sched: better min_vruntime tracking

Better min_vruntime tracking: update it every time 'curr' is
updated - not just when a task is enqueued into the tree.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 33 insertions, 7 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index e3081fb65d63..ec445cadbb01 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -116,22 +116,28 @@ static inline struct task_struct *task_of(struct sched_entity *se)
  * Scheduling class tree data structure manipulation methods:
  */
 
+static inline u64
+max_vruntime(u64 min_vruntime, u64 vruntime)
+{
+        if ((vruntime > min_vruntime) ||
+            (min_vruntime > (1ULL << 61) && vruntime < (1ULL << 50)))
+                min_vruntime = vruntime;
+
+        return min_vruntime;
+}
+
 static inline void
 set_leftmost(struct cfs_rq *cfs_rq, struct rb_node *leftmost)
 {
         struct sched_entity *se;
 
         cfs_rq->rb_leftmost = leftmost;
-        if (leftmost) {
+        if (leftmost)
                 se = rb_entry(leftmost, struct sched_entity, run_node);
-                if ((se->vruntime > cfs_rq->min_vruntime) ||
-                    (cfs_rq->min_vruntime > (1ULL << 61) &&
-                     se->vruntime < (1ULL << 50)))
-                        cfs_rq->min_vruntime = se->vruntime;
-        }
 }
 
-s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
+static inline s64
+entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         return se->fair_key - cfs_rq->min_vruntime;
 }
@@ -254,6 +260,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
               unsigned long delta_exec)
 {
         unsigned long delta_exec_weighted;
+        u64 next_vruntime, min_vruntime;
 
         schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
 
@@ -265,6 +272,25 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
                                                         &curr->load);
         }
         curr->vruntime += delta_exec_weighted;
+
+        /*
+         * maintain cfs_rq->min_vruntime to be a monotonic increasing
+         * value tracking the leftmost vruntime in the tree.
+         */
+        if (first_fair(cfs_rq)) {
+                next_vruntime = __pick_next_entity(cfs_rq)->vruntime;
+
+                /* min_vruntime() := !max_vruntime() */
+                min_vruntime = max_vruntime(curr->vruntime, next_vruntime);
+                if (min_vruntime == next_vruntime)
+                        min_vruntime = curr->vruntime;
+                else
+                        min_vruntime = next_vruntime;
+        } else
+                min_vruntime = curr->vruntime;
+
+        cfs_rq->min_vruntime =
+                max_vruntime(cfs_rq->min_vruntime, min_vruntime);
 }
 
 static void update_curr(struct cfs_rq *cfs_rq)