Re: [PATCH] schedstats and staircase scheduler

[Con Kolivas <kernel@kolivas.org>]

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Rick Lindsley wrote:
> Ok Andrew, I've attached two patches (which should be applied in order to 
> apply cleanly).  They are separate because they address two different issues.  
> The first, sstat-nosmp, fixes a problem with schedstats when CONFIG_SMP is not 
> defined.
> 
> The second should restore the staircase scheduler so that we can figure out 
> why it's good and whether it can be even better.

Hi

Staircase has had it's timeslice expire in -mm for a while but here is a 
slightly newer version to play with that I diffed against your 
sstat-nosmp (that patch had some minor faults).

It would be interesting to see if setting interactive mode to 0 has any 
effect on your benchmarks and stats. This attached version may see 
slight detriment with the default of 1 (but it also might not).

echo 0 > /proc/sys/kernel/interactive

The compute mode helps some benchmarks I didn't anticipate (like reaim) 
and would also be worth examining.

echo 1 > /proc/sys/kernel/compute


Patches to get mm1 to staircase available here:

http://ck.kolivas.org/patches/2.6/2.6.8/2.6.8-rc3-mm1

Cheers,
Con

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

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Index: linux-2.6.8-rc3-mm1/fs/proc/array.c
===================================================================
--- linux-2.6.8-rc3-mm1.orig/fs/proc/array.c	2004-08-07 01:09:59.400250725 +1000
+++ linux-2.6.8-rc3-mm1/fs/proc/array.c	2004-08-07 01:10:33.958749030 +1000
@@ -155,7 +155,7 @@
 	read_lock(&tasklist_lock);
 	buffer += sprintf(buffer,
 		"State:\t%s\n"
-		"SleepAVG:\t%lu%%\n"
+		"Burst:\t%d\n"
 		"Tgid:\t%d\n"
 		"Pid:\t%d\n"
 		"PPid:\t%d\n"
@@ -163,7 +163,7 @@
 		"Uid:\t%d\t%d\t%d\t%d\n"
 		"Gid:\t%d\t%d\t%d\t%d\n",
 		get_task_state(p),
-		(p->sleep_avg/1024)*100/(1020000000/1024),
+		p->burst,
 	       	p->tgid,
 		p->pid, p->pid ? p->real_parent->pid : 0,
 		p->pid && p->ptrace ? p->parent->pid : 0,
Index: linux-2.6.8-rc3-mm1/include/linux/sched.h
===================================================================
--- linux-2.6.8-rc3-mm1.orig/include/linux/sched.h	2004-08-07 01:09:59.410249133 +1000
+++ linux-2.6.8-rc3-mm1/include/linux/sched.h	2004-08-07 01:10:33.960748712 +1000
@@ -164,6 +164,7 @@
 
 void io_schedule(void);
 long io_schedule_timeout(long timeout);
+extern int sched_interactive, sched_compute;
 
 extern void cpu_init (void);
 extern void trap_init(void);
@@ -344,7 +345,6 @@
 extern struct user_struct root_user;
 #define INIT_USER (&root_user)
 
-typedef struct prio_array prio_array_t;
 struct backing_dev_info;
 struct reclaim_state;
 
@@ -433,16 +433,13 @@
 
 	int prio, static_prio;
 	struct list_head run_list;
-	prio_array_t *array;
-
-	unsigned long sleep_avg;
-	long interactive_credit;
 	unsigned long long timestamp;
-	int activated;
+	unsigned long runtime, totalrun;
+	unsigned int burst;
 
 	unsigned long policy;
 	cpumask_t cpus_allowed;
-	unsigned int time_slice, first_time_slice;
+	unsigned int slice, time_slice;
 
 #ifdef CONFIG_SCHEDSTATS
 	struct sched_info sched_info;
@@ -615,6 +612,9 @@
 #define PF_SWAPOFF	0x00080000	/* I am in swapoff */
 #define PF_LESS_THROTTLE 0x00100000	/* Throttle me less: I clean memory */
 #define PF_SYNCWRITE	0x00200000	/* I am doing a sync write */
+#define PF_FORKED	0x00400000	/* I have just forked */
+#define PF_YIELDED	0x00800000	/* I have just yielded */
+#define PF_UISLEEP	0x01000000	/* Uninterruptible sleep */
 
 #ifdef CONFIG_SMP
 extern int set_cpus_allowed(task_t *p, cpumask_t new_mask);
@@ -698,7 +698,6 @@
  static inline void kick_process(struct task_struct *tsk) { }
 #endif
 extern void FASTCALL(sched_fork(task_t * p));
-extern void FASTCALL(sched_exit(task_t * p));
 
 extern int in_group_p(gid_t);
 extern int in_egroup_p(gid_t);
Index: linux-2.6.8-rc3-mm1/include/linux/sysctl.h
===================================================================
--- linux-2.6.8-rc3-mm1.orig/include/linux/sysctl.h	2004-08-07 01:09:57.195601728 +1000
+++ linux-2.6.8-rc3-mm1/include/linux/sysctl.h	2004-08-07 01:10:33.960748712 +1000
@@ -134,6 +134,8 @@
 	KERN_SPARC_SCONS_PWROFF=64, /* int: serial console power-off halt */
 	KERN_HZ_TIMER=65,	/* int: hz timer on or off */
 	KERN_UNKNOWN_NMI_PANIC=66, /* int: unknown nmi panic flag */
+	KERN_INTERACTIVE=67,	/* interactive tasks can have cpu bursts */
+	KERN_COMPUTE=68,	/* adjust timeslices for a compute server */
 };
 
 
Index: linux-2.6.8-rc3-mm1/init/main.c
===================================================================
--- linux-2.6.8-rc3-mm1.orig/init/main.c	2004-08-07 01:09:57.190602524 +1000
+++ linux-2.6.8-rc3-mm1/init/main.c	2004-08-07 01:10:33.961748552 +1000
@@ -683,6 +683,7 @@
 static int init(void * unused)
 {
 	lock_kernel();
+	current->prio = MAX_PRIO - 1;
 	/*
 	 * Tell the world that we're going to be the grim
 	 * reaper of innocent orphaned children.
Index: linux-2.6.8-rc3-mm1/kernel/exit.c
===================================================================
--- linux-2.6.8-rc3-mm1.orig/kernel/exit.c	2004-08-07 01:09:57.192602206 +1000
+++ linux-2.6.8-rc3-mm1/kernel/exit.c	2004-08-07 01:10:33.962748393 +1000
@@ -96,7 +96,6 @@
 	p->parent->cnvcsw += p->nvcsw + p->cnvcsw;
 	p->parent->cnivcsw += p->nivcsw + p->cnivcsw;
 	perfctr_release_task(p);
-	sched_exit(p);
 	write_unlock_irq(&tasklist_lock);
 	spin_unlock(&p->proc_lock);
 	proc_pid_flush(proc_dentry);
Index: linux-2.6.8-rc3-mm1/kernel/sched.c
===================================================================
--- linux-2.6.8-rc3-mm1.orig/kernel/sched.c	2004-08-07 01:10:00.579063047 +1000
+++ linux-2.6.8-rc3-mm1/kernel/sched.c	2004-08-07 01:10:34.180713695 +1000
@@ -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
+ *  2004-07-07	New staircase scheduling policy by Con Kolivas with help
+ *		from William Lee Irwin III, Zwane Mwaikambo & Peter Williams.
  */
 
 #include <linux/mm.h>
@@ -49,12 +51,6 @@
 
 #include <asm/unistd.h>
 
-#ifdef CONFIG_NUMA
-#define cpu_to_node_mask(cpu) node_to_cpumask(cpu_to_node(cpu))
-#else
-#define cpu_to_node_mask(cpu) (cpu_online_map)
-#endif
-
 /*
  * Convert user-nice values [ -20 ... 0 ... 19 ]
  * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
@@ -79,111 +75,15 @@
  * Some helpers for converting nanosecond timing to jiffy resolution
  */
 #define NS_TO_JIFFIES(TIME)	((TIME) / (1000000000 / HZ))
-#define JIFFIES_TO_NS(TIME)	((TIME) * (1000000000 / HZ))
-
-/*
- * 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 200 msecs.
- * Timeslices get refilled after they expire.
- */
-#define MIN_TIMESLICE		max(5 * HZ / 1000, 1)
-#define MAX_TIMESLICE		(200 * 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		(AVG_TIMESLICE * MAX_BONUS)
-#define STARVATION_LIMIT	(MAX_SLEEP_AVG)
-#define NS_MAX_SLEEP_AVG	(JIFFIES_TO_NS(MAX_SLEEP_AVG))
-#define CREDIT_LIMIT		100
-
-/*
- * 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)
-
-#ifdef CONFIG_SMP
-#define TIMESLICE_GRANULARITY(p)	(MIN_TIMESLICE * \
-		(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
-			num_online_cpus())
-#else
-#define TIMESLICE_GRANULARITY(p)	(MIN_TIMESLICE * \
-		(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), 40, MAX_BONUS) + 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 HIGH_CREDIT(p) \
-	((p)->interactive_credit > CREDIT_LIMIT)
-
-#define LOW_CREDIT(p) \
-	((p)->interactive_credit < -CREDIT_LIMIT)
-
-#define TASK_PREEMPTS_CURR(p, rq) \
-	((p)->prio < (rq)->curr->prio)
 
+int sched_compute = 0;
 /*
- * 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.
+ *This is the time all tasks within the same priority round robin.
+ *compute setting is reserved for dedicated computational scheduling
+ *and has ten times larger intervals.
  */
-
-#define BASE_TIMESLICE(p) \
-	max(MAX_TIMESLICE * (MAX_PRIO - (p)->static_prio) / (MAX_USER_PRIO), \
-		MIN_TIMESLICE)
-
-static unsigned int task_timeslice(task_t *p)
-{
-	return BASE_TIMESLICE(p);
-}
+#define _RR_INTERVAL		((10 * HZ / 1000) ? : 1)
+#define RR_INTERVAL()		(_RR_INTERVAL * (1 + 9 * sched_compute))
 
 #define task_hot(p, now, sd) ((now) - (p)->timestamp < (sd)->cache_hot_time)
 
@@ -201,16 +101,8 @@
  * These are the runqueue data structures:
  */
 
-#define BITMAP_SIZE ((((MAX_PRIO+1+7)/8)+sizeof(long)-1)/sizeof(long))
-
 typedef struct runqueue runqueue_t;
 
-struct prio_array {
-	unsigned int nr_active;
-	unsigned long bitmap[BITMAP_SIZE];
-	struct list_head queue[MAX_PRIO];
-};
-
 /*
  * This is the main, per-CPU runqueue data structure.
  *
@@ -230,12 +122,13 @@
 	unsigned long cpu_load;
 #endif
 	unsigned long long nr_switches;
-	unsigned long expired_timestamp, nr_uninterruptible;
+	unsigned long nr_uninterruptible;
 	unsigned long long timestamp_last_tick;
+	unsigned int cache_ticks, preempted;
 	task_t *curr, *idle;
 	struct mm_struct *prev_mm;
-	prio_array_t *active, *expired, arrays[2];
-	int best_expired_prio;
+	unsigned long bitmap[BITS_TO_LONGS(MAX_PRIO+1)];
+	struct list_head queue[MAX_PRIO + 1];
 	atomic_t nr_iowait;
 
 #ifdef CONFIG_SMP
@@ -693,24 +586,26 @@
 #define sched_info_switch(t, next)	do { } while (0)
 #endif /* CONFIG_SCHEDSTATS */
 
+static inline int task_queued(task_t *task)
+{
+	return !list_empty(&task->run_list);
+}
+
 /*
- * Adding/removing a task to/from a priority array:
+ * Adding/removing a task to/from a runqueue:
  */
-static void dequeue_task(struct task_struct *p, prio_array_t *array)
+static void dequeue_task(struct task_struct *p, runqueue_t *rq)
 {
-	array->nr_active--;
-	list_del(&p->run_list);
-	if (list_empty(array->queue + p->prio))
-		__clear_bit(p->prio, array->bitmap);
+	list_del_init(&p->run_list);
+	if (list_empty(rq->queue + p->prio))
+		__clear_bit(p->prio, rq->bitmap);
 }
 
-static void enqueue_task(struct task_struct *p, prio_array_t *array)
+static void enqueue_task(struct task_struct *p, runqueue_t *rq)
 {
 	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;
+	list_add_tail(&p->run_list, rq->queue + p->prio);
+	__set_bit(p->prio, rq->bitmap);
 }
 
 /*
@@ -718,43 +613,10 @@
  * remote queue so we want these tasks to show up at the head of the
  * local queue:
  */
-static inline void enqueue_task_head(struct task_struct *p, prio_array_t *array)
+static inline void enqueue_task_head(struct task_struct *p, runqueue_t *rq)
 {
-	list_add(&p->run_list, array->queue + p->prio);
-	__set_bit(p->prio, array->bitmap);
-	array->nr_active++;
-	p->array = array;
-}
-
-/*
- * 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.
- */
-static int effective_prio(task_t *p)
-{
-	int bonus, prio;
-
-	if (rt_task(p))
-		return p->prio;
-
-	bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
-
-	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;
+	list_add(&p->run_list, rq->queue + p->prio);
+	__set_bit(p->prio, rq->bitmap);
 }
 
 /*
@@ -762,7 +624,7 @@
  */
 static inline void __activate_task(task_t *p, runqueue_t *rq)
 {
-	enqueue_task(p, rq->active);
+	enqueue_task(p, rq);
 	rq->nr_running++;
 }
 
@@ -771,95 +633,132 @@
  */
 static inline void __activate_idle_task(task_t *p, runqueue_t *rq)
 {
-	enqueue_task_head(p, rq->active);
+	enqueue_task_head(p, rq);
 	rq->nr_running++;
 }
 
-static void recalc_task_prio(task_t *p, unsigned long long now)
+/*
+ * burst - extra intervals an interactive task can run for at best priority
+ * instead of descending priorities.
+ */
+static unsigned int burst(task_t *p)
 {
-	unsigned long long __sleep_time = now - p->timestamp;
-	unsigned long sleep_time;
+	if (likely(!rt_task(p))) {
+		unsigned int task_user_prio = TASK_USER_PRIO(p);
+		return 39 - task_user_prio;
+	} else
+		return p->burst;
+}
 
-	if (__sleep_time > NS_MAX_SLEEP_AVG)
-		sleep_time = NS_MAX_SLEEP_AVG;
-	else
-		sleep_time = (unsigned long)__sleep_time;
+static void inc_burst(task_t *p)
+{
+	unsigned int best_burst;
+	best_burst = burst(p);
+	if (p->burst < best_burst)
+		p->burst++;
+}
 
-	if (likely(sleep_time > 0)) {
-		/*
-		 * User tasks that sleep a long time are categorised as
-		 * idle and will get just interactive status to stay active &
-		 * prevent them suddenly becoming cpu hogs and starving
-		 * other processes.
-		 */
-		if (p->mm && p->activated != -1 &&
-			sleep_time > INTERACTIVE_SLEEP(p)) {
-				p->sleep_avg = JIFFIES_TO_NS(MAX_SLEEP_AVG -
-						AVG_TIMESLICE);
-				if (!HIGH_CREDIT(p))
-					p->interactive_credit++;
-		} else {
-			/*
-			 * The lower the sleep avg a task has the more
-			 * rapidly it will rise with sleep time.
-			 */
-			sleep_time *= (MAX_BONUS - CURRENT_BONUS(p)) ? : 1;
+static void dec_burst(task_t *p)
+{
+	if (p->burst)
+		p->burst--;
+}
 
-			/*
-			 * Tasks with low interactive_credit are limited to
-			 * one timeslice worth of sleep avg bonus.
-			 */
-			if (LOW_CREDIT(p) &&
-			    sleep_time > JIFFIES_TO_NS(task_timeslice(p)))
-				sleep_time = JIFFIES_TO_NS(task_timeslice(p));
+/*
+ * slice - the duration a task runs before getting requeued at it's best
+ * priority and has it's burst decremented.
+ */
+static unsigned int slice(task_t *p)
+{
+	unsigned int slice = RR_INTERVAL();
+	if (likely(!rt_task(p)))
+		slice += burst(p) * RR_INTERVAL();
+	return slice;
+}
 
-			/*
-			 * Non high_credit tasks waking from uninterruptible
-			 * sleep are limited in their sleep_avg rise as they
-			 * are likely to be cpu hogs waiting on I/O
-			 */
-			if (p->activated == -1 && !HIGH_CREDIT(p) && p->mm) {
-				if (p->sleep_avg >= INTERACTIVE_SLEEP(p))
-					sleep_time = 0;
-				else if (p->sleep_avg + sleep_time >=
-						INTERACTIVE_SLEEP(p)) {
-					p->sleep_avg = INTERACTIVE_SLEEP(p);
-					sleep_time = 0;
-				}
-			}
+/*
+ * sched_interactive - sysctl which allows interactive tasks to have bursts
+ */
+int sched_interactive = 1;
 
-			/*
-			 * 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;
+static int rr_interval(task_t * p)
+{
+	int rr_interval = RR_INTERVAL();
+	if (unlikely(!rr_interval))
+		rr_interval = 1;
+	return rr_interval;
+}
 
-			if (p->sleep_avg > NS_MAX_SLEEP_AVG) {
-				p->sleep_avg = NS_MAX_SLEEP_AVG;
-				if (!HIGH_CREDIT(p))
-					p->interactive_credit++;
+/*
+ * effective_prio - dynamic priority dependent on burst.
+ * The priority normally decreases by one each RR_INTERVAL.
+ * As the burst increases the priority stays at the top "stair" or
+ * priority for longer.
+ */
+static int effective_prio(task_t *p)
+{
+	int prio, rr;
+	unsigned int full_slice, used_slice, first_slice;
+	unsigned int best_burst;
+	if (rt_task(p))
+		return p->prio;
+
+	best_burst = burst(p);
+	if (p->flags & PF_UISLEEP && sched_interactive && best_burst && p->mm)
+		best_burst--;
+	full_slice = slice(p);
+	rr = rr_interval(p);
+	used_slice = full_slice - p->slice;
+	if (p->burst > best_burst)
+		p->burst = best_burst;
+	first_slice = rr;
+	if (sched_interactive && !sched_compute && p->mm)
+		first_slice *= (p->burst + 1);
+	prio = MAX_PRIO - 1 - best_burst;
+
+	if (used_slice < first_slice)
+		return prio;
+	prio += 1 + (used_slice - first_slice) / rr;
+	if (prio > MAX_PRIO - 1)
+		prio = MAX_PRIO - 1;
+	return prio;
+}
+
+/*
+ * recalc_task_prio - this checks for tasks that run ultra short timeslices
+ * or have just forked a thread/process and make them continue their old
+ * slice instead of starting a new one at high priority.
+ */
+static void recalc_task_prio(task_t *p, unsigned long long now)
+{
+	unsigned long sleep_time = now - p->timestamp;
+	unsigned long ns_totalrun = p->totalrun + p->runtime;
+	unsigned long total_run = NS_TO_JIFFIES(ns_totalrun);
+	if (p->flags & PF_FORKED || ((!(NS_TO_JIFFIES(p->runtime)) ||
+		!sched_interactive || sched_compute) &&
+		NS_TO_JIFFIES(p->runtime + sleep_time) < rr_interval(p))) {
+			p->flags &= ~PF_FORKED;
+			if (p->slice - total_run < 1) {
+				p->totalrun = 0;
+				dec_burst(p);
+			} else {
+				p->totalrun = ns_totalrun;
+				p->slice -= total_run;
 			}
-		}
+	} else {
+		if (!(p->flags & PF_UISLEEP))
+			inc_burst(p);
+		p->runtime = 0;
+		p->totalrun = 0;
 	}
-
-	p->prio = effective_prio(p);
 }
 
 /*
  * 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(task_t *p, runqueue_t *rq, int local)
 {
-	unsigned long long now;
-
-	now = sched_clock();
+	unsigned long long now = sched_clock();
 #ifdef CONFIG_SMP
 	if (!local) {
 		/* Compensate for drifting sched_clock */
@@ -868,33 +767,12 @@
 			+ rq->timestamp_last_tick;
 	}
 #endif
-
+	p->slice = slice(p);
 	recalc_task_prio(p, now);
-
-	/*
-	 * This checks to make sure it's not an uninterruptible task
-	 * that is now waking up.
-	 */
-	if (!p->activated) {
-		/*
-		 * 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->activated = 2;
-		else {
-			/*
-			 * Normal first-time wakeups get a credit too for
-			 * on-runqueue time, but it will be weighted down:
-			 */
-			p->activated = 1;
-		}
-	}
+	p->flags &= ~PF_UISLEEP;
+	p->prio = effective_prio(p);
+	p->time_slice = rr_interval(p);
 	p->timestamp = now;
-
 	__activate_task(p, rq);
 }
 
@@ -904,10 +782,11 @@
 static void deactivate_task(struct task_struct *p, runqueue_t *rq)
 {
 	rq->nr_running--;
-	if (p->state == TASK_UNINTERRUPTIBLE)
+	if (p->state == TASK_UNINTERRUPTIBLE) {
+		p->flags |= PF_UISLEEP;
 		rq->nr_uninterruptible++;
-	dequeue_task(p, p->array);
-	p->array = NULL;
+	}
+	dequeue_task(p, rq);
 }
 
 /*
@@ -980,7 +859,7 @@
 	 * 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;
 	}
@@ -1011,7 +890,7 @@
 repeat:
 	rq = task_rq_lock(p, &flags);
 	/* Must be off runqueue entirely, not preempted. */
-	if (unlikely(p->array)) {
+	if (unlikely(task_queued(p))) {
 		/* If it's preempted, we yield.  It could be a while. */
 		preempted = !task_running(rq, p);
 		task_rq_unlock(rq, &flags);
@@ -1109,6 +988,26 @@
 }
 #endif
 
+/*
+ * cache_delay is the time preemption is delayed in sched_compute mode
+ * and is set to 5*cache_decay_ticks
+ */
+static int cache_delay = 10 * HZ / 1000;
+
+static int task_preempts_curr(struct task_struct *p, runqueue_t *rq)
+{
+	if (p->prio > rq->curr->prio)
+		return 0;
+	if (p->prio == rq->curr->prio && (p->slice < slice(p) ||
+		rt_task(rq->curr)))
+			return 0;
+	if (!sched_compute || rq->cache_ticks >= cache_delay ||
+		!p->mm || rt_task(p))
+			return 1;
+	rq->preempted = 1;
+		return 0;
+}
+
 /***
  * try_to_wake_up - wake up a thread
  * @p: the to-be-woken-up thread
@@ -1141,7 +1040,7 @@
 	if (!(old_state & state))
 		goto out;
 
-	if (p->array)
+	if (task_queued(p))
 		goto out_running;
 
 	cpu = task_cpu(p);
@@ -1220,7 +1119,7 @@
 		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();
@@ -1229,14 +1128,8 @@
 
 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->activated = -1;
-	}
 
 	/*
 	 * Sync wakeups (i.e. those types of wakeups where the waker
@@ -1248,7 +1141,7 @@
 	 */
 	activate_task(p, rq, cpu == this_cpu);
 	if (!sync || cpu != this_cpu) {
-		if (TASK_PREEMPTS_CURR(p, rq))
+		if (task_preempts_curr(p, rq))
 			resched_task(rq->curr);
 	}
 	success = 1;
@@ -1293,7 +1186,6 @@
 	 */
 	p->state = TASK_RUNNING;
 	INIT_LIST_HEAD(&p->run_list);
-	p->array = NULL;
 	spin_lock_init(&p->switch_lock);
 #ifdef CONFIG_SCHEDSTATS
 	memset(&p->sched_info, 0, sizeof(p->sched_info));
@@ -1307,33 +1199,6 @@
 	 */
 	p->thread_info->preempt_count = 1;
 #endif
-	/*
-	 * 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->timestamp = sched_clock();
-	if (unlikely(!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();
 }
 
 /*
@@ -1356,39 +1221,15 @@
 	BUG_ON(p->state != TASK_RUNNING);
 
 	schedstat_inc(rq, wunt_cnt);
+
 	/*
-	 * 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.
+	 * Forked process gets no burst to prevent fork bombs.
 	 */
-	p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
-		CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-
-	p->interactive_credit = 0;
-
-	p->prio = effective_prio(p);
+	p->burst = 0;
+	current->flags |= PF_FORKED;
 
 	if (likely(cpu == this_cpu)) {
-		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;
-				list_add_tail(&p->run_list, &current->run_list);
-				p->array = current->array;
-				p->array->nr_active++;
-				rq->nr_running++;
-			}
-			set_need_resched();
-		} else
-			/* Run child last */
-			__activate_task(p, rq);
+		__activate_task(p, rq);
 	} else {
 		runqueue_t *this_rq = cpu_rq(this_cpu);
 
@@ -1399,51 +1240,12 @@
 		p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
 					+ rq->timestamp_last_tick;
 		__activate_task(p, rq);
-		if (TASK_PREEMPTS_CURR(p, rq))
+		if (task_preempts_curr(p, rq))
 			resched_task(rq->curr);
 
-		current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
-			PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-		schedstat_inc(rq, wunt_moved);
-	}
-
-	if (unlikely(cpu != this_cpu)) {
 		task_rq_unlock(rq, &flags);
 		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(rq, &flags);
-}
-
-/*
- * Potentially available exiting-child timeslices are
- * retrieved here - this way the parent does not get
- * penalized for creating too many threads.
- *
- * (this cannot be used to 'generate' timeslices
- * artificially, because any timeslice recovered here
- * was given away by the parent in the first place.)
- */
-void fastcall sched_exit(task_t * p)
-{
-	unsigned long flags;
-	runqueue_t *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) {
-		p->parent->time_slice += p->time_slice;
-		if (unlikely(p->parent->time_slice > MAX_TIMESLICE))
-			p->parent->time_slice = MAX_TIMESLICE;
-	}
-	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);
 }
 
@@ -1745,21 +1547,21 @@
  * Both runqueues must be locked.
  */
 static inline
-void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p,
-	       runqueue_t *this_rq, prio_array_t *this_array, int this_cpu)
+void pull_task(runqueue_t *src_rq, task_t *p,
+		runqueue_t *this_rq, int this_cpu)
 {
-	dequeue_task(p, src_array);
+	dequeue_task(p, src_rq);
 	src_rq->nr_running--;
 	set_task_cpu(p, this_cpu);
 	this_rq->nr_running++;
-	enqueue_task(p, this_array);
+	enqueue_task(p, this_rq);
 	p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
 				+ this_rq->timestamp_last_tick;
 	/*
 	 * 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))
+	if (task_preempts_curr(p, this_rq))
 		resched_task(this_rq->curr);
 }
 
@@ -1802,7 +1604,6 @@
 		      unsigned long max_nr_move, struct sched_domain *sd,
 		      enum idle_type idle)
 {
-	prio_array_t *array, *dst_array;
 	struct list_head *head, *curr;
 	int idx, pulled = 0;
 	task_t *tmp;
@@ -1810,38 +1611,17 @@
 	if (max_nr_move <= 0 || busiest->nr_running <= 1)
 		goto out;
 
-	/*
-	 * 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.
-	 */
-	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;
 skip_bitmap:
 	if (!idx)
-		idx = sched_find_first_bit(array->bitmap);
+		idx = sched_find_first_bit(busiest->bitmap);
 	else
-		idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
-	if (idx >= MAX_PRIO) {
-		if (array == busiest->expired && busiest->active->nr_active) {
-			array = busiest->active;
-			dst_array = this_rq->active;
-			goto new_array;
-		}
+		idx = find_next_bit(busiest->bitmap, MAX_PRIO, idx);
+	if (idx >= MAX_PRIO)
 		goto out;
-	}
 
-	head = array->queue + idx;
+	head = busiest->queue + idx;
 	curr = head->prev;
 skip_queue:
 	tmp = list_entry(curr, task_t, run_list);
@@ -1863,7 +1643,7 @@
 	schedstat_inc(this_rq, pt_gained[idle]);
 	schedstat_inc(busiest, pt_lost[idle]);
 
-	pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
+	pull_task(busiest, tmp, this_rq, this_cpu);
 	pulled++;
 
 	/* We only want to steal up to the prescribed number of tasks. */
@@ -2356,22 +2136,6 @@
 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. We also ignore the interactivity
- * if a better static_prio task has expired:
- */
-#define EXPIRED_STARVING(rq) \
-	((STARVATION_LIMIT && ((rq)->expired_timestamp && \
-		(jiffies - (rq)->expired_timestamp >= \
-			STARVATION_LIMIT * ((rq)->nr_running) + 1))) || \
-			((rq)->curr->static_prio > (rq)->best_expired_prio))
-
-/*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.
  *
@@ -2414,79 +2178,41 @@
 	else
 		cpustat->user += user_ticks;
 	cpustat->system += sys_ticks;
-
-	/* Task might have expired already, but not scheduled off yet */
-	if (p->array != rq->active) {
-		set_tsk_need_resched(p);
+	/*
+	 * SCHED_FIFO tasks never run out of timeslice.
+	 */
+	if (unlikely(p->policy == SCHED_FIFO))
 		goto out;
-	}
+
 	spin_lock(&rq->lock);
+	rq->cache_ticks++;
 	/*
-	 * 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.
+	 * Tasks lose burst each time they use up a full slice().
 	 */
-	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);
-			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->slice) {
+		set_tsk_need_resched(p);
+		dequeue_task(p, rq);
+		dec_burst(p);
+		p->slice = slice(p);
+		p->prio = effective_prio(p);
+		p->time_slice = rr_interval(p);
+		enqueue_task(p, rq);
 		goto out_unlock;
 	}
+	/*
+	 * Tasks that run out of time_slice but still have slice left get
+	 * requeued with a lower priority && rr_interval time_slice.
+	 */
 	if (!--p->time_slice) {
-		dequeue_task(p, rq->active);
 		set_tsk_need_resched(p);
+		dequeue_task(p, rq);
 		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)) {
-
-			dequeue_task(p, rq->active);
-			set_tsk_need_resched(p);
-			p->prio = effective_prio(p);
-			enqueue_task(p, rq->active);
-		}
+		p->time_slice = rr_interval(p);
+		enqueue_task(p, rq);
+		goto out_unlock;
 	}
+	if (rq->preempted && rq->cache_ticks >= cache_delay)
+		set_tsk_need_resched(p);
 out_unlock:
 	spin_unlock(&rq->lock);
 out:
@@ -2549,8 +2275,8 @@
 		 * task from using an unfair proportion of the
 		 * physical cpu's resources. -ck
 		 */
-		if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) / 100) >
-			task_timeslice(p) || rt_task(smt_curr)) &&
+		if (((smt_curr->slice * (100 - sd->per_cpu_gain) / 100) >
+			slice(p) || rt_task(smt_curr)) &&
 			p->mm && smt_curr->mm && !rt_task(p))
 				ret = 1;
 
@@ -2559,8 +2285,8 @@
 		 * or wake it up if it has been put to sleep for priority
 		 * reasons.
 		 */
-		if ((((p->time_slice * (100 - sd->per_cpu_gain) / 100) >
-			task_timeslice(smt_curr) || rt_task(p)) &&
+		if ((((p->slice * (100 - sd->per_cpu_gain) / 100) >
+			slice(smt_curr) || rt_task(p)) &&
 			smt_curr->mm && p->mm && !rt_task(smt_curr)) ||
 			(smt_curr == smt_rq->idle && smt_rq->nr_running))
 				resched_task(smt_curr);
@@ -2586,10 +2312,8 @@
 	long *switch_count;
 	task_t *prev, *next;
 	runqueue_t *rq;
-	prio_array_t *array;
 	struct list_head *queue;
 	unsigned long long now;
-	unsigned long run_time;
 	int cpu, idx;
 
 	/*
@@ -2610,30 +2334,10 @@
 	prev = current;
 	rq = this_rq();
 
-	/*
-	 * The idle thread is not allowed to schedule!
-	 * Remove this check after it has been exercised a bit.
-	 */
-	if (unlikely(current == rq->idle) && current->state != TASK_RUNNING) {
-		printk(KERN_ERR "bad: scheduling from the idle thread!\n");
-		dump_stack();
-	}
-
 	release_kernel_lock(prev);
 	schedstat_inc(rq, sched_cnt);
 	now = sched_clock();
-	if (likely(now - prev->timestamp < NS_MAX_SLEEP_AVG))
-		run_time = now - prev->timestamp;
-	else
-		run_time = NS_MAX_SLEEP_AVG;
-
-	/*
-	 * Tasks with interactive credits get charged less run_time
-	 * at high sleep_avg to delay them losing their interactive
-	 * status
-	 */
-	if (HIGH_CREDIT(prev))
-		run_time /= (CURRENT_BONUS(prev) ? : 1);
+	prev->runtime = now - prev->timestamp;
 
 	spin_lock_irq(&rq->lock);
 
@@ -2656,64 +2360,38 @@
 		idle_balance(cpu, rq);
 		if (!rq->nr_running) {
 			next = rq->idle;
-			rq->expired_timestamp = 0;
 			wake_sleeping_dependent(cpu, rq);
 			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;
-	} else
-		schedstat_inc(rq, sched_noswitch);
-
-	idx = sched_find_first_bit(array->bitmap);
-	queue = array->queue + idx;
+	idx = sched_find_first_bit(rq->bitmap);
+	queue = rq->queue + idx;
 	next = list_entry(queue->next, task_t, run_list);
 
 	if (dependent_sleeper(cpu, rq, next)) {
 		schedstat_inc(rq, sched_goidle);
 		next = rq->idle;
-		goto switch_tasks;
 	}
 
-	if (!rt_task(next) && next->activated > 0) {
-		unsigned long long delta = now - next->timestamp;
-
-		if (next->activated == 1)
-			delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
-
-		array = next->array;
-		dequeue_task(next, array);
-		recalc_task_prio(next, next->timestamp + delta);
-		enqueue_task(next, array);
-	}
-	next->activated = 0;
 switch_tasks:
 	prefetch(next);
 	clear_tsk_need_resched(prev);
 	RCU_qsctr(task_cpu(prev))++;
 
-	prev->sleep_avg -= run_time;
-	if ((long)prev->sleep_avg <= 0) {
-		prev->sleep_avg = 0;
-		if (!(HIGH_CREDIT(prev) || LOW_CREDIT(prev)))
-			prev->interactive_credit--;
-	}
 	prev->timestamp = now;
+	if (next->flags & PF_YIELDED) {
+		next->flags &= ~PF_YIELDED;
+		dequeue_task(next, rq);
+		next->prio = effective_prio(next);
+		enqueue_task_head(next, rq);
+	}
 
 	sched_info_switch(prev, next);
 	if (likely(prev != next)) {
 		next->timestamp = now;
+		rq->preempted = 0;
+		rq->cache_ticks = 0;
 		rq->nr_switches++;
 		rq->curr = next;
 		++*switch_count;
@@ -2975,9 +2653,8 @@
 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;
+	int queued, old_prio, new_prio, delta;
 
 	if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
 		return;
@@ -2996,9 +2673,8 @@
 		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);
 
 	old_prio = p->prio;
 	new_prio = NICE_TO_PRIO(nice);
@@ -3006,8 +2682,8 @@
 	p->static_prio = NICE_TO_PRIO(nice);
 	p->prio += delta;
 
-	if (array) {
-		enqueue_task(p, array);
+	if (queued) {
+		enqueue_task(p, rq);
 		/*
 		 * If the task increased its priority or is running and
 		 * lowered its priority, then reschedule its CPU:
@@ -3119,7 +2795,7 @@
 /* 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;
 	if (policy != SCHED_NORMAL)
@@ -3135,8 +2811,7 @@
 {
 	struct sched_param lp;
 	int retval = -EINVAL;
-	int oldprio;
-	prio_array_t *array;
+	int queued, oldprio;
 	unsigned long flags;
 	runqueue_t *rq;
 	task_t *p;
@@ -3196,13 +2871,12 @@
 	if (retval)
 		goto out_unlock;
 
-	array = p->array;
-	if (array)
+	if ((queued = task_queued(p)))
 		deactivate_task(p, task_rq(p));
 	retval = 0;
 	oldprio = p->prio;
 	__setscheduler(p, policy, lp.sched_priority);
-	if (array) {
+	if (queued) {
 		__activate_task(p, task_rq(p));
 		/*
 		 * Reschedule if we are currently running on this runqueue and
@@ -3212,7 +2886,7 @@
 		if (task_running(rq, p)) {
 			if (p->prio > oldprio)
 				resched_task(rq->curr);
-		} else if (TASK_PREEMPTS_CURR(p, rq))
+		} else if (task_preempts_curr(p, rq))
 			resched_task(rq->curr);
 	}
 
@@ -3419,37 +3093,22 @@
 
 /**
  * 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.
  */
 asmlinkage long sys_sched_yield(void)
 {
 	runqueue_t *rq = this_rq_lock();
-	prio_array_t *array = current->array;
-	prio_array_t *target = rq->expired;
 
 	schedstat_inc(rq, yld_cnt);
-	/*
-	 * We implement yielding by moving the task into the expired
-	 * queue.
-	 *
-	 * (special rule: RT tasks will just roundrobin in the active
-	 *  array.)
-	 */
-	if (rt_task(current))
-		target = rq->active;
-
-	if (current->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);
 
-	dequeue_task(current, array);
-	enqueue_task(current, target);
+	dequeue_task(current, rq);
+	current->slice = slice(current);
+	current->time_slice = RR_INTERVAL();
+	if (likely(!rt_task(current))) {
+		current->flags |= PF_YIELDED;
+		current->prio = MAX_PRIO - 1;
+	}
+	current->burst = 0;
+	enqueue_task(current, rq);
 
 	/*
 	 * Since we are going to call schedule() anyway, there's
@@ -3588,7 +3247,7 @@
 		goto out_unlock;
 
 	jiffies_to_timespec(p->policy & SCHED_FIFO ?
-				0 : task_timeslice(p), &t);
+				0 : slice(p), &t);
 	read_unlock(&tasklist_lock);
 	retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
 out_nounlock:
@@ -3701,11 +3360,9 @@
 	runqueue_t *rq = cpu_rq(cpu);
 	unsigned long flags;
 
-	idle->sleep_avg = 0;
-	idle->interactive_credit = 0;
-	idle->array = NULL;
 	idle->prio = MAX_PRIO;
 	idle->state = TASK_RUNNING;
+	idle->burst = 0;
 	set_task_cpu(idle, cpu);
 
 	spin_lock_irqsave(&rq->lock, flags);
@@ -3819,7 +3476,7 @@
 		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
@@ -3830,7 +3487,7 @@
 				+ rq_dest->timestamp_last_tick;
 		deactivate_task(p, rq_src);
 		activate_task(p, rq_dest, 0);
-		if (TASK_PREEMPTS_CURR(p, rq_dest))
+		if (task_preempts_curr(p, rq_dest))
 			resched_task(rq_dest->curr);
 	}
 
@@ -4487,7 +4144,7 @@
 void __init sched_init(void)
 {
 	runqueue_t *rq;
-	int i, j, k;
+	int i, j;
 
 #ifdef CONFIG_SMP
 	/* Set up an initial dummy domain for early boot */
@@ -4505,16 +4162,16 @@
 	sched_group_init.cpumask = CPU_MASK_ALL;
 	sched_group_init.next = &sched_group_init;
 	sched_group_init.cpu_power = SCHED_LOAD_SCALE;
+
+	cache_delay = cache_decay_ticks * 5;
 #endif
 
 	for (i = 0; i < NR_CPUS; i++) {
-		prio_array_t *array;
-
 		rq = cpu_rq(i);
 		spin_lock_init(&rq->lock);
-		rq->active = rq->arrays;
-		rq->expired = rq->arrays + 1;
-		rq->best_expired_prio = MAX_PRIO;
+
+		rq->cache_ticks = 0;
+		rq->preempted = 0;
 
 #ifdef CONFIG_SMP
 		rq->sd = &sched_domain_init;
@@ -4525,16 +4182,13 @@
 		INIT_LIST_HEAD(&rq->migration_queue);
 #endif
 		atomic_set(&rq->nr_iowait, 0);
-
-		for (j = 0; j < 2; j++) {
-			array = rq->arrays + j;
-			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 (j = 0; j <= MAX_PRIO; j++)
+			INIT_LIST_HEAD(&rq->queue[j]);
+		memset(rq->bitmap, 0, BITS_TO_LONGS(MAX_PRIO+1)*sizeof(long));
+		/*
+		 * delimiter for bitsearch
+		 */
+		__set_bit(MAX_PRIO, rq->bitmap);
 	}
 
 	/*
Index: linux-2.6.8-rc3-mm1/kernel/sysctl.c
===================================================================
--- linux-2.6.8-rc3-mm1.orig/kernel/sysctl.c	2004-08-07 01:09:57.193602047 +1000
+++ linux-2.6.8-rc3-mm1/kernel/sysctl.c	2004-08-07 01:10:34.011740594 +1000
@@ -641,6 +641,22 @@
 		.proc_handler   = &proc_unknown_nmi_panic,
 	},
 #endif
+	{
+		.ctl_name	= KERN_INTERACTIVE,
+		.procname	= "interactive",
+		.data		= &sched_interactive,
+		.maxlen		= sizeof (int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
+	{
+		.ctl_name	= KERN_COMPUTE,
+		.procname	= "compute",
+		.data		= &sched_compute,
+		.maxlen		= sizeof (int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 	{ .ctl_name = 0 }
 };
 
More recent patches modify files in test4-test5.

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