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Subject[PATCH] [RSDL 5/6] sched: implement rsdl cpu scheduler
Date
Implement the "Rotating Staircase DeadLine" RSDL cpu scheduler policy.

Signed-off-by: Con Kolivas <kernel@kolivas.org>

---
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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