1 files changed, 173 insertions, 68 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 9573c33688b8..51aa3e102acb 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -143,6 +143,49 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
         return se->parent;
 }
 
+/* return depth at which a sched entity is present in the hierarchy */
+static inline int depth_se(struct sched_entity *se)
+{
+        int depth = 0;
+
+        for_each_sched_entity(se)
+                depth++;
+
+        return depth;
+}
+
+static void
+find_matching_se(struct sched_entity **se, struct sched_entity **pse)
+{
+        int se_depth, pse_depth;
+
+        /*
+         * preemption test can be made between sibling entities who are in the
+         * same cfs_rq i.e who have a common parent. Walk up the hierarchy of
+         * both tasks until we find their ancestors who are siblings of common
+         * parent.
+         */
+
+        /* First walk up until both entities are at same depth */
+        se_depth = depth_se(*se);
+        pse_depth = depth_se(*pse);
+
+        while (se_depth > pse_depth) {
+                se_depth--;
+                *se = parent_entity(*se);
+        }
+
+        while (pse_depth > se_depth) {
+                pse_depth--;
+                *pse = parent_entity(*pse);
+        }
+
+        while (!is_same_group(*se, *pse)) {
+                *se = parent_entity(*se);
+                *pse = parent_entity(*pse);
+        }
+}
+
 #else   /* CONFIG_FAIR_GROUP_SCHED */
 
 static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
@@ -193,6 +236,11 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
         return NULL;
 }
 
+static inline void
+find_matching_se(struct sched_entity **se, struct sched_entity **pse)
+{
+}
+
 #endif  /* CONFIG_FAIR_GROUP_SCHED */
 
 
@@ -223,6 +271,27 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
         return se->vruntime - cfs_rq->min_vruntime;
 }
 
+static void update_min_vruntime(struct cfs_rq *cfs_rq)
+{
+        u64 vruntime = cfs_rq->min_vruntime;
+
+        if (cfs_rq->curr)
+                vruntime = cfs_rq->curr->vruntime;
+
+        if (cfs_rq->rb_leftmost) {
+                struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost,
+                                                   struct sched_entity,
+                                                   run_node);
+
+                if (vruntime == cfs_rq->min_vruntime)
+                        vruntime = se->vruntime;
+                else
+                        vruntime = min_vruntime(vruntime, se->vruntime);
+        }
+
+        cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime);
+}
+
 /*
  * Enqueue an entity into the rb-tree:
  */
@@ -256,15 +325,8 @@ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
          * Maintain a cache of leftmost tree entries (it is frequently
          * used):
          */
-        if (leftmost) {
+        if (leftmost)
                 cfs_rq->rb_leftmost = &se->run_node;
-                /*
-                 * maintain cfs_rq->min_vruntime to be a monotonic increasing
-                 * value tracking the leftmost vruntime in the tree.
-                 */
-                cfs_rq->min_vruntime =
-                        max_vruntime(cfs_rq->min_vruntime, se->vruntime);
-        }
 
         rb_link_node(&se->run_node, parent, link);
         rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
@@ -274,37 +336,25 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         if (cfs_rq->rb_leftmost == &se->run_node) {
                 struct rb_node *next_node;
-                struct sched_entity *next;
 
                 next_node = rb_next(&se->run_node);
                 cfs_rq->rb_leftmost = next_node;
-
-                if (next_node) {
-                        next = rb_entry(next_node,
-                                        struct sched_entity, run_node);
-                        cfs_rq->min_vruntime =
-                                max_vruntime(cfs_rq->min_vruntime,
-                                             next->vruntime);
-                }
         }
 
-        if (cfs_rq->next == se)
-                cfs_rq->next = NULL;
-
         rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
 }
 
-static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
-{
-        return cfs_rq->rb_leftmost;
-}
-
 static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
 {
-        return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
+        struct rb_node *left = cfs_rq->rb_leftmost;
+
+        if (!left)
+                return NULL;
+
+        return rb_entry(left, struct sched_entity, run_node);
 }
 
-static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
+static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
 {
         struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
 
@@ -424,6 +474,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
         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);
 }
 
 static void update_curr(struct cfs_rq *cfs_rq)
@@ -613,13 +664,7 @@ static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
-        u64 vruntime;
-
-        if (first_fair(cfs_rq)) {
-                vruntime = min_vruntime(cfs_rq->min_vruntime,
-                                __pick_next_entity(cfs_rq)->vruntime);
-        } else
-                vruntime = cfs_rq->min_vruntime;
+        u64 vruntime = cfs_rq->min_vruntime;
 
         /*
          * The 'current' period is already promised to the current tasks,
@@ -693,9 +738,16 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 #endif
         }
 
+        if (cfs_rq->last == se)
+                cfs_rq->last = NULL;
+
+        if (cfs_rq->next == se)
+                cfs_rq->next = NULL;
+
         if (se != cfs_rq->curr)
                 __dequeue_entity(cfs_rq, se);
         account_entity_dequeue(cfs_rq, se);
+        update_min_vruntime(cfs_rq);
 }
 
 /*
@@ -742,29 +794,18 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
         se->prev_sum_exec_runtime = se->sum_exec_runtime;
 }
 
-static struct sched_entity *
-pick_next(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
-        struct rq *rq = rq_of(cfs_rq);
-        u64 pair_slice = rq->clock - cfs_rq->pair_start;
-
-        if (!cfs_rq->next || pair_slice > sysctl_sched_min_granularity) {
-                cfs_rq->pair_start = rq->clock;
-                return se;
-        }
-
-        return cfs_rq->next;
-}
+static int
+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 = NULL;
+        struct sched_entity *se = __pick_next_entity(cfs_rq);
 
-        if (first_fair(cfs_rq)) {
-                se = __pick_next_entity(cfs_rq);
-                se = pick_next(cfs_rq, se);
-                set_next_entity(cfs_rq, se);
-        }
+        if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1)
+                return cfs_rq->next;
+
+        if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1)
+                return cfs_rq->last;
 
         return se;
 }
@@ -1122,10 +1163,9 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
         if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
                 return 0;
 
-        if (!sync && sched_feat(SYNC_WAKEUPS) &&
-            curr->se.avg_overlap < sysctl_sched_migration_cost &&
-            p->se.avg_overlap < sysctl_sched_migration_cost)
-                sync = 1;
+        if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||
+                        p->se.avg_overlap > sysctl_sched_migration_cost))
+                sync = 0;
 
         /*
          * If sync wakeup then subtract the (maximum possible)
@@ -1244,33 +1284,88 @@ static unsigned long wakeup_gran(struct sched_entity *se)
          * More easily preempt - nice tasks, while not making it harder for
          * + nice tasks.
          */
-        if (sched_feat(ASYM_GRAN))
-                gran = calc_delta_mine(gran, NICE_0_LOAD, &se->load);
+        if (!sched_feat(ASYM_GRAN) || se->load.weight > NICE_0_LOAD)
+                gran = calc_delta_fair(sysctl_sched_wakeup_granularity, se);
 
         return gran;
 }
 
 /*
+ * Should 'se' preempt 'curr'.
+ *
+ *             |s1
+ *        |s2
+ *   |s3
+ *         g
+ *      |<--->|c
+ *
+ *  w(c, s1) = -1
+ *  w(c, s2) =  0
+ *  w(c, s3) =  1
+ *
+ */
+static int
+wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
+{
+        s64 gran, vdiff = curr->vruntime - se->vruntime;
+
+        if (vdiff <= 0)
+                return -1;
+
+        gran = wakeup_gran(curr);
+        if (vdiff > gran)
+                return 1;
+
+        return 0;
+}
+
+static void set_last_buddy(struct sched_entity *se)
+{
+        for_each_sched_entity(se)
+                cfs_rq_of(se)->last = se;
+}
+
+static void set_next_buddy(struct sched_entity *se)
+{
+        for_each_sched_entity(se)
+                cfs_rq_of(se)->next = se;
+}
+
+/*
  * Preempt the current task with a newly woken task if needed:
  */
 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
 {
         struct task_struct *curr = rq->curr;
-        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
         struct sched_entity *se = &curr->se, *pse = &p->se;
-        s64 delta_exec;
 
         if (unlikely(rt_prio(p->prio))) {
+                struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+
                 update_rq_clock(rq);
                 update_curr(cfs_rq);
                 resched_task(curr);
                 return;
         }
 
+        if (unlikely(p->sched_class != &fair_sched_class))
+                return;
+
         if (unlikely(se == pse))
                 return;
 
-        cfs_rq_of(pse)->next = pse;
+        /*
+         * 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);
+        set_next_buddy(pse);
 
         /*
          * We can come here with TIF_NEED_RESCHED already set from new task
@@ -1296,9 +1391,19 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
                 return;
         }
 
-        delta_exec = se->sum_exec_runtime - se->prev_sum_exec_runtime;
-        if (delta_exec > wakeup_gran(pse))
-                resched_task(curr);
+        find_matching_se(&se, &pse);
+
+        while (se) {
+                BUG_ON(!pse);
+
+                if (wakeup_preempt_entity(se, pse) == 1) {
+                        resched_task(curr);
+                        break;
+                }
+
+                se = parent_entity(se);
+                pse = parent_entity(pse);
+        }
 }
 
 static struct task_struct *pick_next_task_fair(struct rq *rq)
@@ -1312,6 +1417,7 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
 
         do {
                 se = pick_next_entity(cfs_rq);
+                set_next_entity(cfs_rq, se);
                 cfs_rq = group_cfs_rq(se);
         } while (cfs_rq);
 
@@ -1594,9 +1700,6 @@ static const struct sched_class fair_sched_class = {
         .enqueue_task           = enqueue_task_fair,
         .dequeue_task           = dequeue_task_fair,
         .yield_task             = yield_task_fair,
-#ifdef CONFIG_SMP
-        .select_task_rq         = select_task_rq_fair,
-#endif /* CONFIG_SMP */
 
         .check_preempt_curr     = check_preempt_wakeup,
 
@@ -1604,6 +1707,8 @@ static const struct sched_class fair_sched_class = {
         .put_prev_task          = put_prev_task_fair,
 
 #ifdef CONFIG_SMP
+        .select_task_rq         = select_task_rq_fair,
+
         .load_balance           = load_balance_fair,
         .move_one_task          = move_one_task_fair,
 #endif