diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched_fair.c | 1131 |
1 files changed, 1131 insertions, 0 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c new file mode 100644 index 00000000000..6971db0a716 --- /dev/null +++ b/kernel/sched_fair.c @@ -0,0 +1,1131 @@ +/* + * 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 |