/* * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) * * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar * * Interactivity improvements by Mike Galbraith * (C) 2007 Mike Galbraith * * Various enhancements by Dmitry Adamushko. * (C) 2007 Dmitry Adamushko * * Group scheduling enhancements by Srivatsa Vaddagiri * Copyright IBM Corporation, 2007 * Author: Srivatsa Vaddagiri * * Scaled math optimizations by Thomas Gleixner * Copyright (C) 2007, Thomas Gleixner * * Adaptive scheduling granularity, math enhancements by Peter Zijlstra * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra */ #include #include #include /* * Targeted preemption latency for CPU-bound tasks: * (default: 6ms * (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 = 6000000ULL; unsigned int normalized_sysctl_sched_latency = 6000000ULL; /* * The initial- and re-scaling of tunables is configurable * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) * * Options are: * SCHED_TUNABLESCALING_NONE - unscaled, always *1 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus */ enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG; /* * Minimal preemption granularity for CPU-bound tasks: * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) */ unsigned int sysctl_sched_min_granularity = 750000ULL; unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; /* * is kept at sysctl_sched_latency / sysctl_sched_min_granularity */ static unsigned int sched_nr_latency = 8; /* * After fork, child runs first. If set to 0 (default) then * parent will (try to) run first. */ unsigned int sysctl_sched_child_runs_first __read_mostly; /* * SCHED_OTHER wake-up granularity. * (default: 1 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 = 1000000UL; unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; /* * The exponential sliding window over which load is averaged for shares * distribution. * (default: 10msec) */ unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; #ifdef CONFIG_CFS_BANDWIDTH /* * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool * each time a cfs_rq requests quota. * * Note: in the case that the slice exceeds the runtime remaining (either due * to consumption or the quota being specified to be smaller than the slice) * we will always only issue the remaining available time. * * default: 5 msec, units: microseconds */ unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; #endif static const 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; } /* An entity is a task if it doesn't "own" a runqueue */ #define entity_is_task(se) (!se->my_q) static inline struct task_struct *task_of(struct sched_entity *se) { #ifdef CONFIG_SCHED_DEBUG WARN_ON_ONCE(!entity_is_task(se)); #endif return container_of(se, struct task_struct, se); } /* 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; } static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { if (!cfs_rq->on_list) { /* * Ensure we either appear before our parent (if already * enqueued) or force our parent to appear after us when it is * enqueued. The fact that we always enqueue bottom-up * reduces this to two cases. */ if (cfs_rq->tg->parent && cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) { list_add_rcu(&cfs_rq->leaf_cfs_rq_list, &rq_of(cfs_rq)->leaf_cfs_rq_list); } else { list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, &rq_of(cfs_rq)->leaf_cfs_rq_list); } cfs_rq->on_list = 1; } } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { if (cfs_rq->on_list) { list_del_rcu(&cfs_rq->leaf_cfs_rq_list); cfs_rq->on_list = 0; } } /* 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 task_struct *task_of(struct sched_entity *se) { return container_of(se, struct task_struct, se); } 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 void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) { } static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) { } #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 */ static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec); /************************************************************** * 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 int entity_before(struct sched_entity *a, struct sched_entity *b) { return (s64)(a->vruntime - b->vruntime) < 0; } 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); #ifndef CONFIG_64BIT smp_wmb(); cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; #endif } /* * 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; 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 (entity_before(se, 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_first_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_next_entity(struct sched_entity *se) { struct rb_node *next = rb_next(&se->run_node); if (!next) return NULL; return rb_entry(next, struct sched_entity, run_node); } #ifdef CONFIG_SCHED_DEBUG 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: */ int sched_proc_update_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); int factor = get_update_sysctl_factor(); if (ret || !write) return ret; sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, sysctl_sched_min_granularity); #define WRT_SYSCTL(name) \ (normalized_sysctl_##name = sysctl_##name / (factor)) WRT_SYSCTL(sched_min_granularity); WRT_SYSCTL(sched_latency); WRT_SYSCTL(sched_wakeup_granularity); #undef WRT_SYSCTL 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; struct load_weight lw; cfs_rq = cfs_rq_of(se); load = &cfs_rq->load; if (unlikely(!se->on_rq)) { 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); } static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update); static void update_cfs_shares(struct cfs_rq *cfs_rq); /* * 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->statistics.exec_max, max((u64)delta_exec, curr->statistics.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); #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED cfs_rq->load_unacc_exec_time += delta_exec; #endif } static void update_curr(struct cfs_rq *cfs_rq) { struct sched_entity *curr = cfs_rq->curr; u64 now = rq_of(cfs_rq)->clock_task; 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); trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); cpuacct_charge(curtask, delta_exec); account_group_exec_runtime(curtask, delta_exec); } account_cfs_rq_runtime(cfs_rq, delta_exec); } static inline void update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) { schedstat_set(se->statistics.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->statistics.wait_max, max(se->statistics.wait_max, rq_of(cfs_rq)->clock - se->statistics.wait_start)); schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1); schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum + rq_of(cfs_rq)->clock - se->statistics.wait_start); #ifdef CONFIG_SCHEDSTATS if (entity_is_task(se)) { trace_sched_stat_wait(task_of(se), rq_of(cfs_rq)->clock - se->statistics.wait_start); } #endif schedstat_set(se->statistics.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_task; } /************************************************** * 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++; } 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--; } #ifdef CONFIG_FAIR_GROUP_SCHED /* we need this in update_cfs_load and load-balance functions below */ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); # ifdef CONFIG_SMP static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq, int global_update) { struct task_group *tg = cfs_rq->tg; long load_avg; load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1); load_avg -= cfs_rq->load_contribution; if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) { atomic_add(load_avg, &tg->load_weight); cfs_rq->load_contribution += load_avg; } } static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) { u64 period = sysctl_sched_shares_window; u64 now, delta; unsigned long load = cfs_rq->load.weight; if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq)) return; now = rq_of(cfs_rq)->clock_task; delta = now - cfs_rq->load_stamp; /* truncate load history at 4 idle periods */ if (cfs_rq->load_stamp > cfs_rq->load_last && now - cfs_rq->load_last > 4 * period) { cfs_rq->load_period = 0; cfs_rq->load_avg = 0; delta = period - 1; } cfs_rq->load_stamp = now; cfs_rq->load_unacc_exec_time = 0; cfs_rq->load_period += delta; if (load) { cfs_rq->load_last = now; cfs_rq->load_avg += delta * load; } /* consider updating load contribution on each fold or truncate */ if (global_update || cfs_rq->load_period > period || !cfs_rq->load_period) update_cfs_rq_load_contribution(cfs_rq, global_update); while (cfs_rq->load_period > period) { /* * Inline assembly required to prevent the compiler * optimising this loop into a divmod call. * See __iter_div_u64_rem() for another example of this. */ asm("" : "+rm" (cfs_rq->load_period)); cfs_rq->load_period /= 2; cfs_rq->load_avg /= 2; } if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg) list_del_leaf_cfs_rq(cfs_rq); } static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) { long tg_weight; /* * Use this CPU's actual weight instead of the last load_contribution * to gain a more accurate current total weight. See * update_cfs_rq_load_contribution(). */ tg_weight = atomic_read(&tg->load_weight); tg_weight -= cfs_rq->load_contribution; tg_weight += cfs_rq->load.weight; return tg_weight; } static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) { long tg_weight, load, shares; tg_weight = calc_tg_weight(tg, cfs_rq); load = cfs_rq->load.weight; shares = (tg->shares * load); if (tg_weight) shares /= tg_weight; if (shares < MIN_SHARES) shares = MIN_SHARES; if (shares > tg->shares) shares = tg->shares; return shares; } static void update_entity_shares_tick(struct cfs_rq *cfs_rq) { if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) { update_cfs_load(cfs_rq, 0); update_cfs_shares(cfs_rq); } } # else /* CONFIG_SMP */ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) { } static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) { return tg->shares; } static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq) { } # endif /* CONFIG_SMP */ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, unsigned long weight) { if (se->on_rq) { /* commit outstanding execution time */ if (cfs_rq->curr == se) update_curr(cfs_rq); account_entity_dequeue(cfs_rq, se); } update_load_set(&se->load, weight); if (se->on_rq) account_entity_enqueue(cfs_rq, se); } static void update_cfs_shares(struct cfs_rq *cfs_rq) { struct task_group *tg; struct sched_entity *se; long shares; tg = cfs_rq->tg; se = tg->se[cpu_of(rq_of(cfs_rq))]; if (!se || throttled_hierarchy(cfs_rq)) return; #ifndef CONFIG_SMP if (likely(se->load.weight == tg->shares)) return; #endif shares = calc_cfs_shares(cfs_rq, tg); reweight_entity(cfs_rq_of(se), se, shares); } #else /* CONFIG_FAIR_GROUP_SCHED */ static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) { } static inline void update_cfs_shares(struct cfs_rq *cfs_rq) { } static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq) { } #endif /* CONFIG_FAIR_GROUP_SCHED */ static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) { #ifdef CONFIG_SCHEDSTATS struct task_struct *tsk = NULL; if (entity_is_task(se)) tsk = task_of(se); if (se->statistics.sleep_start) { u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start; if ((s64)delta < 0) delta = 0; if (unlikely(delta > se->statistics.sleep_max)) se->statistics.sleep_max = delta; se->statistics.sleep_start = 0; se->statistics.sum_sleep_runtime += delta; if (tsk) { account_scheduler_latency(tsk, delta >> 10, 1); trace_sched_stat_sleep(tsk, delta); } } if (se->statistics.block_start) { u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start; if ((s64)delta < 0) delta = 0; if (unlikely(delta > se->statistics.block_max)) se->statistics.block_max = delta; se->statistics.block_start = 0; se->statistics.sum_sleep_runtime += delta; if (tsk) { if (tsk->in_iowait) { se->statistics.iowait_sum += delta; se->statistics.iowait_count++; trace_sched_stat_iowait(tsk, 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); /* sleeps up to a single latency don't count. */ if (!initial) { unsigned long thresh = sysctl_sched_latency; /* * Halve their sleep time's effect, to allow * for a gentler effect of sleepers: */ if (sched_feat(GENTLE_FAIR_SLEEPERS)) thresh >>= 1; vruntime -= thresh; } /* ensure we never gain time by being placed backwards. */ vruntime = max_vruntime(se->vruntime, vruntime); se->vruntime = vruntime; } static void check_enqueue_throttle(struct cfs_rq *cfs_rq); static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { /* * Update the normalized vruntime before updating min_vruntime * through callig update_curr(). */ if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) se->vruntime += cfs_rq->min_vruntime; /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); update_cfs_load(cfs_rq, 0); account_entity_enqueue(cfs_rq, se); update_cfs_shares(cfs_rq); if (flags & ENQUEUE_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); se->on_rq = 1; if (cfs_rq->nr_running == 1) { list_add_leaf_cfs_rq(cfs_rq); check_enqueue_throttle(cfs_rq); } } static void __clear_buddies_last(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->last == se) cfs_rq->last = NULL; else break; } } static void __clear_buddies_next(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->next == se) cfs_rq->next = NULL; else break; } } static void __clear_buddies_skip(struct sched_entity *se) { for_each_sched_entity(se) { struct cfs_rq *cfs_rq = cfs_rq_of(se); if (cfs_rq->skip == se) cfs_rq->skip = NULL; else break; } } static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) { if (cfs_rq->last == se) __clear_buddies_last(se); if (cfs_rq->next == se) __clear_buddies_next(se); if (cfs_rq->skip == se) __clear_buddies_skip(se); } static void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); static void dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); update_stats_dequeue(cfs_rq, se); if (flags & DEQUEUE_SLEEP) { #ifdef CONFIG_SCHEDSTATS if (entity_is_task(se)) { struct task_struct *tsk = task_of(se); if (tsk->state & TASK_INTERRUPTIBLE) se->statistics.sleep_start = rq_of(cfs_rq)->clock; if (tsk->state & TASK_UNINTERRUPTIBLE) se->statistics.block_start = rq_of(cfs_rq)->clock; } #endif } clear_buddies(cfs_rq, se); if (se != cfs_rq->curr) __dequeue_entity(cfs_rq, se); se->on_rq = 0; update_cfs_load(cfs_rq, 0); account_entity_dequeue(cfs_rq, se); /* * Normalize the entity after updating the min_vruntime because the * update can refer to the ->curr item and we need to reflect this * movement in our normalized position. */ if (!(flags & DEQUEUE_SLEEP)) se->vruntime -= cfs_rq->min_vruntime; /* return excess runtime on last dequeue */ return_cfs_rq_runtime(cfs_rq); update_min_vruntime(cfs_rq); update_cfs_shares(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; struct sched_entity *se; s64 delta; 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); return; } /* * Ensure that a task that missed wakeup preemption by a * narrow margin doesn't have to wait for a full slice. * This also mitigates buddy induced latencies under load. */ if (delta_exec < sysctl_sched_min_granularity) return; se = __pick_first_entity(cfs_rq); delta = curr->vruntime - se->vruntime; if (delta < 0) return; if (delta > ideal_runtime) resched_task(rq_of(cfs_rq)->curr); } static void set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) { /* 'current' is not kept within the tree. */ if (se->on_rq) { /* * Any task has to be enqueued before it get to execute on * a CPU. So account for the time it spent waiting on the * runqueue. */ update_stats_wait_end(cfs_rq, se); __dequeue_entity(cfs_rq, se); } update_stats_curr_start(cfs_rq, se); cfs_rq->curr = se; #ifdef CONFIG_SCHEDSTATS /* * Track our maximum slice length, if the CPU's load is at * least twice that of our own weight (i.e. dont track it * when there are only lesser-weight tasks around): */ if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { se->statistics.slice_max = max(se->statistics.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); /* * Pick the next process, keeping these things in mind, in this order: * 1) keep things fair between processes/task groups * 2) pick the "next" process, since someone really wants that to run * 3) pick the "last" process, for cache locality * 4) do not run the "skip" process, if something else is available */ static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) { struct sched_entity *se = __pick_first_entity(cfs_rq); struct sched_entity *left = se; /* * Avoid running the skip buddy, if running something else can * be done without getting too unfair. */ if (cfs_rq->skip == se) { struct sched_entity *second = __pick_next_entity(se); if (second && wakeup_preempt_entity(second, left) < 1) se = second; } /* * Prefer last buddy, try to return the CPU to a preempted task. */ if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) se = cfs_rq->last; /* * Someone really wants this to run. If it's not unfair, run it. */ if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) se = cfs_rq->next; clear_buddies(cfs_rq, se); return se; } static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq); 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); /* throttle cfs_rqs exceeding runtime */ check_cfs_rq_runtime(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); /* * Update share accounting for long-running entities. */ update_entity_shares_tick(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) check_preempt_tick(cfs_rq, curr); } /************************************************** * CFS bandwidth control machinery */ #ifdef CONFIG_CFS_BANDWIDTH /* * default period for cfs group bandwidth. * default: 0.1s, units: nanoseconds */ static inline u64 default_cfs_period(void) { return 100000000ULL; } static inline u64 sched_cfs_bandwidth_slice(void) { return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; } /* * Replenish runtime according to assigned quota and update expiration time. * We use sched_clock_cpu directly instead of rq->clock to avoid adding * additional synchronization around rq->lock. * * requires cfs_b->lock */ static void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) { u64 now; if (cfs_b->quota == RUNTIME_INF) return; now = sched_clock_cpu(smp_processor_id()); cfs_b->runtime = cfs_b->quota; cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); } /* returns 0 on failure to allocate runtime */ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct task_group *tg = cfs_rq->tg; struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); u64 amount = 0, min_amount, expires; /* note: this is a positive sum as runtime_remaining <= 0 */ min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; raw_spin_lock(&cfs_b->lock); if (cfs_b->quota == RUNTIME_INF) amount = min_amount; else { /* * If the bandwidth pool has become inactive, then at least one * period must have elapsed since the last consumption. * Refresh the global state and ensure bandwidth timer becomes * active. */ if (!cfs_b->timer_active) { __refill_cfs_bandwidth_runtime(cfs_b); __start_cfs_bandwidth(cfs_b); } if (cfs_b->runtime > 0) { amount = min(cfs_b->runtime, min_amount); cfs_b->runtime -= amount; cfs_b->idle = 0; } } expires = cfs_b->runtime_expires; raw_spin_unlock(&cfs_b->lock); cfs_rq->runtime_remaining += amount; /* * we may have advanced our local expiration to account for allowed * spread between our sched_clock and the one on which runtime was * issued. */ if ((s64)(expires - cfs_rq->runtime_expires) > 0) cfs_rq->runtime_expires = expires; return cfs_rq->runtime_remaining > 0; } /* * Note: This depends on the synchronization provided by sched_clock and the * fact that rq->clock snapshots this value. */ static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); struct rq *rq = rq_of(cfs_rq); /* if the deadline is ahead of our clock, nothing to do */ if (likely((s64)(rq->clock - cfs_rq->runtime_expires) < 0)) return; if (cfs_rq->runtime_remaining < 0) return; /* * If the local deadline has passed we have to consider the * possibility that our sched_clock is 'fast' and the global deadline * has not truly expired. * * Fortunately we can check determine whether this the case by checking * whether the global deadline has advanced. */ if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) { /* extend local deadline, drift is bounded above by 2 ticks */ cfs_rq->runtime_expires += TICK_NSEC; } else { /* global deadline is ahead, expiration has passed */ cfs_rq->runtime_remaining = 0; } } static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) { /* dock delta_exec before expiring quota (as it could span periods) */ cfs_rq->runtime_remaining -= delta_exec; expire_cfs_rq_runtime(cfs_rq); if (likely(cfs_rq->runtime_remaining > 0)) return; /* * if we're unable to extend our runtime we resched so that the active * hierarchy can be throttled */ if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) resched_task(rq_of(cfs_rq)->curr); } static __always_inline void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) { if (!cfs_rq->runtime_enabled) return; __account_cfs_rq_runtime(cfs_rq, delta_exec); } static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) { return cfs_rq->throttled; } /* check whether cfs_rq, or any parent, is throttled */ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) { return cfs_rq->throttle_count; } /* * Ensure that neither of the group entities corresponding to src_cpu or * dest_cpu are members of a throttled hierarchy when performing group * load-balance operations. */ static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu) { struct cfs_rq *src_cfs_rq, *dest_cfs_rq; src_cfs_rq = tg->cfs_rq[src_cpu]; dest_cfs_rq = tg->cfs_rq[dest_cpu]; return throttled_hierarchy(src_cfs_rq) || throttled_hierarchy(dest_cfs_rq); } /* updated child weight may affect parent so we have to do this bottom up */ static int tg_unthrottle_up(struct task_group *tg, void *data) { struct rq *rq = data; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; cfs_rq->throttle_count--; #ifdef CONFIG_SMP if (!cfs_rq->throttle_count) { u64 delta = rq->clock_task - cfs_rq->load_stamp; /* leaving throttled state, advance shares averaging windows */ cfs_rq->load_stamp += delta; cfs_rq->load_last += delta; /* update entity weight now that we are on_rq again */ update_cfs_shares(cfs_rq); } #endif return 0; } static int tg_throttle_down(struct task_group *tg, void *data) { struct rq *rq = data; struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; /* group is entering throttled state, record last load */ if (!cfs_rq->throttle_count) update_cfs_load(cfs_rq, 0); cfs_rq->throttle_count++; return 0; } static void throttle_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); struct sched_entity *se; long task_delta, dequeue = 1; se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; /* account load preceding throttle */ rcu_read_lock(); walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); rcu_read_unlock(); task_delta = cfs_rq->h_nr_running; for_each_sched_entity(se) { struct cfs_rq *qcfs_rq = cfs_rq_of(se); /* throttled entity or throttle-on-deactivate */ if (!se->on_rq) break; if (dequeue) dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); qcfs_rq->h_nr_running -= task_delta; if (qcfs_rq->load.weight) dequeue = 0; } if (!se) rq->nr_running -= task_delta; cfs_rq->throttled = 1; cfs_rq->throttled_timestamp = rq->clock; raw_spin_lock(&cfs_b->lock); list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); if (!cfs_b->timer_active) __start_cfs_bandwidth(cfs_b); raw_spin_unlock(&cfs_b->lock); } static void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) { struct rq *rq = rq_of(cfs_rq); struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); struct sched_entity *se; int enqueue = 1; long task_delta; se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; cfs_rq->throttled = 0; raw_spin_lock(&cfs_b->lock); cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp; list_del_rcu(&cfs_rq->throttled_list); raw_spin_unlock(&cfs_b->lock); cfs_rq->throttled_timestamp = 0; update_rq_clock(rq); /* update hierarchical throttle state */ walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); if (!cfs_rq->load.weight) return; task_delta = cfs_rq->h_nr_running; for_each_sched_entity(se) { if (se->on_rq) enqueue = 0; cfs_rq = cfs_rq_of(se); if (enqueue) enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); cfs_rq->h_nr_running += task_delta; if (cfs_rq_throttled(cfs_rq)) break; } if (!se) rq->nr_running += task_delta; /* determine whether we need to wake up potentially idle cpu */ if (rq->curr == rq->idle && rq->cfs.nr_running) resched_task(rq->curr); } static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, u64 remaining, u64 expires) { struct cfs_rq *cfs_rq; u64 runtime = remaining; rcu_read_lock(); list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, throttled_list) { struct rq *rq = rq_of(cfs_rq); raw_spin_lock(&rq->lock); if (!cfs_rq_throttled(cfs_rq)) goto next; runtime = -cfs_rq->runtime_remaining + 1; if (runtime > remaining) runtime = remaining; remaining -= runtime; cfs_rq->runtime_remaining += runtime; cfs_rq->runtime_expires = expires; /* we check whether we're throttled above */ if (cfs_rq->runtime_remaining > 0) unthrottle_cfs_rq(cfs_rq); next: raw_spin_unlock(&rq->lock); if (!remaining) break; } rcu_read_unlock(); return remaining; } /* * Responsible for refilling a task_group's bandwidth and unthrottling its * cfs_rqs as appropriate. If there has been no activity within the last * period the timer is deactivated until scheduling resumes; cfs_b->idle is * used to track this state. */ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) { u64 runtime, runtime_expires; int idle = 1, throttled; raw_spin_lock(&cfs_b->lock); /* no need to continue the timer with no bandwidth constraint */ if (cfs_b->quota == RUNTIME_INF) goto out_unlock; throttled = !list_empty(&cfs_b->throttled_cfs_rq); /* idle depends on !throttled (for the case of a large deficit) */ idle = cfs_b->idle && !throttled; cfs_b->nr_periods += overrun; /* if we're going inactive then everything else can be deferred */ if (idle) goto out_unlock; __refill_cfs_bandwidth_runtime(cfs_b); if (!throttled) { /* mark as potentially idle for the upcoming period */ cfs_b->idle = 1; goto out_unlock; } /* account preceding periods in which throttling occurred */ cfs_b->nr_throttled += overrun; /* * There are throttled entities so we must first use the new bandwidth * to unthrottle them before making it generally available. This * ensures that all existing debts will be paid before a new cfs_rq is * allowed to run. */ runtime = cfs_b->runtime; runtime_expires = cfs_b->runtime_expires; cfs_b->runtime = 0; /* * This check is repeated as we are holding onto the new bandwidth * while we unthrottle. This can potentially race with an unthrottled * group trying to acquire new bandwidth from the global pool. */ while (throttled && runtime > 0) { raw_spin_unlock(&cfs_b->lock); /* we can't nest cfs_b->lock while distributing bandwidth */ runtime = distribute_cfs_runtime(cfs_b, runtime, runtime_expires); raw_spin_lock(&cfs_b->lock); throttled = !list_empty(&cfs_b->throttled_cfs_rq); } /* return (any) remaining runtime */ cfs_b->runtime = runtime; /* * While we are ensured activity in the period following an * unthrottle, this also covers the case in which the new bandwidth is * insufficient to cover the existing bandwidth deficit. (Forcing the * timer to remain active while there are any throttled entities.) */ cfs_b->idle = 0; out_unlock: if (idle) cfs_b->timer_active = 0; raw_spin_unlock(&cfs_b->lock); return idle; } /* a cfs_rq won't donate quota below this amount */ static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; /* minimum remaining period time to redistribute slack quota */ static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; /* how long we wait to gather additional slack before distributing */ static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; /* are we near the end of the current quota period? */ static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) { struct hrtimer *refresh_timer = &cfs_b->period_timer; u64 remaining; /* if the call-back is running a quota refresh is already occurring */ if (hrtimer_callback_running(refresh_timer)) return 1; /* is a quota refresh about to occur? */ remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); if (remaining < min_expire) return 1; return 0; } static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) { u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; /* if there's a quota refresh soon don't bother with slack */ if (runtime_refresh_within(cfs_b, min_left)) return; start_bandwidth_timer(&cfs_b->slack_timer, ns_to_ktime(cfs_bandwidth_slack_period)); } /* we know any runtime found here is valid as update_curr() precedes return */ static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) { struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; if (slack_runtime <= 0) return; raw_spin_lock(&cfs_b->lock); if (cfs_b->quota != RUNTIME_INF && cfs_rq->runtime_expires == cfs_b->runtime_expires) { cfs_b->runtime += slack_runtime; /* we are under rq->lock, defer unthrottling using a timer */ if (cfs_b->runtime > sched_cfs_bandwidth_slice() && !list_empty(&cfs_b->throttled_cfs_rq)) start_cfs_slack_bandwidth(cfs_b); } raw_spin_unlock(&cfs_b->lock); /* even if it's not valid for return we don't want to try again */ cfs_rq->runtime_remaining -= slack_runtime; } static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) { if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) return; __return_cfs_rq_runtime(cfs_rq); } /* * This is done with a timer (instead of inline with bandwidth return) since * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. */ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) { u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); u64 expires; /* confirm we're still not at a refresh boundary */ if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) return; raw_spin_lock(&cfs_b->lock); if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) { runtime = cfs_b->runtime; cfs_b->runtime = 0; } expires = cfs_b->runtime_expires; raw_spin_unlock(&cfs_b->lock); if (!runtime) return; runtime = distribute_cfs_runtime(cfs_b, runtime, expires); raw_spin_lock(&cfs_b->lock); if (expires == cfs_b->runtime_expires) cfs_b->runtime = runtime; raw_spin_unlock(&cfs_b->lock); } /* * When a group wakes up we want to make sure that its quota is not already * expired/exceeded, otherwise it may be allowed to steal additional ticks of * runtime as update_curr() throttling can not not trigger until it's on-rq. */ static void check_enqueue_throttle(struct cfs_rq *cfs_rq) { /* an active group must be handled by the update_curr()->put() path */ if (!cfs_rq->runtime_enabled || cfs_rq->curr) return; /* ensure the group is not already throttled */ if (cfs_rq_throttled(cfs_rq)) return; /* update runtime allocation */ account_cfs_rq_runtime(cfs_rq, 0); if (cfs_rq->runtime_remaining <= 0) throttle_cfs_rq(cfs_rq); } /* conditionally throttle active cfs_rq's from put_prev_entity() */ static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) return; /* * it's possible for a throttled entity to be forced into a running * state (e.g. set_curr_task), in this case we're finished. */ if (cfs_rq_throttled(cfs_rq)) return; throttle_cfs_rq(cfs_rq); } #else static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) {} static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} static void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) { return 0; } static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) { return 0; } static inline int throttled_lb_pair(struct task_group *tg, int src_cpu, int dest_cpu) { return 0; } #endif /************************************************** * 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 flags) { 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, flags); /* * end evaluation on encountering a throttled cfs_rq * * note: in the case of encountering a throttled cfs_rq we will * post the final h_nr_running increment below. */ if (cfs_rq_throttled(cfs_rq)) break; cfs_rq->h_nr_running++; flags = ENQUEUE_WAKEUP; } for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); cfs_rq->h_nr_running++; if (cfs_rq_throttled(cfs_rq)) break; update_cfs_load(cfs_rq, 0); update_cfs_shares(cfs_rq); } if (!se) inc_nr_running(rq); hrtick_update(rq); } static void set_next_buddy(struct sched_entity *se); /* * 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 flags) { struct cfs_rq *cfs_rq; struct sched_entity *se = &p->se; int task_sleep = flags & DEQUEUE_SLEEP; for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); dequeue_entity(cfs_rq, se, flags); /* * end evaluation on encountering a throttled cfs_rq * * note: in the case of encountering a throttled cfs_rq we will * post the final h_nr_running decrement below. */ if (cfs_rq_throttled(cfs_rq)) break; cfs_rq->h_nr_running--; /* Don't dequeue parent if it has other entities besides us */ if (cfs_rq->load.weight) { /* * Bias pick_next to pick a task from this cfs_rq, as * p is sleeping when it is within its sched_slice. */ if (task_sleep && parent_entity(se)) set_next_buddy(parent_entity(se)); /* avoid re-evaluating load for this entity */ se = parent_entity(se); break; } flags |= DEQUEUE_SLEEP; } for_each_sched_entity(se) { cfs_rq = cfs_rq_of(se); cfs_rq->h_nr_running--; if (cfs_rq_throttled(cfs_rq)) break; update_cfs_load(cfs_rq, 0); update_cfs_shares(cfs_rq); } if (!se) dec_nr_running(rq); hrtick_update(rq); } #ifdef CONFIG_SMP static void task_waking_fair(struct task_struct *p) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); u64 min_vruntime; #ifndef CONFIG_64BIT u64 min_vruntime_copy; do { min_vruntime_copy = cfs_rq->min_vruntime_copy; smp_rmb(); min_vruntime = cfs_rq->min_vruntime; } while (min_vruntime != min_vruntime_copy); #else min_vruntime = cfs_rq->min_vruntime; #endif se->vruntime -= min_vruntime; } #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. * * Calculate the effective load difference if @wl is added (subtracted) to @tg * on this @cpu and results in a total addition (subtraction) of @wg to the * total group weight. * * Given a runqueue weight distribution (rw_i) we can compute a shares * distribution (s_i) using: * * s_i = rw_i / \Sum rw_j (1) * * Suppose we have 4 CPUs and our @tg is a direct child of the root group and * has 7 equal weight tasks, distributed as below (rw_i), with the resulting * shares distribution (s_i): * * rw_i = { 2, 4, 1, 0 } * s_i = { 2/7, 4/7, 1/7, 0 } * * As per wake_affine() we're interested in the load of two CPUs (the CPU the * task used to run on and the CPU the waker is running on), we need to * compute the effect of waking a task on either CPU and, in case of a sync * wakeup, compute the effect of the current task going to sleep. * * So for a change of @wl to the local @cpu with an overall group weight change * of @wl we can compute the new shares distribution (s'_i) using: * * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) * * Suppose we're interested in CPUs 0 and 1, and want to compute the load * differences in waking a task to CPU 0. The additional task changes the * weight and shares distributions like: * * rw'_i = { 3, 4, 1, 0 } * s'_i = { 3/8, 4/8, 1/8, 0 } * * We can then compute the difference in effective weight by using: * * dw_i = S * (s'_i - s_i) (3) * * Where 'S' is the group weight as seen by its parent. * * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - * 4/7) times the weight of the group. */ static long effective_load(struct task_group *tg, int cpu, long wl, long wg) { struct sched_entity *se = tg->se[cpu]; if (!tg->parent) /* the trivial, non-cgroup case */ return wl; for_each_sched_entity(se) { long w, W; tg = se->my_q->tg; /* * W = @wg + \Sum rw_j */ W = wg + calc_tg_weight(tg, se->my_q); /* * w = rw_i + @wl */ w = se->my_q->load.weight + wl; /* * wl = S * s'_i; see (2) */ if (W > 0 && w < W) wl = (w * tg->shares) / W; else wl = tg->shares; /* * Per the above, wl is the new se->load.weight value; since * those are clipped to [MIN_SHARES, ...) do so now. See * calc_cfs_shares(). */ if (wl < MIN_SHARES) wl = MIN_SHARES; /* * wl = dw_i = S * (s'_i - s_i); see (3) */ wl -= se->load.weight; /* * Recursively apply this logic to all parent groups to compute * the final effective load change on the root group. Since * only the @tg group gets extra weight, all parent groups can * only redistribute existing shares. @wl is the shift in shares * resulting from this level per the above. */ 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 *sd, struct task_struct *p, int sync) { s64 this_load, load; int idx, this_cpu, prev_cpu; unsigned long tl_per_task; struct task_group *tg; unsigned long weight; int balanced; idx = sd->wake_idx; this_cpu = smp_processor_id(); prev_cpu = task_cpu(p); load = source_load(prev_cpu, idx); this_load = target_load(this_cpu, idx); /* * 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; this_load += effective_load(tg, this_cpu, -weight, -weight); load += effective_load(tg, prev_cpu, 0, -weight); } tg = task_group(p); weight = p->se.load.weight; /* * In low-load situations, where prev_cpu is idle and this_cpu is idle * due to the sync cause above having dropped this_load to 0, we'll * always have an imbalance, but there's really nothing you can do * about that, so that's good too. * * Otherwise check if either cpus are near enough in load to allow this * task to be woken on this_cpu. */ if (this_load > 0) { s64 this_eff_load, prev_eff_load; this_eff_load = 100; this_eff_load *= power_of(prev_cpu); this_eff_load *= this_load + effective_load(tg, this_cpu, weight, weight); prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; prev_eff_load *= power_of(this_cpu); prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); balanced = this_eff_load <= prev_eff_load; } else balanced = true; /* * 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.statistics.nr_wakeups_affine_attempts); tl_per_task = cpu_avg_load_per_task(this_cpu); if (balanced || (this_load <= load && this_load + 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(sd, ttwu_move_affine); schedstat_inc(p, se.statistics.nr_wakeups_affine); return 1; } return 0; } /* * find_idlest_group finds and returns the least busy CPU group within the * domain. */ static struct sched_group * find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu, int load_idx) { struct sched_group *idlest = NULL, *group = sd->groups; unsigned long min_load = ULONG_MAX, this_load = 0; int imbalance = 100 + (sd->imbalance_pct-100)/2; do { unsigned long load, avg_load; int local_group; int i; /* Skip over this group if it has no CPUs allowed */ if (!cpumask_intersects(sched_group_cpus(group), tsk_cpus_allowed(p))) continue; local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(group)); /* Tally up the load of all CPUs in the group */ avg_load = 0; for_each_cpu(i, sched_group_cpus(group)) { /* Bias balancing toward cpus of our domain */ if (local_group) load = source_load(i, load_idx); else load = target_load(i, load_idx); avg_load += load; } /* Adjust by relative CPU power of the group */ avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power; if (local_group) { this_load = avg_load; } else if (avg_load < min_load) { min_load = avg_load; idlest = group; } } while (group = group->next, group != sd->groups); if (!idlest || 100*this_load < imbalance*min_load) return NULL; return idlest; } /* * find_idlest_cpu - find the idlest cpu among the cpus in group. */ static int find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { unsigned long load, min_load = ULONG_MAX; int idlest = -1; int i; /* Traverse only the allowed CPUs */ for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { load = weighted_cpuload(i); if (load < min_load || (load == min_load && i == this_cpu)) { min_load = load; idlest = i; } } return idlest; } /* * Try and locate an idle CPU in the sched_domain. */ static int select_idle_sibling(struct task_struct *p, int target) { int cpu = smp_processor_id(); int prev_cpu = task_cpu(p); struct sched_domain *sd; struct sched_group *sg; int i, smt = 0; /* * If the task is going to be woken-up on this cpu and if it is * already idle, then it is the right target. */ if (target == cpu && idle_cpu(cpu)) return cpu; /* * If the task is going to be woken-up on the cpu where it previously * ran and if it is currently idle, then it the right target. */ if (target == prev_cpu && idle_cpu(prev_cpu)) return prev_cpu; /* * Otherwise, iterate the domains and find an elegible idle cpu. */ rcu_read_lock(); again: for_each_domain(target, sd) { if (!smt && (sd->flags & SD_SHARE_CPUPOWER)) continue; if (smt && !(sd->flags & SD_SHARE_CPUPOWER)) break; if (!(sd->flags & SD_SHARE_PKG_RESOURCES)) break; sg = sd->groups; do { if (!cpumask_intersects(sched_group_cpus(sg), tsk_cpus_allowed(p))) goto next; for_each_cpu(i, sched_group_cpus(sg)) { if (!idle_cpu(i)) goto next; } target = cpumask_first_and(sched_group_cpus(sg), tsk_cpus_allowed(p)); goto done; next: sg = sg->next; } while (sg != sd->groups); } if (!smt) { smt = 1; goto again; } done: rcu_read_unlock(); return target; } /* * sched_balance_self: balance the current task (running on cpu) in domains * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and * SD_BALANCE_EXEC. * * Balance, ie. select the least loaded group. * * Returns the target CPU number, or the same CPU if no balancing is needed. * * preempt must be disabled. */ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) { struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; int cpu = smp_processor_id(); int prev_cpu = task_cpu(p); int new_cpu = cpu; int want_affine = 0; int want_sd = 1; int sync = wake_flags & WF_SYNC; if (sd_flag & SD_BALANCE_WAKE) { if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) want_affine = 1; new_cpu = prev_cpu; } rcu_read_lock(); for_each_domain(cpu, tmp) { if (!(tmp->flags & SD_LOAD_BALANCE)) continue; /* * If power savings logic is enabled for a domain, see if we * are not overloaded, if so, don't balance wider. */ if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) { unsigned long power = 0; unsigned long nr_running = 0; unsigned long capacity; int i; for_each_cpu(i, sched_domain_span(tmp)) { power += power_of(i); nr_running += cpu_rq(i)->cfs.nr_running; } capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE); if (tmp->flags & SD_POWERSAVINGS_BALANCE) nr_running /= 2; if (nr_running < capacity) want_sd = 0; } /* * If both cpu and prev_cpu are part of this domain, * cpu is a valid SD_WAKE_AFFINE target. */ if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { affine_sd = tmp; want_affine = 0; } if (!want_sd && !want_affine) break; if (!(tmp->flags & sd_flag)) continue; if (want_sd) sd = tmp; } if (affine_sd) { if (cpu == prev_cpu || wake_affine(affine_sd, p, sync)) prev_cpu = cpu; new_cpu = select_idle_sibling(p, prev_cpu); goto unlock; } while (sd) { int load_idx = sd->forkexec_idx; struct sched_group *group; int weight; if (!(sd->flags & sd_flag)) { sd = sd->child; continue; } if (sd_flag & SD_BALANCE_WAKE) load_idx = sd->wake_idx; group = find_idlest_group(sd, p, cpu, load_idx); if (!group) { sd = sd->child; continue; } new_cpu = find_idlest_cpu(group, p, cpu); if (new_cpu == -1 || new_cpu == cpu) { /* Now try balancing at a lower domain level of cpu */ sd = sd->child; continue; } /* Now try balancing at a lower domain level of new_cpu */ cpu = new_cpu; weight = sd->span_weight; sd = NULL; for_each_domain(cpu, tmp) { if (weight <= tmp->span_weight) break; if (tmp->flags & sd_flag) sd = tmp; } /* while loop will break here if sd == NULL */ } unlock: rcu_read_unlock(); return new_cpu; } #endif /* CONFIG_SMP */ static unsigned long wakeup_gran(struct sched_entity *curr, struct sched_entity *se) { unsigned long gran = sysctl_sched_wakeup_granularity; /* * Since its curr running now, convert the gran from real-time * to virtual-time in his units. * * 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. */ return calc_delta_fair(gran, se); } /* * 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 (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; for_each_sched_entity(se) cfs_rq_of(se)->last = se; } static void set_next_buddy(struct sched_entity *se) { if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) return; for_each_sched_entity(se) cfs_rq_of(se)->next = se; } static void set_skip_buddy(struct sched_entity *se) { for_each_sched_entity(se) cfs_rq_of(se)->skip = 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 wake_flags) { struct task_struct *curr = rq->curr; struct sched_entity *se = &curr->se, *pse = &p->se; struct cfs_rq *cfs_rq = task_cfs_rq(curr); int scale = cfs_rq->nr_running >= sched_nr_latency; int next_buddy_marked = 0; if (unlikely(se == pse)) return; /* * This is possible from callers such as pull_task(), in which we * unconditionally check_prempt_curr() after an enqueue (which may have * lead to a throttle). This both saves work and prevents false * next-buddy nomination below. */ if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) return; if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { set_next_buddy(pse); next_buddy_marked = 1; } /* * We can come here with TIF_NEED_RESCHED already set from new task * wake up path. * * Note: this also catches the edge-case of curr being in a throttled * group (e.g. via set_curr_task), since update_curr() (in the * enqueue of curr) will have resulted in resched being set. This * prevents us from potentially nominating it as a false LAST_BUDDY * below. */ if (test_tsk_need_resched(curr)) return; /* Idle tasks are by definition preempted by non-idle tasks. */ if (unlikely(curr->policy == SCHED_IDLE) && likely(p->policy != SCHED_IDLE)) goto preempt; /* * Batch and idle tasks do not preempt non-idle tasks (their preemption * is driven by the tick): */ if (unlikely(p->policy != SCHED_NORMAL)) return; find_matching_se(&se, &pse); update_curr(cfs_rq_of(se)); BUG_ON(!pse); if (wakeup_preempt_entity(se, pse) == 1) { /* * Bias pick_next to pick the sched entity that is * triggering this preemption. */ if (!next_buddy_marked) set_next_buddy(pse); goto preempt; } return; preempt: resched_task(curr); /* * 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 it. */ if (unlikely(!se->on_rq || curr == rq->idle)) return; if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) set_last_buddy(se); } 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 (!cfs_rq->nr_running) return NULL; do { se = pick_next_entity(cfs_rq); 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); } } /* * sched_yield() is very simple * * The magic of dealing with the ->skip buddy is in pick_next_entity. */ 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 *se = &curr->se; /* * Are we the only task in the tree? */ if (unlikely(rq->nr_running == 1)) return; clear_buddies(cfs_rq, se); if (curr->policy != SCHED_BATCH) { update_rq_clock(rq); /* * Update run-time statistics of the 'current'. */ update_curr(cfs_rq); } set_skip_buddy(se); } static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) { struct sched_entity *se = &p->se; /* throttled hierarchies are not runnable */ if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) return false; /* Tell the scheduler that we'd really like pse to run next. */ set_next_buddy(se); yield_task_fair(rq); return true; } #ifdef CONFIG_SMP /************************************************** * Fair scheduling class load-balancing methods: */ /* * pull_task - move a task from a remote runqueue to the local runqueue. * Both runqueues must be locked. */ static void pull_task(struct rq *src_rq, struct task_struct *p, struct rq *this_rq, int this_cpu) { deactivate_task(src_rq, p, 0); set_task_cpu(p, this_cpu); activate_task(this_rq, p, 0); check_preempt_curr(this_rq, p, 0); } /* * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? */ static int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu, struct sched_domain *sd, enum cpu_idle_type idle, int *all_pinned) { int tsk_cache_hot = 0; /* * We do not migrate tasks that are: * 1) running (obviously), or * 2) cannot be migrated to this CPU due to cpus_allowed, or * 3) are cache-hot on their current CPU. */ if (!cpumask_test_cpu(this_cpu, tsk_cpus_allowed(p))) { schedstat_inc(p, se.statistics.nr_failed_migrations_affine); return 0; } *all_pinned = 0; if (task_running(rq, p)) { schedstat_inc(p, se.statistics.nr_failed_migrations_running); return 0; } /* * Aggressive migration if: * 1) task is cache cold, or * 2) too many balance attempts have failed. */ tsk_cache_hot = task_hot(p, rq->clock_task, sd); if (!tsk_cache_hot || sd->nr_balance_failed > sd->cache_nice_tries) { #ifdef CONFIG_SCHEDSTATS if (tsk_cache_hot) { schedstat_inc(sd, lb_hot_gained[idle]); schedstat_inc(p, se.statistics.nr_forced_migrations); } #endif return 1; } if (tsk_cache_hot) { schedstat_inc(p, se.statistics.nr_failed_migrations_hot); return 0; } return 1; } /* * move_one_task tries to move exactly one task from busiest to this_rq, as * part of active balancing operations within "domain". * Returns 1 if successful and 0 otherwise. * * Called with both runqueues locked. */ static int move_one_task(struct rq *this_rq, int this_cpu, struct rq *busiest, struct sched_domain *sd, enum cpu_idle_type idle) { struct task_struct *p, *n; struct cfs_rq *cfs_rq; int pinned = 0; for_each_leaf_cfs_rq(busiest, cfs_rq) { list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) { if (throttled_lb_pair(task_group(p), busiest->cpu, this_cpu)) break; if (!can_migrate_task(p, busiest, this_cpu, sd, idle, &pinned)) continue; pull_task(busiest, p, this_rq, this_cpu); /* * Right now, this is only the second place pull_task() * is called, so we can safely collect pull_task() * stats here rather than inside pull_task(). */ schedstat_inc(sd, lb_gained[idle]); return 1; } } return 0; } static unsigned long balance_tasks(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, struct cfs_rq *busiest_cfs_rq) { int loops = 0, pulled = 0; long rem_load_move = max_load_move; struct task_struct *p, *n; if (max_load_move == 0) goto out; list_for_each_entry_safe(p, n, &busiest_cfs_rq->tasks, se.group_node) { if (loops++ > sysctl_sched_nr_migrate) break; if ((p->se.load.weight >> 1) > rem_load_move || !can_migrate_task(p, busiest, this_cpu, sd, idle, all_pinned)) continue; pull_task(busiest, p, this_rq, this_cpu); pulled++; rem_load_move -= p->se.load.weight; #ifdef CONFIG_PREEMPT /* * NEWIDLE balancing is a source of latency, so preemptible * kernels will stop after the first task is pulled to minimize * the critical section. */ if (idle == CPU_NEWLY_IDLE) break; #endif /* * We only want to steal up to the prescribed amount of * weighted load. */ if (rem_load_move <= 0) break; } out: /* * Right now, this is one of only two places pull_task() is called, * so we can safely collect pull_task() stats here rather than * inside pull_task(). */ schedstat_add(sd, lb_gained[idle], pulled); return max_load_move - rem_load_move; } #ifdef CONFIG_FAIR_GROUP_SCHED /* * update tg->load_weight by folding this cpu's load_avg */ static int update_shares_cpu(struct task_group *tg, int cpu) { struct cfs_rq *cfs_rq; unsigned long flags; struct rq *rq; if (!tg->se[cpu]) return 0; rq = cpu_rq(cpu); cfs_rq = tg->cfs_rq[cpu]; raw_spin_lock_irqsave(&rq->lock, flags); update_rq_clock(rq); update_cfs_load(cfs_rq, 1); /* * We need to update shares after updating tg->load_weight in * order to adjust the weight of groups with long running tasks. */ update_cfs_shares(cfs_rq); raw_spin_unlock_irqrestore(&rq->lock, flags); return 0; } static void update_shares(int cpu) { struct cfs_rq *cfs_rq; struct rq *rq = cpu_rq(cpu); rcu_read_lock(); /* * Iterates the task_group tree in a bottom up fashion, see * list_add_leaf_cfs_rq() for details. */ for_each_leaf_cfs_rq(rq, cfs_rq) { /* throttled entities do not contribute to load */ if (throttled_hierarchy(cfs_rq)) continue; update_shares_cpu(cfs_rq->tg, cpu); } rcu_read_unlock(); } /* * Compute the cpu's hierarchical load factor for each task group. * This needs to be done in a top-down fashion because the load of a child * group is a fraction of its parents load. */ static int tg_load_down(struct task_group *tg, void *data) { unsigned long load; long cpu = (long)data; if (!tg->parent) { load = cpu_rq(cpu)->load.weight; } else { load = tg->parent->cfs_rq[cpu]->h_load; load *= tg->se[cpu]->load.weight; load /= tg->parent->cfs_rq[cpu]->load.weight + 1; } tg->cfs_rq[cpu]->h_load = load; return 0; } static void update_h_load(long cpu) { walk_tg_tree(tg_load_down, tg_nop, (void *)cpu); } 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) { long rem_load_move = max_load_move; struct cfs_rq *busiest_cfs_rq; rcu_read_lock(); update_h_load(cpu_of(busiest)); for_each_leaf_cfs_rq(busiest, busiest_cfs_rq) { 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 or part of a throttled hierarchy */ if (!busiest_cfs_rq->task_weight || throttled_lb_pair(busiest_cfs_rq->tg, cpu_of(busiest), this_cpu)) continue; rem_load = (u64)rem_load_move * busiest_weight; rem_load = div_u64(rem_load, busiest_h_load + 1); moved_load = balance_tasks(this_rq, this_cpu, busiest, rem_load, sd, idle, all_pinned, busiest_cfs_rq); 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 inline void update_shares(int cpu) { } 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) { return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd, idle, all_pinned, &busiest->cfs); } #endif /* * move_tasks tries to move up to max_load_move weighted load from busiest to * this_rq, as part of a balancing operation within domain "sd". * Returns 1 if successful and 0 otherwise. * * Called with both runqueues locked. */ static int move_tasks(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) { unsigned long total_load_moved = 0, load_moved; do { load_moved = load_balance_fair(this_rq, this_cpu, busiest, max_load_move - total_load_moved, sd, idle, all_pinned); total_load_moved += load_moved; #ifdef CONFIG_PREEMPT /* * NEWIDLE balancing is a source of latency, so preemptible * kernels will stop after the first task is pulled to minimize * the critical section. */ if (idle == CPU_NEWLY_IDLE && this_rq->nr_running) break; if (raw_spin_is_contended(&this_rq->lock) || raw_spin_is_contended(&busiest->lock)) break; #endif } while (load_moved && max_load_move > total_load_moved); return total_load_moved > 0; } /********** Helpers for find_busiest_group ************************/ /* * sd_lb_stats - Structure to store the statistics of a sched_domain * during load balancing. */ struct sd_lb_stats { struct sched_group *busiest; /* Busiest group in this sd */ struct sched_group *this; /* Local group in this sd */ unsigned long total_load; /* Total load of all groups in sd */ unsigned long total_pwr; /* Total power of all groups in sd */ unsigned long avg_load; /* Average load across all groups in sd */ /** Statistics of this group */ unsigned long this_load; unsigned long this_load_per_task; unsigned long this_nr_running; unsigned long this_has_capacity; unsigned int this_idle_cpus; /* Statistics of the busiest group */ unsigned int busiest_idle_cpus; unsigned long max_load; unsigned long busiest_load_per_task; unsigned long busiest_nr_running; unsigned long busiest_group_capacity; unsigned long busiest_has_capacity; unsigned int busiest_group_weight; int group_imb; /* Is there imbalance in this sd */ #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) int power_savings_balance; /* Is powersave balance needed for this sd */ struct sched_group *group_min; /* Least loaded group in sd */ struct sched_group *group_leader; /* Group which relieves group_min */ unsigned long min_load_per_task; /* load_per_task in group_min */ unsigned long leader_nr_running; /* Nr running of group_leader */ unsigned long min_nr_running; /* Nr running of group_min */ #endif }; /* * sg_lb_stats - stats of a sched_group required for load_balancing */ struct sg_lb_stats { unsigned long avg_load; /*Avg load across the CPUs of the group */ unsigned long group_load; /* Total load over the CPUs of the group */ unsigned long sum_nr_running; /* Nr tasks running in the group */ unsigned long sum_weighted_load; /* Weighted load of group's tasks */ unsigned long group_capacity; unsigned long idle_cpus; unsigned long group_weight; int group_imb; /* Is there an imbalance in the group ? */ int group_has_capacity; /* Is there extra capacity in the group? */ }; /** * group_first_cpu - Returns the first cpu in the cpumask of a sched_group. * @group: The group whose first cpu is to be returned. */ static inline unsigned int group_first_cpu(struct sched_group *group) { return cpumask_first(sched_group_cpus(group)); } /** * get_sd_load_idx - Obtain the load index for a given sched domain. * @sd: The sched_domain whose load_idx is to be obtained. * @idle: The Idle status of the CPU for whose sd load_icx is obtained. */ static inline int get_sd_load_idx(struct sched_domain *sd, enum cpu_idle_type idle) { int load_idx; switch (idle) { case CPU_NOT_IDLE: load_idx = sd->busy_idx; break; case CPU_NEWLY_IDLE: load_idx = sd->newidle_idx; break; default: load_idx = sd->idle_idx; break; } return load_idx; } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) /** * init_sd_power_savings_stats - Initialize power savings statistics for * the given sched_domain, during load balancing. * * @sd: Sched domain whose power-savings statistics are to be initialized. * @sds: Variable containing the statistics for sd. * @idle: Idle status of the CPU at which we're performing load-balancing. */ static inline void init_sd_power_savings_stats(struct sched_domain *sd, struct sd_lb_stats *sds, enum cpu_idle_type idle) { /* * Busy processors will not participate in power savings * balance. */ if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE)) sds->power_savings_balance = 0; else { sds->power_savings_balance = 1; sds->min_nr_running = ULONG_MAX; sds->leader_nr_running = 0; } } /** * update_sd_power_savings_stats - Update the power saving stats for a * sched_domain while performing load balancing. * * @group: sched_group belonging to the sched_domain under consideration. * @sds: Variable containing the statistics of the sched_domain * @local_group: Does group contain the CPU for which we're performing * load balancing ? * @sgs: Variable containing the statistics of the group. */ static inline void update_sd_power_savings_stats(struct sched_group *group, struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs) { if (!sds->power_savings_balance) return; /* * If the local group is idle or completely loaded * no need to do power savings balance at this domain */ if (local_group && (sds->this_nr_running >= sgs->group_capacity || !sds->this_nr_running)) sds->power_savings_balance = 0; /* * If a group is already running at full capacity or idle, * don't include that group in power savings calculations */ if (!sds->power_savings_balance || sgs->sum_nr_running >= sgs->group_capacity || !sgs->sum_nr_running) return; /* * Calculate the group which has the least non-idle load. * This is the group from where we need to pick up the load * for saving power */ if ((sgs->sum_nr_running < sds->min_nr_running) || (sgs->sum_nr_running == sds->min_nr_running && group_first_cpu(group) > group_first_cpu(sds->group_min))) { sds->group_min = group; sds->min_nr_running = sgs->sum_nr_running; sds->min_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; } /* * Calculate the group which is almost near its * capacity but still has some space to pick up some load * from other group and save more power */ if (sgs->sum_nr_running + 1 > sgs->group_capacity) return; if (sgs->sum_nr_running > sds->leader_nr_running || (sgs->sum_nr_running == sds->leader_nr_running && group_first_cpu(group) < group_first_cpu(sds->group_leader))) { sds->group_leader = group; sds->leader_nr_running = sgs->sum_nr_running; } } /** * check_power_save_busiest_group - see if there is potential for some power-savings balance * @sds: Variable containing the statistics of the sched_domain * under consideration. * @this_cpu: Cpu at which we're currently performing load-balancing. * @imbalance: Variable to store the imbalance. * * Description: * Check if we have potential to perform some power-savings balance. * If yes, set the busiest group to be the least loaded group in the * sched_domain, so that it's CPUs can be put to idle. * * Returns 1 if there is potential to perform power-savings balance. * Else returns 0. */ static inline int check_power_save_busiest_group(struct sd_lb_stats *sds, int this_cpu, unsigned long *imbalance) { if (!sds->power_savings_balance) return 0; if (sds->this != sds->group_leader || sds->group_leader == sds->group_min) return 0; *imbalance = sds->min_load_per_task; sds->busiest = sds->group_min; return 1; } #else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */ static inline void init_sd_power_savings_stats(struct sched_domain *sd, struct sd_lb_stats *sds, enum cpu_idle_type idle) { return; } static inline void update_sd_power_savings_stats(struct sched_group *group, struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs) { return; } static inline int check_power_save_busiest_group(struct sd_lb_stats *sds, int this_cpu, unsigned long *imbalance) { return 0; } #endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */ unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu) { return SCHED_POWER_SCALE; } unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu) { return default_scale_freq_power(sd, cpu); } unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu) { unsigned long weight = sd->span_weight; unsigned long smt_gain = sd->smt_gain; smt_gain /= weight; return smt_gain; } unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu) { return default_scale_smt_power(sd, cpu); } unsigned long scale_rt_power(int cpu) { struct rq *rq = cpu_rq(cpu); u64 total, available; total = sched_avg_period() + (rq->clock - rq->age_stamp); if (unlikely(total < rq->rt_avg)) { /* Ensures that power won't end up being negative */ available = 0; } else { available = total - rq->rt_avg; } if (unlikely((s64)total < SCHED_POWER_SCALE)) total = SCHED_POWER_SCALE; total >>= SCHED_POWER_SHIFT; return div_u64(available, total); } static void update_cpu_power(struct sched_domain *sd, int cpu) { unsigned long weight = sd->span_weight; unsigned long power = SCHED_POWER_SCALE; struct sched_group *sdg = sd->groups; if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) { if (sched_feat(ARCH_POWER)) power *= arch_scale_smt_power(sd, cpu); else power *= default_scale_smt_power(sd, cpu); power >>= SCHED_POWER_SHIFT; } sdg->sgp->power_orig = power; if (sched_feat(ARCH_POWER)) power *= arch_scale_freq_power(sd, cpu); else power *= default_scale_freq_power(sd, cpu); power >>= SCHED_POWER_SHIFT; power *= scale_rt_power(cpu); power >>= SCHED_POWER_SHIFT; if (!power) power = 1; cpu_rq(cpu)->cpu_power = power; sdg->sgp->power = power; } static void update_group_power(struct sched_domain *sd, int cpu) { struct sched_domain *child = sd->child; struct sched_group *group, *sdg = sd->groups; unsigned long power; if (!child) { update_cpu_power(sd, cpu); return; } power = 0; group = child->groups; do { power += group->sgp->power; group = group->next; } while (group != child->groups); sdg->sgp->power = power; } /* * Try and fix up capacity for tiny siblings, this is needed when * things like SD_ASYM_PACKING need f_b_g to select another sibling * which on its own isn't powerful enough. * * See update_sd_pick_busiest() and check_asym_packing(). */ static inline int fix_small_capacity(struct sched_domain *sd, struct sched_group *group) { /* * Only siblings can have significantly less than SCHED_POWER_SCALE */ if (!(sd->flags & SD_SHARE_CPUPOWER)) return 0; /* * If ~90% of the cpu_power is still there, we're good. */ if (group->sgp->power * 32 > group->sgp->power_orig * 29) return 1; return 0; } /** * update_sg_lb_stats - Update sched_group's statistics for load balancing. * @sd: The sched_domain whose statistics are to be updated. * @group: sched_group whose statistics are to be updated. * @this_cpu: Cpu for which load balance is currently performed. * @idle: Idle status of this_cpu * @load_idx: Load index of sched_domain of this_cpu for load calc. * @local_group: Does group contain this_cpu. * @cpus: Set of cpus considered for load balancing. * @balance: Should we balance. * @sgs: variable to hold the statistics for this group. */ static inline void update_sg_lb_stats(struct sched_domain *sd, struct sched_group *group, int this_cpu, enum cpu_idle_type idle, int load_idx, int local_group, const struct cpumask *cpus, int *balance, struct sg_lb_stats *sgs) { unsigned long load, max_cpu_load, min_cpu_load, max_nr_running; int i; unsigned int balance_cpu = -1, first_idle_cpu = 0; unsigned long avg_load_per_task = 0; if (local_group) balance_cpu = group_first_cpu(group); /* Tally up the load of all CPUs in the group */ max_cpu_load = 0; min_cpu_load = ~0UL; max_nr_running = 0; for_each_cpu_and(i, sched_group_cpus(group), cpus) { struct rq *rq = cpu_rq(i); /* Bias balancing toward cpus of our domain */ if (local_group) { if (idle_cpu(i) && !first_idle_cpu) { first_idle_cpu = 1; balance_cpu = i; } load = target_load(i, load_idx); } else { load = source_load(i, load_idx); if (load > max_cpu_load) { max_cpu_load = load; max_nr_running = rq->nr_running; } if (min_cpu_load > load) min_cpu_load = load; } sgs->group_load += load; sgs->sum_nr_running += rq->nr_running; sgs->sum_weighted_load += weighted_cpuload(i); if (idle_cpu(i)) sgs->idle_cpus++; } /* * First idle cpu or the first cpu(busiest) in this sched group * is eligible for doing load balancing at this and above * domains. In the newly idle case, we will allow all the cpu's * to do the newly idle load balance. */ if (idle != CPU_NEWLY_IDLE && local_group) { if (balance_cpu != this_cpu) { *balance = 0; return; } update_group_power(sd, this_cpu); } /* Adjust by relative CPU power of the group */ sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power; /* * Consider the group unbalanced when the imbalance is larger * than the average weight of a task. * * APZ: with cgroup the avg task weight can vary wildly and * might not be a suitable number - should we keep a * normalized nr_running number somewhere that negates * the hierarchy? */ if (sgs->sum_nr_running) avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; if ((max_cpu_load - min_cpu_load) >= avg_load_per_task && max_nr_running > 1) sgs->group_imb = 1; sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power, SCHED_POWER_SCALE); if (!sgs->group_capacity) sgs->group_capacity = fix_small_capacity(sd, group); sgs->group_weight = group->group_weight; if (sgs->group_capacity > sgs->sum_nr_running) sgs->group_has_capacity = 1; } /** * update_sd_pick_busiest - return 1 on busiest group * @sd: sched_domain whose statistics are to be checked * @sds: sched_domain statistics * @sg: sched_group candidate to be checked for being the busiest * @sgs: sched_group statistics * @this_cpu: the current cpu * * Determine if @sg is a busier group than the previously selected * busiest group. */ static bool update_sd_pick_busiest(struct sched_domain *sd, struct sd_lb_stats *sds, struct sched_group *sg, struct sg_lb_stats *sgs, int this_cpu) { if (sgs->avg_load <= sds->max_load) return false; if (sgs->sum_nr_running > sgs->group_capacity) return true; if (sgs->group_imb) return true; /* * ASYM_PACKING needs to move all the work to the lowest * numbered CPUs in the group, therefore mark all groups * higher than ourself as busy. */ if ((sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running && this_cpu < group_first_cpu(sg)) { if (!sds->busiest) return true; if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) return true; } return false; } /** * update_sd_lb_stats - Update sched_domain's statistics for load balancing. * @sd: sched_domain whose statistics are to be updated. * @this_cpu: Cpu for which load balance is currently performed. * @idle: Idle status of this_cpu * @cpus: Set of cpus considered for load balancing. * @balance: Should we balance. * @sds: variable to hold the statistics for this sched_domain. */ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu, enum cpu_idle_type idle, const struct cpumask *cpus, int *balance, struct sd_lb_stats *sds) { struct sched_domain *child = sd->child; struct sched_group *sg = sd->groups; struct sg_lb_stats sgs; int load_idx, prefer_sibling = 0; if (child && child->flags & SD_PREFER_SIBLING) prefer_sibling = 1; init_sd_power_savings_stats(sd, sds, idle); load_idx = get_sd_load_idx(sd, idle); do { int local_group; local_group = cpumask_test_cpu(this_cpu, sched_group_cpus(sg)); memset(&sgs, 0, sizeof(sgs)); update_sg_lb_stats(sd, sg, this_cpu, idle, load_idx, local_group, cpus, balance, &sgs); if (local_group && !(*balance)) return; sds->total_load += sgs.group_load; sds->total_pwr += sg->sgp->power; /* * In case the child domain prefers tasks go to siblings * first, lower the sg capacity to one so that we'll try * and move all the excess tasks away. We lower the capacity * of a group only if the local group has the capacity to fit * these excess tasks, i.e. nr_running < group_capacity. The * extra check prevents the case where you always pull from the * heaviest group when it is already under-utilized (possible * with a large weight task outweighs the tasks on the system). */ if (prefer_sibling && !local_group && sds->this_has_capacity) sgs.group_capacity = min(sgs.group_capacity, 1UL); if (local_group) { sds->this_load = sgs.avg_load; sds->this = sg; sds->this_nr_running = sgs.sum_nr_running; sds->this_load_per_task = sgs.sum_weighted_load; sds->this_has_capacity = sgs.group_has_capacity; sds->this_idle_cpus = sgs.idle_cpus; } else if (update_sd_pick_busiest(sd, sds, sg, &sgs, this_cpu)) { sds->max_load = sgs.avg_load; sds->busiest = sg; sds->busiest_nr_running = sgs.sum_nr_running; sds->busiest_idle_cpus = sgs.idle_cpus; sds->busiest_group_capacity = sgs.group_capacity; sds->busiest_load_per_task = sgs.sum_weighted_load; sds->busiest_has_capacity = sgs.group_has_capacity; sds->busiest_group_weight = sgs.group_weight; sds->group_imb = sgs.group_imb; } update_sd_power_savings_stats(sg, sds, local_group, &sgs); sg = sg->next; } while (sg != sd->groups); } int __weak arch_sd_sibling_asym_packing(void) { return 0*SD_ASYM_PACKING; } /** * check_asym_packing - Check to see if the group is packed into the * sched doman. * * This is primarily intended to used at the sibling level. Some * cores like POWER7 prefer to use lower numbered SMT threads. In the * case of POWER7, it can move to lower SMT modes only when higher * threads are idle. When in lower SMT modes, the threads will * perform better since they share less core resources. Hence when we * have idle threads, we want them to be the higher ones. * * This packing function is run on idle threads. It checks to see if * the busiest CPU in this domain (core in the P7 case) has a higher * CPU number than the packing function is being run on. Here we are * assuming lower CPU number will be equivalent to lower a SMT thread * number. * * Returns 1 when packing is required and a task should be moved to * this CPU. The amount of the imbalance is returned in *imbalance. * * @sd: The sched_domain whose packing is to be checked. * @sds: Statistics of the sched_domain which is to be packed * @this_cpu: The cpu at whose sched_domain we're performing load-balance. * @imbalance: returns amount of imbalanced due to packing. */ static int check_asym_packing(struct sched_domain *sd, struct sd_lb_stats *sds, int this_cpu, unsigned long *imbalance) { int busiest_cpu; if (!(sd->flags & SD_ASYM_PACKING)) return 0; if (!sds->busiest) return 0; busiest_cpu = group_first_cpu(sds->busiest); if (this_cpu > busiest_cpu) return 0; *imbalance = DIV_ROUND_CLOSEST(sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE); return 1; } /** * fix_small_imbalance - Calculate the minor imbalance that exists * amongst the groups of a sched_domain, during * load balancing. * @sds: Statistics of the sched_domain whose imbalance is to be calculated. * @this_cpu: The cpu at whose sched_domain we're performing load-balance. * @imbalance: Variable to store the imbalance. */ static inline void fix_small_imbalance(struct sd_lb_stats *sds, int this_cpu, unsigned long *imbalance) { unsigned long tmp, pwr_now = 0, pwr_move = 0; unsigned int imbn = 2; unsigned long scaled_busy_load_per_task; if (sds->this_nr_running) { sds->this_load_per_task /= sds->this_nr_running; if (sds->busiest_load_per_task > sds->this_load_per_task) imbn = 1; } else sds->this_load_per_task = cpu_avg_load_per_task(this_cpu); scaled_busy_load_per_task = sds->busiest_load_per_task * SCHED_POWER_SCALE; scaled_busy_load_per_task /= sds->busiest->sgp->power; if (sds->max_load - sds->this_load + scaled_busy_load_per_task >= (scaled_busy_load_per_task * imbn)) { *imbalance = sds->busiest_load_per_task; return; } /* * OK, we don't have enough imbalance to justify moving tasks, * however we may be able to increase total CPU power used by * moving them. */ pwr_now += sds->busiest->sgp->power * min(sds->busiest_load_per_task, sds->max_load); pwr_now += sds->this->sgp->power * min(sds->this_load_per_task, sds->this_load); pwr_now /= SCHED_POWER_SCALE; /* Amount of load we'd subtract */ tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) / sds->busiest->sgp->power; if (sds->max_load > tmp) pwr_move += sds->busiest->sgp->power * min(sds->busiest_load_per_task, sds->max_load - tmp); /* Amount of load we'd add */ if (sds->max_load * sds->busiest->sgp->power < sds->busiest_load_per_task * SCHED_POWER_SCALE) tmp = (sds->max_load * sds->busiest->sgp->power) / sds->this->sgp->power; else tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) / sds->this->sgp->power; pwr_move += sds->this->sgp->power * min(sds->this_load_per_task, sds->this_load + tmp); pwr_move /= SCHED_POWER_SCALE; /* Move if we gain throughput */ if (pwr_move > pwr_now) *imbalance = sds->busiest_load_per_task; } /** * calculate_imbalance - Calculate the amount of imbalance present within the * groups of a given sched_domain during load balance. * @sds: statistics of the sched_domain whose imbalance is to be calculated. * @this_cpu: Cpu for which currently load balance is being performed. * @imbalance: The variable to store the imbalance. */ static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu, unsigned long *imbalance) { unsigned long max_pull, load_above_capacity = ~0UL; sds->busiest_load_per_task /= sds->busiest_nr_running; if (sds->group_imb) { sds->busiest_load_per_task = min(sds->busiest_load_per_task, sds->avg_load); } /* * In the presence of smp nice balancing, certain scenarios can have * max load less than avg load(as we skip the groups at or below * its cpu_power, while calculating max_load..) */ if (sds->max_load < sds->avg_load) { *imbalance = 0; return fix_small_imbalance(sds, this_cpu, imbalance); } if (!sds->group_imb) { /* * Don't want to pull so many tasks that a group would go idle. */ load_above_capacity = (sds->busiest_nr_running - sds->busiest_group_capacity); load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE); load_above_capacity /= sds->busiest->sgp->power; } /* * We're trying to get all the cpus to the average_load, so we don't * want to push ourselves above the average load, nor do we wish to * reduce the max loaded cpu below the average load. At the same time, * we also don't want to reduce the group load below the group capacity * (so that we can implement power-savings policies etc). Thus we look * for the minimum possible imbalance. * Be careful of negative numbers as they'll appear as very large values * with unsigned longs. */ max_pull = min(sds->max_load - sds->avg_load, load_above_capacity); /* How much load to actually move to equalise the imbalance */ *imbalance = min(max_pull * sds->busiest->sgp->power, (sds->avg_load - sds->this_load) * sds->this->sgp->power) / SCHED_POWER_SCALE; /* * if *imbalance is less than the average load per runnable task * there is no guarantee that any tasks will be moved so we'll have * a think about bumping its value to force at least one task to be * moved */ if (*imbalance < sds->busiest_load_per_task) return fix_small_imbalance(sds, this_cpu, imbalance); } /******* find_busiest_group() helpers end here *********************/ /** * find_busiest_group - Returns the busiest group within the sched_domain * if there is an imbalance. If there isn't an imbalance, and * the user has opted for power-savings, it returns a group whose * CPUs can be put to idle by rebalancing those tasks elsewhere, if * such a group exists. * * Also calculates the amount of weighted load which should be moved * to restore balance. * * @sd: The sched_domain whose busiest group is to be returned. * @this_cpu: The cpu for which load balancing is currently being performed. * @imbalance: Variable which stores amount of weighted load which should * be moved to restore balance/put a group to idle. * @idle: The idle status of this_cpu. * @cpus: The set of CPUs under consideration for load-balancing. * @balance: Pointer to a variable indicating if this_cpu * is the appropriate cpu to perform load balancing at this_level. * * Returns: - the busiest group if imbalance exists. * - If no imbalance and user has opted for power-savings balance, * return the least loaded group whose CPUs can be * put to idle by rebalancing its tasks onto our group. */ static struct sched_group * find_busiest_group(struct sched_domain *sd, int this_cpu, unsigned long *imbalance, enum cpu_idle_type idle, const struct cpumask *cpus, int *balance) { struct sd_lb_stats sds; memset(&sds, 0, sizeof(sds)); /* * Compute the various statistics relavent for load balancing at * this level. */ update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds); /* * this_cpu is not the appropriate cpu to perform load balancing at * this level. */ if (!(*balance)) goto ret; if ((idle == CPU_IDLE || idle == CPU_NEWLY_IDLE) && check_asym_packing(sd, &sds, this_cpu, imbalance)) return sds.busiest; /* There is no busy sibling group to pull tasks from */ if (!sds.busiest || sds.busiest_nr_running == 0) goto out_balanced; sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr; /* * If the busiest group is imbalanced the below checks don't * work because they assumes all things are equal, which typically * isn't true due to cpus_allowed constraints and the like. */ if (sds.group_imb) goto force_balance; /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity && !sds.busiest_has_capacity) goto force_balance; /* * If the local group is more busy than the selected busiest group * don't try and pull any tasks. */ if (sds.this_load >= sds.max_load) goto out_balanced; /* * Don't pull any tasks if this group is already above the domain * average load. */ if (sds.this_load >= sds.avg_load) goto out_balanced; if (idle == CPU_IDLE) { /* * This cpu is idle. If the busiest group load doesn't * have more tasks than the number of available cpu's and * there is no imbalance between this and busiest group * wrt to idle cpu's, it is balanced. */ if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) && sds.busiest_nr_running <= sds.busiest_group_weight) goto out_balanced; } else { /* * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use * imbalance_pct to be conservative. */ if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load) goto out_balanced; } force_balance: /* Looks like there is an imbalance. Compute it */ calculate_imbalance(&sds, this_cpu, imbalance); return sds.busiest; out_balanced: /* * There is no obvious imbalance. But check if we can do some balancing * to save power. */ if (check_power_save_busiest_group(&sds, this_cpu, imbalance)) return sds.busiest; ret: *imbalance = 0; return NULL; } /* * find_busiest_queue - find the busiest runqueue among the cpus in group. */ static struct rq * find_busiest_queue(struct sched_domain *sd, struct sched_group *group, enum cpu_idle_type idle, unsigned long imbalance, const struct cpumask *cpus) { struct rq *busiest = NULL, *rq; unsigned long max_load = 0; int i; for_each_cpu(i, sched_group_cpus(group)) { unsigned long power = power_of(i); unsigned long capacity = DIV_ROUND_CLOSEST(power, SCHED_POWER_SCALE); unsigned long wl; if (!capacity) capacity = fix_small_capacity(sd, group); if (!cpumask_test_cpu(i, cpus)) continue; rq = cpu_rq(i); wl = weighted_cpuload(i); /* * When comparing with imbalance, use weighted_cpuload() * which is not scaled with the cpu power. */ if (capacity && rq->nr_running == 1 && wl > imbalance) continue; /* * For the load comparisons with the other cpu's, consider * the weighted_cpuload() scaled with the cpu power, so that * the load can be moved away from the cpu that is potentially * running at a lower capacity. */ wl = (wl * SCHED_POWER_SCALE) / power; if (wl > max_load) { max_load = wl; busiest = rq; } } return busiest; } /* * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but * so long as it is large enough. */ #define MAX_PINNED_INTERVAL 512 /* Working cpumask for load_balance and load_balance_newidle. */ static DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask); static int need_active_balance(struct sched_domain *sd, int idle, int busiest_cpu, int this_cpu) { if (idle == CPU_NEWLY_IDLE) { /* * ASYM_PACKING needs to force migrate tasks from busy but * higher numbered CPUs in order to pack all tasks in the * lowest numbered CPUs. */ if ((sd->flags & SD_ASYM_PACKING) && busiest_cpu > this_cpu) return 1; /* * The only task running in a non-idle cpu can be moved to this * cpu in an attempt to completely freeup the other CPU * package. * * The package power saving logic comes from * find_busiest_group(). If there are no imbalance, then * f_b_g() will return NULL. However when sched_mc={1,2} then * f_b_g() will select a group from which a running task may be * pulled to this cpu in order to make the other package idle. * If there is no opportunity to make a package idle and if * there are no imbalance, then f_b_g() will return NULL and no * action will be taken in load_balance_newidle(). * * Under normal task pull operation due to imbalance, there * will be more than one task in the source run queue and * move_tasks() will succeed. ld_moved will be true and this * active balance code will not be triggered. */ if (sched_mc_power_savings < POWERSAVINGS_BALANCE_WAKEUP) return 0; } return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); } static int active_load_balance_cpu_stop(void *data); /* * Check this_cpu to ensure it is balanced within domain. Attempt to move * tasks if there is an imbalance. */ static int load_balance(int this_cpu, struct rq *this_rq, struct sched_domain *sd, enum cpu_idle_type idle, int *balance) { int ld_moved, all_pinned = 0, active_balance = 0; struct sched_group *group; unsigned long imbalance; struct rq *busiest; unsigned long flags; struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask); cpumask_copy(cpus, cpu_active_mask); schedstat_inc(sd, lb_count[idle]); redo: group = find_busiest_group(sd, this_cpu, &imbalance, idle, cpus, balance); if (*balance == 0) goto out_balanced; if (!group) { schedstat_inc(sd, lb_nobusyg[idle]); goto out_balanced; } busiest = find_busiest_queue(sd, group, idle, imbalance, cpus); if (!busiest) { schedstat_inc(sd, lb_nobusyq[idle]); goto out_balanced; } BUG_ON(busiest == this_rq); schedstat_add(sd, lb_imbalance[idle], imbalance); ld_moved = 0; if (busiest->nr_running > 1) { /* * Attempt to move tasks. If find_busiest_group has found * an imbalance but busiest->nr_running <= 1, the group is * still unbalanced. ld_moved simply stays zero, so it is * correctly treated as an imbalance. */ all_pinned = 1; local_irq_save(flags); double_rq_lock(this_rq, busiest); ld_moved = move_tasks(this_rq, this_cpu, busiest, imbalance, sd, idle, &all_pinned); double_rq_unlock(this_rq, busiest); local_irq_restore(flags); /* * some other cpu did the load balance for us. */ if (ld_moved && this_cpu != smp_processor_id()) resched_cpu(this_cpu); /* All tasks on this runqueue were pinned by CPU affinity */ if (unlikely(all_pinned)) { cpumask_clear_cpu(cpu_of(busiest), cpus); if (!cpumask_empty(cpus)) goto redo; goto out_balanced; } } if (!ld_moved) { schedstat_inc(sd, lb_failed[idle]); /* * Increment the failure counter only on periodic balance. * We do not want newidle balance, which can be very * frequent, pollute the failure counter causing * excessive cache_hot migrations and active balances. */ if (idle != CPU_NEWLY_IDLE) sd->nr_balance_failed++; if (need_active_balance(sd, idle, cpu_of(busiest), this_cpu)) { raw_spin_lock_irqsave(&busiest->lock, flags); /* don't kick the active_load_balance_cpu_stop, * if the curr task on busiest cpu can't be * moved to this_cpu */ if (!cpumask_test_cpu(this_cpu, tsk_cpus_allowed(busiest->curr))) { raw_spin_unlock_irqrestore(&busiest->lock, flags); all_pinned = 1; goto out_one_pinned; } /* * ->active_balance synchronizes accesses to * ->active_balance_work. Once set, it's cleared * only after active load balance is finished. */ if (!busiest->active_balance) { busiest->active_balance = 1; busiest->push_cpu = this_cpu; active_balance = 1; } raw_spin_unlock_irqrestore(&busiest->lock, flags); if (active_balance) stop_one_cpu_nowait(cpu_of(busiest), active_load_balance_cpu_stop, busiest, &busiest->active_balance_work); /* * We've kicked active balancing, reset the failure * counter. */ sd->nr_balance_failed = sd->cache_nice_tries+1; } } else sd->nr_balance_failed = 0; if (likely(!active_balance)) { /* We were unbalanced, so reset the balancing interval */ sd->balance_interval = sd->min_interval; } else { /* * If we've begun active balancing, start to back off. This * case may not be covered by the all_pinned logic if there * is only 1 task on the busy runqueue (because we don't call * move_tasks). */ if (sd->balance_interval < sd->max_interval) sd->balance_interval *= 2; } goto out; out_balanced: schedstat_inc(sd, lb_balanced[idle]); sd->nr_balance_failed = 0; out_one_pinned: /* tune up the balancing interval */ if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) || (sd->balance_interval < sd->max_interval)) sd->balance_interval *= 2; ld_moved = 0; out: return ld_moved; } /* * idle_balance is called by schedule() if this_cpu is about to become * idle. Attempts to pull tasks from other CPUs. */ static void idle_balance(int this_cpu, struct rq *this_rq) { struct sched_domain *sd; int pulled_task = 0; unsigned long next_balance = jiffies + HZ; this_rq->idle_stamp = this_rq->clock; if (this_rq->avg_idle < sysctl_sched_migration_cost) return; /* * Drop the rq->lock, but keep IRQ/preempt disabled. */ raw_spin_unlock(&this_rq->lock); update_shares(this_cpu); rcu_read_lock(); for_each_domain(this_cpu, sd) { unsigned long interval; int balance = 1; if (!(sd->flags & SD_LOAD_BALANCE)) continue; if (sd->flags & SD_BALANCE_NEWIDLE) { /* If we've pulled tasks over stop searching: */ pulled_task = load_balance(this_cpu, this_rq, sd, CPU_NEWLY_IDLE, &balance); } interval = msecs_to_jiffies(sd->balance_interval); if (time_after(next_balance, sd->last_balance + interval)) next_balance = sd->last_balance + interval; if (pulled_task) { this_rq->idle_stamp = 0; break; } } rcu_read_unlock(); raw_spin_lock(&this_rq->lock); if (pulled_task || time_after(jiffies, this_rq->next_balance)) { /* * We are going idle. next_balance may be set based on * a busy processor. So reset next_balance. */ this_rq->next_balance = next_balance; } } /* * active_load_balance_cpu_stop is run by cpu stopper. It pushes * running tasks off the busiest CPU onto idle CPUs. It requires at * least 1 task to be running on each physical CPU where possible, and * avoids physical / logical imbalances. */ static int active_load_balance_cpu_stop(void *data) { struct rq *busiest_rq = data; int busiest_cpu = cpu_of(busiest_rq); int target_cpu = busiest_rq->push_cpu; struct rq *target_rq = cpu_rq(target_cpu); struct sched_domain *sd; raw_spin_lock_irq(&busiest_rq->lock); /* make sure the requested cpu hasn't gone down in the meantime */ if (unlikely(busiest_cpu != smp_processor_id() || !busiest_rq->active_balance)) goto out_unlock; /* Is there any task to move? */ if (busiest_rq->nr_running <= 1) goto out_unlock; /* * This condition is "impossible", if it occurs * we need to fix it. Originally reported by * Bjorn Helgaas on a 128-cpu setup. */ BUG_ON(busiest_rq == target_rq); /* move a task from busiest_rq to target_rq */ double_lock_balance(busiest_rq, target_rq); /* Search for an sd spanning us and the target CPU. */ rcu_read_lock(); for_each_domain(target_cpu, sd) { if ((sd->flags & SD_LOAD_BALANCE) && cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) break; } if (likely(sd)) { schedstat_inc(sd, alb_count); if (move_one_task(target_rq, target_cpu, busiest_rq, sd, CPU_IDLE)) schedstat_inc(sd, alb_pushed); else schedstat_inc(sd, alb_failed); } rcu_read_unlock(); double_unlock_balance(busiest_rq, target_rq); out_unlock: busiest_rq->active_balance = 0; raw_spin_unlock_irq(&busiest_rq->lock); return 0; } #ifdef CONFIG_NO_HZ /* * idle load balancing details * - One of the idle CPUs nominates itself as idle load_balancer, while * entering idle. * - This idle load balancer CPU will also go into tickless mode when * it is idle, just like all other idle CPUs * - When one of the busy CPUs notice that there may be an idle rebalancing * needed, they will kick the idle load balancer, which then does idle * load balancing for all the idle CPUs. */ static struct { atomic_t load_balancer; atomic_t first_pick_cpu; atomic_t second_pick_cpu; cpumask_var_t idle_cpus_mask; cpumask_var_t grp_idle_mask; unsigned long next_balance; /* in jiffy units */ } nohz ____cacheline_aligned; int get_nohz_load_balancer(void) { return atomic_read(&nohz.load_balancer); } #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT) /** * lowest_flag_domain - Return lowest sched_domain containing flag. * @cpu: The cpu whose lowest level of sched domain is to * be returned. * @flag: The flag to check for the lowest sched_domain * for the given cpu. * * Returns the lowest sched_domain of a cpu which contains the given flag. */ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag) { struct sched_domain *sd; for_each_domain(cpu, sd) if (sd->flags & flag) break; return sd; } /** * for_each_flag_domain - Iterates over sched_domains containing the flag. * @cpu: The cpu whose domains we're iterating over. * @sd: variable holding the value of the power_savings_sd * for cpu. * @flag: The flag to filter the sched_domains to be iterated. * * Iterates over all the scheduler domains for a given cpu that has the 'flag' * set, starting from the lowest sched_domain to the highest. */ #define for_each_flag_domain(cpu, sd, flag) \ for (sd = lowest_flag_domain(cpu, flag); \ (sd && (sd->flags & flag)); sd = sd->parent) /** * is_semi_idle_group - Checks if the given sched_group is semi-idle. * @ilb_group: group to be checked for semi-idleness * * Returns: 1 if the group is semi-idle. 0 otherwise. * * We define a sched_group to be semi idle if it has atleast one idle-CPU * and atleast one non-idle CPU. This helper function checks if the given * sched_group is semi-idle or not. */ static inline int is_semi_idle_group(struct sched_group *ilb_group) { cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask, sched_group_cpus(ilb_group)); /* * A sched_group is semi-idle when it has atleast one busy cpu * and atleast one idle cpu. */ if (cpumask_empty(nohz.grp_idle_mask)) return 0; if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group))) return 0; return 1; } /** * find_new_ilb - Finds the optimum idle load balancer for nomination. * @cpu: The cpu which is nominating a new idle_load_balancer. * * Returns: Returns the id of the idle load balancer if it exists, * Else, returns >= nr_cpu_ids. * * This algorithm picks the idle load balancer such that it belongs to a * semi-idle powersavings sched_domain. The idea is to try and avoid * completely idle packages/cores just for the purpose of idle load balancing * when there are other idle cpu's which are better suited for that job. */ static int find_new_ilb(int cpu) { struct sched_domain *sd; struct sched_group *ilb_group; int ilb = nr_cpu_ids; /* * Have idle load balancer selection from semi-idle packages only * when power-aware load balancing is enabled */ if (!(sched_smt_power_savings || sched_mc_power_savings)) goto out_done; /* * Optimize for the case when we have no idle CPUs or only one * idle CPU. Don't walk the sched_domain hierarchy in such cases */ if (cpumask_weight(nohz.idle_cpus_mask) < 2) goto out_done; rcu_read_lock(); for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) { ilb_group = sd->groups; do { if (is_semi_idle_group(ilb_group)) { ilb = cpumask_first(nohz.grp_idle_mask); goto unlock; } ilb_group = ilb_group->next; } while (ilb_group != sd->groups); } unlock: rcu_read_unlock(); out_done: return ilb; } #else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */ static inline int find_new_ilb(int call_cpu) { return nr_cpu_ids; } #endif /* * Kick a CPU to do the nohz balancing, if it is time for it. We pick the * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle * CPU (if there is one). */ static void nohz_balancer_kick(int cpu) { int ilb_cpu; nohz.next_balance++; ilb_cpu = get_nohz_load_balancer(); if (ilb_cpu >= nr_cpu_ids) { ilb_cpu = cpumask_first(nohz.idle_cpus_mask); if (ilb_cpu >= nr_cpu_ids) return; } if (!cpu_rq(ilb_cpu)->nohz_balance_kick) { cpu_rq(ilb_cpu)->nohz_balance_kick = 1; smp_mb(); /* * Use smp_send_reschedule() instead of resched_cpu(). * This way we generate a sched IPI on the target cpu which * is idle. And the softirq performing nohz idle load balance * will be run before returning from the IPI. */ smp_send_reschedule(ilb_cpu); } return; } /* * This routine will try to nominate the ilb (idle load balancing) * owner among the cpus whose ticks are stopped. ilb owner will do the idle * load balancing on behalf of all those cpus. * * When the ilb owner becomes busy, we will not have new ilb owner until some * idle CPU wakes up and goes back to idle or some busy CPU tries to kick * idle load balancing by kicking one of the idle CPUs. * * Ticks are stopped for the ilb owner as well, with busy CPU kicking this * ilb owner CPU in future (when there is a need for idle load balancing on * behalf of all idle CPUs). */ void select_nohz_load_balancer(int stop_tick) { int cpu = smp_processor_id(); if (stop_tick) { if (!cpu_active(cpu)) { if (atomic_read(&nohz.load_balancer) != cpu) return; /* * If we are going offline and still the leader, * give up! */ if (atomic_cmpxchg(&nohz.load_balancer, cpu, nr_cpu_ids) != cpu) BUG(); return; } cpumask_set_cpu(cpu, nohz.idle_cpus_mask); if (atomic_read(&nohz.first_pick_cpu) == cpu) atomic_cmpxchg(&nohz.first_pick_cpu, cpu, nr_cpu_ids); if (atomic_read(&nohz.second_pick_cpu) == cpu) atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids); if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) { int new_ilb; /* make me the ilb owner */ if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids, cpu) != nr_cpu_ids) return; /* * Check to see if there is a more power-efficient * ilb. */ new_ilb = find_new_ilb(cpu); if (new_ilb < nr_cpu_ids && new_ilb != cpu) { atomic_set(&nohz.load_balancer, nr_cpu_ids); resched_cpu(new_ilb); return; } return; } } else { if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask)) return; cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); if (atomic_read(&nohz.load_balancer) == cpu) if (atomic_cmpxchg(&nohz.load_balancer, cpu, nr_cpu_ids) != cpu) BUG(); } return; } #endif static DEFINE_SPINLOCK(balancing); static unsigned long __read_mostly max_load_balance_interval = HZ/10; /* * Scale the max load_balance interval with the number of CPUs in the system. * This trades load-balance latency on larger machines for less cross talk. */ static void update_max_interval(void) { max_load_balance_interval = HZ*num_online_cpus()/10; } /* * It checks each scheduling domain to see if it is due to be balanced, * and initiates a balancing operation if so. * * Balancing parameters are set up in arch_init_sched_domains. */ static void rebalance_domains(int cpu, enum cpu_idle_type idle) { int balance = 1; struct rq *rq = cpu_rq(cpu); unsigned long interval; struct sched_domain *sd; /* Earliest time when we have to do rebalance again */ unsigned long next_balance = jiffies + 60*HZ; int update_next_balance = 0; int need_serialize; update_shares(cpu); rcu_read_lock(); for_each_domain(cpu, sd) { if (!(sd->flags & SD_LOAD_BALANCE)) continue; interval = sd->balance_interval; if (idle != CPU_IDLE) interval *= sd->busy_factor; /* scale ms to jiffies */ interval = msecs_to_jiffies(interval); interval = clamp(interval, 1UL, max_load_balance_interval); need_serialize = sd->flags & SD_SERIALIZE; if (need_serialize) { if (!spin_trylock(&balancing)) goto out; } if (time_after_eq(jiffies, sd->last_balance + interval)) { if (load_balance(cpu, rq, sd, idle, &balance)) { /* * We've pulled tasks over so either we're no * longer idle. */ idle = CPU_NOT_IDLE; } sd->last_balance = jiffies; } if (need_serialize) spin_unlock(&balancing); out: if (time_after(next_balance, sd->last_balance + interval)) { next_balance = sd->last_balance + interval; update_next_balance = 1; } /* * Stop the load balance at this level. There is another * CPU in our sched group which is doing load balancing more * actively. */ if (!balance) break; } rcu_read_unlock(); /* * next_balance will be updated only when there is a need. * When the cpu is attached to null domain for ex, it will not be * updated. */ if (likely(update_next_balance)) rq->next_balance = next_balance; } #ifdef CONFIG_NO_HZ /* * In CONFIG_NO_HZ case, the idle balance kickee will do the * rebalancing for all the cpus for whom scheduler ticks are stopped. */ static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { struct rq *this_rq = cpu_rq(this_cpu); struct rq *rq; int balance_cpu; if (idle != CPU_IDLE || !this_rq->nohz_balance_kick) return; for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { if (balance_cpu == this_cpu) continue; /* * If this cpu gets work to do, stop the load balancing * work being done for other cpus. Next load * balancing owner will pick it up. */ if (need_resched()) { this_rq->nohz_balance_kick = 0; break; } raw_spin_lock_irq(&this_rq->lock); update_rq_clock(this_rq); update_idle_cpu_load(this_rq); raw_spin_unlock_irq(&this_rq->lock); rebalance_domains(balance_cpu, CPU_IDLE); rq = cpu_rq(balance_cpu); if (time_after(this_rq->next_balance, rq->next_balance)) this_rq->next_balance = rq->next_balance; } nohz.next_balance = this_rq->next_balance; this_rq->nohz_balance_kick = 0; } /* * Current heuristic for kicking the idle load balancer * - first_pick_cpu is the one of the busy CPUs. It will kick * idle load balancer when it has more than one process active. This * eliminates the need for idle load balancing altogether when we have * only one running process in the system (common case). * - If there are more than one busy CPU, idle load balancer may have * to run for active_load_balance to happen (i.e., two busy CPUs are * SMT or core siblings and can run better if they move to different * physical CPUs). So, second_pick_cpu is the second of the busy CPUs * which will kick idle load balancer as soon as it has any load. */ static inline int nohz_kick_needed(struct rq *rq, int cpu) { unsigned long now = jiffies; int ret; int first_pick_cpu, second_pick_cpu; if (time_before(now, nohz.next_balance)) return 0; if (idle_cpu(cpu)) return 0; first_pick_cpu = atomic_read(&nohz.first_pick_cpu); second_pick_cpu = atomic_read(&nohz.second_pick_cpu); if (first_pick_cpu < nr_cpu_ids && first_pick_cpu != cpu && second_pick_cpu < nr_cpu_ids && second_pick_cpu != cpu) return 0; ret = atomic_cmpxchg(&nohz.first_pick_cpu, nr_cpu_ids, cpu); if (ret == nr_cpu_ids || ret == cpu) { atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids); if (rq->nr_running > 1) return 1; } else { ret = atomic_cmpxchg(&nohz.second_pick_cpu, nr_cpu_ids, cpu); if (ret == nr_cpu_ids || ret == cpu) { if (rq->nr_running) return 1; } } return 0; } #else static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { } #endif /* * run_rebalance_domains is triggered when needed from the scheduler tick. * Also triggered for nohz idle balancing (with nohz_balancing_kick set). */ static void run_rebalance_domains(struct softirq_action *h) { int this_cpu = smp_processor_id(); struct rq *this_rq = cpu_rq(this_cpu); enum cpu_idle_type idle = this_rq->idle_balance ? CPU_IDLE : CPU_NOT_IDLE; rebalance_domains(this_cpu, idle); /* * If this cpu has a pending nohz_balance_kick, then do the * balancing on behalf of the other idle cpus whose ticks are * stopped. */ nohz_idle_balance(this_cpu, idle); } static inline int on_null_domain(int cpu) { return !rcu_dereference_sched(cpu_rq(cpu)->sd); } /* * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. */ static inline void trigger_load_balance(struct rq *rq, int cpu) { /* Don't need to rebalance while attached to NULL domain */ if (time_after_eq(jiffies, rq->next_balance) && likely(!on_null_domain(cpu))) raise_softirq(SCHED_SOFTIRQ); #ifdef CONFIG_NO_HZ else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu))) nohz_balancer_kick(cpu); #endif } static void rq_online_fair(struct rq *rq) { update_sysctl(); } static void rq_offline_fair(struct rq *rq) { update_sysctl(); /* Ensure any throttled groups are reachable by pick_next_task */ unthrottle_offline_cfs_rqs(rq); } #else /* CONFIG_SMP */ /* * on UP we do not need to balance between CPUs: */ static inline void idle_balance(int cpu, struct rq *rq) { } #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); } } /* * called on fork with the child task as argument from the parent's context * - child not yet on the tasklist * - preemption disabled */ static void task_fork_fair(struct task_struct *p) { struct cfs_rq *cfs_rq = task_cfs_rq(current); struct sched_entity *se = &p->se, *curr = cfs_rq->curr; int this_cpu = smp_processor_id(); struct rq *rq = this_rq(); unsigned long flags; raw_spin_lock_irqsave(&rq->lock, flags); update_rq_clock(rq); /* * Not only the cpu but also the task_group of the parent might have * been changed after parent->se.parent,cfs_rq were copied to * child->se.parent,cfs_rq. So call __set_task_cpu() to make those * of child point to valid ones. */ rcu_read_lock(); __set_task_cpu(p, this_cpu); rcu_read_unlock(); update_curr(cfs_rq); if (curr) se->vruntime = curr->vruntime; place_entity(cfs_rq, se, 1); if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { /* * 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); } se->vruntime -= cfs_rq->min_vruntime; raw_spin_unlock_irqrestore(&rq->lock, flags); } /* * 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) { if (!p->se.on_rq) return; /* * 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 (rq->curr == p) { if (p->prio > oldprio) resched_task(rq->curr); } else check_preempt_curr(rq, p, 0); } static void switched_from_fair(struct rq *rq, struct task_struct *p) { struct sched_entity *se = &p->se; struct cfs_rq *cfs_rq = cfs_rq_of(se); /* * Ensure the task's vruntime is normalized, so that when its * switched back to the fair class the enqueue_entity(.flags=0) will * do the right thing. * * If it was on_rq, then the dequeue_entity(.flags=0) will already * have normalized the vruntime, if it was !on_rq, then only when * the task is sleeping will it still have non-normalized vruntime. */ if (!se->on_rq && p->state != TASK_RUNNING) { /* * Fix up our vruntime so that the current sleep doesn't * cause 'unlimited' sleep bonus. */ place_entity(cfs_rq, se, 0); se->vruntime -= cfs_rq->min_vruntime; } } /* * We switched to the sched_fair class. */ static void switched_to_fair(struct rq *rq, struct task_struct *p) { if (!p->se.on_rq) return; /* * 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 (rq->curr == p) 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) { struct cfs_rq *cfs_rq = cfs_rq_of(se); set_next_entity(cfs_rq, se); /* ensure bandwidth has been allocated on our new cfs_rq */ account_cfs_rq_runtime(cfs_rq, 0); } } #ifdef CONFIG_FAIR_GROUP_SCHED static void task_move_group_fair(struct task_struct *p, int on_rq) { /* * If the task was not on the rq at the time of this cgroup movement * it must have been asleep, sleeping tasks keep their ->vruntime * absolute on their old rq until wakeup (needed for the fair sleeper * bonus in place_entity()). * * If it was on the rq, we've just 'preempted' it, which does convert * ->vruntime to a relative base. * * Make sure both cases convert their relative position when migrating * to another cgroup's rq. This does somewhat interfere with the * fair sleeper stuff for the first placement, but who cares. */ if (!on_rq) p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; set_task_rq(p, task_cpu(p)); if (!on_rq) p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime; } #endif static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) { struct sched_entity *se = &task->se; unsigned int rr_interval = 0; /* * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise * idle runqueue: */ if (rq->cfs.load.weight) rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); return rr_interval; } /* * 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, .yield_to_task = yield_to_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, .rq_online = rq_online_fair, .rq_offline = rq_offline_fair, .task_waking = task_waking_fair, #endif .set_curr_task = set_curr_task_fair, .task_tick = task_tick_fair, .task_fork = task_fork_fair, .prio_changed = prio_changed_fair, .switched_from = switched_from_fair, .switched_to = switched_to_fair, .get_rr_interval = get_rr_interval_fair, #ifdef CONFIG_FAIR_GROUP_SCHED .task_move_group = task_move_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