sched: remove PREEMPT_RESTRICT

remove PREEMPT_RESTRICT. (this is a separate commit so that any
regression related to the removal itself is bisectable)
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -863,7 +863,6 @@ struct sched_entity {
 	struct load_weight	load;		/* for load-balancing */
 	struct rb_node		run_node;
 	unsigned int		on_rq;
-	int			peer_preempt;
 
 	u64			exec_start;
 	u64			sum_exec_runtime;

kernel/sched.c

@@ -460,7 +460,6 @@ enum {
 	SCHED_FEAT_TREE_AVG             = 4,
 	SCHED_FEAT_APPROX_AVG           = 8,
 	SCHED_FEAT_WAKEUP_PREEMPT	= 16,
-	SCHED_FEAT_PREEMPT_RESTRICT	= 32,
 };
 
 const_debug unsigned int sysctl_sched_features =
@@ -468,8 +467,7 @@ const_debug unsigned int sysctl_sched_features =
 		SCHED_FEAT_START_DEBIT		* 1 |
 		SCHED_FEAT_TREE_AVG		* 0 |
 		SCHED_FEAT_APPROX_AVG		* 0 |
-		SCHED_FEAT_WAKEUP_PREEMPT	* 1 |
-		SCHED_FEAT_PREEMPT_RESTRICT	* 0;
+		SCHED_FEAT_WAKEUP_PREEMPT	* 1;
 
 #define sched_feat(x) (sysctl_sched_features & SCHED_FEAT_##x)
 

kernel/sched_fair.c

@@ -546,7 +546,6 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 
 	update_stats_dequeue(cfs_rq, se);
 	if (sleep) {
-		se->peer_preempt = 0;
 #ifdef CONFIG_SCHEDSTATS
 		if (entity_is_task(se)) {
 			struct task_struct *tsk = task_of(se);
@@ -574,10 +573,8 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 
 	ideal_runtime = sched_slice(cfs_rq, curr);
 	delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
-	if (delta_exec > ideal_runtime ||
-			(sched_feat(PREEMPT_RESTRICT) && curr->peer_preempt))
+	if (delta_exec > ideal_runtime)
 		resched_task(rq_of(cfs_rq)->curr);
-	curr->peer_preempt = 0;
 }
 
 static void
@@ -867,9 +864,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
 			gran = calc_delta_fair(gran, &se->load);
 
 		if (delta > gran) {
-			int now = !sched_feat(PREEMPT_RESTRICT);
-
-			if (now || p->prio < curr->prio || !se->peer_preempt++)
+			if (p->prio < curr->prio)
 				resched_task(curr);
 		}
 	}
@@ -1083,7 +1078,6 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
 		swap(curr->vruntime, se->vruntime);
 	}
 
-	se->peer_preempt = 0;
 	enqueue_task_fair(rq, p, 0);
 	resched_task(rq->curr);
 }