[PATCH] [RSDL 5/6] sched: implement rsdl cpu scheduler

[Con Kolivas]

Implement the "Rotating Staircase DeadLine" RSDL cpu scheduler policy.

Signed-off-by: Con Kolivas <kernel@xxxxxxxxxxx>

---
 include/linux/init_task.h |    2 
 include/linux/sched.h     |   25 
 kernel/sched.c            | 1199 ++++++++++++++++++++++------------------------
 3 files changed, 597 insertions(+), 629 deletions(-)

Index: linux-2.6.20-rsdl/kernel/sched.c
===================================================================
--- linux-2.6.20-rsdl.orig/kernel/sched.c	2007-03-04 17:30:25.000000000 +1100
+++ linux-2.6.20-rsdl/kernel/sched.c	2007-03-04 17:30:31.000000000 +1100
@@ -16,6 +16,8 @@
  *		by Davide Libenzi, preemptible kernel bits by Robert Love.
  *  2003-09-03	Interactivity tuning by Con Kolivas.
  *  2004-04-02	Scheduler domains code by Nick Piggin
+ *  2007-03-02	Rotating Staircase deadline scheduling policy by Con Kolivas
+ *		RSDL v0.26
  */
 
 #include <linux/mm.h>
@@ -73,126 +75,29 @@
 #define USER_PRIO(p)		((p)-MAX_RT_PRIO)
 #define TASK_USER_PRIO(p)	USER_PRIO((p)->static_prio)
 #define MAX_USER_PRIO		(USER_PRIO(MAX_PRIO))
+#define SCHED_PRIO(p)		((p)+MAX_RT_PRIO)
+#define MAX_DYN_PRIO		(MAX_PRIO + PRIO_RANGE)
 
 /*
- * Some helpers for converting nanosecond timing to jiffy resolution
+ * Preemption needs to take into account that a low priority task can be
+ * at a higher prio due to list merging. Its priority is artificially
+ * elevated and it should be preempted if anything higher priority wakes up.
  */
-#define NS_TO_JIFFIES(TIME)	((TIME) / (1000000000 / HZ))
-#define JIFFIES_TO_NS(TIME)	((TIME) * (1000000000 / HZ))
+#define TASK_PREEMPTS_CURR(p, curr) \
+	(((p)->prio < (curr)->prio) || (((p)->prio == (curr)->prio) && \
+		((p)->static_prio < (curr)->static_prio && \
+			((curr)->static_prio > (curr)->prio))))
 
 /*
- * These are the 'tuning knobs' of the scheduler:
- *
- * Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
- * default timeslice is 100 msecs, maximum timeslice is 800 msecs.
- * Timeslices get refilled after they expire.
- */
-#define MIN_TIMESLICE		max(5 * HZ / 1000, 1)
-#define DEF_TIMESLICE		(100 * HZ / 1000)
-#define ON_RUNQUEUE_WEIGHT	 30
-#define CHILD_PENALTY		 95
-#define PARENT_PENALTY		100
-#define EXIT_WEIGHT		  3
-#define PRIO_BONUS_RATIO	 25
-#define MAX_BONUS		(MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
-#define INTERACTIVE_DELTA	  2
-#define MAX_SLEEP_AVG		(DEF_TIMESLICE * MAX_BONUS)
-#define STARVATION_LIMIT	(MAX_SLEEP_AVG)
-#define NS_MAX_SLEEP_AVG	(JIFFIES_TO_NS(MAX_SLEEP_AVG))
-
-/*
- * If a task is 'interactive' then we reinsert it in the active
- * array after it has expired its current timeslice. (it will not
- * continue to run immediately, it will still roundrobin with
- * other interactive tasks.)
- *
- * This part scales the interactivity limit depending on niceness.
- *
- * We scale it linearly, offset by the INTERACTIVE_DELTA delta.
- * Here are a few examples of different nice levels:
- *
- *  TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
- *  TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
- *  TASK_INTERACTIVE(  0): [1,1,1,1,0,0,0,0,0,0,0]
- *  TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
- *  TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
- *
- * (the X axis represents the possible -5 ... 0 ... +5 dynamic
- *  priority range a task can explore, a value of '1' means the
- *  task is rated interactive.)
- *
- * Ie. nice +19 tasks can never get 'interactive' enough to be
- * reinserted into the active array. And only heavily CPU-hog nice -20
- * tasks will be expired. Default nice 0 tasks are somewhere between,
- * it takes some effort for them to get interactive, but it's not
- * too hard.
- */
-
-#define CURRENT_BONUS(p) \
-	(NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
-		MAX_SLEEP_AVG)
-
-#define GRANULARITY	(10 * HZ / 1000 ? : 1)
-
-#ifdef CONFIG_SMP
-#define TIMESLICE_GRANULARITY(p)	(GRANULARITY * \
-		(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
-			num_online_cpus())
-#else
-#define TIMESLICE_GRANULARITY(p)	(GRANULARITY * \
-		(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
-#endif
-
-#define SCALE(v1,v1_max,v2_max) \
-	(v1) * (v2_max) / (v1_max)
-
-#define DELTA(p) \
-	(SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
-		INTERACTIVE_DELTA)
-
-#define TASK_INTERACTIVE(p) \
-	((p)->prio <= (p)->static_prio - DELTA(p))
-
-#define INTERACTIVE_SLEEP(p) \
-	(JIFFIES_TO_NS(MAX_SLEEP_AVG * \
-		(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
-
-#define TASK_PREEMPTS_CURR(p, rq) \
-	((p)->prio < (rq)->curr->prio)
-
-#define SCALE_PRIO(x, prio) \
-	max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
-
-static unsigned int static_prio_timeslice(int static_prio)
-{
-	if (static_prio < NICE_TO_PRIO(0))
-		return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio);
-	else
-		return SCALE_PRIO(DEF_TIMESLICE, static_prio);
-}
-
-/*
- * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
- * to time slice values: [800ms ... 100ms ... 5ms]
- *
- * The higher a thread's priority, the bigger timeslices
- * it gets during one round of execution. But even the lowest
- * priority thread gets MIN_TIMESLICE worth of execution time.
- */
-
-static inline unsigned int task_timeslice(struct task_struct *p)
-{
-	return static_prio_timeslice(p->static_prio);
-}
-
-/*
- * These are the runqueue data structures:
+ * This is the time all tasks within the same priority round robin.
+ * Set to a minimum of 6ms.
  */
+#define RR_INTERVAL		((6 * HZ / 1001) + 1)
+#define DEF_TIMESLICE		(RR_INTERVAL * 19)
 
 struct prio_array {
-	unsigned int nr_active;
-	DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */
 	struct list_head queue[MAX_PRIO];
+	/* Tasks queued at each priority */
 };
 
 /*
@@ -224,14 +129,40 @@ struct rq {
 	 */
 	unsigned long nr_uninterruptible;
 
-	unsigned long expired_timestamp;
 	/* Cached timestamp set by update_cpu_clock() */
 	unsigned long long most_recent_timestamp;
 	struct task_struct *curr, *idle;
 	unsigned long next_balance;
 	struct mm_struct *prev_mm;
+
+	DECLARE_BITMAP(dyn_bitmap, MAX_DYN_PRIO + 1);
+	/*
+	 * The bitmap of priorities queued; The extra PRIO_RANGE at the end
+	 * is for a bitmap of expired tasks queued. This minimises the number
+	 * of bit lookups over prio_array swaps. The dynamic bits can have
+	 * false positives. Include 1 bit for delimiter.
+	 */
+
+	DECLARE_BITMAP(static_bitmap, MAX_PRIO);
+	/* The bitmap of all static priorities queued */
+
+	unsigned long prio_queued[MAX_PRIO];
+	/* The number of tasks at each static priority */
+
+	long prio_quota[PRIO_RANGE];
+	/*
+	 * The quota of ticks the runqueue runs at each dynamic priority
+	 * before cycling to the next priority.
+	 */
+
 	struct prio_array *active, *expired, arrays[2];
-	int best_expired_prio;
+
+	int prio_level;
+	/* The current dynamic priority level this runqueue is at */
+
+	unsigned long prio_rotation;
+	/* How many times we have rotated the priority queue */
+
 	atomic_t nr_iowait;
 
 #ifdef CONFIG_SMP
@@ -569,12 +500,9 @@ static inline struct rq *this_rq_lock(vo
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
 /*
  * Called when a process is dequeued from the active array and given
- * the cpu.  We should note that with the exception of interactive
- * tasks, the expired queue will become the active queue after the active
- * queue is empty, without explicitly dequeuing and requeuing tasks in the
- * expired queue.  (Interactive tasks may be requeued directly to the
- * active queue, thus delaying tasks in the expired queue from running;
- * see scheduler_tick()).
+ * the cpu.  We should note that the expired queue will become the active
+ * queue after the active queue is empty, without explicitly dequeuing and
+ * requeuing tasks in the expired queue.
  *
  * This function is only called from sched_info_arrive(), rather than
  * dequeue_task(). Even though a task may be queued and dequeued multiple
@@ -672,71 +600,167 @@ sched_info_switch(struct task_struct *pr
 #define sched_info_switch(t, next)	do { } while (0)
 #endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */
 
+static inline int task_queued(struct task_struct *task)
+{
+	return !list_empty(&task->run_list);
+}
+
+static inline void set_task_entitlement(struct task_struct *p)
+{
+	__set_bit(USER_PRIO(p->prio), p->bitmap);
+
+	/*
+	 * In the case this task has been part of a merged list that has
+	 * made it to higher priority than it should be, we remove the
+	 * quota from its own priority since it will get a quota at this
+	 * priority.
+	 */
+	if (p->normal_prio < p->static_prio)
+		__set_bit(USER_PRIO(p->static_prio), p->bitmap);
+	p->time_slice = p->quota;
+}
+
 /*
- * Adding/removing a task to/from a priority array:
+ * Only the static_bitmap has hard accounting. The dynamic bits can have
+ * false positives. rt_tasks can only be on the active queue.
  */
-static void dequeue_task(struct task_struct *p, struct prio_array *array)
+static inline void set_dynamic_bit(struct task_struct *p, struct rq *rq)
 {
-	array->nr_active--;
-	list_del(&p->run_list);
-	if (list_empty(array->queue + p->prio))
-		__clear_bit(p->prio, array->bitmap);
+	if (p->array == rq->active)
+		__set_bit(p->prio, rq->dyn_bitmap);
+	else
+		__set_bit(p->prio + PRIO_RANGE, rq->dyn_bitmap);
 }
 
-static void enqueue_task(struct task_struct *p, struct prio_array *array)
+static inline void set_queue_bits(struct rq *rq, struct task_struct *p)
 {
-	sched_info_queued(p);
-	list_add_tail(&p->run_list, array->queue + p->prio);
-	__set_bit(p->prio, array->bitmap);
-	array->nr_active++;
-	p->array = array;
+	__set_bit(p->static_prio, rq->static_bitmap);
+	set_dynamic_bit(p, rq);
 }
 
 /*
- * Put task to the end of the run list without the overhead of dequeue
- * followed by enqueue.
+ * Removing from a runqueue. While we don't know with absolute certainty
+ * where this task really is, the p->array and p->prio are very likely
+ * so we check that queue to see if we can clear that bit to take some
+ * load off finding false positives in next_dynamic_task().
  */
-static void requeue_task(struct task_struct *p, struct prio_array *array)
+static void dequeue_task(struct task_struct *p, struct rq *rq)
 {
-	list_move_tail(&p->run_list, array->queue + p->prio);
+	list_del_init(&p->run_list);
+	if (!--rq->prio_queued[p->static_prio])
+		__clear_bit(p->static_prio, rq->static_bitmap);
+	if (list_empty(p->array->queue + p->prio)) {
+		int bitmap_prio = p->prio;
+
+		if (p->array == rq->expired)
+			bitmap_prio += PRIO_RANGE;
+		__clear_bit(bitmap_prio, rq->dyn_bitmap);
+	}
 }
 
-static inline void
-enqueue_task_head(struct task_struct *p, struct prio_array *array)
+/*
+ * The task is being queued on a fresh array so it has its entitlement
+ * bitmap cleared.
+ */
+static inline void task_new_array(struct task_struct *p, struct rq *rq)
+{
+	bitmap_zero(p->bitmap, PRIO_RANGE);
+	p->rotation = rq->prio_rotation;
+}
+
+#define rq_quota(rq, prio)	((rq)->prio_quota[USER_PRIO(prio)])
+/*
+ * recalc_task_prio determines what prio a non rt_task will be
+ * queued at. If the task has already been running during this runqueue's
+ * major rotation (rq->prio_rotation) then it continues at the same
+ * priority if it has tick entitlement left. If it does not have entitlement
+ * left, it finds the next priority slot according to its nice value that it
+ * has not extracted quota from. If it has not run during this major
+ * rotation, it starts at its static priority and has its bitmap quota
+ * cleared. If it does not have any slots left it has all its slots reset and
+ * is queued on the expired at its static priority.
+ */
+static void recalc_task_prio(struct task_struct *p, struct rq *rq)
 {
-	list_add(&p->run_list, array->queue + p->prio);
-	__set_bit(p->prio, array->bitmap);
-	array->nr_active++;
+	struct prio_array *array = rq->active;
+	int queue_prio, search_prio;
+
+	if (p->rotation == rq->prio_rotation && p->array == array) {
+		if (p->time_slice && rq_quota(rq, p->prio))
+			return;
+	} else
+		task_new_array(p, rq);
+	search_prio = p->static_prio;
+
+	/*
+	 * SCHED_BATCH tasks never start at better priority than any other
+	 * task that is already running since they are flagged as latency
+	 * insensitive. This means they never cause greater latencies in other
+	 * non SCHED_BATCH tasks of the same nice level.
+	 */
+	if (unlikely(p->policy == SCHED_BATCH))
+		search_prio = max(p->static_prio, rq->prio_level);
+	queue_prio = SCHED_PRIO(find_next_zero_bit(p->bitmap, PRIO_RANGE,
+		     USER_PRIO(search_prio)));
+	if (queue_prio == MAX_PRIO) {
+		queue_prio = p->static_prio;
+		array = rq->expired;
+		bitmap_zero(p->bitmap, PRIO_RANGE);
+	} else
+		rq_quota(rq, queue_prio) += p->quota;
+	p->prio = p->normal_prio = queue_prio;
 	p->array = array;
+	set_task_entitlement(p);
 }
 
 /*
- * __normal_prio - return the priority that is based on the static
- * priority but is modified by bonuses/penalties.
- *
- * We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
- * into the -5 ... 0 ... +5 bonus/penalty range.
- *
- * We use 25% of the full 0...39 priority range so that:
- *
- * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
- * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
- *
- * Both properties are important to certain workloads.
+ * Adding to a runqueue. The dynamic priority queue that it is added to is
+ * determined by the priority rotation of the runqueue it is being added to
+ * and the quota still available in the task in p->bitmap and p->time_slice
+ * (see recalc_task_prio above). The rq static_bitmap stores a list of
+ * the static priorities, and prio_queued the number of tasks stored at each
+ * p->static_prio level.
  */
+static inline void __enqueue_task(struct task_struct *p, struct rq *rq)
+{
+	if (rt_task(p))
+		p->array = rq->active;
+	else
+		recalc_task_prio(p, rq);
+	rq->prio_queued[p->static_prio]++;
 
-static inline int __normal_prio(struct task_struct *p)
+	sched_info_queued(p);
+	set_queue_bits(rq, p);
+}
+
+static void enqueue_task(struct task_struct *p, struct rq *rq)
 {
-	int bonus, prio;
+	__enqueue_task(p, rq);
+	list_add_tail(&p->run_list, p->array->queue + p->prio);
+}
 
-	bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
+static inline void enqueue_task_head(struct task_struct *p, struct rq *rq)
+{
+	__enqueue_task(p, rq);
+	list_add(&p->run_list, p->array->queue + p->prio);
+}
 
-	prio = p->static_prio - bonus;
-	if (prio < MAX_RT_PRIO)
-		prio = MAX_RT_PRIO;
-	if (prio > MAX_PRIO-1)
-		prio = MAX_PRIO-1;
-	return prio;
+/*
+ * requeue_task is only called when p->static_prio does not change. p->prio
+ * can change with dynamic tasks.
+ */
+static void requeue_task(struct task_struct *p, struct rq *rq,
+			 struct prio_array *old_array, int old_prio)
+{
+	list_move_tail(&p->run_list, p->array->queue + p->prio);
+	if (!rt_task(p)) {
+		if (list_empty(old_array->queue + old_prio)) {
+			if (old_array == rq->expired)
+				old_prio += PRIO_RANGE;
+			__clear_bit(old_prio, rq->dyn_bitmap);
+		}
+		set_dynamic_bit(p, rq);
+	}
 }
 
 /*
@@ -749,6 +773,20 @@ static inline int __normal_prio(struct t
  */
 
 /*
+ * task_timeslice - the total duration a task can run during one major
+ * rotation.
+ */
+static inline unsigned int task_timeslice(struct task_struct *p)
+{
+	unsigned int slice, rr;
+
+	slice = rr = p->quota;
+	if (likely(!rt_task(p)))
+		slice += (PRIO_RANGE - 1 - TASK_USER_PRIO(p)) * rr;
+	return slice;
+}
+
+/*
  * Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
  * If static_prio_timeslice() is ever changed to break this assumption then
  * this code will need modification
@@ -756,10 +794,9 @@ static inline int __normal_prio(struct t
 #define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
 #define LOAD_WEIGHT(lp) \
 	(((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
-#define PRIO_TO_LOAD_WEIGHT(prio) \
-	LOAD_WEIGHT(static_prio_timeslice(prio))
-#define RTPRIO_TO_LOAD_WEIGHT(rp) \
-	(PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))
+#define TASK_LOAD_WEIGHT(p)	LOAD_WEIGHT(task_timeslice(p))
+#define RTPRIO_TO_LOAD_WEIGHT(rp)	\
+	(LOAD_WEIGHT((RR_INTERVAL + 20 + (rp))))
 
 static void set_load_weight(struct task_struct *p)
 {
@@ -776,7 +813,7 @@ static void set_load_weight(struct task_
 #endif
 			p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority);
 	} else
-		p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio);
+		p->load_weight = TASK_LOAD_WEIGHT(p);
 }
 
 static inline void
@@ -804,28 +841,35 @@ static inline void dec_nr_running(struct
 }
 
 /*
- * Calculate the expected normal priority: i.e. priority
- * without taking RT-inheritance into account. Might be
- * boosted by interactivity modifiers. Changes upon fork,
- * setprio syscalls, and whenever the interactivity
- * estimator recalculates.
+ * __activate_task - move a task to the runqueue.
  */
-static inline int normal_prio(struct task_struct *p)
+static inline void __activate_task(struct task_struct *p, struct rq *rq)
+{
+	enqueue_task(p, rq);
+	inc_nr_running(p, rq);
+}
+
+/*
+ * __activate_idle_task - move idle task to the _front_ of runqueue.
+ */
+static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
 {
-	int prio;
+	enqueue_task_head(p, rq);
+	inc_nr_running(p, rq);
+}
 
+static inline int normal_prio(struct task_struct *p)
+{
 	if (has_rt_policy(p))
-		prio = MAX_RT_PRIO-1 - p->rt_priority;
-	else
-		prio = __normal_prio(p);
-	return prio;
+		return MAX_RT_PRIO-1 - p->rt_priority;
+	/* Other tasks all have normal_prio set in recalc_task_prio */
+	return p->static_prio;
 }
 
 /*
  * Calculate the current priority, i.e. the priority
  * taken into account by the scheduler. This value might
- * be boosted by RT tasks, or might be boosted by
- * interactivity modifiers. Will be RT if the task got
+ * be boosted by RT tasks as it will be RT if the task got
  * RT-boosted. If not then it returns p->normal_prio.
  */
 static int effective_prio(struct task_struct *p)
@@ -842,111 +886,26 @@ static int effective_prio(struct task_st
 }
 
 /*
- * __activate_task - move a task to the runqueue.
- */
-static void __activate_task(struct task_struct *p, struct rq *rq)
-{
-	struct prio_array *target = rq->active;
-
-	if (batch_task(p))
-		target = rq->expired;
-	enqueue_task(p, target);
-	inc_nr_running(p, rq);
-}
-
-/*
- * __activate_idle_task - move idle task to the _front_ of runqueue.
- */
-static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
-{
-	enqueue_task_head(p, rq->active);
-	inc_nr_running(p, rq);
-}
-
-/*
- * Recalculate p->normal_prio and p->prio after having slept,
- * updating the sleep-average too:
+ * All tasks have quotas based on RR_INTERVAL. From nice 0 to 19 they are
+ * all equal to it and below zero they get progressively larger making their
+ * effective quota significantly larger. rt tasks all get RR_INTERVAL.
  */
-static int recalc_task_prio(struct task_struct *p, unsigned long long now)
+static unsigned int rr_interval(struct task_struct *p)
 {
-	/* Caller must always ensure 'now >= p->timestamp' */
-	unsigned long sleep_time = now - p->timestamp;
+	int nice = TASK_NICE(p);
 
-	if (batch_task(p))
-		sleep_time = 0;
-
-	if (likely(sleep_time > 0)) {
-		/*
-		 * This ceiling is set to the lowest priority that would allow
-		 * a task to be reinserted into the active array on timeslice
-		 * completion.
-		 */
-		unsigned long ceiling = INTERACTIVE_SLEEP(p);
-
-		if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
-			/*
-			 * Prevents user tasks from achieving best priority
-			 * with one single large enough sleep.
-			 */
-			p->sleep_avg = ceiling;
-			/*
-			 * Using INTERACTIVE_SLEEP() as a ceiling places a
-			 * nice(0) task 1ms sleep away from promotion, and
-			 * gives it 700ms to round-robin with no chance of
-			 * being demoted.  This is more than generous, so
-			 * mark this sleep as non-interactive to prevent the
-			 * on-runqueue bonus logic from intervening should
-			 * this task not receive cpu immediately.
-			 */
-			p->sleep_type = SLEEP_NONINTERACTIVE;
-		} else {
-			/*
-			 * Tasks waking from uninterruptible sleep are
-			 * limited in their sleep_avg rise as they
-			 * are likely to be waiting on I/O
-			 */
-			if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
-				if (p->sleep_avg >= ceiling)
-					sleep_time = 0;
-				else if (p->sleep_avg + sleep_time >=
-					 ceiling) {
-						p->sleep_avg = ceiling;
-						sleep_time = 0;
-				}
-			}
-
-			/*
-			 * This code gives a bonus to interactive tasks.
-			 *
-			 * The boost works by updating the 'average sleep time'
-			 * value here, based on ->timestamp. The more time a
-			 * task spends sleeping, the higher the average gets -
-			 * and the higher the priority boost gets as well.
-			 */
-			p->sleep_avg += sleep_time;
-
-		}
-		if (p->sleep_avg > NS_MAX_SLEEP_AVG)
-			p->sleep_avg = NS_MAX_SLEEP_AVG;
-	}
-
-	return effective_prio(p);
+	if (nice < 0 && !rt_task(p))
+		return RR_INTERVAL * (20 - nice) / 20;
+	return RR_INTERVAL;
 }
 
 /*
  * activate_task - move a task to the runqueue and do priority recalculation
- *
- * Update all the scheduling statistics stuff. (sleep average
- * calculation, priority modifiers, etc.)
  */
 static void activate_task(struct task_struct *p, struct rq *rq, int local)
 {
-	unsigned long long now;
-
-	if (rt_task(p))
-		goto out;
+	unsigned long long now = sched_clock();
 
-	now = sched_clock();
 #ifdef CONFIG_SMP
 	if (!local) {
 		/* Compensate for drifting sched_clock */
@@ -967,32 +926,9 @@ static void activate_task(struct task_st
 				     (now - p->timestamp) >> 20);
 	}
 
-	p->prio = recalc_task_prio(p, now);
-
-	/*
-	 * This checks to make sure it's not an uninterruptible task
-	 * that is now waking up.
-	 */
-	if (p->sleep_type == SLEEP_NORMAL) {
-		/*
-		 * Tasks which were woken up by interrupts (ie. hw events)
-		 * are most likely of interactive nature. So we give them
-		 * the credit of extending their sleep time to the period
-		 * of time they spend on the runqueue, waiting for execution
-		 * on a CPU, first time around:
-		 */
-		if (in_interrupt())
-			p->sleep_type = SLEEP_INTERRUPTED;
-		else {
-			/*
-			 * Normal first-time wakeups get a credit too for
-			 * on-runqueue time, but it will be weighted down:
-			 */
-			p->sleep_type = SLEEP_INTERACTIVE;
-		}
-	}
+	p->quota = rr_interval(p);
+	p->prio = effective_prio(p);
 	p->timestamp = now;
-out:
 	__activate_task(p, rq);
 }
 
@@ -1002,8 +938,7 @@ out:
 static void deactivate_task(struct task_struct *p, struct rq *rq)
 {
 	dec_nr_running(p, rq);
-	dequeue_task(p, p->array);
-	p->array = NULL;
+	dequeue_task(p, rq);
 }
 
 /*
@@ -1085,7 +1020,7 @@ migrate_task(struct task_struct *p, int 
 	 * If the task is not on a runqueue (and not running), then
 	 * it is sufficient to simply update the task's cpu field.
 	 */
-	if (!p->array && !task_running(rq, p)) {
+	if (!task_queued(p) && !task_running(rq, p)) {
 		set_task_cpu(p, dest_cpu);
 		return 0;
 	}
@@ -1116,7 +1051,7 @@ void wait_task_inactive(struct task_stru
 repeat:
 	rq = task_rq_lock(p, &flags);
 	/* Must be off runqueue entirely, not preempted. */
-	if (unlikely(p->array || task_running(rq, p))) {
+	if (unlikely(task_queued(p) || task_running(rq, p))) {
 		/* If it's preempted, we yield.  It could be a while. */
 		preempted = !task_running(rq, p);
 		task_rq_unlock(rq, &flags);
@@ -1381,6 +1316,20 @@ static inline int wake_idle(int cpu, str
 }
 #endif
 
+static inline int task_preempts_curr(struct task_struct *p, struct rq *rq)
+{
+	struct task_struct *curr = rq->curr;
+
+	return ((p->array == task_rq(p)->active &&
+		TASK_PREEMPTS_CURR(p, curr)) || curr == rq->idle);
+}
+
+static inline void try_preempt(struct task_struct *p, struct rq *rq)
+{
+	if (task_preempts_curr(p, rq))
+		resched_task(rq->curr);
+}
+
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
@@ -1412,7 +1361,7 @@ static int try_to_wake_up(struct task_st
 	if (!(old_state & state))
 		goto out;
 
-	if (p->array)
+	if (task_queued(p))
 		goto out_running;
 
 	cpu = task_cpu(p);
@@ -1505,7 +1454,7 @@ out_set_cpu:
 		old_state = p->state;
 		if (!(old_state & state))
 			goto out;
-		if (p->array)
+		if (task_queued(p))
 			goto out_running;
 
 		this_cpu = smp_processor_id();
@@ -1514,26 +1463,10 @@ out_set_cpu:
 
 out_activate:
 #endif /* CONFIG_SMP */
-	if (old_state == TASK_UNINTERRUPTIBLE) {
+	if (old_state == TASK_UNINTERRUPTIBLE)
 		rq->nr_uninterruptible--;
-		/*
-		 * Tasks on involuntary sleep don't earn
-		 * sleep_avg beyond just interactive state.
-		 */
-		p->sleep_type = SLEEP_NONINTERACTIVE;
-	} else
 
 	/*
-	 * Tasks that have marked their sleep as noninteractive get
-	 * woken up with their sleep average not weighted in an
-	 * interactive way.
-	 */
-		if (old_state & TASK_NONINTERACTIVE)
-			p->sleep_type = SLEEP_NONINTERACTIVE;
-
-
-	activate_task(p, rq, cpu == this_cpu);
-	/*
 	 * Sync wakeups (i.e. those types of wakeups where the waker
 	 * has indicated that it will leave the CPU in short order)
 	 * don't trigger a preemption, if the woken up task will run on
@@ -1541,10 +1474,9 @@ out_activate:
 	 * the waker guarantees that the freshly woken up task is going
 	 * to be considered on this CPU.)
 	 */
-	if (!sync || cpu != this_cpu) {
-		if (TASK_PREEMPTS_CURR(p, rq))
-			resched_task(rq->curr);
-	}
+	activate_task(p, rq, cpu == this_cpu);
+	if (!sync || cpu != this_cpu)
+		try_preempt(p, rq);
 	success = 1;
 
 out_running:
@@ -1567,7 +1499,7 @@ int fastcall wake_up_state(struct task_s
 	return try_to_wake_up(p, state, 0);
 }
 
-static void task_running_tick(struct rq *rq, struct task_struct *p);
+static void task_expired_entitlement(struct rq *rq, struct task_struct *p);
 /*
  * Perform scheduler related setup for a newly forked process p.
  * p is forked by current.
@@ -1595,7 +1527,6 @@ void fastcall sched_fork(struct task_str
 	p->prio = current->normal_prio;
 
 	INIT_LIST_HEAD(&p->run_list);
-	p->array = NULL;
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
 	if (unlikely(sched_info_on()))
 		memset(&p->sched_info, 0, sizeof(p->sched_info));
@@ -1607,6 +1538,8 @@ void fastcall sched_fork(struct task_str
 	/* Want to start with kernel preemption disabled. */
 	task_thread_info(p)->preempt_count = 1;
 #endif
+	if (unlikely(p->policy == SCHED_FIFO))
+		goto out;
 	/*
 	 * Share the timeslice between parent and child, thus the
 	 * total amount of pending timeslices in the system doesn't change,
@@ -1621,16 +1554,19 @@ void fastcall sched_fork(struct task_str
 	p->first_time_slice = 1;
 	current->time_slice >>= 1;
 	p->timestamp = sched_clock();
-	if (unlikely(!current->time_slice)) {
+	if (!current->time_slice) {
 		/*
-		 * This case is rare, it happens when the parent has only
-		 * a single jiffy left from its timeslice. Taking the
-		 * runqueue lock is not a problem.
+		 * This case happens when the parent has only a single jiffy
+		 * left from its timeslice. Taking the runqueue lock is not
+		 * a problem.
 		 */
-		current->time_slice = 1;
-		task_running_tick(cpu_rq(cpu), current);
+		struct rq *rq = __task_rq_lock(current);
+
+		task_expired_entitlement(rq, current);
+		__task_rq_unlock(rq);
 	}
 	local_irq_enable();
+out:
 	put_cpu();
 }
 
@@ -1652,38 +1588,16 @@ void fastcall wake_up_new_task(struct ta
 	this_cpu = smp_processor_id();
 	cpu = task_cpu(p);
 
-	/*
-	 * We decrease the sleep average of forking parents
-	 * and children as well, to keep max-interactive tasks
-	 * from forking tasks that are max-interactive. The parent
-	 * (current) is done further down, under its lock.
-	 */
-	p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
-		CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-
-	p->prio = effective_prio(p);
-
 	if (likely(cpu == this_cpu)) {
+		activate_task(p, rq, 1);
 		if (!(clone_flags & CLONE_VM)) {
 			/*
 			 * The VM isn't cloned, so we're in a good position to
 			 * do child-runs-first in anticipation of an exec. This
 			 * usually avoids a lot of COW overhead.
 			 */
-			if (unlikely(!current->array))
-				__activate_task(p, rq);
-			else {
-				p->prio = current->prio;
-				p->normal_prio = current->normal_prio;
-				list_add_tail(&p->run_list, &current->run_list);
-				p->array = current->array;
-				p->array->nr_active++;
-				inc_nr_running(p, rq);
-			}
 			set_need_resched();
-		} else
-			/* Run child last */
-			__activate_task(p, rq);
+		}
 		/*
 		 * We skip the following code due to cpu == this_cpu
 	 	 *
@@ -1700,19 +1614,16 @@ void fastcall wake_up_new_task(struct ta
 		 */
 		p->timestamp = (p->timestamp - this_rq->most_recent_timestamp)
 					+ rq->most_recent_timestamp;
-		__activate_task(p, rq);
-		if (TASK_PREEMPTS_CURR(p, rq))
-			resched_task(rq->curr);
+		activate_task(p, rq, 0);
+		try_preempt(p, rq);
 
 		/*
 		 * Parent and child are on different CPUs, now get the
-		 * parent runqueue to update the parent's ->sleep_avg:
+		 * parent runqueue to update the parent's ->flags:
 		 */
 		task_rq_unlock(rq, &flags);
 		this_rq = task_rq_lock(current, &flags);
 	}
-	current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
-		PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
 	task_rq_unlock(this_rq, &flags);
 }
 
@@ -1730,20 +1641,12 @@ void fastcall sched_exit(struct task_str
 	unsigned long flags;
 	struct rq *rq;
 
-	/*
-	 * If the child was a (relative-) CPU hog then decrease
-	 * the sleep_avg of the parent as well.
-	 */
 	rq = task_rq_lock(p->parent, &flags);
 	if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
 		p->parent->time_slice += p->time_slice;
-		if (unlikely(p->parent->time_slice > task_timeslice(p)))
-			p->parent->time_slice = task_timeslice(p);
+		if (unlikely(p->parent->time_slice > p->quota))
+			p->parent->time_slice = p->quota;
 	}
-	if (p->sleep_avg < p->parent->sleep_avg)
-		p->parent->sleep_avg = p->parent->sleep_avg /
-		(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
-		(EXIT_WEIGHT + 1);
 	task_rq_unlock(rq, &flags);
 }
 
@@ -2070,21 +1973,27 @@ void sched_exec(void)
  */
 static void pull_task(struct rq *src_rq, struct prio_array *src_array,
 		      struct task_struct *p, struct rq *this_rq,
-		      struct prio_array *this_array, int this_cpu)
+		      int this_cpu)
 {
-	dequeue_task(p, src_array);
+	dequeue_task(p, src_rq);
 	dec_nr_running(p, src_rq);
 	set_task_cpu(p, this_cpu);
 	inc_nr_running(p, this_rq);
-	enqueue_task(p, this_array);
+
+	/*
+	 * If this task has already been running on src_rq this priority
+	 * cycle, make the new runqueue think it has been on its cycle
+	 */
+	if (p->rotation == src_rq->prio_rotation)
+		p->rotation = this_rq->prio_rotation;
+	enqueue_task(p, this_rq);
 	p->timestamp = (p->timestamp - src_rq->most_recent_timestamp)
 				+ this_rq->most_recent_timestamp;
 	/*
 	 * Note that idle threads have a prio of MAX_PRIO, for this test
 	 * to be always true for them.
 	 */
-	if (TASK_PREEMPTS_CURR(p, this_rq))
-		resched_task(this_rq->curr);
+	try_preempt(p, this_rq);
 }
 
 /*
@@ -2127,8 +2036,6 @@ int can_migrate_task(struct task_struct 
 	return 1;
 }
 
-#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
-
 /*
  * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
  * load from busiest to this_rq, as part of a balancing operation within
@@ -2141,9 +2048,9 @@ static int move_tasks(struct rq *this_rq
 		      struct sched_domain *sd, enum idle_type idle,
 		      int *all_pinned)
 {
-	int idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
+	int idx, test_idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
 	    best_prio_seen, skip_for_load;
-	struct prio_array *array, *dst_array;
+	struct prio_array *array;
 	struct list_head *head, *curr;
 	struct task_struct *tmp;
 	long rem_load_move;
@@ -2153,8 +2060,8 @@ static int move_tasks(struct rq *this_rq
 
 	rem_load_move = max_load_move;
 	pinned = 1;
-	this_best_prio = rq_best_prio(this_rq);
-	best_prio = rq_best_prio(busiest);
+	this_best_prio = this_rq->curr->prio;
+	best_prio = busiest->curr->prio;
 	/*
 	 * Enable handling of the case where there is more than one task
 	 * with the best priority.   If the current running task is one
@@ -2168,32 +2075,35 @@ static int move_tasks(struct rq *this_rq
 	 * We first consider expired tasks. Those will likely not be
 	 * executed in the near future, and they are most likely to
 	 * be cache-cold, thus switching CPUs has the least effect
-	 * on them.
+	 * on them. This is done by starting the search at priority
+	 * MAX_PRIO since expired bits are MAX_PRIO...MAX_DYN_PRIO-1
 	 */
-	if (busiest->expired->nr_active) {
-		array = busiest->expired;
-		dst_array = this_rq->expired;
-	} else {
-		array = busiest->active;
-		dst_array = this_rq->active;
-	}
-
-new_array:
-	/* Start searching at priority 0: */
-	idx = 0;
+	array = busiest->expired;
+	test_idx = MAX_PRIO;
 skip_bitmap:
-	if (!idx)
-		idx = sched_find_first_bit(array->bitmap);
+	if (!test_idx)
+		idx = sched_find_first_bit(busiest->dyn_bitmap);
 	else
-		idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
-	if (idx >= MAX_PRIO) {
-		if (array == busiest->expired && busiest->active->nr_active) {
+		idx = find_next_bit(busiest->dyn_bitmap, MAX_DYN_PRIO,
+		      test_idx);
+	if (idx >= MAX_DYN_PRIO) {
+		if (array == busiest->expired) {
 			array = busiest->active;
-			dst_array = this_rq->active;
-			goto new_array;
+			test_idx = 0;
+			goto skip_bitmap;
 		}
 		goto out;
 	}
+	test_idx = idx;
+	if (idx >= MAX_PRIO) {
+		if (array == busiest->active)
+			goto out;
+		idx -= PRIO_RANGE;
+	}
+	if (list_empty(array->queue + idx)) {
+		__clear_bit(test_idx, busiest->dyn_bitmap);
+		goto skip_bitmap;
+	}
 
 	head = array->queue + idx;
 	curr = head->prev;
@@ -2216,11 +2126,11 @@ skip_queue:
 		best_prio_seen |= idx == best_prio;
 		if (curr != head)
 			goto skip_queue;
-		idx++;
+		test_idx++;
 		goto skip_bitmap;
 	}
 
-	pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
+	pull_task(busiest, array, tmp, this_rq, this_cpu);
 	pulled++;
 	rem_load_move -= tmp->load_weight;
 
@@ -2233,7 +2143,7 @@ skip_queue:
 			this_best_prio = idx;
 		if (curr != head)
 			goto skip_queue;
-		idx++;
+		test_idx++;
 		goto skip_bitmap;
 	}
 out:
@@ -3036,27 +2946,6 @@ unsigned long long current_sched_time(co
 }
 
 /*
- * We place interactive tasks back into the active array, if possible.
- *
- * To guarantee that this does not starve expired tasks we ignore the
- * interactivity of a task if the first expired task had to wait more
- * than a 'reasonable' amount of time. This deadline timeout is
- * load-dependent, as the frequency of array switched decreases with
- * increasing number of running tasks. We also ignore the interactivity
- * if a better static_prio task has expired:
- */
-static inline int expired_starving(struct rq *rq)
-{
-	if (rq->curr->static_prio > rq->best_expired_prio)
-		return 1;
-	if (!STARVATION_LIMIT || !rq->expired_timestamp)
-		return 0;
-	if (jiffies - rq->expired_timestamp > STARVATION_LIMIT * rq->nr_running)
-		return 1;
-	return 0;
-}
-
-/*
  * Account user cpu time to a process.
  * @p: the process that the cpu time gets accounted to
  * @hardirq_offset: the offset to subtract from hardirq_count()
@@ -3129,87 +3018,137 @@ void account_steal_time(struct task_stru
 		cpustat->steal = cputime64_add(cpustat->steal, tmp);
 }
 
+/*
+ * The task has used up its quota of running in this prio_level so it must be
+ * dropped a priority level, all managed by recalc_task_prio().
+ */
+static void task_expired_entitlement(struct rq *rq, struct task_struct *p)
+{
+	struct prio_array *old_array;
+	int old_prio;
+
+	set_tsk_need_resched(p);
+	if (unlikely(p->first_time_slice))
+		p->first_time_slice = 0;
+	if (rt_task(p)) {
+		p->time_slice = p->quota;
+		return;
+	}
+	old_array = p->array;
+	old_prio = p->prio;
+	/* p->prio and p->array will be updated in recalc_task_prio */
+	recalc_task_prio(p, rq);
+	requeue_task(p, rq, old_array, old_prio);
+}
+
+/*
+ * A major priority rotation occurs when all priority quotas for this array
+ * have been exhausted.
+ */
+static inline void major_prio_rotation(struct rq *rq)
+{
+	struct prio_array *new_array = rq->expired;
+
+	rq->expired = rq->active;
+	rq->active = new_array;
+	rq->prio_rotation++;
+	bitmap_zero(rq->dyn_bitmap, MAX_DYN_PRIO);
+	bitmap_copy(rq->dyn_bitmap, rq->static_bitmap, MAX_PRIO);
+	__set_bit(MAX_DYN_PRIO, rq->dyn_bitmap);
+}
+
+/*
+ * This is the heart of the virtual deadline priority management.
+ *
+ * We have used up the quota allocated to this priority level so we rotate
+ * the prio_level of the runqueue to the next lowest priority. We merge any
+ * remaining tasks at this level current_queue with the next priority and
+ * reset this level's queue. MAX_PRIO - 1 is a special case where we perform
+ * a major rotation.
+ */
+static inline void rotate_runqueue_priority(struct rq *rq)
+{
+	int new_prio_level, remaining_quota = rq_quota(rq, rq->prio_level);
+	struct prio_array *array = rq->active;
+
+	if (rq->prio_level > MAX_PRIO - 2) {
+		/* Major rotation required */
+		struct prio_array *new_queue = rq->expired;
+
+		/*
+		 * The static_bitmap gives us the highest p->static prio task
+		 * that is queued. This value is used as the prio after
+		 * the major rotation and all tasks remaining on this
+		 * active queue are moved there. This means tasks can end
+		 * up a p->prio better than their p->static_prio.
+		 */
+		new_prio_level = find_next_bit(rq->static_bitmap, MAX_PRIO,
+				 MAX_RT_PRIO);
+		if (!list_empty(array->queue + rq->prio_level)) {
+			list_splice_tail_init(array->queue + rq->prio_level,
+					 new_queue->queue + new_prio_level);
+		}
+		memset(rq->prio_quota, 0, ARRAY_SIZE(rq->prio_quota));
+		major_prio_rotation(rq);
+	} else {
+		/* Minor rotation */
+		new_prio_level = rq->prio_level + 1;
+		__clear_bit(rq->prio_level, rq->dyn_bitmap);
+		if (!list_empty(array->queue + rq->prio_level)) {
+			list_splice_tail_init(array->queue + rq->prio_level,
+					 array->queue + new_prio_level);
+			__set_bit(new_prio_level, rq->dyn_bitmap);
+		}
+		rq_quota(rq, rq->prio_level) = 0;
+	}
+	rq->prio_level = new_prio_level;
+	/*
+	 * While we usually rotate with the rq quota being 0, it is possible
+	 * to be negative so we subtract any deficit from the new level.
+	 */
+	rq_quota(rq, new_prio_level) += remaining_quota;
+}
+
 static void task_running_tick(struct rq *rq, struct task_struct *p)
 {
-	if (p->array != rq->active) {
+	if (unlikely(!task_queued(p))) {
 		/* Task has expired but was not scheduled yet */
 		set_tsk_need_resched(p);
 		return;
 	}
+	/* SCHED_FIFO tasks never run out of timeslice. */
+	if (unlikely(p->policy == SCHED_FIFO))
+		return;
+
 	spin_lock(&rq->lock);
 	/*
-	 * The task was running during this tick - update the
-	 * time slice counter. Note: we do not update a thread's
-	 * priority until it either goes to sleep or uses up its
-	 * timeslice. This makes it possible for interactive tasks
-	 * to use up their timeslices at their highest priority levels.
+	 * Accounting is performed by both the task and the runqueue. This
+	 * allows frequently sleeping tasks to get their proper quota of
+	 * cpu as the runqueue will have their quota still available at
+	 * the appropriate priority level. It also means frequently waking
+	 * tasks that might miss the scheduler_tick() will get forced down
+	 * priority regardless.
+	 */
+	if (!--p->time_slice)
+		task_expired_entitlement(rq, p);
+	/*
+	 * The rq quota can become negative due to a task being queued in
+	 * scheduler without any quota left at that priority level. It is
+	 * cheaper to allow it to run till this scheduler tick and then
+	 * subtract it from the quota of the merged queues.
 	 */
-	if (rt_task(p)) {
-		/*
-		 * RR tasks need a special form of timeslice management.
-		 * FIFO tasks have no timeslices.
-		 */
-		if ((p->policy == SCHED_RR) && !--p->time_slice) {
-			p->time_slice = task_timeslice(p);
+	if (!rt_task(p) && --rq_quota(rq, rq->prio_level) <= 0) {
+		if (unlikely(p->first_time_slice))
 			p->first_time_slice = 0;
-			set_tsk_need_resched(p);
-
-			/* put it at the end of the queue: */
-			requeue_task(p, rq->active);
-		}
-		goto out_unlock;
-	}
-	if (!--p->time_slice) {
-		dequeue_task(p, rq->active);
+		rotate_runqueue_priority(rq);
 		set_tsk_need_resched(p);
-		p->prio = effective_prio(p);
-		p->time_slice = task_timeslice(p);
-		p->first_time_slice = 0;
-
-		if (!rq->expired_timestamp)
-			rq->expired_timestamp = jiffies;
-		if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
-			enqueue_task(p, rq->expired);
-			if (p->static_prio < rq->best_expired_prio)
-				rq->best_expired_prio = p->static_prio;
-		} else
-			enqueue_task(p, rq->active);
-	} else {
-		/*
-		 * Prevent a too long timeslice allowing a task to monopolize
-		 * the CPU. We do this by splitting up the timeslice into
-		 * smaller pieces.
-		 *
-		 * Note: this does not mean the task's timeslices expire or
-		 * get lost in any way, they just might be preempted by
-		 * another task of equal priority. (one with higher
-		 * priority would have preempted this task already.) We
-		 * requeue this task to the end of the list on this priority
-		 * level, which is in essence a round-robin of tasks with
-		 * equal priority.
-		 *
-		 * This only applies to tasks in the interactive
-		 * delta range with at least TIMESLICE_GRANULARITY to requeue.
-		 */
-		if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
-			p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
-			(p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
-			(p->array == rq->active)) {
-
-			requeue_task(p, rq->active);
-			set_tsk_need_resched(p);
-		}
 	}
-out_unlock:
 	spin_unlock(&rq->lock);
 }
 
 /*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.
- *
- * It also gets called by the fork code, when changing the parent's
- * timeslices.
  */
 void scheduler_tick(void)
 {
@@ -3271,6 +3210,12 @@ static void wake_sleeping_dependent(int 
 	}
 }
 
+static inline unsigned long remaining_slice(struct task_struct *p)
+{
+	return p->quota * (MAX_PRIO - 1 - p->prio) +
+		p->time_slice;
+}
+
 /*
  * number of 'lost' timeslices this task wont be able to fully
  * utilize, if another task runs on a sibling. This models the
@@ -3279,7 +3224,7 @@ static void wake_sleeping_dependent(int 
 static inline unsigned long
 smt_slice(struct task_struct *p, struct sched_domain *sd)
 {
-	return p->time_slice * (100 - sd->per_cpu_gain) / 100;
+	return remaining_slice(p) * (100 - sd->per_cpu_gain) / 100;
 }
 
 /*
@@ -3342,7 +3287,7 @@ dependent_sleeper(int this_cpu, struct r
 					ret = 1;
 		} else {
 			if (smt_curr->static_prio < p->static_prio &&
-				!TASK_PREEMPTS_CURR(p, smt_rq) &&
+				!task_preempts_curr(p, smt_rq) &&
 				smt_slice(smt_curr, sd) > task_timeslice(p))
 					ret = 1;
 		}
@@ -3400,10 +3345,98 @@ EXPORT_SYMBOL(sub_preempt_count);
 
 #endif
 
-static inline int interactive_sleep(enum sleep_type sleep_type)
+/*
+ * Leave this debugging in until we are certain all bitmap manipulations are
+ * working as desired since we can safely get out of this situation.
+ */
+static noinline int rq_bitmap_error(struct rq *rq)
+{
+	static int bitmap_error = 0;
+	struct prio_array *array;
+	struct list_head *queue;
+	int idx, test_idx;
+
+	if (!bitmap_error++)
+		printk(KERN_ERR "Scheduler bitmap error - bitmap being reconstructed..\n");
+	for (test_idx = MAX_RT_PRIO ; test_idx < MAX_DYN_PRIO ; test_idx++) {
+		if (test_idx < MAX_PRIO) {
+			idx = test_idx;
+			array = rq->active;
+		} else {
+			idx = test_idx - PRIO_RANGE;
+			array = rq->expired;
+		}
+		queue = array->queue + idx;
+		if (!list_empty(queue)) {
+			if (!test_bit(test_idx, rq->dyn_bitmap)) {
+				__set_bit(test_idx, rq->dyn_bitmap);
+			}
+		}
+	}
+	idx = find_next_bit(rq->dyn_bitmap, MAX_DYN_PRIO, MAX_RT_PRIO);
+	BUG_ON(idx == MAX_DYN_PRIO);
+	return idx;
+}
+
+/*
+ * next_dynamic_task finds the next suitable dynamic task. As the dyn_bitmap
+ * contains all the active and expired dynamic tasks sequentially we only
+ * need to do one bitmap lookup.
+ */
+static inline struct task_struct *next_dynamic_task(struct rq *rq, int idx)
 {
-	return (sleep_type == SLEEP_INTERACTIVE ||
-		sleep_type == SLEEP_INTERRUPTED);
+	struct task_struct *next;
+	struct list_head *queue;
+	struct prio_array *array = rq->active;
+
+retry:
+	if (unlikely(idx == MAX_DYN_PRIO))
+		idx = rq_bitmap_error(rq);
+	if (idx >= MAX_PRIO) {
+		/*
+		 * We have selected a bit from the expired range so there are
+		 * no more tasks in the active array.
+		 */
+		major_prio_rotation(rq);
+		array = rq->active;
+		idx -= PRIO_RANGE;
+	}
+	if (unlikely(list_empty(array->queue + idx))) {
+		/*
+		 * This can happen because they are not always cleared on
+		 * dequeue_task since they may have been dequeued while
+		 * waiting on a runqueue and a rotation has occurred in the
+		 * interim. A very rare occurrence.
+		 */
+		__clear_bit(idx, rq->dyn_bitmap);
+		idx = find_next_bit(rq->dyn_bitmap, MAX_DYN_PRIO, idx + 1);
+		goto retry;
+	}
+	queue = array->queue + idx;
+	next = list_entry(queue->next, struct task_struct, run_list);
+	/*
+	 * When the task is chosen it is checked to see if its quota has been
+	 * added to this runqueue level which is only performed once per
+	 * level per major rotation for each running task.
+	 */
+	if (next->rotation != rq->prio_rotation) {
+			/* Task has moved during major rotation */
+			task_new_array(next, rq);
+			set_task_entitlement(next);
+			rq_quota(rq, idx) += next->quota;
+	} else if (!test_bit(USER_PRIO(idx), next->bitmap)) {
+			/* Task has moved during minor rotation */
+			set_task_entitlement(next);
+			rq_quota(rq, idx) += next->quota;
+	}
+	rq->prio_level = idx;
+	/*
+	 * next needs to have its prio and array reset here in case the
+	 * values are wrong due to priority rotation.
+	 */
+	next->prio = idx;
+	next->array = array;
+	return next;
 }
 
 /*
@@ -3412,13 +3445,11 @@ static inline int interactive_sleep(enum
 asmlinkage void __sched schedule(void)
 {
 	struct task_struct *prev, *next;
-	struct prio_array *array;
 	struct list_head *queue;
 	unsigned long long now;
-	unsigned long run_time;
-	int cpu, idx, new_prio;
 	long *switch_count;
 	struct rq *rq;
+	int cpu, idx;
 
 	/*
 	 * Test if we are atomic.  Since do_exit() needs to call into
@@ -3454,18 +3485,6 @@ need_resched_nonpreemptible:
 
 	schedstat_inc(rq, sched_cnt);
 	now = sched_clock();
-	if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
-		run_time = now - prev->timestamp;
-		if (unlikely((long long)(now - prev->timestamp) < 0))
-			run_time = 0;
-	} else
-		run_time = NS_MAX_SLEEP_AVG;
-
-	/*
-	 * Tasks charged proportionately less run_time at high sleep_avg to
-	 * delay them losing their interactive status
-	 */
-	run_time /= (CURRENT_BONUS(prev) ? : 1);
 
 	spin_lock_irq(&rq->lock);
 
@@ -3487,47 +3506,19 @@ need_resched_nonpreemptible:
 		idle_balance(cpu, rq);
 		if (!rq->nr_running) {
 			next = rq->idle;
-			rq->expired_timestamp = 0;
 			wake_sleeping_dependent(cpu);
 			goto switch_tasks;
 		}
 	}
 
-	array = rq->active;
-	if (unlikely(!array->nr_active)) {
-		/*
-		 * Switch the active and expired arrays.
-		 */
-		schedstat_inc(rq, sched_switch);
-		rq->active = rq->expired;
-		rq->expired = array;
-		array = rq->active;
-		rq->expired_timestamp = 0;
-		rq->best_expired_prio = MAX_PRIO;
+	idx = sched_find_first_bit(rq->dyn_bitmap);
+	if (!rt_prio(idx))
+		next = next_dynamic_task(rq, idx);
+	else {
+		queue = rq->active->queue + idx;
+		next = list_entry(queue->next, struct task_struct, run_list);
 	}
 
-	idx = sched_find_first_bit(array->bitmap);
-	queue = array->queue + idx;
-	next = list_entry(queue->next, struct task_struct, run_list);
-
-	if (!rt_task(next) && interactive_sleep(next->sleep_type)) {
-		unsigned long long delta = now - next->timestamp;
-		if (unlikely((long long)(now - next->timestamp) < 0))
-			delta = 0;
-
-		if (next->sleep_type == SLEEP_INTERACTIVE)
-			delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
-
-		array = next->array;
-		new_prio = recalc_task_prio(next, next->timestamp + delta);
-
-		if (unlikely(next->prio != new_prio)) {
-			dequeue_task(next, array);
-			next->prio = new_prio;
-			enqueue_task(next, array);
-		}
-	}
-	next->sleep_type = SLEEP_NORMAL;
 	if (dependent_sleeper(cpu, rq, next))
 		next = rq->idle;
 switch_tasks:
@@ -3539,10 +3530,6 @@ switch_tasks:
 	rcu_qsctr_inc(task_cpu(prev));
 
 	update_cpu_clock(prev, rq, now);
-
-	prev->sleep_avg -= run_time;
-	if ((long)prev->sleep_avg <= 0)
-		prev->sleep_avg = 0;
 	prev->timestamp = prev->last_ran = now;
 
 	sched_info_switch(prev, next);
@@ -3978,29 +3965,21 @@ EXPORT_SYMBOL(sleep_on_timeout);
  */
 void rt_mutex_setprio(struct task_struct *p, int prio)
 {
-	struct prio_array *array;
 	unsigned long flags;
+	int queued, oldprio;
 	struct rq *rq;
-	int oldprio;
 
 	BUG_ON(prio < 0 || prio > MAX_PRIO);
 
 	rq = task_rq_lock(p, &flags);
 
 	oldprio = p->prio;
-	array = p->array;
-	if (array)
-		dequeue_task(p, array);
+	if ((queued = task_queued(p)))
+		dequeue_task(p, rq);
 	p->prio = prio;
 
-	if (array) {
-		/*
-		 * If changing to an RT priority then queue it
-		 * in the active array!
-		 */
-		if (rt_task(p))
-			array = rq->active;
-		enqueue_task(p, array);
+	if (queued) {
+		enqueue_task(p, rq);
 		/*
 		 * Reschedule if we are currently running on this runqueue and
 		 * our priority decreased, or if we are not currently running on
@@ -4009,8 +3988,8 @@ void rt_mutex_setprio(struct task_struct
 		if (task_running(rq, p)) {
 			if (p->prio > oldprio)
 				resched_task(rq->curr);
-		} else if (TASK_PREEMPTS_CURR(p, rq))
-			resched_task(rq->curr);
+		} else
+			try_preempt(p, rq);
 	}
 	task_rq_unlock(rq, &flags);
 }
@@ -4019,8 +3998,7 @@ void rt_mutex_setprio(struct task_struct
 
 void set_user_nice(struct task_struct *p, long nice)
 {
-	struct prio_array *array;
-	int old_prio, delta;
+	int queued, old_prio,delta;
 	unsigned long flags;
 	struct rq *rq;
 
@@ -4041,9 +4019,8 @@ void set_user_nice(struct task_struct *p
 		p->static_prio = NICE_TO_PRIO(nice);
 		goto out_unlock;
 	}
-	array = p->array;
-	if (array) {
-		dequeue_task(p, array);
+	if ((queued = task_queued(p))) {
+		dequeue_task(p, rq);
 		dec_raw_weighted_load(rq, p);
 	}
 
@@ -4053,8 +4030,8 @@ void set_user_nice(struct task_struct *p
 	p->prio = effective_prio(p);
 	delta = p->prio - old_prio;
 
-	if (array) {
-		enqueue_task(p, array);
+	if (queued) {
+		enqueue_task(p, rq);
 		inc_raw_weighted_load(rq, p);
 		/*
 		 * If the task increased its priority or is running and
@@ -4130,7 +4107,7 @@ asmlinkage long sys_nice(int increment)
  *
  * This is the priority value as seen by users in /proc.
  * RT tasks are offset by -200. Normal tasks are centered
- * around 0, value goes from -16 to +15.
+ * around 0, value goes from 0 to +19.
  */
 int task_prio(const struct task_struct *p)
 {
@@ -4177,18 +4154,13 @@ static inline struct task_struct *find_p
 /* Actually do priority change: must hold rq lock. */
 static void __setscheduler(struct task_struct *p, int policy, int prio)
 {
-	BUG_ON(p->array);
+	BUG_ON(task_queued(p));
 
 	p->policy = policy;
 	p->rt_priority = prio;
 	p->normal_prio = normal_prio(p);
 	/* we are holding p->pi_lock already */
 	p->prio = rt_mutex_getprio(p);
-	/*
-	 * SCHED_BATCH tasks are treated as perpetual CPU hogs:
-	 */
-	if (policy == SCHED_BATCH)
-		p->sleep_avg = 0;
 	set_load_weight(p);
 }
 
@@ -4204,8 +4176,7 @@ static void __setscheduler(struct task_s
 int sched_setscheduler(struct task_struct *p, int policy,
 		       struct sched_param *param)
 {
-	int retval, oldprio, oldpolicy = -1;
-	struct prio_array *array;
+	int queued, retval, oldprio, oldpolicy = -1;
 	unsigned long flags;
 	struct rq *rq;
 
@@ -4279,12 +4250,11 @@ recheck:
 		spin_unlock_irqrestore(&p->pi_lock, flags);
 		goto recheck;
 	}
-	array = p->array;
-	if (array)
+	if ((queued = task_queued(p)))
 		deactivate_task(p, rq);
 	oldprio = p->prio;
 	__setscheduler(p, policy, param->sched_priority);
-	if (array) {
+	if (queued) {
 		__activate_task(p, rq);
 		/*
 		 * Reschedule if we are currently running on this runqueue and
@@ -4294,8 +4264,8 @@ recheck:
 		if (task_running(rq, p)) {
 			if (p->prio > oldprio)
 				resched_task(rq->curr);
-		} else if (TASK_PREEMPTS_CURR(p, rq))
-			resched_task(rq->curr);
+		} else
+			try_preempt(p, rq);
 	}
 	__task_rq_unlock(rq);
 	spin_unlock_irqrestore(&p->pi_lock, flags);
@@ -4568,13 +4538,14 @@ asmlinkage long sys_sched_getaffinity(pi
  * sys_sched_yield - yield the current processor to other threads.
  *
  * this function yields the current CPU by moving the calling thread
- * to the expired array. If there are no other threads running on this
- * CPU then this function will return.
+ * to the expired array.
  */
 asmlinkage long sys_sched_yield(void)
 {
 	struct rq *rq = this_rq_lock();
-	struct prio_array *array = current->array, *target = rq->expired;
+	struct task_struct *p = current;
+	struct prio_array *old_array = p->array;
+	int old_prio = p->prio;
 
 	schedstat_inc(rq, yld_cnt);
 	/*
@@ -4584,24 +4555,12 @@ asmlinkage long sys_sched_yield(void)
 	 * (special rule: RT tasks will just roundrobin in the active
 	 *  array.)
 	 */
-	if (rt_task(current))
-		target = rq->active;
-
-	if (array->nr_active == 1) {
-		schedstat_inc(rq, yld_act_empty);
-		if (!rq->expired->nr_active)
-			schedstat_inc(rq, yld_both_empty);
-	} else if (!rq->expired->nr_active)
-		schedstat_inc(rq, yld_exp_empty);
-
-	if (array != target) {
-		dequeue_task(current, array);
-		enqueue_task(current, target);
-	} else
-		/*
-		 * requeue_task is cheaper so perform that if possible.
-		 */
-		requeue_task(current, array);
+	if (!rt_task(p)) {
+		p->array = rq->expired;
+		p->prio = p->static_prio;
+		bitmap_zero(p->bitmap, PRIO_RANGE);
+	}
+	requeue_task(p, rq, old_array, old_prio);
 
 	/*
 	 * Since we are going to call schedule() anyway, there's
@@ -4940,8 +4899,8 @@ void __cpuinit init_idle(struct task_str
 	struct rq *rq = cpu_rq(cpu);
 	unsigned long flags;
 
+	bitmap_zero(idle->bitmap, PRIO_RANGE + 1);
 	idle->timestamp = sched_clock();
-	idle->sleep_avg = 0;
 	idle->array = NULL;
 	idle->prio = idle->normal_prio = MAX_PRIO;
 	idle->state = TASK_RUNNING;
@@ -5062,7 +5021,7 @@ static int __migrate_task(struct task_st
 		goto out;
 
 	set_task_cpu(p, dest_cpu);
-	if (p->array) {
+	if (task_queued(p)) {
 		/*
 		 * Sync timestamp with rq_dest's before activating.
 		 * The same thing could be achieved by doing this step
@@ -5073,8 +5032,7 @@ static int __migrate_task(struct task_st
 				+ rq_dest->most_recent_timestamp;
 		deactivate_task(p, rq_src);
 		__activate_task(p, rq_dest);
-		if (TASK_PREEMPTS_CURR(p, rq_dest))
-			resched_task(rq_dest->curr);
+		try_preempt(p, rq_dest);
 	}
 	ret = 1;
 out:
@@ -6904,9 +6862,10 @@ void __init sched_init(void)
 		spin_lock_init(&rq->lock);
 		lockdep_set_class(&rq->lock, &rq->rq_lock_key);
 		rq->nr_running = 0;
+		rq->prio_rotation = 0;
+		rq->prio_level = MAX_RT_PRIO;
 		rq->active = rq->arrays;
 		rq->expired = rq->arrays + 1;
-		rq->best_expired_prio = MAX_PRIO;
 
 #ifdef CONFIG_SMP
 		rq->sd = NULL;
@@ -6921,14 +6880,17 @@ void __init sched_init(void)
 		atomic_set(&rq->nr_iowait, 0);
 
 		for (j = 0; j < 2; j++) {
+
 			array = rq->arrays + j;
-			for (k = 0; k < MAX_PRIO; k++) {
+			for (k = 0; k < MAX_PRIO; k++)
 				INIT_LIST_HEAD(array->queue + k);
-				__clear_bit(k, array->bitmap);
-			}
-			// delimiter for bitsearch
-			__set_bit(MAX_PRIO, array->bitmap);
 		}
+		for (k = 0; k < PRIO_RANGE; k++)
+			rq->prio_quota[k] = 0;
+		bitmap_zero(rq->dyn_bitmap, MAX_DYN_PRIO);
+		bitmap_zero(rq->static_bitmap, MAX_PRIO);
+		/* delimiter for bitsearch */
+		__set_bit(MAX_DYN_PRIO, rq->dyn_bitmap);
 	}
 
 	set_load_weight(&init_task);
@@ -6984,10 +6946,10 @@ EXPORT_SYMBOL(__might_sleep);
 #ifdef CONFIG_MAGIC_SYSRQ
 void normalize_rt_tasks(void)
 {
-	struct prio_array *array;
 	struct task_struct *p;
 	unsigned long flags;
 	struct rq *rq;
+	int queued;
 
 	read_lock_irq(&tasklist_lock);
 	for_each_process(p) {
@@ -6997,11 +6959,10 @@ void normalize_rt_tasks(void)
 		spin_lock_irqsave(&p->pi_lock, flags);
 		rq = __task_rq_lock(p);
 
-		array = p->array;
-		if (array)
+		if ((queued = task_queued(p)))
 			deactivate_task(p, task_rq(p));
 		__setscheduler(p, SCHED_NORMAL, 0);
-		if (array) {
+		if (queued) {
 			__activate_task(p, task_rq(p));
 			resched_task(rq->curr);
 		}
Index: linux-2.6.20-rsdl/include/linux/init_task.h
===================================================================
--- linux-2.6.20-rsdl.orig/include/linux/init_task.h	2007-03-04 17:30:25.000000000 +1100
+++ linux-2.6.20-rsdl/include/linux/init_task.h	2007-03-04 17:30:31.000000000 +1100
@@ -102,6 +102,7 @@ extern struct group_info init_groups;
 	.prio		= MAX_PRIO-20,					\
 	.static_prio	= MAX_PRIO-20,					\
 	.normal_prio	= MAX_PRIO-20,					\
+	.rotation	= 0,						\
 	.policy		= SCHED_NORMAL,					\
 	.cpus_allowed	= CPU_MASK_ALL,					\
 	.mm		= NULL,						\
@@ -109,6 +110,7 @@ extern struct group_info init_groups;
 	.run_list	= LIST_HEAD_INIT(tsk.run_list),			\
 	.ioprio		= 0,						\
 	.time_slice	= HZ,						\
+	.quota		= HZ,						\
 	.tasks		= LIST_HEAD_INIT(tsk.tasks),			\
 	.ptrace_children= LIST_HEAD_INIT(tsk.ptrace_children),		\
 	.ptrace_list	= LIST_HEAD_INIT(tsk.ptrace_list),		\
Index: linux-2.6.20-rsdl/include/linux/sched.h
===================================================================
--- linux-2.6.20-rsdl.orig/include/linux/sched.h	2007-03-04 17:30:30.000000000 +1100
+++ linux-2.6.20-rsdl/include/linux/sched.h	2007-03-04 17:30:31.000000000 +1100
@@ -521,8 +521,9 @@ struct signal_struct {
 
 #define MAX_USER_RT_PRIO	100
 #define MAX_RT_PRIO		MAX_USER_RT_PRIO
+#define PRIO_RANGE		(40)
 
-#define MAX_PRIO		(MAX_RT_PRIO + 40)
+#define MAX_PRIO		(MAX_RT_PRIO + PRIO_RANGE)
 
 #define rt_prio(prio)		unlikely((prio) < MAX_RT_PRIO)
 #define rt_task(p)		rt_prio((p)->prio)
@@ -788,13 +789,6 @@ struct mempolicy;
 struct pipe_inode_info;
 struct uts_namespace;
 
-enum sleep_type {
-	SLEEP_NORMAL,
-	SLEEP_NONINTERACTIVE,
-	SLEEP_INTERACTIVE,
-	SLEEP_INTERRUPTED,
-};
-
 struct prio_array;
 
 struct task_struct {
@@ -814,20 +808,31 @@ struct task_struct {
 	int load_weight;	/* for niceness load balancing purposes */
 	int prio, static_prio, normal_prio;
 	struct list_head run_list;
+	DECLARE_BITMAP(bitmap, PRIO_RANGE + 1);
 	struct prio_array *array;
+	unsigned long rotation;
+	/* Which major runqueue rotation did this task run */
 
 	unsigned short ioprio;
 #ifdef CONFIG_BLK_DEV_IO_TRACE
 	unsigned int btrace_seq;
 #endif
-	unsigned long sleep_avg;
 	unsigned long long timestamp, last_ran;
 	unsigned long long sched_time; /* sched_clock time spent running */
-	enum sleep_type sleep_type;
 
 	unsigned long policy;
 	cpumask_t cpus_allowed;
 	unsigned int time_slice, first_time_slice;
+	/*
+	 * How much this task is entitled to run at the current priority
+	 * before being requeued at a lower priority, and is this the very
+	 * first time_slice this task has ever run.
+	 */
+	unsigned int quota;
+	/*
+	 * How much this task contributes to the current priority queue
+	 * length
+	 */
 
 #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
 	struct sched_info sched_info;

-- 
-ck
-
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