sched: Kill WAKEUP_PREEMPT

Remove the WAKEUP_PREEMPT feature, disabling it doesn't make any sense
and its outlived its use by a long long while.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Acked-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110729082033.GB12106@zhy
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched_fair.c

@@ -1095,9 +1095,6 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 	 * 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;
 
@@ -1233,7 +1230,7 @@ entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
 		return;
 #endif
 
-	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
+	if (cfs_rq->nr_running > 1)
 		check_preempt_tick(cfs_rq, curr);
 }
 
@@ -1899,10 +1896,6 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 	if (unlikely(p->policy != SCHED_NORMAL))
 		return;
 
-
-	if (!sched_feat(WAKEUP_PREEMPT))
-		return;
-
 	find_matching_se(&se, &pse);
 	update_curr(cfs_rq_of(se));
 	BUG_ON(!pse);

kernel/sched_features.h

@@ -11,11 +11,6 @@ SCHED_FEAT(GENTLE_FAIR_SLEEPERS, 1)
  */
 SCHED_FEAT(START_DEBIT, 1)
 
-/*
- * Should wakeups try to preempt running tasks.
- */
-SCHED_FEAT(WAKEUP_PREEMPT, 1)
-
 /*
  * Based on load and program behaviour, see if it makes sense to place
  * a newly woken task on the same cpu as the task that woke it --