1 /* 2 * Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH) 3 * 4 * Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> 5 * 6 * Interactivity improvements by Mike Galbraith 7 * (C) 2007 Mike Galbraith <efault@gmx.de> 8 * 9 * Various enhancements by Dmitry Adamushko. 10 * (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com> 11 * 12 * Group scheduling enhancements by Srivatsa Vaddagiri 13 * Copyright IBM Corporation, 2007 14 * Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> 15 * 16 * Scaled math optimizations by Thomas Gleixner 17 * Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de> 18 * 19 * Adaptive scheduling granularity, math enhancements by Peter Zijlstra 20 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> 21 */ 22 23 #include <linux/latencytop.h> 24 #include <linux/sched.h> 25 #include <linux/cpumask.h> 26 #include <linux/slab.h> 27 #include <linux/profile.h> 28 #include <linux/interrupt.h> 29 #include <linux/mempolicy.h> 30 #include <linux/migrate.h> 31 #include <linux/task_work.h> 32 33 #include <trace/events/sched.h> 34 35 #include "sched.h" 36 37 /* 38 * Targeted preemption latency for CPU-bound tasks: 39 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) 40 * 41 * NOTE: this latency value is not the same as the concept of 42 * 'timeslice length' - timeslices in CFS are of variable length 43 * and have no persistent notion like in traditional, time-slice 44 * based scheduling concepts. 45 * 46 * (to see the precise effective timeslice length of your workload, 47 * run vmstat and monitor the context-switches (cs) field) 48 */ 49 unsigned int sysctl_sched_latency = 6000000ULL; 50 unsigned int normalized_sysctl_sched_latency = 6000000ULL; 51 52 /* 53 * The initial- and re-scaling of tunables is configurable 54 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) 55 * 56 * Options are: 57 * SCHED_TUNABLESCALING_NONE - unscaled, always *1 58 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) 59 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus 60 */ 61 enum sched_tunable_scaling sysctl_sched_tunable_scaling 62 = SCHED_TUNABLESCALING_LOG; 63 64 /* 65 * Minimal preemption granularity for CPU-bound tasks: 66 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) 67 */ 68 unsigned int sysctl_sched_min_granularity = 750000ULL; 69 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; 70 71 /* 72 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity 73 */ 74 static unsigned int sched_nr_latency = 8; 75 76 /* 77 * After fork, child runs first. If set to 0 (default) then 78 * parent will (try to) run first. 79 */ 80 unsigned int sysctl_sched_child_runs_first __read_mostly; 81 82 /* 83 * SCHED_OTHER wake-up granularity. 84 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) 85 * 86 * This option delays the preemption effects of decoupled workloads 87 * and reduces their over-scheduling. Synchronous workloads will still 88 * have immediate wakeup/sleep latencies. 89 */ 90 unsigned int sysctl_sched_wakeup_granularity = 1000000UL; 91 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; 92 93 const_debug unsigned int sysctl_sched_migration_cost = 500000UL; 94 95 /* 96 * The exponential sliding window over which load is averaged for shares 97 * distribution. 98 * (default: 10msec) 99 */ 100 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; 101 102 #ifdef CONFIG_CFS_BANDWIDTH 103 /* 104 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool 105 * each time a cfs_rq requests quota. 106 * 107 * Note: in the case that the slice exceeds the runtime remaining (either due 108 * to consumption or the quota being specified to be smaller than the slice) 109 * we will always only issue the remaining available time. 110 * 111 * default: 5 msec, units: microseconds 112 */ 113 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; 114 #endif 115 116 static inline void update_load_add(struct load_weight *lw, unsigned long inc) 117 { 118 lw->weight += inc; 119 lw->inv_weight = 0; 120 } 121 122 static inline void update_load_sub(struct load_weight *lw, unsigned long dec) 123 { 124 lw->weight -= dec; 125 lw->inv_weight = 0; 126 } 127 128 static inline void update_load_set(struct load_weight *lw, unsigned long w) 129 { 130 lw->weight = w; 131 lw->inv_weight = 0; 132 } 133 134 /* 135 * Increase the granularity value when there are more CPUs, 136 * because with more CPUs the 'effective latency' as visible 137 * to users decreases. But the relationship is not linear, 138 * so pick a second-best guess by going with the log2 of the 139 * number of CPUs. 140 * 141 * This idea comes from the SD scheduler of Con Kolivas: 142 */ 143 static int get_update_sysctl_factor(void) 144 { 145 unsigned int cpus = min_t(int, num_online_cpus(), 8); 146 unsigned int factor; 147 148 switch (sysctl_sched_tunable_scaling) { 149 case SCHED_TUNABLESCALING_NONE: 150 factor = 1; 151 break; 152 case SCHED_TUNABLESCALING_LINEAR: 153 factor = cpus; 154 break; 155 case SCHED_TUNABLESCALING_LOG: 156 default: 157 factor = 1 + ilog2(cpus); 158 break; 159 } 160 161 return factor; 162 } 163 164 static void update_sysctl(void) 165 { 166 unsigned int factor = get_update_sysctl_factor(); 167 168 #define SET_SYSCTL(name) \ 169 (sysctl_##name = (factor) * normalized_sysctl_##name) 170 SET_SYSCTL(sched_min_granularity); 171 SET_SYSCTL(sched_latency); 172 SET_SYSCTL(sched_wakeup_granularity); 173 #undef SET_SYSCTL 174 } 175 176 void sched_init_granularity(void) 177 { 178 update_sysctl(); 179 } 180 181 #define WMULT_CONST (~0U) 182 #define WMULT_SHIFT 32 183 184 static void __update_inv_weight(struct load_weight *lw) 185 { 186 unsigned long w; 187 188 if (likely(lw->inv_weight)) 189 return; 190 191 w = scale_load_down(lw->weight); 192 193 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) 194 lw->inv_weight = 1; 195 else if (unlikely(!w)) 196 lw->inv_weight = WMULT_CONST; 197 else 198 lw->inv_weight = WMULT_CONST / w; 199 } 200 201 /* 202 * delta_exec * weight / lw.weight 203 * OR 204 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT 205 * 206 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case 207 * we're guaranteed shift stays positive because inv_weight is guaranteed to 208 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. 209 * 210 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus 211 * weight/lw.weight <= 1, and therefore our shift will also be positive. 212 */ 213 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) 214 { 215 u64 fact = scale_load_down(weight); 216 int shift = WMULT_SHIFT; 217 218 __update_inv_weight(lw); 219 220 if (unlikely(fact >> 32)) { 221 while (fact >> 32) { 222 fact >>= 1; 223 shift--; 224 } 225 } 226 227 /* hint to use a 32x32->64 mul */ 228 fact = (u64)(u32)fact * lw->inv_weight; 229 230 while (fact >> 32) { 231 fact >>= 1; 232 shift--; 233 } 234 235 return mul_u64_u32_shr(delta_exec, fact, shift); 236 } 237 238 239 const struct sched_class fair_sched_class; 240 241 /************************************************************** 242 * CFS operations on generic schedulable entities: 243 */ 244 245 #ifdef CONFIG_FAIR_GROUP_SCHED 246 247 /* cpu runqueue to which this cfs_rq is attached */ 248 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 249 { 250 return cfs_rq->rq; 251 } 252 253 /* An entity is a task if it doesn't "own" a runqueue */ 254 #define entity_is_task(se) (!se->my_q) 255 256 static inline struct task_struct *task_of(struct sched_entity *se) 257 { 258 #ifdef CONFIG_SCHED_DEBUG 259 WARN_ON_ONCE(!entity_is_task(se)); 260 #endif 261 return container_of(se, struct task_struct, se); 262 } 263 264 /* Walk up scheduling entities hierarchy */ 265 #define for_each_sched_entity(se) \ 266 for (; se; se = se->parent) 267 268 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 269 { 270 return p->se.cfs_rq; 271 } 272 273 /* runqueue on which this entity is (to be) queued */ 274 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 275 { 276 return se->cfs_rq; 277 } 278 279 /* runqueue "owned" by this group */ 280 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 281 { 282 return grp->my_q; 283 } 284 285 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, 286 int force_update); 287 288 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 289 { 290 if (!cfs_rq->on_list) { 291 /* 292 * Ensure we either appear before our parent (if already 293 * enqueued) or force our parent to appear after us when it is 294 * enqueued. The fact that we always enqueue bottom-up 295 * reduces this to two cases. 296 */ 297 if (cfs_rq->tg->parent && 298 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) { 299 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, 300 &rq_of(cfs_rq)->leaf_cfs_rq_list); 301 } else { 302 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, 303 &rq_of(cfs_rq)->leaf_cfs_rq_list); 304 } 305 306 cfs_rq->on_list = 1; 307 /* We should have no load, but we need to update last_decay. */ 308 update_cfs_rq_blocked_load(cfs_rq, 0); 309 } 310 } 311 312 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 313 { 314 if (cfs_rq->on_list) { 315 list_del_rcu(&cfs_rq->leaf_cfs_rq_list); 316 cfs_rq->on_list = 0; 317 } 318 } 319 320 /* Iterate thr' all leaf cfs_rq's on a runqueue */ 321 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 322 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) 323 324 /* Do the two (enqueued) entities belong to the same group ? */ 325 static inline struct cfs_rq * 326 is_same_group(struct sched_entity *se, struct sched_entity *pse) 327 { 328 if (se->cfs_rq == pse->cfs_rq) 329 return se->cfs_rq; 330 331 return NULL; 332 } 333 334 static inline struct sched_entity *parent_entity(struct sched_entity *se) 335 { 336 return se->parent; 337 } 338 339 static void 340 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 341 { 342 int se_depth, pse_depth; 343 344 /* 345 * preemption test can be made between sibling entities who are in the 346 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of 347 * both tasks until we find their ancestors who are siblings of common 348 * parent. 349 */ 350 351 /* First walk up until both entities are at same depth */ 352 se_depth = (*se)->depth; 353 pse_depth = (*pse)->depth; 354 355 while (se_depth > pse_depth) { 356 se_depth--; 357 *se = parent_entity(*se); 358 } 359 360 while (pse_depth > se_depth) { 361 pse_depth--; 362 *pse = parent_entity(*pse); 363 } 364 365 while (!is_same_group(*se, *pse)) { 366 *se = parent_entity(*se); 367 *pse = parent_entity(*pse); 368 } 369 } 370 371 #else /* !CONFIG_FAIR_GROUP_SCHED */ 372 373 static inline struct task_struct *task_of(struct sched_entity *se) 374 { 375 return container_of(se, struct task_struct, se); 376 } 377 378 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 379 { 380 return container_of(cfs_rq, struct rq, cfs); 381 } 382 383 #define entity_is_task(se) 1 384 385 #define for_each_sched_entity(se) \ 386 for (; se; se = NULL) 387 388 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 389 { 390 return &task_rq(p)->cfs; 391 } 392 393 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 394 { 395 struct task_struct *p = task_of(se); 396 struct rq *rq = task_rq(p); 397 398 return &rq->cfs; 399 } 400 401 /* runqueue "owned" by this group */ 402 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 403 { 404 return NULL; 405 } 406 407 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 408 { 409 } 410 411 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 412 { 413 } 414 415 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 416 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) 417 418 static inline struct sched_entity *parent_entity(struct sched_entity *se) 419 { 420 return NULL; 421 } 422 423 static inline void 424 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 425 { 426 } 427 428 #endif /* CONFIG_FAIR_GROUP_SCHED */ 429 430 static __always_inline 431 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); 432 433 /************************************************************** 434 * Scheduling class tree data structure manipulation methods: 435 */ 436 437 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) 438 { 439 s64 delta = (s64)(vruntime - max_vruntime); 440 if (delta > 0) 441 max_vruntime = vruntime; 442 443 return max_vruntime; 444 } 445 446 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) 447 { 448 s64 delta = (s64)(vruntime - min_vruntime); 449 if (delta < 0) 450 min_vruntime = vruntime; 451 452 return min_vruntime; 453 } 454 455 static inline int entity_before(struct sched_entity *a, 456 struct sched_entity *b) 457 { 458 return (s64)(a->vruntime - b->vruntime) < 0; 459 } 460 461 static void update_min_vruntime(struct cfs_rq *cfs_rq) 462 { 463 u64 vruntime = cfs_rq->min_vruntime; 464 465 if (cfs_rq->curr) 466 vruntime = cfs_rq->curr->vruntime; 467 468 if (cfs_rq->rb_leftmost) { 469 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, 470 struct sched_entity, 471 run_node); 472 473 if (!cfs_rq->curr) 474 vruntime = se->vruntime; 475 else 476 vruntime = min_vruntime(vruntime, se->vruntime); 477 } 478 479 /* ensure we never gain time by being placed backwards. */ 480 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); 481 #ifndef CONFIG_64BIT 482 smp_wmb(); 483 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 484 #endif 485 } 486 487 /* 488 * Enqueue an entity into the rb-tree: 489 */ 490 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 491 { 492 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; 493 struct rb_node *parent = NULL; 494 struct sched_entity *entry; 495 int leftmost = 1; 496 497 /* 498 * Find the right place in the rbtree: 499 */ 500 while (*link) { 501 parent = *link; 502 entry = rb_entry(parent, struct sched_entity, run_node); 503 /* 504 * We dont care about collisions. Nodes with 505 * the same key stay together. 506 */ 507 if (entity_before(se, entry)) { 508 link = &parent->rb_left; 509 } else { 510 link = &parent->rb_right; 511 leftmost = 0; 512 } 513 } 514 515 /* 516 * Maintain a cache of leftmost tree entries (it is frequently 517 * used): 518 */ 519 if (leftmost) 520 cfs_rq->rb_leftmost = &se->run_node; 521 522 rb_link_node(&se->run_node, parent, link); 523 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); 524 } 525 526 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 527 { 528 if (cfs_rq->rb_leftmost == &se->run_node) { 529 struct rb_node *next_node; 530 531 next_node = rb_next(&se->run_node); 532 cfs_rq->rb_leftmost = next_node; 533 } 534 535 rb_erase(&se->run_node, &cfs_rq->tasks_timeline); 536 } 537 538 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) 539 { 540 struct rb_node *left = cfs_rq->rb_leftmost; 541 542 if (!left) 543 return NULL; 544 545 return rb_entry(left, struct sched_entity, run_node); 546 } 547 548 static struct sched_entity *__pick_next_entity(struct sched_entity *se) 549 { 550 struct rb_node *next = rb_next(&se->run_node); 551 552 if (!next) 553 return NULL; 554 555 return rb_entry(next, struct sched_entity, run_node); 556 } 557 558 #ifdef CONFIG_SCHED_DEBUG 559 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) 560 { 561 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); 562 563 if (!last) 564 return NULL; 565 566 return rb_entry(last, struct sched_entity, run_node); 567 } 568 569 /************************************************************** 570 * Scheduling class statistics methods: 571 */ 572 573 int sched_proc_update_handler(struct ctl_table *table, int write, 574 void __user *buffer, size_t *lenp, 575 loff_t *ppos) 576 { 577 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 578 int factor = get_update_sysctl_factor(); 579 580 if (ret || !write) 581 return ret; 582 583 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, 584 sysctl_sched_min_granularity); 585 586 #define WRT_SYSCTL(name) \ 587 (normalized_sysctl_##name = sysctl_##name / (factor)) 588 WRT_SYSCTL(sched_min_granularity); 589 WRT_SYSCTL(sched_latency); 590 WRT_SYSCTL(sched_wakeup_granularity); 591 #undef WRT_SYSCTL 592 593 return 0; 594 } 595 #endif 596 597 /* 598 * delta /= w 599 */ 600 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) 601 { 602 if (unlikely(se->load.weight != NICE_0_LOAD)) 603 delta = __calc_delta(delta, NICE_0_LOAD, &se->load); 604 605 return delta; 606 } 607 608 /* 609 * The idea is to set a period in which each task runs once. 610 * 611 * When there are too many tasks (sched_nr_latency) we have to stretch 612 * this period because otherwise the slices get too small. 613 * 614 * p = (nr <= nl) ? l : l*nr/nl 615 */ 616 static u64 __sched_period(unsigned long nr_running) 617 { 618 u64 period = sysctl_sched_latency; 619 unsigned long nr_latency = sched_nr_latency; 620 621 if (unlikely(nr_running > nr_latency)) { 622 period = sysctl_sched_min_granularity; 623 period *= nr_running; 624 } 625 626 return period; 627 } 628 629 /* 630 * We calculate the wall-time slice from the period by taking a part 631 * proportional to the weight. 632 * 633 * s = p*P[w/rw] 634 */ 635 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 636 { 637 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); 638 639 for_each_sched_entity(se) { 640 struct load_weight *load; 641 struct load_weight lw; 642 643 cfs_rq = cfs_rq_of(se); 644 load = &cfs_rq->load; 645 646 if (unlikely(!se->on_rq)) { 647 lw = cfs_rq->load; 648 649 update_load_add(&lw, se->load.weight); 650 load = &lw; 651 } 652 slice = __calc_delta(slice, se->load.weight, load); 653 } 654 return slice; 655 } 656 657 /* 658 * We calculate the vruntime slice of a to-be-inserted task. 659 * 660 * vs = s/w 661 */ 662 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) 663 { 664 return calc_delta_fair(sched_slice(cfs_rq, se), se); 665 } 666 667 #ifdef CONFIG_SMP 668 static unsigned long task_h_load(struct task_struct *p); 669 670 static inline void __update_task_entity_contrib(struct sched_entity *se); 671 672 /* Give new task start runnable values to heavy its load in infant time */ 673 void init_task_runnable_average(struct task_struct *p) 674 { 675 u32 slice; 676 677 p->se.avg.decay_count = 0; 678 slice = sched_slice(task_cfs_rq(p), &p->se) >> 10; 679 p->se.avg.runnable_avg_sum = slice; 680 p->se.avg.runnable_avg_period = slice; 681 __update_task_entity_contrib(&p->se); 682 } 683 #else 684 void init_task_runnable_average(struct task_struct *p) 685 { 686 } 687 #endif 688 689 /* 690 * Update the current task's runtime statistics. 691 */ 692 static void update_curr(struct cfs_rq *cfs_rq) 693 { 694 struct sched_entity *curr = cfs_rq->curr; 695 u64 now = rq_clock_task(rq_of(cfs_rq)); 696 u64 delta_exec; 697 698 if (unlikely(!curr)) 699 return; 700 701 delta_exec = now - curr->exec_start; 702 if (unlikely((s64)delta_exec <= 0)) 703 return; 704 705 curr->exec_start = now; 706 707 schedstat_set(curr->statistics.exec_max, 708 max(delta_exec, curr->statistics.exec_max)); 709 710 curr->sum_exec_runtime += delta_exec; 711 schedstat_add(cfs_rq, exec_clock, delta_exec); 712 713 curr->vruntime += calc_delta_fair(delta_exec, curr); 714 update_min_vruntime(cfs_rq); 715 716 if (entity_is_task(curr)) { 717 struct task_struct *curtask = task_of(curr); 718 719 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); 720 cpuacct_charge(curtask, delta_exec); 721 account_group_exec_runtime(curtask, delta_exec); 722 } 723 724 account_cfs_rq_runtime(cfs_rq, delta_exec); 725 } 726 727 static inline void 728 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 729 { 730 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq))); 731 } 732 733 /* 734 * Task is being enqueued - update stats: 735 */ 736 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 737 { 738 /* 739 * Are we enqueueing a waiting task? (for current tasks 740 * a dequeue/enqueue event is a NOP) 741 */ 742 if (se != cfs_rq->curr) 743 update_stats_wait_start(cfs_rq, se); 744 } 745 746 static void 747 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) 748 { 749 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max, 750 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start)); 751 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1); 752 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum + 753 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); 754 #ifdef CONFIG_SCHEDSTATS 755 if (entity_is_task(se)) { 756 trace_sched_stat_wait(task_of(se), 757 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); 758 } 759 #endif 760 schedstat_set(se->statistics.wait_start, 0); 761 } 762 763 static inline void 764 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 765 { 766 /* 767 * Mark the end of the wait period if dequeueing a 768 * waiting task: 769 */ 770 if (se != cfs_rq->curr) 771 update_stats_wait_end(cfs_rq, se); 772 } 773 774 /* 775 * We are picking a new current task - update its stats: 776 */ 777 static inline void 778 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 779 { 780 /* 781 * We are starting a new run period: 782 */ 783 se->exec_start = rq_clock_task(rq_of(cfs_rq)); 784 } 785 786 /************************************************** 787 * Scheduling class queueing methods: 788 */ 789 790 #ifdef CONFIG_NUMA_BALANCING 791 /* 792 * Approximate time to scan a full NUMA task in ms. The task scan period is 793 * calculated based on the tasks virtual memory size and 794 * numa_balancing_scan_size. 795 */ 796 unsigned int sysctl_numa_balancing_scan_period_min = 1000; 797 unsigned int sysctl_numa_balancing_scan_period_max = 60000; 798 799 /* Portion of address space to scan in MB */ 800 unsigned int sysctl_numa_balancing_scan_size = 256; 801 802 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ 803 unsigned int sysctl_numa_balancing_scan_delay = 1000; 804 805 static unsigned int task_nr_scan_windows(struct task_struct *p) 806 { 807 unsigned long rss = 0; 808 unsigned long nr_scan_pages; 809 810 /* 811 * Calculations based on RSS as non-present and empty pages are skipped 812 * by the PTE scanner and NUMA hinting faults should be trapped based 813 * on resident pages 814 */ 815 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); 816 rss = get_mm_rss(p->mm); 817 if (!rss) 818 rss = nr_scan_pages; 819 820 rss = round_up(rss, nr_scan_pages); 821 return rss / nr_scan_pages; 822 } 823 824 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ 825 #define MAX_SCAN_WINDOW 2560 826 827 static unsigned int task_scan_min(struct task_struct *p) 828 { 829 unsigned int scan, floor; 830 unsigned int windows = 1; 831 832 if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW) 833 windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size; 834 floor = 1000 / windows; 835 836 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); 837 return max_t(unsigned int, floor, scan); 838 } 839 840 static unsigned int task_scan_max(struct task_struct *p) 841 { 842 unsigned int smin = task_scan_min(p); 843 unsigned int smax; 844 845 /* Watch for min being lower than max due to floor calculations */ 846 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); 847 return max(smin, smax); 848 } 849 850 static void account_numa_enqueue(struct rq *rq, struct task_struct *p) 851 { 852 rq->nr_numa_running += (p->numa_preferred_nid != -1); 853 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); 854 } 855 856 static void account_numa_dequeue(struct rq *rq, struct task_struct *p) 857 { 858 rq->nr_numa_running -= (p->numa_preferred_nid != -1); 859 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); 860 } 861 862 struct numa_group { 863 atomic_t refcount; 864 865 spinlock_t lock; /* nr_tasks, tasks */ 866 int nr_tasks; 867 pid_t gid; 868 struct list_head task_list; 869 870 struct rcu_head rcu; 871 nodemask_t active_nodes; 872 unsigned long total_faults; 873 /* 874 * Faults_cpu is used to decide whether memory should move 875 * towards the CPU. As a consequence, these stats are weighted 876 * more by CPU use than by memory faults. 877 */ 878 unsigned long *faults_cpu; 879 unsigned long faults[0]; 880 }; 881 882 /* Shared or private faults. */ 883 #define NR_NUMA_HINT_FAULT_TYPES 2 884 885 /* Memory and CPU locality */ 886 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) 887 888 /* Averaged statistics, and temporary buffers. */ 889 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) 890 891 pid_t task_numa_group_id(struct task_struct *p) 892 { 893 return p->numa_group ? p->numa_group->gid : 0; 894 } 895 896 static inline int task_faults_idx(int nid, int priv) 897 { 898 return NR_NUMA_HINT_FAULT_TYPES * nid + priv; 899 } 900 901 static inline unsigned long task_faults(struct task_struct *p, int nid) 902 { 903 if (!p->numa_faults_memory) 904 return 0; 905 906 return p->numa_faults_memory[task_faults_idx(nid, 0)] + 907 p->numa_faults_memory[task_faults_idx(nid, 1)]; 908 } 909 910 static inline unsigned long group_faults(struct task_struct *p, int nid) 911 { 912 if (!p->numa_group) 913 return 0; 914 915 return p->numa_group->faults[task_faults_idx(nid, 0)] + 916 p->numa_group->faults[task_faults_idx(nid, 1)]; 917 } 918 919 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) 920 { 921 return group->faults_cpu[task_faults_idx(nid, 0)] + 922 group->faults_cpu[task_faults_idx(nid, 1)]; 923 } 924 925 /* 926 * These return the fraction of accesses done by a particular task, or 927 * task group, on a particular numa node. The group weight is given a 928 * larger multiplier, in order to group tasks together that are almost 929 * evenly spread out between numa nodes. 930 */ 931 static inline unsigned long task_weight(struct task_struct *p, int nid) 932 { 933 unsigned long total_faults; 934 935 if (!p->numa_faults_memory) 936 return 0; 937 938 total_faults = p->total_numa_faults; 939 940 if (!total_faults) 941 return 0; 942 943 return 1000 * task_faults(p, nid) / total_faults; 944 } 945 946 static inline unsigned long group_weight(struct task_struct *p, int nid) 947 { 948 if (!p->numa_group || !p->numa_group->total_faults) 949 return 0; 950 951 return 1000 * group_faults(p, nid) / p->numa_group->total_faults; 952 } 953 954 bool should_numa_migrate_memory(struct task_struct *p, struct page * page, 955 int src_nid, int dst_cpu) 956 { 957 struct numa_group *ng = p->numa_group; 958 int dst_nid = cpu_to_node(dst_cpu); 959 int last_cpupid, this_cpupid; 960 961 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); 962 963 /* 964 * Multi-stage node selection is used in conjunction with a periodic 965 * migration fault to build a temporal task<->page relation. By using 966 * a two-stage filter we remove short/unlikely relations. 967 * 968 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate 969 * a task's usage of a particular page (n_p) per total usage of this 970 * page (n_t) (in a given time-span) to a probability. 971 * 972 * Our periodic faults will sample this probability and getting the 973 * same result twice in a row, given these samples are fully 974 * independent, is then given by P(n)^2, provided our sample period 975 * is sufficiently short compared to the usage pattern. 976 * 977 * This quadric squishes small probabilities, making it less likely we 978 * act on an unlikely task<->page relation. 979 */ 980 last_cpupid = page_cpupid_xchg_last(page, this_cpupid); 981 if (!cpupid_pid_unset(last_cpupid) && 982 cpupid_to_nid(last_cpupid) != dst_nid) 983 return false; 984 985 /* Always allow migrate on private faults */ 986 if (cpupid_match_pid(p, last_cpupid)) 987 return true; 988 989 /* A shared fault, but p->numa_group has not been set up yet. */ 990 if (!ng) 991 return true; 992 993 /* 994 * Do not migrate if the destination is not a node that 995 * is actively used by this numa group. 996 */ 997 if (!node_isset(dst_nid, ng->active_nodes)) 998 return false; 999 1000 /* 1001 * Source is a node that is not actively used by this 1002 * numa group, while the destination is. Migrate. 1003 */ 1004 if (!node_isset(src_nid, ng->active_nodes)) 1005 return true; 1006 1007 /* 1008 * Both source and destination are nodes in active 1009 * use by this numa group. Maximize memory bandwidth 1010 * by migrating from more heavily used groups, to less 1011 * heavily used ones, spreading the load around. 1012 * Use a 1/4 hysteresis to avoid spurious page movement. 1013 */ 1014 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4); 1015 } 1016 1017 static unsigned long weighted_cpuload(const int cpu); 1018 static unsigned long source_load(int cpu, int type); 1019 static unsigned long target_load(int cpu, int type); 1020 static unsigned long capacity_of(int cpu); 1021 static long effective_load(struct task_group *tg, int cpu, long wl, long wg); 1022 1023 /* Cached statistics for all CPUs within a node */ 1024 struct numa_stats { 1025 unsigned long nr_running; 1026 unsigned long load; 1027 1028 /* Total compute capacity of CPUs on a node */ 1029 unsigned long compute_capacity; 1030 1031 /* Approximate capacity in terms of runnable tasks on a node */ 1032 unsigned long task_capacity; 1033 int has_free_capacity; 1034 }; 1035 1036 /* 1037 * XXX borrowed from update_sg_lb_stats 1038 */ 1039 static void update_numa_stats(struct numa_stats *ns, int nid) 1040 { 1041 int cpu, cpus = 0; 1042 1043 memset(ns, 0, sizeof(*ns)); 1044 for_each_cpu(cpu, cpumask_of_node(nid)) { 1045 struct rq *rq = cpu_rq(cpu); 1046 1047 ns->nr_running += rq->nr_running; 1048 ns->load += weighted_cpuload(cpu); 1049 ns->compute_capacity += capacity_of(cpu); 1050 1051 cpus++; 1052 } 1053 1054 /* 1055 * If we raced with hotplug and there are no CPUs left in our mask 1056 * the @ns structure is NULL'ed and task_numa_compare() will 1057 * not find this node attractive. 1058 * 1059 * We'll either bail at !has_free_capacity, or we'll detect a huge 1060 * imbalance and bail there. 1061 */ 1062 if (!cpus) 1063 return; 1064 1065 ns->load = (ns->load * SCHED_CAPACITY_SCALE) / ns->compute_capacity; 1066 ns->task_capacity = 1067 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE); 1068 ns->has_free_capacity = (ns->nr_running < ns->task_capacity); 1069 } 1070 1071 struct task_numa_env { 1072 struct task_struct *p; 1073 1074 int src_cpu, src_nid; 1075 int dst_cpu, dst_nid; 1076 1077 struct numa_stats src_stats, dst_stats; 1078 1079 int imbalance_pct; 1080 1081 struct task_struct *best_task; 1082 long best_imp; 1083 int best_cpu; 1084 }; 1085 1086 static void task_numa_assign(struct task_numa_env *env, 1087 struct task_struct *p, long imp) 1088 { 1089 if (env->best_task) 1090 put_task_struct(env->best_task); 1091 if (p) 1092 get_task_struct(p); 1093 1094 env->best_task = p; 1095 env->best_imp = imp; 1096 env->best_cpu = env->dst_cpu; 1097 } 1098 1099 static bool load_too_imbalanced(long orig_src_load, long orig_dst_load, 1100 long src_load, long dst_load, 1101 struct task_numa_env *env) 1102 { 1103 long imb, old_imb; 1104 1105 /* We care about the slope of the imbalance, not the direction. */ 1106 if (dst_load < src_load) 1107 swap(dst_load, src_load); 1108 1109 /* Is the difference below the threshold? */ 1110 imb = dst_load * 100 - src_load * env->imbalance_pct; 1111 if (imb <= 0) 1112 return false; 1113 1114 /* 1115 * The imbalance is above the allowed threshold. 1116 * Compare it with the old imbalance. 1117 */ 1118 if (orig_dst_load < orig_src_load) 1119 swap(orig_dst_load, orig_src_load); 1120 1121 old_imb = orig_dst_load * 100 - orig_src_load * env->imbalance_pct; 1122 1123 /* Would this change make things worse? */ 1124 return (imb > old_imb); 1125 } 1126 1127 /* 1128 * This checks if the overall compute and NUMA accesses of the system would 1129 * be improved if the source tasks was migrated to the target dst_cpu taking 1130 * into account that it might be best if task running on the dst_cpu should 1131 * be exchanged with the source task 1132 */ 1133 static void task_numa_compare(struct task_numa_env *env, 1134 long taskimp, long groupimp) 1135 { 1136 struct rq *src_rq = cpu_rq(env->src_cpu); 1137 struct rq *dst_rq = cpu_rq(env->dst_cpu); 1138 struct task_struct *cur; 1139 long orig_src_load, src_load; 1140 long orig_dst_load, dst_load; 1141 long load; 1142 long imp = (groupimp > 0) ? groupimp : taskimp; 1143 1144 rcu_read_lock(); 1145 cur = ACCESS_ONCE(dst_rq->curr); 1146 if (cur->pid == 0) /* idle */ 1147 cur = NULL; 1148 1149 /* 1150 * "imp" is the fault differential for the source task between the 1151 * source and destination node. Calculate the total differential for 1152 * the source task and potential destination task. The more negative 1153 * the value is, the more rmeote accesses that would be expected to 1154 * be incurred if the tasks were swapped. 1155 */ 1156 if (cur) { 1157 /* Skip this swap candidate if cannot move to the source cpu */ 1158 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur))) 1159 goto unlock; 1160 1161 /* 1162 * If dst and source tasks are in the same NUMA group, or not 1163 * in any group then look only at task weights. 1164 */ 1165 if (cur->numa_group == env->p->numa_group) { 1166 imp = taskimp + task_weight(cur, env->src_nid) - 1167 task_weight(cur, env->dst_nid); 1168 /* 1169 * Add some hysteresis to prevent swapping the 1170 * tasks within a group over tiny differences. 1171 */ 1172 if (cur->numa_group) 1173 imp -= imp/16; 1174 } else { 1175 /* 1176 * Compare the group weights. If a task is all by 1177 * itself (not part of a group), use the task weight 1178 * instead. 1179 */ 1180 if (env->p->numa_group) 1181 imp = groupimp; 1182 else 1183 imp = taskimp; 1184 1185 if (cur->numa_group) 1186 imp += group_weight(cur, env->src_nid) - 1187 group_weight(cur, env->dst_nid); 1188 else 1189 imp += task_weight(cur, env->src_nid) - 1190 task_weight(cur, env->dst_nid); 1191 } 1192 } 1193 1194 if (imp < env->best_imp) 1195 goto unlock; 1196 1197 if (!cur) { 1198 /* Is there capacity at our destination? */ 1199 if (env->src_stats.has_free_capacity && 1200 !env->dst_stats.has_free_capacity) 1201 goto unlock; 1202 1203 goto balance; 1204 } 1205 1206 /* Balance doesn't matter much if we're running a task per cpu */ 1207 if (src_rq->nr_running == 1 && dst_rq->nr_running == 1) 1208 goto assign; 1209 1210 /* 1211 * In the overloaded case, try and keep the load balanced. 1212 */ 1213 balance: 1214 orig_dst_load = env->dst_stats.load; 1215 orig_src_load = env->src_stats.load; 1216 1217 /* XXX missing capacity terms */ 1218 load = task_h_load(env->p); 1219 dst_load = orig_dst_load + load; 1220 src_load = orig_src_load - load; 1221 1222 if (cur) { 1223 load = task_h_load(cur); 1224 dst_load -= load; 1225 src_load += load; 1226 } 1227 1228 if (load_too_imbalanced(orig_src_load, orig_dst_load, 1229 src_load, dst_load, env)) 1230 goto unlock; 1231 1232 assign: 1233 task_numa_assign(env, cur, imp); 1234 unlock: 1235 rcu_read_unlock(); 1236 } 1237 1238 static void task_numa_find_cpu(struct task_numa_env *env, 1239 long taskimp, long groupimp) 1240 { 1241 int cpu; 1242 1243 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { 1244 /* Skip this CPU if the source task cannot migrate */ 1245 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p))) 1246 continue; 1247 1248 env->dst_cpu = cpu; 1249 task_numa_compare(env, taskimp, groupimp); 1250 } 1251 } 1252 1253 static int task_numa_migrate(struct task_struct *p) 1254 { 1255 struct task_numa_env env = { 1256 .p = p, 1257 1258 .src_cpu = task_cpu(p), 1259 .src_nid = task_node(p), 1260 1261 .imbalance_pct = 112, 1262 1263 .best_task = NULL, 1264 .best_imp = 0, 1265 .best_cpu = -1 1266 }; 1267 struct sched_domain *sd; 1268 unsigned long taskweight, groupweight; 1269 int nid, ret; 1270 long taskimp, groupimp; 1271 1272 /* 1273 * Pick the lowest SD_NUMA domain, as that would have the smallest 1274 * imbalance and would be the first to start moving tasks about. 1275 * 1276 * And we want to avoid any moving of tasks about, as that would create 1277 * random movement of tasks -- counter the numa conditions we're trying 1278 * to satisfy here. 1279 */ 1280 rcu_read_lock(); 1281 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); 1282 if (sd) 1283 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; 1284 rcu_read_unlock(); 1285 1286 /* 1287 * Cpusets can break the scheduler domain tree into smaller 1288 * balance domains, some of which do not cross NUMA boundaries. 1289 * Tasks that are "trapped" in such domains cannot be migrated 1290 * elsewhere, so there is no point in (re)trying. 1291 */ 1292 if (unlikely(!sd)) { 1293 p->numa_preferred_nid = task_node(p); 1294 return -EINVAL; 1295 } 1296 1297 taskweight = task_weight(p, env.src_nid); 1298 groupweight = group_weight(p, env.src_nid); 1299 update_numa_stats(&env.src_stats, env.src_nid); 1300 env.dst_nid = p->numa_preferred_nid; 1301 taskimp = task_weight(p, env.dst_nid) - taskweight; 1302 groupimp = group_weight(p, env.dst_nid) - groupweight; 1303 update_numa_stats(&env.dst_stats, env.dst_nid); 1304 1305 /* If the preferred nid has free capacity, try to use it. */ 1306 if (env.dst_stats.has_free_capacity) 1307 task_numa_find_cpu(&env, taskimp, groupimp); 1308 1309 /* No space available on the preferred nid. Look elsewhere. */ 1310 if (env.best_cpu == -1) { 1311 for_each_online_node(nid) { 1312 if (nid == env.src_nid || nid == p->numa_preferred_nid) 1313 continue; 1314 1315 /* Only consider nodes where both task and groups benefit */ 1316 taskimp = task_weight(p, nid) - taskweight; 1317 groupimp = group_weight(p, nid) - groupweight; 1318 if (taskimp < 0 && groupimp < 0) 1319 continue; 1320 1321 env.dst_nid = nid; 1322 update_numa_stats(&env.dst_stats, env.dst_nid); 1323 task_numa_find_cpu(&env, taskimp, groupimp); 1324 } 1325 } 1326 1327 /* No better CPU than the current one was found. */ 1328 if (env.best_cpu == -1) 1329 return -EAGAIN; 1330 1331 /* 1332 * If the task is part of a workload that spans multiple NUMA nodes, 1333 * and is migrating into one of the workload's active nodes, remember 1334 * this node as the task's preferred numa node, so the workload can 1335 * settle down. 1336 * A task that migrated to a second choice node will be better off 1337 * trying for a better one later. Do not set the preferred node here. 1338 */ 1339 if (p->numa_group && node_isset(env.dst_nid, p->numa_group->active_nodes)) 1340 sched_setnuma(p, env.dst_nid); 1341 1342 /* 1343 * Reset the scan period if the task is being rescheduled on an 1344 * alternative node to recheck if the tasks is now properly placed. 1345 */ 1346 p->numa_scan_period = task_scan_min(p); 1347 1348 if (env.best_task == NULL) { 1349 ret = migrate_task_to(p, env.best_cpu); 1350 if (ret != 0) 1351 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); 1352 return ret; 1353 } 1354 1355 ret = migrate_swap(p, env.best_task); 1356 if (ret != 0) 1357 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); 1358 put_task_struct(env.best_task); 1359 return ret; 1360 } 1361 1362 /* Attempt to migrate a task to a CPU on the preferred node. */ 1363 static void numa_migrate_preferred(struct task_struct *p) 1364 { 1365 unsigned long interval = HZ; 1366 1367 /* This task has no NUMA fault statistics yet */ 1368 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults_memory)) 1369 return; 1370 1371 /* Periodically retry migrating the task to the preferred node */ 1372 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); 1373 p->numa_migrate_retry = jiffies + interval; 1374 1375 /* Success if task is already running on preferred CPU */ 1376 if (task_node(p) == p->numa_preferred_nid) 1377 return; 1378 1379 /* Otherwise, try migrate to a CPU on the preferred node */ 1380 task_numa_migrate(p); 1381 } 1382 1383 /* 1384 * Find the nodes on which the workload is actively running. We do this by 1385 * tracking the nodes from which NUMA hinting faults are triggered. This can 1386 * be different from the set of nodes where the workload's memory is currently 1387 * located. 1388 * 1389 * The bitmask is used to make smarter decisions on when to do NUMA page 1390 * migrations, To prevent flip-flopping, and excessive page migrations, nodes 1391 * are added when they cause over 6/16 of the maximum number of faults, but 1392 * only removed when they drop below 3/16. 1393 */ 1394 static void update_numa_active_node_mask(struct numa_group *numa_group) 1395 { 1396 unsigned long faults, max_faults = 0; 1397 int nid; 1398 1399 for_each_online_node(nid) { 1400 faults = group_faults_cpu(numa_group, nid); 1401 if (faults > max_faults) 1402 max_faults = faults; 1403 } 1404 1405 for_each_online_node(nid) { 1406 faults = group_faults_cpu(numa_group, nid); 1407 if (!node_isset(nid, numa_group->active_nodes)) { 1408 if (faults > max_faults * 6 / 16) 1409 node_set(nid, numa_group->active_nodes); 1410 } else if (faults < max_faults * 3 / 16) 1411 node_clear(nid, numa_group->active_nodes); 1412 } 1413 } 1414 1415 /* 1416 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS 1417 * increments. The more local the fault statistics are, the higher the scan 1418 * period will be for the next scan window. If local/remote ratio is below 1419 * NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) the 1420 * scan period will decrease 1421 */ 1422 #define NUMA_PERIOD_SLOTS 10 1423 #define NUMA_PERIOD_THRESHOLD 3 1424 1425 /* 1426 * Increase the scan period (slow down scanning) if the majority of 1427 * our memory is already on our local node, or if the majority of 1428 * the page accesses are shared with other processes. 1429 * Otherwise, decrease the scan period. 1430 */ 1431 static void update_task_scan_period(struct task_struct *p, 1432 unsigned long shared, unsigned long private) 1433 { 1434 unsigned int period_slot; 1435 int ratio; 1436 int diff; 1437 1438 unsigned long remote = p->numa_faults_locality[0]; 1439 unsigned long local = p->numa_faults_locality[1]; 1440 1441 /* 1442 * If there were no record hinting faults then either the task is 1443 * completely idle or all activity is areas that are not of interest 1444 * to automatic numa balancing. Scan slower 1445 */ 1446 if (local + shared == 0) { 1447 p->numa_scan_period = min(p->numa_scan_period_max, 1448 p->numa_scan_period << 1); 1449 1450 p->mm->numa_next_scan = jiffies + 1451 msecs_to_jiffies(p->numa_scan_period); 1452 1453 return; 1454 } 1455 1456 /* 1457 * Prepare to scale scan period relative to the current period. 1458 * == NUMA_PERIOD_THRESHOLD scan period stays the same 1459 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) 1460 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) 1461 */ 1462 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); 1463 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); 1464 if (ratio >= NUMA_PERIOD_THRESHOLD) { 1465 int slot = ratio - NUMA_PERIOD_THRESHOLD; 1466 if (!slot) 1467 slot = 1; 1468 diff = slot * period_slot; 1469 } else { 1470 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; 1471 1472 /* 1473 * Scale scan rate increases based on sharing. There is an 1474 * inverse relationship between the degree of sharing and 1475 * the adjustment made to the scanning period. Broadly 1476 * speaking the intent is that there is little point 1477 * scanning faster if shared accesses dominate as it may 1478 * simply bounce migrations uselessly 1479 */ 1480 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared)); 1481 diff = (diff * ratio) / NUMA_PERIOD_SLOTS; 1482 } 1483 1484 p->numa_scan_period = clamp(p->numa_scan_period + diff, 1485 task_scan_min(p), task_scan_max(p)); 1486 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 1487 } 1488 1489 /* 1490 * Get the fraction of time the task has been running since the last 1491 * NUMA placement cycle. The scheduler keeps similar statistics, but 1492 * decays those on a 32ms period, which is orders of magnitude off 1493 * from the dozens-of-seconds NUMA balancing period. Use the scheduler 1494 * stats only if the task is so new there are no NUMA statistics yet. 1495 */ 1496 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) 1497 { 1498 u64 runtime, delta, now; 1499 /* Use the start of this time slice to avoid calculations. */ 1500 now = p->se.exec_start; 1501 runtime = p->se.sum_exec_runtime; 1502 1503 if (p->last_task_numa_placement) { 1504 delta = runtime - p->last_sum_exec_runtime; 1505 *period = now - p->last_task_numa_placement; 1506 } else { 1507 delta = p->se.avg.runnable_avg_sum; 1508 *period = p->se.avg.runnable_avg_period; 1509 } 1510 1511 p->last_sum_exec_runtime = runtime; 1512 p->last_task_numa_placement = now; 1513 1514 return delta; 1515 } 1516 1517 static void task_numa_placement(struct task_struct *p) 1518 { 1519 int seq, nid, max_nid = -1, max_group_nid = -1; 1520 unsigned long max_faults = 0, max_group_faults = 0; 1521 unsigned long fault_types[2] = { 0, 0 }; 1522 unsigned long total_faults; 1523 u64 runtime, period; 1524 spinlock_t *group_lock = NULL; 1525 1526 seq = ACCESS_ONCE(p->mm->numa_scan_seq); 1527 if (p->numa_scan_seq == seq) 1528 return; 1529 p->numa_scan_seq = seq; 1530 p->numa_scan_period_max = task_scan_max(p); 1531 1532 total_faults = p->numa_faults_locality[0] + 1533 p->numa_faults_locality[1]; 1534 runtime = numa_get_avg_runtime(p, &period); 1535 1536 /* If the task is part of a group prevent parallel updates to group stats */ 1537 if (p->numa_group) { 1538 group_lock = &p->numa_group->lock; 1539 spin_lock_irq(group_lock); 1540 } 1541 1542 /* Find the node with the highest number of faults */ 1543 for_each_online_node(nid) { 1544 unsigned long faults = 0, group_faults = 0; 1545 int priv, i; 1546 1547 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { 1548 long diff, f_diff, f_weight; 1549 1550 i = task_faults_idx(nid, priv); 1551 1552 /* Decay existing window, copy faults since last scan */ 1553 diff = p->numa_faults_buffer_memory[i] - p->numa_faults_memory[i] / 2; 1554 fault_types[priv] += p->numa_faults_buffer_memory[i]; 1555 p->numa_faults_buffer_memory[i] = 0; 1556 1557 /* 1558 * Normalize the faults_from, so all tasks in a group 1559 * count according to CPU use, instead of by the raw 1560 * number of faults. Tasks with little runtime have 1561 * little over-all impact on throughput, and thus their 1562 * faults are less important. 1563 */ 1564 f_weight = div64_u64(runtime << 16, period + 1); 1565 f_weight = (f_weight * p->numa_faults_buffer_cpu[i]) / 1566 (total_faults + 1); 1567 f_diff = f_weight - p->numa_faults_cpu[i] / 2; 1568 p->numa_faults_buffer_cpu[i] = 0; 1569 1570 p->numa_faults_memory[i] += diff; 1571 p->numa_faults_cpu[i] += f_diff; 1572 faults += p->numa_faults_memory[i]; 1573 p->total_numa_faults += diff; 1574 if (p->numa_group) { 1575 /* safe because we can only change our own group */ 1576 p->numa_group->faults[i] += diff; 1577 p->numa_group->faults_cpu[i] += f_diff; 1578 p->numa_group->total_faults += diff; 1579 group_faults += p->numa_group->faults[i]; 1580 } 1581 } 1582 1583 if (faults > max_faults) { 1584 max_faults = faults; 1585 max_nid = nid; 1586 } 1587 1588 if (group_faults > max_group_faults) { 1589 max_group_faults = group_faults; 1590 max_group_nid = nid; 1591 } 1592 } 1593 1594 update_task_scan_period(p, fault_types[0], fault_types[1]); 1595 1596 if (p->numa_group) { 1597 update_numa_active_node_mask(p->numa_group); 1598 /* 1599 * If the preferred task and group nids are different, 1600 * iterate over the nodes again to find the best place. 1601 */ 1602 if (max_nid != max_group_nid) { 1603 unsigned long weight, max_weight = 0; 1604 1605 for_each_online_node(nid) { 1606 weight = task_weight(p, nid) + group_weight(p, nid); 1607 if (weight > max_weight) { 1608 max_weight = weight; 1609 max_nid = nid; 1610 } 1611 } 1612 } 1613 1614 spin_unlock_irq(group_lock); 1615 } 1616 1617 /* Preferred node as the node with the most faults */ 1618 if (max_faults && max_nid != p->numa_preferred_nid) { 1619 /* Update the preferred nid and migrate task if possible */ 1620 sched_setnuma(p, max_nid); 1621 numa_migrate_preferred(p); 1622 } 1623 } 1624 1625 static inline int get_numa_group(struct numa_group *grp) 1626 { 1627 return atomic_inc_not_zero(&grp->refcount); 1628 } 1629 1630 static inline void put_numa_group(struct numa_group *grp) 1631 { 1632 if (atomic_dec_and_test(&grp->refcount)) 1633 kfree_rcu(grp, rcu); 1634 } 1635 1636 static void task_numa_group(struct task_struct *p, int cpupid, int flags, 1637 int *priv) 1638 { 1639 struct numa_group *grp, *my_grp; 1640 struct task_struct *tsk; 1641 bool join = false; 1642 int cpu = cpupid_to_cpu(cpupid); 1643 int i; 1644 1645 if (unlikely(!p->numa_group)) { 1646 unsigned int size = sizeof(struct numa_group) + 1647 4*nr_node_ids*sizeof(unsigned long); 1648 1649 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); 1650 if (!grp) 1651 return; 1652 1653 atomic_set(&grp->refcount, 1); 1654 spin_lock_init(&grp->lock); 1655 INIT_LIST_HEAD(&grp->task_list); 1656 grp->gid = p->pid; 1657 /* Second half of the array tracks nids where faults happen */ 1658 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * 1659 nr_node_ids; 1660 1661 node_set(task_node(current), grp->active_nodes); 1662 1663 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 1664 grp->faults[i] = p->numa_faults_memory[i]; 1665 1666 grp->total_faults = p->total_numa_faults; 1667 1668 list_add(&p->numa_entry, &grp->task_list); 1669 grp->nr_tasks++; 1670 rcu_assign_pointer(p->numa_group, grp); 1671 } 1672 1673 rcu_read_lock(); 1674 tsk = ACCESS_ONCE(cpu_rq(cpu)->curr); 1675 1676 if (!cpupid_match_pid(tsk, cpupid)) 1677 goto no_join; 1678 1679 grp = rcu_dereference(tsk->numa_group); 1680 if (!grp) 1681 goto no_join; 1682 1683 my_grp = p->numa_group; 1684 if (grp == my_grp) 1685 goto no_join; 1686 1687 /* 1688 * Only join the other group if its bigger; if we're the bigger group, 1689 * the other task will join us. 1690 */ 1691 if (my_grp->nr_tasks > grp->nr_tasks) 1692 goto no_join; 1693 1694 /* 1695 * Tie-break on the grp address. 1696 */ 1697 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) 1698 goto no_join; 1699 1700 /* Always join threads in the same process. */ 1701 if (tsk->mm == current->mm) 1702 join = true; 1703 1704 /* Simple filter to avoid false positives due to PID collisions */ 1705 if (flags & TNF_SHARED) 1706 join = true; 1707 1708 /* Update priv based on whether false sharing was detected */ 1709 *priv = !join; 1710 1711 if (join && !get_numa_group(grp)) 1712 goto no_join; 1713 1714 rcu_read_unlock(); 1715 1716 if (!join) 1717 return; 1718 1719 BUG_ON(irqs_disabled()); 1720 double_lock_irq(&my_grp->lock, &grp->lock); 1721 1722 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { 1723 my_grp->faults[i] -= p->numa_faults_memory[i]; 1724 grp->faults[i] += p->numa_faults_memory[i]; 1725 } 1726 my_grp->total_faults -= p->total_numa_faults; 1727 grp->total_faults += p->total_numa_faults; 1728 1729 list_move(&p->numa_entry, &grp->task_list); 1730 my_grp->nr_tasks--; 1731 grp->nr_tasks++; 1732 1733 spin_unlock(&my_grp->lock); 1734 spin_unlock_irq(&grp->lock); 1735 1736 rcu_assign_pointer(p->numa_group, grp); 1737 1738 put_numa_group(my_grp); 1739 return; 1740 1741 no_join: 1742 rcu_read_unlock(); 1743 return; 1744 } 1745 1746 void task_numa_free(struct task_struct *p) 1747 { 1748 struct numa_group *grp = p->numa_group; 1749 void *numa_faults = p->numa_faults_memory; 1750 unsigned long flags; 1751 int i; 1752 1753 if (grp) { 1754 spin_lock_irqsave(&grp->lock, flags); 1755 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 1756 grp->faults[i] -= p->numa_faults_memory[i]; 1757 grp->total_faults -= p->total_numa_faults; 1758 1759 list_del(&p->numa_entry); 1760 grp->nr_tasks--; 1761 spin_unlock_irqrestore(&grp->lock, flags); 1762 rcu_assign_pointer(p->numa_group, NULL); 1763 put_numa_group(grp); 1764 } 1765 1766 p->numa_faults_memory = NULL; 1767 p->numa_faults_buffer_memory = NULL; 1768 p->numa_faults_cpu= NULL; 1769 p->numa_faults_buffer_cpu = NULL; 1770 kfree(numa_faults); 1771 } 1772 1773 /* 1774 * Got a PROT_NONE fault for a page on @node. 1775 */ 1776 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) 1777 { 1778 struct task_struct *p = current; 1779 bool migrated = flags & TNF_MIGRATED; 1780 int cpu_node = task_node(current); 1781 int local = !!(flags & TNF_FAULT_LOCAL); 1782 int priv; 1783 1784 if (!numabalancing_enabled) 1785 return; 1786 1787 /* for example, ksmd faulting in a user's mm */ 1788 if (!p->mm) 1789 return; 1790 1791 /* Do not worry about placement if exiting */ 1792 if (p->state == TASK_DEAD) 1793 return; 1794 1795 /* Allocate buffer to track faults on a per-node basis */ 1796 if (unlikely(!p->numa_faults_memory)) { 1797 int size = sizeof(*p->numa_faults_memory) * 1798 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; 1799 1800 p->numa_faults_memory = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); 1801 if (!p->numa_faults_memory) 1802 return; 1803 1804 BUG_ON(p->numa_faults_buffer_memory); 1805 /* 1806 * The averaged statistics, shared & private, memory & cpu, 1807 * occupy the first half of the array. The second half of the 1808 * array is for current counters, which are averaged into the 1809 * first set by task_numa_placement. 1810 */ 1811 p->numa_faults_cpu = p->numa_faults_memory + (2 * nr_node_ids); 1812 p->numa_faults_buffer_memory = p->numa_faults_memory + (4 * nr_node_ids); 1813 p->numa_faults_buffer_cpu = p->numa_faults_memory + (6 * nr_node_ids); 1814 p->total_numa_faults = 0; 1815 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 1816 } 1817 1818 /* 1819 * First accesses are treated as private, otherwise consider accesses 1820 * to be private if the accessing pid has not changed 1821 */ 1822 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { 1823 priv = 1; 1824 } else { 1825 priv = cpupid_match_pid(p, last_cpupid); 1826 if (!priv && !(flags & TNF_NO_GROUP)) 1827 task_numa_group(p, last_cpupid, flags, &priv); 1828 } 1829 1830 /* 1831 * If a workload spans multiple NUMA nodes, a shared fault that 1832 * occurs wholly within the set of nodes that the workload is 1833 * actively using should be counted as local. This allows the 1834 * scan rate to slow down when a workload has settled down. 1835 */ 1836 if (!priv && !local && p->numa_group && 1837 node_isset(cpu_node, p->numa_group->active_nodes) && 1838 node_isset(mem_node, p->numa_group->active_nodes)) 1839 local = 1; 1840 1841 task_numa_placement(p); 1842 1843 /* 1844 * Retry task to preferred node migration periodically, in case it 1845 * case it previously failed, or the scheduler moved us. 1846 */ 1847 if (time_after(jiffies, p->numa_migrate_retry)) 1848 numa_migrate_preferred(p); 1849 1850 if (migrated) 1851 p->numa_pages_migrated += pages; 1852 1853 p->numa_faults_buffer_memory[task_faults_idx(mem_node, priv)] += pages; 1854 p->numa_faults_buffer_cpu[task_faults_idx(cpu_node, priv)] += pages; 1855 p->numa_faults_locality[local] += pages; 1856 } 1857 1858 static void reset_ptenuma_scan(struct task_struct *p) 1859 { 1860 ACCESS_ONCE(p->mm->numa_scan_seq)++; 1861 p->mm->numa_scan_offset = 0; 1862 } 1863 1864 /* 1865 * The expensive part of numa migration is done from task_work context. 1866 * Triggered from task_tick_numa(). 1867 */ 1868 void task_numa_work(struct callback_head *work) 1869 { 1870 unsigned long migrate, next_scan, now = jiffies; 1871 struct task_struct *p = current; 1872 struct mm_struct *mm = p->mm; 1873 struct vm_area_struct *vma; 1874 unsigned long start, end; 1875 unsigned long nr_pte_updates = 0; 1876 long pages; 1877 1878 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work)); 1879 1880 work->next = work; /* protect against double add */ 1881 /* 1882 * Who cares about NUMA placement when they're dying. 1883 * 1884 * NOTE: make sure not to dereference p->mm before this check, 1885 * exit_task_work() happens _after_ exit_mm() so we could be called 1886 * without p->mm even though we still had it when we enqueued this 1887 * work. 1888 */ 1889 if (p->flags & PF_EXITING) 1890 return; 1891 1892 if (!mm->numa_next_scan) { 1893 mm->numa_next_scan = now + 1894 msecs_to_jiffies(sysctl_numa_balancing_scan_delay); 1895 } 1896 1897 /* 1898 * Enforce maximal scan/migration frequency.. 1899 */ 1900 migrate = mm->numa_next_scan; 1901 if (time_before(now, migrate)) 1902 return; 1903 1904 if (p->numa_scan_period == 0) { 1905 p->numa_scan_period_max = task_scan_max(p); 1906 p->numa_scan_period = task_scan_min(p); 1907 } 1908 1909 next_scan = now + msecs_to_jiffies(p->numa_scan_period); 1910 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) 1911 return; 1912 1913 /* 1914 * Delay this task enough that another task of this mm will likely win 1915 * the next time around. 1916 */ 1917 p->node_stamp += 2 * TICK_NSEC; 1918 1919 start = mm->numa_scan_offset; 1920 pages = sysctl_numa_balancing_scan_size; 1921 pages <<= 20 - PAGE_SHIFT; /* MB in pages */ 1922 if (!pages) 1923 return; 1924 1925 down_read(&mm->mmap_sem); 1926 vma = find_vma(mm, start); 1927 if (!vma) { 1928 reset_ptenuma_scan(p); 1929 start = 0; 1930 vma = mm->mmap; 1931 } 1932 for (; vma; vma = vma->vm_next) { 1933 if (!vma_migratable(vma) || !vma_policy_mof(p, vma)) 1934 continue; 1935 1936 /* 1937 * Shared library pages mapped by multiple processes are not 1938 * migrated as it is expected they are cache replicated. Avoid 1939 * hinting faults in read-only file-backed mappings or the vdso 1940 * as migrating the pages will be of marginal benefit. 1941 */ 1942 if (!vma->vm_mm || 1943 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) 1944 continue; 1945 1946 /* 1947 * Skip inaccessible VMAs to avoid any confusion between 1948 * PROT_NONE and NUMA hinting ptes 1949 */ 1950 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 1951 continue; 1952 1953 do { 1954 start = max(start, vma->vm_start); 1955 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); 1956 end = min(end, vma->vm_end); 1957 nr_pte_updates += change_prot_numa(vma, start, end); 1958 1959 /* 1960 * Scan sysctl_numa_balancing_scan_size but ensure that 1961 * at least one PTE is updated so that unused virtual 1962 * address space is quickly skipped. 1963 */ 1964 if (nr_pte_updates) 1965 pages -= (end - start) >> PAGE_SHIFT; 1966 1967 start = end; 1968 if (pages <= 0) 1969 goto out; 1970 1971 cond_resched(); 1972 } while (end != vma->vm_end); 1973 } 1974 1975 out: 1976 /* 1977 * It is possible to reach the end of the VMA list but the last few 1978 * VMAs are not guaranteed to the vma_migratable. If they are not, we 1979 * would find the !migratable VMA on the next scan but not reset the 1980 * scanner to the start so check it now. 1981 */ 1982 if (vma) 1983 mm->numa_scan_offset = start; 1984 else 1985 reset_ptenuma_scan(p); 1986 up_read(&mm->mmap_sem); 1987 } 1988 1989 /* 1990 * Drive the periodic memory faults.. 1991 */ 1992 void task_tick_numa(struct rq *rq, struct task_struct *curr) 1993 { 1994 struct callback_head *work = &curr->numa_work; 1995 u64 period, now; 1996 1997 /* 1998 * We don't care about NUMA placement if we don't have memory. 1999 */ 2000 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) 2001 return; 2002 2003 /* 2004 * Using runtime rather than walltime has the dual advantage that 2005 * we (mostly) drive the selection from busy threads and that the 2006 * task needs to have done some actual work before we bother with 2007 * NUMA placement. 2008 */ 2009 now = curr->se.sum_exec_runtime; 2010 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; 2011 2012 if (now - curr->node_stamp > period) { 2013 if (!curr->node_stamp) 2014 curr->numa_scan_period = task_scan_min(curr); 2015 curr->node_stamp += period; 2016 2017 if (!time_before(jiffies, curr->mm->numa_next_scan)) { 2018 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ 2019 task_work_add(curr, work, true); 2020 } 2021 } 2022 } 2023 #else 2024 static void task_tick_numa(struct rq *rq, struct task_struct *curr) 2025 { 2026 } 2027 2028 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) 2029 { 2030 } 2031 2032 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) 2033 { 2034 } 2035 #endif /* CONFIG_NUMA_BALANCING */ 2036 2037 static void 2038 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2039 { 2040 update_load_add(&cfs_rq->load, se->load.weight); 2041 if (!parent_entity(se)) 2042 update_load_add(&rq_of(cfs_rq)->load, se->load.weight); 2043 #ifdef CONFIG_SMP 2044 if (entity_is_task(se)) { 2045 struct rq *rq = rq_of(cfs_rq); 2046 2047 account_numa_enqueue(rq, task_of(se)); 2048 list_add(&se->group_node, &rq->cfs_tasks); 2049 } 2050 #endif 2051 cfs_rq->nr_running++; 2052 } 2053 2054 static void 2055 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2056 { 2057 update_load_sub(&cfs_rq->load, se->load.weight); 2058 if (!parent_entity(se)) 2059 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight); 2060 if (entity_is_task(se)) { 2061 account_numa_dequeue(rq_of(cfs_rq), task_of(se)); 2062 list_del_init(&se->group_node); 2063 } 2064 cfs_rq->nr_running--; 2065 } 2066 2067 #ifdef CONFIG_FAIR_GROUP_SCHED 2068 # ifdef CONFIG_SMP 2069 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) 2070 { 2071 long tg_weight; 2072 2073 /* 2074 * Use this CPU's actual weight instead of the last load_contribution 2075 * to gain a more accurate current total weight. See 2076 * update_cfs_rq_load_contribution(). 2077 */ 2078 tg_weight = atomic_long_read(&tg->load_avg); 2079 tg_weight -= cfs_rq->tg_load_contrib; 2080 tg_weight += cfs_rq->load.weight; 2081 2082 return tg_weight; 2083 } 2084 2085 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2086 { 2087 long tg_weight, load, shares; 2088 2089 tg_weight = calc_tg_weight(tg, cfs_rq); 2090 load = cfs_rq->load.weight; 2091 2092 shares = (tg->shares * load); 2093 if (tg_weight) 2094 shares /= tg_weight; 2095 2096 if (shares < MIN_SHARES) 2097 shares = MIN_SHARES; 2098 if (shares > tg->shares) 2099 shares = tg->shares; 2100 2101 return shares; 2102 } 2103 # else /* CONFIG_SMP */ 2104 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2105 { 2106 return tg->shares; 2107 } 2108 # endif /* CONFIG_SMP */ 2109 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, 2110 unsigned long weight) 2111 { 2112 if (se->on_rq) { 2113 /* commit outstanding execution time */ 2114 if (cfs_rq->curr == se) 2115 update_curr(cfs_rq); 2116 account_entity_dequeue(cfs_rq, se); 2117 } 2118 2119 update_load_set(&se->load, weight); 2120 2121 if (se->on_rq) 2122 account_entity_enqueue(cfs_rq, se); 2123 } 2124 2125 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); 2126 2127 static void update_cfs_shares(struct cfs_rq *cfs_rq) 2128 { 2129 struct task_group *tg; 2130 struct sched_entity *se; 2131 long shares; 2132 2133 tg = cfs_rq->tg; 2134 se = tg->se[cpu_of(rq_of(cfs_rq))]; 2135 if (!se || throttled_hierarchy(cfs_rq)) 2136 return; 2137 #ifndef CONFIG_SMP 2138 if (likely(se->load.weight == tg->shares)) 2139 return; 2140 #endif 2141 shares = calc_cfs_shares(cfs_rq, tg); 2142 2143 reweight_entity(cfs_rq_of(se), se, shares); 2144 } 2145 #else /* CONFIG_FAIR_GROUP_SCHED */ 2146 static inline void update_cfs_shares(struct cfs_rq *cfs_rq) 2147 { 2148 } 2149 #endif /* CONFIG_FAIR_GROUP_SCHED */ 2150 2151 #ifdef CONFIG_SMP 2152 /* 2153 * We choose a half-life close to 1 scheduling period. 2154 * Note: The tables below are dependent on this value. 2155 */ 2156 #define LOAD_AVG_PERIOD 32 2157 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */ 2158 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */ 2159 2160 /* Precomputed fixed inverse multiplies for multiplication by y^n */ 2161 static const u32 runnable_avg_yN_inv[] = { 2162 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6, 2163 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85, 2164 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581, 2165 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9, 2166 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80, 2167 0x85aac367, 0x82cd8698, 2168 }; 2169 2170 /* 2171 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent 2172 * over-estimates when re-combining. 2173 */ 2174 static const u32 runnable_avg_yN_sum[] = { 2175 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103, 2176 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082, 2177 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371, 2178 }; 2179 2180 /* 2181 * Approximate: 2182 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period) 2183 */ 2184 static __always_inline u64 decay_load(u64 val, u64 n) 2185 { 2186 unsigned int local_n; 2187 2188 if (!n) 2189 return val; 2190 else if (unlikely(n > LOAD_AVG_PERIOD * 63)) 2191 return 0; 2192 2193 /* after bounds checking we can collapse to 32-bit */ 2194 local_n = n; 2195 2196 /* 2197 * As y^PERIOD = 1/2, we can combine 2198 * y^n = 1/2^(n/PERIOD) * k^(n%PERIOD) 2199 * With a look-up table which covers k^n (n<PERIOD) 2200 * 2201 * To achieve constant time decay_load. 2202 */ 2203 if (unlikely(local_n >= LOAD_AVG_PERIOD)) { 2204 val >>= local_n / LOAD_AVG_PERIOD; 2205 local_n %= LOAD_AVG_PERIOD; 2206 } 2207 2208 val *= runnable_avg_yN_inv[local_n]; 2209 /* We don't use SRR here since we always want to round down. */ 2210 return val >> 32; 2211 } 2212 2213 /* 2214 * For updates fully spanning n periods, the contribution to runnable 2215 * average will be: \Sum 1024*y^n 2216 * 2217 * We can compute this reasonably efficiently by combining: 2218 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD} 2219 */ 2220 static u32 __compute_runnable_contrib(u64 n) 2221 { 2222 u32 contrib = 0; 2223 2224 if (likely(n <= LOAD_AVG_PERIOD)) 2225 return runnable_avg_yN_sum[n]; 2226 else if (unlikely(n >= LOAD_AVG_MAX_N)) 2227 return LOAD_AVG_MAX; 2228 2229 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */ 2230 do { 2231 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */ 2232 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD]; 2233 2234 n -= LOAD_AVG_PERIOD; 2235 } while (n > LOAD_AVG_PERIOD); 2236 2237 contrib = decay_load(contrib, n); 2238 return contrib + runnable_avg_yN_sum[n]; 2239 } 2240 2241 /* 2242 * We can represent the historical contribution to runnable average as the 2243 * coefficients of a geometric series. To do this we sub-divide our runnable 2244 * history into segments of approximately 1ms (1024us); label the segment that 2245 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g. 2246 * 2247 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ... 2248 * p0 p1 p2 2249 * (now) (~1ms ago) (~2ms ago) 2250 * 2251 * Let u_i denote the fraction of p_i that the entity was runnable. 2252 * 2253 * We then designate the fractions u_i as our co-efficients, yielding the 2254 * following representation of historical load: 2255 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ... 2256 * 2257 * We choose y based on the with of a reasonably scheduling period, fixing: 2258 * y^32 = 0.5 2259 * 2260 * This means that the contribution to load ~32ms ago (u_32) will be weighted 2261 * approximately half as much as the contribution to load within the last ms 2262 * (u_0). 2263 * 2264 * When a period "rolls over" and we have new u_0`, multiplying the previous 2265 * sum again by y is sufficient to update: 2266 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) 2267 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] 2268 */ 2269 static __always_inline int __update_entity_runnable_avg(u64 now, 2270 struct sched_avg *sa, 2271 int runnable) 2272 { 2273 u64 delta, periods; 2274 u32 runnable_contrib; 2275 int delta_w, decayed = 0; 2276 2277 delta = now - sa->last_runnable_update; 2278 /* 2279 * This should only happen when time goes backwards, which it 2280 * unfortunately does during sched clock init when we swap over to TSC. 2281 */ 2282 if ((s64)delta < 0) { 2283 sa->last_runnable_update = now; 2284 return 0; 2285 } 2286 2287 /* 2288 * Use 1024ns as the unit of measurement since it's a reasonable 2289 * approximation of 1us and fast to compute. 2290 */ 2291 delta >>= 10; 2292 if (!delta) 2293 return 0; 2294 sa->last_runnable_update = now; 2295 2296 /* delta_w is the amount already accumulated against our next period */ 2297 delta_w = sa->runnable_avg_period % 1024; 2298 if (delta + delta_w >= 1024) { 2299 /* period roll-over */ 2300 decayed = 1; 2301 2302 /* 2303 * Now that we know we're crossing a period boundary, figure 2304 * out how much from delta we need to complete the current 2305 * period and accrue it. 2306 */ 2307 delta_w = 1024 - delta_w; 2308 if (runnable) 2309 sa->runnable_avg_sum += delta_w; 2310 sa->runnable_avg_period += delta_w; 2311 2312 delta -= delta_w; 2313 2314 /* Figure out how many additional periods this update spans */ 2315 periods = delta / 1024; 2316 delta %= 1024; 2317 2318 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum, 2319 periods + 1); 2320 sa->runnable_avg_period = decay_load(sa->runnable_avg_period, 2321 periods + 1); 2322 2323 /* Efficiently calculate \sum (1..n_period) 1024*y^i */ 2324 runnable_contrib = __compute_runnable_contrib(periods); 2325 if (runnable) 2326 sa->runnable_avg_sum += runnable_contrib; 2327 sa->runnable_avg_period += runnable_contrib; 2328 } 2329 2330 /* Remainder of delta accrued against u_0` */ 2331 if (runnable) 2332 sa->runnable_avg_sum += delta; 2333 sa->runnable_avg_period += delta; 2334 2335 return decayed; 2336 } 2337 2338 /* Synchronize an entity's decay with its parenting cfs_rq.*/ 2339 static inline u64 __synchronize_entity_decay(struct sched_entity *se) 2340 { 2341 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2342 u64 decays = atomic64_read(&cfs_rq->decay_counter); 2343 2344 decays -= se->avg.decay_count; 2345 if (!decays) 2346 return 0; 2347 2348 se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays); 2349 se->avg.decay_count = 0; 2350 2351 return decays; 2352 } 2353 2354 #ifdef CONFIG_FAIR_GROUP_SCHED 2355 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, 2356 int force_update) 2357 { 2358 struct task_group *tg = cfs_rq->tg; 2359 long tg_contrib; 2360 2361 tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; 2362 tg_contrib -= cfs_rq->tg_load_contrib; 2363 2364 if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) { 2365 atomic_long_add(tg_contrib, &tg->load_avg); 2366 cfs_rq->tg_load_contrib += tg_contrib; 2367 } 2368 } 2369 2370 /* 2371 * Aggregate cfs_rq runnable averages into an equivalent task_group 2372 * representation for computing load contributions. 2373 */ 2374 static inline void __update_tg_runnable_avg(struct sched_avg *sa, 2375 struct cfs_rq *cfs_rq) 2376 { 2377 struct task_group *tg = cfs_rq->tg; 2378 long contrib; 2379 2380 /* The fraction of a cpu used by this cfs_rq */ 2381 contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT, 2382 sa->runnable_avg_period + 1); 2383 contrib -= cfs_rq->tg_runnable_contrib; 2384 2385 if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) { 2386 atomic_add(contrib, &tg->runnable_avg); 2387 cfs_rq->tg_runnable_contrib += contrib; 2388 } 2389 } 2390 2391 static inline void __update_group_entity_contrib(struct sched_entity *se) 2392 { 2393 struct cfs_rq *cfs_rq = group_cfs_rq(se); 2394 struct task_group *tg = cfs_rq->tg; 2395 int runnable_avg; 2396 2397 u64 contrib; 2398 2399 contrib = cfs_rq->tg_load_contrib * tg->shares; 2400 se->avg.load_avg_contrib = div_u64(contrib, 2401 atomic_long_read(&tg->load_avg) + 1); 2402 2403 /* 2404 * For group entities we need to compute a correction term in the case 2405 * that they are consuming <1 cpu so that we would contribute the same 2406 * load as a task of equal weight. 2407 * 2408 * Explicitly co-ordinating this measurement would be expensive, but 2409 * fortunately the sum of each cpus contribution forms a usable 2410 * lower-bound on the true value. 2411 * 2412 * Consider the aggregate of 2 contributions. Either they are disjoint 2413 * (and the sum represents true value) or they are disjoint and we are 2414 * understating by the aggregate of their overlap. 2415 * 2416 * Extending this to N cpus, for a given overlap, the maximum amount we 2417 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of 2418 * cpus that overlap for this interval and w_i is the interval width. 2419 * 2420 * On a small machine; the first term is well-bounded which bounds the 2421 * total error since w_i is a subset of the period. Whereas on a 2422 * larger machine, while this first term can be larger, if w_i is the 2423 * of consequential size guaranteed to see n_i*w_i quickly converge to 2424 * our upper bound of 1-cpu. 2425 */ 2426 runnable_avg = atomic_read(&tg->runnable_avg); 2427 if (runnable_avg < NICE_0_LOAD) { 2428 se->avg.load_avg_contrib *= runnable_avg; 2429 se->avg.load_avg_contrib >>= NICE_0_SHIFT; 2430 } 2431 } 2432 2433 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) 2434 { 2435 __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable); 2436 __update_tg_runnable_avg(&rq->avg, &rq->cfs); 2437 } 2438 #else /* CONFIG_FAIR_GROUP_SCHED */ 2439 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, 2440 int force_update) {} 2441 static inline void __update_tg_runnable_avg(struct sched_avg *sa, 2442 struct cfs_rq *cfs_rq) {} 2443 static inline void __update_group_entity_contrib(struct sched_entity *se) {} 2444 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} 2445 #endif /* CONFIG_FAIR_GROUP_SCHED */ 2446 2447 static inline void __update_task_entity_contrib(struct sched_entity *se) 2448 { 2449 u32 contrib; 2450 2451 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ 2452 contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight); 2453 contrib /= (se->avg.runnable_avg_period + 1); 2454 se->avg.load_avg_contrib = scale_load(contrib); 2455 } 2456 2457 /* Compute the current contribution to load_avg by se, return any delta */ 2458 static long __update_entity_load_avg_contrib(struct sched_entity *se) 2459 { 2460 long old_contrib = se->avg.load_avg_contrib; 2461 2462 if (entity_is_task(se)) { 2463 __update_task_entity_contrib(se); 2464 } else { 2465 __update_tg_runnable_avg(&se->avg, group_cfs_rq(se)); 2466 __update_group_entity_contrib(se); 2467 } 2468 2469 return se->avg.load_avg_contrib - old_contrib; 2470 } 2471 2472 static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq, 2473 long load_contrib) 2474 { 2475 if (likely(load_contrib < cfs_rq->blocked_load_avg)) 2476 cfs_rq->blocked_load_avg -= load_contrib; 2477 else 2478 cfs_rq->blocked_load_avg = 0; 2479 } 2480 2481 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); 2482 2483 /* Update a sched_entity's runnable average */ 2484 static inline void update_entity_load_avg(struct sched_entity *se, 2485 int update_cfs_rq) 2486 { 2487 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2488 long contrib_delta; 2489 u64 now; 2490 2491 /* 2492 * For a group entity we need to use their owned cfs_rq_clock_task() in 2493 * case they are the parent of a throttled hierarchy. 2494 */ 2495 if (entity_is_task(se)) 2496 now = cfs_rq_clock_task(cfs_rq); 2497 else 2498 now = cfs_rq_clock_task(group_cfs_rq(se)); 2499 2500 if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq)) 2501 return; 2502 2503 contrib_delta = __update_entity_load_avg_contrib(se); 2504 2505 if (!update_cfs_rq) 2506 return; 2507 2508 if (se->on_rq) 2509 cfs_rq->runnable_load_avg += contrib_delta; 2510 else 2511 subtract_blocked_load_contrib(cfs_rq, -contrib_delta); 2512 } 2513 2514 /* 2515 * Decay the load contributed by all blocked children and account this so that 2516 * their contribution may appropriately discounted when they wake up. 2517 */ 2518 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update) 2519 { 2520 u64 now = cfs_rq_clock_task(cfs_rq) >> 20; 2521 u64 decays; 2522 2523 decays = now - cfs_rq->last_decay; 2524 if (!decays && !force_update) 2525 return; 2526 2527 if (atomic_long_read(&cfs_rq->removed_load)) { 2528 unsigned long removed_load; 2529 removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0); 2530 subtract_blocked_load_contrib(cfs_rq, removed_load); 2531 } 2532 2533 if (decays) { 2534 cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg, 2535 decays); 2536 atomic64_add(decays, &cfs_rq->decay_counter); 2537 cfs_rq->last_decay = now; 2538 } 2539 2540 __update_cfs_rq_tg_load_contrib(cfs_rq, force_update); 2541 } 2542 2543 /* Add the load generated by se into cfs_rq's child load-average */ 2544 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, 2545 struct sched_entity *se, 2546 int wakeup) 2547 { 2548 /* 2549 * We track migrations using entity decay_count <= 0, on a wake-up 2550 * migration we use a negative decay count to track the remote decays 2551 * accumulated while sleeping. 2552 * 2553 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they 2554 * are seen by enqueue_entity_load_avg() as a migration with an already 2555 * constructed load_avg_contrib. 2556 */ 2557 if (unlikely(se->avg.decay_count <= 0)) { 2558 se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq)); 2559 if (se->avg.decay_count) { 2560 /* 2561 * In a wake-up migration we have to approximate the 2562 * time sleeping. This is because we can't synchronize 2563 * clock_task between the two cpus, and it is not 2564 * guaranteed to be read-safe. Instead, we can 2565 * approximate this using our carried decays, which are 2566 * explicitly atomically readable. 2567 */ 2568 se->avg.last_runnable_update -= (-se->avg.decay_count) 2569 << 20; 2570 update_entity_load_avg(se, 0); 2571 /* Indicate that we're now synchronized and on-rq */ 2572 se->avg.decay_count = 0; 2573 } 2574 wakeup = 0; 2575 } else { 2576 __synchronize_entity_decay(se); 2577 } 2578 2579 /* migrated tasks did not contribute to our blocked load */ 2580 if (wakeup) { 2581 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); 2582 update_entity_load_avg(se, 0); 2583 } 2584 2585 cfs_rq->runnable_load_avg += se->avg.load_avg_contrib; 2586 /* we force update consideration on load-balancer moves */ 2587 update_cfs_rq_blocked_load(cfs_rq, !wakeup); 2588 } 2589 2590 /* 2591 * Remove se's load from this cfs_rq child load-average, if the entity is 2592 * transitioning to a blocked state we track its projected decay using 2593 * blocked_load_avg. 2594 */ 2595 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, 2596 struct sched_entity *se, 2597 int sleep) 2598 { 2599 update_entity_load_avg(se, 1); 2600 /* we force update consideration on load-balancer moves */ 2601 update_cfs_rq_blocked_load(cfs_rq, !sleep); 2602 2603 cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib; 2604 if (sleep) { 2605 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; 2606 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); 2607 } /* migrations, e.g. sleep=0 leave decay_count == 0 */ 2608 } 2609 2610 /* 2611 * Update the rq's load with the elapsed running time before entering 2612 * idle. if the last scheduled task is not a CFS task, idle_enter will 2613 * be the only way to update the runnable statistic. 2614 */ 2615 void idle_enter_fair(struct rq *this_rq) 2616 { 2617 update_rq_runnable_avg(this_rq, 1); 2618 } 2619 2620 /* 2621 * Update the rq's load with the elapsed idle time before a task is 2622 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will 2623 * be the only way to update the runnable statistic. 2624 */ 2625 void idle_exit_fair(struct rq *this_rq) 2626 { 2627 update_rq_runnable_avg(this_rq, 0); 2628 } 2629 2630 static int idle_balance(struct rq *this_rq); 2631 2632 #else /* CONFIG_SMP */ 2633 2634 static inline void update_entity_load_avg(struct sched_entity *se, 2635 int update_cfs_rq) {} 2636 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} 2637 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, 2638 struct sched_entity *se, 2639 int wakeup) {} 2640 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, 2641 struct sched_entity *se, 2642 int sleep) {} 2643 static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, 2644 int force_update) {} 2645 2646 static inline int idle_balance(struct rq *rq) 2647 { 2648 return 0; 2649 } 2650 2651 #endif /* CONFIG_SMP */ 2652 2653 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) 2654 { 2655 #ifdef CONFIG_SCHEDSTATS 2656 struct task_struct *tsk = NULL; 2657 2658 if (entity_is_task(se)) 2659 tsk = task_of(se); 2660 2661 if (se->statistics.sleep_start) { 2662 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start; 2663 2664 if ((s64)delta < 0) 2665 delta = 0; 2666 2667 if (unlikely(delta > se->statistics.sleep_max)) 2668 se->statistics.sleep_max = delta; 2669 2670 se->statistics.sleep_start = 0; 2671 se->statistics.sum_sleep_runtime += delta; 2672 2673 if (tsk) { 2674 account_scheduler_latency(tsk, delta >> 10, 1); 2675 trace_sched_stat_sleep(tsk, delta); 2676 } 2677 } 2678 if (se->statistics.block_start) { 2679 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start; 2680 2681 if ((s64)delta < 0) 2682 delta = 0; 2683 2684 if (unlikely(delta > se->statistics.block_max)) 2685 se->statistics.block_max = delta; 2686 2687 se->statistics.block_start = 0; 2688 se->statistics.sum_sleep_runtime += delta; 2689 2690 if (tsk) { 2691 if (tsk->in_iowait) { 2692 se->statistics.iowait_sum += delta; 2693 se->statistics.iowait_count++; 2694 trace_sched_stat_iowait(tsk, delta); 2695 } 2696 2697 trace_sched_stat_blocked(tsk, delta); 2698 2699 /* 2700 * Blocking time is in units of nanosecs, so shift by 2701 * 20 to get a milliseconds-range estimation of the 2702 * amount of time that the task spent sleeping: 2703 */ 2704 if (unlikely(prof_on == SLEEP_PROFILING)) { 2705 profile_hits(SLEEP_PROFILING, 2706 (void *)get_wchan(tsk), 2707 delta >> 20); 2708 } 2709 account_scheduler_latency(tsk, delta >> 10, 0); 2710 } 2711 } 2712 #endif 2713 } 2714 2715 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) 2716 { 2717 #ifdef CONFIG_SCHED_DEBUG 2718 s64 d = se->vruntime - cfs_rq->min_vruntime; 2719 2720 if (d < 0) 2721 d = -d; 2722 2723 if (d > 3*sysctl_sched_latency) 2724 schedstat_inc(cfs_rq, nr_spread_over); 2725 #endif 2726 } 2727 2728 static void 2729 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 2730 { 2731 u64 vruntime = cfs_rq->min_vruntime; 2732 2733 /* 2734 * The 'current' period is already promised to the current tasks, 2735 * however the extra weight of the new task will slow them down a 2736 * little, place the new task so that it fits in the slot that 2737 * stays open at the end. 2738 */ 2739 if (initial && sched_feat(START_DEBIT)) 2740 vruntime += sched_vslice(cfs_rq, se); 2741 2742 /* sleeps up to a single latency don't count. */ 2743 if (!initial) { 2744 unsigned long thresh = sysctl_sched_latency; 2745 2746 /* 2747 * Halve their sleep time's effect, to allow 2748 * for a gentler effect of sleepers: 2749 */ 2750 if (sched_feat(GENTLE_FAIR_SLEEPERS)) 2751 thresh >>= 1; 2752 2753 vruntime -= thresh; 2754 } 2755 2756 /* ensure we never gain time by being placed backwards. */ 2757 se->vruntime = max_vruntime(se->vruntime, vruntime); 2758 } 2759 2760 static void check_enqueue_throttle(struct cfs_rq *cfs_rq); 2761 2762 static void 2763 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 2764 { 2765 /* 2766 * Update the normalized vruntime before updating min_vruntime 2767 * through calling update_curr(). 2768 */ 2769 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) 2770 se->vruntime += cfs_rq->min_vruntime; 2771 2772 /* 2773 * Update run-time statistics of the 'current'. 2774 */ 2775 update_curr(cfs_rq); 2776 enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP); 2777 account_entity_enqueue(cfs_rq, se); 2778 update_cfs_shares(cfs_rq); 2779 2780 if (flags & ENQUEUE_WAKEUP) { 2781 place_entity(cfs_rq, se, 0); 2782 enqueue_sleeper(cfs_rq, se); 2783 } 2784 2785 update_stats_enqueue(cfs_rq, se); 2786 check_spread(cfs_rq, se); 2787 if (se != cfs_rq->curr) 2788 __enqueue_entity(cfs_rq, se); 2789 se->on_rq = 1; 2790 2791 if (cfs_rq->nr_running == 1) { 2792 list_add_leaf_cfs_rq(cfs_rq); 2793 check_enqueue_throttle(cfs_rq); 2794 } 2795 } 2796 2797 static void __clear_buddies_last(struct sched_entity *se) 2798 { 2799 for_each_sched_entity(se) { 2800 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2801 if (cfs_rq->last != se) 2802 break; 2803 2804 cfs_rq->last = NULL; 2805 } 2806 } 2807 2808 static void __clear_buddies_next(struct sched_entity *se) 2809 { 2810 for_each_sched_entity(se) { 2811 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2812 if (cfs_rq->next != se) 2813 break; 2814 2815 cfs_rq->next = NULL; 2816 } 2817 } 2818 2819 static void __clear_buddies_skip(struct sched_entity *se) 2820 { 2821 for_each_sched_entity(se) { 2822 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2823 if (cfs_rq->skip != se) 2824 break; 2825 2826 cfs_rq->skip = NULL; 2827 } 2828 } 2829 2830 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) 2831 { 2832 if (cfs_rq->last == se) 2833 __clear_buddies_last(se); 2834 2835 if (cfs_rq->next == se) 2836 __clear_buddies_next(se); 2837 2838 if (cfs_rq->skip == se) 2839 __clear_buddies_skip(se); 2840 } 2841 2842 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); 2843 2844 static void 2845 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 2846 { 2847 /* 2848 * Update run-time statistics of the 'current'. 2849 */ 2850 update_curr(cfs_rq); 2851 dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP); 2852 2853 update_stats_dequeue(cfs_rq, se); 2854 if (flags & DEQUEUE_SLEEP) { 2855 #ifdef CONFIG_SCHEDSTATS 2856 if (entity_is_task(se)) { 2857 struct task_struct *tsk = task_of(se); 2858 2859 if (tsk->state & TASK_INTERRUPTIBLE) 2860 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq)); 2861 if (tsk->state & TASK_UNINTERRUPTIBLE) 2862 se->statistics.block_start = rq_clock(rq_of(cfs_rq)); 2863 } 2864 #endif 2865 } 2866 2867 clear_buddies(cfs_rq, se); 2868 2869 if (se != cfs_rq->curr) 2870 __dequeue_entity(cfs_rq, se); 2871 se->on_rq = 0; 2872 account_entity_dequeue(cfs_rq, se); 2873 2874 /* 2875 * Normalize the entity after updating the min_vruntime because the 2876 * update can refer to the ->curr item and we need to reflect this 2877 * movement in our normalized position. 2878 */ 2879 if (!(flags & DEQUEUE_SLEEP)) 2880 se->vruntime -= cfs_rq->min_vruntime; 2881 2882 /* return excess runtime on last dequeue */ 2883 return_cfs_rq_runtime(cfs_rq); 2884 2885 update_min_vruntime(cfs_rq); 2886 update_cfs_shares(cfs_rq); 2887 } 2888 2889 /* 2890 * Preempt the current task with a newly woken task if needed: 2891 */ 2892 static void 2893 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 2894 { 2895 unsigned long ideal_runtime, delta_exec; 2896 struct sched_entity *se; 2897 s64 delta; 2898 2899 ideal_runtime = sched_slice(cfs_rq, curr); 2900 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; 2901 if (delta_exec > ideal_runtime) { 2902 resched_task(rq_of(cfs_rq)->curr); 2903 /* 2904 * The current task ran long enough, ensure it doesn't get 2905 * re-elected due to buddy favours. 2906 */ 2907 clear_buddies(cfs_rq, curr); 2908 return; 2909 } 2910 2911 /* 2912 * Ensure that a task that missed wakeup preemption by a 2913 * narrow margin doesn't have to wait for a full slice. 2914 * This also mitigates buddy induced latencies under load. 2915 */ 2916 if (delta_exec < sysctl_sched_min_granularity) 2917 return; 2918 2919 se = __pick_first_entity(cfs_rq); 2920 delta = curr->vruntime - se->vruntime; 2921 2922 if (delta < 0) 2923 return; 2924 2925 if (delta > ideal_runtime) 2926 resched_task(rq_of(cfs_rq)->curr); 2927 } 2928 2929 static void 2930 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 2931 { 2932 /* 'current' is not kept within the tree. */ 2933 if (se->on_rq) { 2934 /* 2935 * Any task has to be enqueued before it get to execute on 2936 * a CPU. So account for the time it spent waiting on the 2937 * runqueue. 2938 */ 2939 update_stats_wait_end(cfs_rq, se); 2940 __dequeue_entity(cfs_rq, se); 2941 } 2942 2943 update_stats_curr_start(cfs_rq, se); 2944 cfs_rq->curr = se; 2945 #ifdef CONFIG_SCHEDSTATS 2946 /* 2947 * Track our maximum slice length, if the CPU's load is at 2948 * least twice that of our own weight (i.e. dont track it 2949 * when there are only lesser-weight tasks around): 2950 */ 2951 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { 2952 se->statistics.slice_max = max(se->statistics.slice_max, 2953 se->sum_exec_runtime - se->prev_sum_exec_runtime); 2954 } 2955 #endif 2956 se->prev_sum_exec_runtime = se->sum_exec_runtime; 2957 } 2958 2959 static int 2960 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); 2961 2962 /* 2963 * Pick the next process, keeping these things in mind, in this order: 2964 * 1) keep things fair between processes/task groups 2965 * 2) pick the "next" process, since someone really wants that to run 2966 * 3) pick the "last" process, for cache locality 2967 * 4) do not run the "skip" process, if something else is available 2968 */ 2969 static struct sched_entity * 2970 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) 2971 { 2972 struct sched_entity *left = __pick_first_entity(cfs_rq); 2973 struct sched_entity *se; 2974 2975 /* 2976 * If curr is set we have to see if its left of the leftmost entity 2977 * still in the tree, provided there was anything in the tree at all. 2978 */ 2979 if (!left || (curr && entity_before(curr, left))) 2980 left = curr; 2981 2982 se = left; /* ideally we run the leftmost entity */ 2983 2984 /* 2985 * Avoid running the skip buddy, if running something else can 2986 * be done without getting too unfair. 2987 */ 2988 if (cfs_rq->skip == se) { 2989 struct sched_entity *second; 2990 2991 if (se == curr) { 2992 second = __pick_first_entity(cfs_rq); 2993 } else { 2994 second = __pick_next_entity(se); 2995 if (!second || (curr && entity_before(curr, second))) 2996 second = curr; 2997 } 2998 2999 if (second && wakeup_preempt_entity(second, left) < 1) 3000 se = second; 3001 } 3002 3003 /* 3004 * Prefer last buddy, try to return the CPU to a preempted task. 3005 */ 3006 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) 3007 se = cfs_rq->last; 3008 3009 /* 3010 * Someone really wants this to run. If it's not unfair, run it. 3011 */ 3012 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) 3013 se = cfs_rq->next; 3014 3015 clear_buddies(cfs_rq, se); 3016 3017 return se; 3018 } 3019 3020 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); 3021 3022 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) 3023 { 3024 /* 3025 * If still on the runqueue then deactivate_task() 3026 * was not called and update_curr() has to be done: 3027 */ 3028 if (prev->on_rq) 3029 update_curr(cfs_rq); 3030 3031 /* throttle cfs_rqs exceeding runtime */ 3032 check_cfs_rq_runtime(cfs_rq); 3033 3034 check_spread(cfs_rq, prev); 3035 if (prev->on_rq) { 3036 update_stats_wait_start(cfs_rq, prev); 3037 /* Put 'current' back into the tree. */ 3038 __enqueue_entity(cfs_rq, prev); 3039 /* in !on_rq case, update occurred at dequeue */ 3040 update_entity_load_avg(prev, 1); 3041 } 3042 cfs_rq->curr = NULL; 3043 } 3044 3045 static void 3046 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) 3047 { 3048 /* 3049 * Update run-time statistics of the 'current'. 3050 */ 3051 update_curr(cfs_rq); 3052 3053 /* 3054 * Ensure that runnable average is periodically updated. 3055 */ 3056 update_entity_load_avg(curr, 1); 3057 update_cfs_rq_blocked_load(cfs_rq, 1); 3058 update_cfs_shares(cfs_rq); 3059 3060 #ifdef CONFIG_SCHED_HRTICK 3061 /* 3062 * queued ticks are scheduled to match the slice, so don't bother 3063 * validating it and just reschedule. 3064 */ 3065 if (queued) { 3066 resched_task(rq_of(cfs_rq)->curr); 3067 return; 3068 } 3069 /* 3070 * don't let the period tick interfere with the hrtick preemption 3071 */ 3072 if (!sched_feat(DOUBLE_TICK) && 3073 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) 3074 return; 3075 #endif 3076 3077 if (cfs_rq->nr_running > 1) 3078 check_preempt_tick(cfs_rq, curr); 3079 } 3080 3081 3082 /************************************************** 3083 * CFS bandwidth control machinery 3084 */ 3085 3086 #ifdef CONFIG_CFS_BANDWIDTH 3087 3088 #ifdef HAVE_JUMP_LABEL 3089 static struct static_key __cfs_bandwidth_used; 3090 3091 static inline bool cfs_bandwidth_used(void) 3092 { 3093 return static_key_false(&__cfs_bandwidth_used); 3094 } 3095 3096 void cfs_bandwidth_usage_inc(void) 3097 { 3098 static_key_slow_inc(&__cfs_bandwidth_used); 3099 } 3100 3101 void cfs_bandwidth_usage_dec(void) 3102 { 3103 static_key_slow_dec(&__cfs_bandwidth_used); 3104 } 3105 #else /* HAVE_JUMP_LABEL */ 3106 static bool cfs_bandwidth_used(void) 3107 { 3108 return true; 3109 } 3110 3111 void cfs_bandwidth_usage_inc(void) {} 3112 void cfs_bandwidth_usage_dec(void) {} 3113 #endif /* HAVE_JUMP_LABEL */ 3114 3115 /* 3116 * default period for cfs group bandwidth. 3117 * default: 0.1s, units: nanoseconds 3118 */ 3119 static inline u64 default_cfs_period(void) 3120 { 3121 return 100000000ULL; 3122 } 3123 3124 static inline u64 sched_cfs_bandwidth_slice(void) 3125 { 3126 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; 3127 } 3128 3129 /* 3130 * Replenish runtime according to assigned quota and update expiration time. 3131 * We use sched_clock_cpu directly instead of rq->clock to avoid adding 3132 * additional synchronization around rq->lock. 3133 * 3134 * requires cfs_b->lock 3135 */ 3136 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) 3137 { 3138 u64 now; 3139 3140 if (cfs_b->quota == RUNTIME_INF) 3141 return; 3142 3143 now = sched_clock_cpu(smp_processor_id()); 3144 cfs_b->runtime = cfs_b->quota; 3145 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); 3146 } 3147 3148 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 3149 { 3150 return &tg->cfs_bandwidth; 3151 } 3152 3153 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */ 3154 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 3155 { 3156 if (unlikely(cfs_rq->throttle_count)) 3157 return cfs_rq->throttled_clock_task; 3158 3159 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; 3160 } 3161 3162 /* returns 0 on failure to allocate runtime */ 3163 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3164 { 3165 struct task_group *tg = cfs_rq->tg; 3166 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); 3167 u64 amount = 0, min_amount, expires; 3168 3169 /* note: this is a positive sum as runtime_remaining <= 0 */ 3170 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; 3171 3172 raw_spin_lock(&cfs_b->lock); 3173 if (cfs_b->quota == RUNTIME_INF) 3174 amount = min_amount; 3175 else { 3176 /* 3177 * If the bandwidth pool has become inactive, then at least one 3178 * period must have elapsed since the last consumption. 3179 * Refresh the global state and ensure bandwidth timer becomes 3180 * active. 3181 */ 3182 if (!cfs_b->timer_active) { 3183 __refill_cfs_bandwidth_runtime(cfs_b); 3184 __start_cfs_bandwidth(cfs_b, false); 3185 } 3186 3187 if (cfs_b->runtime > 0) { 3188 amount = min(cfs_b->runtime, min_amount); 3189 cfs_b->runtime -= amount; 3190 cfs_b->idle = 0; 3191 } 3192 } 3193 expires = cfs_b->runtime_expires; 3194 raw_spin_unlock(&cfs_b->lock); 3195 3196 cfs_rq->runtime_remaining += amount; 3197 /* 3198 * we may have advanced our local expiration to account for allowed 3199 * spread between our sched_clock and the one on which runtime was 3200 * issued. 3201 */ 3202 if ((s64)(expires - cfs_rq->runtime_expires) > 0) 3203 cfs_rq->runtime_expires = expires; 3204 3205 return cfs_rq->runtime_remaining > 0; 3206 } 3207 3208 /* 3209 * Note: This depends on the synchronization provided by sched_clock and the 3210 * fact that rq->clock snapshots this value. 3211 */ 3212 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3213 { 3214 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3215 3216 /* if the deadline is ahead of our clock, nothing to do */ 3217 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0)) 3218 return; 3219 3220 if (cfs_rq->runtime_remaining < 0) 3221 return; 3222 3223 /* 3224 * If the local deadline has passed we have to consider the 3225 * possibility that our sched_clock is 'fast' and the global deadline 3226 * has not truly expired. 3227 * 3228 * Fortunately we can check determine whether this the case by checking 3229 * whether the global deadline has advanced. It is valid to compare 3230 * cfs_b->runtime_expires without any locks since we only care about 3231 * exact equality, so a partial write will still work. 3232 */ 3233 3234 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) { 3235 /* extend local deadline, drift is bounded above by 2 ticks */ 3236 cfs_rq->runtime_expires += TICK_NSEC; 3237 } else { 3238 /* global deadline is ahead, expiration has passed */ 3239 cfs_rq->runtime_remaining = 0; 3240 } 3241 } 3242 3243 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 3244 { 3245 /* dock delta_exec before expiring quota (as it could span periods) */ 3246 cfs_rq->runtime_remaining -= delta_exec; 3247 expire_cfs_rq_runtime(cfs_rq); 3248 3249 if (likely(cfs_rq->runtime_remaining > 0)) 3250 return; 3251 3252 /* 3253 * if we're unable to extend our runtime we resched so that the active 3254 * hierarchy can be throttled 3255 */ 3256 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) 3257 resched_task(rq_of(cfs_rq)->curr); 3258 } 3259 3260 static __always_inline 3261 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 3262 { 3263 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) 3264 return; 3265 3266 __account_cfs_rq_runtime(cfs_rq, delta_exec); 3267 } 3268 3269 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 3270 { 3271 return cfs_bandwidth_used() && cfs_rq->throttled; 3272 } 3273 3274 /* check whether cfs_rq, or any parent, is throttled */ 3275 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 3276 { 3277 return cfs_bandwidth_used() && cfs_rq->throttle_count; 3278 } 3279 3280 /* 3281 * Ensure that neither of the group entities corresponding to src_cpu or 3282 * dest_cpu are members of a throttled hierarchy when performing group 3283 * load-balance operations. 3284 */ 3285 static inline int throttled_lb_pair(struct task_group *tg, 3286 int src_cpu, int dest_cpu) 3287 { 3288 struct cfs_rq *src_cfs_rq, *dest_cfs_rq; 3289 3290 src_cfs_rq = tg->cfs_rq[src_cpu]; 3291 dest_cfs_rq = tg->cfs_rq[dest_cpu]; 3292 3293 return throttled_hierarchy(src_cfs_rq) || 3294 throttled_hierarchy(dest_cfs_rq); 3295 } 3296 3297 /* updated child weight may affect parent so we have to do this bottom up */ 3298 static int tg_unthrottle_up(struct task_group *tg, void *data) 3299 { 3300 struct rq *rq = data; 3301 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 3302 3303 cfs_rq->throttle_count--; 3304 #ifdef CONFIG_SMP 3305 if (!cfs_rq->throttle_count) { 3306 /* adjust cfs_rq_clock_task() */ 3307 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - 3308 cfs_rq->throttled_clock_task; 3309 } 3310 #endif 3311 3312 return 0; 3313 } 3314 3315 static int tg_throttle_down(struct task_group *tg, void *data) 3316 { 3317 struct rq *rq = data; 3318 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 3319 3320 /* group is entering throttled state, stop time */ 3321 if (!cfs_rq->throttle_count) 3322 cfs_rq->throttled_clock_task = rq_clock_task(rq); 3323 cfs_rq->throttle_count++; 3324 3325 return 0; 3326 } 3327 3328 static void throttle_cfs_rq(struct cfs_rq *cfs_rq) 3329 { 3330 struct rq *rq = rq_of(cfs_rq); 3331 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3332 struct sched_entity *se; 3333 long task_delta, dequeue = 1; 3334 3335 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; 3336 3337 /* freeze hierarchy runnable averages while throttled */ 3338 rcu_read_lock(); 3339 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); 3340 rcu_read_unlock(); 3341 3342 task_delta = cfs_rq->h_nr_running; 3343 for_each_sched_entity(se) { 3344 struct cfs_rq *qcfs_rq = cfs_rq_of(se); 3345 /* throttled entity or throttle-on-deactivate */ 3346 if (!se->on_rq) 3347 break; 3348 3349 if (dequeue) 3350 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); 3351 qcfs_rq->h_nr_running -= task_delta; 3352 3353 if (qcfs_rq->load.weight) 3354 dequeue = 0; 3355 } 3356 3357 if (!se) 3358 sub_nr_running(rq, task_delta); 3359 3360 cfs_rq->throttled = 1; 3361 cfs_rq->throttled_clock = rq_clock(rq); 3362 raw_spin_lock(&cfs_b->lock); 3363 list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); 3364 if (!cfs_b->timer_active) 3365 __start_cfs_bandwidth(cfs_b, false); 3366 raw_spin_unlock(&cfs_b->lock); 3367 } 3368 3369 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 3370 { 3371 struct rq *rq = rq_of(cfs_rq); 3372 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3373 struct sched_entity *se; 3374 int enqueue = 1; 3375 long task_delta; 3376 3377 se = cfs_rq->tg->se[cpu_of(rq)]; 3378 3379 cfs_rq->throttled = 0; 3380 3381 update_rq_clock(rq); 3382 3383 raw_spin_lock(&cfs_b->lock); 3384 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; 3385 list_del_rcu(&cfs_rq->throttled_list); 3386 raw_spin_unlock(&cfs_b->lock); 3387 3388 /* update hierarchical throttle state */ 3389 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); 3390 3391 if (!cfs_rq->load.weight) 3392 return; 3393 3394 task_delta = cfs_rq->h_nr_running; 3395 for_each_sched_entity(se) { 3396 if (se->on_rq) 3397 enqueue = 0; 3398 3399 cfs_rq = cfs_rq_of(se); 3400 if (enqueue) 3401 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); 3402 cfs_rq->h_nr_running += task_delta; 3403 3404 if (cfs_rq_throttled(cfs_rq)) 3405 break; 3406 } 3407 3408 if (!se) 3409 add_nr_running(rq, task_delta); 3410 3411 /* determine whether we need to wake up potentially idle cpu */ 3412 if (rq->curr == rq->idle && rq->cfs.nr_running) 3413 resched_task(rq->curr); 3414 } 3415 3416 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, 3417 u64 remaining, u64 expires) 3418 { 3419 struct cfs_rq *cfs_rq; 3420 u64 runtime = remaining; 3421 3422 rcu_read_lock(); 3423 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, 3424 throttled_list) { 3425 struct rq *rq = rq_of(cfs_rq); 3426 3427 raw_spin_lock(&rq->lock); 3428 if (!cfs_rq_throttled(cfs_rq)) 3429 goto next; 3430 3431 runtime = -cfs_rq->runtime_remaining + 1; 3432 if (runtime > remaining) 3433 runtime = remaining; 3434 remaining -= runtime; 3435 3436 cfs_rq->runtime_remaining += runtime; 3437 cfs_rq->runtime_expires = expires; 3438 3439 /* we check whether we're throttled above */ 3440 if (cfs_rq->runtime_remaining > 0) 3441 unthrottle_cfs_rq(cfs_rq); 3442 3443 next: 3444 raw_spin_unlock(&rq->lock); 3445 3446 if (!remaining) 3447 break; 3448 } 3449 rcu_read_unlock(); 3450 3451 return remaining; 3452 } 3453 3454 /* 3455 * Responsible for refilling a task_group's bandwidth and unthrottling its 3456 * cfs_rqs as appropriate. If there has been no activity within the last 3457 * period the timer is deactivated until scheduling resumes; cfs_b->idle is 3458 * used to track this state. 3459 */ 3460 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) 3461 { 3462 u64 runtime, runtime_expires; 3463 int throttled; 3464 3465 /* no need to continue the timer with no bandwidth constraint */ 3466 if (cfs_b->quota == RUNTIME_INF) 3467 goto out_deactivate; 3468 3469 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 3470 cfs_b->nr_periods += overrun; 3471 3472 /* 3473 * idle depends on !throttled (for the case of a large deficit), and if 3474 * we're going inactive then everything else can be deferred 3475 */ 3476 if (cfs_b->idle && !throttled) 3477 goto out_deactivate; 3478 3479 /* 3480 * if we have relooped after returning idle once, we need to update our 3481 * status as actually running, so that other cpus doing 3482 * __start_cfs_bandwidth will stop trying to cancel us. 3483 */ 3484 cfs_b->timer_active = 1; 3485 3486 __refill_cfs_bandwidth_runtime(cfs_b); 3487 3488 if (!throttled) { 3489 /* mark as potentially idle for the upcoming period */ 3490 cfs_b->idle = 1; 3491 return 0; 3492 } 3493 3494 /* account preceding periods in which throttling occurred */ 3495 cfs_b->nr_throttled += overrun; 3496 3497 /* 3498 * There are throttled entities so we must first use the new bandwidth 3499 * to unthrottle them before making it generally available. This 3500 * ensures that all existing debts will be paid before a new cfs_rq is 3501 * allowed to run. 3502 */ 3503 runtime = cfs_b->runtime; 3504 runtime_expires = cfs_b->runtime_expires; 3505 cfs_b->runtime = 0; 3506 3507 /* 3508 * This check is repeated as we are holding onto the new bandwidth 3509 * while we unthrottle. This can potentially race with an unthrottled 3510 * group trying to acquire new bandwidth from the global pool. 3511 */ 3512 while (throttled && runtime > 0) { 3513 raw_spin_unlock(&cfs_b->lock); 3514 /* we can't nest cfs_b->lock while distributing bandwidth */ 3515 runtime = distribute_cfs_runtime(cfs_b, runtime, 3516 runtime_expires); 3517 raw_spin_lock(&cfs_b->lock); 3518 3519 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 3520 } 3521 3522 /* return (any) remaining runtime */ 3523 cfs_b->runtime = runtime; 3524 /* 3525 * While we are ensured activity in the period following an 3526 * unthrottle, this also covers the case in which the new bandwidth is 3527 * insufficient to cover the existing bandwidth deficit. (Forcing the 3528 * timer to remain active while there are any throttled entities.) 3529 */ 3530 cfs_b->idle = 0; 3531 3532 return 0; 3533 3534 out_deactivate: 3535 cfs_b->timer_active = 0; 3536 return 1; 3537 } 3538 3539 /* a cfs_rq won't donate quota below this amount */ 3540 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; 3541 /* minimum remaining period time to redistribute slack quota */ 3542 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; 3543 /* how long we wait to gather additional slack before distributing */ 3544 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; 3545 3546 /* 3547 * Are we near the end of the current quota period? 3548 * 3549 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the 3550 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of 3551 * migrate_hrtimers, base is never cleared, so we are fine. 3552 */ 3553 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) 3554 { 3555 struct hrtimer *refresh_timer = &cfs_b->period_timer; 3556 u64 remaining; 3557 3558 /* if the call-back is running a quota refresh is already occurring */ 3559 if (hrtimer_callback_running(refresh_timer)) 3560 return 1; 3561 3562 /* is a quota refresh about to occur? */ 3563 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); 3564 if (remaining < min_expire) 3565 return 1; 3566 3567 return 0; 3568 } 3569 3570 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) 3571 { 3572 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; 3573 3574 /* if there's a quota refresh soon don't bother with slack */ 3575 if (runtime_refresh_within(cfs_b, min_left)) 3576 return; 3577 3578 start_bandwidth_timer(&cfs_b->slack_timer, 3579 ns_to_ktime(cfs_bandwidth_slack_period)); 3580 } 3581 3582 /* we know any runtime found here is valid as update_curr() precedes return */ 3583 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3584 { 3585 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3586 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; 3587 3588 if (slack_runtime <= 0) 3589 return; 3590 3591 raw_spin_lock(&cfs_b->lock); 3592 if (cfs_b->quota != RUNTIME_INF && 3593 cfs_rq->runtime_expires == cfs_b->runtime_expires) { 3594 cfs_b->runtime += slack_runtime; 3595 3596 /* we are under rq->lock, defer unthrottling using a timer */ 3597 if (cfs_b->runtime > sched_cfs_bandwidth_slice() && 3598 !list_empty(&cfs_b->throttled_cfs_rq)) 3599 start_cfs_slack_bandwidth(cfs_b); 3600 } 3601 raw_spin_unlock(&cfs_b->lock); 3602 3603 /* even if it's not valid for return we don't want to try again */ 3604 cfs_rq->runtime_remaining -= slack_runtime; 3605 } 3606 3607 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3608 { 3609 if (!cfs_bandwidth_used()) 3610 return; 3611 3612 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) 3613 return; 3614 3615 __return_cfs_rq_runtime(cfs_rq); 3616 } 3617 3618 /* 3619 * This is done with a timer (instead of inline with bandwidth return) since 3620 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. 3621 */ 3622 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) 3623 { 3624 u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); 3625 u64 expires; 3626 3627 /* confirm we're still not at a refresh boundary */ 3628 raw_spin_lock(&cfs_b->lock); 3629 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { 3630 raw_spin_unlock(&cfs_b->lock); 3631 return; 3632 } 3633 3634 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) { 3635 runtime = cfs_b->runtime; 3636 cfs_b->runtime = 0; 3637 } 3638 expires = cfs_b->runtime_expires; 3639 raw_spin_unlock(&cfs_b->lock); 3640 3641 if (!runtime) 3642 return; 3643 3644 runtime = distribute_cfs_runtime(cfs_b, runtime, expires); 3645 3646 raw_spin_lock(&cfs_b->lock); 3647 if (expires == cfs_b->runtime_expires) 3648 cfs_b->runtime = runtime; 3649 raw_spin_unlock(&cfs_b->lock); 3650 } 3651 3652 /* 3653 * When a group wakes up we want to make sure that its quota is not already 3654 * expired/exceeded, otherwise it may be allowed to steal additional ticks of 3655 * runtime as update_curr() throttling can not not trigger until it's on-rq. 3656 */ 3657 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) 3658 { 3659 if (!cfs_bandwidth_used()) 3660 return; 3661 3662 /* an active group must be handled by the update_curr()->put() path */ 3663 if (!cfs_rq->runtime_enabled || cfs_rq->curr) 3664 return; 3665 3666 /* ensure the group is not already throttled */ 3667 if (cfs_rq_throttled(cfs_rq)) 3668 return; 3669 3670 /* update runtime allocation */ 3671 account_cfs_rq_runtime(cfs_rq, 0); 3672 if (cfs_rq->runtime_remaining <= 0) 3673 throttle_cfs_rq(cfs_rq); 3674 } 3675 3676 /* conditionally throttle active cfs_rq's from put_prev_entity() */ 3677 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3678 { 3679 if (!cfs_bandwidth_used()) 3680 return false; 3681 3682 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) 3683 return false; 3684 3685 /* 3686 * it's possible for a throttled entity to be forced into a running 3687 * state (e.g. set_curr_task), in this case we're finished. 3688 */ 3689 if (cfs_rq_throttled(cfs_rq)) 3690 return true; 3691 3692 throttle_cfs_rq(cfs_rq); 3693 return true; 3694 } 3695 3696 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) 3697 { 3698 struct cfs_bandwidth *cfs_b = 3699 container_of(timer, struct cfs_bandwidth, slack_timer); 3700 do_sched_cfs_slack_timer(cfs_b); 3701 3702 return HRTIMER_NORESTART; 3703 } 3704 3705 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 3706 { 3707 struct cfs_bandwidth *cfs_b = 3708 container_of(timer, struct cfs_bandwidth, period_timer); 3709 ktime_t now; 3710 int overrun; 3711 int idle = 0; 3712 3713 raw_spin_lock(&cfs_b->lock); 3714 for (;;) { 3715 now = hrtimer_cb_get_time(timer); 3716 overrun = hrtimer_forward(timer, now, cfs_b->period); 3717 3718 if (!overrun) 3719 break; 3720 3721 idle = do_sched_cfs_period_timer(cfs_b, overrun); 3722 } 3723 raw_spin_unlock(&cfs_b->lock); 3724 3725 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 3726 } 3727 3728 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 3729 { 3730 raw_spin_lock_init(&cfs_b->lock); 3731 cfs_b->runtime = 0; 3732 cfs_b->quota = RUNTIME_INF; 3733 cfs_b->period = ns_to_ktime(default_cfs_period()); 3734 3735 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); 3736 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 3737 cfs_b->period_timer.function = sched_cfs_period_timer; 3738 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 3739 cfs_b->slack_timer.function = sched_cfs_slack_timer; 3740 } 3741 3742 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3743 { 3744 cfs_rq->runtime_enabled = 0; 3745 INIT_LIST_HEAD(&cfs_rq->throttled_list); 3746 } 3747 3748 /* requires cfs_b->lock, may release to reprogram timer */ 3749 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force) 3750 { 3751 /* 3752 * The timer may be active because we're trying to set a new bandwidth 3753 * period or because we're racing with the tear-down path 3754 * (timer_active==0 becomes visible before the hrtimer call-back 3755 * terminates). In either case we ensure that it's re-programmed 3756 */ 3757 while (unlikely(hrtimer_active(&cfs_b->period_timer)) && 3758 hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) { 3759 /* bounce the lock to allow do_sched_cfs_period_timer to run */ 3760 raw_spin_unlock(&cfs_b->lock); 3761 cpu_relax(); 3762 raw_spin_lock(&cfs_b->lock); 3763 /* if someone else restarted the timer then we're done */ 3764 if (!force && cfs_b->timer_active) 3765 return; 3766 } 3767 3768 cfs_b->timer_active = 1; 3769 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period); 3770 } 3771 3772 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 3773 { 3774 hrtimer_cancel(&cfs_b->period_timer); 3775 hrtimer_cancel(&cfs_b->slack_timer); 3776 } 3777 3778 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) 3779 { 3780 struct cfs_rq *cfs_rq; 3781 3782 for_each_leaf_cfs_rq(rq, cfs_rq) { 3783 if (!cfs_rq->runtime_enabled) 3784 continue; 3785 3786 /* 3787 * clock_task is not advancing so we just need to make sure 3788 * there's some valid quota amount 3789 */ 3790 cfs_rq->runtime_remaining = 1; 3791 if (cfs_rq_throttled(cfs_rq)) 3792 unthrottle_cfs_rq(cfs_rq); 3793 } 3794 } 3795 3796 #else /* CONFIG_CFS_BANDWIDTH */ 3797 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 3798 { 3799 return rq_clock_task(rq_of(cfs_rq)); 3800 } 3801 3802 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} 3803 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } 3804 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} 3805 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 3806 3807 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 3808 { 3809 return 0; 3810 } 3811 3812 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 3813 { 3814 return 0; 3815 } 3816 3817 static inline int throttled_lb_pair(struct task_group *tg, 3818 int src_cpu, int dest_cpu) 3819 { 3820 return 0; 3821 } 3822 3823 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 3824 3825 #ifdef CONFIG_FAIR_GROUP_SCHED 3826 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 3827 #endif 3828 3829 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 3830 { 3831 return NULL; 3832 } 3833 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 3834 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} 3835 3836 #endif /* CONFIG_CFS_BANDWIDTH */ 3837 3838 /************************************************** 3839 * CFS operations on tasks: 3840 */ 3841 3842 #ifdef CONFIG_SCHED_HRTICK 3843 static void hrtick_start_fair(struct rq *rq, struct task_struct *p) 3844 { 3845 struct sched_entity *se = &p->se; 3846 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3847 3848 WARN_ON(task_rq(p) != rq); 3849 3850 if (cfs_rq->nr_running > 1) { 3851 u64 slice = sched_slice(cfs_rq, se); 3852 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; 3853 s64 delta = slice - ran; 3854 3855 if (delta < 0) { 3856 if (rq->curr == p) 3857 resched_task(p); 3858 return; 3859 } 3860 3861 /* 3862 * Don't schedule slices shorter than 10000ns, that just 3863 * doesn't make sense. Rely on vruntime for fairness. 3864 */ 3865 if (rq->curr != p) 3866 delta = max_t(s64, 10000LL, delta); 3867 3868 hrtick_start(rq, delta); 3869 } 3870 } 3871 3872 /* 3873 * called from enqueue/dequeue and updates the hrtick when the 3874 * current task is from our class and nr_running is low enough 3875 * to matter. 3876 */ 3877 static void hrtick_update(struct rq *rq) 3878 { 3879 struct task_struct *curr = rq->curr; 3880 3881 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) 3882 return; 3883 3884 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) 3885 hrtick_start_fair(rq, curr); 3886 } 3887 #else /* !CONFIG_SCHED_HRTICK */ 3888 static inline void 3889 hrtick_start_fair(struct rq *rq, struct task_struct *p) 3890 { 3891 } 3892 3893 static inline void hrtick_update(struct rq *rq) 3894 { 3895 } 3896 #endif 3897 3898 /* 3899 * The enqueue_task method is called before nr_running is 3900 * increased. Here we update the fair scheduling stats and 3901 * then put the task into the rbtree: 3902 */ 3903 static void 3904 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 3905 { 3906 struct cfs_rq *cfs_rq; 3907 struct sched_entity *se = &p->se; 3908 3909 for_each_sched_entity(se) { 3910 if (se->on_rq) 3911 break; 3912 cfs_rq = cfs_rq_of(se); 3913 enqueue_entity(cfs_rq, se, flags); 3914 3915 /* 3916 * end evaluation on encountering a throttled cfs_rq 3917 * 3918 * note: in the case of encountering a throttled cfs_rq we will 3919 * post the final h_nr_running increment below. 3920 */ 3921 if (cfs_rq_throttled(cfs_rq)) 3922 break; 3923 cfs_rq->h_nr_running++; 3924 3925 flags = ENQUEUE_WAKEUP; 3926 } 3927 3928 for_each_sched_entity(se) { 3929 cfs_rq = cfs_rq_of(se); 3930 cfs_rq->h_nr_running++; 3931 3932 if (cfs_rq_throttled(cfs_rq)) 3933 break; 3934 3935 update_cfs_shares(cfs_rq); 3936 update_entity_load_avg(se, 1); 3937 } 3938 3939 if (!se) { 3940 update_rq_runnable_avg(rq, rq->nr_running); 3941 add_nr_running(rq, 1); 3942 } 3943 hrtick_update(rq); 3944 } 3945 3946 static void set_next_buddy(struct sched_entity *se); 3947 3948 /* 3949 * The dequeue_task method is called before nr_running is 3950 * decreased. We remove the task from the rbtree and 3951 * update the fair scheduling stats: 3952 */ 3953 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 3954 { 3955 struct cfs_rq *cfs_rq; 3956 struct sched_entity *se = &p->se; 3957 int task_sleep = flags & DEQUEUE_SLEEP; 3958 3959 for_each_sched_entity(se) { 3960 cfs_rq = cfs_rq_of(se); 3961 dequeue_entity(cfs_rq, se, flags); 3962 3963 /* 3964 * end evaluation on encountering a throttled cfs_rq 3965 * 3966 * note: in the case of encountering a throttled cfs_rq we will 3967 * post the final h_nr_running decrement below. 3968 */ 3969 if (cfs_rq_throttled(cfs_rq)) 3970 break; 3971 cfs_rq->h_nr_running--; 3972 3973 /* Don't dequeue parent if it has other entities besides us */ 3974 if (cfs_rq->load.weight) { 3975 /* 3976 * Bias pick_next to pick a task from this cfs_rq, as 3977 * p is sleeping when it is within its sched_slice. 3978 */ 3979 if (task_sleep && parent_entity(se)) 3980 set_next_buddy(parent_entity(se)); 3981 3982 /* avoid re-evaluating load for this entity */ 3983 se = parent_entity(se); 3984 break; 3985 } 3986 flags |= DEQUEUE_SLEEP; 3987 } 3988 3989 for_each_sched_entity(se) { 3990 cfs_rq = cfs_rq_of(se); 3991 cfs_rq->h_nr_running--; 3992 3993 if (cfs_rq_throttled(cfs_rq)) 3994 break; 3995 3996 update_cfs_shares(cfs_rq); 3997 update_entity_load_avg(se, 1); 3998 } 3999 4000 if (!se) { 4001 sub_nr_running(rq, 1); 4002 update_rq_runnable_avg(rq, 1); 4003 } 4004 hrtick_update(rq); 4005 } 4006 4007 #ifdef CONFIG_SMP 4008 /* Used instead of source_load when we know the type == 0 */ 4009 static unsigned long weighted_cpuload(const int cpu) 4010 { 4011 return cpu_rq(cpu)->cfs.runnable_load_avg; 4012 } 4013 4014 /* 4015 * Return a low guess at the load of a migration-source cpu weighted 4016 * according to the scheduling class and "nice" value. 4017 * 4018 * We want to under-estimate the load of migration sources, to 4019 * balance conservatively. 4020 */ 4021 static unsigned long source_load(int cpu, int type) 4022 { 4023 struct rq *rq = cpu_rq(cpu); 4024 unsigned long total = weighted_cpuload(cpu); 4025 4026 if (type == 0 || !sched_feat(LB_BIAS)) 4027 return total; 4028 4029 return min(rq->cpu_load[type-1], total); 4030 } 4031 4032 /* 4033 * Return a high guess at the load of a migration-target cpu weighted 4034 * according to the scheduling class and "nice" value. 4035 */ 4036 static unsigned long target_load(int cpu, int type) 4037 { 4038 struct rq *rq = cpu_rq(cpu); 4039 unsigned long total = weighted_cpuload(cpu); 4040 4041 if (type == 0 || !sched_feat(LB_BIAS)) 4042 return total; 4043 4044 return max(rq->cpu_load[type-1], total); 4045 } 4046 4047 static unsigned long capacity_of(int cpu) 4048 { 4049 return cpu_rq(cpu)->cpu_capacity; 4050 } 4051 4052 static unsigned long cpu_avg_load_per_task(int cpu) 4053 { 4054 struct rq *rq = cpu_rq(cpu); 4055 unsigned long nr_running = ACCESS_ONCE(rq->nr_running); 4056 unsigned long load_avg = rq->cfs.runnable_load_avg; 4057 4058 if (nr_running) 4059 return load_avg / nr_running; 4060 4061 return 0; 4062 } 4063 4064 static void record_wakee(struct task_struct *p) 4065 { 4066 /* 4067 * Rough decay (wiping) for cost saving, don't worry 4068 * about the boundary, really active task won't care 4069 * about the loss. 4070 */ 4071 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { 4072 current->wakee_flips >>= 1; 4073 current->wakee_flip_decay_ts = jiffies; 4074 } 4075 4076 if (current->last_wakee != p) { 4077 current->last_wakee = p; 4078 current->wakee_flips++; 4079 } 4080 } 4081 4082 static void task_waking_fair(struct task_struct *p) 4083 { 4084 struct sched_entity *se = &p->se; 4085 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4086 u64 min_vruntime; 4087 4088 #ifndef CONFIG_64BIT 4089 u64 min_vruntime_copy; 4090 4091 do { 4092 min_vruntime_copy = cfs_rq->min_vruntime_copy; 4093 smp_rmb(); 4094 min_vruntime = cfs_rq->min_vruntime; 4095 } while (min_vruntime != min_vruntime_copy); 4096 #else 4097 min_vruntime = cfs_rq->min_vruntime; 4098 #endif 4099 4100 se->vruntime -= min_vruntime; 4101 record_wakee(p); 4102 } 4103 4104 #ifdef CONFIG_FAIR_GROUP_SCHED 4105 /* 4106 * effective_load() calculates the load change as seen from the root_task_group 4107 * 4108 * Adding load to a group doesn't make a group heavier, but can cause movement 4109 * of group shares between cpus. Assuming the shares were perfectly aligned one 4110 * can calculate the shift in shares. 4111 * 4112 * Calculate the effective load difference if @wl is added (subtracted) to @tg 4113 * on this @cpu and results in a total addition (subtraction) of @wg to the 4114 * total group weight. 4115 * 4116 * Given a runqueue weight distribution (rw_i) we can compute a shares 4117 * distribution (s_i) using: 4118 * 4119 * s_i = rw_i / \Sum rw_j (1) 4120 * 4121 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and 4122 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting 4123 * shares distribution (s_i): 4124 * 4125 * rw_i = { 2, 4, 1, 0 } 4126 * s_i = { 2/7, 4/7, 1/7, 0 } 4127 * 4128 * As per wake_affine() we're interested in the load of two CPUs (the CPU the 4129 * task used to run on and the CPU the waker is running on), we need to 4130 * compute the effect of waking a task on either CPU and, in case of a sync 4131 * wakeup, compute the effect of the current task going to sleep. 4132 * 4133 * So for a change of @wl to the local @cpu with an overall group weight change 4134 * of @wl we can compute the new shares distribution (s'_i) using: 4135 * 4136 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) 4137 * 4138 * Suppose we're interested in CPUs 0 and 1, and want to compute the load 4139 * differences in waking a task to CPU 0. The additional task changes the 4140 * weight and shares distributions like: 4141 * 4142 * rw'_i = { 3, 4, 1, 0 } 4143 * s'_i = { 3/8, 4/8, 1/8, 0 } 4144 * 4145 * We can then compute the difference in effective weight by using: 4146 * 4147 * dw_i = S * (s'_i - s_i) (3) 4148 * 4149 * Where 'S' is the group weight as seen by its parent. 4150 * 4151 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) 4152 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - 4153 * 4/7) times the weight of the group. 4154 */ 4155 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 4156 { 4157 struct sched_entity *se = tg->se[cpu]; 4158 4159 if (!tg->parent) /* the trivial, non-cgroup case */ 4160 return wl; 4161 4162 for_each_sched_entity(se) { 4163 long w, W; 4164 4165 tg = se->my_q->tg; 4166 4167 /* 4168 * W = @wg + \Sum rw_j 4169 */ 4170 W = wg + calc_tg_weight(tg, se->my_q); 4171 4172 /* 4173 * w = rw_i + @wl 4174 */ 4175 w = se->my_q->load.weight + wl; 4176 4177 /* 4178 * wl = S * s'_i; see (2) 4179 */ 4180 if (W > 0 && w < W) 4181 wl = (w * tg->shares) / W; 4182 else 4183 wl = tg->shares; 4184 4185 /* 4186 * Per the above, wl is the new se->load.weight value; since 4187 * those are clipped to [MIN_SHARES, ...) do so now. See 4188 * calc_cfs_shares(). 4189 */ 4190 if (wl < MIN_SHARES) 4191 wl = MIN_SHARES; 4192 4193 /* 4194 * wl = dw_i = S * (s'_i - s_i); see (3) 4195 */ 4196 wl -= se->load.weight; 4197 4198 /* 4199 * Recursively apply this logic to all parent groups to compute 4200 * the final effective load change on the root group. Since 4201 * only the @tg group gets extra weight, all parent groups can 4202 * only redistribute existing shares. @wl is the shift in shares 4203 * resulting from this level per the above. 4204 */ 4205 wg = 0; 4206 } 4207 4208 return wl; 4209 } 4210 #else 4211 4212 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 4213 { 4214 return wl; 4215 } 4216 4217 #endif 4218 4219 static int wake_wide(struct task_struct *p) 4220 { 4221 int factor = this_cpu_read(sd_llc_size); 4222 4223 /* 4224 * Yeah, it's the switching-frequency, could means many wakee or 4225 * rapidly switch, use factor here will just help to automatically 4226 * adjust the loose-degree, so bigger node will lead to more pull. 4227 */ 4228 if (p->wakee_flips > factor) { 4229 /* 4230 * wakee is somewhat hot, it needs certain amount of cpu 4231 * resource, so if waker is far more hot, prefer to leave 4232 * it alone. 4233 */ 4234 if (current->wakee_flips > (factor * p->wakee_flips)) 4235 return 1; 4236 } 4237 4238 return 0; 4239 } 4240 4241 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 4242 { 4243 s64 this_load, load; 4244 int idx, this_cpu, prev_cpu; 4245 unsigned long tl_per_task; 4246 struct task_group *tg; 4247 unsigned long weight; 4248 int balanced; 4249 4250 /* 4251 * If we wake multiple tasks be careful to not bounce 4252 * ourselves around too much. 4253 */ 4254 if (wake_wide(p)) 4255 return 0; 4256 4257 idx = sd->wake_idx; 4258 this_cpu = smp_processor_id(); 4259 prev_cpu = task_cpu(p); 4260 load = source_load(prev_cpu, idx); 4261 this_load = target_load(this_cpu, idx); 4262 4263 /* 4264 * If sync wakeup then subtract the (maximum possible) 4265 * effect of the currently running task from the load 4266 * of the current CPU: 4267 */ 4268 if (sync) { 4269 tg = task_group(current); 4270 weight = current->se.load.weight; 4271 4272 this_load += effective_load(tg, this_cpu, -weight, -weight); 4273 load += effective_load(tg, prev_cpu, 0, -weight); 4274 } 4275 4276 tg = task_group(p); 4277 weight = p->se.load.weight; 4278 4279 /* 4280 * In low-load situations, where prev_cpu is idle and this_cpu is idle 4281 * due to the sync cause above having dropped this_load to 0, we'll 4282 * always have an imbalance, but there's really nothing you can do 4283 * about that, so that's good too. 4284 * 4285 * Otherwise check if either cpus are near enough in load to allow this 4286 * task to be woken on this_cpu. 4287 */ 4288 if (this_load > 0) { 4289 s64 this_eff_load, prev_eff_load; 4290 4291 this_eff_load = 100; 4292 this_eff_load *= capacity_of(prev_cpu); 4293 this_eff_load *= this_load + 4294 effective_load(tg, this_cpu, weight, weight); 4295 4296 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; 4297 prev_eff_load *= capacity_of(this_cpu); 4298 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); 4299 4300 balanced = this_eff_load <= prev_eff_load; 4301 } else 4302 balanced = true; 4303 4304 /* 4305 * If the currently running task will sleep within 4306 * a reasonable amount of time then attract this newly 4307 * woken task: 4308 */ 4309 if (sync && balanced) 4310 return 1; 4311 4312 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); 4313 tl_per_task = cpu_avg_load_per_task(this_cpu); 4314 4315 if (balanced || 4316 (this_load <= load && 4317 this_load + target_load(prev_cpu, idx) <= tl_per_task)) { 4318 /* 4319 * This domain has SD_WAKE_AFFINE and 4320 * p is cache cold in this domain, and 4321 * there is no bad imbalance. 4322 */ 4323 schedstat_inc(sd, ttwu_move_affine); 4324 schedstat_inc(p, se.statistics.nr_wakeups_affine); 4325 4326 return 1; 4327 } 4328 return 0; 4329 } 4330 4331 /* 4332 * find_idlest_group finds and returns the least busy CPU group within the 4333 * domain. 4334 */ 4335 static struct sched_group * 4336 find_idlest_group(struct sched_domain *sd, struct task_struct *p, 4337 int this_cpu, int sd_flag) 4338 { 4339 struct sched_group *idlest = NULL, *group = sd->groups; 4340 unsigned long min_load = ULONG_MAX, this_load = 0; 4341 int load_idx = sd->forkexec_idx; 4342 int imbalance = 100 + (sd->imbalance_pct-100)/2; 4343 4344 if (sd_flag & SD_BALANCE_WAKE) 4345 load_idx = sd->wake_idx; 4346 4347 do { 4348 unsigned long load, avg_load; 4349 int local_group; 4350 int i; 4351 4352 /* Skip over this group if it has no CPUs allowed */ 4353 if (!cpumask_intersects(sched_group_cpus(group), 4354 tsk_cpus_allowed(p))) 4355 continue; 4356 4357 local_group = cpumask_test_cpu(this_cpu, 4358 sched_group_cpus(group)); 4359 4360 /* Tally up the load of all CPUs in the group */ 4361 avg_load = 0; 4362 4363 for_each_cpu(i, sched_group_cpus(group)) { 4364 /* Bias balancing toward cpus of our domain */ 4365 if (local_group) 4366 load = source_load(i, load_idx); 4367 else 4368 load = target_load(i, load_idx); 4369 4370 avg_load += load; 4371 } 4372 4373 /* Adjust by relative CPU capacity of the group */ 4374 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; 4375 4376 if (local_group) { 4377 this_load = avg_load; 4378 } else if (avg_load < min_load) { 4379 min_load = avg_load; 4380 idlest = group; 4381 } 4382 } while (group = group->next, group != sd->groups); 4383 4384 if (!idlest || 100*this_load < imbalance*min_load) 4385 return NULL; 4386 return idlest; 4387 } 4388 4389 /* 4390 * find_idlest_cpu - find the idlest cpu among the cpus in group. 4391 */ 4392 static int 4393 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 4394 { 4395 unsigned long load, min_load = ULONG_MAX; 4396 int idlest = -1; 4397 int i; 4398 4399 /* Traverse only the allowed CPUs */ 4400 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { 4401 load = weighted_cpuload(i); 4402 4403 if (load < min_load || (load == min_load && i == this_cpu)) { 4404 min_load = load; 4405 idlest = i; 4406 } 4407 } 4408 4409 return idlest; 4410 } 4411 4412 /* 4413 * Try and locate an idle CPU in the sched_domain. 4414 */ 4415 static int select_idle_sibling(struct task_struct *p, int target) 4416 { 4417 struct sched_domain *sd; 4418 struct sched_group *sg; 4419 int i = task_cpu(p); 4420 4421 if (idle_cpu(target)) 4422 return target; 4423 4424 /* 4425 * If the prevous cpu is cache affine and idle, don't be stupid. 4426 */ 4427 if (i != target && cpus_share_cache(i, target) && idle_cpu(i)) 4428 return i; 4429 4430 /* 4431 * Otherwise, iterate the domains and find an elegible idle cpu. 4432 */ 4433 sd = rcu_dereference(per_cpu(sd_llc, target)); 4434 for_each_lower_domain(sd) { 4435 sg = sd->groups; 4436 do { 4437 if (!cpumask_intersects(sched_group_cpus(sg), 4438 tsk_cpus_allowed(p))) 4439 goto next; 4440 4441 for_each_cpu(i, sched_group_cpus(sg)) { 4442 if (i == target || !idle_cpu(i)) 4443 goto next; 4444 } 4445 4446 target = cpumask_first_and(sched_group_cpus(sg), 4447 tsk_cpus_allowed(p)); 4448 goto done; 4449 next: 4450 sg = sg->next; 4451 } while (sg != sd->groups); 4452 } 4453 done: 4454 return target; 4455 } 4456 4457 /* 4458 * select_task_rq_fair: Select target runqueue for the waking task in domains 4459 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, 4460 * SD_BALANCE_FORK, or SD_BALANCE_EXEC. 4461 * 4462 * Balances load by selecting the idlest cpu in the idlest group, or under 4463 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set. 4464 * 4465 * Returns the target cpu number. 4466 * 4467 * preempt must be disabled. 4468 */ 4469 static int 4470 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) 4471 { 4472 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; 4473 int cpu = smp_processor_id(); 4474 int new_cpu = cpu; 4475 int want_affine = 0; 4476 int sync = wake_flags & WF_SYNC; 4477 4478 if (p->nr_cpus_allowed == 1) 4479 return prev_cpu; 4480 4481 if (sd_flag & SD_BALANCE_WAKE) { 4482 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) 4483 want_affine = 1; 4484 new_cpu = prev_cpu; 4485 } 4486 4487 rcu_read_lock(); 4488 for_each_domain(cpu, tmp) { 4489 if (!(tmp->flags & SD_LOAD_BALANCE)) 4490 continue; 4491 4492 /* 4493 * If both cpu and prev_cpu are part of this domain, 4494 * cpu is a valid SD_WAKE_AFFINE target. 4495 */ 4496 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && 4497 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { 4498 affine_sd = tmp; 4499 break; 4500 } 4501 4502 if (tmp->flags & sd_flag) 4503 sd = tmp; 4504 } 4505 4506 if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync)) 4507 prev_cpu = cpu; 4508 4509 if (sd_flag & SD_BALANCE_WAKE) { 4510 new_cpu = select_idle_sibling(p, prev_cpu); 4511 goto unlock; 4512 } 4513 4514 while (sd) { 4515 struct sched_group *group; 4516 int weight; 4517 4518 if (!(sd->flags & sd_flag)) { 4519 sd = sd->child; 4520 continue; 4521 } 4522 4523 group = find_idlest_group(sd, p, cpu, sd_flag); 4524 if (!group) { 4525 sd = sd->child; 4526 continue; 4527 } 4528 4529 new_cpu = find_idlest_cpu(group, p, cpu); 4530 if (new_cpu == -1 || new_cpu == cpu) { 4531 /* Now try balancing at a lower domain level of cpu */ 4532 sd = sd->child; 4533 continue; 4534 } 4535 4536 /* Now try balancing at a lower domain level of new_cpu */ 4537 cpu = new_cpu; 4538 weight = sd->span_weight; 4539 sd = NULL; 4540 for_each_domain(cpu, tmp) { 4541 if (weight <= tmp->span_weight) 4542 break; 4543 if (tmp->flags & sd_flag) 4544 sd = tmp; 4545 } 4546 /* while loop will break here if sd == NULL */ 4547 } 4548 unlock: 4549 rcu_read_unlock(); 4550 4551 return new_cpu; 4552 } 4553 4554 /* 4555 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and 4556 * cfs_rq_of(p) references at time of call are still valid and identify the 4557 * previous cpu. However, the caller only guarantees p->pi_lock is held; no 4558 * other assumptions, including the state of rq->lock, should be made. 4559 */ 4560 static void 4561 migrate_task_rq_fair(struct task_struct *p, int next_cpu) 4562 { 4563 struct sched_entity *se = &p->se; 4564 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4565 4566 /* 4567 * Load tracking: accumulate removed load so that it can be processed 4568 * when we next update owning cfs_rq under rq->lock. Tasks contribute 4569 * to blocked load iff they have a positive decay-count. It can never 4570 * be negative here since on-rq tasks have decay-count == 0. 4571 */ 4572 if (se->avg.decay_count) { 4573 se->avg.decay_count = -__synchronize_entity_decay(se); 4574 atomic_long_add(se->avg.load_avg_contrib, 4575 &cfs_rq->removed_load); 4576 } 4577 4578 /* We have migrated, no longer consider this task hot */ 4579 se->exec_start = 0; 4580 } 4581 #endif /* CONFIG_SMP */ 4582 4583 static unsigned long 4584 wakeup_gran(struct sched_entity *curr, struct sched_entity *se) 4585 { 4586 unsigned long gran = sysctl_sched_wakeup_granularity; 4587 4588 /* 4589 * Since its curr running now, convert the gran from real-time 4590 * to virtual-time in his units. 4591 * 4592 * By using 'se' instead of 'curr' we penalize light tasks, so 4593 * they get preempted easier. That is, if 'se' < 'curr' then 4594 * the resulting gran will be larger, therefore penalizing the 4595 * lighter, if otoh 'se' > 'curr' then the resulting gran will 4596 * be smaller, again penalizing the lighter task. 4597 * 4598 * This is especially important for buddies when the leftmost 4599 * task is higher priority than the buddy. 4600 */ 4601 return calc_delta_fair(gran, se); 4602 } 4603 4604 /* 4605 * Should 'se' preempt 'curr'. 4606 * 4607 * |s1 4608 * |s2 4609 * |s3 4610 * g 4611 * |<--->|c 4612 * 4613 * w(c, s1) = -1 4614 * w(c, s2) = 0 4615 * w(c, s3) = 1 4616 * 4617 */ 4618 static int 4619 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) 4620 { 4621 s64 gran, vdiff = curr->vruntime - se->vruntime; 4622 4623 if (vdiff <= 0) 4624 return -1; 4625 4626 gran = wakeup_gran(curr, se); 4627 if (vdiff > gran) 4628 return 1; 4629 4630 return 0; 4631 } 4632 4633 static void set_last_buddy(struct sched_entity *se) 4634 { 4635 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 4636 return; 4637 4638 for_each_sched_entity(se) 4639 cfs_rq_of(se)->last = se; 4640 } 4641 4642 static void set_next_buddy(struct sched_entity *se) 4643 { 4644 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 4645 return; 4646 4647 for_each_sched_entity(se) 4648 cfs_rq_of(se)->next = se; 4649 } 4650 4651 static void set_skip_buddy(struct sched_entity *se) 4652 { 4653 for_each_sched_entity(se) 4654 cfs_rq_of(se)->skip = se; 4655 } 4656 4657 /* 4658 * Preempt the current task with a newly woken task if needed: 4659 */ 4660 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 4661 { 4662 struct task_struct *curr = rq->curr; 4663 struct sched_entity *se = &curr->se, *pse = &p->se; 4664 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 4665 int scale = cfs_rq->nr_running >= sched_nr_latency; 4666 int next_buddy_marked = 0; 4667 4668 if (unlikely(se == pse)) 4669 return; 4670 4671 /* 4672 * This is possible from callers such as move_task(), in which we 4673 * unconditionally check_prempt_curr() after an enqueue (which may have 4674 * lead to a throttle). This both saves work and prevents false 4675 * next-buddy nomination below. 4676 */ 4677 if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) 4678 return; 4679 4680 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { 4681 set_next_buddy(pse); 4682 next_buddy_marked = 1; 4683 } 4684 4685 /* 4686 * We can come here with TIF_NEED_RESCHED already set from new task 4687 * wake up path. 4688 * 4689 * Note: this also catches the edge-case of curr being in a throttled 4690 * group (e.g. via set_curr_task), since update_curr() (in the 4691 * enqueue of curr) will have resulted in resched being set. This 4692 * prevents us from potentially nominating it as a false LAST_BUDDY 4693 * below. 4694 */ 4695 if (test_tsk_need_resched(curr)) 4696 return; 4697 4698 /* Idle tasks are by definition preempted by non-idle tasks. */ 4699 if (unlikely(curr->policy == SCHED_IDLE) && 4700 likely(p->policy != SCHED_IDLE)) 4701 goto preempt; 4702 4703 /* 4704 * Batch and idle tasks do not preempt non-idle tasks (their preemption 4705 * is driven by the tick): 4706 */ 4707 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) 4708 return; 4709 4710 find_matching_se(&se, &pse); 4711 update_curr(cfs_rq_of(se)); 4712 BUG_ON(!pse); 4713 if (wakeup_preempt_entity(se, pse) == 1) { 4714 /* 4715 * Bias pick_next to pick the sched entity that is 4716 * triggering this preemption. 4717 */ 4718 if (!next_buddy_marked) 4719 set_next_buddy(pse); 4720 goto preempt; 4721 } 4722 4723 return; 4724 4725 preempt: 4726 resched_task(curr); 4727 /* 4728 * Only set the backward buddy when the current task is still 4729 * on the rq. This can happen when a wakeup gets interleaved 4730 * with schedule on the ->pre_schedule() or idle_balance() 4731 * point, either of which can * drop the rq lock. 4732 * 4733 * Also, during early boot the idle thread is in the fair class, 4734 * for obvious reasons its a bad idea to schedule back to it. 4735 */ 4736 if (unlikely(!se->on_rq || curr == rq->idle)) 4737 return; 4738 4739 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) 4740 set_last_buddy(se); 4741 } 4742 4743 static struct task_struct * 4744 pick_next_task_fair(struct rq *rq, struct task_struct *prev) 4745 { 4746 struct cfs_rq *cfs_rq = &rq->cfs; 4747 struct sched_entity *se; 4748 struct task_struct *p; 4749 int new_tasks; 4750 4751 again: 4752 #ifdef CONFIG_FAIR_GROUP_SCHED 4753 if (!cfs_rq->nr_running) 4754 goto idle; 4755 4756 if (prev->sched_class != &fair_sched_class) 4757 goto simple; 4758 4759 /* 4760 * Because of the set_next_buddy() in dequeue_task_fair() it is rather 4761 * likely that a next task is from the same cgroup as the current. 4762 * 4763 * Therefore attempt to avoid putting and setting the entire cgroup 4764 * hierarchy, only change the part that actually changes. 4765 */ 4766 4767 do { 4768 struct sched_entity *curr = cfs_rq->curr; 4769 4770 /* 4771 * Since we got here without doing put_prev_entity() we also 4772 * have to consider cfs_rq->curr. If it is still a runnable 4773 * entity, update_curr() will update its vruntime, otherwise 4774 * forget we've ever seen it. 4775 */ 4776 if (curr && curr->on_rq) 4777 update_curr(cfs_rq); 4778 else 4779 curr = NULL; 4780 4781 /* 4782 * This call to check_cfs_rq_runtime() will do the throttle and 4783 * dequeue its entity in the parent(s). Therefore the 'simple' 4784 * nr_running test will indeed be correct. 4785 */ 4786 if (unlikely(check_cfs_rq_runtime(cfs_rq))) 4787 goto simple; 4788 4789 se = pick_next_entity(cfs_rq, curr); 4790 cfs_rq = group_cfs_rq(se); 4791 } while (cfs_rq); 4792 4793 p = task_of(se); 4794 4795 /* 4796 * Since we haven't yet done put_prev_entity and if the selected task 4797 * is a different task than we started out with, try and touch the 4798 * least amount of cfs_rqs. 4799 */ 4800 if (prev != p) { 4801 struct sched_entity *pse = &prev->se; 4802 4803 while (!(cfs_rq = is_same_group(se, pse))) { 4804 int se_depth = se->depth; 4805 int pse_depth = pse->depth; 4806 4807 if (se_depth <= pse_depth) { 4808 put_prev_entity(cfs_rq_of(pse), pse); 4809 pse = parent_entity(pse); 4810 } 4811 if (se_depth >= pse_depth) { 4812 set_next_entity(cfs_rq_of(se), se); 4813 se = parent_entity(se); 4814 } 4815 } 4816 4817 put_prev_entity(cfs_rq, pse); 4818 set_next_entity(cfs_rq, se); 4819 } 4820 4821 if (hrtick_enabled(rq)) 4822 hrtick_start_fair(rq, p); 4823 4824 return p; 4825 simple: 4826 cfs_rq = &rq->cfs; 4827 #endif 4828 4829 if (!cfs_rq->nr_running) 4830 goto idle; 4831 4832 put_prev_task(rq, prev); 4833 4834 do { 4835 se = pick_next_entity(cfs_rq, NULL); 4836 set_next_entity(cfs_rq, se); 4837 cfs_rq = group_cfs_rq(se); 4838 } while (cfs_rq); 4839 4840 p = task_of(se); 4841 4842 if (hrtick_enabled(rq)) 4843 hrtick_start_fair(rq, p); 4844 4845 return p; 4846 4847 idle: 4848 new_tasks = idle_balance(rq); 4849 /* 4850 * Because idle_balance() releases (and re-acquires) rq->lock, it is 4851 * possible for any higher priority task to appear. In that case we 4852 * must re-start the pick_next_entity() loop. 4853 */ 4854 if (new_tasks < 0) 4855 return RETRY_TASK; 4856 4857 if (new_tasks > 0) 4858 goto again; 4859 4860 return NULL; 4861 } 4862 4863 /* 4864 * Account for a descheduled task: 4865 */ 4866 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) 4867 { 4868 struct sched_entity *se = &prev->se; 4869 struct cfs_rq *cfs_rq; 4870 4871 for_each_sched_entity(se) { 4872 cfs_rq = cfs_rq_of(se); 4873 put_prev_entity(cfs_rq, se); 4874 } 4875 } 4876 4877 /* 4878 * sched_yield() is very simple 4879 * 4880 * The magic of dealing with the ->skip buddy is in pick_next_entity. 4881 */ 4882 static void yield_task_fair(struct rq *rq) 4883 { 4884 struct task_struct *curr = rq->curr; 4885 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 4886 struct sched_entity *se = &curr->se; 4887 4888 /* 4889 * Are we the only task in the tree? 4890 */ 4891 if (unlikely(rq->nr_running == 1)) 4892 return; 4893 4894 clear_buddies(cfs_rq, se); 4895 4896 if (curr->policy != SCHED_BATCH) { 4897 update_rq_clock(rq); 4898 /* 4899 * Update run-time statistics of the 'current'. 4900 */ 4901 update_curr(cfs_rq); 4902 /* 4903 * Tell update_rq_clock() that we've just updated, 4904 * so we don't do microscopic update in schedule() 4905 * and double the fastpath cost. 4906 */ 4907 rq->skip_clock_update = 1; 4908 } 4909 4910 set_skip_buddy(se); 4911 } 4912 4913 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) 4914 { 4915 struct sched_entity *se = &p->se; 4916 4917 /* throttled hierarchies are not runnable */ 4918 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) 4919 return false; 4920 4921 /* Tell the scheduler that we'd really like pse to run next. */ 4922 set_next_buddy(se); 4923 4924 yield_task_fair(rq); 4925 4926 return true; 4927 } 4928 4929 #ifdef CONFIG_SMP 4930 /************************************************** 4931 * Fair scheduling class load-balancing methods. 4932 * 4933 * BASICS 4934 * 4935 * The purpose of load-balancing is to achieve the same basic fairness the 4936 * per-cpu scheduler provides, namely provide a proportional amount of compute 4937 * time to each task. This is expressed in the following equation: 4938 * 4939 * W_i,n/P_i == W_j,n/P_j for all i,j (1) 4940 * 4941 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight 4942 * W_i,0 is defined as: 4943 * 4944 * W_i,0 = \Sum_j w_i,j (2) 4945 * 4946 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight 4947 * is derived from the nice value as per prio_to_weight[]. 4948 * 4949 * The weight average is an exponential decay average of the instantaneous 4950 * weight: 4951 * 4952 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) 4953 * 4954 * C_i is the compute capacity of cpu i, typically it is the 4955 * fraction of 'recent' time available for SCHED_OTHER task execution. But it 4956 * can also include other factors [XXX]. 4957 * 4958 * To achieve this balance we define a measure of imbalance which follows 4959 * directly from (1): 4960 * 4961 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) 4962 * 4963 * We them move tasks around to minimize the imbalance. In the continuous 4964 * function space it is obvious this converges, in the discrete case we get 4965 * a few fun cases generally called infeasible weight scenarios. 4966 * 4967 * [XXX expand on: 4968 * - infeasible weights; 4969 * - local vs global optima in the discrete case. ] 4970 * 4971 * 4972 * SCHED DOMAINS 4973 * 4974 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) 4975 * for all i,j solution, we create a tree of cpus that follows the hardware 4976 * topology where each level pairs two lower groups (or better). This results 4977 * in O(log n) layers. Furthermore we reduce the number of cpus going up the 4978 * tree to only the first of the previous level and we decrease the frequency 4979 * of load-balance at each level inv. proportional to the number of cpus in 4980 * the groups. 4981 * 4982 * This yields: 4983 * 4984 * log_2 n 1 n 4985 * \Sum { --- * --- * 2^i } = O(n) (5) 4986 * i = 0 2^i 2^i 4987 * `- size of each group 4988 * | | `- number of cpus doing load-balance 4989 * | `- freq 4990 * `- sum over all levels 4991 * 4992 * Coupled with a limit on how many tasks we can migrate every balance pass, 4993 * this makes (5) the runtime complexity of the balancer. 4994 * 4995 * An important property here is that each CPU is still (indirectly) connected 4996 * to every other cpu in at most O(log n) steps: 4997 * 4998 * The adjacency matrix of the resulting graph is given by: 4999 * 5000 * log_2 n 5001 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) 5002 * k = 0 5003 * 5004 * And you'll find that: 5005 * 5006 * A^(log_2 n)_i,j != 0 for all i,j (7) 5007 * 5008 * Showing there's indeed a path between every cpu in at most O(log n) steps. 5009 * The task movement gives a factor of O(m), giving a convergence complexity 5010 * of: 5011 * 5012 * O(nm log n), n := nr_cpus, m := nr_tasks (8) 5013 * 5014 * 5015 * WORK CONSERVING 5016 * 5017 * In order to avoid CPUs going idle while there's still work to do, new idle 5018 * balancing is more aggressive and has the newly idle cpu iterate up the domain 5019 * tree itself instead of relying on other CPUs to bring it work. 5020 * 5021 * This adds some complexity to both (5) and (8) but it reduces the total idle 5022 * time. 5023 * 5024 * [XXX more?] 5025 * 5026 * 5027 * CGROUPS 5028 * 5029 * Cgroups make a horror show out of (2), instead of a simple sum we get: 5030 * 5031 * s_k,i 5032 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) 5033 * S_k 5034 * 5035 * Where 5036 * 5037 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) 5038 * 5039 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i. 5040 * 5041 * The big problem is S_k, its a global sum needed to compute a local (W_i) 5042 * property. 5043 * 5044 * [XXX write more on how we solve this.. _after_ merging pjt's patches that 5045 * rewrite all of this once again.] 5046 */ 5047 5048 static unsigned long __read_mostly max_load_balance_interval = HZ/10; 5049 5050 enum fbq_type { regular, remote, all }; 5051 5052 #define LBF_ALL_PINNED 0x01 5053 #define LBF_NEED_BREAK 0x02 5054 #define LBF_DST_PINNED 0x04 5055 #define LBF_SOME_PINNED 0x08 5056 5057 struct lb_env { 5058 struct sched_domain *sd; 5059 5060 struct rq *src_rq; 5061 int src_cpu; 5062 5063 int dst_cpu; 5064 struct rq *dst_rq; 5065 5066 struct cpumask *dst_grpmask; 5067 int new_dst_cpu; 5068 enum cpu_idle_type idle; 5069 long imbalance; 5070 /* The set of CPUs under consideration for load-balancing */ 5071 struct cpumask *cpus; 5072 5073 unsigned int flags; 5074 5075 unsigned int loop; 5076 unsigned int loop_break; 5077 unsigned int loop_max; 5078 5079 enum fbq_type fbq_type; 5080 }; 5081 5082 /* 5083 * move_task - move a task from one runqueue to another runqueue. 5084 * Both runqueues must be locked. 5085 */ 5086 static void move_task(struct task_struct *p, struct lb_env *env) 5087 { 5088 deactivate_task(env->src_rq, p, 0); 5089 set_task_cpu(p, env->dst_cpu); 5090 activate_task(env->dst_rq, p, 0); 5091 check_preempt_curr(env->dst_rq, p, 0); 5092 } 5093 5094 /* 5095 * Is this task likely cache-hot: 5096 */ 5097 static int 5098 task_hot(struct task_struct *p, u64 now) 5099 { 5100 s64 delta; 5101 5102 if (p->sched_class != &fair_sched_class) 5103 return 0; 5104 5105 if (unlikely(p->policy == SCHED_IDLE)) 5106 return 0; 5107 5108 /* 5109 * Buddy candidates are cache hot: 5110 */ 5111 if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running && 5112 (&p->se == cfs_rq_of(&p->se)->next || 5113 &p->se == cfs_rq_of(&p->se)->last)) 5114 return 1; 5115 5116 if (sysctl_sched_migration_cost == -1) 5117 return 1; 5118 if (sysctl_sched_migration_cost == 0) 5119 return 0; 5120 5121 delta = now - p->se.exec_start; 5122 5123 return delta < (s64)sysctl_sched_migration_cost; 5124 } 5125 5126 #ifdef CONFIG_NUMA_BALANCING 5127 /* Returns true if the destination node has incurred more faults */ 5128 static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env) 5129 { 5130 struct numa_group *numa_group = rcu_dereference(p->numa_group); 5131 int src_nid, dst_nid; 5132 5133 if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults_memory || 5134 !(env->sd->flags & SD_NUMA)) { 5135 return false; 5136 } 5137 5138 src_nid = cpu_to_node(env->src_cpu); 5139 dst_nid = cpu_to_node(env->dst_cpu); 5140 5141 if (src_nid == dst_nid) 5142 return false; 5143 5144 if (numa_group) { 5145 /* Task is already in the group's interleave set. */ 5146 if (node_isset(src_nid, numa_group->active_nodes)) 5147 return false; 5148 5149 /* Task is moving into the group's interleave set. */ 5150 if (node_isset(dst_nid, numa_group->active_nodes)) 5151 return true; 5152 5153 return group_faults(p, dst_nid) > group_faults(p, src_nid); 5154 } 5155 5156 /* Encourage migration to the preferred node. */ 5157 if (dst_nid == p->numa_preferred_nid) 5158 return true; 5159 5160 return task_faults(p, dst_nid) > task_faults(p, src_nid); 5161 } 5162 5163 5164 static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env) 5165 { 5166 struct numa_group *numa_group = rcu_dereference(p->numa_group); 5167 int src_nid, dst_nid; 5168 5169 if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER)) 5170 return false; 5171 5172 if (!p->numa_faults_memory || !(env->sd->flags & SD_NUMA)) 5173 return false; 5174 5175 src_nid = cpu_to_node(env->src_cpu); 5176 dst_nid = cpu_to_node(env->dst_cpu); 5177 5178 if (src_nid == dst_nid) 5179 return false; 5180 5181 if (numa_group) { 5182 /* Task is moving within/into the group's interleave set. */ 5183 if (node_isset(dst_nid, numa_group->active_nodes)) 5184 return false; 5185 5186 /* Task is moving out of the group's interleave set. */ 5187 if (node_isset(src_nid, numa_group->active_nodes)) 5188 return true; 5189 5190 return group_faults(p, dst_nid) < group_faults(p, src_nid); 5191 } 5192 5193 /* Migrating away from the preferred node is always bad. */ 5194 if (src_nid == p->numa_preferred_nid) 5195 return true; 5196 5197 return task_faults(p, dst_nid) < task_faults(p, src_nid); 5198 } 5199 5200 #else 5201 static inline bool migrate_improves_locality(struct task_struct *p, 5202 struct lb_env *env) 5203 { 5204 return false; 5205 } 5206 5207 static inline bool migrate_degrades_locality(struct task_struct *p, 5208 struct lb_env *env) 5209 { 5210 return false; 5211 } 5212 #endif 5213 5214 /* 5215 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? 5216 */ 5217 static 5218 int can_migrate_task(struct task_struct *p, struct lb_env *env) 5219 { 5220 int tsk_cache_hot = 0; 5221 /* 5222 * We do not migrate tasks that are: 5223 * 1) throttled_lb_pair, or 5224 * 2) cannot be migrated to this CPU due to cpus_allowed, or 5225 * 3) running (obviously), or 5226 * 4) are cache-hot on their current CPU. 5227 */ 5228 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) 5229 return 0; 5230 5231 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { 5232 int cpu; 5233 5234 schedstat_inc(p, se.statistics.nr_failed_migrations_affine); 5235 5236 env->flags |= LBF_SOME_PINNED; 5237 5238 /* 5239 * Remember if this task can be migrated to any other cpu in 5240 * our sched_group. We may want to revisit it if we couldn't 5241 * meet load balance goals by pulling other tasks on src_cpu. 5242 * 5243 * Also avoid computing new_dst_cpu if we have already computed 5244 * one in current iteration. 5245 */ 5246 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED)) 5247 return 0; 5248 5249 /* Prevent to re-select dst_cpu via env's cpus */ 5250 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { 5251 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) { 5252 env->flags |= LBF_DST_PINNED; 5253 env->new_dst_cpu = cpu; 5254 break; 5255 } 5256 } 5257 5258 return 0; 5259 } 5260 5261 /* Record that we found atleast one task that could run on dst_cpu */ 5262 env->flags &= ~LBF_ALL_PINNED; 5263 5264 if (task_running(env->src_rq, p)) { 5265 schedstat_inc(p, se.statistics.nr_failed_migrations_running); 5266 return 0; 5267 } 5268 5269 /* 5270 * Aggressive migration if: 5271 * 1) destination numa is preferred 5272 * 2) task is cache cold, or 5273 * 3) too many balance attempts have failed. 5274 */ 5275 tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq)); 5276 if (!tsk_cache_hot) 5277 tsk_cache_hot = migrate_degrades_locality(p, env); 5278 5279 if (migrate_improves_locality(p, env)) { 5280 #ifdef CONFIG_SCHEDSTATS 5281 if (tsk_cache_hot) { 5282 schedstat_inc(env->sd, lb_hot_gained[env->idle]); 5283 schedstat_inc(p, se.statistics.nr_forced_migrations); 5284 } 5285 #endif 5286 return 1; 5287 } 5288 5289 if (!tsk_cache_hot || 5290 env->sd->nr_balance_failed > env->sd->cache_nice_tries) { 5291 5292 if (tsk_cache_hot) { 5293 schedstat_inc(env->sd, lb_hot_gained[env->idle]); 5294 schedstat_inc(p, se.statistics.nr_forced_migrations); 5295 } 5296 5297 return 1; 5298 } 5299 5300 schedstat_inc(p, se.statistics.nr_failed_migrations_hot); 5301 return 0; 5302 } 5303 5304 /* 5305 * move_one_task tries to move exactly one task from busiest to this_rq, as 5306 * part of active balancing operations within "domain". 5307 * Returns 1 if successful and 0 otherwise. 5308 * 5309 * Called with both runqueues locked. 5310 */ 5311 static int move_one_task(struct lb_env *env) 5312 { 5313 struct task_struct *p, *n; 5314 5315 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) { 5316 if (!can_migrate_task(p, env)) 5317 continue; 5318 5319 move_task(p, env); 5320 /* 5321 * Right now, this is only the second place move_task() 5322 * is called, so we can safely collect move_task() 5323 * stats here rather than inside move_task(). 5324 */ 5325 schedstat_inc(env->sd, lb_gained[env->idle]); 5326 return 1; 5327 } 5328 return 0; 5329 } 5330 5331 static const unsigned int sched_nr_migrate_break = 32; 5332 5333 /* 5334 * move_tasks tries to move up to imbalance weighted load from busiest to 5335 * this_rq, as part of a balancing operation within domain "sd". 5336 * Returns 1 if successful and 0 otherwise. 5337 * 5338 * Called with both runqueues locked. 5339 */ 5340 static int move_tasks(struct lb_env *env) 5341 { 5342 struct list_head *tasks = &env->src_rq->cfs_tasks; 5343 struct task_struct *p; 5344 unsigned long load; 5345 int pulled = 0; 5346 5347 if (env->imbalance <= 0) 5348 return 0; 5349 5350 while (!list_empty(tasks)) { 5351 p = list_first_entry(tasks, struct task_struct, se.group_node); 5352 5353 env->loop++; 5354 /* We've more or less seen every task there is, call it quits */ 5355 if (env->loop > env->loop_max) 5356 break; 5357 5358 /* take a breather every nr_migrate tasks */ 5359 if (env->loop > env->loop_break) { 5360 env->loop_break += sched_nr_migrate_break; 5361 env->flags |= LBF_NEED_BREAK; 5362 break; 5363 } 5364 5365 if (!can_migrate_task(p, env)) 5366 goto next; 5367 5368 load = task_h_load(p); 5369 5370 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) 5371 goto next; 5372 5373 if ((load / 2) > env->imbalance) 5374 goto next; 5375 5376 move_task(p, env); 5377 pulled++; 5378 env->imbalance -= load; 5379 5380 #ifdef CONFIG_PREEMPT 5381 /* 5382 * NEWIDLE balancing is a source of latency, so preemptible 5383 * kernels will stop after the first task is pulled to minimize 5384 * the critical section. 5385 */ 5386 if (env->idle == CPU_NEWLY_IDLE) 5387 break; 5388 #endif 5389 5390 /* 5391 * We only want to steal up to the prescribed amount of 5392 * weighted load. 5393 */ 5394 if (env->imbalance <= 0) 5395 break; 5396 5397 continue; 5398 next: 5399 list_move_tail(&p->se.group_node, tasks); 5400 } 5401 5402 /* 5403 * Right now, this is one of only two places move_task() is called, 5404 * so we can safely collect move_task() stats here rather than 5405 * inside move_task(). 5406 */ 5407 schedstat_add(env->sd, lb_gained[env->idle], pulled); 5408 5409 return pulled; 5410 } 5411 5412 #ifdef CONFIG_FAIR_GROUP_SCHED 5413 /* 5414 * update tg->load_weight by folding this cpu's load_avg 5415 */ 5416 static void __update_blocked_averages_cpu(struct task_group *tg, int cpu) 5417 { 5418 struct sched_entity *se = tg->se[cpu]; 5419 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu]; 5420 5421 /* throttled entities do not contribute to load */ 5422 if (throttled_hierarchy(cfs_rq)) 5423 return; 5424 5425 update_cfs_rq_blocked_load(cfs_rq, 1); 5426 5427 if (se) { 5428 update_entity_load_avg(se, 1); 5429 /* 5430 * We pivot on our runnable average having decayed to zero for 5431 * list removal. This generally implies that all our children 5432 * have also been removed (modulo rounding error or bandwidth 5433 * control); however, such cases are rare and we can fix these 5434 * at enqueue. 5435 * 5436 * TODO: fix up out-of-order children on enqueue. 5437 */ 5438 if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running) 5439 list_del_leaf_cfs_rq(cfs_rq); 5440 } else { 5441 struct rq *rq = rq_of(cfs_rq); 5442 update_rq_runnable_avg(rq, rq->nr_running); 5443 } 5444 } 5445 5446 static void update_blocked_averages(int cpu) 5447 { 5448 struct rq *rq = cpu_rq(cpu); 5449 struct cfs_rq *cfs_rq; 5450 unsigned long flags; 5451 5452 raw_spin_lock_irqsave(&rq->lock, flags); 5453 update_rq_clock(rq); 5454 /* 5455 * Iterates the task_group tree in a bottom up fashion, see 5456 * list_add_leaf_cfs_rq() for details. 5457 */ 5458 for_each_leaf_cfs_rq(rq, cfs_rq) { 5459 /* 5460 * Note: We may want to consider periodically releasing 5461 * rq->lock about these updates so that creating many task 5462 * groups does not result in continually extending hold time. 5463 */ 5464 __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu); 5465 } 5466 5467 raw_spin_unlock_irqrestore(&rq->lock, flags); 5468 } 5469 5470 /* 5471 * Compute the hierarchical load factor for cfs_rq and all its ascendants. 5472 * This needs to be done in a top-down fashion because the load of a child 5473 * group is a fraction of its parents load. 5474 */ 5475 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) 5476 { 5477 struct rq *rq = rq_of(cfs_rq); 5478 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; 5479 unsigned long now = jiffies; 5480 unsigned long load; 5481 5482 if (cfs_rq->last_h_load_update == now) 5483 return; 5484 5485 cfs_rq->h_load_next = NULL; 5486 for_each_sched_entity(se) { 5487 cfs_rq = cfs_rq_of(se); 5488 cfs_rq->h_load_next = se; 5489 if (cfs_rq->last_h_load_update == now) 5490 break; 5491 } 5492 5493 if (!se) { 5494 cfs_rq->h_load = cfs_rq->runnable_load_avg; 5495 cfs_rq->last_h_load_update = now; 5496 } 5497 5498 while ((se = cfs_rq->h_load_next) != NULL) { 5499 load = cfs_rq->h_load; 5500 load = div64_ul(load * se->avg.load_avg_contrib, 5501 cfs_rq->runnable_load_avg + 1); 5502 cfs_rq = group_cfs_rq(se); 5503 cfs_rq->h_load = load; 5504 cfs_rq->last_h_load_update = now; 5505 } 5506 } 5507 5508 static unsigned long task_h_load(struct task_struct *p) 5509 { 5510 struct cfs_rq *cfs_rq = task_cfs_rq(p); 5511 5512 update_cfs_rq_h_load(cfs_rq); 5513 return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load, 5514 cfs_rq->runnable_load_avg + 1); 5515 } 5516 #else 5517 static inline void update_blocked_averages(int cpu) 5518 { 5519 } 5520 5521 static unsigned long task_h_load(struct task_struct *p) 5522 { 5523 return p->se.avg.load_avg_contrib; 5524 } 5525 #endif 5526 5527 /********** Helpers for find_busiest_group ************************/ 5528 /* 5529 * sg_lb_stats - stats of a sched_group required for load_balancing 5530 */ 5531 struct sg_lb_stats { 5532 unsigned long avg_load; /*Avg load across the CPUs of the group */ 5533 unsigned long group_load; /* Total load over the CPUs of the group */ 5534 unsigned long sum_weighted_load; /* Weighted load of group's tasks */ 5535 unsigned long load_per_task; 5536 unsigned long group_capacity; 5537 unsigned int sum_nr_running; /* Nr tasks running in the group */ 5538 unsigned int group_capacity_factor; 5539 unsigned int idle_cpus; 5540 unsigned int group_weight; 5541 int group_imb; /* Is there an imbalance in the group ? */ 5542 int group_has_free_capacity; 5543 #ifdef CONFIG_NUMA_BALANCING 5544 unsigned int nr_numa_running; 5545 unsigned int nr_preferred_running; 5546 #endif 5547 }; 5548 5549 /* 5550 * sd_lb_stats - Structure to store the statistics of a sched_domain 5551 * during load balancing. 5552 */ 5553 struct sd_lb_stats { 5554 struct sched_group *busiest; /* Busiest group in this sd */ 5555 struct sched_group *local; /* Local group in this sd */ 5556 unsigned long total_load; /* Total load of all groups in sd */ 5557 unsigned long total_capacity; /* Total capacity of all groups in sd */ 5558 unsigned long avg_load; /* Average load across all groups in sd */ 5559 5560 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ 5561 struct sg_lb_stats local_stat; /* Statistics of the local group */ 5562 }; 5563 5564 static inline void init_sd_lb_stats(struct sd_lb_stats *sds) 5565 { 5566 /* 5567 * Skimp on the clearing to avoid duplicate work. We can avoid clearing 5568 * local_stat because update_sg_lb_stats() does a full clear/assignment. 5569 * We must however clear busiest_stat::avg_load because 5570 * update_sd_pick_busiest() reads this before assignment. 5571 */ 5572 *sds = (struct sd_lb_stats){ 5573 .busiest = NULL, 5574 .local = NULL, 5575 .total_load = 0UL, 5576 .total_capacity = 0UL, 5577 .busiest_stat = { 5578 .avg_load = 0UL, 5579 }, 5580 }; 5581 } 5582 5583 /** 5584 * get_sd_load_idx - Obtain the load index for a given sched domain. 5585 * @sd: The sched_domain whose load_idx is to be obtained. 5586 * @idle: The idle status of the CPU for whose sd load_idx is obtained. 5587 * 5588 * Return: The load index. 5589 */ 5590 static inline int get_sd_load_idx(struct sched_domain *sd, 5591 enum cpu_idle_type idle) 5592 { 5593 int load_idx; 5594 5595 switch (idle) { 5596 case CPU_NOT_IDLE: 5597 load_idx = sd->busy_idx; 5598 break; 5599 5600 case CPU_NEWLY_IDLE: 5601 load_idx = sd->newidle_idx; 5602 break; 5603 default: 5604 load_idx = sd->idle_idx; 5605 break; 5606 } 5607 5608 return load_idx; 5609 } 5610 5611 static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu) 5612 { 5613 return SCHED_CAPACITY_SCALE; 5614 } 5615 5616 unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu) 5617 { 5618 return default_scale_capacity(sd, cpu); 5619 } 5620 5621 static unsigned long default_scale_smt_capacity(struct sched_domain *sd, int cpu) 5622 { 5623 unsigned long weight = sd->span_weight; 5624 unsigned long smt_gain = sd->smt_gain; 5625 5626 smt_gain /= weight; 5627 5628 return smt_gain; 5629 } 5630 5631 unsigned long __weak arch_scale_smt_capacity(struct sched_domain *sd, int cpu) 5632 { 5633 return default_scale_smt_capacity(sd, cpu); 5634 } 5635 5636 static unsigned long scale_rt_capacity(int cpu) 5637 { 5638 struct rq *rq = cpu_rq(cpu); 5639 u64 total, available, age_stamp, avg; 5640 s64 delta; 5641 5642 /* 5643 * Since we're reading these variables without serialization make sure 5644 * we read them once before doing sanity checks on them. 5645 */ 5646 age_stamp = ACCESS_ONCE(rq->age_stamp); 5647 avg = ACCESS_ONCE(rq->rt_avg); 5648 5649 delta = rq_clock(rq) - age_stamp; 5650 if (unlikely(delta < 0)) 5651 delta = 0; 5652 5653 total = sched_avg_period() + delta; 5654 5655 if (unlikely(total < avg)) { 5656 /* Ensures that capacity won't end up being negative */ 5657 available = 0; 5658 } else { 5659 available = total - avg; 5660 } 5661 5662 if (unlikely((s64)total < SCHED_CAPACITY_SCALE)) 5663 total = SCHED_CAPACITY_SCALE; 5664 5665 total >>= SCHED_CAPACITY_SHIFT; 5666 5667 return div_u64(available, total); 5668 } 5669 5670 static void update_cpu_capacity(struct sched_domain *sd, int cpu) 5671 { 5672 unsigned long weight = sd->span_weight; 5673 unsigned long capacity = SCHED_CAPACITY_SCALE; 5674 struct sched_group *sdg = sd->groups; 5675 5676 if ((sd->flags & SD_SHARE_CPUCAPACITY) && weight > 1) { 5677 if (sched_feat(ARCH_CAPACITY)) 5678 capacity *= arch_scale_smt_capacity(sd, cpu); 5679 else 5680 capacity *= default_scale_smt_capacity(sd, cpu); 5681 5682 capacity >>= SCHED_CAPACITY_SHIFT; 5683 } 5684 5685 sdg->sgc->capacity_orig = capacity; 5686 5687 if (sched_feat(ARCH_CAPACITY)) 5688 capacity *= arch_scale_freq_capacity(sd, cpu); 5689 else 5690 capacity *= default_scale_capacity(sd, cpu); 5691 5692 capacity >>= SCHED_CAPACITY_SHIFT; 5693 5694 capacity *= scale_rt_capacity(cpu); 5695 capacity >>= SCHED_CAPACITY_SHIFT; 5696 5697 if (!capacity) 5698 capacity = 1; 5699 5700 cpu_rq(cpu)->cpu_capacity = capacity; 5701 sdg->sgc->capacity = capacity; 5702 } 5703 5704 void update_group_capacity(struct sched_domain *sd, int cpu) 5705 { 5706 struct sched_domain *child = sd->child; 5707 struct sched_group *group, *sdg = sd->groups; 5708 unsigned long capacity, capacity_orig; 5709 unsigned long interval; 5710 5711 interval = msecs_to_jiffies(sd->balance_interval); 5712 interval = clamp(interval, 1UL, max_load_balance_interval); 5713 sdg->sgc->next_update = jiffies + interval; 5714 5715 if (!child) { 5716 update_cpu_capacity(sd, cpu); 5717 return; 5718 } 5719 5720 capacity_orig = capacity = 0; 5721 5722 if (child->flags & SD_OVERLAP) { 5723 /* 5724 * SD_OVERLAP domains cannot assume that child groups 5725 * span the current group. 5726 */ 5727 5728 for_each_cpu(cpu, sched_group_cpus(sdg)) { 5729 struct sched_group_capacity *sgc; 5730 struct rq *rq = cpu_rq(cpu); 5731 5732 /* 5733 * build_sched_domains() -> init_sched_groups_capacity() 5734 * gets here before we've attached the domains to the 5735 * runqueues. 5736 * 5737 * Use capacity_of(), which is set irrespective of domains 5738 * in update_cpu_capacity(). 5739 * 5740 * This avoids capacity/capacity_orig from being 0 and 5741 * causing divide-by-zero issues on boot. 5742 * 5743 * Runtime updates will correct capacity_orig. 5744 */ 5745 if (unlikely(!rq->sd)) { 5746 capacity_orig += capacity_of(cpu); 5747 capacity += capacity_of(cpu); 5748 continue; 5749 } 5750 5751 sgc = rq->sd->groups->sgc; 5752 capacity_orig += sgc->capacity_orig; 5753 capacity += sgc->capacity; 5754 } 5755 } else { 5756 /* 5757 * !SD_OVERLAP domains can assume that child groups 5758 * span the current group. 5759 */ 5760 5761 group = child->groups; 5762 do { 5763 capacity_orig += group->sgc->capacity_orig; 5764 capacity += group->sgc->capacity; 5765 group = group->next; 5766 } while (group != child->groups); 5767 } 5768 5769 sdg->sgc->capacity_orig = capacity_orig; 5770 sdg->sgc->capacity = capacity; 5771 } 5772 5773 /* 5774 * Try and fix up capacity for tiny siblings, this is needed when 5775 * things like SD_ASYM_PACKING need f_b_g to select another sibling 5776 * which on its own isn't powerful enough. 5777 * 5778 * See update_sd_pick_busiest() and check_asym_packing(). 5779 */ 5780 static inline int 5781 fix_small_capacity(struct sched_domain *sd, struct sched_group *group) 5782 { 5783 /* 5784 * Only siblings can have significantly less than SCHED_CAPACITY_SCALE 5785 */ 5786 if (!(sd->flags & SD_SHARE_CPUCAPACITY)) 5787 return 0; 5788 5789 /* 5790 * If ~90% of the cpu_capacity is still there, we're good. 5791 */ 5792 if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29) 5793 return 1; 5794 5795 return 0; 5796 } 5797 5798 /* 5799 * Group imbalance indicates (and tries to solve) the problem where balancing 5800 * groups is inadequate due to tsk_cpus_allowed() constraints. 5801 * 5802 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a 5803 * cpumask covering 1 cpu of the first group and 3 cpus of the second group. 5804 * Something like: 5805 * 5806 * { 0 1 2 3 } { 4 5 6 7 } 5807 * * * * * 5808 * 5809 * If we were to balance group-wise we'd place two tasks in the first group and 5810 * two tasks in the second group. Clearly this is undesired as it will overload 5811 * cpu 3 and leave one of the cpus in the second group unused. 5812 * 5813 * The current solution to this issue is detecting the skew in the first group 5814 * by noticing the lower domain failed to reach balance and had difficulty 5815 * moving tasks due to affinity constraints. 5816 * 5817 * When this is so detected; this group becomes a candidate for busiest; see 5818 * update_sd_pick_busiest(). And calculate_imbalance() and 5819 * find_busiest_group() avoid some of the usual balance conditions to allow it 5820 * to create an effective group imbalance. 5821 * 5822 * This is a somewhat tricky proposition since the next run might not find the 5823 * group imbalance and decide the groups need to be balanced again. A most 5824 * subtle and fragile situation. 5825 */ 5826 5827 static inline int sg_imbalanced(struct sched_group *group) 5828 { 5829 return group->sgc->imbalance; 5830 } 5831 5832 /* 5833 * Compute the group capacity factor. 5834 * 5835 * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by 5836 * first dividing out the smt factor and computing the actual number of cores 5837 * and limit unit capacity with that. 5838 */ 5839 static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group) 5840 { 5841 unsigned int capacity_factor, smt, cpus; 5842 unsigned int capacity, capacity_orig; 5843 5844 capacity = group->sgc->capacity; 5845 capacity_orig = group->sgc->capacity_orig; 5846 cpus = group->group_weight; 5847 5848 /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */ 5849 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig); 5850 capacity_factor = cpus / smt; /* cores */ 5851 5852 capacity_factor = min_t(unsigned, 5853 capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE)); 5854 if (!capacity_factor) 5855 capacity_factor = fix_small_capacity(env->sd, group); 5856 5857 return capacity_factor; 5858 } 5859 5860 /** 5861 * update_sg_lb_stats - Update sched_group's statistics for load balancing. 5862 * @env: The load balancing environment. 5863 * @group: sched_group whose statistics are to be updated. 5864 * @load_idx: Load index of sched_domain of this_cpu for load calc. 5865 * @local_group: Does group contain this_cpu. 5866 * @sgs: variable to hold the statistics for this group. 5867 */ 5868 static inline void update_sg_lb_stats(struct lb_env *env, 5869 struct sched_group *group, int load_idx, 5870 int local_group, struct sg_lb_stats *sgs) 5871 { 5872 unsigned long load; 5873 int i; 5874 5875 memset(sgs, 0, sizeof(*sgs)); 5876 5877 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 5878 struct rq *rq = cpu_rq(i); 5879 5880 /* Bias balancing toward cpus of our domain */ 5881 if (local_group) 5882 load = target_load(i, load_idx); 5883 else 5884 load = source_load(i, load_idx); 5885 5886 sgs->group_load += load; 5887 sgs->sum_nr_running += rq->nr_running; 5888 #ifdef CONFIG_NUMA_BALANCING 5889 sgs->nr_numa_running += rq->nr_numa_running; 5890 sgs->nr_preferred_running += rq->nr_preferred_running; 5891 #endif 5892 sgs->sum_weighted_load += weighted_cpuload(i); 5893 if (idle_cpu(i)) 5894 sgs->idle_cpus++; 5895 } 5896 5897 /* Adjust by relative CPU capacity of the group */ 5898 sgs->group_capacity = group->sgc->capacity; 5899 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; 5900 5901 if (sgs->sum_nr_running) 5902 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; 5903 5904 sgs->group_weight = group->group_weight; 5905 5906 sgs->group_imb = sg_imbalanced(group); 5907 sgs->group_capacity_factor = sg_capacity_factor(env, group); 5908 5909 if (sgs->group_capacity_factor > sgs->sum_nr_running) 5910 sgs->group_has_free_capacity = 1; 5911 } 5912 5913 /** 5914 * update_sd_pick_busiest - return 1 on busiest group 5915 * @env: The load balancing environment. 5916 * @sds: sched_domain statistics 5917 * @sg: sched_group candidate to be checked for being the busiest 5918 * @sgs: sched_group statistics 5919 * 5920 * Determine if @sg is a busier group than the previously selected 5921 * busiest group. 5922 * 5923 * Return: %true if @sg is a busier group than the previously selected 5924 * busiest group. %false otherwise. 5925 */ 5926 static bool update_sd_pick_busiest(struct lb_env *env, 5927 struct sd_lb_stats *sds, 5928 struct sched_group *sg, 5929 struct sg_lb_stats *sgs) 5930 { 5931 if (sgs->avg_load <= sds->busiest_stat.avg_load) 5932 return false; 5933 5934 if (sgs->sum_nr_running > sgs->group_capacity_factor) 5935 return true; 5936 5937 if (sgs->group_imb) 5938 return true; 5939 5940 /* 5941 * ASYM_PACKING needs to move all the work to the lowest 5942 * numbered CPUs in the group, therefore mark all groups 5943 * higher than ourself as busy. 5944 */ 5945 if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running && 5946 env->dst_cpu < group_first_cpu(sg)) { 5947 if (!sds->busiest) 5948 return true; 5949 5950 if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) 5951 return true; 5952 } 5953 5954 return false; 5955 } 5956 5957 #ifdef CONFIG_NUMA_BALANCING 5958 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 5959 { 5960 if (sgs->sum_nr_running > sgs->nr_numa_running) 5961 return regular; 5962 if (sgs->sum_nr_running > sgs->nr_preferred_running) 5963 return remote; 5964 return all; 5965 } 5966 5967 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 5968 { 5969 if (rq->nr_running > rq->nr_numa_running) 5970 return regular; 5971 if (rq->nr_running > rq->nr_preferred_running) 5972 return remote; 5973 return all; 5974 } 5975 #else 5976 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 5977 { 5978 return all; 5979 } 5980 5981 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 5982 { 5983 return regular; 5984 } 5985 #endif /* CONFIG_NUMA_BALANCING */ 5986 5987 /** 5988 * update_sd_lb_stats - Update sched_domain's statistics for load balancing. 5989 * @env: The load balancing environment. 5990 * @sds: variable to hold the statistics for this sched_domain. 5991 */ 5992 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) 5993 { 5994 struct sched_domain *child = env->sd->child; 5995 struct sched_group *sg = env->sd->groups; 5996 struct sg_lb_stats tmp_sgs; 5997 int load_idx, prefer_sibling = 0; 5998 5999 if (child && child->flags & SD_PREFER_SIBLING) 6000 prefer_sibling = 1; 6001 6002 load_idx = get_sd_load_idx(env->sd, env->idle); 6003 6004 do { 6005 struct sg_lb_stats *sgs = &tmp_sgs; 6006 int local_group; 6007 6008 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg)); 6009 if (local_group) { 6010 sds->local = sg; 6011 sgs = &sds->local_stat; 6012 6013 if (env->idle != CPU_NEWLY_IDLE || 6014 time_after_eq(jiffies, sg->sgc->next_update)) 6015 update_group_capacity(env->sd, env->dst_cpu); 6016 } 6017 6018 update_sg_lb_stats(env, sg, load_idx, local_group, sgs); 6019 6020 if (local_group) 6021 goto next_group; 6022 6023 /* 6024 * In case the child domain prefers tasks go to siblings 6025 * first, lower the sg capacity factor to one so that we'll try 6026 * and move all the excess tasks away. We lower the capacity 6027 * of a group only if the local group has the capacity to fit 6028 * these excess tasks, i.e. nr_running < group_capacity_factor. The 6029 * extra check prevents the case where you always pull from the 6030 * heaviest group when it is already under-utilized (possible 6031 * with a large weight task outweighs the tasks on the system). 6032 */ 6033 if (prefer_sibling && sds->local && 6034 sds->local_stat.group_has_free_capacity) 6035 sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U); 6036 6037 if (update_sd_pick_busiest(env, sds, sg, sgs)) { 6038 sds->busiest = sg; 6039 sds->busiest_stat = *sgs; 6040 } 6041 6042 next_group: 6043 /* Now, start updating sd_lb_stats */ 6044 sds->total_load += sgs->group_load; 6045 sds->total_capacity += sgs->group_capacity; 6046 6047 sg = sg->next; 6048 } while (sg != env->sd->groups); 6049 6050 if (env->sd->flags & SD_NUMA) 6051 env->fbq_type = fbq_classify_group(&sds->busiest_stat); 6052 } 6053 6054 /** 6055 * check_asym_packing - Check to see if the group is packed into the 6056 * sched doman. 6057 * 6058 * This is primarily intended to used at the sibling level. Some 6059 * cores like POWER7 prefer to use lower numbered SMT threads. In the 6060 * case of POWER7, it can move to lower SMT modes only when higher 6061 * threads are idle. When in lower SMT modes, the threads will 6062 * perform better since they share less core resources. Hence when we 6063 * have idle threads, we want them to be the higher ones. 6064 * 6065 * This packing function is run on idle threads. It checks to see if 6066 * the busiest CPU in this domain (core in the P7 case) has a higher 6067 * CPU number than the packing function is being run on. Here we are 6068 * assuming lower CPU number will be equivalent to lower a SMT thread 6069 * number. 6070 * 6071 * Return: 1 when packing is required and a task should be moved to 6072 * this CPU. The amount of the imbalance is returned in *imbalance. 6073 * 6074 * @env: The load balancing environment. 6075 * @sds: Statistics of the sched_domain which is to be packed 6076 */ 6077 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) 6078 { 6079 int busiest_cpu; 6080 6081 if (!(env->sd->flags & SD_ASYM_PACKING)) 6082 return 0; 6083 6084 if (!sds->busiest) 6085 return 0; 6086 6087 busiest_cpu = group_first_cpu(sds->busiest); 6088 if (env->dst_cpu > busiest_cpu) 6089 return 0; 6090 6091 env->imbalance = DIV_ROUND_CLOSEST( 6092 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, 6093 SCHED_CAPACITY_SCALE); 6094 6095 return 1; 6096 } 6097 6098 /** 6099 * fix_small_imbalance - Calculate the minor imbalance that exists 6100 * amongst the groups of a sched_domain, during 6101 * load balancing. 6102 * @env: The load balancing environment. 6103 * @sds: Statistics of the sched_domain whose imbalance is to be calculated. 6104 */ 6105 static inline 6106 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 6107 { 6108 unsigned long tmp, capa_now = 0, capa_move = 0; 6109 unsigned int imbn = 2; 6110 unsigned long scaled_busy_load_per_task; 6111 struct sg_lb_stats *local, *busiest; 6112 6113 local = &sds->local_stat; 6114 busiest = &sds->busiest_stat; 6115 6116 if (!local->sum_nr_running) 6117 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu); 6118 else if (busiest->load_per_task > local->load_per_task) 6119 imbn = 1; 6120 6121 scaled_busy_load_per_task = 6122 (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 6123 busiest->group_capacity; 6124 6125 if (busiest->avg_load + scaled_busy_load_per_task >= 6126 local->avg_load + (scaled_busy_load_per_task * imbn)) { 6127 env->imbalance = busiest->load_per_task; 6128 return; 6129 } 6130 6131 /* 6132 * OK, we don't have enough imbalance to justify moving tasks, 6133 * however we may be able to increase total CPU capacity used by 6134 * moving them. 6135 */ 6136 6137 capa_now += busiest->group_capacity * 6138 min(busiest->load_per_task, busiest->avg_load); 6139 capa_now += local->group_capacity * 6140 min(local->load_per_task, local->avg_load); 6141 capa_now /= SCHED_CAPACITY_SCALE; 6142 6143 /* Amount of load we'd subtract */ 6144 if (busiest->avg_load > scaled_busy_load_per_task) { 6145 capa_move += busiest->group_capacity * 6146 min(busiest->load_per_task, 6147 busiest->avg_load - scaled_busy_load_per_task); 6148 } 6149 6150 /* Amount of load we'd add */ 6151 if (busiest->avg_load * busiest->group_capacity < 6152 busiest->load_per_task * SCHED_CAPACITY_SCALE) { 6153 tmp = (busiest->avg_load * busiest->group_capacity) / 6154 local->group_capacity; 6155 } else { 6156 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 6157 local->group_capacity; 6158 } 6159 capa_move += local->group_capacity * 6160 min(local->load_per_task, local->avg_load + tmp); 6161 capa_move /= SCHED_CAPACITY_SCALE; 6162 6163 /* Move if we gain throughput */ 6164 if (capa_move > capa_now) 6165 env->imbalance = busiest->load_per_task; 6166 } 6167 6168 /** 6169 * calculate_imbalance - Calculate the amount of imbalance present within the 6170 * groups of a given sched_domain during load balance. 6171 * @env: load balance environment 6172 * @sds: statistics of the sched_domain whose imbalance is to be calculated. 6173 */ 6174 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 6175 { 6176 unsigned long max_pull, load_above_capacity = ~0UL; 6177 struct sg_lb_stats *local, *busiest; 6178 6179 local = &sds->local_stat; 6180 busiest = &sds->busiest_stat; 6181 6182 if (busiest->group_imb) { 6183 /* 6184 * In the group_imb case we cannot rely on group-wide averages 6185 * to ensure cpu-load equilibrium, look at wider averages. XXX 6186 */ 6187 busiest->load_per_task = 6188 min(busiest->load_per_task, sds->avg_load); 6189 } 6190 6191 /* 6192 * In the presence of smp nice balancing, certain scenarios can have 6193 * max load less than avg load(as we skip the groups at or below 6194 * its cpu_capacity, while calculating max_load..) 6195 */ 6196 if (busiest->avg_load <= sds->avg_load || 6197 local->avg_load >= sds->avg_load) { 6198 env->imbalance = 0; 6199 return fix_small_imbalance(env, sds); 6200 } 6201 6202 if (!busiest->group_imb) { 6203 /* 6204 * Don't want to pull so many tasks that a group would go idle. 6205 * Except of course for the group_imb case, since then we might 6206 * have to drop below capacity to reach cpu-load equilibrium. 6207 */ 6208 load_above_capacity = 6209 (busiest->sum_nr_running - busiest->group_capacity_factor); 6210 6211 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE); 6212 load_above_capacity /= busiest->group_capacity; 6213 } 6214 6215 /* 6216 * We're trying to get all the cpus to the average_load, so we don't 6217 * want to push ourselves above the average load, nor do we wish to 6218 * reduce the max loaded cpu below the average load. At the same time, 6219 * we also don't want to reduce the group load below the group capacity 6220 * (so that we can implement power-savings policies etc). Thus we look 6221 * for the minimum possible imbalance. 6222 */ 6223 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity); 6224 6225 /* How much load to actually move to equalise the imbalance */ 6226 env->imbalance = min( 6227 max_pull * busiest->group_capacity, 6228 (sds->avg_load - local->avg_load) * local->group_capacity 6229 ) / SCHED_CAPACITY_SCALE; 6230 6231 /* 6232 * if *imbalance is less than the average load per runnable task 6233 * there is no guarantee that any tasks will be moved so we'll have 6234 * a think about bumping its value to force at least one task to be 6235 * moved 6236 */ 6237 if (env->imbalance < busiest->load_per_task) 6238 return fix_small_imbalance(env, sds); 6239 } 6240 6241 /******* find_busiest_group() helpers end here *********************/ 6242 6243 /** 6244 * find_busiest_group - Returns the busiest group within the sched_domain 6245 * if there is an imbalance. If there isn't an imbalance, and 6246 * the user has opted for power-savings, it returns a group whose 6247 * CPUs can be put to idle by rebalancing those tasks elsewhere, if 6248 * such a group exists. 6249 * 6250 * Also calculates the amount of weighted load which should be moved 6251 * to restore balance. 6252 * 6253 * @env: The load balancing environment. 6254 * 6255 * Return: - The busiest group if imbalance exists. 6256 * - If no imbalance and user has opted for power-savings balance, 6257 * return the least loaded group whose CPUs can be 6258 * put to idle by rebalancing its tasks onto our group. 6259 */ 6260 static struct sched_group *find_busiest_group(struct lb_env *env) 6261 { 6262 struct sg_lb_stats *local, *busiest; 6263 struct sd_lb_stats sds; 6264 6265 init_sd_lb_stats(&sds); 6266 6267 /* 6268 * Compute the various statistics relavent for load balancing at 6269 * this level. 6270 */ 6271 update_sd_lb_stats(env, &sds); 6272 local = &sds.local_stat; 6273 busiest = &sds.busiest_stat; 6274 6275 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) && 6276 check_asym_packing(env, &sds)) 6277 return sds.busiest; 6278 6279 /* There is no busy sibling group to pull tasks from */ 6280 if (!sds.busiest || busiest->sum_nr_running == 0) 6281 goto out_balanced; 6282 6283 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load) 6284 / sds.total_capacity; 6285 6286 /* 6287 * If the busiest group is imbalanced the below checks don't 6288 * work because they assume all things are equal, which typically 6289 * isn't true due to cpus_allowed constraints and the like. 6290 */ 6291 if (busiest->group_imb) 6292 goto force_balance; 6293 6294 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ 6295 if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity && 6296 !busiest->group_has_free_capacity) 6297 goto force_balance; 6298 6299 /* 6300 * If the local group is more busy than the selected busiest group 6301 * don't try and pull any tasks. 6302 */ 6303 if (local->avg_load >= busiest->avg_load) 6304 goto out_balanced; 6305 6306 /* 6307 * Don't pull any tasks if this group is already above the domain 6308 * average load. 6309 */ 6310 if (local->avg_load >= sds.avg_load) 6311 goto out_balanced; 6312 6313 if (env->idle == CPU_IDLE) { 6314 /* 6315 * This cpu is idle. If the busiest group load doesn't 6316 * have more tasks than the number of available cpu's and 6317 * there is no imbalance between this and busiest group 6318 * wrt to idle cpu's, it is balanced. 6319 */ 6320 if ((local->idle_cpus < busiest->idle_cpus) && 6321 busiest->sum_nr_running <= busiest->group_weight) 6322 goto out_balanced; 6323 } else { 6324 /* 6325 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use 6326 * imbalance_pct to be conservative. 6327 */ 6328 if (100 * busiest->avg_load <= 6329 env->sd->imbalance_pct * local->avg_load) 6330 goto out_balanced; 6331 } 6332 6333 force_balance: 6334 /* Looks like there is an imbalance. Compute it */ 6335 calculate_imbalance(env, &sds); 6336 return sds.busiest; 6337 6338 out_balanced: 6339 env->imbalance = 0; 6340 return NULL; 6341 } 6342 6343 /* 6344 * find_busiest_queue - find the busiest runqueue among the cpus in group. 6345 */ 6346 static struct rq *find_busiest_queue(struct lb_env *env, 6347 struct sched_group *group) 6348 { 6349 struct rq *busiest = NULL, *rq; 6350 unsigned long busiest_load = 0, busiest_capacity = 1; 6351 int i; 6352 6353 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 6354 unsigned long capacity, capacity_factor, wl; 6355 enum fbq_type rt; 6356 6357 rq = cpu_rq(i); 6358 rt = fbq_classify_rq(rq); 6359 6360 /* 6361 * We classify groups/runqueues into three groups: 6362 * - regular: there are !numa tasks 6363 * - remote: there are numa tasks that run on the 'wrong' node 6364 * - all: there is no distinction 6365 * 6366 * In order to avoid migrating ideally placed numa tasks, 6367 * ignore those when there's better options. 6368 * 6369 * If we ignore the actual busiest queue to migrate another 6370 * task, the next balance pass can still reduce the busiest 6371 * queue by moving tasks around inside the node. 6372 * 6373 * If we cannot move enough load due to this classification 6374 * the next pass will adjust the group classification and 6375 * allow migration of more tasks. 6376 * 6377 * Both cases only affect the total convergence complexity. 6378 */ 6379 if (rt > env->fbq_type) 6380 continue; 6381 6382 capacity = capacity_of(i); 6383 capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE); 6384 if (!capacity_factor) 6385 capacity_factor = fix_small_capacity(env->sd, group); 6386 6387 wl = weighted_cpuload(i); 6388 6389 /* 6390 * When comparing with imbalance, use weighted_cpuload() 6391 * which is not scaled with the cpu capacity. 6392 */ 6393 if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance) 6394 continue; 6395 6396 /* 6397 * For the load comparisons with the other cpu's, consider 6398 * the weighted_cpuload() scaled with the cpu capacity, so 6399 * that the load can be moved away from the cpu that is 6400 * potentially running at a lower capacity. 6401 * 6402 * Thus we're looking for max(wl_i / capacity_i), crosswise 6403 * multiplication to rid ourselves of the division works out 6404 * to: wl_i * capacity_j > wl_j * capacity_i; where j is 6405 * our previous maximum. 6406 */ 6407 if (wl * busiest_capacity > busiest_load * capacity) { 6408 busiest_load = wl; 6409 busiest_capacity = capacity; 6410 busiest = rq; 6411 } 6412 } 6413 6414 return busiest; 6415 } 6416 6417 /* 6418 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but 6419 * so long as it is large enough. 6420 */ 6421 #define MAX_PINNED_INTERVAL 512 6422 6423 /* Working cpumask for load_balance and load_balance_newidle. */ 6424 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); 6425 6426 static int need_active_balance(struct lb_env *env) 6427 { 6428 struct sched_domain *sd = env->sd; 6429 6430 if (env->idle == CPU_NEWLY_IDLE) { 6431 6432 /* 6433 * ASYM_PACKING needs to force migrate tasks from busy but 6434 * higher numbered CPUs in order to pack all tasks in the 6435 * lowest numbered CPUs. 6436 */ 6437 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) 6438 return 1; 6439 } 6440 6441 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); 6442 } 6443 6444 static int active_load_balance_cpu_stop(void *data); 6445 6446 static int should_we_balance(struct lb_env *env) 6447 { 6448 struct sched_group *sg = env->sd->groups; 6449 struct cpumask *sg_cpus, *sg_mask; 6450 int cpu, balance_cpu = -1; 6451 6452 /* 6453 * In the newly idle case, we will allow all the cpu's 6454 * to do the newly idle load balance. 6455 */ 6456 if (env->idle == CPU_NEWLY_IDLE) 6457 return 1; 6458 6459 sg_cpus = sched_group_cpus(sg); 6460 sg_mask = sched_group_mask(sg); 6461 /* Try to find first idle cpu */ 6462 for_each_cpu_and(cpu, sg_cpus, env->cpus) { 6463 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu)) 6464 continue; 6465 6466 balance_cpu = cpu; 6467 break; 6468 } 6469 6470 if (balance_cpu == -1) 6471 balance_cpu = group_balance_cpu(sg); 6472 6473 /* 6474 * First idle cpu or the first cpu(busiest) in this sched group 6475 * is eligible for doing load balancing at this and above domains. 6476 */ 6477 return balance_cpu == env->dst_cpu; 6478 } 6479 6480 /* 6481 * Check this_cpu to ensure it is balanced within domain. Attempt to move 6482 * tasks if there is an imbalance. 6483 */ 6484 static int load_balance(int this_cpu, struct rq *this_rq, 6485 struct sched_domain *sd, enum cpu_idle_type idle, 6486 int *continue_balancing) 6487 { 6488 int ld_moved, cur_ld_moved, active_balance = 0; 6489 struct sched_domain *sd_parent = sd->parent; 6490 struct sched_group *group; 6491 struct rq *busiest; 6492 unsigned long flags; 6493 struct cpumask *cpus = __get_cpu_var(load_balance_mask); 6494 6495 struct lb_env env = { 6496 .sd = sd, 6497 .dst_cpu = this_cpu, 6498 .dst_rq = this_rq, 6499 .dst_grpmask = sched_group_cpus(sd->groups), 6500 .idle = idle, 6501 .loop_break = sched_nr_migrate_break, 6502 .cpus = cpus, 6503 .fbq_type = all, 6504 }; 6505 6506 /* 6507 * For NEWLY_IDLE load_balancing, we don't need to consider 6508 * other cpus in our group 6509 */ 6510 if (idle == CPU_NEWLY_IDLE) 6511 env.dst_grpmask = NULL; 6512 6513 cpumask_copy(cpus, cpu_active_mask); 6514 6515 schedstat_inc(sd, lb_count[idle]); 6516 6517 redo: 6518 if (!should_we_balance(&env)) { 6519 *continue_balancing = 0; 6520 goto out_balanced; 6521 } 6522 6523 group = find_busiest_group(&env); 6524 if (!group) { 6525 schedstat_inc(sd, lb_nobusyg[idle]); 6526 goto out_balanced; 6527 } 6528 6529 busiest = find_busiest_queue(&env, group); 6530 if (!busiest) { 6531 schedstat_inc(sd, lb_nobusyq[idle]); 6532 goto out_balanced; 6533 } 6534 6535 BUG_ON(busiest == env.dst_rq); 6536 6537 schedstat_add(sd, lb_imbalance[idle], env.imbalance); 6538 6539 ld_moved = 0; 6540 if (busiest->nr_running > 1) { 6541 /* 6542 * Attempt to move tasks. If find_busiest_group has found 6543 * an imbalance but busiest->nr_running <= 1, the group is 6544 * still unbalanced. ld_moved simply stays zero, so it is 6545 * correctly treated as an imbalance. 6546 */ 6547 env.flags |= LBF_ALL_PINNED; 6548 env.src_cpu = busiest->cpu; 6549 env.src_rq = busiest; 6550 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); 6551 6552 more_balance: 6553 local_irq_save(flags); 6554 double_rq_lock(env.dst_rq, busiest); 6555 6556 /* 6557 * cur_ld_moved - load moved in current iteration 6558 * ld_moved - cumulative load moved across iterations 6559 */ 6560 cur_ld_moved = move_tasks(&env); 6561 ld_moved += cur_ld_moved; 6562 double_rq_unlock(env.dst_rq, busiest); 6563 local_irq_restore(flags); 6564 6565 /* 6566 * some other cpu did the load balance for us. 6567 */ 6568 if (cur_ld_moved && env.dst_cpu != smp_processor_id()) 6569 resched_cpu(env.dst_cpu); 6570 6571 if (env.flags & LBF_NEED_BREAK) { 6572 env.flags &= ~LBF_NEED_BREAK; 6573 goto more_balance; 6574 } 6575 6576 /* 6577 * Revisit (affine) tasks on src_cpu that couldn't be moved to 6578 * us and move them to an alternate dst_cpu in our sched_group 6579 * where they can run. The upper limit on how many times we 6580 * iterate on same src_cpu is dependent on number of cpus in our 6581 * sched_group. 6582 * 6583 * This changes load balance semantics a bit on who can move 6584 * load to a given_cpu. In addition to the given_cpu itself 6585 * (or a ilb_cpu acting on its behalf where given_cpu is 6586 * nohz-idle), we now have balance_cpu in a position to move 6587 * load to given_cpu. In rare situations, this may cause 6588 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding 6589 * _independently_ and at _same_ time to move some load to 6590 * given_cpu) causing exceess load to be moved to given_cpu. 6591 * This however should not happen so much in practice and 6592 * moreover subsequent load balance cycles should correct the 6593 * excess load moved. 6594 */ 6595 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { 6596 6597 /* Prevent to re-select dst_cpu via env's cpus */ 6598 cpumask_clear_cpu(env.dst_cpu, env.cpus); 6599 6600 env.dst_rq = cpu_rq(env.new_dst_cpu); 6601 env.dst_cpu = env.new_dst_cpu; 6602 env.flags &= ~LBF_DST_PINNED; 6603 env.loop = 0; 6604 env.loop_break = sched_nr_migrate_break; 6605 6606 /* 6607 * Go back to "more_balance" rather than "redo" since we 6608 * need to continue with same src_cpu. 6609 */ 6610 goto more_balance; 6611 } 6612 6613 /* 6614 * We failed to reach balance because of affinity. 6615 */ 6616 if (sd_parent) { 6617 int *group_imbalance = &sd_parent->groups->sgc->imbalance; 6618 6619 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) { 6620 *group_imbalance = 1; 6621 } else if (*group_imbalance) 6622 *group_imbalance = 0; 6623 } 6624 6625 /* All tasks on this runqueue were pinned by CPU affinity */ 6626 if (unlikely(env.flags & LBF_ALL_PINNED)) { 6627 cpumask_clear_cpu(cpu_of(busiest), cpus); 6628 if (!cpumask_empty(cpus)) { 6629 env.loop = 0; 6630 env.loop_break = sched_nr_migrate_break; 6631 goto redo; 6632 } 6633 goto out_balanced; 6634 } 6635 } 6636 6637 if (!ld_moved) { 6638 schedstat_inc(sd, lb_failed[idle]); 6639 /* 6640 * Increment the failure counter only on periodic balance. 6641 * We do not want newidle balance, which can be very 6642 * frequent, pollute the failure counter causing 6643 * excessive cache_hot migrations and active balances. 6644 */ 6645 if (idle != CPU_NEWLY_IDLE) 6646 sd->nr_balance_failed++; 6647 6648 if (need_active_balance(&env)) { 6649 raw_spin_lock_irqsave(&busiest->lock, flags); 6650 6651 /* don't kick the active_load_balance_cpu_stop, 6652 * if the curr task on busiest cpu can't be 6653 * moved to this_cpu 6654 */ 6655 if (!cpumask_test_cpu(this_cpu, 6656 tsk_cpus_allowed(busiest->curr))) { 6657 raw_spin_unlock_irqrestore(&busiest->lock, 6658 flags); 6659 env.flags |= LBF_ALL_PINNED; 6660 goto out_one_pinned; 6661 } 6662 6663 /* 6664 * ->active_balance synchronizes accesses to 6665 * ->active_balance_work. Once set, it's cleared 6666 * only after active load balance is finished. 6667 */ 6668 if (!busiest->active_balance) { 6669 busiest->active_balance = 1; 6670 busiest->push_cpu = this_cpu; 6671 active_balance = 1; 6672 } 6673 raw_spin_unlock_irqrestore(&busiest->lock, flags); 6674 6675 if (active_balance) { 6676 stop_one_cpu_nowait(cpu_of(busiest), 6677 active_load_balance_cpu_stop, busiest, 6678 &busiest->active_balance_work); 6679 } 6680 6681 /* 6682 * We've kicked active balancing, reset the failure 6683 * counter. 6684 */ 6685 sd->nr_balance_failed = sd->cache_nice_tries+1; 6686 } 6687 } else 6688 sd->nr_balance_failed = 0; 6689 6690 if (likely(!active_balance)) { 6691 /* We were unbalanced, so reset the balancing interval */ 6692 sd->balance_interval = sd->min_interval; 6693 } else { 6694 /* 6695 * If we've begun active balancing, start to back off. This 6696 * case may not be covered by the all_pinned logic if there 6697 * is only 1 task on the busy runqueue (because we don't call 6698 * move_tasks). 6699 */ 6700 if (sd->balance_interval < sd->max_interval) 6701 sd->balance_interval *= 2; 6702 } 6703 6704 goto out; 6705 6706 out_balanced: 6707 schedstat_inc(sd, lb_balanced[idle]); 6708 6709 sd->nr_balance_failed = 0; 6710 6711 out_one_pinned: 6712 /* tune up the balancing interval */ 6713 if (((env.flags & LBF_ALL_PINNED) && 6714 sd->balance_interval < MAX_PINNED_INTERVAL) || 6715 (sd->balance_interval < sd->max_interval)) 6716 sd->balance_interval *= 2; 6717 6718 ld_moved = 0; 6719 out: 6720 return ld_moved; 6721 } 6722 6723 static inline unsigned long 6724 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) 6725 { 6726 unsigned long interval = sd->balance_interval; 6727 6728 if (cpu_busy) 6729 interval *= sd->busy_factor; 6730 6731 /* scale ms to jiffies */ 6732 interval = msecs_to_jiffies(interval); 6733 interval = clamp(interval, 1UL, max_load_balance_interval); 6734 6735 return interval; 6736 } 6737 6738 static inline void 6739 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance) 6740 { 6741 unsigned long interval, next; 6742 6743 interval = get_sd_balance_interval(sd, cpu_busy); 6744 next = sd->last_balance + interval; 6745 6746 if (time_after(*next_balance, next)) 6747 *next_balance = next; 6748 } 6749 6750 /* 6751 * idle_balance is called by schedule() if this_cpu is about to become 6752 * idle. Attempts to pull tasks from other CPUs. 6753 */ 6754 static int idle_balance(struct rq *this_rq) 6755 { 6756 unsigned long next_balance = jiffies + HZ; 6757 int this_cpu = this_rq->cpu; 6758 struct sched_domain *sd; 6759 int pulled_task = 0; 6760 u64 curr_cost = 0; 6761 6762 idle_enter_fair(this_rq); 6763 6764 /* 6765 * We must set idle_stamp _before_ calling idle_balance(), such that we 6766 * measure the duration of idle_balance() as idle time. 6767 */ 6768 this_rq->idle_stamp = rq_clock(this_rq); 6769 6770 if (this_rq->avg_idle < sysctl_sched_migration_cost) { 6771 rcu_read_lock(); 6772 sd = rcu_dereference_check_sched_domain(this_rq->sd); 6773 if (sd) 6774 update_next_balance(sd, 0, &next_balance); 6775 rcu_read_unlock(); 6776 6777 goto out; 6778 } 6779 6780 /* 6781 * Drop the rq->lock, but keep IRQ/preempt disabled. 6782 */ 6783 raw_spin_unlock(&this_rq->lock); 6784 6785 update_blocked_averages(this_cpu); 6786 rcu_read_lock(); 6787 for_each_domain(this_cpu, sd) { 6788 int continue_balancing = 1; 6789 u64 t0, domain_cost; 6790 6791 if (!(sd->flags & SD_LOAD_BALANCE)) 6792 continue; 6793 6794 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { 6795 update_next_balance(sd, 0, &next_balance); 6796 break; 6797 } 6798 6799 if (sd->flags & SD_BALANCE_NEWIDLE) { 6800 t0 = sched_clock_cpu(this_cpu); 6801 6802 pulled_task = load_balance(this_cpu, this_rq, 6803 sd, CPU_NEWLY_IDLE, 6804 &continue_balancing); 6805 6806 domain_cost = sched_clock_cpu(this_cpu) - t0; 6807 if (domain_cost > sd->max_newidle_lb_cost) 6808 sd->max_newidle_lb_cost = domain_cost; 6809 6810 curr_cost += domain_cost; 6811 } 6812 6813 update_next_balance(sd, 0, &next_balance); 6814 6815 /* 6816 * Stop searching for tasks to pull if there are 6817 * now runnable tasks on this rq. 6818 */ 6819 if (pulled_task || this_rq->nr_running > 0) 6820 break; 6821 } 6822 rcu_read_unlock(); 6823 6824 raw_spin_lock(&this_rq->lock); 6825 6826 if (curr_cost > this_rq->max_idle_balance_cost) 6827 this_rq->max_idle_balance_cost = curr_cost; 6828 6829 /* 6830 * While browsing the domains, we released the rq lock, a task could 6831 * have been enqueued in the meantime. Since we're not going idle, 6832 * pretend we pulled a task. 6833 */ 6834 if (this_rq->cfs.h_nr_running && !pulled_task) 6835 pulled_task = 1; 6836 6837 out: 6838 /* Move the next balance forward */ 6839 if (time_after(this_rq->next_balance, next_balance)) 6840 this_rq->next_balance = next_balance; 6841 6842 /* Is there a task of a high priority class? */ 6843 if (this_rq->nr_running != this_rq->cfs.h_nr_running) 6844 pulled_task = -1; 6845 6846 if (pulled_task) { 6847 idle_exit_fair(this_rq); 6848 this_rq->idle_stamp = 0; 6849 } 6850 6851 return pulled_task; 6852 } 6853 6854 /* 6855 * active_load_balance_cpu_stop is run by cpu stopper. It pushes 6856 * running tasks off the busiest CPU onto idle CPUs. It requires at 6857 * least 1 task to be running on each physical CPU where possible, and 6858 * avoids physical / logical imbalances. 6859 */ 6860 static int active_load_balance_cpu_stop(void *data) 6861 { 6862 struct rq *busiest_rq = data; 6863 int busiest_cpu = cpu_of(busiest_rq); 6864 int target_cpu = busiest_rq->push_cpu; 6865 struct rq *target_rq = cpu_rq(target_cpu); 6866 struct sched_domain *sd; 6867 6868 raw_spin_lock_irq(&busiest_rq->lock); 6869 6870 /* make sure the requested cpu hasn't gone down in the meantime */ 6871 if (unlikely(busiest_cpu != smp_processor_id() || 6872 !busiest_rq->active_balance)) 6873 goto out_unlock; 6874 6875 /* Is there any task to move? */ 6876 if (busiest_rq->nr_running <= 1) 6877 goto out_unlock; 6878 6879 /* 6880 * This condition is "impossible", if it occurs 6881 * we need to fix it. Originally reported by 6882 * Bjorn Helgaas on a 128-cpu setup. 6883 */ 6884 BUG_ON(busiest_rq == target_rq); 6885 6886 /* move a task from busiest_rq to target_rq */ 6887 double_lock_balance(busiest_rq, target_rq); 6888 6889 /* Search for an sd spanning us and the target CPU. */ 6890 rcu_read_lock(); 6891 for_each_domain(target_cpu, sd) { 6892 if ((sd->flags & SD_LOAD_BALANCE) && 6893 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) 6894 break; 6895 } 6896 6897 if (likely(sd)) { 6898 struct lb_env env = { 6899 .sd = sd, 6900 .dst_cpu = target_cpu, 6901 .dst_rq = target_rq, 6902 .src_cpu = busiest_rq->cpu, 6903 .src_rq = busiest_rq, 6904 .idle = CPU_IDLE, 6905 }; 6906 6907 schedstat_inc(sd, alb_count); 6908 6909 if (move_one_task(&env)) 6910 schedstat_inc(sd, alb_pushed); 6911 else 6912 schedstat_inc(sd, alb_failed); 6913 } 6914 rcu_read_unlock(); 6915 double_unlock_balance(busiest_rq, target_rq); 6916 out_unlock: 6917 busiest_rq->active_balance = 0; 6918 raw_spin_unlock_irq(&busiest_rq->lock); 6919 return 0; 6920 } 6921 6922 static inline int on_null_domain(struct rq *rq) 6923 { 6924 return unlikely(!rcu_dereference_sched(rq->sd)); 6925 } 6926 6927 #ifdef CONFIG_NO_HZ_COMMON 6928 /* 6929 * idle load balancing details 6930 * - When one of the busy CPUs notice that there may be an idle rebalancing 6931 * needed, they will kick the idle load balancer, which then does idle 6932 * load balancing for all the idle CPUs. 6933 */ 6934 static struct { 6935 cpumask_var_t idle_cpus_mask; 6936 atomic_t nr_cpus; 6937 unsigned long next_balance; /* in jiffy units */ 6938 } nohz ____cacheline_aligned; 6939 6940 static inline int find_new_ilb(void) 6941 { 6942 int ilb = cpumask_first(nohz.idle_cpus_mask); 6943 6944 if (ilb < nr_cpu_ids && idle_cpu(ilb)) 6945 return ilb; 6946 6947 return nr_cpu_ids; 6948 } 6949 6950 /* 6951 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the 6952 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle 6953 * CPU (if there is one). 6954 */ 6955 static void nohz_balancer_kick(void) 6956 { 6957 int ilb_cpu; 6958 6959 nohz.next_balance++; 6960 6961 ilb_cpu = find_new_ilb(); 6962 6963 if (ilb_cpu >= nr_cpu_ids) 6964 return; 6965 6966 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu))) 6967 return; 6968 /* 6969 * Use smp_send_reschedule() instead of resched_cpu(). 6970 * This way we generate a sched IPI on the target cpu which 6971 * is idle. And the softirq performing nohz idle load balance 6972 * will be run before returning from the IPI. 6973 */ 6974 smp_send_reschedule(ilb_cpu); 6975 return; 6976 } 6977 6978 static inline void nohz_balance_exit_idle(int cpu) 6979 { 6980 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { 6981 /* 6982 * Completely isolated CPUs don't ever set, so we must test. 6983 */ 6984 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { 6985 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); 6986 atomic_dec(&nohz.nr_cpus); 6987 } 6988 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 6989 } 6990 } 6991 6992 static inline void set_cpu_sd_state_busy(void) 6993 { 6994 struct sched_domain *sd; 6995 int cpu = smp_processor_id(); 6996 6997 rcu_read_lock(); 6998 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 6999 7000 if (!sd || !sd->nohz_idle) 7001 goto unlock; 7002 sd->nohz_idle = 0; 7003 7004 atomic_inc(&sd->groups->sgc->nr_busy_cpus); 7005 unlock: 7006 rcu_read_unlock(); 7007 } 7008 7009 void set_cpu_sd_state_idle(void) 7010 { 7011 struct sched_domain *sd; 7012 int cpu = smp_processor_id(); 7013 7014 rcu_read_lock(); 7015 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 7016 7017 if (!sd || sd->nohz_idle) 7018 goto unlock; 7019 sd->nohz_idle = 1; 7020 7021 atomic_dec(&sd->groups->sgc->nr_busy_cpus); 7022 unlock: 7023 rcu_read_unlock(); 7024 } 7025 7026 /* 7027 * This routine will record that the cpu is going idle with tick stopped. 7028 * This info will be used in performing idle load balancing in the future. 7029 */ 7030 void nohz_balance_enter_idle(int cpu) 7031 { 7032 /* 7033 * If this cpu is going down, then nothing needs to be done. 7034 */ 7035 if (!cpu_active(cpu)) 7036 return; 7037 7038 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) 7039 return; 7040 7041 /* 7042 * If we're a completely isolated CPU, we don't play. 7043 */ 7044 if (on_null_domain(cpu_rq(cpu))) 7045 return; 7046 7047 cpumask_set_cpu(cpu, nohz.idle_cpus_mask); 7048 atomic_inc(&nohz.nr_cpus); 7049 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 7050 } 7051 7052 static int sched_ilb_notifier(struct notifier_block *nfb, 7053 unsigned long action, void *hcpu) 7054 { 7055 switch (action & ~CPU_TASKS_FROZEN) { 7056 case CPU_DYING: 7057 nohz_balance_exit_idle(smp_processor_id()); 7058 return NOTIFY_OK; 7059 default: 7060 return NOTIFY_DONE; 7061 } 7062 } 7063 #endif 7064 7065 static DEFINE_SPINLOCK(balancing); 7066 7067 /* 7068 * Scale the max load_balance interval with the number of CPUs in the system. 7069 * This trades load-balance latency on larger machines for less cross talk. 7070 */ 7071 void update_max_interval(void) 7072 { 7073 max_load_balance_interval = HZ*num_online_cpus()/10; 7074 } 7075 7076 /* 7077 * It checks each scheduling domain to see if it is due to be balanced, 7078 * and initiates a balancing operation if so. 7079 * 7080 * Balancing parameters are set up in init_sched_domains. 7081 */ 7082 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) 7083 { 7084 int continue_balancing = 1; 7085 int cpu = rq->cpu; 7086 unsigned long interval; 7087 struct sched_domain *sd; 7088 /* Earliest time when we have to do rebalance again */ 7089 unsigned long next_balance = jiffies + 60*HZ; 7090 int update_next_balance = 0; 7091 int need_serialize, need_decay = 0; 7092 u64 max_cost = 0; 7093 7094 update_blocked_averages(cpu); 7095 7096 rcu_read_lock(); 7097 for_each_domain(cpu, sd) { 7098 /* 7099 * Decay the newidle max times here because this is a regular 7100 * visit to all the domains. Decay ~1% per second. 7101 */ 7102 if (time_after(jiffies, sd->next_decay_max_lb_cost)) { 7103 sd->max_newidle_lb_cost = 7104 (sd->max_newidle_lb_cost * 253) / 256; 7105 sd->next_decay_max_lb_cost = jiffies + HZ; 7106 need_decay = 1; 7107 } 7108 max_cost += sd->max_newidle_lb_cost; 7109 7110 if (!(sd->flags & SD_LOAD_BALANCE)) 7111 continue; 7112 7113 /* 7114 * Stop the load balance at this level. There is another 7115 * CPU in our sched group which is doing load balancing more 7116 * actively. 7117 */ 7118 if (!continue_balancing) { 7119 if (need_decay) 7120 continue; 7121 break; 7122 } 7123 7124 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 7125 7126 need_serialize = sd->flags & SD_SERIALIZE; 7127 if (need_serialize) { 7128 if (!spin_trylock(&balancing)) 7129 goto out; 7130 } 7131 7132 if (time_after_eq(jiffies, sd->last_balance + interval)) { 7133 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { 7134 /* 7135 * The LBF_DST_PINNED logic could have changed 7136 * env->dst_cpu, so we can't know our idle 7137 * state even if we migrated tasks. Update it. 7138 */ 7139 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; 7140 } 7141 sd->last_balance = jiffies; 7142 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 7143 } 7144 if (need_serialize) 7145 spin_unlock(&balancing); 7146 out: 7147 if (time_after(next_balance, sd->last_balance + interval)) { 7148 next_balance = sd->last_balance + interval; 7149 update_next_balance = 1; 7150 } 7151 } 7152 if (need_decay) { 7153 /* 7154 * Ensure the rq-wide value also decays but keep it at a 7155 * reasonable floor to avoid funnies with rq->avg_idle. 7156 */ 7157 rq->max_idle_balance_cost = 7158 max((u64)sysctl_sched_migration_cost, max_cost); 7159 } 7160 rcu_read_unlock(); 7161 7162 /* 7163 * next_balance will be updated only when there is a need. 7164 * When the cpu is attached to null domain for ex, it will not be 7165 * updated. 7166 */ 7167 if (likely(update_next_balance)) 7168 rq->next_balance = next_balance; 7169 } 7170 7171 #ifdef CONFIG_NO_HZ_COMMON 7172 /* 7173 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the 7174 * rebalancing for all the cpus for whom scheduler ticks are stopped. 7175 */ 7176 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) 7177 { 7178 int this_cpu = this_rq->cpu; 7179 struct rq *rq; 7180 int balance_cpu; 7181 7182 if (idle != CPU_IDLE || 7183 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) 7184 goto end; 7185 7186 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { 7187 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) 7188 continue; 7189 7190 /* 7191 * If this cpu gets work to do, stop the load balancing 7192 * work being done for other cpus. Next load 7193 * balancing owner will pick it up. 7194 */ 7195 if (need_resched()) 7196 break; 7197 7198 rq = cpu_rq(balance_cpu); 7199 7200 /* 7201 * If time for next balance is due, 7202 * do the balance. 7203 */ 7204 if (time_after_eq(jiffies, rq->next_balance)) { 7205 raw_spin_lock_irq(&rq->lock); 7206 update_rq_clock(rq); 7207 update_idle_cpu_load(rq); 7208 raw_spin_unlock_irq(&rq->lock); 7209 rebalance_domains(rq, CPU_IDLE); 7210 } 7211 7212 if (time_after(this_rq->next_balance, rq->next_balance)) 7213 this_rq->next_balance = rq->next_balance; 7214 } 7215 nohz.next_balance = this_rq->next_balance; 7216 end: 7217 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)); 7218 } 7219 7220 /* 7221 * Current heuristic for kicking the idle load balancer in the presence 7222 * of an idle cpu is the system. 7223 * - This rq has more than one task. 7224 * - At any scheduler domain level, this cpu's scheduler group has multiple 7225 * busy cpu's exceeding the group's capacity. 7226 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler 7227 * domain span are idle. 7228 */ 7229 static inline int nohz_kick_needed(struct rq *rq) 7230 { 7231 unsigned long now = jiffies; 7232 struct sched_domain *sd; 7233 struct sched_group_capacity *sgc; 7234 int nr_busy, cpu = rq->cpu; 7235 7236 if (unlikely(rq->idle_balance)) 7237 return 0; 7238 7239 /* 7240 * We may be recently in ticked or tickless idle mode. At the first 7241 * busy tick after returning from idle, we will update the busy stats. 7242 */ 7243 set_cpu_sd_state_busy(); 7244 nohz_balance_exit_idle(cpu); 7245 7246 /* 7247 * None are in tickless mode and hence no need for NOHZ idle load 7248 * balancing. 7249 */ 7250 if (likely(!atomic_read(&nohz.nr_cpus))) 7251 return 0; 7252 7253 if (time_before(now, nohz.next_balance)) 7254 return 0; 7255 7256 if (rq->nr_running >= 2) 7257 goto need_kick; 7258 7259 rcu_read_lock(); 7260 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 7261 7262 if (sd) { 7263 sgc = sd->groups->sgc; 7264 nr_busy = atomic_read(&sgc->nr_busy_cpus); 7265 7266 if (nr_busy > 1) 7267 goto need_kick_unlock; 7268 } 7269 7270 sd = rcu_dereference(per_cpu(sd_asym, cpu)); 7271 7272 if (sd && (cpumask_first_and(nohz.idle_cpus_mask, 7273 sched_domain_span(sd)) < cpu)) 7274 goto need_kick_unlock; 7275 7276 rcu_read_unlock(); 7277 return 0; 7278 7279 need_kick_unlock: 7280 rcu_read_unlock(); 7281 need_kick: 7282 return 1; 7283 } 7284 #else 7285 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { } 7286 #endif 7287 7288 /* 7289 * run_rebalance_domains is triggered when needed from the scheduler tick. 7290 * Also triggered for nohz idle balancing (with nohz_balancing_kick set). 7291 */ 7292 static void run_rebalance_domains(struct softirq_action *h) 7293 { 7294 struct rq *this_rq = this_rq(); 7295 enum cpu_idle_type idle = this_rq->idle_balance ? 7296 CPU_IDLE : CPU_NOT_IDLE; 7297 7298 rebalance_domains(this_rq, idle); 7299 7300 /* 7301 * If this cpu has a pending nohz_balance_kick, then do the 7302 * balancing on behalf of the other idle cpus whose ticks are 7303 * stopped. 7304 */ 7305 nohz_idle_balance(this_rq, idle); 7306 } 7307 7308 /* 7309 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. 7310 */ 7311 void trigger_load_balance(struct rq *rq) 7312 { 7313 /* Don't need to rebalance while attached to NULL domain */ 7314 if (unlikely(on_null_domain(rq))) 7315 return; 7316 7317 if (time_after_eq(jiffies, rq->next_balance)) 7318 raise_softirq(SCHED_SOFTIRQ); 7319 #ifdef CONFIG_NO_HZ_COMMON 7320 if (nohz_kick_needed(rq)) 7321 nohz_balancer_kick(); 7322 #endif 7323 } 7324 7325 static void rq_online_fair(struct rq *rq) 7326 { 7327 update_sysctl(); 7328 } 7329 7330 static void rq_offline_fair(struct rq *rq) 7331 { 7332 update_sysctl(); 7333 7334 /* Ensure any throttled groups are reachable by pick_next_task */ 7335 unthrottle_offline_cfs_rqs(rq); 7336 } 7337 7338 #endif /* CONFIG_SMP */ 7339 7340 /* 7341 * scheduler tick hitting a task of our scheduling class: 7342 */ 7343 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) 7344 { 7345 struct cfs_rq *cfs_rq; 7346 struct sched_entity *se = &curr->se; 7347 7348 for_each_sched_entity(se) { 7349 cfs_rq = cfs_rq_of(se); 7350 entity_tick(cfs_rq, se, queued); 7351 } 7352 7353 if (numabalancing_enabled) 7354 task_tick_numa(rq, curr); 7355 7356 update_rq_runnable_avg(rq, 1); 7357 } 7358 7359 /* 7360 * called on fork with the child task as argument from the parent's context 7361 * - child not yet on the tasklist 7362 * - preemption disabled 7363 */ 7364 static void task_fork_fair(struct task_struct *p) 7365 { 7366 struct cfs_rq *cfs_rq; 7367 struct sched_entity *se = &p->se, *curr; 7368 int this_cpu = smp_processor_id(); 7369 struct rq *rq = this_rq(); 7370 unsigned long flags; 7371 7372 raw_spin_lock_irqsave(&rq->lock, flags); 7373 7374 update_rq_clock(rq); 7375 7376 cfs_rq = task_cfs_rq(current); 7377 curr = cfs_rq->curr; 7378 7379 /* 7380 * Not only the cpu but also the task_group of the parent might have 7381 * been changed after parent->se.parent,cfs_rq were copied to 7382 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those 7383 * of child point to valid ones. 7384 */ 7385 rcu_read_lock(); 7386 __set_task_cpu(p, this_cpu); 7387 rcu_read_unlock(); 7388 7389 update_curr(cfs_rq); 7390 7391 if (curr) 7392 se->vruntime = curr->vruntime; 7393 place_entity(cfs_rq, se, 1); 7394 7395 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { 7396 /* 7397 * Upon rescheduling, sched_class::put_prev_task() will place 7398 * 'current' within the tree based on its new key value. 7399 */ 7400 swap(curr->vruntime, se->vruntime); 7401 resched_task(rq->curr); 7402 } 7403 7404 se->vruntime -= cfs_rq->min_vruntime; 7405 7406 raw_spin_unlock_irqrestore(&rq->lock, flags); 7407 } 7408 7409 /* 7410 * Priority of the task has changed. Check to see if we preempt 7411 * the current task. 7412 */ 7413 static void 7414 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) 7415 { 7416 if (!p->se.on_rq) 7417 return; 7418 7419 /* 7420 * Reschedule if we are currently running on this runqueue and 7421 * our priority decreased, or if we are not currently running on 7422 * this runqueue and our priority is higher than the current's 7423 */ 7424 if (rq->curr == p) { 7425 if (p->prio > oldprio) 7426 resched_task(rq->curr); 7427 } else 7428 check_preempt_curr(rq, p, 0); 7429 } 7430 7431 static void switched_from_fair(struct rq *rq, struct task_struct *p) 7432 { 7433 struct sched_entity *se = &p->se; 7434 struct cfs_rq *cfs_rq = cfs_rq_of(se); 7435 7436 /* 7437 * Ensure the task's vruntime is normalized, so that when it's 7438 * switched back to the fair class the enqueue_entity(.flags=0) will 7439 * do the right thing. 7440 * 7441 * If it's on_rq, then the dequeue_entity(.flags=0) will already 7442 * have normalized the vruntime, if it's !on_rq, then only when 7443 * the task is sleeping will it still have non-normalized vruntime. 7444 */ 7445 if (!p->on_rq && p->state != TASK_RUNNING) { 7446 /* 7447 * Fix up our vruntime so that the current sleep doesn't 7448 * cause 'unlimited' sleep bonus. 7449 */ 7450 place_entity(cfs_rq, se, 0); 7451 se->vruntime -= cfs_rq->min_vruntime; 7452 } 7453 7454 #ifdef CONFIG_SMP 7455 /* 7456 * Remove our load from contribution when we leave sched_fair 7457 * and ensure we don't carry in an old decay_count if we 7458 * switch back. 7459 */ 7460 if (se->avg.decay_count) { 7461 __synchronize_entity_decay(se); 7462 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); 7463 } 7464 #endif 7465 } 7466 7467 /* 7468 * We switched to the sched_fair class. 7469 */ 7470 static void switched_to_fair(struct rq *rq, struct task_struct *p) 7471 { 7472 struct sched_entity *se = &p->se; 7473 #ifdef CONFIG_FAIR_GROUP_SCHED 7474 /* 7475 * Since the real-depth could have been changed (only FAIR 7476 * class maintain depth value), reset depth properly. 7477 */ 7478 se->depth = se->parent ? se->parent->depth + 1 : 0; 7479 #endif 7480 if (!se->on_rq) 7481 return; 7482 7483 /* 7484 * We were most likely switched from sched_rt, so 7485 * kick off the schedule if running, otherwise just see 7486 * if we can still preempt the current task. 7487 */ 7488 if (rq->curr == p) 7489 resched_task(rq->curr); 7490 else 7491 check_preempt_curr(rq, p, 0); 7492 } 7493 7494 /* Account for a task changing its policy or group. 7495 * 7496 * This routine is mostly called to set cfs_rq->curr field when a task 7497 * migrates between groups/classes. 7498 */ 7499 static void set_curr_task_fair(struct rq *rq) 7500 { 7501 struct sched_entity *se = &rq->curr->se; 7502 7503 for_each_sched_entity(se) { 7504 struct cfs_rq *cfs_rq = cfs_rq_of(se); 7505 7506 set_next_entity(cfs_rq, se); 7507 /* ensure bandwidth has been allocated on our new cfs_rq */ 7508 account_cfs_rq_runtime(cfs_rq, 0); 7509 } 7510 } 7511 7512 void init_cfs_rq(struct cfs_rq *cfs_rq) 7513 { 7514 cfs_rq->tasks_timeline = RB_ROOT; 7515 cfs_rq->min_vruntime = (u64)(-(1LL << 20)); 7516 #ifndef CONFIG_64BIT 7517 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 7518 #endif 7519 #ifdef CONFIG_SMP 7520 atomic64_set(&cfs_rq->decay_counter, 1); 7521 atomic_long_set(&cfs_rq->removed_load, 0); 7522 #endif 7523 } 7524 7525 #ifdef CONFIG_FAIR_GROUP_SCHED 7526 static void task_move_group_fair(struct task_struct *p, int on_rq) 7527 { 7528 struct sched_entity *se = &p->se; 7529 struct cfs_rq *cfs_rq; 7530 7531 /* 7532 * If the task was not on the rq at the time of this cgroup movement 7533 * it must have been asleep, sleeping tasks keep their ->vruntime 7534 * absolute on their old rq until wakeup (needed for the fair sleeper 7535 * bonus in place_entity()). 7536 * 7537 * If it was on the rq, we've just 'preempted' it, which does convert 7538 * ->vruntime to a relative base. 7539 * 7540 * Make sure both cases convert their relative position when migrating 7541 * to another cgroup's rq. This does somewhat interfere with the 7542 * fair sleeper stuff for the first placement, but who cares. 7543 */ 7544 /* 7545 * When !on_rq, vruntime of the task has usually NOT been normalized. 7546 * But there are some cases where it has already been normalized: 7547 * 7548 * - Moving a forked child which is waiting for being woken up by 7549 * wake_up_new_task(). 7550 * - Moving a task which has been woken up by try_to_wake_up() and 7551 * waiting for actually being woken up by sched_ttwu_pending(). 7552 * 7553 * To prevent boost or penalty in the new cfs_rq caused by delta 7554 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. 7555 */ 7556 if (!on_rq && (!se->sum_exec_runtime || p->state == TASK_WAKING)) 7557 on_rq = 1; 7558 7559 if (!on_rq) 7560 se->vruntime -= cfs_rq_of(se)->min_vruntime; 7561 set_task_rq(p, task_cpu(p)); 7562 se->depth = se->parent ? se->parent->depth + 1 : 0; 7563 if (!on_rq) { 7564 cfs_rq = cfs_rq_of(se); 7565 se->vruntime += cfs_rq->min_vruntime; 7566 #ifdef CONFIG_SMP 7567 /* 7568 * migrate_task_rq_fair() will have removed our previous 7569 * contribution, but we must synchronize for ongoing future 7570 * decay. 7571 */ 7572 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); 7573 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; 7574 #endif 7575 } 7576 } 7577 7578 void free_fair_sched_group(struct task_group *tg) 7579 { 7580 int i; 7581 7582 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); 7583 7584 for_each_possible_cpu(i) { 7585 if (tg->cfs_rq) 7586 kfree(tg->cfs_rq[i]); 7587 if (tg->se) 7588 kfree(tg->se[i]); 7589 } 7590 7591 kfree(tg->cfs_rq); 7592 kfree(tg->se); 7593 } 7594 7595 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 7596 { 7597 struct cfs_rq *cfs_rq; 7598 struct sched_entity *se; 7599 int i; 7600 7601 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL); 7602 if (!tg->cfs_rq) 7603 goto err; 7604 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL); 7605 if (!tg->se) 7606 goto err; 7607 7608 tg->shares = NICE_0_LOAD; 7609 7610 init_cfs_bandwidth(tg_cfs_bandwidth(tg)); 7611 7612 for_each_possible_cpu(i) { 7613 cfs_rq = kzalloc_node(sizeof(struct cfs_rq), 7614 GFP_KERNEL, cpu_to_node(i)); 7615 if (!cfs_rq) 7616 goto err; 7617 7618 se = kzalloc_node(sizeof(struct sched_entity), 7619 GFP_KERNEL, cpu_to_node(i)); 7620 if (!se) 7621 goto err_free_rq; 7622 7623 init_cfs_rq(cfs_rq); 7624 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); 7625 } 7626 7627 return 1; 7628 7629 err_free_rq: 7630 kfree(cfs_rq); 7631 err: 7632 return 0; 7633 } 7634 7635 void unregister_fair_sched_group(struct task_group *tg, int cpu) 7636 { 7637 struct rq *rq = cpu_rq(cpu); 7638 unsigned long flags; 7639 7640 /* 7641 * Only empty task groups can be destroyed; so we can speculatively 7642 * check on_list without danger of it being re-added. 7643 */ 7644 if (!tg->cfs_rq[cpu]->on_list) 7645 return; 7646 7647 raw_spin_lock_irqsave(&rq->lock, flags); 7648 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); 7649 raw_spin_unlock_irqrestore(&rq->lock, flags); 7650 } 7651 7652 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, 7653 struct sched_entity *se, int cpu, 7654 struct sched_entity *parent) 7655 { 7656 struct rq *rq = cpu_rq(cpu); 7657 7658 cfs_rq->tg = tg; 7659 cfs_rq->rq = rq; 7660 init_cfs_rq_runtime(cfs_rq); 7661 7662 tg->cfs_rq[cpu] = cfs_rq; 7663 tg->se[cpu] = se; 7664 7665 /* se could be NULL for root_task_group */ 7666 if (!se) 7667 return; 7668 7669 if (!parent) { 7670 se->cfs_rq = &rq->cfs; 7671 se->depth = 0; 7672 } else { 7673 se->cfs_rq = parent->my_q; 7674 se->depth = parent->depth + 1; 7675 } 7676 7677 se->my_q = cfs_rq; 7678 /* guarantee group entities always have weight */ 7679 update_load_set(&se->load, NICE_0_LOAD); 7680 se->parent = parent; 7681 } 7682 7683 static DEFINE_MUTEX(shares_mutex); 7684 7685 int sched_group_set_shares(struct task_group *tg, unsigned long shares) 7686 { 7687 int i; 7688 unsigned long flags; 7689 7690 /* 7691 * We can't change the weight of the root cgroup. 7692 */ 7693 if (!tg->se[0]) 7694 return -EINVAL; 7695 7696 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); 7697 7698 mutex_lock(&shares_mutex); 7699 if (tg->shares == shares) 7700 goto done; 7701 7702 tg->shares = shares; 7703 for_each_possible_cpu(i) { 7704 struct rq *rq = cpu_rq(i); 7705 struct sched_entity *se; 7706 7707 se = tg->se[i]; 7708 /* Propagate contribution to hierarchy */ 7709 raw_spin_lock_irqsave(&rq->lock, flags); 7710 7711 /* Possible calls to update_curr() need rq clock */ 7712 update_rq_clock(rq); 7713 for_each_sched_entity(se) 7714 update_cfs_shares(group_cfs_rq(se)); 7715 raw_spin_unlock_irqrestore(&rq->lock, flags); 7716 } 7717 7718 done: 7719 mutex_unlock(&shares_mutex); 7720 return 0; 7721 } 7722 #else /* CONFIG_FAIR_GROUP_SCHED */ 7723 7724 void free_fair_sched_group(struct task_group *tg) { } 7725 7726 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 7727 { 7728 return 1; 7729 } 7730 7731 void unregister_fair_sched_group(struct task_group *tg, int cpu) { } 7732 7733 #endif /* CONFIG_FAIR_GROUP_SCHED */ 7734 7735 7736 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) 7737 { 7738 struct sched_entity *se = &task->se; 7739 unsigned int rr_interval = 0; 7740 7741 /* 7742 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise 7743 * idle runqueue: 7744 */ 7745 if (rq->cfs.load.weight) 7746 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); 7747 7748 return rr_interval; 7749 } 7750 7751 /* 7752 * All the scheduling class methods: 7753 */ 7754 const struct sched_class fair_sched_class = { 7755 .next = &idle_sched_class, 7756 .enqueue_task = enqueue_task_fair, 7757 .dequeue_task = dequeue_task_fair, 7758 .yield_task = yield_task_fair, 7759 .yield_to_task = yield_to_task_fair, 7760 7761 .check_preempt_curr = check_preempt_wakeup, 7762 7763 .pick_next_task = pick_next_task_fair, 7764 .put_prev_task = put_prev_task_fair, 7765 7766 #ifdef CONFIG_SMP 7767 .select_task_rq = select_task_rq_fair, 7768 .migrate_task_rq = migrate_task_rq_fair, 7769 7770 .rq_online = rq_online_fair, 7771 .rq_offline = rq_offline_fair, 7772 7773 .task_waking = task_waking_fair, 7774 #endif 7775 7776 .set_curr_task = set_curr_task_fair, 7777 .task_tick = task_tick_fair, 7778 .task_fork = task_fork_fair, 7779 7780 .prio_changed = prio_changed_fair, 7781 .switched_from = switched_from_fair, 7782 .switched_to = switched_to_fair, 7783 7784 .get_rr_interval = get_rr_interval_fair, 7785 7786 #ifdef CONFIG_FAIR_GROUP_SCHED 7787 .task_move_group = task_move_group_fair, 7788 #endif 7789 }; 7790 7791 #ifdef CONFIG_SCHED_DEBUG 7792 void print_cfs_stats(struct seq_file *m, int cpu) 7793 { 7794 struct cfs_rq *cfs_rq; 7795 7796 rcu_read_lock(); 7797 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) 7798 print_cfs_rq(m, cpu, cfs_rq); 7799 rcu_read_unlock(); 7800 } 7801 #endif 7802 7803 __init void init_sched_fair_class(void) 7804 { 7805 #ifdef CONFIG_SMP 7806 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); 7807 7808 #ifdef CONFIG_NO_HZ_COMMON 7809 nohz.next_balance = jiffies; 7810 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); 7811 cpu_notifier(sched_ilb_notifier, 0); 7812 #endif 7813 #endif /* SMP */ 7814 7815 } 7816