affine(affine_sd, p, sync)) {
-               new_cpu = cpu;
-               goto out;
-       }
+       if (affine_sd && wake_affine(affine_sd, p, sync))
+               return cpu;
 
        while (sd) {
                int load_idx = sd->forkexec_idx;
@@ -1503,8 +1587,6 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag
                /* while loop will break here if sd == NULL */
        }
 
-out:
-       rcu_read_unlock();
        return new_cpu;
 }
 #endif /* CONFIG_SMP */
@@ -1624,13 +1706,10 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
        struct sched_entity *se = &curr->se, *pse = &p->se;
        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
        int sync = wake_flags & WF_SYNC;
+       int scale = cfs_rq->nr_running >= sched_nr_latency;
 
-       update_curr(cfs_rq);
-
-       if (unlikely(rt_prio(p->prio))) {
-               resched_task(curr);
-               return;
-       }
+       if (unlikely(rt_prio(p->prio)))
+               goto preempt;
 
        if (unlikely(p->sched_class != &fair_sched_class))
                return;
@@ -1638,18 +1717,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
        if (unlikely(se == pse))
                return;
 
-       /*
-        * Only set the backward buddy when the current task is still on the
-        * rq. This can happen when a wakeup gets interleaved with schedule on
-        * the ->pre_schedule() or idle_balance() point, either of which can
-        * drop the rq lock.
-        *
-        * Also, during early boot the idle thread is in the fair class, for
-        * obvious reasons its a bad idea to schedule back to the idle thread.
-        */
-       if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
-               set_last_buddy(se);
-       if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
+       if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
                set_next_buddy(pse);
 
        /*
@@ -1667,36 +1735,44 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
                return;
 
        /* Idle tasks are by definition preempted by everybody. */
-       if (unlikely(curr->policy == SCHED_IDLE)) {
-               resched_task(curr);
-               return;
-       }
+       if (unlikely(curr->policy == SCHED_IDLE))
+               goto preempt;
 
-       if ((sched_feat(WAKEUP_SYNC) && sync) ||
-           (sched_feat(WAKEUP_OVERLAP) &&
-            (se->avg_overlap < sysctl_sched_migration_cost &&
-             pse->avg_overlap < sysctl_sched_migration_cost))) {
-               resched_task(curr);
-               return;
-       }
+       if (sched_feat(WAKEUP_SYNC) && sync)
+               goto preempt;
 
-       if (sched_feat(WAKEUP_RUNNING)) {
-               if (pse->avg_running < se->avg_running) {
-                       set_next_buddy(pse);
-                       resched_task(curr);
-                       return;
-               }
-       }
+       if (sched_feat(WAKEUP_OVERLAP) &&
+                       se->avg_overlap < sysctl_sched_migration_cost &&
+                       pse->avg_overlap < sysctl_sched_migration_cost)
+               goto preempt;
 
        if (!sched_feat(WAKEUP_PREEMPT))
                return;
 
+       update_curr(cfs_rq);
        find_matching_se(&se, &pse);
-
        BUG_ON(!pse);
-
        if (wakeup_preempt_entity(se, pse) == 1)
-               resched_task(curr);
+               goto preempt;
+
+       return;
+
+preempt:
+       resched_task(curr);
+       /*
+        * Only set the backward buddy when the current task is still
+        * on the rq. This can happen when a wakeup gets interleaved
+        * with schedule on the ->pre_schedule() or idle_balance()
+        * point, either of which can * drop the rq lock.
+        *
+        * Also, during early boot the idle thread is in the fair class,
+        * for obvious reasons its a bad idea to schedule back to it.
+        */
+       if (unlikely(!se->on_rq || curr == rq->idle))
+               return;
+
+       if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
+               set_last_buddy(se);
 }
 
 static struct task_struct *pick_next_task_fair(struct rq *rq)
@@ -1705,21 +1781,11 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
        struct cfs_rq *cfs_rq = &rq->cfs;
        struct sched_entity *se;
 
-       if (unlikely(!cfs_rq->nr_running))
+       if (!cfs_rq->nr_running)
                return NULL;
 
        do {
                se = pick_next_entity(cfs_rq);
-               /*
-                * If se was a buddy, clear it so that it will have to earn
-                * the favour again.
-                *
-                * If se was not a buddy, clear the buddies because neither
-                * was elegible to run, let them earn it again.
-                *
-                * IOW. unconditionally clear buddies.
-                */
-               __clear_buddies(cfs_rq, NULL);
                set_next_entity(cfs_rq, se);
                cfs_rq = group_cfs_rq(se);
        } while (cfs_rq);
@@ -1750,57 +1816,164 @@ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
  */
 
 /*
- * Load-balancing iterator. Note: while the runqueue stays locked
- * during the whole iteration, the current task might be
- * dequeued so the iterator has to be dequeue-safe. Here we
- * achieve that by always pre-iterating before returning
- * the current task:
+ * pull_task - move a task from a remote runqueue to the local runqueue.
+ * Both runqueues must be locked.
  */
-static struct task_struct *
-__load_balance_iterator(struct cfs_rq *cfs_rq, struct list_head *next)
+static void pull_task(struct rq *src_rq, struct task_struct *p,
+                     struct rq *this_rq, int this_cpu)
 {
-       struct task_struct *p = NULL;
-       struct sched_entity *se;
+       deactivate_task(src_rq, p, 0);
+       set_task_cpu(p, this_cpu);
+       activate_task(this_rq, p, 0);
+       check_preempt_curr(this_rq, p, 0);
+}
 
-       if (next == &cfs_rq->tasks)
-               return NULL;
+/*
+ * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
+ */
+static
+int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
+                    struct sched_domain *sd, enum cpu_idle_type idle,
+                    int *all_pinned)
+{
+       int tsk_cache_hot = 0;
+       /*
+        * We do not migrate tasks that are:
+        * 1) running (obviously), or
+        * 2) cannot be migrated to this CPU due to cpus_allowed, or
+        * 3) are cache-hot on their current CPU.
+        */
+       if (!cpumask_test_cpu(this_cpu, &p->cpus_allowed)) {
+               schedstat_inc(p, se.nr_failed_migrations_affine);
+               return 0;
+       }
+       *all_pinned = 0;
 
-       se = list_entry(next, struct sched_entity, group_node);
-       p = task_of(se);
-       cfs_rq->balance_iterator = next->next;
+       if (task_running(rq, p)) {
+               schedstat_inc(p, se.nr_failed_migrations_running);
+               return 0;
+       }
 
-       return p;
-}
+       /*
+        * Aggressive migration if:
+        * 1) task is cache cold, or
+        * 2) too many balance attempts have failed.
+        */
 
-static struct task_struct *load_balance_start_fair(void *arg)
-{
-       struct cfs_rq *cfs_rq = arg;
+       tsk_cache_hot = task_hot(p, rq->clock, sd);
+       if (!tsk_cache_hot ||
+               sd->nr_balance_failed > sd->cache_nice_tries) {
+#ifdef CONFIG_SCHEDSTATS
+               if (tsk_cache_hot) {
+                       schedstat_inc(sd, lb_hot_gained[idle]);
+                       schedstat_inc(p, se.nr_forced_migrations);
+               }
+#endif
+               return 1;
+       }
 
-       return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next);
+       if (tsk_cache_hot) {
+               schedstat_inc(p, se.nr_failed_migrations_hot);
+               return 0;
+       }
+       return 1;
 }
 
-static struct task_struct *load_balance_next_fair(void *arg)
+/*
+ * move_one_task tries to move exactly one task from busiest to this_rq, as
+ * part of active balancing operations within "domain".
+ * Returns 1 if successful and 0 otherwise.
+ *
+ * Called with both runqueues locked.
+ */
+static int
+move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest,
+             struct sched_domain *sd, enum cpu_idle_type idle)
 {
-       struct cfs_rq *cfs_rq = arg;
+       struct task_struct *p, *n;
+       struct cfs_rq *cfs_rq;
+       int pinned = 0;
 
-       return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator);
+       for_each_leaf_cfs_rq(busiest, cfs_rq) {
+               list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {
+
+                       if (!can_migrate_task(p, busiest, this_cpu,
+                                               sd, idle, &pinned))
+                               continue;
+
+                       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;
+               }
+       }
+
+       return 0;
 }
 
 static unsigned long
-__load_balance_fair(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 cfs_rq *cfs_rq)
+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 cfs_rq *busiest_cfs_rq)
 {
-       struct rq_iterator cfs_rq_iterator;
+       int loops = 0, pulled = 0, pinned = 0;
+       long rem_load_move = max_load_move;
+       struct task_struct *p, *n;
 
-       cfs_rq_iterator.start = load_balance_start_fair;
-       cfs_rq_iterator.next = load_balance_next_fair;
-       cfs_rq_iterator.arg = cfs_rq;
+       if (max_load_move == 0)
+               goto out;
 
-       return balance_tasks(this_rq, this_cpu, busiest,
-                       max_load_move, sd, idle, all_pinned,
-                       this_best_prio, &cfs_rq_iterator);
+       pinned = 1;
+
+       list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) {
+               if (loops++ > sysctl_sched_nr_migrate)
+                       break;
+
+               if ((p->se.load.weight >> 1) > rem_load_move ||
+                   !can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned))
+                       continue;
+
+               pull_task(busiest, p, this_rq, this_cpu);
+               pulled++;
+               rem_load_move -= p->se.load.weight;
+
+#ifdef CONFIG_PREEMPT
+               /*
+                * NEWIDLE balancing is a source of latency, so preemptible
+                * kernels will stop after the first task is pulled to minimize
+                * the critical section.
+                */
+               if (idle == CPU_NEWLY_IDLE)
+                       break;
+#endif
+
+               /*
+                * We only want to steal up to the prescribed amount of
+                * weighted load.
+                */
+               if (rem_load_move <= 0)
+                       break;
+
+               if (p->prio < *this_best_prio)
+                       *this_best_prio = p->prio;
+       }
+out:
+       /*
+        * 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().
+        */
+       schedstat_add(sd, lb_gained[idle], pulled);
+
+       if (all_pinned)
+               *all_pinned = pinned;
+
+       return max_load_move - rem_load_move;
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
@@ -1832,9 +2005,9 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
                rem_load = (u64)rem_load_move * busiest_weight;
                rem_load = div_u64(rem_load, busiest_h_load + 1);
 
-               moved_load = __load_balance_fair(this_rq, this_cpu, busiest,
+               moved_load = balance_tasks(this_rq, this_cpu, busiest,
                                rem_load, sd, idle, all_pinned, this_best_prio,
-                               tg->cfs_rq[busiest_cpu]);
+                               busiest_cfs_rq);
 
                if (!moved_load)
                        continue;
@@ -1857,35 +2030,1529 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  struct sched_domain *sd, enum cpu_idle_type idle,
                  int *all_pinned, int *this_best_prio)
 {
-       return __load_balance_fair(this_rq, this_cpu, busiest,
+       return balance_tasks(this_rq, this_cpu, busiest,
                        max_load_move, sd, idle, all_pinned,
                        this_best_prio, &busiest->cfs);
 }
 #endif
 
-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)
+/*
+ * move_tasks tries to move up to max_load_move weighted load from busiest to
+ * this_rq, as part of a balancing operation within domain "sd".
+ * Returns 1 if successful and 0 otherwise.
+ *
+ * Called with both runqueues locked.
+ */
+static int move_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)
 {
-       struct cfs_rq *busy_cfs_rq;
-       struct rq_iterator cfs_rq_iterator;
+       unsigned long total_load_moved = 0, load_moved;
+       int this_best_prio = this_rq->curr->prio;
 
-       cfs_rq_iterator.start = load_balance_start_fair;
-       cfs_rq_iterator.next = load_balance_next_fair;
+       do {
+               load_moved = load_balance_fair(this_rq, this_cpu, busiest,
+                               max_load_move - total_load_moved,
+                               sd, idle, all_pinned, &this_best_prio);
 
-       for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
+               total_load_moved += load_moved;
+
+#ifdef CONFIG_PREEMPT
                /*
-                * pass busy_cfs_rq argument into
-                * load_balance_[start|next]_fair iterators
+                * NEWIDLE balancing is a source of latency, so preemptible
+                * kernels will stop after the first task is pulled to minimize
+                * the critical section.
                 */
-               cfs_rq_iterator.arg = busy_cfs_rq;
-               if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
-                                      &cfs_rq_iterator))
-                   return 1;
+               if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
+                       break;
+
+               if (raw_spin_is_contended(&this_rq->lock) ||
+                               raw_spin_is_contended(&busiest->lock))
+                       break;
+#endif
+       } while (load_moved && max_load_move > total_load_moved);
+
+       return total_load_moved > 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;
+       unsigned long busiest_group_capacity;
+
+       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
+ */
+struct sg_lb_stats {
+       unsigned long avg_load; /*Avg load across the CPUs of the group */
+       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 group_capacity;
+       int group_imb; /* Is there an imbalance in the group ? */
+};
+
+/**
+ * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
+ * @group: The group whose first cpu is to be returned.
+ */
+static inline unsigned int group_first_cpu(struct sched_group *group)
+{
+       return cpumask_first(sched_group_cpus(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.
+ * @idle: The Idle status of the CPU for whose sd load_icx is obtained.
+ */
+static inline int get_sd_load_idx(struct sched_domain *sd,
+                                       enum cpu_idle_type idle)
+{
+       int load_idx;
+
+       switch (idle) {
+       case CPU_NOT_IDLE:
+               load_idx = sd->busy_idx;
+               break;
+
+       case CPU_NEWLY_IDLE:
+               load_idx = sd->newidle_idx;
+               break;
+       default:
+               load_idx = sd->idle_idx;
+               break;
        }
 
+       return load_idx;
+}
+
+
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+/**
+ * init_sd_power_savings_stats - Initialize power savings statistics for
+ * the given sched_domain, during load balancing.
+ *
+ * @sd: Sched domain whose power-savings statistics are to be initialized.
+ * @sds: Variable containing the statistics for sd.
+ * @idle: Idle status of the CPU at which we're performing load-balancing.
+ */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+       struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+       /*
+        * Busy processors will not participate in power savings
+        * balance.
+        */
+       if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
+               sds->power_savings_balance = 0;
+       else {
+               sds->power_savings_balance = 1;
+               sds->min_nr_running = ULONG_MAX;
+               sds->leader_nr_running = 0;
+       }
+}
+
+/**
+ * update_sd_power_savings_stats - Update the power saving stats for a
+ * sched_domain while performing load balancing.
+ *
+ * @group: sched_group belonging to the sched_domain under consideration.
+ * @sds: Variable containing the statistics of the sched_domain
+ * @local_group: Does group contain the CPU for which we're performing
+ *             load balancing ?
+ * @sgs: Variable containing the statistics of the group.
+ */
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+       struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+
+       if (!sds->power_savings_balance)
+               return;
+
+       /*
+        * If the local group is idle or completely loaded
+        * no need to do power savings balance at this domain
+        */
+       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 (!sds->power_savings_balance ||
+               sgs->sum_nr_running >= sgs->group_capacity ||
+               !sgs->sum_nr_running)
+               return;
+
+       /*
+        * Calculate the group which has the least non-idle load.
+        * This is the group from where we need to pick up the load
+        * for saving power
+        */
+       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;
+       }
+
+       /*
+        * Calculate the group which is almost near its
+        * capacity but still has some space to pick up some load
+        * from other group and save more power
+        */
+       if (sgs->sum_nr_running + 1 > sgs->group_capacity)
+               return;
+
+       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;
+       }
+}
+
+/**
+ * check_power_save_busiest_group - see if there is potential for some power-savings balance
+ * @sds: Variable containing the statistics of the sched_domain
+ *     under consideration.
+ * @this_cpu: Cpu at which we're currently performing load-balancing.
+ * @imbalance: Variable to store the imbalance.
+ *
+ * Description:
+ * Check if we have potential to perform some power-savings balance.
+ * If yes, set the busiest group to be the least loaded group in the
+ * sched_domain, so that it's CPUs can be put to idle.
+ *
+ * Returns 1 if there is potential to perform power-savings balance.
+ * Else returns 0.
+ */
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+                                       int this_cpu, unsigned long *imbalance)
+{
+       if (!sds->power_savings_balance)
+               return 0;
+
+       if (sds->this != sds->group_leader ||
+                       sds->group_leader == sds->group_min)
+               return 0;
+
+       *imbalance = sds->min_load_per_task;
+       sds->busiest = sds->group_min;
+
+       return 1;
+
+}
+#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+       struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+       return;
+}
+
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+       struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+       return;
+}
+
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+                                       int this_cpu, unsigned long *imbalance)
+{
        return 0;
 }
+#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
+
+
+unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu)
+{
+       return SCHED_LOAD_SCALE;
+}
+
+unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
+{
+       return default_scale_freq_power(sd, cpu);
+}
+
+unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+       unsigned long weight = cpumask_weight(sched_domain_span(sd));
+       unsigned long smt_gain = sd->smt_gain;
+
+       smt_gain /= weight;
+
+       return smt_gain;
+}
+
+unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu)
+{
+       return default_scale_smt_power(sd, cpu);
+}
+
+unsigned long scale_rt_power(int cpu)
+{
+       struct rq *rq = cpu_rq(cpu);
+       u64 total, available;
+
+       sched_avg_update(rq);
+
+       total = sched_avg_period() + (rq->clock - rq->age_stamp);
+       available = total - rq->rt_avg;
+
+       if (unlikely((s64)total < SCHED_LOAD_SCALE))
+               total = SCHED_LOAD_SCALE;
+
+       total >>= SCHED_LOAD_SHIFT;
+
+       return div_u64(available, total);
+}
+
+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;
+
+       if (sched_feat(ARCH_POWER))
+               power *= arch_scale_freq_power(sd, cpu);
+       else
+               power *= default_scale_freq_power(sd, cpu);
+
+       power >>= SCHED_LOAD_SHIFT;
+
+       if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) {
+               if (sched_feat(ARCH_POWER))
+                       power *= arch_scale_smt_power(sd, cpu);
+               else
+                       power *= default_scale_smt_power(sd, cpu);
+
+               power >>= SCHED_LOAD_SHIFT;
+       }
+
+       power *= scale_rt_power(cpu);
+       power >>= SCHED_LOAD_SHIFT;
+
+       if (!power)
+               power = 1;
+
+       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;
+
+       if (!child) {
+               update_cpu_power(sd, cpu);
+               return;
+       }
+
+       power = 0;
+
+       group = child->groups;
+       do {
+               power += group->cpu_power;
+               group = group->next;
+       } while (group != child->groups);
+
+       sdg->cpu_power = power;
+}
+
+/**
+ * update_sg_lb_stats - Update sched_group's statistics for load balancing.
+ * @sd: The sched_domain whose statistics are to be updated.
+ * @group: sched_group whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @load_idx: Load index of sched_domain of this_cpu for load calc.
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @local_group: Does group contain this_cpu.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sgs: variable to hold the statistics for this group.
+ */
+static inline void update_sg_lb_stats(struct sched_domain *sd,
+                       struct sched_group *group, int this_cpu,
+                       enum cpu_idle_type idle, int load_idx, int *sd_idle,
+                       int local_group, const struct cpumask *cpus,
+                       int *balance, struct sg_lb_stats *sgs)
+{
+       unsigned long load, max_cpu_load, min_cpu_load;
+       int i;
+       unsigned int balance_cpu = -1, first_idle_cpu = 0;
+       unsigned long avg_load_per_task = 0;
+
+       if (local_group)
+               balance_cpu = group_first_cpu(group);
+
+       /* Tally up the load of all CPUs in the group */
+       max_cpu_load = 0;
+       min_cpu_load = ~0UL;
+
+       for_each_cpu_and(i, sched_group_cpus(group), cpus) {
+               struct rq *rq = cpu_rq(i);
+
+               if (*sd_idle && rq->nr_running)
+                       *sd_idle = 0;
+
+               /* Bias balancing toward cpus of our domain */
+               if (local_group) {
+                       if (idle_cpu(i) && !first_idle_cpu) {
+                               first_idle_cpu = 1;
+                               balance_cpu = i;
+                       }
+
+                       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)
+                               min_cpu_load = load;
+               }
+
+               sgs->group_load += load;
+               sgs->sum_nr_running += rq->nr_running;
+               sgs->sum_weighted_load += weighted_cpuload(i);
+
+       }
+
+       /*
+        * First idle cpu or the first cpu(busiest) in this sched group
+        * is eligible for doing load balancing at this and above
+        * domains. In the newly idle case, we will allow all the cpu's
+        * to do the newly idle load balance.
+        */
+       if (idle != CPU_NEWLY_IDLE && local_group &&
+           balance_cpu != this_cpu) {
+               *balance = 0;
+               return;
+       }
+
+       update_group_power(sd, this_cpu);
+
+       /* Adjust by relative CPU power of the group */
+       sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power;
+
+       /*
+        * Consider the group unbalanced when the imbalance is larger
+        * than the average weight of two tasks.
+        *
+        * APZ: with cgroup the avg task weight can vary wildly and
+        *      might not be a suitable number - should we keep a
+        *      normalized nr_running number somewhere that negates
+        *      the hierarchy?
+        */
+       if (sgs->sum_nr_running)
+               avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
+
+       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);
+}
+
+/**
+ * update_sd_lb_stats - Update sched_group's statistics for load balancing.
+ * @sd: sched_domain whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sds: variable to hold the statistics for this sched_domain.
+ */
+static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
+                       enum cpu_idle_type idle, int *sd_idle,
+                       const struct cpumask *cpus, int *balance,
+                       struct sd_lb_stats *sds)
+{
+       struct sched_domain *child = sd->child;
+       struct sched_group *group = sd->groups;
+       struct sg_lb_stats sgs;
+       int load_idx, prefer_sibling = 0;
+
+       if (child && child->flags & SD_PREFER_SIBLING)
+               prefer_sibling = 1;
+
+       init_sd_power_savings_stats(sd, sds, idle);
+       load_idx = get_sd_load_idx(sd, idle);
+
+       do {
+               int local_group;
+
+               local_group = cpumask_test_cpu(this_cpu,
+                                              sched_group_cpus(group));
+               memset(&sgs, 0, sizeof(sgs));
+               update_sg_lb_stats(sd, group, this_cpu, idle, load_idx, sd_idle,
+                               local_group, cpus, balance, &sgs);
+
+               if (local_group && !(*balance))
+                       return;
+
+               sds->total_load += sgs.group_load;
+               sds->total_pwr += group->cpu_power;
+
+               /*
+                * In case the child domain prefers tasks go to siblings
+                * first, lower the group capacity to one so that we'll try
+                * and move all the excess tasks away.
+                */
+               if (prefer_sibling)
+                       sgs.group_capacity = min(sgs.group_capacity, 1UL);
+
+               if (local_group) {
+                       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)) {
+                       sds->max_load = sgs.avg_load;
+                       sds->busiest = group;
+                       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->group_imb = sgs.group_imb;
+               }
+
+               update_sd_power_savings_stats(group, sds, local_group, &sgs);
+               group = group->next;
+       } while (group != sd->groups);
+}
+
+/**
+ * fix_small_imbalance - Calculate the minor imbalance that exists
+ *                     amongst the groups of a sched_domain, during
+ *                     load balancing.
+ * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
+ * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
+ * @imbalance: Variable to store the imbalance.
+ */
+static inline void fix_small_imbalance(struct sd_lb_stats *sds,
+                               int this_cpu, unsigned long *imbalance)
+{
+       unsigned long tmp, pwr_now = 0, pwr_move = 0;
+       unsigned int imbn = 2;
+       unsigned long scaled_busy_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
+               sds->this_load_per_task =
+                       cpu_avg_load_per_task(this_cpu);
+
+       scaled_busy_load_per_task = sds->busiest_load_per_task
+                                                * SCHED_LOAD_SCALE;
+       scaled_busy_load_per_task /= sds->busiest->cpu_power;
+
+       if (sds->max_load - sds->this_load + scaled_busy_load_per_task >=
+                       (scaled_busy_load_per_task * imbn)) {
+               *imbalance = sds->busiest_load_per_task;
+               return;
+       }
+
+       /*
+        * OK, we don't have enough imbalance to justify moving tasks,
+        * however we may be able to increase total CPU power used by
+        * moving them.
+        */
+
+       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 = (sds->busiest_load_per_task * SCHED_LOAD_SCALE) /
+               sds->busiest->cpu_power;
+       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 (sds->max_load * sds->busiest->cpu_power <
+               sds->busiest_load_per_task * SCHED_LOAD_SCALE)
+               tmp = (sds->max_load * sds->busiest->cpu_power) /
+                       sds->this->cpu_power;
+       else
+               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;
+
+       /* Move if we gain throughput */
+       if (pwr_move > pwr_now)
+               *imbalance = sds->busiest_load_per_task;
+}
+
+/**
+ * calculate_imbalance - Calculate the amount of imbalance present within the
+ *                      groups of a given sched_domain during load balance.
+ * @sds: statistics of the sched_domain whose imbalance is to be calculated.
+ * @this_cpu: Cpu for which currently load balance is being performed.
+ * @imbalance: The variable to store the imbalance.
+ */
+static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
+               unsigned long *imbalance)
+{
+       unsigned long max_pull, load_above_capacity = ~0UL;
+
+       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);
+       }
+
+       /*
+        * In the presence of smp nice balancing, certain scenarios can have
+        * 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) {
+               *imbalance = 0;
+               return fix_small_imbalance(sds, this_cpu, imbalance);
+       }
+
+       if (!sds->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 *= (SCHED_LOAD_SCALE * SCHED_LOAD_SCALE);
+
+               load_above_capacity /= sds->busiest->cpu_power;
+       }
+
+       /*
+        * We're trying to get all the cpus to the average_load, so we don't
+        * want to push ourselves above the average load, nor do we wish to
+        * reduce the max loaded cpu below the average load. At the same time,
+        * we also don't want to reduce the group load below the group capacity
+        * (so that we can implement power-savings policies etc). Thus we look
+        * for the minimum possible imbalance.
+        * 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);
+
+       /* 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)
+                       / SCHED_LOAD_SCALE;
+
+       /*
+        * if *imbalance is less than the average load per runnable task
+        * there is no gaurantee that any tasks will be moved so we'll have
+        * a think about bumping its value to force at least one task to be
+        * moved
+        */
+       if (*imbalance < sds->busiest_load_per_task)
+               return fix_small_imbalance(sds, this_cpu, imbalance);
+
+}
+/******* find_busiest_group() helpers end here *********************/
+
+/**
+ * find_busiest_group - Returns the busiest group within the sched_domain
+ * if there is an imbalance. If there isn't an imbalance, and
+ * the user has opted for power-savings, it returns a group whose
+ * CPUs can be put to idle by rebalancing those tasks elsewhere, if
+ * such a group exists.
+ *
+ * Also calculates the amount of weighted load which should be moved
+ * to restore balance.
+ *
+ * @sd: The sched_domain whose busiest group is to be returned.
+ * @this_cpu: The cpu for which load balancing is currently being performed.
+ * @imbalance: Variable which stores amount of weighted load which should
+ *             be moved to restore balance/put a group to idle.
+ * @idle: The idle status of this_cpu.
+ * @sd_idle: The idleness of sd
+ * @cpus: The set of CPUs under consideration for load-balancing.
+ * @balance: Pointer to a variable indicating if this_cpu
+ *     is the appropriate cpu to perform load balancing at this_level.
+ *
+ * Returns:    - the busiest group if imbalance exists.
+ *             - If no imbalance and user has opted for power-savings balance,
+ *                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 sched_domain *sd, int this_cpu,
+                  unsigned long *imbalance, enum cpu_idle_type idle,
+                  int *sd_idle, const struct cpumask *cpus, int *balance)
+{
+       struct sd_lb_stats sds;
+
+       memset(&sds, 0, sizeof(sds));
+
+       /*
+        * Compute the various statistics relavent for load balancing at
+        * this level.
+        */
+       update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
+                                       balance, &sds);
+
+       /* Cases where imbalance does not exist from POV of this_cpu */
+       /* 1) this_cpu is not the appropriate cpu to perform load balancing
+        *    at this level.
+        * 2) There is no busy sibling group to pull from.
+        * 3) This group is the busiest group.
+        * 4) This group is more busy than the avg busieness at this
+        *    sched_domain.
+        * 5) The imbalance is within the specified limit.
+        */
+       if (!(*balance))
+               goto ret;
+
+       if (!sds.busiest || sds.busiest_nr_running == 0)
+               goto out_balanced;
+
+       if (sds.this_load >= sds.max_load)
+               goto out_balanced;
+
+       sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
+
+       if (sds.this_load >= sds.avg_load)
+               goto out_balanced;
+
+       if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
+               goto out_balanced;
+
+       /* Looks like there is an imbalance. Compute it */
+       calculate_imbalance(&sds, this_cpu, imbalance);
+       return sds.busiest;
+
+out_balanced:
+       /*
+        * There is no obvious imbalance. But check if we can do some balancing
+        * to save power.
+        */
+       if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
+               return sds.busiest;
+ret:
+       *imbalance = 0;
+       return NULL;
+}
+
+/*
+ * find_busiest_queue - find the busiest runqueue among the cpus in group.
+ */
+static struct rq *
+find_busiest_queue(struct sched_group *group, enum cpu_idle_type idle,
+                  unsigned long imbalance, const struct cpumask *cpus)
+{
+       struct rq *busiest = NULL, *rq;
+       unsigned long max_load = 0;
+       int i;
+
+       for_each_cpu(i, sched_group_cpus(group)) {
+               unsigned long power = power_of(i);
+               unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+               unsigned long wl;
+
+               if (!cpumask_test_cpu(i, cpus))
+                       continue;
+
+               rq = cpu_rq(i);
+               wl = weighted_cpuload(i);
+
+               /*
+                * When comparing with imbalance, use weighted_cpuload()
+                * which is not scaled with the cpu power.
+                */
+               if (capacity && rq->nr_running == 1 && wl > imbalance)
+                       continue;
+
+               /*
+                * For the load comparisons with the other cpu's, consider
+                * the weighted_cpuload() scaled with the cpu power, so that
+                * the load can be moved away from the cpu that is potentially
+                * running at a lower capacity.
+                */
+               wl = (wl * SCHED_LOAD_SCALE) / power;
+
+               if (wl > max_load) {
+                       max_load = wl;
+                       busiest = rq;
+               }
+       }
+
+       return busiest;
+}
+
+/*
+ * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
+ * so long as it is large enough.
+ */
+#define MAX_PINNED_INTERVAL    512
+
+/* Working cpumask for load_balance and load_balance_newidle. */
+static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
+
+static int need_active_balance(struct sched_domain *sd, int sd_idle, int idle)
+{
+       if (idle == CPU_NEWLY_IDLE) {
+               /*
+                * The only task running in a non-idle cpu can be moved to this
+                * cpu in an attempt to completely freeup the other CPU
+                * package.
+                *
+                * The package power saving logic comes from
+                * find_busiest_group(). If there are no imbalance, then
+                * f_b_g() will return NULL. However when sched_mc={1,2} then
+                * f_b_g() will select a group from which a running task may be
+                * pulled to this cpu in order to make the other package idle.
+                * If there is no opportunity to make a package idle and if
+                * there are no imbalance, then f_b_g() will return NULL and no
+                * action will be taken in load_balance_newidle().
+                *
+                * Under normal task pull operation due to imbalance, there
+                * will be more than one task in the source run queue and
+                * move_tasks() will succeed.  ld_moved will be true and this
+                * active balance code will not be triggered.
+                */
+               if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+                   !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+                       return 0;
+
+               if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP)
+                       return 0;
+       }
+
+       return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
+}
+
+/*
+ * Check this_cpu to ensure it is balanced within domain. Attempt to move
+ * tasks if there is an imbalance.
+ */
+static int load_balance(int this_cpu, struct rq *this_rq,
+                       struct sched_domain *sd, enum cpu_idle_type idle,
+                       int *balance)
+{
+       int ld_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
+       struct sched_group *group;
+       unsigned long imbalance;
+       struct rq *busiest;
+       unsigned long flags;
+       struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
+
+       cpumask_copy(cpus, cpu_active_mask);
+
+       /*
+        * When power savings policy is enabled for the parent domain, idle
+        * sibling can pick up load irrespective of busy siblings. In this case,
+        * let the state of idle sibling percolate up as CPU_IDLE, instead of
+        * portraying it as CPU_NOT_IDLE.
+        */
+       if (idle != CPU_NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
+           !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+               sd_idle = 1;
+
+       schedstat_inc(sd, lb_count[idle]);
+
+redo:
+       update_shares(sd);
+       group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
+                                  cpus, balance);
+
+       if (*balance == 0)
+               goto out_balanced;
+
+       if (!group) {
+               schedstat_inc(sd, lb_nobusyg[idle]);
+               goto out_balanced;
+       }
+
+       busiest = find_busiest_queue(group, idle, imbalance, cpus);
+       if (!busiest) {
+               schedstat_inc(sd, lb_nobusyq[idle]);
+               goto out_balanced;
+       }
+
+       BUG_ON(busiest == this_rq);
+
+       schedstat_add(sd, lb_imbalance[idle], imbalance);
+
+       ld_moved = 0;
+       if (busiest->nr_running > 1) {
+               /*
+                * Attempt to move tasks. If find_busiest_group has found
+                * an imbalance but busiest->nr_running <= 1, the group is
+                * still unbalanced. ld_moved simply stays zero, so it is
+                * correctly treated as an imbalance.
+                */
+               local_irq_save(flags);
+               double_rq_lock(this_rq, busiest);
+               ld_moved = move_tasks(this_rq, this_cpu, busiest,
+                                     imbalance, sd, idle, &all_pinned);
+               double_rq_unlock(this_rq, busiest);
+               local_irq_restore(flags);
+
+               /*
+                * some other cpu did the load balance for us.
+                */
+               if (ld_moved && this_cpu != smp_processor_id())
+                       resched_cpu(this_cpu);
+
+               /* All tasks on this runqueue were pinned by CPU affinity */
+               if (unlikely(all_pinned)) {
+                       cpumask_clear_cpu(cpu_of(busiest), cpus);
+                       if (!cpumask_empty(cpus))
+                               goto redo;
+                       goto out_balanced;
+               }
+       }
+
+       if (!ld_moved) {
+               schedstat_inc(sd, lb_failed[idle]);
+               sd->nr_balance_failed++;
+
+               if (need_active_balance(sd, sd_idle, idle)) {
+                       raw_spin_lock_irqsave(&busiest->lock, flags);
+
+                       /* don't kick the migration_thread, if the curr
+                        * task on busiest cpu can't be moved to this_cpu
+                        */
+                       if (!cpumask_test_cpu(this_cpu,
+                                             &busiest->curr->cpus_allowed)) {
+                               raw_spin_unlock_irqrestore(&busiest->lock,
+                                                           flags);
+                               all_pinned = 1;
+                               goto out_one_pinned;
+                       }
+
+                       if (!busiest->active_balance) {
+                               busiest->active_balance = 1;
+                               busiest->push_cpu = this_cpu;
+                               active_balance = 1;
+                       }
+                       raw_spin_unlock_irqrestore(&busiest->lock, flags);
+                       if (active_balance)
+                               wake_up_process(busiest->migration_thread);
+
+                       /*
+                        * We've kicked active balancing, reset the failure
+                        * counter.
+                        */
+                       sd->nr_balance_failed = sd->cache_nice_tries+1;
+               }
+       } else
+               sd->nr_balance_failed = 0;
+
+       if (likely(!active_balance)) {
+               /* We were unbalanced, so reset the balancing interval */
+               sd->balance_interval = sd->min_interval;
+       } else {
+               /*
+                * If we've begun active balancing, start to back off. This
+                * case may not be covered by the all_pinned logic if there
+                * is only 1 task on the busy runqueue (because we don't call
+                * move_tasks).
+                */
+               if (sd->balance_interval < sd->max_interval)
+                       sd->balance_interval *= 2;
+       }
+
+       if (!ld_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+           !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+               ld_moved = -1;
+
+       goto out;
+
+out_balanced:
+       schedstat_inc(sd, lb_balanced[idle]);
+
+       sd->nr_balance_failed = 0;
+
+out_one_pinned:
+       /* tune up the balancing interval */
+       if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
+                       (sd->balance_interval < sd->max_interval))
+               sd->balance_interval *= 2;
+
+       if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
+           !test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
+               ld_moved = -1;
+       else
+               ld_moved = 0;
+out:
+       if (ld_moved)
+               update_shares(sd);
+       return ld_moved;
+}
+
+/*
+ * idle_balance is called by schedule() if this_cpu is about to become
+ * idle. Attempts to pull tasks from other CPUs.
+ */
+static void idle_balance(int this_cpu, struct rq *this_rq)
+{
+       struct sched_domain *sd;
+       int pulled_task = 0;
+       unsigned long next_balance = jiffies + HZ;
+
+       this_rq->idle_stamp = this_rq->clock;
+
+       if (this_rq->avg_idle < sysctl_sched_migration_cost)
+               return;
+
+       /*
+        * Drop the rq->lock, but keep IRQ/preempt disabled.
+        */
+       raw_spin_unlock(&this_rq->lock);
+
+       for_each_domain(this_cpu, sd) {
+               unsigned long interval;
+               int balance = 1;
+
+               if (!(sd->flags & SD_LOAD_BALANCE))
+                       continue;
+
+               if (sd->flags & SD_BALANCE_NEWIDLE) {
+                       /* If we've pulled tasks over stop searching: */
+                       pulled_task = load_balance(this_cpu, this_rq,
+                                                  sd, CPU_NEWLY_IDLE, &balance);
+               }
+
+               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;
+                       break;
+               }
+       }
+
+       raw_spin_lock(&this_rq->lock);
+
+       if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
+               /*
+                * We are going idle. next_balance may be set based on
+                * a busy processor. So reset next_balance.
+                */
+               this_rq->next_balance = next_balance;
+       }
+}
+
+/*
+ * active_load_balance is run by migration threads. It pushes running tasks
+ * off the busiest CPU onto idle CPUs. It requires at least 1 task to be
+ * running on each physical CPU where possible, and avoids physical /
+ * logical imbalances.
+ *
+ * Called with busiest_rq locked.
+ */
+static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
+{
+       int target_cpu = busiest_rq->push_cpu;
+       struct sched_domain *sd;
+       struct rq *target_rq;
+
+       /* Is there any task to move? */
+       if (busiest_rq->nr_running <= 1)
+               return;
+
+       target_rq = cpu_rq(target_cpu);
+
+       /*
+        * This condition is "impossible", if it occurs
+        * we need to fix it. Originally reported by
+        * Bjorn Helgaas on a 128-cpu setup.
+        */
+       BUG_ON(busiest_rq == target_rq);
+
+       /* move a task from busiest_rq to target_rq */
+       double_lock_balance(busiest_rq, target_rq);
+       update_rq_clock(busiest_rq);
+       update_rq_clock(target_rq);
+
+       /* Search for an sd spanning us and the target CPU. */
+       for_each_domain(target_cpu, sd) {
+               if ((sd->flags & SD_LOAD_BALANCE) &&
+                   cpumask_test_cpu(busiest_cpu, sched_domain_span(sd)))
+                               break;
+       }
+
+       if (likely(sd)) {
+               schedstat_inc(sd, alb_count);
+
+               if (move_one_task(target_rq, target_cpu, busiest_rq,
+                                 sd, CPU_IDLE))
+                       schedstat_inc(sd, alb_pushed);
+               else
+                       schedstat_inc(sd, alb_failed);
+       }
+       double_unlock_balance(busiest_rq, target_rq);
+}
+
+#ifdef CONFIG_NO_HZ
+static struct {
+       atomic_t load_balancer;
+       cpumask_var_t cpu_mask;
+       cpumask_var_t ilb_grp_nohz_mask;
+} nohz ____cacheline_aligned = {
+       .load_balancer = ATOMIC_INIT(-1),
+};
+
+int get_nohz_load_balancer(void)
+{
+       return atomic_read(&nohz.load_balancer);
+}
+
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+/**
+ * lowest_flag_domain - Return lowest sched_domain containing flag.
+ * @cpu:       The cpu whose lowest level of sched domain is to
+ *             be returned.
+ * @flag:      The flag to check for the lowest sched_domain
+ *             for the given cpu.
+ *
+ * Returns the lowest sched_domain of a cpu which contains the given flag.
+ */
+static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
+{
+       struct sched_domain *sd;
+
+       for_each_domain(cpu, sd)
+               if (sd && (sd->flags & flag))
+                       break;
+
+       return sd;
+}
+
+/**
+ * for_each_flag_domain - Iterates over sched_domains containing the flag.
+ * @cpu:       The cpu whose domains we're iterating over.
+ * @sd:                variable holding the value of the power_savings_sd
+ *             for cpu.
+ * @flag:      The flag to filter the sched_domains to be iterated.
+ *
+ * Iterates over all the scheduler domains for a given cpu that has the 'flag'
+ * set, starting from the lowest sched_domain to the highest.
+ */
+#define for_each_flag_domain(cpu, sd, flag) \
+       for (sd = lowest_flag_domain(cpu, flag); \
+               (sd && (sd->flags & flag)); sd = sd->parent)
+
+/**
+ * is_semi_idle_group - Checks if the given sched_group is semi-idle.
+ * @ilb_group: group to be checked for semi-idleness
+ *
+ * Returns:    1 if the group is semi-idle. 0 otherwise.
+ *
+ * We define a sched_group to be semi idle if it has atleast one idle-CPU
+ * and atleast one non-idle CPU. This helper function checks if the given
+ * sched_group is semi-idle or not.
+ */
+static inline int is_semi_idle_group(struct sched_group *ilb_group)
+{
+       cpumask_and(nohz.ilb_grp_nohz_mask, nohz.cpu_mask,
+                                       sched_group_cpus(ilb_group));
+
+       /*
+        * A sched_group is semi-idle when it has atleast one busy cpu
+        * and atleast one idle cpu.
+        */
+       if (cpumask_empty(nohz.ilb_grp_nohz_mask))
+               return 0;
+
+       if (cpumask_equal(nohz.ilb_grp_nohz_mask, sched_group_cpus(ilb_group)))
+               return 0;
+
+       return 1;
+}
+/**
+ * find_new_ilb - Finds the optimum idle load balancer for nomination.
+ * @cpu:       The cpu which is nominating a new idle_load_balancer.
+ *
+ * Returns:    Returns the id of the idle load balancer if it exists,
+ *             Else, returns >= nr_cpu_ids.
+ *
+ * This algorithm picks the idle load balancer such that it belongs to a
+ * semi-idle powersavings sched_domain. The idea is to try and avoid
+ * completely idle packages/cores just for the purpose of idle load balancing
+ * when there are other idle cpu's which are better suited for that job.
+ */
+static int find_new_ilb(int cpu)
+{
+       struct sched_domain *sd;
+       struct sched_group *ilb_group;
+
+       /*
+        * Have idle load balancer selection from semi-idle packages only
+        * when power-aware load balancing is enabled
+        */
+       if (!(sched_smt_power_savings || sched_mc_power_savings))
+               goto out_done;
+
+       /*
+        * Optimize for the case when we have no idle CPUs or only one
+        * idle CPU. Don't walk the sched_domain hierarchy in such cases
+        */
+       if (cpumask_weight(nohz.cpu_mask) < 2)
+               goto out_done;
+
+       for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
+               ilb_group = sd->groups;
+
+               do {
+                       if (is_semi_idle_group(ilb_group))
+                               return cpumask_first(nohz.ilb_grp_nohz_mask);
+
+                       ilb_group = ilb_group->next;
+
+               } while (ilb_group != sd->groups);
+       }
+
+out_done:
+       return cpumask_first(nohz.cpu_mask);
+}
+#else /*  (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
+static inline int find_new_ilb(int call_cpu)
+{
+       return cpumask_first(nohz.cpu_mask);
+}
+#endif
+
+/*
+ * This routine will try to nominate the ilb (idle load balancing)
+ * owner among the cpus whose ticks are stopped. ilb owner will do the idle
+ * load balancing on behalf of all those cpus. If all the cpus in the system
+ * go into this tickless mode, then there will be no ilb owner (as there is
+ * no need for one) and all the cpus will sleep till the next wakeup event
+ * arrives...
+ *
+ * For the ilb owner, tick is not stopped. And this tick will be used
+ * for idle load balancing. ilb owner will still be part of
+ * nohz.cpu_mask..
+ *
+ * While stopping the tick, this cpu will become the ilb owner if there
+ * is no other owner. And will be the owner till that cpu becomes busy
+ * or if all cpus in the system stop their ticks at which point
+ * there is no need for ilb owner.
+ *
+ * When the ilb owner becomes busy, it nominates another owner, during the
+ * next busy scheduler_tick()
+ */
+int select_nohz_load_balancer(int stop_tick)
+{
+       int cpu = smp_processor_id();
+
+       if (stop_tick) {
+               cpu_rq(cpu)->in_nohz_recently = 1;
+
+               if (!cpu_active(cpu)) {
+                       if (atomic_read(&nohz.load_balancer) != cpu)
+                               return 0;
+
+                       /*
+                        * If we are going offline and still the leader,
+                        * give up!
+                        */
+                       if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
+                               BUG();
+
+                       return 0;
+               }
+
+               cpumask_set_cpu(cpu, nohz.cpu_mask);
+
+               /* time for ilb owner also to sleep */
+               if (cpumask_weight(nohz.cpu_mask) == num_active_cpus()) {
+                       if (atomic_read(&nohz.load_balancer) == cpu)
+                               atomic_set(&nohz.load_balancer, -1);
+                       return 0;
+               }
+
+               if (atomic_read(&nohz.load_balancer) == -1) {
+                       /* make me the ilb owner */
+                       if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
+                               return 1;
+               } else if (atomic_read(&nohz.load_balancer) == cpu) {
+                       int new_ilb;
+
+                       if (!(sched_smt_power_savings ||
+                                               sched_mc_power_savings))
+                               return 1;
+                       /*
+                        * Check to see if there is a more power-efficient
+                        * ilb.
+                        */
+                       new_ilb = find_new_ilb(cpu);
+                       if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
+                               atomic_set(&nohz.load_balancer, -1);
+                               resched_cpu(new_ilb);
+                               return 0;
+                       }
+                       return 1;
+               }
+       } else {
+               if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
+                       return 0;
+
+               cpumask_clear_cpu(cpu, nohz.cpu_mask);
+
+               if (atomic_read(&nohz.load_balancer) == cpu)
+                       if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
+                               BUG();
+       }
+       return 0;
+}
+#endif
+
+static DEFINE_SPINLOCK(balancing);
+
+/*
+ * It checks each scheduling domain to see if it is due to be balanced,
+ * and initiates a balancing operation if so.
+ *
+ * Balancing parameters are set up in arch_init_sched_domains.
+ */
+static void rebalance_domains(int cpu, enum cpu_idle_type idle)
+{
+       int balance = 1;
+       struct rq *rq = cpu_rq(cpu);
+       unsigned long interval;
+       struct sched_domain *sd;
+       /* Earliest time when we have to do rebalance again */
+       unsigned long next_balance = jiffies + 60*HZ;
+       int update_next_balance = 0;
+       int need_serialize;
+
+       for_each_domain(cpu, sd) {
+               if (!(sd->flags & SD_LOAD_BALANCE))
+                       continue;
+
+               interval = sd->balance_interval;
+               if (idle != CPU_IDLE)
+                       interval *= sd->busy_factor;
+
+               /* scale ms to jiffies */
+               interval = msecs_to_jiffies(interval);
+               if (unlikely(!interval))
+                       interval = 1;
+               if (interval > HZ*NR_CPUS/10)
+                       interval = HZ*NR_CPUS/10;
+
+               need_serialize = sd->flags & SD_SERIALIZE;
+
+               if (need_serialize) {
+                       if (!spin_trylock(&balancing))
+                               goto out;
+               }
+
+               if (time_after_eq(jiffies, sd->last_balance + interval)) {
+                       if (load_balance(cpu, rq, sd, idle, &balance)) {
+                               /*
+                                * We've pulled tasks over so either we're no
+                                * longer idle, or one of our SMT siblings is
+                                * not idle.
+                                */
+                               idle = CPU_NOT_IDLE;
+                       }
+                       sd->last_balance = jiffies;
+               }
+               if (need_serialize)
+                       spin_unlock(&balancing);
+out:
+               if (time_after(next_balance, sd->last_balance + interval)) {
+                       next_balance = sd->last_balance + interval;
+                       update_next_balance = 1;
+               }
+
+               /*
+                * Stop the load balance at this level. There is another
+                * CPU in our sched group which is doing load balancing more
+                * actively.
+                */
+               if (!balance)
+                       break;
+       }
+
+       /*
+        * next_balance will be updated only when there is a need.
+        * When the cpu is attached to null domain for ex, it will not be
+        * updated.
+        */
+       if (likely(update_next_balance))
+               rq->next_balance = next_balance;
+}
+
+/*
+ * run_rebalance_domains is triggered when needed from the scheduler tick.
+ * In CONFIG_NO_HZ case, the idle load balance owner will do the
+ * rebalancing for all the cpus for whom scheduler ticks are stopped.
+ */
+static void run_rebalance_domains(struct softirq_action *h)
+{
+       int this_cpu = smp_processor_id();
+       struct rq *this_rq = cpu_rq(this_cpu);
+       enum cpu_idle_type idle = this_rq->idle_at_tick ?
+                                               CPU_IDLE : CPU_NOT_IDLE;
+
+       rebalance_domains(this_cpu, idle);
+
+#ifdef CONFIG_NO_HZ
+       /*
+        * If this cpu is the owner for idle load balancing, then do the
+        * balancing on behalf of the other idle cpus whose ticks are
+        * stopped.
+        */
+       if (this_rq->idle_at_tick &&
+           atomic_read(&nohz.load_balancer) == this_cpu) {
+               struct rq *rq;
+               int balance_cpu;
+
+               for_each_cpu(balance_cpu, nohz.cpu_mask) {
+                       if (balance_cpu == this_cpu)
+                               continue;
+
+                       /*
+                        * If this cpu gets work to do, stop the load balancing
+                        * work being done for other cpus. Next load
+                        * balancing owner will pick it up.
+                        */
+                       if (need_resched())
+                               break;
+
+                       rebalance_domains(balance_cpu, CPU_IDLE);
+
+                       rq = cpu_rq(balance_cpu);
+                       if (time_after(this_rq->next_balance, rq->next_balance))
+                               this_rq->next_balance = rq->next_balance;
+               }
+       }
+#endif
+}
+
+static inline int on_null_domain(int cpu)
+{
+       return !rcu_dereference_sched(cpu_rq(cpu)->sd);
+}
+
+/*
+ * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
+ *
+ * In case of CONFIG_NO_HZ, this is the place where we nominate a new
+ * idle load balancing owner or decide to stop the periodic load balancing,
+ * if the whole system is idle.
+ */
+static inline void trigger_load_balance(struct rq *rq, int cpu)
+{
+#ifdef CONFIG_NO_HZ
+       /*
+        * If we were in the nohz mode recently and busy at the current
+        * scheduler tick, then check if we need to nominate new idle
+        * load balancer.
+        */
+       if (rq->in_nohz_recently && !rq->idle_at_tick) {
+               rq->in_nohz_recently = 0;
+
+               if (atomic_read(&nohz.load_balancer) == cpu) {
+                       cpumask_clear_cpu(cpu, nohz.cpu_mask);
+                       atomic_set(&nohz.load_balancer, -1);
+               }
+
+               if (atomic_read(&nohz.load_balancer) == -1) {
+                       int ilb = find_new_ilb(cpu);
+
+                       if (ilb < nr_cpu_ids)
+                               resched_cpu(ilb);
+               }
+       }
+
+       /*
+        * If this cpu is idle and doing idle load balancing for all the
+        * cpus with ticks stopped, is it time for that to stop?
+        */
+       if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
+           cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
+               resched_cpu(cpu);
+               return;
+       }
+
+       /*
+        * If this cpu is idle and the idle load balancing is done by
+        * someone else, then no need raise the SCHED_SOFTIRQ
+        */
+       if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
+           cpumask_test_cpu(cpu, nohz.cpu_mask))
+               return;
+#endif
+       /* Don't need to rebalance while attached to NULL domain */
+       if (time_after_eq(jiffies, rq->next_balance) &&
+           likely(!on_null_domain(cpu)))
+               raise_softirq(SCHED_SOFTIRQ);
+}
+
+static void rq_online_fair(struct rq *rq)
+{
+       update_sysctl();
+}
+
+static void rq_offline_fair(struct rq *rq)
+{
+       update_sysctl();
+}
+
+#else  /* CONFIG_SMP */
+
+/*
+ * on UP we do not need to balance between CPUs:
+ */
+static inline void idle_balance(int cpu, struct rq *rq)
+{
+}
+
 #endif /* CONFIG_SMP */
 
 /*
@@ -1903,28 +3570,30 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
 }
 
 /*
- * Share the fairness runtime between parent and child, thus the
- * total amount of pressure for CPU stays equal - new tasks
- * get a chance to run but frequent forkers are not allowed to
- * monopolize the CPU. Note: the parent runqueue is locked,
- * the child is not running yet.
+ * called on fork with the child task as argument from the parent's context
+ *  - child not yet on the tasklist
+ *  - preemption disabled
  */
-static void task_new_fair(struct rq *rq, struct task_struct *p)
+static void task_fork_fair(struct task_struct *p)
 {
-       struct cfs_rq *cfs_rq = task_cfs_rq(p);
+       struct cfs_rq *cfs_rq = task_cfs_rq(current);
        struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
        int this_cpu = smp_processor_id();
+       struct rq *rq = this_rq();
+       unsigned long flags;
 
-       sched_info_queued(p);
+       raw_spin_lock_irqsave(&rq->lock, flags);
+
+       if (unlikely(task_cpu(p) != this_cpu))
+               __set_task_cpu(p, this_cpu);
 
        update_curr(cfs_rq);
+
        if (curr)
                se->vruntime = curr->vruntime;
        place_entity(cfs_rq, se, 1);
 
-       /* 'curr' will be NULL if the child belongs to a different group */
-       if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
-                       curr && entity_before(curr, se)) {
+       if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) {
                /*
                 * Upon rescheduling, sched_class::put_prev_task() will place
                 * 'current' within the tree based on its new key value.
@@ -1933,7 +3602,9 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
                resched_task(rq->curr);
        }
 
-       enqueue_task_fair(rq, p, 0);
+       se->vruntime -= cfs_rq->min_vruntime;
+
+       raw_spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 /*
@@ -1986,30 +3657,27 @@ static void set_curr_task_fair(struct rq *rq)
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-static void moved_group_fair(struct task_struct *p)
+static void moved_group_fair(struct task_struct *p, int on_rq)
 {
        struct cfs_rq *cfs_rq = task_cfs_rq(p);
 
        update_curr(cfs_rq);
-       place_entity(cfs_rq, &p->se, 1);
+       if (!on_rq)
+               place_entity(cfs_rq, &p->se, 1);
 }
 #endif
 
-unsigned int get_rr_interval_fair(struct task_struct *task)
+static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task)
 {
        struct sched_entity *se = &task->se;
-       unsigned long flags;
-       struct rq *rq;
        unsigned int rr_interval = 0;
 
        /*
         * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise
         * idle runqueue:
         */
-       rq = task_rq_lock(task, &flags);
        if (rq->cfs.load.weight)
                rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se));
-       task_rq_unlock(rq, &flags);
 
        return rr_interval;
 }
@@ -2031,13 +3699,15 @@ static const struct sched_class fair_sched_class = {
 #ifdef CONFIG_SMP
        .select_task_rq         = select_task_rq_fair,
 
-       .load_balance           = load_balance_fair,
-       .move_one_task          = move_one_task_fair,
+       .rq_online              = rq_online_fair,
+       .rq_offline             = rq_offline_fair,
+
+       .task_waking            = task_waking_fair,
 #endif
 
        .set_curr_task          = set_curr_task_fair,
        .task_tick              = task_tick_fair,
-       .task_new               = task_new_fair,
+       .task_fork              = task_fork_fair,
 
        .prio_changed           = prio_changed_fair,
        .switched_to            = switched_to_fair,