sched: Replace use of entity_key()

"entity_key()" is only used in "__enqueue_entity()" and
its only function is to subtract a tasks vruntime by
its groups minvruntime.
Before this patch a rbtree enqueue-decision is done by
comparing two tasks in the style:

	"if (entity_key(cfs_rq, se) < entity_key(cfs_rq, entry))"

which would be

	"if (se->vruntime-cfs_rq->min_vruntime < entry->vruntime-cfs_rq->min_vruntime)"

or (if reducing cfs_rq->min_vruntime out)

	"if (se->vruntime < entry->vruntime)"

which is

	"if (entity_before(se, entry))"

So we do not need "entity_key()".
If "entity_before()" is inline we will also save one subtraction (only one,
because "entity_key(cfs_rq, se)"  was cached in "key")

Signed-off-by: Stephan Baerwolf <stephan.baerwolf@tu-ilmenau.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-ns12mnd2h5w8rb9agd8hnsfk@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 0588c0b..a2ecbaa 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -321,11 +321,6 @@ static inline int entity_before(struct sched_entity *a,
        return (s64)(a->vruntime - b->vruntime) < 0;
 }
 
-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;
@@ -359,7 +354,6 @@ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
        struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
        struct rb_node *parent = NULL;
        struct sched_entity *entry;
-       s64 key = entity_key(cfs_rq, se);
        int leftmost = 1;
 
        /*
@@ -372,7 +366,7 @@ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
                 * We dont care about collisions. Nodes with
                 * the same key stay together.
                 */
-               if (key < entity_key(cfs_rq, entry)) {
+               if (entity_before(se, entry)) {
                        link = &parent->rb_left;
                } else {
                        link = &parent->rb_right;