[PATCH] Nick's scheduler policy v10

* [PATCH] Nick's scheduler policy v10
@ 2003-08-30  6:31 Nick Piggin
  2003-08-31 20:20 ` Martin J. Bligh
  2003-09-04 22:55 ` bill davidsen
  0 siblings, 2 replies; 13+ messages in thread
From: Nick Piggin @ 2003-08-30  6:31 UTC (permalink / raw)
  To: linux-kernel

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Hi,
This is quite a big change from v8. Fixes a few bugs in child priority,
and adds a small lower bound on the amount of history that is kept. This
should improve "fork something" times hopefully, and stops new children
being able to fluctuate priority so wildly.

Eliminates "timeslice backboost" and only uses "priority backboost". This
decreases scheduling latency quite nicely - I can only measure 130ms for
a very low priority task, with a make -j3 and wildly moving an xterm around
in front of a mozilla window.

Makes a fairly fundamental change to how sleeping/running is accounted.
It now takes into account time on the runqueue. This hopefully will keep
priorities more stable under varying loads.

Includes an upper bound on the amount of priority a task can get in one
sleep. Hopefully this catches freak long sleeps like a SIGSTOP or unexpected
swaps. This change breaks the priority calculation a little bit. I'm 
thinking
about how to fix it.

Feedback welcome! Its against 0-test4, as usual.



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--- archs/linux-2.6/include/linux/sched.h	2003-08-26 12:33:49.000000000 +1000
+++ linux-2.6/include/linux/sched.h	2003-08-25 20:31:50.000000000 +1000
@@ -281,7 +281,9 @@ struct signal_struct {
 #define MAX_RT_PRIO		MAX_USER_RT_PRIO
 
 #define MAX_PRIO		(MAX_RT_PRIO + 40)
- 
+
+#define rt_task(p)		((p)->prio < MAX_RT_PRIO)
+
 /*
  * Some day this will be a full-fledged user tracking system..
  */
@@ -339,12 +341,16 @@ struct task_struct {
 	struct list_head run_list;
 	prio_array_t *array;
 
+	unsigned long array_sequence;
+	unsigned long timestamp;
+
+	unsigned long total_time, sleep_time;
 	unsigned long sleep_avg;
-	unsigned long last_run;
 
 	unsigned long policy;
 	cpumask_t cpus_allowed;
 	unsigned int time_slice, first_time_slice;
+	unsigned int used_slice;
 
 	struct list_head tasks;
 	struct list_head ptrace_children;
@@ -552,6 +558,7 @@ extern int FASTCALL(wake_up_state(struct
 extern int FASTCALL(wake_up_process(struct task_struct * tsk));
 extern int FASTCALL(wake_up_process_kick(struct task_struct * tsk));
 extern void FASTCALL(wake_up_forked_process(struct task_struct * tsk));
+extern void FASTCALL(sched_fork(task_t * p));
 extern void FASTCALL(sched_exit(task_t * p));
 
 asmlinkage long sys_wait4(pid_t pid,unsigned int * stat_addr, int options, struct rusage * ru);
--- archs/linux-2.6/kernel/fork.c	2003-08-26 12:33:49.000000000 +1000
+++ linux-2.6/kernel/fork.c	2003-08-25 20:31:50.000000000 +1000
@@ -911,33 +911,9 @@ struct task_struct *copy_process(unsigne
 	p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL);
 	p->pdeath_signal = 0;
 
-	/*
-	 * Share the timeslice between parent and child, thus the
-	 * total amount of pending timeslices in the system doesn't change,
-	 * resulting in more scheduling fairness.
-	 */
-	local_irq_disable();
-        p->time_slice = (current->time_slice + 1) >> 1;
-	/*
-	 * The remainder of the first timeslice might be recovered by
-	 * the parent if the child exits early enough.
-	 */
-	p->first_time_slice = 1;
-	current->time_slice >>= 1;
-	p->last_run = jiffies;
-	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.
-		 */
-		current->time_slice = 1;
-		preempt_disable();
-		scheduler_tick(0, 0);
-		local_irq_enable();
-		preempt_enable();
-	} else
-		local_irq_enable();
+	/* Perform scheduler related accounting */
+	sched_fork(p);
+
 	/*
 	 * Ok, add it to the run-queues and make it
 	 * visible to the rest of the system.
--- archs/linux-2.6/kernel/sched.c	2003-08-26 12:33:49.000000000 +1000
+++ linux-2.6/kernel/sched.c	2003-08-30 16:06:15.000000000 +1000
@@ -66,73 +66,24 @@
  * maximum timeslice is 200 msecs. Timeslices get refilled after
  * they expire.
  */
-#define MIN_TIMESLICE		( 10 * HZ / 1000)
-#define MAX_TIMESLICE		(200 * HZ / 1000)
-#define CHILD_PENALTY		50
-#define PARENT_PENALTY		100
-#define EXIT_WEIGHT		3
-#define PRIO_BONUS_RATIO	25
-#define INTERACTIVE_DELTA	2
-#define MAX_SLEEP_AVG		(10*HZ)
-#define STARVATION_LIMIT	(10*HZ)
-#define NODE_THRESHOLD		125
-
-/*
- * 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 SCALE(v1,v1_max,v2_max) \
-	(v1) * (v2_max) / (v1_max)
+#define MIN_TIMESLICE		((1 * HZ / 1000) ? 1 * HZ / 1000 : 1)
+#define MAX_TIMESLICE		(40 * MIN_TIMESLICE) /* This cannot be changed */
 
-#define DELTA(p) \
-	(SCALE(TASK_NICE(p), 40, MAX_USER_PRIO*PRIO_BONUS_RATIO/100) + \
-		INTERACTIVE_DELTA)
+#define MAX_SLEEP		(HZ)
+#define MAX_SLEEP_AFFECT	(MAX_SLEEP/2)
+#define MIN_HISTORY		(HZ/20)
+#define SLEEP_FACTOR		(1024)
 
-#define TASK_INTERACTIVE(p) \
-	((p)->prio <= (p)->static_prio - DELTA(p))
-
-/*
- * BASE_TIMESLICE scales user-nice values [ -20 ... 19 ]
- * to time slice values.
- *
- * 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.
- *
- * task_timeslice() is the interface that is used by the scheduler.
- */
-
-#define BASE_TIMESLICE(p) (MIN_TIMESLICE + \
-	((MAX_TIMESLICE - MIN_TIMESLICE) * (MAX_PRIO-1-(p)->static_prio)/(MAX_USER_PRIO - 1)))
+#define NODE_THRESHOLD		125
 
-static inline unsigned int task_timeslice(task_t *p)
-{
-	return BASE_TIMESLICE(p);
-}
+#define STIME_SLEEP		1
+#define STIME_RUN		2
+#define STIME_WAIT		3
+
+#define TASK_PREEMPTS_CURR(p, rq)			\
+	( (p)->prio < (rq)->curr->prio			\
+	 	|| ((p)->prio == (rq)->curr->prio	\
+			 && (p)->static_prio < (rq)->curr->static_prio) )
 
 /*
  * These are the runqueue data structures:
@@ -157,7 +108,8 @@ struct prio_array {
  */
 struct runqueue {
 	spinlock_t lock;
-	unsigned long nr_running, nr_switches, expired_timestamp,
+	unsigned long array_sequence;
+	unsigned long nr_running, nr_switches,
 			nr_uninterruptible;
 	task_t *curr, *idle;
 	struct mm_struct *prev_mm;
@@ -179,7 +131,6 @@ static DEFINE_PER_CPU(struct runqueue, r
 #define this_rq()		(&__get_cpu_var(runqueues))
 #define task_rq(p)		cpu_rq(task_cpu(p))
 #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
-#define rt_task(p)		((p)->prio < MAX_RT_PRIO)
 
 /*
  * Default context-switch locking:
@@ -298,35 +249,76 @@ static inline void enqueue_task(struct t
 	p->array = array;
 }
 
+static void add_task_time(task_t *p, unsigned long time, unsigned long type)
+{
+	unsigned long r;
+
+	if (time == 0)
+		return;
+
+	if (time > MAX_SLEEP_AFFECT)
+		time = MAX_SLEEP_AFFECT;
+
+	r = MAX_SLEEP - time;
+	p->total_time = (r*p->total_time + MAX_SLEEP/2) / MAX_SLEEP;
+	p->sleep_time = (r*p->sleep_time + MAX_SLEEP/2) / MAX_SLEEP;
+
+	if (type != STIME_WAIT)
+		p->total_time += SLEEP_FACTOR * time;
+	if (type == STIME_SLEEP)
+		p->sleep_time += SLEEP_FACTOR * time;
+
+	p->sleep_avg = (SLEEP_FACTOR * p->sleep_time) / p->total_time;
+
+	if (p->total_time < SLEEP_FACTOR * MIN_HISTORY) {
+		p->total_time = SLEEP_FACTOR * MIN_HISTORY;
+		p->sleep_time = p->total_time * p->sleep_avg / SLEEP_FACTOR;
+	}
+}
+
 /*
- * effective_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.
+ * 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 int effective_prio(task_t *p)
+static unsigned int task_timeslice(task_t *p, runqueue_t *rq)
+{
+	int idx, delta;
+	unsigned int base, timeslice;
+
+	if (rt_task(p))
+		return MAX_TIMESLICE;
+	
+	idx = min(find_next_bit(rq->active->bitmap, MAX_PRIO, MAX_RT_PRIO),
+			find_next_bit(rq->expired->bitmap, MAX_PRIO, MAX_RT_PRIO));
+	idx = min(idx, p->prio);
+	delta = p->prio - idx;
+
+	base = MIN_TIMESLICE * (MAX_USER_PRIO + 1) / (delta + 2);
+	timeslice = base * (USER_PRIO(idx) + 8) / 8;
+
+	if (timeslice <= 0)
+		timeslice = 1;
+
+	return timeslice;
+}
+
+static unsigned long task_priority(task_t *p)
 {
 	int bonus, prio;
 
 	if (rt_task(p))
 		return p->prio;
 
-	bonus = MAX_USER_PRIO*PRIO_BONUS_RATIO*p->sleep_avg/MAX_SLEEP_AVG/100 -
-			MAX_USER_PRIO*PRIO_BONUS_RATIO/100/2;
+	bonus = (MAX_USER_PRIO * p->sleep_avg) / SLEEP_FACTOR / 2;
+	prio = USER_PRIO(p->static_prio) / 2 + (MAX_USER_PRIO / 2);
 
-	prio = p->static_prio - bonus;
+	prio = MAX_RT_PRIO + prio - bonus;
 	if (prio < MAX_RT_PRIO)
 		prio = MAX_RT_PRIO;
 	if (prio > MAX_PRIO-1)
 		prio = MAX_PRIO-1;
+
 	return prio;
 }
 
@@ -347,34 +339,29 @@ static inline void __activate_task(task_
  */
 static inline void activate_task(task_t *p, runqueue_t *rq)
 {
-	long sleep_time = jiffies - p->last_run - 1;
+	unsigned long sleep = jiffies - p->timestamp;
+	p->timestamp = jiffies;
 
-	if (sleep_time > 0) {
-		int sleep_avg;
+	if (sleep > MAX_SLEEP)
+		sleep = MAX_SLEEP;
 
-		/*
-		 * This code gives a bonus to interactive tasks.
-		 *
-		 * The boost works by updating the 'average sleep time'
-		 * value here, based on ->last_run. The more time a task
-		 * spends sleeping, the higher the average gets - and the
-		 * higher the priority boost gets as well.
-		 */
-		sleep_avg = p->sleep_avg + sleep_time;
+	if (!in_interrupt() && current->mm) {
+		unsigned long boost = sleep / 2;
+		add_task_time(current, boost, STIME_SLEEP);
+		add_task_time(p, sleep - boost, STIME_SLEEP);
+	} else {
+		add_task_time(p, sleep, STIME_SLEEP);
+		
+		if (in_interrupt())
+			add_task_time(p, sleep / 2, STIME_SLEEP);
+	}
 
-		/*
-		 * 'Overflow' bonus ticks go to the waker as well, so the
-		 * ticks are not lost. This has the effect of further
-		 * boosting tasks that are related to maximum-interactive
-		 * tasks.
-		 */
-		if (sleep_avg > MAX_SLEEP_AVG)
-			sleep_avg = MAX_SLEEP_AVG;
-		if (p->sleep_avg != sleep_avg) {
-			p->sleep_avg = sleep_avg;
-			p->prio = effective_prio(p);
-		}
+	p->prio = task_priority(p);
+
+	if (rq->array_sequence != p->array_sequence) {
+		p->used_slice = 0;
 	}
+
 	__activate_task(p, rq);
 }
 
@@ -383,6 +370,7 @@ static inline void activate_task(task_t 
  */
 static inline void deactivate_task(struct task_struct *p, runqueue_t *rq)
 {
+	p->array_sequence = rq->array_sequence;
 	nr_running_dec(rq);
 	if (p->state == TASK_UNINTERRUPTIBLE)
 		rq->nr_uninterruptible++;
@@ -426,7 +414,7 @@ static inline void resched_task(task_t *
  * be called with interrupts off, or it may introduce deadlock with
  * smp_call_function() if an IPI is sent by the same process we are
  * waiting to become inactive.
- */
+ n*/
 void wait_task_inactive(task_t * p)
 {
 	unsigned long flags;
@@ -497,11 +485,9 @@ repeat_lock_task:
 			}
 			if (old_state == TASK_UNINTERRUPTIBLE)
 				rq->nr_uninterruptible--;
-			if (sync)
-				__activate_task(p, rq);
-			else {
-				activate_task(p, rq);
-				if (p->prio < rq->curr->prio)
+			activate_task(p, rq);
+			if (!sync) {
+				if (TASK_PREEMPTS_CURR(p, rq))
 					resched_task(rq->curr);
 			}
 			success = 1;
@@ -534,36 +520,83 @@ int wake_up_state(task_t *p, unsigned in
 }
 
 /*
+ * Perform scheduler related accounting for a newly forked process @p.
+ * @p is forked by current.
+ */
+void sched_fork(task_t *p)
+{
+	unsigned long ts;
+	unsigned long flags;
+	runqueue_t *rq;
+
+	/*
+	 * Share the timeslice between parent and child, thus the
+	 * total amount of pending timeslices in the system doesn't change,
+	 * resulting in more scheduling fairness.
+	 */
+	local_irq_disable();
+	p->timestamp = jiffies;
+	rq = task_rq_lock(current, &flags);
+	ts = task_timeslice(current, rq);
+	task_rq_unlock(rq, &flags);
+	p->used_slice = current->used_slice + (ts - current->used_slice) / 2;
+	current->used_slice += (ts - current->used_slice + 1) / 2;
+	/*
+	 * The remainder of the first timeslice might be recovered by
+	 * the parent if the child exits early enough.
+	 */
+	p->first_time_slice = 1;
+	if (current->used_slice >= ts) {
+		/*
+	 	 * 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.
+		 */
+		current->used_slice = ts - 1;
+		preempt_disable();
+		scheduler_tick(0, 0);
+		local_irq_enable();
+		preempt_enable();
+	} else
+		local_irq_enable();
+}
+	
+/*
  * wake_up_forked_process - wake up a freshly forked process.
  *
  * This function will do some initial scheduler statistics housekeeping
  * that must be done for every newly created process.
  */
-void wake_up_forked_process(task_t * p)
+void wake_up_forked_process(task_t *p)
 {
 	unsigned long flags;
 	runqueue_t *rq = task_rq_lock(current, &flags);
 
 	p->state = TASK_RUNNING;
-	/*
-	 * We decrease the sleep average of forking parents
-	 * and children as well, to keep max-interactive tasks
-	 * from forking tasks that are max-interactive.
-	 */
-	current->sleep_avg = current->sleep_avg * PARENT_PENALTY / 100;
-	p->sleep_avg = p->sleep_avg * CHILD_PENALTY / 100;
-	p->prio = effective_prio(p);
+
 	set_task_cpu(p, smp_processor_id());
 
-	if (unlikely(!current->array))
-		__activate_task(p, rq);
-	else {
-		p->prio = current->prio;
-		list_add_tail(&p->run_list, &current->run_list);
-		p->array = current->array;
-		p->array->nr_active++;
-		nr_running_inc(rq);
+	p->total_time = current->total_time / 10;
+	p->sleep_time = current->sleep_time / 10
+			+ (current->total_time - current->sleep_time) / 20;
+	if (p->total_time != 0)
+		p->sleep_avg = (SLEEP_FACTOR * p->sleep_time) / p->total_time;
+	else
+		p->sleep_avg = SLEEP_FACTOR / 2;
+
+	if (p->total_time < SLEEP_FACTOR * MIN_HISTORY) {
+		p->total_time = SLEEP_FACTOR * MIN_HISTORY;
+		p->sleep_time = p->total_time * p->sleep_avg / SLEEP_FACTOR;
 	}
+
+	current->sleep_time = 3 * current->sleep_time / 4;
+	if (current->total_time != 0)
+		current->sleep_avg = (SLEEP_FACTOR * current->sleep_time)
+						/ current->total_time;
+
+	p->prio = task_priority(p);
+	__activate_task(p, rq);
+
 	task_rq_unlock(rq, &flags);
 }
 
@@ -582,18 +615,17 @@ void sched_exit(task_t * p)
 
 	local_irq_save(flags);
 	if (p->first_time_slice) {
-		p->parent->time_slice += p->time_slice;
-		if (unlikely(p->parent->time_slice > MAX_TIMESLICE))
-			p->parent->time_slice = MAX_TIMESLICE;
+		unsigned long flags;
+		runqueue_t *rq;
+		rq = task_rq_lock(p, &flags);
+		p->parent->used_slice -= task_timeslice(p, rq) - p->used_slice;
+		task_rq_unlock(rq, &flags);
 	}
-	local_irq_restore(flags);
-	/*
-	 * If the child was a (relative-) CPU hog then decrease
-	 * the sleep_avg of the parent as well.
-	 */
+
 	if (p->sleep_avg < p->parent->sleep_avg)
-		p->parent->sleep_avg = (p->parent->sleep_avg * EXIT_WEIGHT +
-			p->sleep_avg) / (EXIT_WEIGHT + 1);
+		add_task_time(p->parent, (p->parent->sleep_avg - p->sleep_avg)/2, STIME_RUN);
+	
+	local_irq_restore(flags);
 }
 
 /**
@@ -995,13 +1027,29 @@ static inline void pull_task(runqueue_t 
 	 * Note that idle threads have a prio of MAX_PRIO, for this test
 	 * to be always true for them.
 	 */
-	if (p->prio < this_rq->curr->prio)
+	if (TASK_PREEMPTS_CURR(p, this_rq))
 		set_need_resched();
-	else {
-		if (p->prio == this_rq->curr->prio &&
-				p->time_slice > this_rq->curr->time_slice)
-			set_need_resched();
-	}
+}
+
+/*
+ * comment me
+ */
+
+static inline int
+can_migrate_task(task_t *tsk, runqueue_t *rq, int this_cpu, int idle)
+{
+	unsigned long delta;
+
+	if (task_running(rq, tsk))
+		return 0;
+	if (!cpu_isset(this_cpu, tsk->cpus_allowed))
+		return 0;
+
+	delta = jiffies - tsk->timestamp;
+	if (idle && (delta <= cache_decay_ticks))
+		return 0;
+
+	return 1;
 }
 
 /*
@@ -1063,14 +1111,9 @@ skip_queue:
 	 * 3) are cache-hot on their current CPU.
 	 */
 
-#define CAN_MIGRATE_TASK(p,rq,this_cpu)					\
-	((!idle || (jiffies - (p)->last_run > cache_decay_ticks)) &&	\
-		!task_running(rq, p) &&					\
-			cpu_isset(this_cpu, (p)->cpus_allowed))
-
 	curr = curr->prev;
 
-	if (!CAN_MIGRATE_TASK(tmp, busiest, this_cpu)) {
+	if (!can_migrate_task(tmp, busiest, this_cpu, idle)) {
 		if (curr != head)
 			goto skip_queue;
 		idx++;
@@ -1171,20 +1214,6 @@ DEFINE_PER_CPU(struct kernel_stat, kstat
 EXPORT_PER_CPU_SYMBOL(kstat);
 
 /*
- * 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:
- */
-#define EXPIRED_STARVING(rq) \
-		(STARVATION_LIMIT && ((rq)->expired_timestamp && \
-		(jiffies - (rq)->expired_timestamp >= \
-			STARVATION_LIMIT * ((rq)->nr_running) + 1)))
-
-/*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.
  *
@@ -1201,17 +1230,11 @@ void scheduler_tick(int user_ticks, int 
 	if (rcu_pending(cpu))
 		rcu_check_callbacks(cpu, user_ticks);
 
-	/* note: this timer irq context must be accounted for as well */
-	if (hardirq_count() - HARDIRQ_OFFSET) {
-		cpustat->irq += sys_ticks;
-		sys_ticks = 0;
-	} else if (softirq_count()) {
-		cpustat->softirq += sys_ticks;
-		sys_ticks = 0;
-	}
-
 	if (p == rq->idle) {
-		if (atomic_read(&rq->nr_iowait) > 0)
+		/* note: this timer irq context must be accounted for as well */
+		if (irq_count() - HARDIRQ_OFFSET >= SOFTIRQ_OFFSET)
+			cpustat->system += sys_ticks;
+		else if (atomic_read(&rq->nr_iowait) > 0)
 			cpustat->iowait += sys_ticks;
 		else
 			cpustat->idle += sys_ticks;
@@ -1232,43 +1255,39 @@ void scheduler_tick(int user_ticks, int 
 	spin_lock(&rq->lock);
 	/*
 	 * The task was running during this tick - update the
-	 * time slice counter and the sleep average. 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.
+	 * time slice counter. Note: we do not update a thread's
+	 * priority until it either goes to sleep or uses up its
+	 * timeslice.
 	 */
-	if (p->sleep_avg)
-		p->sleep_avg--;
 	if (unlikely(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);
-			p->first_time_slice = 0;
-			set_tsk_need_resched(p);
-
-			/* put it at the end of the queue: */
-			dequeue_task(p, rq->active);
-			enqueue_task(p, rq->active);
+		if (p->policy == SCHED_RR) {
+			p->used_slice++;
+			if (p->used_slice >= task_timeslice(p, rq)) {
+				p->used_slice = 0;
+				p->first_time_slice = 0;
+				set_tsk_need_resched(p);
+
+				/* put it at the end of the queue: */
+				dequeue_task(p, rq->active);
+				enqueue_task(p, rq->active);
+			}
 		}
 		goto out_unlock;
 	}
-	if (!--p->time_slice) {
+
+	p->used_slice++;
+	if (p->used_slice >= task_timeslice(p, rq)) {
 		dequeue_task(p, rq->active);
 		set_tsk_need_resched(p);
-		p->prio = effective_prio(p);
-		p->time_slice = task_timeslice(p);
+		p->prio = task_priority(p);
+		p->used_slice = 0;
 		p->first_time_slice = 0;
 
-		if (!TASK_INTERACTIVE(p) || EXPIRED_STARVING(rq)) {
-			if (!rq->expired_timestamp)
-				rq->expired_timestamp = jiffies;
-			enqueue_task(p, rq->expired);
-		} else
-			enqueue_task(p, rq->active);
+		enqueue_task(p, rq->expired);
 	}
 out_unlock:
 	spin_unlock(&rq->lock);
@@ -1287,6 +1306,8 @@ asmlinkage void schedule(void)
 	runqueue_t *rq;
 	prio_array_t *array;
 	struct list_head *queue;
+	unsigned long now;
+	unsigned long run_time;
 	int idx;
 
 	/*
@@ -1307,7 +1328,11 @@ need_resched:
 	rq = this_rq();
 
 	release_kernel_lock(prev);
-	prev->last_run = jiffies;
+	now = jiffies;
+	run_time = now - prev->timestamp;
+
+	add_task_time(prev, run_time, STIME_RUN);
+
 	spin_lock_irq(&rq->lock);
 
 	/*
@@ -1336,7 +1361,6 @@ pick_next_task:
 			goto pick_next_task;
 #endif
 		next = rq->idle;
-		rq->expired_timestamp = 0;
 		goto switch_tasks;
 	}
 
@@ -1345,10 +1369,10 @@ pick_next_task:
 		/*
 		 * Switch the active and expired arrays.
 		 */
+		rq->array_sequence++;
 		rq->active = rq->expired;
 		rq->expired = array;
 		array = rq->active;
-		rq->expired_timestamp = 0;
 	}
 
 	idx = sched_find_first_bit(array->bitmap);
@@ -1360,7 +1384,10 @@ switch_tasks:
 	clear_tsk_need_resched(prev);
 	RCU_qsctr(task_cpu(prev))++;
 
+	prev->timestamp = now;
 	if (likely(prev != next)) {
+		add_task_time(next, now - next->timestamp, STIME_WAIT);
+		next->timestamp = now;
 		rq->nr_switches++;
 		rq->curr = next;
 
@@ -1600,6 +1627,7 @@ void set_user_nice(task_t *p, long nice)
 	unsigned long flags;
 	prio_array_t *array;
 	runqueue_t *rq;
+	int old_prio, new_prio, delta;
 
 	if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
 		return;
@@ -1608,6 +1636,12 @@ void set_user_nice(task_t *p, long nice)
 	 * the task might be in the middle of scheduling on another CPU.
 	 */
 	rq = task_rq_lock(p, &flags);
+	/*
+	 * The RT priorities are set via setscheduler(), but we still
+	 * allow the 'normal' nice value to be set - but as expected
+	 * it wont have any effect on scheduling until the task is
+	 * not SCHED_NORMAL:
+	 */
 	if (rt_task(p)) {
 		p->static_prio = NICE_TO_PRIO(nice);
 		goto out_unlock;
@@ -1615,16 +1649,20 @@ void set_user_nice(task_t *p, long nice)
 	array = p->array;
 	if (array)
 		dequeue_task(p, array);
+
+	old_prio = p->prio;
+	new_prio = NICE_TO_PRIO(nice);
+	delta = new_prio - old_prio;
 	p->static_prio = NICE_TO_PRIO(nice);
-	p->prio = NICE_TO_PRIO(nice);
+	p->prio += delta;
+
 	if (array) {
 		enqueue_task(p, array);
 		/*
-		 * If the task is running and lowered its priority,
-		 * or increased its priority then reschedule its CPU:
+		 * If the task increased its priority or is running and
+		 * lowered its priority, then reschedule its CPU:
 		 */
-		if ((NICE_TO_PRIO(nice) < p->static_prio) ||
-							task_running(rq, p))
+		if (delta < 0 || (delta > 0 && task_running(rq, p)))
 			resched_task(rq->curr);
 	}
 out_unlock:
@@ -2139,6 +2177,8 @@ asmlinkage long sys_sched_rr_get_interva
 	int retval = -EINVAL;
 	struct timespec t;
 	task_t *p;
+	unsigned long flags;
+	runqueue_t *rq;
 
 	if (pid < 0)
 		goto out_nounlock;
@@ -2153,8 +2193,10 @@ asmlinkage long sys_sched_rr_get_interva
 	if (retval)
 		goto out_unlock;
 
+	rq = task_rq_lock(p, &flags);
 	jiffies_to_timespec(p->policy & SCHED_FIFO ?
-				0 : task_timeslice(p), &t);
+				0 : task_timeslice(p, rq), &t);
+	task_rq_unlock(rq, &flags);
 	read_unlock(&tasklist_lock);
 	retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
 out_nounlock:

^ permalink raw reply	[flat|nested] 13+ messages in thread