/* * 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> */ /* * Preemption granularity: * (default: 2 msec, units: nanoseconds) * * NOTE: this granularity value is not the same as the concept of * 'timeslice length' - timeslices in CFS will typically be somewhat * larger than this value. (to see the precise effective timeslice * length of your workload, run vmstat and monitor the context-switches * field) * * On SMP systems the value of this is multiplied by the log2 of the * number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way * systems, 4x on 8-way systems, 5x on 16-way systems, etc.) */ unsigned int sysctl_sched_granularity __read_mostly = 2000000000ULL/HZ; /* * SCHED_BATCH wake-up granularity. * (default: 10 msec, 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 __read_mostly = 10000000000ULL/HZ; /* * SCHED_OTHER wake-up granularity. * (default: 1 msec, 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 __read_mostly = 1000000000ULL/HZ; unsigned int sysctl_sched_stat_granularity __read_mostly; /* * Initialized in sched_init_granularity(): */ unsigned int sysctl_sched_runtime_limit __read_mostly; /* * Debugging: various feature bits */ enum { SCHED_FEAT_FAIR_SLEEPERS = 1, SCHED_FEAT_SLEEPER_AVG = 2, SCHED_FEAT_SLEEPER_LOAD_AVG = 4, SCHED_FEAT_PRECISE_CPU_LOAD = 8, SCHED_FEAT_START_DEBIT = 16, SCHED_FEAT_SKIP_INITIAL = 32, }; unsigned int sysctl_sched_features __read_mostly = SCHED_FEAT_FAIR_SLEEPERS *1 | SCHED_FEAT_SLEEPER_AVG *1 | SCHED_FEAT_SLEEPER_LOAD_AVG *1 | SCHED_FEAT_PRECISE_CPU_LOAD *1 | SCHED_FEAT_START_DEBIT *1 | SCHED_FEAT_SKIP_INITIAL *0; extern struct sched_class fair_sched_class; /************************************************************** * 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; } /* currently running entity (if any) on this cfs_rq */ static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq) { return cfs_rq->curr; } /* An entity is a task if it doesn't "own" a runqueue */ #define entity_is_task(se) (!se->my_q) static inline void set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { cfs_rq->curr = se; } #else /* CONFIG_FAIR_GROUP_SCHED */ static inline struct rq *rq_of(struct cfs_rq *cfs_rq) { return container_of(cfs_rq, struct rq, cfs); } static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); if (unlikely(rq->curr->sched_class != &fair_sched_class)) return NULL; return &rq->curr->se; } #define entity_is_task(se) 1 static inline void set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { } #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: */ /* * Enqueue an entity into the rb-tree: */ static inline 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 = se->fair_key; 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 - entry->fair_key < 0) { 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); update_load_add(&cfs_rq->load, se->load.weight); cfs_rq->nr_running++; se->on_rq = 1; } static inline 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); update_load_sub(&cfs_rq->load, se->load.weight); cfs_rq->nr_running--; se->on_rq = 0; } 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); } /************************************************************** * Scheduling class statistics methods: */ /* * We rescale the rescheduling granularity of tasks according to their * nice level, but only linearly, not exponentially: */ static long niced_granularity(struct sched_entity *curr, unsigned long granularity) { u64 tmp; /* * Negative nice levels get the same granularity as nice-0: */ if (likely(curr->load.weight >= NICE_0_LOAD)) return granularity; /* * Positive nice level tasks get linearly finer * granularity: */ tmp = curr->load.weight * (u64)granularity; /* * It will always fit into 'long': */ return (long) (tmp >> NICE_0_SHIFT); } static inline void limit_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se) { long limit = sysctl_sched_runtime_limit; /* * Niced tasks have the same history dynamic range as * non-niced tasks: */ if (unlikely(se->wait_runtime > limit)) { se->wait_runtime = limit; schedstat_inc(se, wait_runtime_overruns); schedstat_inc(cfs_rq, wait_runtime_overruns); } if (unlikely(se->wait_runtime < -limit)) { se->wait_runtime = -limit; schedstat_inc(se, wait_runtime_underruns); schedstat_inc(cfs_rq, wait_runtime_underruns); } } static inline void __add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta) { se->wait_runtime += delta; schedstat_add(se, sum_wait_runtime, delta); limit_wait_runtime(cfs_rq, se); } static void add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta) { schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime); __add_wait_runtime(cfs_rq, se, delta); schedstat_add(cfs_rq, wait_runtime, se->wait_runtime); } /* * 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, u64 now) { unsigned long delta, delta_exec, delta_fair; long delta_mine; struct load_weight *lw = &cfs_rq->load; unsigned long load = lw->weight; if (unlikely(!load)) return; delta_exec = curr->delta_exec; #ifdef CONFIG_SCHEDSTATS if (unlikely(delta_exec > curr->exec_max)) curr->exec_max = delta_exec; #endif curr->sum_exec_runtime += delta_exec; cfs_rq->exec_clock += delta_exec; delta_fair = calc_delta_fair(delta_exec, lw); delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw); if (cfs_rq->sleeper_bonus > sysctl_sched_stat_granularity) { delta = calc_delta_mine(cfs_rq->sleeper_bonus, curr->load.weight, lw); if (unlikely(delta > cfs_rq->sleeper_bonus)) delta = cfs_rq->sleeper_bonus; cfs_rq->sleeper_bonus -= delta; delta_mine -= delta; } cfs_rq->fair_clock += delta_fair; /* * We executed delta_exec amount of time on the CPU, * but we were only entitled to delta_mine amount of * time during that period (if nr_running == 1 then * the two values are equal) * [Note: delta_mine - delta_exec is negative]: */ add_wait_runtime(cfs_rq, curr, delta_mine - delta_exec); } static void update_curr(struct cfs_rq *cfs_rq, u64 now) { struct sched_entity *curr = cfs_rq_curr(cfs_rq); 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); curr->delta_exec += delta_exec; if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) { __update_curr(cfs_rq, curr, now); curr->delta_exec = 0; } curr->exec_start = now; } static inline void update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { se->wait_start_fair = cfs_rq->fair_clock; se->wait_start = now; } /* * We calculate fair deltas here, so protect against the random effects * of a multiplication overflow by capping it to the runtime limit: */ #if BITS_PER_LONG == 32 static inline unsigned long calc_weighted(unsigned long delta, unsigned long weight, int shift) { u64 tmp = (u64)delta * weight >> shift; if (unlikely(tmp > sysctl_sched_runtime_limit*2)) return sysctl_sched_runtime_limit*2; return tmp; } #else static inline unsigned long calc_weighted(unsigned long delta, unsigned long weight, int shift) { return delta * weight >> shift; } #endif /* * Task is being enqueued - update stats: */ static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { s64 key; /* * Are we enqueueing a waiting task? (for current tasks * a dequeue/enqueue event is a NOP) */ if (se != cfs_rq_curr(cfs_rq)) update_stats_wait_start(cfs_rq, se, now); /* * Update the key: */ key = cfs_rq->fair_clock; /* * Optimize the common nice 0 case: */ if (likely(se->load.weight == NICE_0_LOAD)) { key -= se->wait_runtime; } else { u64 tmp; if (se->wait_runtime < 0) { tmp = -se->wait_runtime; key += (tmp * se->load.inv_weight) >> (WMULT_SHIFT - NICE_0_SHIFT); } else { tmp = se->wait_runtime; key -= (tmp * se->load.weight) >> NICE_0_SHIFT; } } se->fair_key = key; } /* * Note: must be called with a freshly updated rq->fair_clock. */ static inline void __update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { unsigned long delta_fair = se->delta_fair_run; #ifdef CONFIG_SCHEDSTATS { s64 delta_wait = now - se->wait_start; if (unlikely(delta_wait > se->wait_max)) se->wait_max = delta_wait; } #endif if (unlikely(se->load.weight != NICE_0_LOAD)) delta_fair = calc_weighted(delta_fair, se->load.weight, NICE_0_SHIFT); add_wait_runtime(cfs_rq, se, delta_fair); } static void update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { unsigned long delta_fair; delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit), (u64)(cfs_rq->fair_clock - se->wait_start_fair)); se->delta_fair_run += delta_fair; if (unlikely(abs(se->delta_fair_run) >= sysctl_sched_stat_granularity)) { __update_stats_wait_end(cfs_rq, se, now); se->delta_fair_run = 0; } se->wait_start_fair = 0; se->wait_start = 0; } static inline void update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { update_curr(cfs_rq, now); /* * Mark the end of the wait period if dequeueing a * waiting task: */ if (se != cfs_rq_curr(cfs_rq)) update_stats_wait_end(cfs_rq, se, now); } /* * 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, u64 now) { /* * We are starting a new run period: */ se->exec_start = now; } /* * We are descheduling a task - update its stats: */ static inline void update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { se->exec_start = 0; } /************************************************** * Scheduling class queueing methods: */ static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { unsigned long load = cfs_rq->load.weight, delta_fair; long prev_runtime; if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG) load = rq_of(cfs_rq)->cpu_load[2]; delta_fair = se->delta_fair_sleep; /* * Fix up delta_fair with the effect of us running * during the whole sleep period: */ if (sysctl_sched_features & SCHED_FEAT_SLEEPER_AVG) delta_fair = div64_likely32((u64)delta_fair * load, load + se->load.weight); if (unlikely(se->load.weight != NICE_0_LOAD)) delta_fair = calc_weighted(delta_fair, se->load.weight, NICE_0_SHIFT); prev_runtime = se->wait_runtime; __add_wait_runtime(cfs_rq, se, delta_fair); delta_fair = se->wait_runtime - prev_runtime; /* * Track the amount of bonus we've given to sleepers: */ cfs_rq->sleeper_bonus += delta_fair; schedstat_add(cfs_rq, wait_runtime, se->wait_runtime); } static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { struct task_struct *tsk = task_of(se); unsigned long delta_fair; if ((entity_is_task(se) && tsk->policy == SCHED_BATCH) || !(sysctl_sched_features & SCHED_FEAT_FAIR_SLEEPERS)) return; delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit), (u64)(cfs_rq->fair_clock - se->sleep_start_fair)); se->delta_fair_sleep += delta_fair; if (unlikely(abs(se->delta_fair_sleep) >= sysctl_sched_stat_granularity)) { __enqueue_sleeper(cfs_rq, se, now); se->delta_fair_sleep = 0; } se->sleep_start_fair = 0; #ifdef CONFIG_SCHEDSTATS if (se->sleep_start) { u64 delta = now - se->sleep_start; 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; } if (se->block_start) { u64 delta = now - se->block_start; 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; } #endif } static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup, u64 now) { /* * Update the fair clock. */ update_curr(cfs_rq, now); if (wakeup) enqueue_sleeper(cfs_rq, se, now); update_stats_enqueue(cfs_rq, se, now); __enqueue_entity(cfs_rq, se); } static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep, u64 now) { update_stats_dequeue(cfs_rq, se, now); if (sleep) { se->sleep_start_fair = cfs_rq->fair_clock; #ifdef CONFIG_SCHEDSTATS if (entity_is_task(se)) { struct task_struct *tsk = task_of(se); if (tsk->state & TASK_INTERRUPTIBLE) se->sleep_start = now; if (tsk->state & TASK_UNINTERRUPTIBLE) se->block_start = now; } cfs_rq->wait_runtime -= se->wait_runtime; #endif } __dequeue_entity(cfs_rq, se); } /* * Preempt the current task with a newly woken task if needed: */ static void __check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se, struct sched_entity *curr, unsigned long granularity) { s64 __delta = curr->fair_key - se->fair_key; /* * Take scheduling granularity into account - do not * preempt the current task unless the best task has * a larger than sched_granularity fairness advantage: */ if (__delta > niced_granularity(curr, granularity)) resched_task(rq_of(cfs_rq)->curr); } static inline void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now) { /* * 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. (note, here we rely on pick_next_task() having * done a put_prev_task_fair() shortly before this, which * updated rq->fair_clock - used by update_stats_wait_end()) */ update_stats_wait_end(cfs_rq, se, now); update_stats_curr_start(cfs_rq, se, now); set_cfs_rq_curr(cfs_rq, se); } static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq, u64 now) { struct sched_entity *se = __pick_next_entity(cfs_rq); set_next_entity(cfs_rq, se, now); return se; } static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev, u64 now) { /* * 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, now); update_stats_curr_end(cfs_rq, prev, now); if (prev->on_rq) update_stats_wait_start(cfs_rq, prev, now); set_cfs_rq_curr(cfs_rq, NULL); } static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) { struct rq *rq = rq_of(cfs_rq); struct sched_entity *next; u64 now = __rq_clock(rq); /* * Dequeue and enqueue the task to update its * position within the tree: */ dequeue_entity(cfs_rq, curr, 0, now); enqueue_entity(cfs_rq, curr, 0, now); /* * Reschedule if another task tops the current one. */ next = __pick_next_entity(cfs_rq); if (next == curr) return; __check_preempt_curr_fair(cfs_rq, next, curr, sysctl_sched_granularity); } /************************************************** * 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) { /* A later patch will take group into account */ return &cpu_rq(this_cpu)->cfs; } /* Iterate thr' all leaf cfs_rq's on a runqueue */ #define for_each_leaf_cfs_rq(rq, cfs_rq) \ list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) /* Do the two (enqueued) tasks belong to the same group ? */ static inline int is_same_group(struct task_struct *curr, struct task_struct *p) { if (curr->se.cfs_rq == p->se.cfs_rq) return 1; return 0; } #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 task_struct *curr, struct task_struct *p) { return 1; } #endif /* CONFIG_FAIR_GROUP_SCHED */ /* * 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, u64 now) { 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, now); } } /* * 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, u64 now) { 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, now); /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) break; } } /* * sched_yield() support is very simple - we dequeue and enqueue */ static void yield_task_fair(struct rq *rq, struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(p); u64 now = __rq_clock(rq); /* * Dequeue and enqueue the task to update its * position within the tree: */ dequeue_entity(cfs_rq, &p->se, 0, now); enqueue_entity(cfs_rq, &p->se, 0, now); } /* * Preempt the current task with a newly woken task if needed: */ static void check_preempt_curr_fair(struct rq *rq, struct task_struct *p) { struct task_struct *curr = rq->curr; struct cfs_rq *cfs_rq = task_cfs_rq(curr); unsigned long gran; if (unlikely(rt_prio(p->prio))) { update_curr(cfs_rq, rq_clock(rq)); resched_task(curr); return; } gran = sysctl_sched_wakeup_granularity; /* * Batch tasks prefer throughput over latency: */ if (unlikely(p->policy == SCHED_BATCH)) gran = sysctl_sched_batch_wakeup_granularity; if (is_same_group(curr, p)) __check_preempt_curr_fair(cfs_rq, &p->se, &curr->se, gran); } static struct task_struct *pick_next_task_fair(struct rq *rq, u64 now) { 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, now); cfs_rq = group_cfs_rq(se); } while (cfs_rq); return task_of(se); } /* * Account for a descheduled task: */ static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, u64 now) { 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, now); } } /************************************************** * 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 inline 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 int cfs_rq_best_prio(struct cfs_rq *cfs_rq) { struct sched_entity *curr; struct task_struct *p; if (!cfs_rq->nr_running) return MAX_PRIO; curr = __pick_next_entity(cfs_rq); p = task_of(curr); return p->prio; } static int load_balance_fair(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 cpu_idle_type idle, int *all_pinned, unsigned long *total_load_moved) { struct cfs_rq *busy_cfs_rq; unsigned long load_moved, total_nr_moved = 0, nr_moved; long rem_load_move = max_load_move; 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) { struct cfs_rq *this_cfs_rq; long imbalance; unsigned long maxload; int this_best_prio, best_prio, best_prio_seen = 0; this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu); imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight; /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */ if (imbalance <= 0) continue; /* Don't pull more than imbalance/2 */ imbalance /= 2; maxload = min(rem_load_move, imbalance); this_best_prio = cfs_rq_best_prio(this_cfs_rq); best_prio = cfs_rq_best_prio(busy_cfs_rq); /* * 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. */ if (cfs_rq_curr(busy_cfs_rq) == &busiest->curr->se) best_prio_seen = 1; /* pass busy_cfs_rq argument into * load_balance_[start|next]_fair iterators */ cfs_rq_iterator.arg = busy_cfs_rq; nr_moved = balance_tasks(this_rq, this_cpu, busiest, max_nr_move, maxload, sd, idle, all_pinned, &load_moved, this_best_prio, best_prio, best_prio_seen, &cfs_rq_iterator); total_nr_moved += nr_moved; max_nr_move -= nr_moved; rem_load_move -= load_moved; if (max_nr_move <= 0 || rem_load_move <= 0) break; } *total_load_moved = max_load_move - rem_load_move; return total_nr_moved; } /* * scheduler tick hitting a task of our scheduling class: */ static void task_tick_fair(struct rq *rq, struct task_struct *curr) { 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); } } /* * 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; u64 now = rq_clock(rq); sched_info_queued(p); update_stats_enqueue(cfs_rq, se, now); /* * Child runs first: we let it run before the parent * until it reschedules once. We set up the key so that * it will preempt the parent: */ p->se.fair_key = current->se.fair_key - niced_granularity(&rq->curr->se, sysctl_sched_granularity) - 1; /* * The first wait is dominated by the child-runs-first logic, * so do not credit it with that waiting time yet: */ if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL) p->se.wait_start_fair = 0; /* * The statistical average of wait_runtime is about * -granularity/2, so initialize the task with that: */ if (sysctl_sched_features & SCHED_FEAT_START_DEBIT) p->se.wait_runtime = -(sysctl_sched_granularity / 2); __enqueue_entity(cfs_rq, se); inc_nr_running(p, rq, now); } #ifdef CONFIG_FAIR_GROUP_SCHED /* 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 task_struct *curr = rq->curr; struct sched_entity *se = &curr->se; u64 now = rq_clock(rq); struct cfs_rq *cfs_rq; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); set_next_entity(cfs_rq, se, now); } } #else static void set_curr_task_fair(struct rq *rq) { } #endif /* * All the scheduling class methods: */ struct sched_class fair_sched_class __read_mostly = { .enqueue_task = enqueue_task_fair, .dequeue_task = dequeue_task_fair, .yield_task = yield_task_fair, .check_preempt_curr = check_preempt_curr_fair, .pick_next_task = pick_next_task_fair, .put_prev_task = put_prev_task_fair, .load_balance = load_balance_fair, .set_curr_task = set_curr_task_fair, .task_tick = task_tick_fair, .task_new = task_new_fair, }; #ifdef CONFIG_SCHED_DEBUG void print_cfs_stats(struct seq_file *m, int cpu, u64 now) { struct rq *rq = cpu_rq(cpu); struct cfs_rq *cfs_rq; for_each_leaf_cfs_rq(rq, cfs_rq) print_cfs_rq(m, cpu, cfs_rq, now); } #endif