/* * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) * * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> * * Interactivity improvements by Mike Galbraith * (C) 2007 Mike Galbraith <efault@gmx.de> * * Various enhancements by Dmitry Adamushko. * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> * * Group scheduling enhancements by Srivatsa Vaddagiri * Copyright IBM Corporation, 2007 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> * * Scaled math optimizations by Thomas Gleixner * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de> * * Adaptive scheduling granularity, math enhancements by Peter Zijlstra * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> */ #include <linux/latencytop.h> /* * Targeted preemption latency for CPU-bound tasks: * (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds) * * NOTE: this latency value is not the same as the concept of * 'timeslice length' - timeslices in CFS are of variable length * and have no persistent notion like in traditional, time-slice * based scheduling concepts. * * (to see the precise effective timeslice length of your workload, * run vmstat and monitor the context-switches (cs) field) */ unsigned int sysctl_sched_latency = 20000000ULL; /* * Minimal preemption granularity for CPU-bound tasks: * (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds) */ unsigned int sysctl_sched_min_granularity = 4000000ULL; /* * is kept at sysctl_sched_latency / sysctl_sched_min_granularity */ static unsigned int sched_nr_latency = 5; /* * After fork, child runs first. (default) If set to 0 then * parent will (try to) run first. */ const_debug unsigned int sysctl_sched_child_runs_first = 1; /* * sys_sched_yield() compat mode * * This option switches the agressive yield implementation of the * old scheduler back on. */ unsigned int __read_mostly sysctl_sched_compat_yield; /* * SCHED_BATCH wake-up granularity. * (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds) * * This option delays the preemption effects of decoupled workloads * and reduces their over-scheduling. Synchronous workloads will still * have immediate wakeup/sleep latencies. */ unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL; /* * SCHED_OTHER wake-up granularity. * (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds) * * This option delays the preemption effects of decoupled workloads * and reduces their over-scheduling. Synchronous workloads will still * have immediate wakeup/sleep latencies. */ unsigned int sysctl_sched_wakeup_granularity = 10000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; /************************************************************** * CFS operations on generic schedulable entities: */ #ifdef CONFIG_FAIR_GROUP_SCHED /* cpu runqueue to which this cfs_rq is attached */ static inline struct rq *rq_of(struct cfs_rq *cfs_rq) { return cfs_rq->rq; } /* An entity is a task if it doesn't "own" a runqueue */ #define entity_is_task(se) (!se->my_q) #else /* CONFIG_FAIR_GROUP_SCHED */ static inline struct rq *rq_of(struct cfs_rq *cfs_rq) { return container_of(cfs_rq, struct rq, cfs); } #define entity_is_task(se) 1 #endif /* CONFIG_FAIR_GROUP_SCHED */ static inline struct task_struct *task_of(struct sched_entity *se) { return container_of(se, struct task_struct, se); } /************************************************************** * Scheduling class tree data structure manipulation methods: */ static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime) { s64 delta = (s64)(vruntime - min_vruntime); if (delta > 0) min_vruntime = vruntime; return min_vruntime; } static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) { s64 delta = (s64)(vruntime - min_vruntime); if (delta < 0) min_vruntime = vruntime; return min_vruntime; } static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) { return se->vruntime - cfs_rq->min_vruntime; } /* * Enqueue an entity into the rb-tree: */ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; struct rb_node *parent = NULL; struct sched_entity *entry; s64 key = entity_key(cfs_rq, se); int leftmost = 1; /* * Find the right place in the rbtree: */ while (*link) { parent = *link; entry = rb_entry(parent, struct sched_entity, run_node); /* * We dont care about collisions. Nodes with * the same key stay together. */ if (key < entity_key(cfs_rq, entry)) { link = &parent->rb_left; } else { link = &parent->rb_right; leftmost = 0; } } /* * Maintain a cache of leftmost tree entries (it is frequently * used): */ if (leftmost) cfs_rq->rb_leftmost = &se->run_node; rb_link_node(&se->run_node, parent, link); rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); } static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->rb_leftmost == &se->run_node) cfs_rq->rb_leftmost = rb_next(&se->run_node); rb_erase(&se->run_node, &cfs_rq->tasks_timeline); } static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq) { return cfs_rq->rb_leftmost; } static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) { return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node); } static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; struct sched_entity *se = NULL; struct rb_node *parent; while (*link) { parent = *link; se = rb_entry(parent, struct sched_entity, run_node); link = &parent->rb_right; } return se; } /************************************************************** * Scheduling class statistics methods: */ #ifdef CONFIG_SCHED_DEBUG int sched_nr_latency_handler(struct ctl_table *table, int write, struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos); if (ret || !write) return ret; sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, sysctl_sched_min_granularity); return 0; } #endif /* * The idea is to set a period in which each task runs once. * * When there are too many tasks (sysctl_sched_nr_latency) we have to stretch * this period because otherwise the slices get too small. * * p = (nr <= nl) ? l : l*nr/nl */ static u64 __sched_period(unsigned long nr_running) { u64 period = sysctl_sched_latency; unsigned long nr_latency = sched_nr_latency; if (unlikely(nr_running > nr_latency)) { period = sysctl_sched_min_granularity; period *= nr_running; } return period; } /* * We calculate the wall-time slice from the period by taking a part * proportional to the weight. * * s = p*w/rw */ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) { u64 slice = __sched_period(cfs_rq->nr_running); slice *= se->load.weight; do_div(slice, cfs_rq->load.weight); return slice; } /* * We calculate the vruntime slice. * * vs = s/w = p/rw */ static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running) { u64 vslice = __sched_period(nr_running); vslice *= NICE_0_LOAD; do_div(vslice, rq_weight); return vslice; } static u64 sched_vslice(struct cfs_rq *cfs_rq) { return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running); } static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se) { return __sched_vslice(cfs_rq->load.weight + se->load.weight, cfs_rq->nr_running + 1); } /* * Update the current task's runtime statistics. Skip current tasks that * are not in our scheduling class. */ static inline void __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr, unsigned long delta_exec) { unsigned long delta_exec_weighted; u64 vruntime; schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max)); curr->sum_exec_runtime += delta_exec; schedstat_add(cfs_rq, exec_clock, delta_exec); delta_exec_weighted = delta_exec; if (unlikely(curr->load.weight != NICE_0_LOAD)) { delta_exec_weighted = calc_delta_fair(delta_exec_weighted, &curr->load); } curr->vruntime += delta_exec_weighted; /* * maintain cfs_rq->min_vruntime to be a monotonic increasing * value tracking the leftmost vruntime in the tree. */ if (first_fair(cfs_rq)) { vruntime = min_vruntime(curr->vruntime, __pick_next_entity(cfs_rq)->vruntime); } else vruntime = curr->vruntime; cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); } static void update_curr(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; u64 now = rq_of(cfs_rq)->clock; unsigned long delta_exec; if (unlikely(!curr)) return; /* * Get the amount of time the current task was running * since the last time we changed load (this cannot * overflow on 32 bits): */ delta_exec = (unsigned long)(now - curr->exec_start); __update_curr(cfs_rq, curr, delta_exec); curr->exec_start = now; if (entity_is_task(curr)) { struct task_struct *curtask = task_of(curr); cpuacct_charge(curtask, delta_exec); } } static inline void update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) { schedstat_set(se->wait_start, rq_of(cfs_rq)->clock); } /* * Task is being enqueued - update stats: */ static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* * Are we enqueueing a waiting task? (for current tasks * a dequeue/enqueue event is a NOP) */ if (se != cfs_rq->curr) update_stats_wait_start(cfs_rq, se); } static void update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) { schedstat_set(se->wait_max, max(se->wait_max, rq_of(cfs_rq)->clock - se->wait_start)); schedstat_set(se->wait_count, se->wait_count + 1); schedstat_set(se->wait_sum, se->wait_sum + rq_of(cfs_rq)->clock - se->wait_start); schedstat_set(se->wait_start, 0); } static inline void update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* * Mark the end of the wait period if dequeueing a * waiting task: */ if (se != cfs_rq->curr) update_stats_wait_end(cfs_rq, se); } /* * We are picking a new current task - update its stats: */ static inline void update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* * We are starting a new run period: */ se->exec_start = rq_of(cfs_rq)->clock; } /************************************************** * Scheduling class queueing methods: */ static void account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_add(&cfs_rq->load, se->load.weight); cfs_rq->nr_running++; se->on_rq = 1; } static void account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_sub(&cfs_rq->load, se->load.weight); cfs_rq->nr_running--; se->on_rq = 0; } static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) { #ifdef CONFIG_SCHEDSTATS if (se->sleep_start) { u64 delta = rq_of(cfs_rq)->clock - se->sleep_start; struct task_struct *tsk = task_of(se); if ((s64)delta < 0) delta = 0; if (unlikely(delta > se->sleep_max)) se->sleep_max = delta; se->sleep_start = 0; se->sum_sleep_runtime += delta; account_scheduler_latency(tsk, delta >> 10, 1); } if (se->block_start) { u64 delta = rq_of(cfs_rq)->clock - se->block_start; struct task_struct *tsk = task_of(se); if ((s64)delta < 0) delta = 0; if (unlikely(delta > se->block_max)) se->block_max = delta; se->block_start = 0; se->sum_sleep_runtime += delta; /* * Blocking time is in units of nanosecs, so shift by 20 to * get a milliseconds-range estimation of the amount of * time that the task spent sleeping: */ if (unlikely(prof_on == SLEEP_PROFILING)) { profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk), delta >> 20); } account_scheduler_latency(tsk, delta >> 10, 0); } #endif } static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) { #ifdef CONFIG_SCHED_DEBUG s64 d = se->vruntime - cfs_rq->min_vruntime; if (d < 0) d = -d; if (d > 3*sysctl_sched_latency) schedstat_inc(cfs_rq, nr_spread_over); #endif } static void place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) { u64 vruntime; vruntime = cfs_rq->min_vruntime; if (sched_feat(TREE_AVG)) { struct sched_entity *last = __pick_last_entity(cfs_rq); if (last) { vruntime += last->vruntime; vruntime >>= 1; } } else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running) vruntime += sched_vslice(cfs_rq)/2; /* * The 'current' period is already promised to the current tasks, * however the extra weight of the new task will slow them down a * little, place the new task so that it fits in the slot that * stays open at the end. */ if (initial && sched_feat(START_DEBIT)) vruntime += sched_vslice_add(cfs_rq, se); if (!initial) { /* sleeps upto a single latency don't count. */ if (sched_feat(NEW_FAIR_SLEEPERS)) vruntime -= sysctl_sched_latency; /* ensure we never gain time by being placed backwards. */ vruntime = max_vruntime(se->vruntime, vruntime); } se->vruntime = vruntime; } static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup) { /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); if (wakeup) { place_entity(cfs_rq, se, 0); enqueue_sleeper(cfs_rq, se); } update_stats_enqueue(cfs_rq, se); check_spread(cfs_rq, se); if (se != cfs_rq->curr) __enqueue_entity(cfs_rq, se); account_entity_enqueue(cfs_rq, se); } static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep) { /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); update_stats_dequeue(cfs_rq, se); if (sleep) { #ifdef CONFIG_SCHEDSTATS if (entity_is_task(se)) { struct task_struct *tsk = task_of(se); if (tsk->state & TASK_INTERRUPTIBLE) se->sleep_start = rq_of(cfs_rq)->clock; if (tsk->state & TASK_UNINTERRUPTIBLE) se->block_start = rq_of(cfs_rq)->clock; } #endif } if (se != cfs_rq->curr) __dequeue_entity(cfs_rq, se); account_entity_dequeue(cfs_rq, se); } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) { unsigned long ideal_runtime, delta_exec; ideal_runtime = sched_slice(cfs_rq, curr); delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; if (delta_exec > ideal_runtime) resched_task(rq_of(cfs_rq)->curr); } static void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* 'current' is not kept within the tree. */ if (se->on_rq) { /* * Any task has to be enqueued before it get to execute on * a CPU. So account for the time it spent waiting on the * runqueue. */ update_stats_wait_end(cfs_rq, se); __dequeue_entity(cfs_rq, se); } update_stats_curr_start(cfs_rq, se); cfs_rq->curr = se; #ifdef CONFIG_SCHEDSTATS /* * Track our maximum slice length, if the CPU's load is at * least twice that of our own weight (i.e. dont track it * when there are only lesser-weight tasks around): */ if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { se->slice_max = max(se->slice_max, se->sum_exec_runtime - se->prev_sum_exec_runtime); } #endif se->prev_sum_exec_runtime = se->sum_exec_runtime; } static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) { struct sched_entity *se = NULL; if (first_fair(cfs_rq)) { se = __pick_next_entity(cfs_rq); set_next_entity(cfs_rq, se); } return se; } static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) { /* * If still on the runqueue then deactivate_task() * was not called and update_curr() has to be done: */ if (prev->on_rq) update_curr(cfs_rq); check_spread(cfs_rq, prev); if (prev->on_rq) { update_stats_wait_start(cfs_rq, prev); /* Put 'current' back into the tree. */ __enqueue_entity(cfs_rq, prev); } cfs_rq->curr = NULL; } static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) { /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); #ifdef CONFIG_SCHED_HRTICK /* * queued ticks are scheduled to match the slice, so don't bother * validating it and just reschedule. */ if (queued) return resched_task(rq_of(cfs_rq)->curr); /* * don't let the period tick interfere with the hrtick preemption */ if (!sched_feat(DOUBLE_TICK) && hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) return; #endif if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT)) check_preempt_tick(cfs_rq, curr); } /************************************************** * CFS operations on tasks: */ #ifdef CONFIG_FAIR_GROUP_SCHED /* Walk up scheduling entities hierarchy */ #define for_each_sched_entity(se) \ for (; se; se = se->parent) static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) { return p->se.cfs_rq; } /* runqueue on which this entity is (to be) queued */ static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) { return se->cfs_rq; } /* runqueue "owned" by this group */ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) { return grp->my_q; } /* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on * another cpu ('this_cpu') */ static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu) { return cfs_rq->tg->cfs_rq[this_cpu]; } /* Iterate thr' all leaf cfs_rq's on a runqueue */ #define for_each_leaf_cfs_rq(rq, cfs_rq) \ list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) /* Do the two (enqueued) entities belong to the same group ? */ static inline int is_same_group(struct sched_entity *se, struct sched_entity *pse) { if (se->cfs_rq == pse->cfs_rq) return 1; return 0; } static inline struct sched_entity *parent_entity(struct sched_entity *se) { return se->parent; } #define GROUP_IMBALANCE_PCT 20 #else /* CONFIG_FAIR_GROUP_SCHED */ #define for_each_sched_entity(se) \ for (; se; se = NULL) static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) { return &task_rq(p)->cfs; } static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) { struct task_struct *p = task_of(se); struct rq *rq = task_rq(p); return &rq->cfs; } /* runqueue "owned" by this group */ static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) { return NULL; } static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu) { return &cpu_rq(this_cpu)->cfs; } #define for_each_leaf_cfs_rq(rq, cfs_rq) \ for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) static inline int is_same_group(struct sched_entity *se, struct sched_entity *pse) { return 1; } static inline struct sched_entity *parent_entity(struct sched_entity *se) { return NULL; } #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_SCHED_HRTICK static void hrtick_start_fair(struct rq *rq, struct task_struct *p) { int requeue = rq->curr == p; struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); WARN_ON(task_rq(p) != rq); if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) { u64 slice = sched_slice(cfs_rq, se); u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; s64 delta = slice - ran; if (delta < 0) { if (rq->curr == p) resched_task(p); return; } /* * Don't schedule slices shorter than 10000ns, that just * doesn't make sense. Rely on vruntime for fairness. */ if (!requeue) delta = max(10000LL, delta); hrtick_start(rq, delta, requeue); } } #else static inline void hrtick_start_fair(struct rq *rq, struct task_struct *p) { } #endif /* * The enqueue_task method is called before nr_running is * increased. Here we update the fair scheduling stats and * then put the task into the rbtree: */ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se, *topse = NULL; /* Highest schedulable entity */ int incload = 1; for_each_sched_entity(se) { topse = se; if (se->on_rq) { incload = 0; break; } cfs_rq = cfs_rq_of(se); enqueue_entity(cfs_rq, se, wakeup); wakeup = 1; } /* Increment cpu load if we just enqueued the first task of a group on * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs * at the highest grouping level. */ if (incload) inc_cpu_load(rq, topse->load.weight); hrtick_start_fair(rq, rq->curr); } /* * The dequeue_task method is called before nr_running is * decreased. We remove the task from the rbtree and * update the fair scheduling stats: */ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se, *topse = NULL; /* Highest schedulable entity */ int decload = 1; for_each_sched_entity(se) { topse = se; cfs_rq = cfs_rq_of(se); dequeue_entity(cfs_rq, se, sleep); /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { if (parent_entity(se)) decload = 0; break; } sleep = 1; } /* Decrement cpu load if we just dequeued the last task of a group on * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs * at the highest grouping level. */ if (decload) dec_cpu_load(rq, topse->load.weight); hrtick_start_fair(rq, rq->curr); } /* * sched_yield() support is very simple - we dequeue and enqueue. * * If compat_yield is turned on then we requeue to the end of the tree. */ static void yield_task_fair(struct rq *rq) { struct task_struct *curr = rq->curr; struct cfs_rq *cfs_rq = task_cfs_rq(curr); struct sched_entity *rightmost, *se = &curr->se; /* * Are we the only task in the tree? */ if (unlikely(cfs_rq->nr_running == 1)) return; if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) { __update_rq_clock(rq); /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); return; } /* * Find the rightmost entry in the rbtree: */ rightmost = __pick_last_entity(cfs_rq); /* * Already in the rightmost position? */ if (unlikely(rightmost->vruntime < se->vruntime)) return; /* * Minimally necessary key value to be last in the tree: * Upon rescheduling, sched_class::put_prev_task() will place * 'current' within the tree based on its new key value. */ se->vruntime = rightmost->vruntime + 1; } /* * 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 it is idle, then it is the best cpu to run this task. * * This cpu is also the best, if it has more than one task already. * Siblings must be also busy(in most cases) as they didn't already * pickup the extra load from this cpu and hence we need not check * sibling runqueue info. This will avoid the checks and cache miss * penalities associated with that. */ if (idle_cpu(cpu) || cpu_rq(cpu)->nr_running > 1) 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)) { if (i != task_cpu(p)) { schedstat_inc(p, se.nr_wakeups_idle); } return i; } } } else { break; } } return cpu; } #else static inline int wake_idle(int cpu, struct task_struct *p) { return cpu; } #endif #ifdef CONFIG_SMP static int select_task_rq_fair(struct task_struct *p, int sync) { int cpu, this_cpu; struct rq *rq; struct sched_domain *sd, *this_sd = NULL; int new_cpu; cpu = task_cpu(p); rq = task_rq(p); this_cpu = smp_processor_id(); new_cpu = cpu; if (cpu == this_cpu) goto out_set_cpu; for_each_domain(this_cpu, sd) { if (cpu_isset(cpu, sd->span)) { 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; unsigned long load, this_load; 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; /* * Attract cache-cold tasks on sync wakeups: */ if (sync && !task_hot(p, rq->clock, this_sd)) goto out_set_cpu; schedstat_inc(p, se.nr_wakeups_affine_attempts); 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->se.load.weight; if ((tl <= load && tl + target_load(cpu, idx) <= tl_per_task) || 100*(tl + p->se.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); schedstat_inc(p, se.nr_wakeups_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); schedstat_inc(p, se.nr_wakeups_passive); goto out_set_cpu; } } } new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */ out_set_cpu: return wake_idle(new_cpu, p); } #endif /* CONFIG_SMP */ /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) { struct task_struct *curr = rq->curr; struct cfs_rq *cfs_rq = task_cfs_rq(curr); struct sched_entity *se = &curr->se, *pse = &p->se; unsigned long gran; if (unlikely(rt_prio(p->prio))) { update_rq_clock(rq); update_curr(cfs_rq); resched_task(curr); return; } /* * Batch tasks do not preempt (their preemption is driven by * the tick): */ if (unlikely(p->policy == SCHED_BATCH)) return; if (!sched_feat(WAKEUP_PREEMPT)) return; while (!is_same_group(se, pse)) { se = parent_entity(se); pse = parent_entity(pse); } gran = sysctl_sched_wakeup_granularity; /* * More easily preempt - nice tasks, while not making * it harder for + nice tasks. */ if (unlikely(se->load.weight > NICE_0_LOAD)) gran = calc_delta_fair(gran, &se->load); if (pse->vruntime + gran < se->vruntime) resched_task(curr); } static struct task_struct *pick_next_task_fair(struct rq *rq) { struct task_struct *p; struct cfs_rq *cfs_rq = &rq->cfs; struct sched_entity *se; if (unlikely(!cfs_rq->nr_running)) return NULL; do { se = pick_next_entity(cfs_rq); cfs_rq = group_cfs_rq(se); } while (cfs_rq); p = task_of(se); hrtick_start_fair(rq, p); return p; } /* * Account for a descheduled task: */ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) { struct sched_entity *se = &prev->se; struct cfs_rq *cfs_rq; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); put_prev_entity(cfs_rq, se); } } #ifdef CONFIG_SMP /************************************************** * Fair scheduling class load-balancing methods: */ /* * Load-balancing iterator. Note: while the runqueue stays locked * during the whole iteration, the current task might be * dequeued so the iterator has to be dequeue-safe. Here we * achieve that by always pre-iterating before returning * the current task: */ static struct task_struct * __load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr) { struct task_struct *p; if (!curr) return NULL; p = rb_entry(curr, struct task_struct, se.run_node); cfs_rq->rb_load_balance_curr = rb_next(curr); return p; } static struct task_struct *load_balance_start_fair(void *arg) { struct cfs_rq *cfs_rq = arg; return __load_balance_iterator(cfs_rq, first_fair(cfs_rq)); } static struct task_struct *load_balance_next_fair(void *arg) { struct cfs_rq *cfs_rq = arg; return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr); } static unsigned long load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest, unsigned long max_load_move, struct sched_domain *sd, enum cpu_idle_type idle, int *all_pinned, int *this_best_prio) { struct cfs_rq *busy_cfs_rq; long rem_load_move = max_load_move; struct rq_iterator cfs_rq_iterator; unsigned long load_moved; cfs_rq_iterator.start = load_balance_start_fair; cfs_rq_iterator.next = load_balance_next_fair; for_each_leaf_cfs_rq(busiest, busy_cfs_rq) { #ifdef CONFIG_FAIR_GROUP_SCHED struct cfs_rq *this_cfs_rq = busy_cfs_rq->tg->cfs_rq[this_cpu]; unsigned long maxload, task_load, group_weight; unsigned long thisload, per_task_load; struct sched_entity *se = busy_cfs_rq->tg->se[busiest->cpu]; task_load = busy_cfs_rq->load.weight; group_weight = se->load.weight; /* * 'group_weight' is contributed by tasks of total weight * 'task_load'. To move 'rem_load_move' worth of weight only, * we need to move a maximum task load of: * * maxload = (remload / group_weight) * task_load; */ maxload = (rem_load_move * task_load) / group_weight; if (!maxload || !task_load) continue; per_task_load = task_load / busy_cfs_rq->nr_running; /* * balance_tasks will try to forcibly move atleast one task if * possible (because of SCHED_LOAD_SCALE_FUZZ). Avoid that if * maxload is less than GROUP_IMBALANCE_FUZZ% the per_task_load. */ if (100 * maxload < GROUP_IMBALANCE_PCT * per_task_load) continue; /* Disable priority-based load balance */ *this_best_prio = 0; thisload = this_cfs_rq->load.weight; #else # define maxload rem_load_move #endif /* * pass busy_cfs_rq argument into * load_balance_[start|next]_fair iterators */ cfs_rq_iterator.arg = busy_cfs_rq; load_moved = balance_tasks(this_rq, this_cpu, busiest, maxload, sd, idle, all_pinned, this_best_prio, &cfs_rq_iterator); #ifdef CONFIG_FAIR_GROUP_SCHED /* * load_moved holds the task load that was moved. The * effective (group) weight moved would be: * load_moved_eff = load_moved/task_load * group_weight; */ load_moved = (group_weight * load_moved) / task_load; /* Adjust shares on both cpus to reflect load_moved */ group_weight -= load_moved; set_se_shares(se, group_weight); se = busy_cfs_rq->tg->se[this_cpu]; if (!thisload) group_weight = load_moved; else group_weight = se->load.weight + load_moved; set_se_shares(se, group_weight); #endif rem_load_move -= load_moved; if (rem_load_move <= 0) break; } return max_load_move - rem_load_move; } static int move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest, struct sched_domain *sd, enum cpu_idle_type idle) { struct cfs_rq *busy_cfs_rq; struct rq_iterator cfs_rq_iterator; cfs_rq_iterator.start = load_balance_start_fair; cfs_rq_iterator.next = load_balance_next_fair; for_each_leaf_cfs_rq(busiest, busy_cfs_rq) { /* * pass busy_cfs_rq argument into * load_balance_[start|next]_fair iterators */ cfs_rq_iterator.arg = busy_cfs_rq; if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle, &cfs_rq_iterator)) return 1; } return 0; } #endif /* * scheduler tick hitting a task of our scheduling class: */ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) { struct cfs_rq *cfs_rq; struct sched_entity *se = &curr->se; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); entity_tick(cfs_rq, se, queued); } } #define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0) /* * Share the fairness runtime between parent and child, thus the * total amount of pressure for CPU stays equal - new tasks * get a chance to run but frequent forkers are not allowed to * monopolize the CPU. Note: the parent runqueue is locked, * the child is not running yet. */ static void task_new_fair(struct rq *rq, struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(p); struct sched_entity *se = &p->se, *curr = cfs_rq->curr; int this_cpu = smp_processor_id(); sched_info_queued(p); update_curr(cfs_rq); place_entity(cfs_rq, se, 1); /* 'curr' will be NULL if the child belongs to a different group */ if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) && curr && curr->vruntime < se->vruntime) { /* * Upon rescheduling, sched_class::put_prev_task() will place * 'current' within the tree based on its new key value. */ swap(curr->vruntime, se->vruntime); } enqueue_task_fair(rq, p, 0); resched_task(rq->curr); } /* * Priority of the task has changed. Check to see if we preempt * the current task. */ static void prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio, int running) { /* * Reschedule if we are currently running on this runqueue and * our priority decreased, or if we are not currently running on * this runqueue and our priority is higher than the current's */ if (running) { if (p->prio > oldprio) resched_task(rq->curr); } else check_preempt_curr(rq, p); } /* * We switched to the sched_fair class. */ static void switched_to_fair(struct rq *rq, struct task_struct *p, int running) { /* * We were most likely switched from sched_rt, so * kick off the schedule if running, otherwise just see * if we can still preempt the current task. */ if (running) resched_task(rq->curr); else check_preempt_curr(rq, p); } /* Account for a task changing its policy or group. * * This routine is mostly called to set cfs_rq->curr field when a task * migrates between groups/classes. */ static void set_curr_task_fair(struct rq *rq) { struct sched_entity *se = &rq->curr->se; for_each_sched_entity(se) set_next_entity(cfs_rq_of(se), se); } /* * All the scheduling class methods: */ static const struct sched_class fair_sched_class = { .next = &idle_sched_class, .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, #ifdef CONFIG_SMP .select_task_rq = select_task_rq_fair, #endif /* CONFIG_SMP */ .check_preempt_curr = check_preempt_wakeup, .pick_next_task = pick_next_task_fair, .put_prev_task = put_prev_task_fair, #ifdef CONFIG_SMP .load_balance = load_balance_fair, .move_one_task = move_one_task_fair, #endif .set_curr_task = set_curr_task_fair, .task_tick = task_tick_fair, .task_new = task_new_fair, .prio_changed = prio_changed_fair, .switched_to = switched_to_fair, }; #ifdef CONFIG_SCHED_DEBUG static void print_cfs_stats(struct seq_file *m, int cpu) { struct cfs_rq *cfs_rq; #ifdef CONFIG_FAIR_GROUP_SCHED print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs); #endif rcu_read_lock(); for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) print_cfs_rq(m, cpu, cfs_rq); rcu_read_unlock(); } #endif