Re: [PATCH] Staircase Scheduler v6.3 for 2.6.7-rc2

Jan Killius
2004-06-06T17:03:09Z

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On Sunday 06 June 2004 17:39, you wrote:
> This is an update of the scheduler policy mechanism rewrite using the
> infrastructure of the current O(1) scheduler. Slight changes from the
> original design require a detailed description. The change to the original
> design has enabled all known corner cases to be abolished and cpu
> distribution to be much better maintained. It has proven to be stable in my
> testing and is ready for more widespread public testing now.
>
>
> Aims:
> - Interactive by design rather than have interactivity bolted on.
> - Good scalability.
> - Simple predictable design.
> - Maintain appropriate cpu distribution and fairness.
> - Low scheduling latency for normal policy tasks.
> - Low overhead.
> - Making renicing processes actually matter for CPU distribution (nice 0
> gets 20 times what nice +20 gets)
> - Resistant to priority inversion
> - More forgiving of poor locking
> - Tunable for a server workload or computational tasks
>
>
> Description:
> - All tasks start at a dynamic priority based on their nice value. They
> run for one RR_INTERVAL (nominally set to 10ms) and then drop one stair
> (priority). If they sleep before running again they get to run for 2
> intervals before being demoted a priority and so on until they get all
> their intervals at their best priority: 20 intervals for nice 0; 1 interval
> for nice +19.
>
>
> - The staircase elevation mechanism can be disabled and all tasks can
> simply descend stairs using the sysctl:
>
> echo 0 > /proc/sys/kernel/interactive
>
> this has the effect of maintaining cpu distribution much more strictly
> according to nice whereas the default mechanism allows bursts of cpu by
> interactive tasks before settling to appropriate cpu distribution.
>
>
> - The time tasks are cpu bound can be increased by using the sysctl:
>
> echo 1 > /proc/sys/kernel/compute
>
> which extends the RR_INTERVAL to 100ms and disables the staircase elevation
> improving conditions for pure computational tasks by optimising cache
> benefits and decreasing context switching (gains another 1.5% on
> kernbench).
>
>
> Performance:
> - All cpu throughput benchmarks show equivalent or better performance than
> mainline. Note that disabling the interactive setting actually _worsens_
> some benchmarks because of their dependence on yield() so I don't recommend
> disabling it unless you do a comparison first.
> - Interactivity is approximately equivalent to mainline 2.6 but with faster
> application startup and no known behavioural quirks.
>
>
> Comments and testing welcome.
>
> fs/proc/array.c | 2
> include/linux/sched.h | 8
> include/linux/sysctl.h | 2
> kernel/sched.c | 676
> +++++++++++++------------------------------------
> kernel/sysctl.c | 16 +
> 5 files changed, 212 insertions(+), 492 deletions(-)
>
> Can be downloaded here:
> http://ck.kolivas.org/patches/2.6/2.6.7-rc2/patch-2.6.7-rc2-s6.3
>
> and below
> Con
The same patch modified to apply clean on 2.6-7-rc2-mm2.
--
Jan

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diff -Naurp linux-2.6.7-rc2-mm2/fs/proc/array.c linux-2.6.7-rc2-mm2-s6.3/fs/proc/array.c
--- linux-2.6.7-rc2-mm2/fs/proc/array.c 2004-06-06 18:51:52.000000000 +0200
+++ linux-2.6.7-rc2-mm2-s6.3/fs/proc/array.c 2004-06-06 18:27:58.343412208 +0200
@@ -155,7 +155,6 @@ static inline char * task_state(struct t
read_lock(&tasklist_lock);
buffer += sprintf(buffer,
"State:\t%s\n"
- "SleepAVG:\t%lu%%\n"
"Tgid:\t%d\n"
"Pid:\t%d\n"
"PPid:\t%d\n"
@@ -163,7 +162,6 @@ static inline char * task_state(struct t
"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->tgid,
p->pid, p->pid ? p->real_parent->pid : 0,
p->pid && p->ptrace ? p->parent->pid : 0,
diff -Naurp linux-2.6.7-rc2-mm2/include/linux/sched.h linux-2.6.7-rc2-mm2-s6.3/include/linux/sched.h
--- linux-2.6.7-rc2-mm2/include/linux/sched.h 2004-06-06 18:51:52.000000000 +0200
+++ linux-2.6.7-rc2-mm2-s6.3/include/linux/sched.h 2004-06-06 18:27:58.343412208 +0200
@@ -172,6 +172,7 @@ extern void show_stack(struct task_struc

void io_schedule(void);
long io_schedule_timeout(long timeout);
+extern int interactive, compute;

extern void cpu_init (void);
extern void trap_init(void);
@@ -410,14 +411,13 @@ struct task_struct {
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 deadline;

unsigned long policy;
cpumask_t cpus_allowed;
- unsigned int time_slice, first_time_slice;
+ unsigned int slice, time_slice, first_time_slice;

struct list_head tasks;
struct list_head ptrace_children;
diff -Naurp linux-2.6.7-rc2-mm2/include/linux/sysctl.h linux-2.6.7-rc2-mm2-s6.3/include/linux/sysctl.h
--- linux-2.6.7-rc2-mm2/include/linux/sysctl.h 2004-06-06 18:51:52.000000000 +0200
+++ linux-2.6.7-rc2-mm2-s6.3/include/linux/sysctl.h 2004-06-06 18:27:58.345411904 +0200
@@ -133,6 +133,8 @@ enum
KERN_NGROUPS_MAX=63, /* int: NGROUPS_MAX */
KERN_SPARC_SCONS_PWROFF=64, /* int: serial console power-off halt */
KERN_HZ_TIMER=65, /* int: hz timer on or off */
+ KERN_INTERACTIVE=66, /* interactive tasks to have cpu bursts */
+ KERN_COMPUTE=67, /* adjust timeslices for a compute server */
};

diff -Naurp linux-2.6.7-rc2-mm2/kernel/sched.c linux-2.6.7-rc2-mm2-s6.3/kernel/sched.c
--- linux-2.6.7-rc2-mm2/kernel/sched.c 2004-06-06 18:51:52.000000000 +0200
+++ linux-2.6.7-rc2-mm2-s6.3/kernel/sched.c 2004-06-06 18:33:49.541022056 +0200
@@ -16,7 +16,10 @@
* 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
- */
+ * 2004-03-19. New staircase scheduling policy by Con Kolivas with help
+ * from Zwane Mwaikambo and useful suggestions by
+ * William Lee Irwin III.
+*/

#include <linux/mm.h>
#include <linux/module.h>
@@ -70,8 +73,6 @@
#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 AVG_TIMESLICE (MIN_TIMESLICE + ((MAX_TIMESLICE - MIN_TIMESLICE) *\
- (MAX_PRIO-1-NICE_TO_PRIO(0))/(MAX_USER_PRIO - 1)))

/*
* Some helpers for converting nanosecond timing to jiffy resolution
@@ -79,110 +80,18 @@
#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 10 msecs, default timeslice is 100 msecs,
- * maximum timeslice is 200 msecs. Timeslices get refilled after
- * they expire.
- */
-#define MIN_TIMESLICE ( 10 * HZ / 1000)
-#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)
+int compute = 0;
+/*
+ *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 _RR_INTERVAL ((10 * HZ / 1000) ? : 1)
+#define RR_INTERVAL (_RR_INTERVAL * (1 + 9 * compute))

#define TASK_PREEMPTS_CURR(p, rq) \
((p)->prio < (rq)->curr->prio)

-/*
- * 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)))
-
-static unsigned int task_timeslice(task_t *p)
-{
- return BASE_TIMESLICE(p);
-}
-
#define task_hot(p, now, sd) ((now) - (p)->timestamp < (sd)->cache_hot_time)

/*
@@ -196,7 +105,7 @@ typedef struct runqueue runqueue_t;
struct prio_array {
unsigned int nr_active;
unsigned long bitmap[BITMAP_SIZE];
- struct list_head queue[MAX_PRIO];
+ struct list_head queue[MAX_PRIO + 1];
};

/*
@@ -218,13 +127,12 @@ struct runqueue {
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;
task_t *curr, *idle;

struct mm_struct *prev_mm;
- prio_array_t *active, *expired, arrays[2];
- int best_expired_prio;
+ prio_array_t array;
atomic_t nr_iowait;

#ifdef CONFIG_SMP
@@ -406,16 +314,18 @@ static inline void rq_unlock(runqueue_t
/*
* Adding/removing a task to/from a priority array:
*/
-static void dequeue_task(struct task_struct *p, prio_array_t *array)
+static void dequeue_task(struct task_struct *p, runqueue_t *rq)
{
+ prio_array_t* array = &rq->array;
array->nr_active--;
list_del(&p->run_list);
if (list_empty(array->queue + p->prio))
__clear_bit(p->prio, array->bitmap);
}

-static void enqueue_task(struct task_struct *p, prio_array_t *array)
+static void enqueue_task(struct task_struct *p, runqueue_t *rq)
{
+ prio_array_t* array = &rq->array;
list_add_tail(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
@@ -427,8 +337,9 @@ static void enqueue_task(struct task_str
* 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)
{
+ prio_array_t* array = &rq->array;
list_add(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
@@ -436,42 +347,11 @@ static inline void enqueue_task_head(str
}

/*
- * 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;
-}
-
-/*
* __activate_task - move a task to the runqueue.
*/
static inline void __activate_task(task_t *p, runqueue_t *rq)
{
- enqueue_task(p, rq->active);
+ enqueue_task(p, rq);
rq->nr_running++;
}

@@ -480,95 +360,112 @@ static inline void __activate_task(task_
*/
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)
+// deadline - the best deadline rank a task can have.
+static unsigned int deadline(task_t *p)
{
- unsigned long long __sleep_time = now - p->timestamp;
- unsigned long sleep_time;
-
- if (__sleep_time > NS_MAX_SLEEP_AVG)
- sleep_time = NS_MAX_SLEEP_AVG;
+ unsigned int task_user_prio;
+ if (rt_task(p))
+ return p->deadline;
+ task_user_prio = TASK_USER_PRIO(p);
+ if (likely(task_user_prio < 40))
+ return 39 - task_user_prio;
else
- sleep_time = (unsigned long)__sleep_time;
+ return 0;
+}

- 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 inc_deadline(task_t *p)
+{
+ unsigned int best_deadline;
+ best_deadline = deadline(p);
+ if (!p->mm || rt_task(p) || !best_deadline)
+ return;
+ if (p->deadline < best_deadline)
+ p->deadline++;
+}

- /*
- * 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));
+static void dec_deadline(task_t *p)
+{
+ if (!p->mm || rt_task(p))
+ return;
+ if (p->deadline)
+ p->deadline--;
+}

- /*
- * 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;
- }
- }
+// slice - the duration a task runs before losing a deadline rank.
+static unsigned int slice(task_t *p)
+{
+ unsigned int slice = RR_INTERVAL;
+ if (!rt_task(p))
+ slice += deadline(p) * RR_INTERVAL;
+ return slice;
+}

- /*
- * 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;
+// interactive - interactive tasks get longer intervals at best priority
+int interactive = 1;

- 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 deadline rank.
+ * With 0 deadline ranks the priority decreases by one each RR_INTERVAL.
+ * As the deadline rank increases the priority stays at the top "stair" or
+ * value for longer.
+ */
+static int effective_prio(task_t *p)
+{
+ int prio;
+ unsigned int full_slice, used_slice, first_slice;
+ unsigned int best_deadline;
+ if (rt_task(p))
+ return p->prio;
+
+ best_deadline = deadline(p);
+ full_slice = slice(p);
+ used_slice = full_slice - p->slice;
+ if (p->deadline > best_deadline || !p->mm)
+ p->deadline = best_deadline;
+ first_slice = RR_INTERVAL;
+ if (interactive && !compute)
+ first_slice *= (p->deadline + 1);
+ prio = MAX_PRIO - 1 - best_deadline;
+
+ if (used_slice < first_slice)
+ return prio;
+ if (p->mm)
+ prio += 1 + (used_slice - first_slice) / RR_INTERVAL;
+ if (prio > MAX_PRIO - 1)
+ prio = MAX_PRIO - 1;
+ return prio;
+}
+
+static void recalc_task_prio(task_t *p, unsigned long long now)
+{
+ unsigned long sleep_time = now - p->timestamp;
+ unsigned long run_time = NS_TO_JIFFIES(p->runtime);
+ unsigned long total_run = NS_TO_JIFFIES(p->totalrun) + run_time;
+ if (!run_time && NS_TO_JIFFIES(p->runtime + sleep_time) < RR_INTERVAL) {
+ if (p->slice - total_run < 1) {
+ p->totalrun = 0;
+ dec_deadline(p);
+ } else {
+ p->totalrun += p->runtime;
+ p->slice -= NS_TO_JIFFIES(p->totalrun);
}
+ } else {
+ inc_deadline(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 */
@@ -577,33 +474,14 @@ static void activate_task(task_t *p, run
+ rq->timestamp_last_tick;
}
#endif
-
- 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->slice = slice(p);
+ if (!rt_task(p) && p->mm)
+ recalc_task_prio(p, now);
+ else
+ inc_deadline(p);
+ p->prio = effective_prio(p);
+ p->time_slice = RR_INTERVAL;
p->timestamp = now;
-
__activate_task(p, rq);
}

@@ -613,9 +491,12 @@ static void activate_task(task_t *p, run
static void deactivate_task(struct task_struct *p, runqueue_t *rq)
{
rq->nr_running--;
- if (p->state == TASK_UNINTERRUPTIBLE)
+ if (p->state == TASK_UNINTERRUPTIBLE) {
rq->nr_uninterruptible++;
- dequeue_task(p, p->array);
+ if (p->deadline > (deadline(p) - 2) && p->deadline && p->mm)
+ p->deadline--;
+ }
+ dequeue_task(p, rq);
p->array = NULL;
}

@@ -946,14 +827,8 @@ 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->activated = -1;
- }

/*
* Sync wakeups (i.e. those types of wakeups where the waker
@@ -1023,12 +898,14 @@ void fastcall sched_fork(task_t *p)
*/
local_irq_disable();
p->time_slice = (current->time_slice + 1) >> 1;
+ p->slice = (current->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;
+ current->slice >>= 1;
p->timestamp = sched_clock();
if (!current->time_slice) {
/*
@@ -1056,33 +933,14 @@ void fastcall wake_up_forked_process(tas
unsigned long flags;
runqueue_t *rq = task_rq_lock(current, &flags);

+ // Forked process gets a lower deadline rank to prevent fork bombs.
+ p->deadline = 0;
BUG_ON(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 = JIFFIES_TO_NS(CURRENT_BONUS(current) *
- PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-
- 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);
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++;
- rq->nr_running++;
- }
+ p->prio = effective_prio(p);
+ __activate_task(p, rq);
task_rq_unlock(rq, &flags);
}

@@ -1103,19 +961,11 @@ void fastcall 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;
+ if (unlikely(p->parent->time_slice > slice(p->parent)))
+ p->parent->time_slice = slice(p->parent);
}
local_irq_restore(flags);
- /*
- * 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->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);
}

@@ -1379,18 +1229,6 @@ lock_again:
double_rq_unlock(this_rq, rq);
goto lock_again;
}
- /*
- * 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 = JIFFIES_TO_NS(CURRENT_BONUS(current) *
- PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
-
- 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);
set_task_cpu(p, cpu);
@@ -1505,15 +1343,15 @@ static void double_lock_balance(runqueue
* pull_task - move a task from a remote runqueue to the local runqueue.
* 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)
+static inline
+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;
/*
@@ -1570,29 +1408,16 @@ static int move_tasks(runqueue_t *this_r
unsigned long max_nr_move, struct sched_domain *sd,
enum idle_type idle)
{
- prio_array_t *array, *dst_array;
+ prio_array_t* array, *dst_array;
struct list_head *head, *curr;
int idx, pulled = 0;
task_t *tmp;

if (max_nr_move <= 0 || busiest->nr_running <= 1)
goto out;
+ array = &busiest->array;
+ dst_array = &this_rq->array;

- /*
- * 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:
@@ -1600,14 +1425,8 @@ skip_bitmap:
idx = sched_find_first_bit(array->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;
- }
+ if (idx >= MAX_PRIO)
goto out;
- }

head = array->queue + idx;
curr = head->prev;
@@ -1622,7 +1441,7 @@ skip_queue:
idx++;
goto skip_bitmap;
}
- 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. */
@@ -2114,22 +1933,6 @@ 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. 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.
*
@@ -2174,76 +1977,38 @@ void scheduler_tick(int user_ticks, int
cpustat->system += sys_ticks;

/* Task might have expired already, but not scheduled off yet */
- if (p->array != rq->active) {
+ if (p->array != &rq->array) {
set_tsk_need_resched(p);
goto out;
}
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.
- */
- 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);
- }
+
+ // SCHED_FIFO tasks never run out of timeslice.
+ if (unlikely(p->policy == SCHED_FIFO))
+ goto out_unlock;
+ // Tasks lose a deadline rank each time they use up a full slice().
+ if (!--p->slice) {
+ set_tsk_need_resched(p);
+ dequeue_task(p, rq);
+ dec_deadline(p);
+ p->slice = slice(p);
+ p->prio = effective_prio(p);
+ p->time_slice = RR_INTERVAL;
+ enqueue_task(p, rq);
+ p->first_time_slice = 0;
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;
+ enqueue_task(p, rq);
+ goto out_unlock;
}
out_unlock:
spin_unlock(&rq->lock);
@@ -2307,8 +2072,8 @@ static inline int dependent_sleeper(int
* 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;

@@ -2317,8 +2082,8 @@ static inline int dependent_sleeper(int
* 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);
@@ -2344,10 +2109,9 @@ asmlinkage void __sched schedule(void)
long *switch_count;
task_t *prev, *next;
runqueue_t *rq;
- prio_array_t *array;
+ prio_array_t* array;
struct list_head *queue;
unsigned long long now;
- unsigned long run_time;
int cpu, idx;

/*
@@ -2370,19 +2134,8 @@ need_resched:
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);

/*
@@ -2404,58 +2157,24 @@ need_resched:
idle_balance(cpu, rq);
if (!rq->nr_running) {
next = rq->idle;
- rq->expired_timestamp = 0;
wake_sleeping_dependent(cpu, rq);
schedstat_inc(rq, sched_idle);
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;
- }
-
+ array = &rq->array;
idx = sched_find_first_bit(array->bitmap);
queue = array->queue + idx;
next = list_entry(queue->next, task_t, run_list);
-
- if (dependent_sleeper(cpu, rq, next)) {
+ if (dependent_sleeper(cpu, rq, next))
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 (likely(prev != next)) {
@@ -2721,7 +2440,7 @@ EXPORT_SYMBOL(sleep_on_timeout);
void set_user_nice(task_t *p, long nice)
{
unsigned long flags;
- prio_array_t *array;
+ prio_array_t* array;
runqueue_t *rq;
int old_prio, new_prio, delta;

@@ -2744,7 +2463,7 @@ void set_user_nice(task_t *p, long nice)
}
array = p->array;
if (array)
- dequeue_task(p, array);
+ dequeue_task(p, rq);

old_prio = p->prio;
new_prio = NICE_TO_PRIO(nice);
@@ -2753,7 +2472,7 @@ void set_user_nice(task_t *p, long nice)
p->prio += delta;

if (array) {
- enqueue_task(p, array);
+ enqueue_task(p, rq);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
@@ -2882,7 +2601,7 @@ static int setscheduler(pid_t pid, int p
struct sched_param lp;
int retval = -EINVAL;
int oldprio;
- prio_array_t *array;
+ prio_array_t* array;
unsigned long flags;
runqueue_t *rq;
task_t *p;
@@ -3151,29 +2870,17 @@ out_unlock:
/**
* 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 (unlikely(rt_task(current)))
- target = rq->active;
-
- dequeue_task(current, array);
- enqueue_task(current, target);
+ dequeue_task(current, rq);
+ current->slice = slice(current);
+ current->time_slice = current->slice;
+ current->prio = effective_prio(current);
+ enqueue_task(current, rq);

/*
* Since we are going to call schedule() anyway, there's
@@ -3312,7 +3019,7 @@ long sys_sched_rr_get_interval(pid_t pid
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:
@@ -3433,6 +3140,7 @@ void __devinit init_idle(task_t *idle, i
idle->array = NULL;
idle->prio = MAX_PRIO;
idle->state = TASK_RUNNING;
+ idle->deadline = 0;
set_task_cpu(idle, cpu);
double_rq_unlock(idle_rq, rq);
set_tsk_need_resched(idle);
@@ -4068,7 +3776,7 @@ int in_sched_functions(unsigned long add
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 */
@@ -4089,13 +3797,10 @@ void __init sched_init(void)
#endif

for (i = 0; i < NR_CPUS; i++) {
- prio_array_t *array;
+ 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;

#ifdef CONFIG_SMP
rq->sd = &sched_domain_init;
@@ -4106,16 +3811,14 @@ void __init sched_init(void)
INIT_LIST_HEAD(&rq->migration_queue);
#endif
atomic_set(&rq->nr_iowait, 0);
+ array = &rq->array;

- 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(array->queue + j);
+ __clear_bit(j, array->bitmap);
}
+ // delimiter for bitsearch
+ __set_bit(MAX_PRIO, array->bitmap);
}
/*
* We have to do a little magic to get the first
diff -Naurp linux-2.6.7-rc2-mm2/kernel/sysctl.c linux-2.6.7-rc2-mm2-s6.3/kernel/sysctl.c
--- linux-2.6.7-rc2-mm2/kernel/sysctl.c 2004-06-06 18:51:52.000000000 +0200
+++ linux-2.6.7-rc2-mm2-s6.3/kernel/sysctl.c 2004-06-06 18:27:58.359409776 +0200
@@ -618,6 +618,22 @@ static ctl_table kern_table[] = {
.mode = 0444,
.proc_handler = &proc_dointvec,
},
+ {
+ .ctl_name = KERN_INTERACTIVE,
+ .procname = "interactive",
+ .data = &interactive,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+ {
+ .ctl_name = KERN_COMPUTE,
+ .procname = "compute",
+ .data = &compute,
+ .maxlen = sizeof (int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
{ .ctl_name = 0 }
};