/* * kernel/sched.c * * Kernel scheduler and related syscalls * * Copyright (C) 1991-2002 Linus Torvalds * * 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and * make semaphores SMP safe * 1998-11-19 Implemented schedule_timeout() and related stuff * by Andrea Arcangeli * 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar: * hybrid priority-list and round-robin design with * an array-switch method of distributing timeslices * and per-CPU runqueues. Cleanups and useful suggestions * 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 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Convert user-nice values [ -20 ... 0 ... 19 ] * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ], * and back. */ #define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20) #define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20) #define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio) /* * 'User priority' is the nice value converted to something we * can work with better when scaling various scheduler parameters, * it's a [ 0 ... 39 ] range. */ #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)) /* * 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 800 msecs. * Timeslices get refilled after they expire. */ #define MIN_TIMESLICE max(5 * HZ / 1000, 1) #define DEF_TIMESLICE (100 * HZ / 1000) #define ON_RUNQUEUE_WEIGHT 30 #define CHILD_PENALTY 95 #define PARENT_PENALTY 100 #define EXIT_WEIGHT 3 #define PRIO_BONUS_RATIO 25 #define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100) #define INTERACTIVE_DELTA 2 #define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS) #define STARVATION_LIMIT (MAX_SLEEP_AVG) #define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG)) /* * If a task is 'interactive' then we reinsert it in the active * array after it has expired its current timeslice. (it will not * continue to run immediately, it will still roundrobin with * other interactive tasks.) * * This part scales the interactivity limit depending on niceness. * * We scale it linearly, offset by the INTERACTIVE_DELTA delta. * Here are a few examples of different nice levels: * * TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0] * TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0] * TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0] * TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0] * * (the X axis represents the possible -5 ... 0 ... +5 dynamic * priority range a task can explore, a value of '1' means the * task is rated interactive.) * * Ie. nice +19 tasks can never get 'interactive' enough to be * reinserted into the active array. And only heavily CPU-hog nice -20 * tasks will be expired. Default nice 0 tasks are somewhere between, * it takes some effort for them to get interactive, but it's not * too hard. */ #define CURRENT_BONUS(p) \ (NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \ MAX_SLEEP_AVG) #define GRANULARITY (10 * HZ / 1000 ? : 1) #ifdef CONFIG_SMP #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \ (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \ num_online_cpus()) #else #define TIMESLICE_GRANULARITY(p) (GRANULARITY * \ (1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1))) #endif #define SCALE(v1,v1_max,v2_max) \ (v1) * (v2_max) / (v1_max) #define DELTA(p) \ (SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \ INTERACTIVE_DELTA) #define TASK_INTERACTIVE(p) \ ((p)->prio <= (p)->static_prio - DELTA(p)) #define INTERACTIVE_SLEEP(p) \ (JIFFIES_TO_NS(MAX_SLEEP_AVG * \ (MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1)) #define TASK_PREEMPTS_CURR(p, rq) \ ((p)->prio < (rq)->curr->prio) /* * task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ] * to time slice values: [800ms ... 100ms ... 5ms] * * The higher a thread's priority, the bigger timeslices * it gets during one round of execution. But even the lowest * priority thread gets MIN_TIMESLICE worth of execution time. */ #define SCALE_PRIO(x, prio) \ max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE) static unsigned int static_prio_timeslice(int static_prio) { if (static_prio < NICE_TO_PRIO(0)) return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio); else return SCALE_PRIO(DEF_TIMESLICE, static_prio); } static inline unsigned int task_timeslice(struct task_struct *p) { return static_prio_timeslice(p->static_prio); } /* * These are the runqueue data structures: */ struct prio_array { unsigned int nr_active; DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */ struct list_head queue[MAX_PRIO]; }; /* * This is the main, per-CPU runqueue data structure. * * Locking rule: those places that want to lock multiple runqueues * (such as the load balancing or the thread migration code), lock * acquire operations must be ordered by ascending &runqueue. */ struct rq { spinlock_t lock; /* * nr_running and cpu_load should be in the same cacheline because * remote CPUs use both these fields when doing load calculation. */ unsigned long nr_running; unsigned long raw_weighted_load; #ifdef CONFIG_SMP unsigned long cpu_load[3]; #endif unsigned long long nr_switches; /* * This is part of a global counter where only the total sum * over all CPUs matters. A task can increase this counter on * one CPU and if it got migrated afterwards it may decrease * it on another CPU. Always updated under the runqueue lock: */ unsigned long nr_uninterruptible; unsigned long expired_timestamp; unsigned long long timestamp_last_tick; struct task_struct *curr, *idle; struct mm_struct *prev_mm; struct prio_array *active, *expired, arrays[2]; int best_expired_prio; atomic_t nr_iowait; #ifdef CONFIG_SMP struct sched_domain *sd; /* For active balancing */ int active_balance; int push_cpu; struct task_struct *migration_thread; struct list_head migration_queue; #endif #ifdef CONFIG_SCHEDSTATS /* latency stats */ struct sched_info rq_sched_info; /* sys_sched_yield() stats */ unsigned long yld_exp_empty; unsigned long yld_act_empty; unsigned long yld_both_empty; unsigned long yld_cnt; /* schedule() stats */ unsigned long sched_switch; unsigned long sched_cnt; unsigned long sched_goidle; /* try_to_wake_up() stats */ unsigned long ttwu_cnt; unsigned long ttwu_local; #endif struct lock_class_key rq_lock_key; }; static DEFINE_PER_CPU(struct rq, runqueues); /* * The domain tree (rq->sd) is protected by RCU's quiescent state transition. * See detach_destroy_domains: synchronize_sched for details. * * The domain tree of any CPU may only be accessed from within * preempt-disabled sections. */ #define for_each_domain(cpu, __sd) \ for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent) #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu))) #define this_rq() (&__get_cpu_var(runqueues)) #define task_rq(p) cpu_rq(task_cpu(p)) #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #ifndef prepare_arch_switch # define prepare_arch_switch(next) do { } while (0) #endif #ifndef finish_arch_switch # define finish_arch_switch(prev) do { } while (0) #endif #ifndef __ARCH_WANT_UNLOCKED_CTXSW static inline int task_running(struct rq *rq, struct task_struct *p) { return rq->curr == p; } static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next) { } static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev) { #ifdef CONFIG_DEBUG_SPINLOCK /* this is a valid case when another task releases the spinlock */ rq->lock.owner = current; #endif /* * If we are tracking spinlock dependencies then we have to * fix up the runqueue lock - which gets 'carried over' from * prev into current: */ spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_); spin_unlock_irq(&rq->lock); } #else /* __ARCH_WANT_UNLOCKED_CTXSW */ static inline int task_running(struct rq *rq, struct task_struct *p) { #ifdef CONFIG_SMP return p->oncpu; #else return rq->curr == p; #endif } static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next) { #ifdef CONFIG_SMP /* * We can optimise this out completely for !SMP, because the * SMP rebalancing from interrupt is the only thing that cares * here. */ next->oncpu = 1; #endif #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW spin_unlock_irq(&rq->lock); #else spin_unlock(&rq->lock); #endif } static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev) { #ifdef CONFIG_SMP /* * After ->oncpu is cleared, the task can be moved to a different CPU. * We must ensure this doesn't happen until the switch is completely * finished. */ smp_wmb(); prev->oncpu = 0; #endif #ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW local_irq_enable(); #endif } #endif /* __ARCH_WANT_UNLOCKED_CTXSW */ /* * __task_rq_lock - lock the runqueue a given task resides on. * Must be called interrupts disabled. */ static inline struct rq *__task_rq_lock(struct task_struct *p) __acquires(rq->lock) { struct rq *rq; repeat_lock_task: rq = task_rq(p); spin_lock(&rq->lock); if (unlikely(rq != task_rq(p))) { spin_unlock(&rq->lock); goto repeat_lock_task; } return rq; } /* * task_rq_lock - lock the runqueue a given task resides on and disable * interrupts. Note the ordering: we can safely lookup the task_rq without * explicitly disabling preemption. */ static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags) __acquires(rq->lock) { struct rq *rq; repeat_lock_task: local_irq_save(*flags); rq = task_rq(p); spin_lock(&rq->lock); if (unlikely(rq != task_rq(p))) { spin_unlock_irqrestore(&rq->lock, *flags); goto repeat_lock_task; } return rq; } static inline void __task_rq_unlock(struct rq *rq) __releases(rq->lock) { spin_unlock(&rq->lock); } static inline void task_rq_unlock(struct rq *rq, unsigned long *flags) __releases(rq->lock) { spin_unlock_irqrestore(&rq->lock, *flags); } #ifdef CONFIG_SCHEDSTATS /* * bump this up when changing the output format or the meaning of an existing * format, so that tools can adapt (or abort) */ #define SCHEDSTAT_VERSION 12 static int show_schedstat(struct seq_file *seq, void *v) { int cpu; seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION); seq_printf(seq, "timestamp %lu\n", jiffies); for_each_online_cpu(cpu) { struct rq *rq = cpu_rq(cpu); #ifdef CONFIG_SMP struct sched_domain *sd; int dcnt = 0; #endif /* runqueue-specific stats */ seq_printf(seq, "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu", cpu, rq->yld_both_empty, rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt, rq->sched_switch, rq->sched_cnt, rq->sched_goidle, rq->ttwu_cnt, rq->ttwu_local, rq->rq_sched_info.cpu_time, rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt); seq_printf(seq, "\n"); #ifdef CONFIG_SMP /* domain-specific stats */ preempt_disable(); for_each_domain(cpu, sd) { enum idle_type itype; char mask_str[NR_CPUS]; cpumask_scnprintf(mask_str, NR_CPUS, sd->span); seq_printf(seq, "domain%d %s", dcnt++, mask_str); for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES; itype++) { seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu", sd->lb_cnt[itype], sd->lb_balanced[itype], sd->lb_failed[itype], sd->lb_imbalance[itype], sd->lb_gained[itype], sd->lb_hot_gained[itype], sd->lb_nobusyq[itype], sd->lb_nobusyg[itype]); } seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n", sd->alb_cnt, sd->alb_failed, sd->alb_pushed, sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed, sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed, sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance); } preempt_enable(); #endif } return 0; } static int schedstat_open(struct inode *inode, struct file *file) { unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32); char *buf = kmalloc(size, GFP_KERNEL); struct seq_file *m; int res; if (!buf) return -ENOMEM; res = single_open(file, show_schedstat, NULL); if (!res) { m = file->private_data; m->buf = buf; m->size = size; } else kfree(buf); return res; } struct file_operations proc_schedstat_operations = { .open = schedstat_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; /* * Expects runqueue lock to be held for atomicity of update */ static inline void rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies) { if (rq) { rq->rq_sched_info.run_delay += delta_jiffies; rq->rq_sched_info.pcnt++; } } /* * Expects runqueue lock to be held for atomicity of update */ static inline void rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies) { if (rq) rq->rq_sched_info.cpu_time += delta_jiffies; } # define schedstat_inc(rq, field) do { (rq)->field++; } while (0) # define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0) #else /* !CONFIG_SCHEDSTATS */ static inline void rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies) {} static inline void rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies) {} # define schedstat_inc(rq, field) do { } while (0) # define schedstat_add(rq, field, amt) do { } while (0) #endif /* * rq_lock - lock a given runqueue and disable interrupts. */ static inline struct rq *this_rq_lock(void) __acquires(rq->lock) { struct rq *rq; local_irq_disable(); rq = this_rq(); spin_lock(&rq->lock); return rq; } #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) /* * Called when a process is dequeued from the active array and given * the cpu. We should note that with the exception of interactive * tasks, the expired queue will become the active queue after the active * queue is empty, without explicitly dequeuing and requeuing tasks in the * expired queue. (Interactive tasks may be requeued directly to the * active queue, thus delaying tasks in the expired queue from running; * see scheduler_tick()). * * This function is only called from sched_info_arrive(), rather than * dequeue_task(). Even though a task may be queued and dequeued multiple * times as it is shuffled about, we're really interested in knowing how * long it was from the *first* time it was queued to the time that it * finally hit a cpu. */ static inline void sched_info_dequeued(struct task_struct *t) { t->sched_info.last_queued = 0; } /* * Called when a task finally hits the cpu. We can now calculate how * long it was waiting to run. We also note when it began so that we * can keep stats on how long its timeslice is. */ static void sched_info_arrive(struct task_struct *t) { unsigned long now = jiffies, delta_jiffies = 0; if (t->sched_info.last_queued) delta_jiffies = now - t->sched_info.last_queued; sched_info_dequeued(t); t->sched_info.run_delay += delta_jiffies; t->sched_info.last_arrival = now; t->sched_info.pcnt++; rq_sched_info_arrive(task_rq(t), delta_jiffies); } /* * Called when a process is queued into either the active or expired * array. The time is noted and later used to determine how long we * had to wait for us to reach the cpu. Since the expired queue will * become the active queue after active queue is empty, without dequeuing * and requeuing any tasks, we are interested in queuing to either. It * is unusual but not impossible for tasks to be dequeued and immediately * requeued in the same or another array: this can happen in sched_yield(), * set_user_nice(), and even load_balance() as it moves tasks from runqueue * to runqueue. * * This function is only called from enqueue_task(), but also only updates * the timestamp if it is already not set. It's assumed that * sched_info_dequeued() will clear that stamp when appropriate. */ static inline void sched_info_queued(struct task_struct *t) { if (unlikely(sched_info_on())) if (!t->sched_info.last_queued) t->sched_info.last_queued = jiffies; } /* * Called when a process ceases being the active-running process, either * voluntarily or involuntarily. Now we can calculate how long we ran. */ static inline void sched_info_depart(struct task_struct *t) { unsigned long delta_jiffies = jiffies - t->sched_info.last_arrival; t->sched_info.cpu_time += delta_jiffies; rq_sched_info_depart(task_rq(t), delta_jiffies); } /* * Called when tasks are switched involuntarily due, typically, to expiring * their time slice. (This may also be called when switching to or from * the idle task.) We are only called when prev != next. */ static inline void __sched_info_switch(struct task_struct *prev, struct task_struct *next) { struct rq *rq = task_rq(prev); /* * prev now departs the cpu. It's not interesting to record * stats about how efficient we were at scheduling the idle * process, however. */ if (prev != rq->idle) sched_info_depart(prev); if (next != rq->idle) sched_info_arrive(next); } static inline void sched_info_switch(struct task_struct *prev, struct task_struct *next) { if (unlikely(sched_info_on())) __sched_info_switch(prev, next); } #else #define sched_info_queued(t) do { } while (0) #define sched_info_switch(t, next) do { } while (0) #endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */ /* * Adding/removing a task to/from a priority array: */ static void dequeue_task(struct task_struct *p, struct prio_array *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, struct prio_array *array) { 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; } /* * Put task to the end of the run list without the overhead of dequeue * followed by enqueue. */ static void requeue_task(struct task_struct *p, struct prio_array *array) { list_move_tail(&p->run_list, array->queue + p->prio); } static inline void enqueue_task_head(struct task_struct *p, struct prio_array *array) { list_add(&p->run_list, array->queue + p->prio); __set_bit(p->prio, array->bitmap); array->nr_active++; p->array = array; } /* * __normal_prio - return the priority that is based on the static * priority but is modified by bonuses/penalties. * * We scale the actual sleep average [0 .... MAX_SLEEP_AVG] * into the -5 ... 0 ... +5 bonus/penalty range. * * We use 25% of the full 0...39 priority range so that: * * 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs. * 2) nice -20 CPU hogs do not get preempted by nice 0 tasks. * * Both properties are important to certain workloads. */ static inline int __normal_prio(struct task_struct *p) { int bonus, 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; } /* * To aid in avoiding the subversion of "niceness" due to uneven distribution * of tasks with abnormal "nice" values across CPUs the contribution that * each task makes to its run queue's load is weighted according to its * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a * scaled version of the new time slice allocation that they receive on time * slice expiry etc. */ /* * Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE * If static_prio_timeslice() is ever changed to break this assumption then * this code will need modification */ #define TIME_SLICE_NICE_ZERO DEF_TIMESLICE #define LOAD_WEIGHT(lp) \ (((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO) #define PRIO_TO_LOAD_WEIGHT(prio) \ LOAD_WEIGHT(static_prio_timeslice(prio)) #define RTPRIO_TO_LOAD_WEIGHT(rp) \ (PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp)) static void set_load_weight(struct task_struct *p) { if (has_rt_policy(p)) { #ifdef CONFIG_SMP if (p == task_rq(p)->migration_thread) /* * The migration thread does the actual balancing. * Giving its load any weight will skew balancing * adversely. */ p->load_weight = 0; else #endif p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority); } else p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio); } static inline void inc_raw_weighted_load(struct rq *rq, const struct task_struct *p) { rq->raw_weighted_load += p->load_weight; } static inline void dec_raw_weighted_load(struct rq *rq, const struct task_struct *p) { rq->raw_weighted_load -= p->load_weight; } static inline void inc_nr_running(struct task_struct *p, struct rq *rq) { rq->nr_running++; inc_raw_weighted_load(rq, p); } static inline void dec_nr_running(struct task_struct *p, struct rq *rq) { rq->nr_running--; dec_raw_weighted_load(rq, p); } /* * Calculate the expected normal priority: i.e. priority * without taking RT-inheritance into account. Might be * boosted by interactivity modifiers. Changes upon fork, * setprio syscalls, and whenever the interactivity * estimator recalculates. */ static inline int normal_prio(struct task_struct *p) { int prio; if (has_rt_policy(p)) prio = MAX_RT_PRIO-1 - p->rt_priority; else prio = __normal_prio(p); return prio; } /* * Calculate the current priority, i.e. the priority * taken into account by the scheduler. This value might * be boosted by RT tasks, or might be boosted by * interactivity modifiers. Will be RT if the task got * RT-boosted. If not then it returns p->normal_prio. */ static int effective_prio(struct task_struct *p) { p->normal_prio = normal_prio(p); /* * If we are RT tasks or we were boosted to RT priority, * keep the priority unchanged. Otherwise, update priority * to the normal priority: */ if (!rt_prio(p->prio)) return p->normal_prio; return p->prio; } /* * __activate_task - move a task to the runqueue. */ static void __activate_task(struct task_struct *p, struct rq *rq) { struct prio_array *target = rq->active; if (batch_task(p)) target = rq->expired; enqueue_task(p, target); inc_nr_running(p, rq); } /* * __activate_idle_task - move idle task to the _front_ of runqueue. */ static inline void __activate_idle_task(struct task_struct *p, struct rq *rq) { enqueue_task_head(p, rq->active); inc_nr_running(p, rq); } /* * Recalculate p->normal_prio and p->prio after having slept, * updating the sleep-average too: */ static int recalc_task_prio(struct task_struct *p, unsigned long long now) { /* Caller must always ensure 'now >= p->timestamp' */ unsigned long sleep_time = now - p->timestamp; if (batch_task(p)) sleep_time = 0; if (likely(sleep_time > 0)) { /* * This ceiling is set to the lowest priority that would allow * a task to be reinserted into the active array on timeslice * completion. */ unsigned long ceiling = INTERACTIVE_SLEEP(p); if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) { /* * Prevents user tasks from achieving best priority * with one single large enough sleep. */ p->sleep_avg = ceiling; /* * Using INTERACTIVE_SLEEP() as a ceiling places a * nice(0) task 1ms sleep away from promotion, and * gives it 700ms to round-robin with no chance of * being demoted. This is more than generous, so * mark this sleep as non-interactive to prevent the * on-runqueue bonus logic from intervening should * this task not receive cpu immediately. */ p->sleep_type = SLEEP_NONINTERACTIVE; } else { /* * Tasks waking from uninterruptible sleep are * limited in their sleep_avg rise as they * are likely to be waiting on I/O */ if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) { if (p->sleep_avg >= ceiling) sleep_time = 0; else if (p->sleep_avg + sleep_time >= ceiling) { p->sleep_avg = ceiling; sleep_time = 0; } } /* * This code gives a bonus to interactive tasks. * * The boost works by updating the 'average sleep time' * value here, based on ->timestamp. The more time a * task spends sleeping, the higher the average gets - * and the higher the priority boost gets as well. */ p->sleep_avg += sleep_time; } if (p->sleep_avg > NS_MAX_SLEEP_AVG) p->sleep_avg = NS_MAX_SLEEP_AVG; } return effective_prio(p); } /* * activate_task - move a task to the runqueue and do priority recalculation * * Update all the scheduling statistics stuff. (sleep average * calculation, priority modifiers, etc.) */ static void activate_task(struct task_struct *p, struct rq *rq, int local) { unsigned long long now; now = sched_clock(); #ifdef CONFIG_SMP if (!local) { /* Compensate for drifting sched_clock */ struct rq *this_rq = this_rq(); now = (now - this_rq->timestamp_last_tick) + rq->timestamp_last_tick; } #endif if (!rt_task(p)) p->prio = recalc_task_prio(p, now); /* * This checks to make sure it's not an uninterruptible task * that is now waking up. */ if (p->sleep_type == SLEEP_NORMAL) { /* * Tasks which were woken up by interrupts (ie. hw events) * are most likely of interactive nature. So we give them * the credit of extending their sleep time to the period * of time they spend on the runqueue, waiting for execution * on a CPU, first time around: */ if (in_interrupt()) p->sleep_type = SLEEP_INTERRUPTED; else { /* * Normal first-time wakeups get a credit too for * on-runqueue time, but it will be weighted down: */ p->sleep_type = SLEEP_INTERACTIVE; } } p->timestamp = now; __activate_task(p, rq); } /* * deactivate_task - remove a task from the runqueue. */ static void deactivate_task(struct task_struct *p, struct rq *rq) { dec_nr_running(p, rq); dequeue_task(p, p->array); p->array = NULL; } /* * resched_task - mark a task 'to be rescheduled now'. * * On UP this means the setting of the need_resched flag, on SMP it * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ #ifdef CONFIG_SMP #ifndef tsk_is_polling #define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG) #endif static void resched_task(struct task_struct *p) { int cpu; assert_spin_locked(&task_rq(p)->lock); if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED))) return; set_tsk_thread_flag(p, TIF_NEED_RESCHED); cpu = task_cpu(p); if (cpu == smp_processor_id()) return; /* NEED_RESCHED must be visible before we test polling */ smp_mb(); if (!tsk_is_polling(p)) smp_send_reschedule(cpu); } #else static inline void resched_task(struct task_struct *p) { assert_spin_locked(&task_rq(p)->lock); set_tsk_need_resched(p); } #endif /** * task_curr - is this task currently executing on a CPU? * @p: the task in question. */ inline int task_curr(const struct task_struct *p) { return cpu_curr(task_cpu(p)) == p; } /* Used instead of source_load when we know the type == 0 */ unsigned long weighted_cpuload(const int cpu) { return cpu_rq(cpu)->raw_weighted_load; } #ifdef CONFIG_SMP struct migration_req { struct list_head list; struct task_struct *task; int dest_cpu; struct completion done; }; /* * The task's runqueue lock must be held. * Returns true if you have to wait for migration thread. */ static int migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req) { struct rq *rq = task_rq(p); /* * 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)) { set_task_cpu(p, dest_cpu); return 0; } init_completion(&req->done); req->task = p; req->dest_cpu = dest_cpu; list_add(&req->list, &rq->migration_queue); return 1; } /* * wait_task_inactive - wait for a thread to unschedule. * * The caller must ensure that the task *will* unschedule sometime soon, * else this function might spin for a *long* time. This function can'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. */ void wait_task_inactive(struct task_struct *p) { unsigned long flags; struct rq *rq; int preempted; repeat: rq = task_rq_lock(p, &flags); /* Must be off runqueue entirely, not preempted. */ if (unlikely(p->array || task_running(rq, p))) { /* If it's preempted, we yield. It could be a while. */ preempted = !task_running(rq, p); task_rq_unlock(rq, &flags); cpu_relax(); if (preempted) yield(); goto repeat; } task_rq_unlock(rq, &flags); } /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread * * Cause a process which is running on another CPU to enter * kernel-mode, without any delay. (to get signals handled.) * * NOTE: this function doesnt have to take the runqueue lock, * because all it wants to ensure is that the remote task enters * the kernel. If the IPI races and the task has been migrated * to another CPU then no harm is done and the purpose has been * achieved as well. */ void kick_process(struct task_struct *p) { int cpu; preempt_disable(); cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); preempt_enable(); } /* * Return a low guess at the load of a migration-source cpu weighted * according to the scheduling class and "nice" value. * * We want to under-estimate the load of migration sources, to * balance conservatively. */ static inline unsigned long source_load(int cpu, int type) { struct rq *rq = cpu_rq(cpu); if (type == 0) return rq->raw_weighted_load; return min(rq->cpu_load[type-1], rq->raw_weighted_load); } /* * Return a high guess at the load of a migration-target cpu weighted * according to the scheduling class and "nice" value. */ static inline unsigned long target_load(int cpu, int type) { struct rq *rq = cpu_rq(cpu); if (type == 0) return rq->raw_weighted_load; return max(rq->cpu_load[type-1], rq->raw_weighted_load); } /* * Return the average load per task on the cpu's run queue */ static inline unsigned long cpu_avg_load_per_task(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long n = rq->nr_running; return n ? rq->raw_weighted_load / n : SCHED_LOAD_SCALE; } /* * find_idlest_group finds and returns the least busy CPU group within the * domain. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu) { struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups; unsigned long min_load = ULONG_MAX, this_load = 0; int load_idx = sd->forkexec_idx; int imbalance = 100 + (sd->imbalance_pct-100)/2; do { unsigned long load, avg_load; int local_group; int i; /* Skip over this group if it has no CPUs allowed */ if (!cpus_intersects(group->cpumask, p->cpus_allowed)) goto nextgroup; local_group = cpu_isset(this_cpu, group->cpumask); /* Tally up the load of all CPUs in the group */ avg_load = 0; for_each_cpu_mask(i, group->cpumask) { /* Bias balancing toward cpus of our domain */ if (local_group) load = source_load(i, load_idx); else load = target_load(i, load_idx); avg_load += load; } /* Adjust by relative CPU power of the group */ avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power; if (local_group) { this_load = avg_load; this = group; } else if (avg_load < min_load) { min_load = avg_load; idlest = group; } nextgroup: group = group->next; } while (group != sd->groups); if (!idlest || 100*this_load < imbalance*min_load) return NULL; return idlest; } /* * find_idlest_queue - find the idlest runqueue among the cpus in group. */ static int find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { cpumask_t tmp; unsigned long load, min_load = ULONG_MAX; int idlest = -1; int i; /* Traverse only the allowed CPUs */ cpus_and(tmp, group->cpumask, p->cpus_allowed); for_each_cpu_mask(i, tmp) { load = weighted_cpuload(i); if (load < min_load || (load == min_load && i == this_cpu)) { min_load = load; idlest = i; } } return idlest; } /* * sched_balance_self: balance the current task (running on cpu) in domains * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and * SD_BALANCE_EXEC. * * Balance, ie. select the least loaded group. * * Returns the target CPU number, or the same CPU if no balancing is needed. * * preempt must be disabled. */ static int sched_balance_self(int cpu, int flag) { struct task_struct *t = current; struct sched_domain *tmp, *sd = NULL; for_each_domain(cpu, tmp) { /* * If power savings logic is enabled for a domain, stop there. */ if (tmp->flags & SD_POWERSAVINGS_BALANCE) break; if (tmp->flags & flag) sd = tmp; } while (sd) { cpumask_t span; struct sched_group *group; int new_cpu; int weight; span = sd->span; group = find_idlest_group(sd, t, cpu); if (!group) goto nextlevel; new_cpu = find_idlest_cpu(group, t, cpu); if (new_cpu == -1 || new_cpu == cpu) goto nextlevel; /* Now try balancing at a lower domain level */ cpu = new_cpu; nextlevel: sd = NULL; weight = cpus_weight(span); for_each_domain(cpu, tmp) { if (weight <= cpus_weight(tmp->span)) break; if (tmp->flags & flag) sd = tmp; } /* while loop will break here if sd == NULL */ } return cpu; } #endif /* CONFIG_SMP */ /* * wake_idle() will wake a task on an idle cpu if task->cpu is * not idle and an idle cpu is available. The span of cpus to * search starts with cpus closest then further out as needed, * so we always favor a closer, idle cpu. * * Returns the CPU we should wake onto. */ #if defined(ARCH_HAS_SCHED_WAKE_IDLE) static int wake_idle(int cpu, struct task_struct *p) { cpumask_t tmp; struct sched_domain *sd; int i; if (idle_cpu(cpu)) return cpu; for_each_domain(cpu, sd) { if (sd->flags & SD_WAKE_IDLE) { cpus_and(tmp, sd->span, p->cpus_allowed); for_each_cpu_mask(i, tmp) { if (idle_cpu(i)) return i; } } else break; } return cpu; } #else static inline int wake_idle(int cpu, struct task_struct *p) { return cpu; } #endif /*** * try_to_wake_up - wake up a thread * @p: the to-be-woken-up thread * @state: the mask of task states that can be woken * @sync: do a synchronous wakeup? * * Put it on the run-queue if it's not already there. The "current" * thread is always on the run-queue (except when the actual * re-schedule is in progress), and as such you're allowed to do * the simpler "current->state = TASK_RUNNING" to mark yourself * runnable without the overhead of this. * * returns failure only if the task is already active. */ static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync) { int cpu, this_cpu, success = 0; unsigned long flags; long old_state; struct rq *rq; #ifdef CONFIG_SMP struct sched_domain *sd, *this_sd = NULL; unsigned long load, this_load; int new_cpu; #endif rq = task_rq_lock(p, &flags); old_state = p->state; if (!(old_state & state)) goto out; if (p->array) goto out_running; cpu = task_cpu(p); this_cpu = smp_processor_id(); #ifdef CONFIG_SMP if (unlikely(task_running(rq, p))) goto out_activate; new_cpu = cpu; schedstat_inc(rq, ttwu_cnt); if (cpu == this_cpu) { schedstat_inc(rq, ttwu_local); goto out_set_cpu; } for_each_domain(this_cpu, sd) { if (cpu_isset(cpu, sd->span)) { schedstat_inc(sd, ttwu_wake_remote); this_sd = sd; break; } } if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed))) goto out_set_cpu; /* * Check for affine wakeup and passive balancing possibilities. */ if (this_sd) { int idx = this_sd->wake_idx; unsigned int imbalance; imbalance = 100 + (this_sd->imbalance_pct - 100) / 2; load = source_load(cpu, idx); this_load = target_load(this_cpu, idx); new_cpu = this_cpu; /* Wake to this CPU if we can */ if (this_sd->flags & SD_WAKE_AFFINE) { unsigned long tl = this_load; unsigned long tl_per_task = cpu_avg_load_per_task(this_cpu); /* * If sync wakeup then subtract the (maximum possible) * effect of the currently running task from the load * of the current CPU: */ if (sync) tl -= current->load_weight; if ((tl <= load && tl + target_load(cpu, idx) <= tl_per_task) || 100*(tl + p->load_weight) <= imbalance*load) { /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and * there is no bad imbalance. */ schedstat_inc(this_sd, ttwu_move_affine); goto out_set_cpu; } } /* * Start passive balancing when half the imbalance_pct * limit is reached. */ if (this_sd->flags & SD_WAKE_BALANCE) { if (imbalance*this_load <= 100*load) { schedstat_inc(this_sd, ttwu_move_balance); goto out_set_cpu; } } } new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */ out_set_cpu: new_cpu = wake_idle(new_cpu, p); if (new_cpu != cpu) { set_task_cpu(p, new_cpu); task_rq_unlock(rq, &flags); /* might preempt at this point */ rq = task_rq_lock(p, &flags); old_state = p->state; if (!(old_state & state)) goto out; if (p->array) goto out_running; this_cpu = smp_processor_id(); cpu = task_cpu(p); } out_activate: #endif /* CONFIG_SMP */ if (old_state == TASK_UNINTERRUPTIBLE) { rq->nr_uninterruptible--; /* * Tasks on involuntary sleep don't earn * sleep_avg beyond just interactive state. */ p->sleep_type = SLEEP_NONINTERACTIVE; } else /* * Tasks that have marked their sleep as noninteractive get * woken up with their sleep average not weighted in an * interactive way. */ if (old_state & TASK_NONINTERACTIVE) p->sleep_type = SLEEP_NONINTERACTIVE; activate_task(p, rq, cpu == this_cpu); /* * Sync wakeups (i.e. those types of wakeups where the waker * has indicated that it will leave the CPU in short order) * don't trigger a preemption, if the woken up task will run on * this cpu. (in this case the 'I will reschedule' promise of * the waker guarantees that the freshly woken up task is going * to be considered on this CPU.) */ if (!sync || cpu != this_cpu) { if (TASK_PREEMPTS_CURR(p, rq)) resched_task(rq->curr); } success = 1; out_running: p->state = TASK_RUNNING; out: task_rq_unlock(rq, &flags); return success; } int fastcall wake_up_process(struct task_struct *p) { return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED | TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0); } EXPORT_SYMBOL(wake_up_process); int fastcall wake_up_state(struct task_struct *p, unsigned int state) { return try_to_wake_up(p, state, 0); } /* * Perform scheduler related setup for a newly forked process p. * p is forked by current. */ void fastcall sched_fork(struct task_struct *p, int clone_flags) { int cpu = get_cpu(); #ifdef CONFIG_SMP cpu = sched_balance_self(cpu, SD_BALANCE_FORK); #endif set_task_cpu(p, cpu); /* * We mark the process as running here, but have not actually * inserted it onto the runqueue yet. This guarantees that * nobody will actually run it, and a signal or other external * event cannot wake it up and insert it on the runqueue either. */ p->state = TASK_RUNNING; /* * Make sure we do not leak PI boosting priority to the child: */ p->prio = current->normal_prio; INIT_LIST_HEAD(&p->run_list); p->array = NULL; #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) if (unlikely(sched_info_on())) memset(&p->sched_info, 0, sizeof(p->sched_info)); #endif #if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW) p->oncpu = 0; #endif #ifdef CONFIG_PREEMPT /* Want to start with kernel preemption disabled. */ task_thread_info(p)->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; scheduler_tick(); } local_irq_enable(); put_cpu(); } /* * wake_up_new_task - wake up a newly created task for the first time. * * This function will do some initial scheduler statistics housekeeping * that must be done for every newly created context, then puts the task * on the runqueue and wakes it. */ void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags) { struct rq *rq, *this_rq; unsigned long flags; int this_cpu, cpu; rq = task_rq_lock(p, &flags); BUG_ON(p->state != TASK_RUNNING); this_cpu = smp_processor_id(); cpu = task_cpu(p); /* * We decrease the sleep average of forking parents * and children as well, to keep max-interactive tasks * from forking tasks that are max-interactive. The parent * (current) is done further down, under its lock. */ p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) * CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS); p->prio = effective_prio(p); if (likely(cpu == this_cpu)) { if (!(clone_flags & CLONE_VM)) { /* * The VM isn't cloned, so we're in a good position to * do child-runs-first in anticipation of an exec. This * usually avoids a lot of COW overhead. */ if (unlikely(!current->array)) __activate_task(p, rq); else { p->prio = current->prio; p->normal_prio = current->normal_prio; list_add_tail(&p->run_list, ¤t->run_list); p->array = current->array; p->array->nr_active++; inc_nr_running(p, rq); } set_need_resched(); } else /* Run child last */ __activate_task(p, rq); /* * We skip the following code due to cpu == this_cpu * * task_rq_unlock(rq, &flags); * this_rq = task_rq_lock(current, &flags); */ this_rq = rq; } else { this_rq = cpu_rq(this_cpu); /* * Not the local CPU - must adjust timestamp. This should * get optimised away in the !CONFIG_SMP case. */ p->timestamp = (p->timestamp - this_rq->timestamp_last_tick) + rq->timestamp_last_tick; __activate_task(p, rq); if (TASK_PREEMPTS_CURR(p, rq)) resched_task(rq->curr); /* * Parent and child are on different CPUs, now get the * parent runqueue to update the parent's ->sleep_avg: */ task_rq_unlock(rq, &flags); this_rq = task_rq_lock(current, &flags); } current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) * PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS); task_rq_unlock(this_rq, &flags); } /* * 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(struct task_struct *p) { unsigned long flags; struct rq *rq; /* * If the child was a (relative-) CPU hog then decrease * the sleep_avg of the parent as well. */ rq = task_rq_lock(p->parent, &flags); if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) { p->parent->time_slice += p->time_slice; if (unlikely(p->parent->time_slice > task_timeslice(p))) p->parent->time_slice = task_timeslice(p); } if (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); } /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch * @next: the task we are going to switch to. * * This is called with the rq lock held and interrupts off. It must * be paired with a subsequent finish_task_switch after the context * switch. * * prepare_task_switch sets up locking and calls architecture specific * hooks. */ static inline void prepare_task_switch(struct rq *rq, struct task_struct *next) { prepare_lock_switch(rq, next); prepare_arch_switch(next); } /** * finish_task_switch - clean up after a task-switch * @rq: runqueue associated with task-switch * @prev: the thread we just switched away from. * * finish_task_switch must be called after the context switch, paired * with a prepare_task_switch call before the context switch. * finish_task_switch will reconcile locking set up by prepare_task_switch, * and do any other architecture-specific cleanup actions. * * Note that we may have delayed dropping an mm in context_switch(). If * so, we finish that here outside of the runqueue lock. (Doing it * with the lock held can cause deadlocks; see schedule() for * details.) */ static inline void finish_task_switch(struct rq *rq, struct task_struct *prev) __releases(rq->lock) { struct mm_struct *mm = rq->prev_mm; unsigned long prev_task_flags; rq->prev_mm = NULL; /* * A task struct has one reference for the use as "current". * If a task dies, then it sets EXIT_ZOMBIE in tsk->exit_state and * calls schedule one last time. The schedule call will never return, * and the scheduled task must drop that reference. * The test for EXIT_ZOMBIE must occur while the runqueue locks are * still held, otherwise prev could be scheduled on another cpu, die * there before we look at prev->state, and then the reference would * be dropped twice. * Manfred Spraul */ prev_task_flags = prev->flags; finish_arch_switch(prev); finish_lock_switch(rq, prev); if (mm) mmdrop(mm); if (unlikely(prev_task_flags & PF_DEAD)) { /* * Remove function-return probe instances associated with this * task and put them back on the free list. */ kprobe_flush_task(prev); put_task_struct(prev); } } /** * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. */ asmlinkage void schedule_tail(struct task_struct *prev) __releases(rq->lock) { struct rq *rq = this_rq(); finish_task_switch(rq, prev); #ifdef __ARCH_WANT_UNLOCKED_CTXSW /* In this case, finish_task_switch does not reenable preemption */ preempt_enable(); #endif if (current->set_child_tid) put_user(current->pid, current->set_child_tid); } /* * context_switch - switch to the new MM and the new * thread's register state. */ static inline struct task_struct * context_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) { struct mm_struct *mm = next->mm; struct mm_struct *oldmm = prev->active_mm; if (unlikely(!mm)) { next->active_mm = oldmm; atomic_inc(&oldmm->mm_count); enter_lazy_tlb(oldmm, next); } else switch_mm(oldmm, mm, next); if (unlikely(!prev->mm)) { prev->active_mm = NULL; WARN_ON(rq->prev_mm); rq->prev_mm = oldmm; } /* * Since the runqueue lock will be released by the next * task (which is an invalid locking op but in the case * of the scheduler it's an obvious special-case), so we * do an early lockdep release here: */ #ifndef __ARCH_WANT_UNLOCKED_CTXSW spin_release(&rq->lock.dep_map, 1, _THIS_IP_); #endif /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); return prev; } /* * nr_running, nr_uninterruptible and nr_context_switches: * * externally visible scheduler statistics: current number of runnable * threads, current number of uninterruptible-sleeping threads, total * number of context switches performed since bootup. */ unsigned long nr_running(void) { unsigned long i, sum = 0; for_each_online_cpu(i) sum += cpu_rq(i)->nr_running; return sum; } unsigned long nr_uninterruptible(void) { unsigned long i, sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_uninterruptible; /* * Since we read the counters lockless, it might be slightly * inaccurate. Do not allow it to go below zero though: */ if (unlikely((long)sum < 0)) sum = 0; return sum; } unsigned long long nr_context_switches(void) { int i; unsigned long long sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_switches; return sum; } unsigned long nr_iowait(void) { unsigned long i, sum = 0; for_each_possible_cpu(i) sum += atomic_read(&cpu_rq(i)->nr_iowait); return sum; } unsigned long nr_active(void) { unsigned long i, running = 0, uninterruptible = 0; for_each_online_cpu(i) { running += cpu_rq(i)->nr_running; uninterruptible += cpu_rq(i)->nr_uninterruptible; } if (unlikely((long)uninterruptible < 0)) uninterruptible = 0; return running + uninterruptible; } #ifdef CONFIG_SMP /* * Is this task likely cache-hot: */ static inline int task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd) { return (long long)(now - p->last_ran) < (long long)sd->cache_hot_time; } /* * double_rq_lock - safely lock two runqueues * * Note this does not disable interrupts like task_rq_lock, * you need to do so manually before calling. */ static void double_rq_lock(struct rq *rq1, struct rq *rq2) __acquires(rq1->lock) __acquires(rq2->lock) { if (rq1 == rq2) { spin_lock(&rq1->lock); __acquire(rq2->lock); /* Fake it out ;) */ } else { if (rq1 < rq2) { spin_lock(&rq1->lock); spin_lock(&rq2->lock); } else { spin_lock(&rq2->lock); spin_lock(&rq1->lock); } } } /* * double_rq_unlock - safely unlock two runqueues * * Note this does not restore interrupts like task_rq_unlock, * you need to do so manually after calling. */ static void double_rq_unlock(struct rq *rq1, struct rq *rq2) __releases(rq1->lock) __releases(rq2->lock) { spin_unlock(&rq1->lock); if (rq1 != rq2) spin_unlock(&rq2->lock); else __release(rq2->lock); } /* * double_lock_balance - lock the busiest runqueue, this_rq is locked already. */ static void double_lock_balance(struct rq *this_rq, struct rq *busiest) __releases(this_rq->lock) __acquires(busiest->lock) __acquires(this_rq->lock) { if (unlikely(!spin_trylock(&busiest->lock))) { if (busiest < this_rq) { spin_unlock(&this_rq->lock); spin_lock(&busiest->lock); spin_lock(&this_rq->lock); } else spin_lock(&busiest->lock); } } /* * If dest_cpu is allowed for this process, migrate the task to it. * This is accomplished by forcing the cpu_allowed mask to only * allow dest_cpu, which will force the cpu onto dest_cpu. Then * the cpu_allowed mask is restored. */ static void sched_migrate_task(struct task_struct *p, int dest_cpu) { struct migration_req req; unsigned long flags; struct rq *rq; rq = task_rq_lock(p, &flags); if (!cpu_isset(dest_cpu, p->cpus_allowed) || unlikely(cpu_is_offline(dest_cpu))) goto out; /* force the process onto the specified CPU */ if (migrate_task(p, dest_cpu, &req)) { /* Need to wait for migration thread (might exit: take ref). */ struct task_struct *mt = rq->migration_thread; get_task_struct(mt); task_rq_unlock(rq, &flags); wake_up_process(mt); put_task_struct(mt); wait_for_completion(&req.done); return; } out: task_rq_unlock(rq, &flags); } /* * sched_exec - execve() is a valuable balancing opportunity, because at * this point the task has the smallest effective memory and cache footprint. */ void sched_exec(void) { int new_cpu, this_cpu = get_cpu(); new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC); put_cpu(); if (new_cpu != this_cpu) sched_migrate_task(current, new_cpu); } /* * pull_task - move a task from a remote runqueue to the local runqueue. * Both runqueues must be locked. */ static void pull_task(struct rq *src_rq, struct prio_array *src_array, struct task_struct *p, struct rq *this_rq, struct prio_array *this_array, int this_cpu) { dequeue_task(p, src_array); dec_nr_running(p, src_rq); set_task_cpu(p, this_cpu); inc_nr_running(p, this_rq); enqueue_task(p, this_array); 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)) resched_task(this_rq->curr); } /* * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? */ static int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, struct sched_domain *sd, enum idle_type idle, int *all_pinned) { /* * We do not migrate tasks that are: * 1) running (obviously), or * 2) cannot be migrated to this CPU due to cpus_allowed, or * 3) are cache-hot on their current CPU. */ if (!cpu_isset(this_cpu, p->cpus_allowed)) return 0; *all_pinned = 0; if (task_running(rq, p)) return 0; /* * Aggressive migration if: * 1) task is cache cold, or * 2) too many balance attempts have failed. */ if (sd->nr_balance_failed > sd->cache_nice_tries) return 1; if (task_hot(p, rq->timestamp_last_tick, sd)) return 0; return 1; } #define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio) /* * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted * load from busiest to this_rq, as part of a balancing operation within * "domain". Returns the number of tasks moved. * * Called with both runqueues locked. */ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest, unsigned long max_nr_move, unsigned long max_load_move, struct sched_domain *sd, enum idle_type idle, int *all_pinned) { int idx, pulled = 0, pinned = 0, this_best_prio, best_prio, best_prio_seen, skip_for_load; struct prio_array *array, *dst_array; struct list_head *head, *curr; struct task_struct *tmp; long rem_load_move; if (max_nr_move == 0 || max_load_move == 0) goto out; rem_load_move = max_load_move; pinned = 1; this_best_prio = rq_best_prio(this_rq); best_prio = rq_best_prio(busiest); /* * Enable handling of the case where there is more than one task * with the best priority. If the current running task is one * of those with prio==best_prio we know it won't be moved * and therefore it's safe to override the skip (based on load) of * any task we find with that prio. */ best_prio_seen = best_prio == busiest->curr->prio; /* * 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); 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; } goto out; } head = array->queue + idx; curr = head->prev; skip_queue: tmp = list_entry(curr, struct task_struct, run_list); curr = curr->prev; /* * To help distribute high priority tasks accross CPUs we don't * skip a task if it will be the highest priority task (i.e. smallest * prio value) on its new queue regardless of its load weight */ skip_for_load = tmp->load_weight > rem_load_move; if (skip_for_load && idx < this_best_prio) skip_for_load = !best_prio_seen && idx == best_prio; if (skip_for_load || !can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) { best_prio_seen |= idx == best_prio; if (curr != head) goto skip_queue; idx++; goto skip_bitmap; } #ifdef CONFIG_SCHEDSTATS if (task_hot(tmp, busiest->timestamp_last_tick, sd)) schedstat_inc(sd, lb_hot_gained[idle]); #endif pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu); pulled++; rem_load_move -= tmp->load_weight; /* * We only want to steal up to the prescribed number of tasks * and the prescribed amount of weighted load. */ if (pulled < max_nr_move && rem_load_move > 0) { if (idx < this_best_prio) this_best_prio = idx; if (curr != head) goto skip_queue; idx++; goto skip_bitmap; } out: /* * Right now, this is the only place pull_task() is called, * so we can safely collect pull_task() stats here rather than * inside pull_task(). */ schedstat_add(sd, lb_gained[idle], pulled); if (all_pinned) *all_pinned = pinned; return pulled; } /* * find_busiest_group finds and returns the busiest CPU group within the * domain. It calculates and returns the amount of weighted load which * should be moved to restore balance via the imbalance parameter. */ static struct sched_group * find_busiest_group(struct sched_domain *sd, int this_cpu, unsigned long *imbalance, enum idle_type idle, int *sd_idle) { struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups; unsigned long max_load, avg_load, total_load, this_load, total_pwr; unsigned long max_pull; unsigned long busiest_load_per_task, busiest_nr_running; unsigned long this_load_per_task, this_nr_running; int load_idx; #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) int power_savings_balance = 1; unsigned long leader_nr_running = 0, min_load_per_task = 0; unsigned long min_nr_running = ULONG_MAX; struct sched_group *group_min = NULL, *group_leader = NULL; #endif max_load = this_load = total_load = total_pwr = 0; busiest_load_per_task = busiest_nr_running = 0; this_load_per_task = this_nr_running = 0; if (idle == NOT_IDLE) load_idx = sd->busy_idx; else if (idle == NEWLY_IDLE) load_idx = sd->newidle_idx; else load_idx = sd->idle_idx; do { unsigned long load, group_capacity; int local_group; int i; unsigned long sum_nr_running, sum_weighted_load; local_group = cpu_isset(this_cpu, group->cpumask); /* Tally up the load of all CPUs in the group */ sum_weighted_load = sum_nr_running = avg_load = 0; for_each_cpu_mask(i, group->cpumask) { struct rq *rq = cpu_rq(i); if (*sd_idle && !idle_cpu(i)) *sd_idle = 0; /* Bias balancing toward cpus of our domain */ if (local_group) load = target_load(i, load_idx); else load = source_load(i, load_idx); avg_load += load; sum_nr_running += rq->nr_running; sum_weighted_load += rq->raw_weighted_load; } total_load += avg_load; total_pwr += group->cpu_power; /* Adjust by relative CPU power of the group */ avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power; group_capacity = group->cpu_power / SCHED_LOAD_SCALE; if (local_group) { this_load = avg_load; this = group; this_nr_running = sum_nr_running; this_load_per_task = sum_weighted_load; } else if (avg_load > max_load && sum_nr_running > group_capacity) { max_load = avg_load; busiest = group; busiest_nr_running = sum_nr_running; busiest_load_per_task = sum_weighted_load; } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) /* * Busy processors will not participate in power savings * balance. */ if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE)) goto group_next; /* * If the local group is idle or completely loaded * no need to do power savings balance at this domain */ if (local_group && (this_nr_running >= group_capacity || !this_nr_running)) power_savings_balance = 0; /* * If a group is already running at full capacity or idle, * don't include that group in power savings calculations */ if (!power_savings_balance || sum_nr_running >= group_capacity || !sum_nr_running) goto group_next; /* * Calculate the group which has the least non-idle load. * This is the group from where we need to pick up the load * for saving power */ if ((sum_nr_running < min_nr_running) || (sum_nr_running == min_nr_running && first_cpu(group->cpumask) < first_cpu(group_min->cpumask))) { group_min = group; min_nr_running = sum_nr_running; min_load_per_task = sum_weighted_load / sum_nr_running; } /* * Calculate the group which is almost near its * capacity but still has some space to pick up some load * from other group and save more power */ if (sum_nr_running <= group_capacity - 1) { if (sum_nr_running > leader_nr_running || (sum_nr_running == leader_nr_running && first_cpu(group->cpumask) > first_cpu(group_leader->cpumask))) { group_leader = group; leader_nr_running = sum_nr_running; } } group_next: #endif group = group->next; } while (group != sd->groups); if (!busiest || this_load >= max_load || busiest_nr_running == 0) goto out_balanced; avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr; if (this_load >= avg_load || 100*max_load <= sd->imbalance_pct*this_load) goto out_balanced; busiest_load_per_task /= busiest_nr_running; /* * We're trying to get all the cpus to the average_load, so we don't * want to push ourselves above the average load, nor do we wish to * reduce the max loaded cpu below the average load, as either of these * actions would just result in more rebalancing later, and ping-pong * tasks around. Thus we look for the minimum possible imbalance. * Negative imbalances (*we* are more loaded than anyone else) will * be counted as no imbalance for these purposes -- we can't fix that * by pulling tasks to us. Be careful of negative numbers as they'll * appear as very large values with unsigned longs. */ if (max_load <= busiest_load_per_task) goto out_balanced; /* * In the presence of smp nice balancing, certain scenarios can have * max load less than avg load(as we skip the groups at or below * its cpu_power, while calculating max_load..) */ if (max_load < avg_load) { *imbalance = 0; goto small_imbalance; } /* Don't want to pull so many tasks that a group would go idle */ max_pull = min(max_load - avg_load, max_load - busiest_load_per_task); /* How much load to actually move to equalise the imbalance */ *imbalance = min(max_pull * busiest->cpu_power, (avg_load - this_load) * this->cpu_power) / SCHED_LOAD_SCALE; /* * if *imbalance is less than the average load per runnable task * there is no gaurantee that any tasks will be moved so we'll have * a think about bumping its value to force at least one task to be * moved */ if (*imbalance < busiest_load_per_task) { unsigned long tmp, pwr_now, pwr_move; unsigned int imbn; small_imbalance: pwr_move = pwr_now = 0; imbn = 2; if (this_nr_running) { this_load_per_task /= this_nr_running; if (busiest_load_per_task > this_load_per_task) imbn = 1; } else this_load_per_task = SCHED_LOAD_SCALE; if (max_load - this_load >= busiest_load_per_task * imbn) { *imbalance = busiest_load_per_task; return busiest; } /* * OK, we don't have enough imbalance to justify moving tasks, * however we may be able to increase total CPU power used by * moving them. */ pwr_now += busiest->cpu_power * min(busiest_load_per_task, max_load); pwr_now += this->cpu_power * min(this_load_per_task, this_load); pwr_now /= SCHED_LOAD_SCALE; /* Amount of load we'd subtract */ tmp = bu