/* * 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_OTHER wake-up granularity. * (default: 5 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 = 5000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; static const struct sched_class fair_sched_class; /************************************************************** * CFS operations on generic schedulable entities: */ static inline struct task_struct *task_of(struct sched_entity *se) { return container_of(se, struct task_struct, se); } #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) /* 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; } /* return depth at which a sched entity is present in the hierarchy */ static inline int depth_se(struct sched_entity *se) { int depth = 0; for_each_sched_entity(se) depth++; return depth; } static void find_matching_se(struct sched_entity **se, struct sched_entity **pse) { int se_depth, pse_depth; /* * preemption test can be made between sibling entities who are in the * same cfs_rq i.e who have a common parent. Walk up the hierarchy of * both tasks until we find their ancestors who are siblings of common * parent. */ /* First walk up until both entities are at same depth */ se_depth = depth_se(*se); pse_depth = depth_se(*pse); while (se_depth > pse_depth) { se_depth--; *se = parent_entity(*se); } while (pse_depth > se_depth) { pse_depth--; *pse = parent_entity(*pse); } while (!is_same_group(*se, *pse)) { *se = parent_entity(*se); *pse = parent_entity(*pse); } } #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 #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; } static inline void find_matching_se(struct sched_entity **se, struct sched_entity **pse) { } #endif /* CONFIG_FAIR_GROUP_SCHED */ /************************************************************** * 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; } static void update_min_vruntime(struct cfs_rq *cfs_rq) { u64 vruntime = cfs_rq->min_vruntime; if (cfs_rq->curr) vruntime = cfs_rq->curr->vruntime; if (cfs_rq->rb_leftmost) { struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, struct sched_entity, run_node); if (!cfs_rq->curr) vruntime = se->vruntime; else vruntime = min_vruntime(vruntime, se->vruntime); } cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, 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) { struct rb_node *next_node; next_node = rb_next(&se->run_node); cfs_rq->rb_leftmost = next_node; } rb_erase(&se->run_node, &cfs_rq->tasks_timeline); } static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq) { struct rb_node *left = cfs_rq->rb_leftmost; if (!left) return NULL; return rb_entry(left, struct sched_entity, run_node); } static struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) { struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); if (!last) return NULL; return rb_entry(last, struct sched_entity, run_node); } /************************************************************** * 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 /* * delta /= w */ static inline unsigned long calc_delta_fair(unsigned long delta, struct sched_entity *se) { if (unlikely(se->load.weight != NICE_0_LOAD)) delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load); return delta; } /* * 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*P[w/rw] */ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) { u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); for_each_sched_entity(se) { struct load_weight *load; cfs_rq = cfs_rq_of(se); load = &cfs_rq->load; if (unlikely(!se->on_rq)) { struct load_weight lw = cfs_rq->load; update_load_add(&lw, se->load.weight); load = &lw; } slice = calc_delta_mine(slice, se->load.weight, load); } return slice; } /* * We calculate the vruntime slice of a to be inserted task * * vs = s/w */ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) { return calc_delta_fair(sched_slice(cfs_rq, se), se); } /* * 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; 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 = calc_delta_fair(delta_exec, curr); curr->vruntime += delta_exec_weighted; update_min_vruntime(cfs_rq); } 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); if (!delta_exec) return; __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); account_group_exec_runtime(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: */ #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED static void add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight) { cfs_rq->task_weight += weight; } #else static inline void add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight) { } #endif static void account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) { update_load_add(&cfs_rq->load, se->load.weight); if (!parent_entity(se)) inc_cpu_load(rq_of(cfs_rq), se->load.weight); if (entity_is_task(se)) { add_cfs_task_weight(cfs_rq, se->load.weight); list_add(&se->group_node, &cfs_rq->tasks); } 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); if (!parent_entity(se)) dec_cpu_load(rq_of(cfs_rq), se->load.weight); if (entity_is_task(se)) { add_cfs_task_weight(cfs_rq, -se->load.weight); list_del_init(&se->group_node); } 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 = cfs_rq->min_vruntime; /* * 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(cfs_rq, se); if (!initial) { /* sleeps upto a single latency don't count. */ if (sched_feat(NEW_FAIR_SLEEPERS)) { unsigned long thresh = sysctl_sched_latency; /* * Convert the sleeper threshold into virtual time. * SCHED_IDLE is a special sub-class. We care about * fairness only relative to other SCHED_IDLE tasks, * all of which have the same weight. */ if (sched_feat(NORMALIZED_SLEEPER) && task_of(se)->policy != SCHED_IDLE) thresh = calc_delta_fair(thresh, se); vruntime -= thresh; } /* 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); account_entity_enqueue(cfs_rq, se); 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); } static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->last == se) cfs_rq->last = NULL; if (cfs_rq->next == se) cfs_rq->next = NULL; } static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { for_each_sched_entity(se) __clear_buddies(cfs_rq_of(se), 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 } clear_buddies(cfs_rq, se); if (se != cfs_rq->curr) __dequeue_entity(cfs_rq, se); account_entity_dequeue(cfs_rq, se); update_min_vruntime(cfs_rq); } /* * 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); /* * The current task ran long enough, ensure it doesn't get * re-elected due to buddy favours. */ clear_buddies(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 int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) { struct sched_entity *se = __pick_next_entity(cfs_rq); if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, se) < 1) return cfs_rq->next; if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, se) < 1) return cfs_rq->last; 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) { resched_task(rq_of(cfs_rq)->curr); return; } /* * 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_SCHED_HRTICK static void hrtick_start_fair(struct rq *rq, struct task_struct *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 (rq->curr != p) delta = max_t(s64, 10000LL, delta); hrtick_start(rq, delta); } } /* * called from enqueue/dequeue and updates the hrtick when the * current task is from our class and nr_running is low enough * to matter. */ static void hrtick_update(struct rq *rq) { struct task_struct *curr = rq->curr; if (curr->sched_class != &fair_sched_class) return; if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) hrtick_start_fair(rq, curr); } #else /* !CONFIG_SCHED_HRTICK */ static inline void hrtick_start_fair(struct rq *rq, struct task_struct *p) { } static inline void hrtick_update(struct rq *rq) { } #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; for_each_sched_entity(se) { if (se->on_rq) break; cfs_rq = cfs_rq_of(se); enqueue_entity(cfs_rq, se, wakeup); wakeup = 1; } hrtick_update(rq); } /* * 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; for_each_sched_entity(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) break; sleep = 1; } hrtick_update(rq); } /* * 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; clear_buddies(cfs_rq, se); 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 || 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. * Domains may include CPUs that are not usable for migration, * hence we need to mask them out (cpu_active_mask) * * Returns the CPU we should wake onto. */ #if defined(ARCH_HAS_SCHED_WAKE_IDLE) static int wake_idle(int cpu, struct task_struct *p) { struct sched_domain *sd; int i; unsigned int chosen_wakeup_cpu; int this_cpu; /* * At POWERSAVINGS_BALANCE_WAKEUP level, if both this_cpu and prev_cpu * are idle and this is not a kernel thread and this task's affinity * allows it to be moved to preferred cpu, then just move! */ this_cpu = smp_processor_id(); chosen_wakeup_cpu = cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu; if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP && idle_cpu(cpu) && idle_cpu(this_cpu) && p->mm && !(p->flags & PF_KTHREAD) && cpu_isset(chosen_wakeup_cpu, p->cpus_allowed)) return chosen_wakeup_cpu; /* * 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)->cfs.nr_running > 1) return cpu; for_each_domain(cpu, sd) { if ((sd->flags & SD_WAKE_IDLE) || ((sd->flags & SD_WAKE_IDLE_FAR) && !task_hot(p, task_rq(p)->clock, sd))) { for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) { if (cpu_active(i) && idle_cpu(i)) { if (i != task_cpu(p)) { schedstat_inc(p, se.nr_wakeups_idle); } return i; } } } else { break; } } return cpu; } #else /* !ARCH_HAS_SCHED_WAKE_IDLE*/ static inline int wake_idle(int cpu, struct task_struct *p) { return cpu; } #endif #ifdef CONFIG_SMP #ifdef CONFIG_FAIR_GROUP_SCHED /* * effective_load() calculates the load change as seen from the root_task_group * * Adding load to a group doesn't make a group heavier, but can cause movement * of group shares between cpus. Assuming the shares were perfectly aligned one * can calculate the shift in shares. * * The problem is that perfectly aligning the shares is rather expensive, hence * we try to avoid doing that too often - see update_shares(), which ratelimits * this change. * * We compensate this by not only taking the current delta into account, but * also considering the delta between when the shares were last adjusted and * now. * * We still saw a performance dip, some tracing learned us that between * cgroup:/ and cgroup:/foo balancing the number of affine wakeups increased * significantly. Therefore try to bias the error in direction of failing * the affine wakeup. * */ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) { struct sched_entity *se = tg->se[cpu]; if (!tg->parent) return wl; /* * By not taking the decrease of shares on the other cpu into * account our error leans towards reducing the affine wakeups. */ if (!wl && sched_feat(ASYM_EFF_LOAD)) return wl; for_each_sched_entity(se) { long S, rw, s, a, b; long more_w; /* * Instead of using this increment, also add the difference * between when the shares were last updated and now. */ more_w = se->my_q->load.weight - se->my_q->rq_weight; wl += more_w; wg += more_w; S = se->my_q->tg->shares; s = se->my_q->shares; rw = se->my_q->rq_weight; a = S*(rw + wl); b = S*rw + s*wg; wl = s*(a-b); if (likely(b)) wl /= b; /* * Assume the group is already running and will * thus already be accounted for in the weight. * * That is, moving shares between CPUs, does not * alter the group weight. */ wg = 0; } return wl; } #else static inline unsigned long effective_load(struct task_group *tg, int cpu, unsigned long wl, unsigned long wg) { return wl; } #endif static int wake_affine(struct sched_domain *this_sd, struct rq *this_rq, struct task_struct *p, int prev_cpu, int this_cpu, int sync, int idx, unsigned long load, unsigned long this_load, unsigned int imbalance) { struct task_struct *curr = this_rq->curr; struct task_group *tg; unsigned long tl = this_load; unsigned long tl_per_task; unsigned long weight; int balanced; if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS)) return 0; if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost || p->se.avg_overlap > sysctl_sched_migration_cost)) sync = 0; /* * If sync wakeup then subtract the (maximum possible) * effect of the currently running task from the load * of the current CPU: */ if (sync) { tg = task_group(current); weight = current->se.load.weight; tl += effective_load(tg, this_cpu, -weight, -weight); load += effective_load(tg, prev_cpu, 0, -weight); } tg = task_group(p); weight = p->se.load.weight; balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <= imbalance*(load + effective_load(tg, prev_cpu, 0, weight)); /* * If the currently running task will sleep within * a reasonable amount of time then attract this newly * woken task: */ if (sync && balanced) return 1; schedstat_inc(p, se.nr_wakeups_affine_attempts); tl_per_task = cpu_avg_load_per_task(this_cpu); if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task)) { /* * 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); return 1; } return 0; } static int select_task_rq_fair(struct task_struct *p, int sync) { struct sched_domain *sd, *this_sd = NULL; int prev_cpu, this_cpu, new_cpu; unsigned long load, this_load; struct rq *this_rq; unsigned int imbalance; int idx; prev_cpu = task_cpu(p); this_cpu = smp_processor_id(); this_rq = cpu_rq(this_cpu); new_cpu = prev_cpu; if (prev_cpu == this_cpu) goto out; /* * 'this_sd' is the first domain that both * this_cpu and prev_cpu are present in: */ for_each_domain(this_cpu, sd) { if (cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) { this_sd = sd; break; } } if (unlikely(!cpumask_test_cpu(this_cpu, &p->cpus_allowed))) goto out; /* * Check for affine wakeup and passive balancing possibilities. */ if (!this_sd) goto out; idx = this_sd->wake_idx; imbalance = 100 + (this_sd->imbalance_pct - 100) / 2; load = source_load(prev_cpu, idx); this_load = target_load(this_cpu, idx); if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx, load, this_load, imbalance)) return this_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); return this_cpu; } } out: return wake_idle(new_cpu, p); } #endif /* CONFIG_SMP */ /* * Adaptive granularity * * se->avg_wakeup gives the average time a task runs until it does a wakeup, * with the limit of wakeup_gran -- when it never does a wakeup. * * So the smaller avg_wakeup is the faster we want this task to preempt, * but we don't want to treat the preemptee unfairly and therefore allow it * to run for at least the amount of time we'd like to run. * * NOTE: we use 2*avg_wakeup to increase the probability of actually doing one * * NOTE: we use *nr_running to scale with load, this nicely matches the * degrading latency on load. */ static unsigned long adaptive_gran(struct sched_entity *curr, struct sched_entity *se) { u64 this_run = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; u64 expected_wakeup = 2*se->avg_wakeup * cfs_rq_of(se)->nr_running; u64 gran = 0; if (this_run < expected_wakeup) gran = expected_wakeup - this_run; return min_t(s64, gran, sysctl_sched_wakeup_granularity); } static unsigned long wakeup_gran(struct sched_entity *curr, struct sched_entity *se) { unsigned long gran = sysctl_sched_wakeup_granularity; if (cfs_rq_of(curr)->curr && sched_feat(ADAPTIVE_GRAN)) gran = adaptive_gran(curr, se); /* * Since its curr running now, convert the gran from real-time * to virtual-time in his units. */ if (sched_feat(ASYM_GRAN)) { /* * By using 'se' instead of 'curr' we penalize light tasks, so * they get preempted easier. That is, if 'se' < 'curr' then * the resulting gran will be larger, therefore penalizing the * lighter, if otoh 'se' > 'curr' then the resulting gran will * be smaller, again penalizing the lighter task. * * This is especially important for buddies when the leftmost * task is higher priority than the buddy. */ if (unlikely(se->load.weight != NICE_0_LOAD)) gran = calc_delta_fair(gran, se); } else { if (unlikely(curr->load.weight != NICE_0_LOAD)) gran = calc_delta_fair(gran, curr); } return gran; } /* * Should 'se' preempt 'curr'. * * |s1 * |s2 * |s3 * g * |<--->|c * * w(c, s1) = -1 * w(c, s2) = 0 * w(c, s3) = 1 * */ static int wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) { s64 gran, vdiff = curr->vruntime - se->vruntime; if (vdiff <= 0) return -1; gran = wakeup_gran(curr, se); if (vdiff > gran) return 1; return 0; } static void set_last_buddy(struct sched_entity *se) { if (likely(task_of(se)->policy != SCHED_IDLE)) { for_each_sched_entity(se) cfs_rq_of(se)->last = se; } } static void set_next_buddy(struct sched_entity *se) { if (likely(task_of(se)->policy != SCHED_IDLE)) { for_each_sched_entity(se) cfs_rq_of(se)->next = se; } } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync) { struct task_struct *curr = rq->curr; struct sched_entity *se = &curr->se, *pse = &p->se; struct cfs_rq *cfs_rq = task_cfs_rq(curr); update_curr(cfs_rq); if (unlikely(rt_prio(p->prio))) { resched_task(curr); return; } if (unlikely(p->sched_class != &fair_sched_class)) return; if (unlikely(se == pse)) return; /* * Only set the backward buddy when the current task is still on the * rq. This can happen when a wakeup gets interleaved with schedule on * the ->pre_schedule() or idle_balance() point, either of which can * drop the rq lock. * * Also, during early boot the idle thread is in the fair class, for * obvious reasons its a bad idea to schedule back to the idle thread. */ if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle)) set_last_buddy(se); set_next_buddy(pse); /* * We can come here with TIF_NEED_RESCHED already set from new task * wake up path. */ if (test_tsk_need_resched(curr)) return; /* * Batch and idle tasks do not preempt (their preemption is driven by * the tick): */ if (unlikely(p->policy != SCHED_NORMAL)) return; /* Idle tasks are by definition preempted by everybody. */ if (unlikely(curr->policy == SCHED_IDLE)) { resched_task(curr); return; } if (!sched_feat(WAKEUP_PREEMPT)) return; if (sched_feat(WAKEUP_OVERLAP) && (sync || (se->avg_overlap < sysctl_sched_migration_cost && pse->avg_overlap < sysctl_sched_migration_cost))) { resched_task(curr); return; } find_matching_se(&se, &pse); while (se) { BUG_ON(!pse); if (wakeup_preempt_entity(se, pse) == 1) { resched_task(curr); break; } se = parent_entity(se); pse = parent_entity(pse); } } 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); /* * If se was a buddy, clear it so that it will have to earn * the favour again. */ __clear_buddies(cfs_rq, se); set_next_entity(cfs_rq, se); 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 list_head *next) { struct task_struct *p = NULL; struct sched_entity *se; if (next == &cfs_rq->tasks) return NULL; se = list_entry(next, struct sched_entity, group_node); p = task_of(se); cfs_rq->balance_iterator = next->next; return p; } static struct task_struct *load_balance_start_fair(void *arg) { struct cfs_rq *cfs_rq = arg; return __load_balance_iterator(cfs_rq, cfs_rq->tasks.next); } static struct task_struct *load_balance_next_fair(void *arg) { struct cfs_rq *cfs_rq = arg; return __load_balance_iterator(cfs_rq, cfs_rq->balance_iterator); } 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 *cfs_rq) { struct rq_iterator cfs_rq_iterator; cfs_rq_iterator.start = load_balance_start_fair; cfs_rq_iterator.next = load_balance_next_fair; cfs_rq_iterator.arg = cfs_rq; return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd, idle, all_pinned, this_best_prio, &cfs_rq_iterator); } #ifdef CONFIG_FAIR_GROUP_SCHED 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) { long rem_load_move = max_load_move; int busiest_cpu = cpu_of(busiest); struct task_group *tg; rcu_read_lock(); update_h_load(busiest_cpu); list_for_each_entry_rcu(tg, &task_groups, list) { struct cfs_rq *busiest_cfs_rq = tg->cfs_rq[busiest_cpu]; unsigned long busiest_h_load = busiest_cfs_rq->h_load; unsigned long busiest_weight = busiest_cfs_rq->load.weight; u64 rem_load, moved_load; /* * empty group */ if (!busiest_cfs_rq->task_weight) continue; rem_load = (u64)rem_load_move * busiest_weight; rem_load = div_u64(rem_load, busiest_h_load + 1); moved_load = __load_balance_fair(this_rq, this_cpu, busiest, rem_load, sd, idle, all_pinned, this_best_prio, tg->cfs_rq[busiest_cpu]); if (!moved_load) continue; moved_load *= busiest_h_load; moved_load = div_u64(moved_load, busiest_weight + 1); rem_load_move -= moved_load; if (rem_load_move < 0) break; } rcu_read_unlock(); return max_load_move - rem_load_move; } #else 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) { return __load_balance_fair(this_rq, this_cpu, busiest, max_load_move, sd, idle, all_pinned, this_best_prio, &busiest->cfs); } #endif 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 /* CONFIG_SMP */ /* * 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); } } /* * 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); resched_task(rq->curr); } enqueue_task_fair(rq, p, 0); } /* * 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, 0); } /* * 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, 0); } /* 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); } #ifdef CONFIG_FAIR_GROUP_SCHED static void moved_group_fair(struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(p); update_curr(cfs_rq); place_entity(cfs_rq, &p->se, 1); } #endif /* * 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, .check_preempt_curr = check_preempt_wakeup, .pick_next_task = pick_next_task_fair, .put_prev_task = put_prev_task_fair, #ifdef CONFIG_SMP .select_task_rq = select_task_rq_fair, .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_FAIR_GROUP_SCHED .moved_group = moved_group_fair, #endif }; #ifdef CONFIG_SCHED_DEBUG static void print_cfs_stats(struct seq_file *m, int cpu) { struct cfs_rq *cfs_rq; rcu_read_lock(); for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) print_cfs_rq(m, cpu, cfs_rq); rcu_read_unlock(); } #endif