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 30 #include <trace/events/sched.h> 31 32 #include "sched.h" 33 34 /* 35 * Targeted preemption latency for CPU-bound tasks: 36 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) 37 * 38 * NOTE: this latency value is not the same as the concept of 39 * 'timeslice length' - timeslices in CFS are of variable length 40 * and have no persistent notion like in traditional, time-slice 41 * based scheduling concepts. 42 * 43 * (to see the precise effective timeslice length of your workload, 44 * run vmstat and monitor the context-switches (cs) field) 45 */ 46 unsigned int sysctl_sched_latency = 6000000ULL; 47 unsigned int normalized_sysctl_sched_latency = 6000000ULL; 48 49 /* 50 * The initial- and re-scaling of tunables is configurable 51 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) 52 * 53 * Options are: 54 * SCHED_TUNABLESCALING_NONE - unscaled, always *1 55 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) 56 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus 57 */ 58 enum sched_tunable_scaling sysctl_sched_tunable_scaling 59 = SCHED_TUNABLESCALING_LOG; 60 61 /* 62 * Minimal preemption granularity for CPU-bound tasks: 63 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) 64 */ 65 unsigned int sysctl_sched_min_granularity = 750000ULL; 66 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; 67 68 /* 69 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity 70 */ 71 static unsigned int sched_nr_latency = 8; 72 73 /* 74 * After fork, child runs first. If set to 0 (default) then 75 * parent will (try to) run first. 76 */ 77 unsigned int sysctl_sched_child_runs_first __read_mostly; 78 79 /* 80 * SCHED_OTHER wake-up granularity. 81 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) 82 * 83 * This option delays the preemption effects of decoupled workloads 84 * and reduces their over-scheduling. Synchronous workloads will still 85 * have immediate wakeup/sleep latencies. 86 */ 87 unsigned int sysctl_sched_wakeup_granularity = 1000000UL; 88 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; 89 90 const_debug unsigned int sysctl_sched_migration_cost = 500000UL; 91 92 /* 93 * The exponential sliding window over which load is averaged for shares 94 * distribution. 95 * (default: 10msec) 96 */ 97 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; 98 99 #ifdef CONFIG_CFS_BANDWIDTH 100 /* 101 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool 102 * each time a cfs_rq requests quota. 103 * 104 * Note: in the case that the slice exceeds the runtime remaining (either due 105 * to consumption or the quota being specified to be smaller than the slice) 106 * we will always only issue the remaining available time. 107 * 108 * default: 5 msec, units: microseconds 109 */ 110 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; 111 #endif 112 113 /* 114 * Increase the granularity value when there are more CPUs, 115 * because with more CPUs the 'effective latency' as visible 116 * to users decreases. But the relationship is not linear, 117 * so pick a second-best guess by going with the log2 of the 118 * number of CPUs. 119 * 120 * This idea comes from the SD scheduler of Con Kolivas: 121 */ 122 static int get_update_sysctl_factor(void) 123 { 124 unsigned int cpus = min_t(int, num_online_cpus(), 8); 125 unsigned int factor; 126 127 switch (sysctl_sched_tunable_scaling) { 128 case SCHED_TUNABLESCALING_NONE: 129 factor = 1; 130 break; 131 case SCHED_TUNABLESCALING_LINEAR: 132 factor = cpus; 133 break; 134 case SCHED_TUNABLESCALING_LOG: 135 default: 136 factor = 1 + ilog2(cpus); 137 break; 138 } 139 140 return factor; 141 } 142 143 static void update_sysctl(void) 144 { 145 unsigned int factor = get_update_sysctl_factor(); 146 147 #define SET_SYSCTL(name) \ 148 (sysctl_##name = (factor) * normalized_sysctl_##name) 149 SET_SYSCTL(sched_min_granularity); 150 SET_SYSCTL(sched_latency); 151 SET_SYSCTL(sched_wakeup_granularity); 152 #undef SET_SYSCTL 153 } 154 155 void sched_init_granularity(void) 156 { 157 update_sysctl(); 158 } 159 160 #if BITS_PER_LONG == 32 161 # define WMULT_CONST (~0UL) 162 #else 163 # define WMULT_CONST (1UL << 32) 164 #endif 165 166 #define WMULT_SHIFT 32 167 168 /* 169 * Shift right and round: 170 */ 171 #define SRR(x, y) (((x) + (1UL << ((y) - 1))) >> (y)) 172 173 /* 174 * delta *= weight / lw 175 */ 176 static unsigned long 177 calc_delta_mine(unsigned long delta_exec, unsigned long weight, 178 struct load_weight *lw) 179 { 180 u64 tmp; 181 182 /* 183 * weight can be less than 2^SCHED_LOAD_RESOLUTION for task group sched 184 * entities since MIN_SHARES = 2. Treat weight as 1 if less than 185 * 2^SCHED_LOAD_RESOLUTION. 186 */ 187 if (likely(weight > (1UL << SCHED_LOAD_RESOLUTION))) 188 tmp = (u64)delta_exec * scale_load_down(weight); 189 else 190 tmp = (u64)delta_exec; 191 192 if (!lw->inv_weight) { 193 unsigned long w = scale_load_down(lw->weight); 194 195 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) 196 lw->inv_weight = 1; 197 else if (unlikely(!w)) 198 lw->inv_weight = WMULT_CONST; 199 else 200 lw->inv_weight = WMULT_CONST / w; 201 } 202 203 /* 204 * Check whether we'd overflow the 64-bit multiplication: 205 */ 206 if (unlikely(tmp > WMULT_CONST)) 207 tmp = SRR(SRR(tmp, WMULT_SHIFT/2) * lw->inv_weight, 208 WMULT_SHIFT/2); 209 else 210 tmp = SRR(tmp * lw->inv_weight, WMULT_SHIFT); 211 212 return (unsigned long)min(tmp, (u64)(unsigned long)LONG_MAX); 213 } 214 215 216 const struct sched_class fair_sched_class; 217 218 /************************************************************** 219 * CFS operations on generic schedulable entities: 220 */ 221 222 #ifdef CONFIG_FAIR_GROUP_SCHED 223 224 /* cpu runqueue to which this cfs_rq is attached */ 225 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 226 { 227 return cfs_rq->rq; 228 } 229 230 /* An entity is a task if it doesn't "own" a runqueue */ 231 #define entity_is_task(se) (!se->my_q) 232 233 static inline struct task_struct *task_of(struct sched_entity *se) 234 { 235 #ifdef CONFIG_SCHED_DEBUG 236 WARN_ON_ONCE(!entity_is_task(se)); 237 #endif 238 return container_of(se, struct task_struct, se); 239 } 240 241 /* Walk up scheduling entities hierarchy */ 242 #define for_each_sched_entity(se) \ 243 for (; se; se = se->parent) 244 245 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 246 { 247 return p->se.cfs_rq; 248 } 249 250 /* runqueue on which this entity is (to be) queued */ 251 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 252 { 253 return se->cfs_rq; 254 } 255 256 /* runqueue "owned" by this group */ 257 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 258 { 259 return grp->my_q; 260 } 261 262 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 263 { 264 if (!cfs_rq->on_list) { 265 /* 266 * Ensure we either appear before our parent (if already 267 * enqueued) or force our parent to appear after us when it is 268 * enqueued. The fact that we always enqueue bottom-up 269 * reduces this to two cases. 270 */ 271 if (cfs_rq->tg->parent && 272 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) { 273 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, 274 &rq_of(cfs_rq)->leaf_cfs_rq_list); 275 } else { 276 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, 277 &rq_of(cfs_rq)->leaf_cfs_rq_list); 278 } 279 280 cfs_rq->on_list = 1; 281 } 282 } 283 284 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 285 { 286 if (cfs_rq->on_list) { 287 list_del_rcu(&cfs_rq->leaf_cfs_rq_list); 288 cfs_rq->on_list = 0; 289 } 290 } 291 292 /* Iterate thr' all leaf cfs_rq's on a runqueue */ 293 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 294 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) 295 296 /* Do the two (enqueued) entities belong to the same group ? */ 297 static inline int 298 is_same_group(struct sched_entity *se, struct sched_entity *pse) 299 { 300 if (se->cfs_rq == pse->cfs_rq) 301 return 1; 302 303 return 0; 304 } 305 306 static inline struct sched_entity *parent_entity(struct sched_entity *se) 307 { 308 return se->parent; 309 } 310 311 /* return depth at which a sched entity is present in the hierarchy */ 312 static inline int depth_se(struct sched_entity *se) 313 { 314 int depth = 0; 315 316 for_each_sched_entity(se) 317 depth++; 318 319 return depth; 320 } 321 322 static void 323 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 324 { 325 int se_depth, pse_depth; 326 327 /* 328 * preemption test can be made between sibling entities who are in the 329 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of 330 * both tasks until we find their ancestors who are siblings of common 331 * parent. 332 */ 333 334 /* First walk up until both entities are at same depth */ 335 se_depth = depth_se(*se); 336 pse_depth = depth_se(*pse); 337 338 while (se_depth > pse_depth) { 339 se_depth--; 340 *se = parent_entity(*se); 341 } 342 343 while (pse_depth > se_depth) { 344 pse_depth--; 345 *pse = parent_entity(*pse); 346 } 347 348 while (!is_same_group(*se, *pse)) { 349 *se = parent_entity(*se); 350 *pse = parent_entity(*pse); 351 } 352 } 353 354 #else /* !CONFIG_FAIR_GROUP_SCHED */ 355 356 static inline struct task_struct *task_of(struct sched_entity *se) 357 { 358 return container_of(se, struct task_struct, se); 359 } 360 361 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 362 { 363 return container_of(cfs_rq, struct rq, cfs); 364 } 365 366 #define entity_is_task(se) 1 367 368 #define for_each_sched_entity(se) \ 369 for (; se; se = NULL) 370 371 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 372 { 373 return &task_rq(p)->cfs; 374 } 375 376 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 377 { 378 struct task_struct *p = task_of(se); 379 struct rq *rq = task_rq(p); 380 381 return &rq->cfs; 382 } 383 384 /* runqueue "owned" by this group */ 385 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 386 { 387 return NULL; 388 } 389 390 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 391 { 392 } 393 394 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 395 { 396 } 397 398 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 399 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) 400 401 static inline int 402 is_same_group(struct sched_entity *se, struct sched_entity *pse) 403 { 404 return 1; 405 } 406 407 static inline struct sched_entity *parent_entity(struct sched_entity *se) 408 { 409 return NULL; 410 } 411 412 static inline void 413 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 414 { 415 } 416 417 #endif /* CONFIG_FAIR_GROUP_SCHED */ 418 419 static __always_inline 420 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec); 421 422 /************************************************************** 423 * Scheduling class tree data structure manipulation methods: 424 */ 425 426 static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime) 427 { 428 s64 delta = (s64)(vruntime - min_vruntime); 429 if (delta > 0) 430 min_vruntime = vruntime; 431 432 return min_vruntime; 433 } 434 435 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) 436 { 437 s64 delta = (s64)(vruntime - min_vruntime); 438 if (delta < 0) 439 min_vruntime = vruntime; 440 441 return min_vruntime; 442 } 443 444 static inline int entity_before(struct sched_entity *a, 445 struct sched_entity *b) 446 { 447 return (s64)(a->vruntime - b->vruntime) < 0; 448 } 449 450 static void update_min_vruntime(struct cfs_rq *cfs_rq) 451 { 452 u64 vruntime = cfs_rq->min_vruntime; 453 454 if (cfs_rq->curr) 455 vruntime = cfs_rq->curr->vruntime; 456 457 if (cfs_rq->rb_leftmost) { 458 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, 459 struct sched_entity, 460 run_node); 461 462 if (!cfs_rq->curr) 463 vruntime = se->vruntime; 464 else 465 vruntime = min_vruntime(vruntime, se->vruntime); 466 } 467 468 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); 469 #ifndef CONFIG_64BIT 470 smp_wmb(); 471 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 472 #endif 473 } 474 475 /* 476 * Enqueue an entity into the rb-tree: 477 */ 478 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 479 { 480 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; 481 struct rb_node *parent = NULL; 482 struct sched_entity *entry; 483 int leftmost = 1; 484 485 /* 486 * Find the right place in the rbtree: 487 */ 488 while (*link) { 489 parent = *link; 490 entry = rb_entry(parent, struct sched_entity, run_node); 491 /* 492 * We dont care about collisions. Nodes with 493 * the same key stay together. 494 */ 495 if (entity_before(se, entry)) { 496 link = &parent->rb_left; 497 } else { 498 link = &parent->rb_right; 499 leftmost = 0; 500 } 501 } 502 503 /* 504 * Maintain a cache of leftmost tree entries (it is frequently 505 * used): 506 */ 507 if (leftmost) 508 cfs_rq->rb_leftmost = &se->run_node; 509 510 rb_link_node(&se->run_node, parent, link); 511 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); 512 } 513 514 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 515 { 516 if (cfs_rq->rb_leftmost == &se->run_node) { 517 struct rb_node *next_node; 518 519 next_node = rb_next(&se->run_node); 520 cfs_rq->rb_leftmost = next_node; 521 } 522 523 rb_erase(&se->run_node, &cfs_rq->tasks_timeline); 524 } 525 526 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) 527 { 528 struct rb_node *left = cfs_rq->rb_leftmost; 529 530 if (!left) 531 return NULL; 532 533 return rb_entry(left, struct sched_entity, run_node); 534 } 535 536 static struct sched_entity *__pick_next_entity(struct sched_entity *se) 537 { 538 struct rb_node *next = rb_next(&se->run_node); 539 540 if (!next) 541 return NULL; 542 543 return rb_entry(next, struct sched_entity, run_node); 544 } 545 546 #ifdef CONFIG_SCHED_DEBUG 547 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) 548 { 549 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); 550 551 if (!last) 552 return NULL; 553 554 return rb_entry(last, struct sched_entity, run_node); 555 } 556 557 /************************************************************** 558 * Scheduling class statistics methods: 559 */ 560 561 int sched_proc_update_handler(struct ctl_table *table, int write, 562 void __user *buffer, size_t *lenp, 563 loff_t *ppos) 564 { 565 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 566 int factor = get_update_sysctl_factor(); 567 568 if (ret || !write) 569 return ret; 570 571 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, 572 sysctl_sched_min_granularity); 573 574 #define WRT_SYSCTL(name) \ 575 (normalized_sysctl_##name = sysctl_##name / (factor)) 576 WRT_SYSCTL(sched_min_granularity); 577 WRT_SYSCTL(sched_latency); 578 WRT_SYSCTL(sched_wakeup_granularity); 579 #undef WRT_SYSCTL 580 581 return 0; 582 } 583 #endif 584 585 /* 586 * delta /= w 587 */ 588 static inline unsigned long 589 calc_delta_fair(unsigned long delta, struct sched_entity *se) 590 { 591 if (unlikely(se->load.weight != NICE_0_LOAD)) 592 delta = calc_delta_mine(delta, NICE_0_LOAD, &se->load); 593 594 return delta; 595 } 596 597 /* 598 * The idea is to set a period in which each task runs once. 599 * 600 * When there are too many tasks (sched_nr_latency) we have to stretch 601 * this period because otherwise the slices get too small. 602 * 603 * p = (nr <= nl) ? l : l*nr/nl 604 */ 605 static u64 __sched_period(unsigned long nr_running) 606 { 607 u64 period = sysctl_sched_latency; 608 unsigned long nr_latency = sched_nr_latency; 609 610 if (unlikely(nr_running > nr_latency)) { 611 period = sysctl_sched_min_granularity; 612 period *= nr_running; 613 } 614 615 return period; 616 } 617 618 /* 619 * We calculate the wall-time slice from the period by taking a part 620 * proportional to the weight. 621 * 622 * s = p*P[w/rw] 623 */ 624 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 625 { 626 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); 627 628 for_each_sched_entity(se) { 629 struct load_weight *load; 630 struct load_weight lw; 631 632 cfs_rq = cfs_rq_of(se); 633 load = &cfs_rq->load; 634 635 if (unlikely(!se->on_rq)) { 636 lw = cfs_rq->load; 637 638 update_load_add(&lw, se->load.weight); 639 load = &lw; 640 } 641 slice = calc_delta_mine(slice, se->load.weight, load); 642 } 643 return slice; 644 } 645 646 /* 647 * We calculate the vruntime slice of a to be inserted task 648 * 649 * vs = s/w 650 */ 651 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) 652 { 653 return calc_delta_fair(sched_slice(cfs_rq, se), se); 654 } 655 656 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update); 657 static void update_cfs_shares(struct cfs_rq *cfs_rq); 658 659 /* 660 * Update the current task's runtime statistics. Skip current tasks that 661 * are not in our scheduling class. 662 */ 663 static inline void 664 __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr, 665 unsigned long delta_exec) 666 { 667 unsigned long delta_exec_weighted; 668 669 schedstat_set(curr->statistics.exec_max, 670 max((u64)delta_exec, curr->statistics.exec_max)); 671 672 curr->sum_exec_runtime += delta_exec; 673 schedstat_add(cfs_rq, exec_clock, delta_exec); 674 delta_exec_weighted = calc_delta_fair(delta_exec, curr); 675 676 curr->vruntime += delta_exec_weighted; 677 update_min_vruntime(cfs_rq); 678 679 #if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED 680 cfs_rq->load_unacc_exec_time += delta_exec; 681 #endif 682 } 683 684 static void update_curr(struct cfs_rq *cfs_rq) 685 { 686 struct sched_entity *curr = cfs_rq->curr; 687 u64 now = rq_of(cfs_rq)->clock_task; 688 unsigned long delta_exec; 689 690 if (unlikely(!curr)) 691 return; 692 693 /* 694 * Get the amount of time the current task was running 695 * since the last time we changed load (this cannot 696 * overflow on 32 bits): 697 */ 698 delta_exec = (unsigned long)(now - curr->exec_start); 699 if (!delta_exec) 700 return; 701 702 __update_curr(cfs_rq, curr, delta_exec); 703 curr->exec_start = now; 704 705 if (entity_is_task(curr)) { 706 struct task_struct *curtask = task_of(curr); 707 708 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); 709 cpuacct_charge(curtask, delta_exec); 710 account_group_exec_runtime(curtask, delta_exec); 711 } 712 713 account_cfs_rq_runtime(cfs_rq, delta_exec); 714 } 715 716 static inline void 717 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 718 { 719 schedstat_set(se->statistics.wait_start, rq_of(cfs_rq)->clock); 720 } 721 722 /* 723 * Task is being enqueued - update stats: 724 */ 725 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 726 { 727 /* 728 * Are we enqueueing a waiting task? (for current tasks 729 * a dequeue/enqueue event is a NOP) 730 */ 731 if (se != cfs_rq->curr) 732 update_stats_wait_start(cfs_rq, se); 733 } 734 735 static void 736 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) 737 { 738 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max, 739 rq_of(cfs_rq)->clock - se->statistics.wait_start)); 740 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1); 741 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum + 742 rq_of(cfs_rq)->clock - se->statistics.wait_start); 743 #ifdef CONFIG_SCHEDSTATS 744 if (entity_is_task(se)) { 745 trace_sched_stat_wait(task_of(se), 746 rq_of(cfs_rq)->clock - se->statistics.wait_start); 747 } 748 #endif 749 schedstat_set(se->statistics.wait_start, 0); 750 } 751 752 static inline void 753 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 754 { 755 /* 756 * Mark the end of the wait period if dequeueing a 757 * waiting task: 758 */ 759 if (se != cfs_rq->curr) 760 update_stats_wait_end(cfs_rq, se); 761 } 762 763 /* 764 * We are picking a new current task - update its stats: 765 */ 766 static inline void 767 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 768 { 769 /* 770 * We are starting a new run period: 771 */ 772 se->exec_start = rq_of(cfs_rq)->clock_task; 773 } 774 775 /************************************************** 776 * Scheduling class queueing methods: 777 */ 778 779 static void 780 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 781 { 782 update_load_add(&cfs_rq->load, se->load.weight); 783 if (!parent_entity(se)) 784 update_load_add(&rq_of(cfs_rq)->load, se->load.weight); 785 #ifdef CONFIG_SMP 786 if (entity_is_task(se)) 787 list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks); 788 #endif 789 cfs_rq->nr_running++; 790 } 791 792 static void 793 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 794 { 795 update_load_sub(&cfs_rq->load, se->load.weight); 796 if (!parent_entity(se)) 797 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight); 798 if (entity_is_task(se)) 799 list_del_init(&se->group_node); 800 cfs_rq->nr_running--; 801 } 802 803 #ifdef CONFIG_FAIR_GROUP_SCHED 804 /* we need this in update_cfs_load and load-balance functions below */ 805 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); 806 # ifdef CONFIG_SMP 807 static void update_cfs_rq_load_contribution(struct cfs_rq *cfs_rq, 808 int global_update) 809 { 810 struct task_group *tg = cfs_rq->tg; 811 long load_avg; 812 813 load_avg = div64_u64(cfs_rq->load_avg, cfs_rq->load_period+1); 814 load_avg -= cfs_rq->load_contribution; 815 816 if (global_update || abs(load_avg) > cfs_rq->load_contribution / 8) { 817 atomic_add(load_avg, &tg->load_weight); 818 cfs_rq->load_contribution += load_avg; 819 } 820 } 821 822 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) 823 { 824 u64 period = sysctl_sched_shares_window; 825 u64 now, delta; 826 unsigned long load = cfs_rq->load.weight; 827 828 if (cfs_rq->tg == &root_task_group || throttled_hierarchy(cfs_rq)) 829 return; 830 831 now = rq_of(cfs_rq)->clock_task; 832 delta = now - cfs_rq->load_stamp; 833 834 /* truncate load history at 4 idle periods */ 835 if (cfs_rq->load_stamp > cfs_rq->load_last && 836 now - cfs_rq->load_last > 4 * period) { 837 cfs_rq->load_period = 0; 838 cfs_rq->load_avg = 0; 839 delta = period - 1; 840 } 841 842 cfs_rq->load_stamp = now; 843 cfs_rq->load_unacc_exec_time = 0; 844 cfs_rq->load_period += delta; 845 if (load) { 846 cfs_rq->load_last = now; 847 cfs_rq->load_avg += delta * load; 848 } 849 850 /* consider updating load contribution on each fold or truncate */ 851 if (global_update || cfs_rq->load_period > period 852 || !cfs_rq->load_period) 853 update_cfs_rq_load_contribution(cfs_rq, global_update); 854 855 while (cfs_rq->load_period > period) { 856 /* 857 * Inline assembly required to prevent the compiler 858 * optimising this loop into a divmod call. 859 * See __iter_div_u64_rem() for another example of this. 860 */ 861 asm("" : "+rm" (cfs_rq->load_period)); 862 cfs_rq->load_period /= 2; 863 cfs_rq->load_avg /= 2; 864 } 865 866 if (!cfs_rq->curr && !cfs_rq->nr_running && !cfs_rq->load_avg) 867 list_del_leaf_cfs_rq(cfs_rq); 868 } 869 870 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) 871 { 872 long tg_weight; 873 874 /* 875 * Use this CPU's actual weight instead of the last load_contribution 876 * to gain a more accurate current total weight. See 877 * update_cfs_rq_load_contribution(). 878 */ 879 tg_weight = atomic_read(&tg->load_weight); 880 tg_weight -= cfs_rq->load_contribution; 881 tg_weight += cfs_rq->load.weight; 882 883 return tg_weight; 884 } 885 886 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 887 { 888 long tg_weight, load, shares; 889 890 tg_weight = calc_tg_weight(tg, cfs_rq); 891 load = cfs_rq->load.weight; 892 893 shares = (tg->shares * load); 894 if (tg_weight) 895 shares /= tg_weight; 896 897 if (shares < MIN_SHARES) 898 shares = MIN_SHARES; 899 if (shares > tg->shares) 900 shares = tg->shares; 901 902 return shares; 903 } 904 905 static void update_entity_shares_tick(struct cfs_rq *cfs_rq) 906 { 907 if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) { 908 update_cfs_load(cfs_rq, 0); 909 update_cfs_shares(cfs_rq); 910 } 911 } 912 # else /* CONFIG_SMP */ 913 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) 914 { 915 } 916 917 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 918 { 919 return tg->shares; 920 } 921 922 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq) 923 { 924 } 925 # endif /* CONFIG_SMP */ 926 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, 927 unsigned long weight) 928 { 929 if (se->on_rq) { 930 /* commit outstanding execution time */ 931 if (cfs_rq->curr == se) 932 update_curr(cfs_rq); 933 account_entity_dequeue(cfs_rq, se); 934 } 935 936 update_load_set(&se->load, weight); 937 938 if (se->on_rq) 939 account_entity_enqueue(cfs_rq, se); 940 } 941 942 static void update_cfs_shares(struct cfs_rq *cfs_rq) 943 { 944 struct task_group *tg; 945 struct sched_entity *se; 946 long shares; 947 948 tg = cfs_rq->tg; 949 se = tg->se[cpu_of(rq_of(cfs_rq))]; 950 if (!se || throttled_hierarchy(cfs_rq)) 951 return; 952 #ifndef CONFIG_SMP 953 if (likely(se->load.weight == tg->shares)) 954 return; 955 #endif 956 shares = calc_cfs_shares(cfs_rq, tg); 957 958 reweight_entity(cfs_rq_of(se), se, shares); 959 } 960 #else /* CONFIG_FAIR_GROUP_SCHED */ 961 static void update_cfs_load(struct cfs_rq *cfs_rq, int global_update) 962 { 963 } 964 965 static inline void update_cfs_shares(struct cfs_rq *cfs_rq) 966 { 967 } 968 969 static inline void update_entity_shares_tick(struct cfs_rq *cfs_rq) 970 { 971 } 972 #endif /* CONFIG_FAIR_GROUP_SCHED */ 973 974 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) 975 { 976 #ifdef CONFIG_SCHEDSTATS 977 struct task_struct *tsk = NULL; 978 979 if (entity_is_task(se)) 980 tsk = task_of(se); 981 982 if (se->statistics.sleep_start) { 983 u64 delta = rq_of(cfs_rq)->clock - se->statistics.sleep_start; 984 985 if ((s64)delta < 0) 986 delta = 0; 987 988 if (unlikely(delta > se->statistics.sleep_max)) 989 se->statistics.sleep_max = delta; 990 991 se->statistics.sleep_start = 0; 992 se->statistics.sum_sleep_runtime += delta; 993 994 if (tsk) { 995 account_scheduler_latency(tsk, delta >> 10, 1); 996 trace_sched_stat_sleep(tsk, delta); 997 } 998 } 999 if (se->statistics.block_start) { 1000 u64 delta = rq_of(cfs_rq)->clock - se->statistics.block_start; 1001 1002 if ((s64)delta < 0) 1003 delta = 0; 1004 1005 if (unlikely(delta > se->statistics.block_max)) 1006 se->statistics.block_max = delta; 1007 1008 se->statistics.block_start = 0; 1009 se->statistics.sum_sleep_runtime += delta; 1010 1011 if (tsk) { 1012 if (tsk->in_iowait) { 1013 se->statistics.iowait_sum += delta; 1014 se->statistics.iowait_count++; 1015 trace_sched_stat_iowait(tsk, delta); 1016 } 1017 1018 trace_sched_stat_blocked(tsk, delta); 1019 1020 /* 1021 * Blocking time is in units of nanosecs, so shift by 1022 * 20 to get a milliseconds-range estimation of the 1023 * amount of time that the task spent sleeping: 1024 */ 1025 if (unlikely(prof_on == SLEEP_PROFILING)) { 1026 profile_hits(SLEEP_PROFILING, 1027 (void *)get_wchan(tsk), 1028 delta >> 20); 1029 } 1030 account_scheduler_latency(tsk, delta >> 10, 0); 1031 } 1032 } 1033 #endif 1034 } 1035 1036 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) 1037 { 1038 #ifdef CONFIG_SCHED_DEBUG 1039 s64 d = se->vruntime - cfs_rq->min_vruntime; 1040 1041 if (d < 0) 1042 d = -d; 1043 1044 if (d > 3*sysctl_sched_latency) 1045 schedstat_inc(cfs_rq, nr_spread_over); 1046 #endif 1047 } 1048 1049 static void 1050 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 1051 { 1052 u64 vruntime = cfs_rq->min_vruntime; 1053 1054 /* 1055 * The 'current' period is already promised to the current tasks, 1056 * however the extra weight of the new task will slow them down a 1057 * little, place the new task so that it fits in the slot that 1058 * stays open at the end. 1059 */ 1060 if (initial && sched_feat(START_DEBIT)) 1061 vruntime += sched_vslice(cfs_rq, se); 1062 1063 /* sleeps up to a single latency don't count. */ 1064 if (!initial) { 1065 unsigned long thresh = sysctl_sched_latency; 1066 1067 /* 1068 * Halve their sleep time's effect, to allow 1069 * for a gentler effect of sleepers: 1070 */ 1071 if (sched_feat(GENTLE_FAIR_SLEEPERS)) 1072 thresh >>= 1; 1073 1074 vruntime -= thresh; 1075 } 1076 1077 /* ensure we never gain time by being placed backwards. */ 1078 vruntime = max_vruntime(se->vruntime, vruntime); 1079 1080 se->vruntime = vruntime; 1081 } 1082 1083 static void check_enqueue_throttle(struct cfs_rq *cfs_rq); 1084 1085 static void 1086 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 1087 { 1088 /* 1089 * Update the normalized vruntime before updating min_vruntime 1090 * through callig update_curr(). 1091 */ 1092 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) 1093 se->vruntime += cfs_rq->min_vruntime; 1094 1095 /* 1096 * Update run-time statistics of the 'current'. 1097 */ 1098 update_curr(cfs_rq); 1099 update_cfs_load(cfs_rq, 0); 1100 account_entity_enqueue(cfs_rq, se); 1101 update_cfs_shares(cfs_rq); 1102 1103 if (flags & ENQUEUE_WAKEUP) { 1104 place_entity(cfs_rq, se, 0); 1105 enqueue_sleeper(cfs_rq, se); 1106 } 1107 1108 update_stats_enqueue(cfs_rq, se); 1109 check_spread(cfs_rq, se); 1110 if (se != cfs_rq->curr) 1111 __enqueue_entity(cfs_rq, se); 1112 se->on_rq = 1; 1113 1114 if (cfs_rq->nr_running == 1) { 1115 list_add_leaf_cfs_rq(cfs_rq); 1116 check_enqueue_throttle(cfs_rq); 1117 } 1118 } 1119 1120 static void __clear_buddies_last(struct sched_entity *se) 1121 { 1122 for_each_sched_entity(se) { 1123 struct cfs_rq *cfs_rq = cfs_rq_of(se); 1124 if (cfs_rq->last == se) 1125 cfs_rq->last = NULL; 1126 else 1127 break; 1128 } 1129 } 1130 1131 static void __clear_buddies_next(struct sched_entity *se) 1132 { 1133 for_each_sched_entity(se) { 1134 struct cfs_rq *cfs_rq = cfs_rq_of(se); 1135 if (cfs_rq->next == se) 1136 cfs_rq->next = NULL; 1137 else 1138 break; 1139 } 1140 } 1141 1142 static void __clear_buddies_skip(struct sched_entity *se) 1143 { 1144 for_each_sched_entity(se) { 1145 struct cfs_rq *cfs_rq = cfs_rq_of(se); 1146 if (cfs_rq->skip == se) 1147 cfs_rq->skip = NULL; 1148 else 1149 break; 1150 } 1151 } 1152 1153 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) 1154 { 1155 if (cfs_rq->last == se) 1156 __clear_buddies_last(se); 1157 1158 if (cfs_rq->next == se) 1159 __clear_buddies_next(se); 1160 1161 if (cfs_rq->skip == se) 1162 __clear_buddies_skip(se); 1163 } 1164 1165 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); 1166 1167 static void 1168 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 1169 { 1170 /* 1171 * Update run-time statistics of the 'current'. 1172 */ 1173 update_curr(cfs_rq); 1174 1175 update_stats_dequeue(cfs_rq, se); 1176 if (flags & DEQUEUE_SLEEP) { 1177 #ifdef CONFIG_SCHEDSTATS 1178 if (entity_is_task(se)) { 1179 struct task_struct *tsk = task_of(se); 1180 1181 if (tsk->state & TASK_INTERRUPTIBLE) 1182 se->statistics.sleep_start = rq_of(cfs_rq)->clock; 1183 if (tsk->state & TASK_UNINTERRUPTIBLE) 1184 se->statistics.block_start = rq_of(cfs_rq)->clock; 1185 } 1186 #endif 1187 } 1188 1189 clear_buddies(cfs_rq, se); 1190 1191 if (se != cfs_rq->curr) 1192 __dequeue_entity(cfs_rq, se); 1193 se->on_rq = 0; 1194 update_cfs_load(cfs_rq, 0); 1195 account_entity_dequeue(cfs_rq, se); 1196 1197 /* 1198 * Normalize the entity after updating the min_vruntime because the 1199 * update can refer to the ->curr item and we need to reflect this 1200 * movement in our normalized position. 1201 */ 1202 if (!(flags & DEQUEUE_SLEEP)) 1203 se->vruntime -= cfs_rq->min_vruntime; 1204 1205 /* return excess runtime on last dequeue */ 1206 return_cfs_rq_runtime(cfs_rq); 1207 1208 update_min_vruntime(cfs_rq); 1209 update_cfs_shares(cfs_rq); 1210 } 1211 1212 /* 1213 * Preempt the current task with a newly woken task if needed: 1214 */ 1215 static void 1216 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 1217 { 1218 unsigned long ideal_runtime, delta_exec; 1219 struct sched_entity *se; 1220 s64 delta; 1221 1222 ideal_runtime = sched_slice(cfs_rq, curr); 1223 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; 1224 if (delta_exec > ideal_runtime) { 1225 resched_task(rq_of(cfs_rq)->curr); 1226 /* 1227 * The current task ran long enough, ensure it doesn't get 1228 * re-elected due to buddy favours. 1229 */ 1230 clear_buddies(cfs_rq, curr); 1231 return; 1232 } 1233 1234 /* 1235 * Ensure that a task that missed wakeup preemption by a 1236 * narrow margin doesn't have to wait for a full slice. 1237 * This also mitigates buddy induced latencies under load. 1238 */ 1239 if (delta_exec < sysctl_sched_min_granularity) 1240 return; 1241 1242 se = __pick_first_entity(cfs_rq); 1243 delta = curr->vruntime - se->vruntime; 1244 1245 if (delta < 0) 1246 return; 1247 1248 if (delta > ideal_runtime) 1249 resched_task(rq_of(cfs_rq)->curr); 1250 } 1251 1252 static void 1253 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 1254 { 1255 /* 'current' is not kept within the tree. */ 1256 if (se->on_rq) { 1257 /* 1258 * Any task has to be enqueued before it get to execute on 1259 * a CPU. So account for the time it spent waiting on the 1260 * runqueue. 1261 */ 1262 update_stats_wait_end(cfs_rq, se); 1263 __dequeue_entity(cfs_rq, se); 1264 } 1265 1266 update_stats_curr_start(cfs_rq, se); 1267 cfs_rq->curr = se; 1268 #ifdef CONFIG_SCHEDSTATS 1269 /* 1270 * Track our maximum slice length, if the CPU's load is at 1271 * least twice that of our own weight (i.e. dont track it 1272 * when there are only lesser-weight tasks around): 1273 */ 1274 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { 1275 se->statistics.slice_max = max(se->statistics.slice_max, 1276 se->sum_exec_runtime - se->prev_sum_exec_runtime); 1277 } 1278 #endif 1279 se->prev_sum_exec_runtime = se->sum_exec_runtime; 1280 } 1281 1282 static int 1283 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); 1284 1285 /* 1286 * Pick the next process, keeping these things in mind, in this order: 1287 * 1) keep things fair between processes/task groups 1288 * 2) pick the "next" process, since someone really wants that to run 1289 * 3) pick the "last" process, for cache locality 1290 * 4) do not run the "skip" process, if something else is available 1291 */ 1292 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq) 1293 { 1294 struct sched_entity *se = __pick_first_entity(cfs_rq); 1295 struct sched_entity *left = se; 1296 1297 /* 1298 * Avoid running the skip buddy, if running something else can 1299 * be done without getting too unfair. 1300 */ 1301 if (cfs_rq->skip == se) { 1302 struct sched_entity *second = __pick_next_entity(se); 1303 if (second && wakeup_preempt_entity(second, left) < 1) 1304 se = second; 1305 } 1306 1307 /* 1308 * Prefer last buddy, try to return the CPU to a preempted task. 1309 */ 1310 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) 1311 se = cfs_rq->last; 1312 1313 /* 1314 * Someone really wants this to run. If it's not unfair, run it. 1315 */ 1316 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) 1317 se = cfs_rq->next; 1318 1319 clear_buddies(cfs_rq, se); 1320 1321 return se; 1322 } 1323 1324 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq); 1325 1326 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) 1327 { 1328 /* 1329 * If still on the runqueue then deactivate_task() 1330 * was not called and update_curr() has to be done: 1331 */ 1332 if (prev->on_rq) 1333 update_curr(cfs_rq); 1334 1335 /* throttle cfs_rqs exceeding runtime */ 1336 check_cfs_rq_runtime(cfs_rq); 1337 1338 check_spread(cfs_rq, prev); 1339 if (prev->on_rq) { 1340 update_stats_wait_start(cfs_rq, prev); 1341 /* Put 'current' back into the tree. */ 1342 __enqueue_entity(cfs_rq, prev); 1343 } 1344 cfs_rq->curr = NULL; 1345 } 1346 1347 static void 1348 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) 1349 { 1350 /* 1351 * Update run-time statistics of the 'current'. 1352 */ 1353 update_curr(cfs_rq); 1354 1355 /* 1356 * Update share accounting for long-running entities. 1357 */ 1358 update_entity_shares_tick(cfs_rq); 1359 1360 #ifdef CONFIG_SCHED_HRTICK 1361 /* 1362 * queued ticks are scheduled to match the slice, so don't bother 1363 * validating it and just reschedule. 1364 */ 1365 if (queued) { 1366 resched_task(rq_of(cfs_rq)->curr); 1367 return; 1368 } 1369 /* 1370 * don't let the period tick interfere with the hrtick preemption 1371 */ 1372 if (!sched_feat(DOUBLE_TICK) && 1373 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) 1374 return; 1375 #endif 1376 1377 if (cfs_rq->nr_running > 1) 1378 check_preempt_tick(cfs_rq, curr); 1379 } 1380 1381 1382 /************************************************** 1383 * CFS bandwidth control machinery 1384 */ 1385 1386 #ifdef CONFIG_CFS_BANDWIDTH 1387 1388 #ifdef HAVE_JUMP_LABEL 1389 static struct static_key __cfs_bandwidth_used; 1390 1391 static inline bool cfs_bandwidth_used(void) 1392 { 1393 return static_key_false(&__cfs_bandwidth_used); 1394 } 1395 1396 void account_cfs_bandwidth_used(int enabled, int was_enabled) 1397 { 1398 /* only need to count groups transitioning between enabled/!enabled */ 1399 if (enabled && !was_enabled) 1400 static_key_slow_inc(&__cfs_bandwidth_used); 1401 else if (!enabled && was_enabled) 1402 static_key_slow_dec(&__cfs_bandwidth_used); 1403 } 1404 #else /* HAVE_JUMP_LABEL */ 1405 static bool cfs_bandwidth_used(void) 1406 { 1407 return true; 1408 } 1409 1410 void account_cfs_bandwidth_used(int enabled, int was_enabled) {} 1411 #endif /* HAVE_JUMP_LABEL */ 1412 1413 /* 1414 * default period for cfs group bandwidth. 1415 * default: 0.1s, units: nanoseconds 1416 */ 1417 static inline u64 default_cfs_period(void) 1418 { 1419 return 100000000ULL; 1420 } 1421 1422 static inline u64 sched_cfs_bandwidth_slice(void) 1423 { 1424 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; 1425 } 1426 1427 /* 1428 * Replenish runtime according to assigned quota and update expiration time. 1429 * We use sched_clock_cpu directly instead of rq->clock to avoid adding 1430 * additional synchronization around rq->lock. 1431 * 1432 * requires cfs_b->lock 1433 */ 1434 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) 1435 { 1436 u64 now; 1437 1438 if (cfs_b->quota == RUNTIME_INF) 1439 return; 1440 1441 now = sched_clock_cpu(smp_processor_id()); 1442 cfs_b->runtime = cfs_b->quota; 1443 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); 1444 } 1445 1446 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 1447 { 1448 return &tg->cfs_bandwidth; 1449 } 1450 1451 /* returns 0 on failure to allocate runtime */ 1452 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) 1453 { 1454 struct task_group *tg = cfs_rq->tg; 1455 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); 1456 u64 amount = 0, min_amount, expires; 1457 1458 /* note: this is a positive sum as runtime_remaining <= 0 */ 1459 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; 1460 1461 raw_spin_lock(&cfs_b->lock); 1462 if (cfs_b->quota == RUNTIME_INF) 1463 amount = min_amount; 1464 else { 1465 /* 1466 * If the bandwidth pool has become inactive, then at least one 1467 * period must have elapsed since the last consumption. 1468 * Refresh the global state and ensure bandwidth timer becomes 1469 * active. 1470 */ 1471 if (!cfs_b->timer_active) { 1472 __refill_cfs_bandwidth_runtime(cfs_b); 1473 __start_cfs_bandwidth(cfs_b); 1474 } 1475 1476 if (cfs_b->runtime > 0) { 1477 amount = min(cfs_b->runtime, min_amount); 1478 cfs_b->runtime -= amount; 1479 cfs_b->idle = 0; 1480 } 1481 } 1482 expires = cfs_b->runtime_expires; 1483 raw_spin_unlock(&cfs_b->lock); 1484 1485 cfs_rq->runtime_remaining += amount; 1486 /* 1487 * we may have advanced our local expiration to account for allowed 1488 * spread between our sched_clock and the one on which runtime was 1489 * issued. 1490 */ 1491 if ((s64)(expires - cfs_rq->runtime_expires) > 0) 1492 cfs_rq->runtime_expires = expires; 1493 1494 return cfs_rq->runtime_remaining > 0; 1495 } 1496 1497 /* 1498 * Note: This depends on the synchronization provided by sched_clock and the 1499 * fact that rq->clock snapshots this value. 1500 */ 1501 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) 1502 { 1503 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 1504 struct rq *rq = rq_of(cfs_rq); 1505 1506 /* if the deadline is ahead of our clock, nothing to do */ 1507 if (likely((s64)(rq->clock - cfs_rq->runtime_expires) < 0)) 1508 return; 1509 1510 if (cfs_rq->runtime_remaining < 0) 1511 return; 1512 1513 /* 1514 * If the local deadline has passed we have to consider the 1515 * possibility that our sched_clock is 'fast' and the global deadline 1516 * has not truly expired. 1517 * 1518 * Fortunately we can check determine whether this the case by checking 1519 * whether the global deadline has advanced. 1520 */ 1521 1522 if ((s64)(cfs_rq->runtime_expires - cfs_b->runtime_expires) >= 0) { 1523 /* extend local deadline, drift is bounded above by 2 ticks */ 1524 cfs_rq->runtime_expires += TICK_NSEC; 1525 } else { 1526 /* global deadline is ahead, expiration has passed */ 1527 cfs_rq->runtime_remaining = 0; 1528 } 1529 } 1530 1531 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, 1532 unsigned long delta_exec) 1533 { 1534 /* dock delta_exec before expiring quota (as it could span periods) */ 1535 cfs_rq->runtime_remaining -= delta_exec; 1536 expire_cfs_rq_runtime(cfs_rq); 1537 1538 if (likely(cfs_rq->runtime_remaining > 0)) 1539 return; 1540 1541 /* 1542 * if we're unable to extend our runtime we resched so that the active 1543 * hierarchy can be throttled 1544 */ 1545 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) 1546 resched_task(rq_of(cfs_rq)->curr); 1547 } 1548 1549 static __always_inline 1550 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) 1551 { 1552 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) 1553 return; 1554 1555 __account_cfs_rq_runtime(cfs_rq, delta_exec); 1556 } 1557 1558 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 1559 { 1560 return cfs_bandwidth_used() && cfs_rq->throttled; 1561 } 1562 1563 /* check whether cfs_rq, or any parent, is throttled */ 1564 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 1565 { 1566 return cfs_bandwidth_used() && cfs_rq->throttle_count; 1567 } 1568 1569 /* 1570 * Ensure that neither of the group entities corresponding to src_cpu or 1571 * dest_cpu are members of a throttled hierarchy when performing group 1572 * load-balance operations. 1573 */ 1574 static inline int throttled_lb_pair(struct task_group *tg, 1575 int src_cpu, int dest_cpu) 1576 { 1577 struct cfs_rq *src_cfs_rq, *dest_cfs_rq; 1578 1579 src_cfs_rq = tg->cfs_rq[src_cpu]; 1580 dest_cfs_rq = tg->cfs_rq[dest_cpu]; 1581 1582 return throttled_hierarchy(src_cfs_rq) || 1583 throttled_hierarchy(dest_cfs_rq); 1584 } 1585 1586 /* updated child weight may affect parent so we have to do this bottom up */ 1587 static int tg_unthrottle_up(struct task_group *tg, void *data) 1588 { 1589 struct rq *rq = data; 1590 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 1591 1592 cfs_rq->throttle_count--; 1593 #ifdef CONFIG_SMP 1594 if (!cfs_rq->throttle_count) { 1595 u64 delta = rq->clock_task - cfs_rq->load_stamp; 1596 1597 /* leaving throttled state, advance shares averaging windows */ 1598 cfs_rq->load_stamp += delta; 1599 cfs_rq->load_last += delta; 1600 1601 /* update entity weight now that we are on_rq again */ 1602 update_cfs_shares(cfs_rq); 1603 } 1604 #endif 1605 1606 return 0; 1607 } 1608 1609 static int tg_throttle_down(struct task_group *tg, void *data) 1610 { 1611 struct rq *rq = data; 1612 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 1613 1614 /* group is entering throttled state, record last load */ 1615 if (!cfs_rq->throttle_count) 1616 update_cfs_load(cfs_rq, 0); 1617 cfs_rq->throttle_count++; 1618 1619 return 0; 1620 } 1621 1622 static void throttle_cfs_rq(struct cfs_rq *cfs_rq) 1623 { 1624 struct rq *rq = rq_of(cfs_rq); 1625 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 1626 struct sched_entity *se; 1627 long task_delta, dequeue = 1; 1628 1629 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; 1630 1631 /* account load preceding throttle */ 1632 rcu_read_lock(); 1633 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); 1634 rcu_read_unlock(); 1635 1636 task_delta = cfs_rq->h_nr_running; 1637 for_each_sched_entity(se) { 1638 struct cfs_rq *qcfs_rq = cfs_rq_of(se); 1639 /* throttled entity or throttle-on-deactivate */ 1640 if (!se->on_rq) 1641 break; 1642 1643 if (dequeue) 1644 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); 1645 qcfs_rq->h_nr_running -= task_delta; 1646 1647 if (qcfs_rq->load.weight) 1648 dequeue = 0; 1649 } 1650 1651 if (!se) 1652 rq->nr_running -= task_delta; 1653 1654 cfs_rq->throttled = 1; 1655 cfs_rq->throttled_timestamp = rq->clock; 1656 raw_spin_lock(&cfs_b->lock); 1657 list_add_tail_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); 1658 raw_spin_unlock(&cfs_b->lock); 1659 } 1660 1661 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 1662 { 1663 struct rq *rq = rq_of(cfs_rq); 1664 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 1665 struct sched_entity *se; 1666 int enqueue = 1; 1667 long task_delta; 1668 1669 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; 1670 1671 cfs_rq->throttled = 0; 1672 raw_spin_lock(&cfs_b->lock); 1673 cfs_b->throttled_time += rq->clock - cfs_rq->throttled_timestamp; 1674 list_del_rcu(&cfs_rq->throttled_list); 1675 raw_spin_unlock(&cfs_b->lock); 1676 cfs_rq->throttled_timestamp = 0; 1677 1678 update_rq_clock(rq); 1679 /* update hierarchical throttle state */ 1680 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); 1681 1682 if (!cfs_rq->load.weight) 1683 return; 1684 1685 task_delta = cfs_rq->h_nr_running; 1686 for_each_sched_entity(se) { 1687 if (se->on_rq) 1688 enqueue = 0; 1689 1690 cfs_rq = cfs_rq_of(se); 1691 if (enqueue) 1692 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); 1693 cfs_rq->h_nr_running += task_delta; 1694 1695 if (cfs_rq_throttled(cfs_rq)) 1696 break; 1697 } 1698 1699 if (!se) 1700 rq->nr_running += task_delta; 1701 1702 /* determine whether we need to wake up potentially idle cpu */ 1703 if (rq->curr == rq->idle && rq->cfs.nr_running) 1704 resched_task(rq->curr); 1705 } 1706 1707 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, 1708 u64 remaining, u64 expires) 1709 { 1710 struct cfs_rq *cfs_rq; 1711 u64 runtime = remaining; 1712 1713 rcu_read_lock(); 1714 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, 1715 throttled_list) { 1716 struct rq *rq = rq_of(cfs_rq); 1717 1718 raw_spin_lock(&rq->lock); 1719 if (!cfs_rq_throttled(cfs_rq)) 1720 goto next; 1721 1722 runtime = -cfs_rq->runtime_remaining + 1; 1723 if (runtime > remaining) 1724 runtime = remaining; 1725 remaining -= runtime; 1726 1727 cfs_rq->runtime_remaining += runtime; 1728 cfs_rq->runtime_expires = expires; 1729 1730 /* we check whether we're throttled above */ 1731 if (cfs_rq->runtime_remaining > 0) 1732 unthrottle_cfs_rq(cfs_rq); 1733 1734 next: 1735 raw_spin_unlock(&rq->lock); 1736 1737 if (!remaining) 1738 break; 1739 } 1740 rcu_read_unlock(); 1741 1742 return remaining; 1743 } 1744 1745 /* 1746 * Responsible for refilling a task_group's bandwidth and unthrottling its 1747 * cfs_rqs as appropriate. If there has been no activity within the last 1748 * period the timer is deactivated until scheduling resumes; cfs_b->idle is 1749 * used to track this state. 1750 */ 1751 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) 1752 { 1753 u64 runtime, runtime_expires; 1754 int idle = 1, throttled; 1755 1756 raw_spin_lock(&cfs_b->lock); 1757 /* no need to continue the timer with no bandwidth constraint */ 1758 if (cfs_b->quota == RUNTIME_INF) 1759 goto out_unlock; 1760 1761 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 1762 /* idle depends on !throttled (for the case of a large deficit) */ 1763 idle = cfs_b->idle && !throttled; 1764 cfs_b->nr_periods += overrun; 1765 1766 /* if we're going inactive then everything else can be deferred */ 1767 if (idle) 1768 goto out_unlock; 1769 1770 __refill_cfs_bandwidth_runtime(cfs_b); 1771 1772 if (!throttled) { 1773 /* mark as potentially idle for the upcoming period */ 1774 cfs_b->idle = 1; 1775 goto out_unlock; 1776 } 1777 1778 /* account preceding periods in which throttling occurred */ 1779 cfs_b->nr_throttled += overrun; 1780 1781 /* 1782 * There are throttled entities so we must first use the new bandwidth 1783 * to unthrottle them before making it generally available. This 1784 * ensures that all existing debts will be paid before a new cfs_rq is 1785 * allowed to run. 1786 */ 1787 runtime = cfs_b->runtime; 1788 runtime_expires = cfs_b->runtime_expires; 1789 cfs_b->runtime = 0; 1790 1791 /* 1792 * This check is repeated as we are holding onto the new bandwidth 1793 * while we unthrottle. This can potentially race with an unthrottled 1794 * group trying to acquire new bandwidth from the global pool. 1795 */ 1796 while (throttled && runtime > 0) { 1797 raw_spin_unlock(&cfs_b->lock); 1798 /* we can't nest cfs_b->lock while distributing bandwidth */ 1799 runtime = distribute_cfs_runtime(cfs_b, runtime, 1800 runtime_expires); 1801 raw_spin_lock(&cfs_b->lock); 1802 1803 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 1804 } 1805 1806 /* return (any) remaining runtime */ 1807 cfs_b->runtime = runtime; 1808 /* 1809 * While we are ensured activity in the period following an 1810 * unthrottle, this also covers the case in which the new bandwidth is 1811 * insufficient to cover the existing bandwidth deficit. (Forcing the 1812 * timer to remain active while there are any throttled entities.) 1813 */ 1814 cfs_b->idle = 0; 1815 out_unlock: 1816 if (idle) 1817 cfs_b->timer_active = 0; 1818 raw_spin_unlock(&cfs_b->lock); 1819 1820 return idle; 1821 } 1822 1823 /* a cfs_rq won't donate quota below this amount */ 1824 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; 1825 /* minimum remaining period time to redistribute slack quota */ 1826 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; 1827 /* how long we wait to gather additional slack before distributing */ 1828 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; 1829 1830 /* are we near the end of the current quota period? */ 1831 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) 1832 { 1833 struct hrtimer *refresh_timer = &cfs_b->period_timer; 1834 u64 remaining; 1835 1836 /* if the call-back is running a quota refresh is already occurring */ 1837 if (hrtimer_callback_running(refresh_timer)) 1838 return 1; 1839 1840 /* is a quota refresh about to occur? */ 1841 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); 1842 if (remaining < min_expire) 1843 return 1; 1844 1845 return 0; 1846 } 1847 1848 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) 1849 { 1850 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; 1851 1852 /* if there's a quota refresh soon don't bother with slack */ 1853 if (runtime_refresh_within(cfs_b, min_left)) 1854 return; 1855 1856 start_bandwidth_timer(&cfs_b->slack_timer, 1857 ns_to_ktime(cfs_bandwidth_slack_period)); 1858 } 1859 1860 /* we know any runtime found here is valid as update_curr() precedes return */ 1861 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 1862 { 1863 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 1864 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; 1865 1866 if (slack_runtime <= 0) 1867 return; 1868 1869 raw_spin_lock(&cfs_b->lock); 1870 if (cfs_b->quota != RUNTIME_INF && 1871 cfs_rq->runtime_expires == cfs_b->runtime_expires) { 1872 cfs_b->runtime += slack_runtime; 1873 1874 /* we are under rq->lock, defer unthrottling using a timer */ 1875 if (cfs_b->runtime > sched_cfs_bandwidth_slice() && 1876 !list_empty(&cfs_b->throttled_cfs_rq)) 1877 start_cfs_slack_bandwidth(cfs_b); 1878 } 1879 raw_spin_unlock(&cfs_b->lock); 1880 1881 /* even if it's not valid for return we don't want to try again */ 1882 cfs_rq->runtime_remaining -= slack_runtime; 1883 } 1884 1885 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 1886 { 1887 if (!cfs_bandwidth_used()) 1888 return; 1889 1890 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) 1891 return; 1892 1893 __return_cfs_rq_runtime(cfs_rq); 1894 } 1895 1896 /* 1897 * This is done with a timer (instead of inline with bandwidth return) since 1898 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. 1899 */ 1900 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) 1901 { 1902 u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); 1903 u64 expires; 1904 1905 /* confirm we're still not at a refresh boundary */ 1906 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) 1907 return; 1908 1909 raw_spin_lock(&cfs_b->lock); 1910 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) { 1911 runtime = cfs_b->runtime; 1912 cfs_b->runtime = 0; 1913 } 1914 expires = cfs_b->runtime_expires; 1915 raw_spin_unlock(&cfs_b->lock); 1916 1917 if (!runtime) 1918 return; 1919 1920 runtime = distribute_cfs_runtime(cfs_b, runtime, expires); 1921 1922 raw_spin_lock(&cfs_b->lock); 1923 if (expires == cfs_b->runtime_expires) 1924 cfs_b->runtime = runtime; 1925 raw_spin_unlock(&cfs_b->lock); 1926 } 1927 1928 /* 1929 * When a group wakes up we want to make sure that its quota is not already 1930 * expired/exceeded, otherwise it may be allowed to steal additional ticks of 1931 * runtime as update_curr() throttling can not not trigger until it's on-rq. 1932 */ 1933 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) 1934 { 1935 if (!cfs_bandwidth_used()) 1936 return; 1937 1938 /* an active group must be handled by the update_curr()->put() path */ 1939 if (!cfs_rq->runtime_enabled || cfs_rq->curr) 1940 return; 1941 1942 /* ensure the group is not already throttled */ 1943 if (cfs_rq_throttled(cfs_rq)) 1944 return; 1945 1946 /* update runtime allocation */ 1947 account_cfs_rq_runtime(cfs_rq, 0); 1948 if (cfs_rq->runtime_remaining <= 0) 1949 throttle_cfs_rq(cfs_rq); 1950 } 1951 1952 /* conditionally throttle active cfs_rq's from put_prev_entity() */ 1953 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) 1954 { 1955 if (!cfs_bandwidth_used()) 1956 return; 1957 1958 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) 1959 return; 1960 1961 /* 1962 * it's possible for a throttled entity to be forced into a running 1963 * state (e.g. set_curr_task), in this case we're finished. 1964 */ 1965 if (cfs_rq_throttled(cfs_rq)) 1966 return; 1967 1968 throttle_cfs_rq(cfs_rq); 1969 } 1970 1971 static inline u64 default_cfs_period(void); 1972 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun); 1973 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b); 1974 1975 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) 1976 { 1977 struct cfs_bandwidth *cfs_b = 1978 container_of(timer, struct cfs_bandwidth, slack_timer); 1979 do_sched_cfs_slack_timer(cfs_b); 1980 1981 return HRTIMER_NORESTART; 1982 } 1983 1984 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 1985 { 1986 struct cfs_bandwidth *cfs_b = 1987 container_of(timer, struct cfs_bandwidth, period_timer); 1988 ktime_t now; 1989 int overrun; 1990 int idle = 0; 1991 1992 for (;;) { 1993 now = hrtimer_cb_get_time(timer); 1994 overrun = hrtimer_forward(timer, now, cfs_b->period); 1995 1996 if (!overrun) 1997 break; 1998 1999 idle = do_sched_cfs_period_timer(cfs_b, overrun); 2000 } 2001 2002 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 2003 } 2004 2005 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 2006 { 2007 raw_spin_lock_init(&cfs_b->lock); 2008 cfs_b->runtime = 0; 2009 cfs_b->quota = RUNTIME_INF; 2010 cfs_b->period = ns_to_ktime(default_cfs_period()); 2011 2012 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); 2013 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 2014 cfs_b->period_timer.function = sched_cfs_period_timer; 2015 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 2016 cfs_b->slack_timer.function = sched_cfs_slack_timer; 2017 } 2018 2019 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) 2020 { 2021 cfs_rq->runtime_enabled = 0; 2022 INIT_LIST_HEAD(&cfs_rq->throttled_list); 2023 } 2024 2025 /* requires cfs_b->lock, may release to reprogram timer */ 2026 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 2027 { 2028 /* 2029 * The timer may be active because we're trying to set a new bandwidth 2030 * period or because we're racing with the tear-down path 2031 * (timer_active==0 becomes visible before the hrtimer call-back 2032 * terminates). In either case we ensure that it's re-programmed 2033 */ 2034 while (unlikely(hrtimer_active(&cfs_b->period_timer))) { 2035 raw_spin_unlock(&cfs_b->lock); 2036 /* ensure cfs_b->lock is available while we wait */ 2037 hrtimer_cancel(&cfs_b->period_timer); 2038 2039 raw_spin_lock(&cfs_b->lock); 2040 /* if someone else restarted the timer then we're done */ 2041 if (cfs_b->timer_active) 2042 return; 2043 } 2044 2045 cfs_b->timer_active = 1; 2046 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period); 2047 } 2048 2049 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 2050 { 2051 hrtimer_cancel(&cfs_b->period_timer); 2052 hrtimer_cancel(&cfs_b->slack_timer); 2053 } 2054 2055 static void unthrottle_offline_cfs_rqs(struct rq *rq) 2056 { 2057 struct cfs_rq *cfs_rq; 2058 2059 for_each_leaf_cfs_rq(rq, cfs_rq) { 2060 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 2061 2062 if (!cfs_rq->runtime_enabled) 2063 continue; 2064 2065 /* 2066 * clock_task is not advancing so we just need to make sure 2067 * there's some valid quota amount 2068 */ 2069 cfs_rq->runtime_remaining = cfs_b->quota; 2070 if (cfs_rq_throttled(cfs_rq)) 2071 unthrottle_cfs_rq(cfs_rq); 2072 } 2073 } 2074 2075 #else /* CONFIG_CFS_BANDWIDTH */ 2076 static __always_inline 2077 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, unsigned long delta_exec) {} 2078 static void check_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 2079 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} 2080 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 2081 2082 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 2083 { 2084 return 0; 2085 } 2086 2087 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 2088 { 2089 return 0; 2090 } 2091 2092 static inline int throttled_lb_pair(struct task_group *tg, 2093 int src_cpu, int dest_cpu) 2094 { 2095 return 0; 2096 } 2097 2098 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 2099 2100 #ifdef CONFIG_FAIR_GROUP_SCHED 2101 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 2102 #endif 2103 2104 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 2105 { 2106 return NULL; 2107 } 2108 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 2109 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} 2110 2111 #endif /* CONFIG_CFS_BANDWIDTH */ 2112 2113 /************************************************** 2114 * CFS operations on tasks: 2115 */ 2116 2117 #ifdef CONFIG_SCHED_HRTICK 2118 static void hrtick_start_fair(struct rq *rq, struct task_struct *p) 2119 { 2120 struct sched_entity *se = &p->se; 2121 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2122 2123 WARN_ON(task_rq(p) != rq); 2124 2125 if (cfs_rq->nr_running > 1) { 2126 u64 slice = sched_slice(cfs_rq, se); 2127 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; 2128 s64 delta = slice - ran; 2129 2130 if (delta < 0) { 2131 if (rq->curr == p) 2132 resched_task(p); 2133 return; 2134 } 2135 2136 /* 2137 * Don't schedule slices shorter than 10000ns, that just 2138 * doesn't make sense. Rely on vruntime for fairness. 2139 */ 2140 if (rq->curr != p) 2141 delta = max_t(s64, 10000LL, delta); 2142 2143 hrtick_start(rq, delta); 2144 } 2145 } 2146 2147 /* 2148 * called from enqueue/dequeue and updates the hrtick when the 2149 * current task is from our class and nr_running is low enough 2150 * to matter. 2151 */ 2152 static void hrtick_update(struct rq *rq) 2153 { 2154 struct task_struct *curr = rq->curr; 2155 2156 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) 2157 return; 2158 2159 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) 2160 hrtick_start_fair(rq, curr); 2161 } 2162 #else /* !CONFIG_SCHED_HRTICK */ 2163 static inline void 2164 hrtick_start_fair(struct rq *rq, struct task_struct *p) 2165 { 2166 } 2167 2168 static inline void hrtick_update(struct rq *rq) 2169 { 2170 } 2171 #endif 2172 2173 /* 2174 * The enqueue_task method is called before nr_running is 2175 * increased. Here we update the fair scheduling stats and 2176 * then put the task into the rbtree: 2177 */ 2178 static void 2179 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 2180 { 2181 struct cfs_rq *cfs_rq; 2182 struct sched_entity *se = &p->se; 2183 2184 for_each_sched_entity(se) { 2185 if (se->on_rq) 2186 break; 2187 cfs_rq = cfs_rq_of(se); 2188 enqueue_entity(cfs_rq, se, flags); 2189 2190 /* 2191 * end evaluation on encountering a throttled cfs_rq 2192 * 2193 * note: in the case of encountering a throttled cfs_rq we will 2194 * post the final h_nr_running increment below. 2195 */ 2196 if (cfs_rq_throttled(cfs_rq)) 2197 break; 2198 cfs_rq->h_nr_running++; 2199 2200 flags = ENQUEUE_WAKEUP; 2201 } 2202 2203 for_each_sched_entity(se) { 2204 cfs_rq = cfs_rq_of(se); 2205 cfs_rq->h_nr_running++; 2206 2207 if (cfs_rq_throttled(cfs_rq)) 2208 break; 2209 2210 update_cfs_load(cfs_rq, 0); 2211 update_cfs_shares(cfs_rq); 2212 } 2213 2214 if (!se) 2215 inc_nr_running(rq); 2216 hrtick_update(rq); 2217 } 2218 2219 static void set_next_buddy(struct sched_entity *se); 2220 2221 /* 2222 * The dequeue_task method is called before nr_running is 2223 * decreased. We remove the task from the rbtree and 2224 * update the fair scheduling stats: 2225 */ 2226 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 2227 { 2228 struct cfs_rq *cfs_rq; 2229 struct sched_entity *se = &p->se; 2230 int task_sleep = flags & DEQUEUE_SLEEP; 2231 2232 for_each_sched_entity(se) { 2233 cfs_rq = cfs_rq_of(se); 2234 dequeue_entity(cfs_rq, se, flags); 2235 2236 /* 2237 * end evaluation on encountering a throttled cfs_rq 2238 * 2239 * note: in the case of encountering a throttled cfs_rq we will 2240 * post the final h_nr_running decrement below. 2241 */ 2242 if (cfs_rq_throttled(cfs_rq)) 2243 break; 2244 cfs_rq->h_nr_running--; 2245 2246 /* Don't dequeue parent if it has other entities besides us */ 2247 if (cfs_rq->load.weight) { 2248 /* 2249 * Bias pick_next to pick a task from this cfs_rq, as 2250 * p is sleeping when it is within its sched_slice. 2251 */ 2252 if (task_sleep && parent_entity(se)) 2253 set_next_buddy(parent_entity(se)); 2254 2255 /* avoid re-evaluating load for this entity */ 2256 se = parent_entity(se); 2257 break; 2258 } 2259 flags |= DEQUEUE_SLEEP; 2260 } 2261 2262 for_each_sched_entity(se) { 2263 cfs_rq = cfs_rq_of(se); 2264 cfs_rq->h_nr_running--; 2265 2266 if (cfs_rq_throttled(cfs_rq)) 2267 break; 2268 2269 update_cfs_load(cfs_rq, 0); 2270 update_cfs_shares(cfs_rq); 2271 } 2272 2273 if (!se) 2274 dec_nr_running(rq); 2275 hrtick_update(rq); 2276 } 2277 2278 #ifdef CONFIG_SMP 2279 /* Used instead of source_load when we know the type == 0 */ 2280 static unsigned long weighted_cpuload(const int cpu) 2281 { 2282 return cpu_rq(cpu)->load.weight; 2283 } 2284 2285 /* 2286 * Return a low guess at the load of a migration-source cpu weighted 2287 * according to the scheduling class and "nice" value. 2288 * 2289 * We want to under-estimate the load of migration sources, to 2290 * balance conservatively. 2291 */ 2292 static unsigned long source_load(int cpu, int type) 2293 { 2294 struct rq *rq = cpu_rq(cpu); 2295 unsigned long total = weighted_cpuload(cpu); 2296 2297 if (type == 0 || !sched_feat(LB_BIAS)) 2298 return total; 2299 2300 return min(rq->cpu_load[type-1], total); 2301 } 2302 2303 /* 2304 * Return a high guess at the load of a migration-target cpu weighted 2305 * according to the scheduling class and "nice" value. 2306 */ 2307 static unsigned long target_load(int cpu, int type) 2308 { 2309 struct rq *rq = cpu_rq(cpu); 2310 unsigned long total = weighted_cpuload(cpu); 2311 2312 if (type == 0 || !sched_feat(LB_BIAS)) 2313 return total; 2314 2315 return max(rq->cpu_load[type-1], total); 2316 } 2317 2318 static unsigned long power_of(int cpu) 2319 { 2320 return cpu_rq(cpu)->cpu_power; 2321 } 2322 2323 static unsigned long cpu_avg_load_per_task(int cpu) 2324 { 2325 struct rq *rq = cpu_rq(cpu); 2326 unsigned long nr_running = ACCESS_ONCE(rq->nr_running); 2327 2328 if (nr_running) 2329 return rq->load.weight / nr_running; 2330 2331 return 0; 2332 } 2333 2334 2335 static void task_waking_fair(struct task_struct *p) 2336 { 2337 struct sched_entity *se = &p->se; 2338 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2339 u64 min_vruntime; 2340 2341 #ifndef CONFIG_64BIT 2342 u64 min_vruntime_copy; 2343 2344 do { 2345 min_vruntime_copy = cfs_rq->min_vruntime_copy; 2346 smp_rmb(); 2347 min_vruntime = cfs_rq->min_vruntime; 2348 } while (min_vruntime != min_vruntime_copy); 2349 #else 2350 min_vruntime = cfs_rq->min_vruntime; 2351 #endif 2352 2353 se->vruntime -= min_vruntime; 2354 } 2355 2356 #ifdef CONFIG_FAIR_GROUP_SCHED 2357 /* 2358 * effective_load() calculates the load change as seen from the root_task_group 2359 * 2360 * Adding load to a group doesn't make a group heavier, but can cause movement 2361 * of group shares between cpus. Assuming the shares were perfectly aligned one 2362 * can calculate the shift in shares. 2363 * 2364 * Calculate the effective load difference if @wl is added (subtracted) to @tg 2365 * on this @cpu and results in a total addition (subtraction) of @wg to the 2366 * total group weight. 2367 * 2368 * Given a runqueue weight distribution (rw_i) we can compute a shares 2369 * distribution (s_i) using: 2370 * 2371 * s_i = rw_i / \Sum rw_j (1) 2372 * 2373 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and 2374 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting 2375 * shares distribution (s_i): 2376 * 2377 * rw_i = { 2, 4, 1, 0 } 2378 * s_i = { 2/7, 4/7, 1/7, 0 } 2379 * 2380 * As per wake_affine() we're interested in the load of two CPUs (the CPU the 2381 * task used to run on and the CPU the waker is running on), we need to 2382 * compute the effect of waking a task on either CPU and, in case of a sync 2383 * wakeup, compute the effect of the current task going to sleep. 2384 * 2385 * So for a change of @wl to the local @cpu with an overall group weight change 2386 * of @wl we can compute the new shares distribution (s'_i) using: 2387 * 2388 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) 2389 * 2390 * Suppose we're interested in CPUs 0 and 1, and want to compute the load 2391 * differences in waking a task to CPU 0. The additional task changes the 2392 * weight and shares distributions like: 2393 * 2394 * rw'_i = { 3, 4, 1, 0 } 2395 * s'_i = { 3/8, 4/8, 1/8, 0 } 2396 * 2397 * We can then compute the difference in effective weight by using: 2398 * 2399 * dw_i = S * (s'_i - s_i) (3) 2400 * 2401 * Where 'S' is the group weight as seen by its parent. 2402 * 2403 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) 2404 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - 2405 * 4/7) times the weight of the group. 2406 */ 2407 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 2408 { 2409 struct sched_entity *se = tg->se[cpu]; 2410 2411 if (!tg->parent) /* the trivial, non-cgroup case */ 2412 return wl; 2413 2414 for_each_sched_entity(se) { 2415 long w, W; 2416 2417 tg = se->my_q->tg; 2418 2419 /* 2420 * W = @wg + \Sum rw_j 2421 */ 2422 W = wg + calc_tg_weight(tg, se->my_q); 2423 2424 /* 2425 * w = rw_i + @wl 2426 */ 2427 w = se->my_q->load.weight + wl; 2428 2429 /* 2430 * wl = S * s'_i; see (2) 2431 */ 2432 if (W > 0 && w < W) 2433 wl = (w * tg->shares) / W; 2434 else 2435 wl = tg->shares; 2436 2437 /* 2438 * Per the above, wl is the new se->load.weight value; since 2439 * those are clipped to [MIN_SHARES, ...) do so now. See 2440 * calc_cfs_shares(). 2441 */ 2442 if (wl < MIN_SHARES) 2443 wl = MIN_SHARES; 2444 2445 /* 2446 * wl = dw_i = S * (s'_i - s_i); see (3) 2447 */ 2448 wl -= se->load.weight; 2449 2450 /* 2451 * Recursively apply this logic to all parent groups to compute 2452 * the final effective load change on the root group. Since 2453 * only the @tg group gets extra weight, all parent groups can 2454 * only redistribute existing shares. @wl is the shift in shares 2455 * resulting from this level per the above. 2456 */ 2457 wg = 0; 2458 } 2459 2460 return wl; 2461 } 2462 #else 2463 2464 static inline unsigned long effective_load(struct task_group *tg, int cpu, 2465 unsigned long wl, unsigned long wg) 2466 { 2467 return wl; 2468 } 2469 2470 #endif 2471 2472 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 2473 { 2474 s64 this_load, load; 2475 int idx, this_cpu, prev_cpu; 2476 unsigned long tl_per_task; 2477 struct task_group *tg; 2478 unsigned long weight; 2479 int balanced; 2480 2481 idx = sd->wake_idx; 2482 this_cpu = smp_processor_id(); 2483 prev_cpu = task_cpu(p); 2484 load = source_load(prev_cpu, idx); 2485 this_load = target_load(this_cpu, idx); 2486 2487 /* 2488 * If sync wakeup then subtract the (maximum possible) 2489 * effect of the currently running task from the load 2490 * of the current CPU: 2491 */ 2492 if (sync) { 2493 tg = task_group(current); 2494 weight = current->se.load.weight; 2495 2496 this_load += effective_load(tg, this_cpu, -weight, -weight); 2497 load += effective_load(tg, prev_cpu, 0, -weight); 2498 } 2499 2500 tg = task_group(p); 2501 weight = p->se.load.weight; 2502 2503 /* 2504 * In low-load situations, where prev_cpu is idle and this_cpu is idle 2505 * due to the sync cause above having dropped this_load to 0, we'll 2506 * always have an imbalance, but there's really nothing you can do 2507 * about that, so that's good too. 2508 * 2509 * Otherwise check if either cpus are near enough in load to allow this 2510 * task to be woken on this_cpu. 2511 */ 2512 if (this_load > 0) { 2513 s64 this_eff_load, prev_eff_load; 2514 2515 this_eff_load = 100; 2516 this_eff_load *= power_of(prev_cpu); 2517 this_eff_load *= this_load + 2518 effective_load(tg, this_cpu, weight, weight); 2519 2520 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; 2521 prev_eff_load *= power_of(this_cpu); 2522 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); 2523 2524 balanced = this_eff_load <= prev_eff_load; 2525 } else 2526 balanced = true; 2527 2528 /* 2529 * If the currently running task will sleep within 2530 * a reasonable amount of time then attract this newly 2531 * woken task: 2532 */ 2533 if (sync && balanced) 2534 return 1; 2535 2536 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); 2537 tl_per_task = cpu_avg_load_per_task(this_cpu); 2538 2539 if (balanced || 2540 (this_load <= load && 2541 this_load + target_load(prev_cpu, idx) <= tl_per_task)) { 2542 /* 2543 * This domain has SD_WAKE_AFFINE and 2544 * p is cache cold in this domain, and 2545 * there is no bad imbalance. 2546 */ 2547 schedstat_inc(sd, ttwu_move_affine); 2548 schedstat_inc(p, se.statistics.nr_wakeups_affine); 2549 2550 return 1; 2551 } 2552 return 0; 2553 } 2554 2555 /* 2556 * find_idlest_group finds and returns the least busy CPU group within the 2557 * domain. 2558 */ 2559 static struct sched_group * 2560 find_idlest_group(struct sched_domain *sd, struct task_struct *p, 2561 int this_cpu, int load_idx) 2562 { 2563 struct sched_group *idlest = NULL, *group = sd->groups; 2564 unsigned long min_load = ULONG_MAX, this_load = 0; 2565 int imbalance = 100 + (sd->imbalance_pct-100)/2; 2566 2567 do { 2568 unsigned long load, avg_load; 2569 int local_group; 2570 int i; 2571 2572 /* Skip over this group if it has no CPUs allowed */ 2573 if (!cpumask_intersects(sched_group_cpus(group), 2574 tsk_cpus_allowed(p))) 2575 continue; 2576 2577 local_group = cpumask_test_cpu(this_cpu, 2578 sched_group_cpus(group)); 2579 2580 /* Tally up the load of all CPUs in the group */ 2581 avg_load = 0; 2582 2583 for_each_cpu(i, sched_group_cpus(group)) { 2584 /* Bias balancing toward cpus of our domain */ 2585 if (local_group) 2586 load = source_load(i, load_idx); 2587 else 2588 load = target_load(i, load_idx); 2589 2590 avg_load += load; 2591 } 2592 2593 /* Adjust by relative CPU power of the group */ 2594 avg_load = (avg_load * SCHED_POWER_SCALE) / group->sgp->power; 2595 2596 if (local_group) { 2597 this_load = avg_load; 2598 } else if (avg_load < min_load) { 2599 min_load = avg_load; 2600 idlest = group; 2601 } 2602 } while (group = group->next, group != sd->groups); 2603 2604 if (!idlest || 100*this_load < imbalance*min_load) 2605 return NULL; 2606 return idlest; 2607 } 2608 2609 /* 2610 * find_idlest_cpu - find the idlest cpu among the cpus in group. 2611 */ 2612 static int 2613 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 2614 { 2615 unsigned long load, min_load = ULONG_MAX; 2616 int idlest = -1; 2617 int i; 2618 2619 /* Traverse only the allowed CPUs */ 2620 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { 2621 load = weighted_cpuload(i); 2622 2623 if (load < min_load || (load == min_load && i == this_cpu)) { 2624 min_load = load; 2625 idlest = i; 2626 } 2627 } 2628 2629 return idlest; 2630 } 2631 2632 /* 2633 * Try and locate an idle CPU in the sched_domain. 2634 */ 2635 static int select_idle_sibling(struct task_struct *p, int target) 2636 { 2637 int cpu = smp_processor_id(); 2638 int prev_cpu = task_cpu(p); 2639 struct sched_domain *sd; 2640 struct sched_group *sg; 2641 int i; 2642 2643 /* 2644 * If the task is going to be woken-up on this cpu and if it is 2645 * already idle, then it is the right target. 2646 */ 2647 if (target == cpu && idle_cpu(cpu)) 2648 return cpu; 2649 2650 /* 2651 * If the task is going to be woken-up on the cpu where it previously 2652 * ran and if it is currently idle, then it the right target. 2653 */ 2654 if (target == prev_cpu && idle_cpu(prev_cpu)) 2655 return prev_cpu; 2656 2657 /* 2658 * Otherwise, iterate the domains and find an elegible idle cpu. 2659 */ 2660 sd = rcu_dereference(per_cpu(sd_llc, target)); 2661 for_each_lower_domain(sd) { 2662 sg = sd->groups; 2663 do { 2664 if (!cpumask_intersects(sched_group_cpus(sg), 2665 tsk_cpus_allowed(p))) 2666 goto next; 2667 2668 for_each_cpu(i, sched_group_cpus(sg)) { 2669 if (!idle_cpu(i)) 2670 goto next; 2671 } 2672 2673 target = cpumask_first_and(sched_group_cpus(sg), 2674 tsk_cpus_allowed(p)); 2675 goto done; 2676 next: 2677 sg = sg->next; 2678 } while (sg != sd->groups); 2679 } 2680 done: 2681 return target; 2682 } 2683 2684 /* 2685 * sched_balance_self: balance the current task (running on cpu) in domains 2686 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and 2687 * SD_BALANCE_EXEC. 2688 * 2689 * Balance, ie. select the least loaded group. 2690 * 2691 * Returns the target CPU number, or the same CPU if no balancing is needed. 2692 * 2693 * preempt must be disabled. 2694 */ 2695 static int 2696 select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) 2697 { 2698 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; 2699 int cpu = smp_processor_id(); 2700 int prev_cpu = task_cpu(p); 2701 int new_cpu = cpu; 2702 int want_affine = 0; 2703 int sync = wake_flags & WF_SYNC; 2704 2705 if (p->nr_cpus_allowed == 1) 2706 return prev_cpu; 2707 2708 if (sd_flag & SD_BALANCE_WAKE) { 2709 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) 2710 want_affine = 1; 2711 new_cpu = prev_cpu; 2712 } 2713 2714 rcu_read_lock(); 2715 for_each_domain(cpu, tmp) { 2716 if (!(tmp->flags & SD_LOAD_BALANCE)) 2717 continue; 2718 2719 /* 2720 * If both cpu and prev_cpu are part of this domain, 2721 * cpu is a valid SD_WAKE_AFFINE target. 2722 */ 2723 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && 2724 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { 2725 affine_sd = tmp; 2726 break; 2727 } 2728 2729 if (tmp->flags & sd_flag) 2730 sd = tmp; 2731 } 2732 2733 if (affine_sd) { 2734 if (cpu != prev_cpu && wake_affine(affine_sd, p, sync)) 2735 prev_cpu = cpu; 2736 2737 new_cpu = select_idle_sibling(p, prev_cpu); 2738 goto unlock; 2739 } 2740 2741 while (sd) { 2742 int load_idx = sd->forkexec_idx; 2743 struct sched_group *group; 2744 int weight; 2745 2746 if (!(sd->flags & sd_flag)) { 2747 sd = sd->child; 2748 continue; 2749 } 2750 2751 if (sd_flag & SD_BALANCE_WAKE) 2752 load_idx = sd->wake_idx; 2753 2754 group = find_idlest_group(sd, p, cpu, load_idx); 2755 if (!group) { 2756 sd = sd->child; 2757 continue; 2758 } 2759 2760 new_cpu = find_idlest_cpu(group, p, cpu); 2761 if (new_cpu == -1 || new_cpu == cpu) { 2762 /* Now try balancing at a lower domain level of cpu */ 2763 sd = sd->child; 2764 continue; 2765 } 2766 2767 /* Now try balancing at a lower domain level of new_cpu */ 2768 cpu = new_cpu; 2769 weight = sd->span_weight; 2770 sd = NULL; 2771 for_each_domain(cpu, tmp) { 2772 if (weight <= tmp->span_weight) 2773 break; 2774 if (tmp->flags & sd_flag) 2775 sd = tmp; 2776 } 2777 /* while loop will break here if sd == NULL */ 2778 } 2779 unlock: 2780 rcu_read_unlock(); 2781 2782 return new_cpu; 2783 } 2784 #endif /* CONFIG_SMP */ 2785 2786 static unsigned long 2787 wakeup_gran(struct sched_entity *curr, struct sched_entity *se) 2788 { 2789 unsigned long gran = sysctl_sched_wakeup_granularity; 2790 2791 /* 2792 * Since its curr running now, convert the gran from real-time 2793 * to virtual-time in his units. 2794 * 2795 * By using 'se' instead of 'curr' we penalize light tasks, so 2796 * they get preempted easier. That is, if 'se' < 'curr' then 2797 * the resulting gran will be larger, therefore penalizing the 2798 * lighter, if otoh 'se' > 'curr' then the resulting gran will 2799 * be smaller, again penalizing the lighter task. 2800 * 2801 * This is especially important for buddies when the leftmost 2802 * task is higher priority than the buddy. 2803 */ 2804 return calc_delta_fair(gran, se); 2805 } 2806 2807 /* 2808 * Should 'se' preempt 'curr'. 2809 * 2810 * |s1 2811 * |s2 2812 * |s3 2813 * g 2814 * |<--->|c 2815 * 2816 * w(c, s1) = -1 2817 * w(c, s2) = 0 2818 * w(c, s3) = 1 2819 * 2820 */ 2821 static int 2822 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) 2823 { 2824 s64 gran, vdiff = curr->vruntime - se->vruntime; 2825 2826 if (vdiff <= 0) 2827 return -1; 2828 2829 gran = wakeup_gran(curr, se); 2830 if (vdiff > gran) 2831 return 1; 2832 2833 return 0; 2834 } 2835 2836 static void set_last_buddy(struct sched_entity *se) 2837 { 2838 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 2839 return; 2840 2841 for_each_sched_entity(se) 2842 cfs_rq_of(se)->last = se; 2843 } 2844 2845 static void set_next_buddy(struct sched_entity *se) 2846 { 2847 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 2848 return; 2849 2850 for_each_sched_entity(se) 2851 cfs_rq_of(se)->next = se; 2852 } 2853 2854 static void set_skip_buddy(struct sched_entity *se) 2855 { 2856 for_each_sched_entity(se) 2857 cfs_rq_of(se)->skip = se; 2858 } 2859 2860 /* 2861 * Preempt the current task with a newly woken task if needed: 2862 */ 2863 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 2864 { 2865 struct task_struct *curr = rq->curr; 2866 struct sched_entity *se = &curr->se, *pse = &p->se; 2867 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 2868 int scale = cfs_rq->nr_running >= sched_nr_latency; 2869 int next_buddy_marked = 0; 2870 2871 if (unlikely(se == pse)) 2872 return; 2873 2874 /* 2875 * This is possible from callers such as move_task(), in which we 2876 * unconditionally check_prempt_curr() after an enqueue (which may have 2877 * lead to a throttle). This both saves work and prevents false 2878 * next-buddy nomination below. 2879 */ 2880 if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) 2881 return; 2882 2883 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { 2884 set_next_buddy(pse); 2885 next_buddy_marked = 1; 2886 } 2887 2888 /* 2889 * We can come here with TIF_NEED_RESCHED already set from new task 2890 * wake up path. 2891 * 2892 * Note: this also catches the edge-case of curr being in a throttled 2893 * group (e.g. via set_curr_task), since update_curr() (in the 2894 * enqueue of curr) will have resulted in resched being set. This 2895 * prevents us from potentially nominating it as a false LAST_BUDDY 2896 * below. 2897 */ 2898 if (test_tsk_need_resched(curr)) 2899 return; 2900 2901 /* Idle tasks are by definition preempted by non-idle tasks. */ 2902 if (unlikely(curr->policy == SCHED_IDLE) && 2903 likely(p->policy != SCHED_IDLE)) 2904 goto preempt; 2905 2906 /* 2907 * Batch and idle tasks do not preempt non-idle tasks (their preemption 2908 * is driven by the tick): 2909 */ 2910 if (unlikely(p->policy != SCHED_NORMAL)) 2911 return; 2912 2913 find_matching_se(&se, &pse); 2914 update_curr(cfs_rq_of(se)); 2915 BUG_ON(!pse); 2916 if (wakeup_preempt_entity(se, pse) == 1) { 2917 /* 2918 * Bias pick_next to pick the sched entity that is 2919 * triggering this preemption. 2920 */ 2921 if (!next_buddy_marked) 2922 set_next_buddy(pse); 2923 goto preempt; 2924 } 2925 2926 return; 2927 2928 preempt: 2929 resched_task(curr); 2930 /* 2931 * Only set the backward buddy when the current task is still 2932 * on the rq. This can happen when a wakeup gets interleaved 2933 * with schedule on the ->pre_schedule() or idle_balance() 2934 * point, either of which can * drop the rq lock. 2935 * 2936 * Also, during early boot the idle thread is in the fair class, 2937 * for obvious reasons its a bad idea to schedule back to it. 2938 */ 2939 if (unlikely(!se->on_rq || curr == rq->idle)) 2940 return; 2941 2942 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) 2943 set_last_buddy(se); 2944 } 2945 2946 static struct task_struct *pick_next_task_fair(struct rq *rq) 2947 { 2948 struct task_struct *p; 2949 struct cfs_rq *cfs_rq = &rq->cfs; 2950 struct sched_entity *se; 2951 2952 if (!cfs_rq->nr_running) 2953 return NULL; 2954 2955 do { 2956 se = pick_next_entity(cfs_rq); 2957 set_next_entity(cfs_rq, se); 2958 cfs_rq = group_cfs_rq(se); 2959 } while (cfs_rq); 2960 2961 p = task_of(se); 2962 if (hrtick_enabled(rq)) 2963 hrtick_start_fair(rq, p); 2964 2965 return p; 2966 } 2967 2968 /* 2969 * Account for a descheduled task: 2970 */ 2971 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) 2972 { 2973 struct sched_entity *se = &prev->se; 2974 struct cfs_rq *cfs_rq; 2975 2976 for_each_sched_entity(se) { 2977 cfs_rq = cfs_rq_of(se); 2978 put_prev_entity(cfs_rq, se); 2979 } 2980 } 2981 2982 /* 2983 * sched_yield() is very simple 2984 * 2985 * The magic of dealing with the ->skip buddy is in pick_next_entity. 2986 */ 2987 static void yield_task_fair(struct rq *rq) 2988 { 2989 struct task_struct *curr = rq->curr; 2990 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 2991 struct sched_entity *se = &curr->se; 2992 2993 /* 2994 * Are we the only task in the tree? 2995 */ 2996 if (unlikely(rq->nr_running == 1)) 2997 return; 2998 2999 clear_buddies(cfs_rq, se); 3000 3001 if (curr->policy != SCHED_BATCH) { 3002 update_rq_clock(rq); 3003 /* 3004 * Update run-time statistics of the 'current'. 3005 */ 3006 update_curr(cfs_rq); 3007 /* 3008 * Tell update_rq_clock() that we've just updated, 3009 * so we don't do microscopic update in schedule() 3010 * and double the fastpath cost. 3011 */ 3012 rq->skip_clock_update = 1; 3013 } 3014 3015 set_skip_buddy(se); 3016 } 3017 3018 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) 3019 { 3020 struct sched_entity *se = &p->se; 3021 3022 /* throttled hierarchies are not runnable */ 3023 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) 3024 return false; 3025 3026 /* Tell the scheduler that we'd really like pse to run next. */ 3027 set_next_buddy(se); 3028 3029 yield_task_fair(rq); 3030 3031 return true; 3032 } 3033 3034 #ifdef CONFIG_SMP 3035 /************************************************** 3036 * Fair scheduling class load-balancing methods: 3037 */ 3038 3039 static unsigned long __read_mostly max_load_balance_interval = HZ/10; 3040 3041 #define LBF_ALL_PINNED 0x01 3042 #define LBF_NEED_BREAK 0x02 3043 #define LBF_SOME_PINNED 0x04 3044 3045 struct lb_env { 3046 struct sched_domain *sd; 3047 3048 struct rq *src_rq; 3049 int src_cpu; 3050 3051 int dst_cpu; 3052 struct rq *dst_rq; 3053 3054 struct cpumask *dst_grpmask; 3055 int new_dst_cpu; 3056 enum cpu_idle_type idle; 3057 long imbalance; 3058 /* The set of CPUs under consideration for load-balancing */ 3059 struct cpumask *cpus; 3060 3061 unsigned int flags; 3062 3063 unsigned int loop; 3064 unsigned int loop_break; 3065 unsigned int loop_max; 3066 }; 3067 3068 /* 3069 * move_task - move a task from one runqueue to another runqueue. 3070 * Both runqueues must be locked. 3071 */ 3072 static void move_task(struct task_struct *p, struct lb_env *env) 3073 { 3074 deactivate_task(env->src_rq, p, 0); 3075 set_task_cpu(p, env->dst_cpu); 3076 activate_task(env->dst_rq, p, 0); 3077 check_preempt_curr(env->dst_rq, p, 0); 3078 } 3079 3080 /* 3081 * Is this task likely cache-hot: 3082 */ 3083 static int 3084 task_hot(struct task_struct *p, u64 now, struct sched_domain *sd) 3085 { 3086 s64 delta; 3087 3088 if (p->sched_class != &fair_sched_class) 3089 return 0; 3090 3091 if (unlikely(p->policy == SCHED_IDLE)) 3092 return 0; 3093 3094 /* 3095 * Buddy candidates are cache hot: 3096 */ 3097 if (sched_feat(CACHE_HOT_BUDDY) && this_rq()->nr_running && 3098 (&p->se == cfs_rq_of(&p->se)->next || 3099 &p->se == cfs_rq_of(&p->se)->last)) 3100 return 1; 3101 3102 if (sysctl_sched_migration_cost == -1) 3103 return 1; 3104 if (sysctl_sched_migration_cost == 0) 3105 return 0; 3106 3107 delta = now - p->se.exec_start; 3108 3109 return delta < (s64)sysctl_sched_migration_cost; 3110 } 3111 3112 /* 3113 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? 3114 */ 3115 static 3116 int can_migrate_task(struct task_struct *p, struct lb_env *env) 3117 { 3118 int tsk_cache_hot = 0; 3119 /* 3120 * We do not migrate tasks that are: 3121 * 1) running (obviously), or 3122 * 2) cannot be migrated to this CPU due to cpus_allowed, or 3123 * 3) are cache-hot on their current CPU. 3124 */ 3125 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { 3126 int new_dst_cpu; 3127 3128 schedstat_inc(p, se.statistics.nr_failed_migrations_affine); 3129 3130 /* 3131 * Remember if this task can be migrated to any other cpu in 3132 * our sched_group. We may want to revisit it if we couldn't 3133 * meet load balance goals by pulling other tasks on src_cpu. 3134 * 3135 * Also avoid computing new_dst_cpu if we have already computed 3136 * one in current iteration. 3137 */ 3138 if (!env->dst_grpmask || (env->flags & LBF_SOME_PINNED)) 3139 return 0; 3140 3141 new_dst_cpu = cpumask_first_and(env->dst_grpmask, 3142 tsk_cpus_allowed(p)); 3143 if (new_dst_cpu < nr_cpu_ids) { 3144 env->flags |= LBF_SOME_PINNED; 3145 env->new_dst_cpu = new_dst_cpu; 3146 } 3147 return 0; 3148 } 3149 3150 /* Record that we found atleast one task that could run on dst_cpu */ 3151 env->flags &= ~LBF_ALL_PINNED; 3152 3153 if (task_running(env->src_rq, p)) { 3154 schedstat_inc(p, se.statistics.nr_failed_migrations_running); 3155 return 0; 3156 } 3157 3158 /* 3159 * Aggressive migration if: 3160 * 1) task is cache cold, or 3161 * 2) too many balance attempts have failed. 3162 */ 3163 3164 tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd); 3165 if (!tsk_cache_hot || 3166 env->sd->nr_balance_failed > env->sd->cache_nice_tries) { 3167 #ifdef CONFIG_SCHEDSTATS 3168 if (tsk_cache_hot) { 3169 schedstat_inc(env->sd, lb_hot_gained[env->idle]); 3170 schedstat_inc(p, se.statistics.nr_forced_migrations); 3171 } 3172 #endif 3173 return 1; 3174 } 3175 3176 if (tsk_cache_hot) { 3177 schedstat_inc(p, se.statistics.nr_failed_migrations_hot); 3178 return 0; 3179 } 3180 return 1; 3181 } 3182 3183 /* 3184 * move_one_task tries to move exactly one task from busiest to this_rq, as 3185 * part of active balancing operations within "domain". 3186 * Returns 1 if successful and 0 otherwise. 3187 * 3188 * Called with both runqueues locked. 3189 */ 3190 static int move_one_task(struct lb_env *env) 3191 { 3192 struct task_struct *p, *n; 3193 3194 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) { 3195 if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu)) 3196 continue; 3197 3198 if (!can_migrate_task(p, env)) 3199 continue; 3200 3201 move_task(p, env); 3202 /* 3203 * Right now, this is only the second place move_task() 3204 * is called, so we can safely collect move_task() 3205 * stats here rather than inside move_task(). 3206 */ 3207 schedstat_inc(env->sd, lb_gained[env->idle]); 3208 return 1; 3209 } 3210 return 0; 3211 } 3212 3213 static unsigned long task_h_load(struct task_struct *p); 3214 3215 static const unsigned int sched_nr_migrate_break = 32; 3216 3217 /* 3218 * move_tasks tries to move up to imbalance weighted load from busiest to 3219 * this_rq, as part of a balancing operation within domain "sd". 3220 * Returns 1 if successful and 0 otherwise. 3221 * 3222 * Called with both runqueues locked. 3223 */ 3224 static int move_tasks(struct lb_env *env) 3225 { 3226 struct list_head *tasks = &env->src_rq->cfs_tasks; 3227 struct task_struct *p; 3228 unsigned long load; 3229 int pulled = 0; 3230 3231 if (env->imbalance <= 0) 3232 return 0; 3233 3234 while (!list_empty(tasks)) { 3235 p = list_first_entry(tasks, struct task_struct, se.group_node); 3236 3237 env->loop++; 3238 /* We've more or less seen every task there is, call it quits */ 3239 if (env->loop > env->loop_max) 3240 break; 3241 3242 /* take a breather every nr_migrate tasks */ 3243 if (env->loop > env->loop_break) { 3244 env->loop_break += sched_nr_migrate_break; 3245 env->flags |= LBF_NEED_BREAK; 3246 break; 3247 } 3248 3249 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) 3250 goto next; 3251 3252 load = task_h_load(p); 3253 3254 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) 3255 goto next; 3256 3257 if ((load / 2) > env->imbalance) 3258 goto next; 3259 3260 if (!can_migrate_task(p, env)) 3261 goto next; 3262 3263 move_task(p, env); 3264 pulled++; 3265 env->imbalance -= load; 3266 3267 #ifdef CONFIG_PREEMPT 3268 /* 3269 * NEWIDLE balancing is a source of latency, so preemptible 3270 * kernels will stop after the first task is pulled to minimize 3271 * the critical section. 3272 */ 3273 if (env->idle == CPU_NEWLY_IDLE) 3274 break; 3275 #endif 3276 3277 /* 3278 * We only want to steal up to the prescribed amount of 3279 * weighted load. 3280 */ 3281 if (env->imbalance <= 0) 3282 break; 3283 3284 continue; 3285 next: 3286 list_move_tail(&p->se.group_node, tasks); 3287 } 3288 3289 /* 3290 * Right now, this is one of only two places move_task() is called, 3291 * so we can safely collect move_task() stats here rather than 3292 * inside move_task(). 3293 */ 3294 schedstat_add(env->sd, lb_gained[env->idle], pulled); 3295 3296 return pulled; 3297 } 3298 3299 #ifdef CONFIG_FAIR_GROUP_SCHED 3300 /* 3301 * update tg->load_weight by folding this cpu's load_avg 3302 */ 3303 static int update_shares_cpu(struct task_group *tg, int cpu) 3304 { 3305 struct cfs_rq *cfs_rq; 3306 unsigned long flags; 3307 struct rq *rq; 3308 3309 if (!tg->se[cpu]) 3310 return 0; 3311 3312 rq = cpu_rq(cpu); 3313 cfs_rq = tg->cfs_rq[cpu]; 3314 3315 raw_spin_lock_irqsave(&rq->lock, flags); 3316 3317 update_rq_clock(rq); 3318 update_cfs_load(cfs_rq, 1); 3319 3320 /* 3321 * We need to update shares after updating tg->load_weight in 3322 * order to adjust the weight of groups with long running tasks. 3323 */ 3324 update_cfs_shares(cfs_rq); 3325 3326 raw_spin_unlock_irqrestore(&rq->lock, flags); 3327 3328 return 0; 3329 } 3330 3331 static void update_shares(int cpu) 3332 { 3333 struct cfs_rq *cfs_rq; 3334 struct rq *rq = cpu_rq(cpu); 3335 3336 rcu_read_lock(); 3337 /* 3338 * Iterates the task_group tree in a bottom up fashion, see 3339 * list_add_leaf_cfs_rq() for details. 3340 */ 3341 for_each_leaf_cfs_rq(rq, cfs_rq) { 3342 /* throttled entities do not contribute to load */ 3343 if (throttled_hierarchy(cfs_rq)) 3344 continue; 3345 3346 update_shares_cpu(cfs_rq->tg, cpu); 3347 } 3348 rcu_read_unlock(); 3349 } 3350 3351 /* 3352 * Compute the cpu's hierarchical load factor for each task group. 3353 * This needs to be done in a top-down fashion because the load of a child 3354 * group is a fraction of its parents load. 3355 */ 3356 static int tg_load_down(struct task_group *tg, void *data) 3357 { 3358 unsigned long load; 3359 long cpu = (long)data; 3360 3361 if (!tg->parent) { 3362 load = cpu_rq(cpu)->load.weight; 3363 } else { 3364 load = tg->parent->cfs_rq[cpu]->h_load; 3365 load *= tg->se[cpu]->load.weight; 3366 load /= tg->parent->cfs_rq[cpu]->load.weight + 1; 3367 } 3368 3369 tg->cfs_rq[cpu]->h_load = load; 3370 3371 return 0; 3372 } 3373 3374 static void update_h_load(long cpu) 3375 { 3376 struct rq *rq = cpu_rq(cpu); 3377 unsigned long now = jiffies; 3378 3379 if (rq->h_load_throttle == now) 3380 return; 3381 3382 rq->h_load_throttle = now; 3383 3384 rcu_read_lock(); 3385 walk_tg_tree(tg_load_down, tg_nop, (void *)cpu); 3386 rcu_read_unlock(); 3387 } 3388 3389 static unsigned long task_h_load(struct task_struct *p) 3390 { 3391 struct cfs_rq *cfs_rq = task_cfs_rq(p); 3392 unsigned long load; 3393 3394 load = p->se.load.weight; 3395 load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1); 3396 3397 return load; 3398 } 3399 #else 3400 static inline void update_shares(int cpu) 3401 { 3402 } 3403 3404 static inline void update_h_load(long cpu) 3405 { 3406 } 3407 3408 static unsigned long task_h_load(struct task_struct *p) 3409 { 3410 return p->se.load.weight; 3411 } 3412 #endif 3413 3414 /********** Helpers for find_busiest_group ************************/ 3415 /* 3416 * sd_lb_stats - Structure to store the statistics of a sched_domain 3417 * during load balancing. 3418 */ 3419 struct sd_lb_stats { 3420 struct sched_group *busiest; /* Busiest group in this sd */ 3421 struct sched_group *this; /* Local group in this sd */ 3422 unsigned long total_load; /* Total load of all groups in sd */ 3423 unsigned long total_pwr; /* Total power of all groups in sd */ 3424 unsigned long avg_load; /* Average load across all groups in sd */ 3425 3426 /** Statistics of this group */ 3427 unsigned long this_load; 3428 unsigned long this_load_per_task; 3429 unsigned long this_nr_running; 3430 unsigned long this_has_capacity; 3431 unsigned int this_idle_cpus; 3432 3433 /* Statistics of the busiest group */ 3434 unsigned int busiest_idle_cpus; 3435 unsigned long max_load; 3436 unsigned long busiest_load_per_task; 3437 unsigned long busiest_nr_running; 3438 unsigned long busiest_group_capacity; 3439 unsigned long busiest_has_capacity; 3440 unsigned int busiest_group_weight; 3441 3442 int group_imb; /* Is there imbalance in this sd */ 3443 }; 3444 3445 /* 3446 * sg_lb_stats - stats of a sched_group required for load_balancing 3447 */ 3448 struct sg_lb_stats { 3449 unsigned long avg_load; /*Avg load across the CPUs of the group */ 3450 unsigned long group_load; /* Total load over the CPUs of the group */ 3451 unsigned long sum_nr_running; /* Nr tasks running in the group */ 3452 unsigned long sum_weighted_load; /* Weighted load of group's tasks */ 3453 unsigned long group_capacity; 3454 unsigned long idle_cpus; 3455 unsigned long group_weight; 3456 int group_imb; /* Is there an imbalance in the group ? */ 3457 int group_has_capacity; /* Is there extra capacity in the group? */ 3458 }; 3459 3460 /** 3461 * get_sd_load_idx - Obtain the load index for a given sched domain. 3462 * @sd: The sched_domain whose load_idx is to be obtained. 3463 * @idle: The Idle status of the CPU for whose sd load_icx is obtained. 3464 */ 3465 static inline int get_sd_load_idx(struct sched_domain *sd, 3466 enum cpu_idle_type idle) 3467 { 3468 int load_idx; 3469 3470 switch (idle) { 3471 case CPU_NOT_IDLE: 3472 load_idx = sd->busy_idx; 3473 break; 3474 3475 case CPU_NEWLY_IDLE: 3476 load_idx = sd->newidle_idx; 3477 break; 3478 default: 3479 load_idx = sd->idle_idx; 3480 break; 3481 } 3482 3483 return load_idx; 3484 } 3485 3486 unsigned long default_scale_freq_power(struct sched_domain *sd, int cpu) 3487 { 3488 return SCHED_POWER_SCALE; 3489 } 3490 3491 unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu) 3492 { 3493 return default_scale_freq_power(sd, cpu); 3494 } 3495 3496 unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu) 3497 { 3498 unsigned long weight = sd->span_weight; 3499 unsigned long smt_gain = sd->smt_gain; 3500 3501 smt_gain /= weight; 3502 3503 return smt_gain; 3504 } 3505 3506 unsigned long __weak arch_scale_smt_power(struct sched_domain *sd, int cpu) 3507 { 3508 return default_scale_smt_power(sd, cpu); 3509 } 3510 3511 unsigned long scale_rt_power(int cpu) 3512 { 3513 struct rq *rq = cpu_rq(cpu); 3514 u64 total, available, age_stamp, avg; 3515 3516 /* 3517 * Since we're reading these variables without serialization make sure 3518 * we read them once before doing sanity checks on them. 3519 */ 3520 age_stamp = ACCESS_ONCE(rq->age_stamp); 3521 avg = ACCESS_ONCE(rq->rt_avg); 3522 3523 total = sched_avg_period() + (rq->clock - age_stamp); 3524 3525 if (unlikely(total < avg)) { 3526 /* Ensures that power won't end up being negative */ 3527 available = 0; 3528 } else { 3529 available = total - avg; 3530 } 3531 3532 if (unlikely((s64)total < SCHED_POWER_SCALE)) 3533 total = SCHED_POWER_SCALE; 3534 3535 total >>= SCHED_POWER_SHIFT; 3536 3537 return div_u64(available, total); 3538 } 3539 3540 static void update_cpu_power(struct sched_domain *sd, int cpu) 3541 { 3542 unsigned long weight = sd->span_weight; 3543 unsigned long power = SCHED_POWER_SCALE; 3544 struct sched_group *sdg = sd->groups; 3545 3546 if ((sd->flags & SD_SHARE_CPUPOWER) && weight > 1) { 3547 if (sched_feat(ARCH_POWER)) 3548 power *= arch_scale_smt_power(sd, cpu); 3549 else 3550 power *= default_scale_smt_power(sd, cpu); 3551 3552 power >>= SCHED_POWER_SHIFT; 3553 } 3554 3555 sdg->sgp->power_orig = power; 3556 3557 if (sched_feat(ARCH_POWER)) 3558 power *= arch_scale_freq_power(sd, cpu); 3559 else 3560 power *= default_scale_freq_power(sd, cpu); 3561 3562 power >>= SCHED_POWER_SHIFT; 3563 3564 power *= scale_rt_power(cpu); 3565 power >>= SCHED_POWER_SHIFT; 3566 3567 if (!power) 3568 power = 1; 3569 3570 cpu_rq(cpu)->cpu_power = power; 3571 sdg->sgp->power = power; 3572 } 3573 3574 void update_group_power(struct sched_domain *sd, int cpu) 3575 { 3576 struct sched_domain *child = sd->child; 3577 struct sched_group *group, *sdg = sd->groups; 3578 unsigned long power; 3579 unsigned long interval; 3580 3581 interval = msecs_to_jiffies(sd->balance_interval); 3582 interval = clamp(interval, 1UL, max_load_balance_interval); 3583 sdg->sgp->next_update = jiffies + interval; 3584 3585 if (!child) { 3586 update_cpu_power(sd, cpu); 3587 return; 3588 } 3589 3590 power = 0; 3591 3592 if (child->flags & SD_OVERLAP) { 3593 /* 3594 * SD_OVERLAP domains cannot assume that child groups 3595 * span the current group. 3596 */ 3597 3598 for_each_cpu(cpu, sched_group_cpus(sdg)) 3599 power += power_of(cpu); 3600 } else { 3601 /* 3602 * !SD_OVERLAP domains can assume that child groups 3603 * span the current group. 3604 */ 3605 3606 group = child->groups; 3607 do { 3608 power += group->sgp->power; 3609 group = group->next; 3610 } while (group != child->groups); 3611 } 3612 3613 sdg->sgp->power_orig = sdg->sgp->power = power; 3614 } 3615 3616 /* 3617 * Try and fix up capacity for tiny siblings, this is needed when 3618 * things like SD_ASYM_PACKING need f_b_g to select another sibling 3619 * which on its own isn't powerful enough. 3620 * 3621 * See update_sd_pick_busiest() and check_asym_packing(). 3622 */ 3623 static inline int 3624 fix_small_capacity(struct sched_domain *sd, struct sched_group *group) 3625 { 3626 /* 3627 * Only siblings can have significantly less than SCHED_POWER_SCALE 3628 */ 3629 if (!(sd->flags & SD_SHARE_CPUPOWER)) 3630 return 0; 3631 3632 /* 3633 * If ~90% of the cpu_power is still there, we're good. 3634 */ 3635 if (group->sgp->power * 32 > group->sgp->power_orig * 29) 3636 return 1; 3637 3638 return 0; 3639 } 3640 3641 /** 3642 * update_sg_lb_stats - Update sched_group's statistics for load balancing. 3643 * @env: The load balancing environment. 3644 * @group: sched_group whose statistics are to be updated. 3645 * @load_idx: Load index of sched_domain of this_cpu for load calc. 3646 * @local_group: Does group contain this_cpu. 3647 * @balance: Should we balance. 3648 * @sgs: variable to hold the statistics for this group. 3649 */ 3650 static inline void update_sg_lb_stats(struct lb_env *env, 3651 struct sched_group *group, int load_idx, 3652 int local_group, int *balance, struct sg_lb_stats *sgs) 3653 { 3654 unsigned long nr_running, max_nr_running, min_nr_running; 3655 unsigned long load, max_cpu_load, min_cpu_load; 3656 unsigned int balance_cpu = -1, first_idle_cpu = 0; 3657 unsigned long avg_load_per_task = 0; 3658 int i; 3659 3660 if (local_group) 3661 balance_cpu = group_balance_cpu(group); 3662 3663 /* Tally up the load of all CPUs in the group */ 3664 max_cpu_load = 0; 3665 min_cpu_load = ~0UL; 3666 max_nr_running = 0; 3667 min_nr_running = ~0UL; 3668 3669 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 3670 struct rq *rq = cpu_rq(i); 3671 3672 nr_running = rq->nr_running; 3673 3674 /* Bias balancing toward cpus of our domain */ 3675 if (local_group) { 3676 if (idle_cpu(i) && !first_idle_cpu && 3677 cpumask_test_cpu(i, sched_group_mask(group))) { 3678 first_idle_cpu = 1; 3679 balance_cpu = i; 3680 } 3681 3682 load = target_load(i, load_idx); 3683 } else { 3684 load = source_load(i, load_idx); 3685 if (load > max_cpu_load) 3686 max_cpu_load = load; 3687 if (min_cpu_load > load) 3688 min_cpu_load = load; 3689 3690 if (nr_running > max_nr_running) 3691 max_nr_running = nr_running; 3692 if (min_nr_running > nr_running) 3693 min_nr_running = nr_running; 3694 } 3695 3696 sgs->group_load += load; 3697 sgs->sum_nr_running += nr_running; 3698 sgs->sum_weighted_load += weighted_cpuload(i); 3699 if (idle_cpu(i)) 3700 sgs->idle_cpus++; 3701 } 3702 3703 /* 3704 * First idle cpu or the first cpu(busiest) in this sched group 3705 * is eligible for doing load balancing at this and above 3706 * domains. In the newly idle case, we will allow all the cpu's 3707 * to do the newly idle load balance. 3708 */ 3709 if (local_group) { 3710 if (env->idle != CPU_NEWLY_IDLE) { 3711 if (balance_cpu != env->dst_cpu) { 3712 *balance = 0; 3713 return; 3714 } 3715 update_group_power(env->sd, env->dst_cpu); 3716 } else if (time_after_eq(jiffies, group->sgp->next_update)) 3717 update_group_power(env->sd, env->dst_cpu); 3718 } 3719 3720 /* Adjust by relative CPU power of the group */ 3721 sgs->avg_load = (sgs->group_load*SCHED_POWER_SCALE) / group->sgp->power; 3722 3723 /* 3724 * Consider the group unbalanced when the imbalance is larger 3725 * than the average weight of a task. 3726 * 3727 * APZ: with cgroup the avg task weight can vary wildly and 3728 * might not be a suitable number - should we keep a 3729 * normalized nr_running number somewhere that negates 3730 * the hierarchy? 3731 */ 3732 if (sgs->sum_nr_running) 3733 avg_load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; 3734 3735 if ((max_cpu_load - min_cpu_load) >= avg_load_per_task && 3736 (max_nr_running - min_nr_running) > 1) 3737 sgs->group_imb = 1; 3738 3739 sgs->group_capacity = DIV_ROUND_CLOSEST(group->sgp->power, 3740 SCHED_POWER_SCALE); 3741 if (!sgs->group_capacity) 3742 sgs->group_capacity = fix_small_capacity(env->sd, group); 3743 sgs->group_weight = group->group_weight; 3744 3745 if (sgs->group_capacity > sgs->sum_nr_running) 3746 sgs->group_has_capacity = 1; 3747 } 3748 3749 /** 3750 * update_sd_pick_busiest - return 1 on busiest group 3751 * @env: The load balancing environment. 3752 * @sds: sched_domain statistics 3753 * @sg: sched_group candidate to be checked for being the busiest 3754 * @sgs: sched_group statistics 3755 * 3756 * Determine if @sg is a busier group than the previously selected 3757 * busiest group. 3758 */ 3759 static bool update_sd_pick_busiest(struct lb_env *env, 3760 struct sd_lb_stats *sds, 3761 struct sched_group *sg, 3762 struct sg_lb_stats *sgs) 3763 { 3764 if (sgs->avg_load <= sds->max_load) 3765 return false; 3766 3767 if (sgs->sum_nr_running > sgs->group_capacity) 3768 return true; 3769 3770 if (sgs->group_imb) 3771 return true; 3772 3773 /* 3774 * ASYM_PACKING needs to move all the work to the lowest 3775 * numbered CPUs in the group, therefore mark all groups 3776 * higher than ourself as busy. 3777 */ 3778 if ((env->sd->flags & SD_ASYM_PACKING) && sgs->sum_nr_running && 3779 env->dst_cpu < group_first_cpu(sg)) { 3780 if (!sds->busiest) 3781 return true; 3782 3783 if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) 3784 return true; 3785 } 3786 3787 return false; 3788 } 3789 3790 /** 3791 * update_sd_lb_stats - Update sched_domain's statistics for load balancing. 3792 * @env: The load balancing environment. 3793 * @balance: Should we balance. 3794 * @sds: variable to hold the statistics for this sched_domain. 3795 */ 3796 static inline void update_sd_lb_stats(struct lb_env *env, 3797 int *balance, struct sd_lb_stats *sds) 3798 { 3799 struct sched_domain *child = env->sd->child; 3800 struct sched_group *sg = env->sd->groups; 3801 struct sg_lb_stats sgs; 3802 int load_idx, prefer_sibling = 0; 3803 3804 if (child && child->flags & SD_PREFER_SIBLING) 3805 prefer_sibling = 1; 3806 3807 load_idx = get_sd_load_idx(env->sd, env->idle); 3808 3809 do { 3810 int local_group; 3811 3812 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg)); 3813 memset(&sgs, 0, sizeof(sgs)); 3814 update_sg_lb_stats(env, sg, load_idx, local_group, balance, &sgs); 3815 3816 if (local_group && !(*balance)) 3817 return; 3818 3819 sds->total_load += sgs.group_load; 3820 sds->total_pwr += sg->sgp->power; 3821 3822 /* 3823 * In case the child domain prefers tasks go to siblings 3824 * first, lower the sg capacity to one so that we'll try 3825 * and move all the excess tasks away. We lower the capacity 3826 * of a group only if the local group has the capacity to fit 3827 * these excess tasks, i.e. nr_running < group_capacity. The 3828 * extra check prevents the case where you always pull from the 3829 * heaviest group when it is already under-utilized (possible 3830 * with a large weight task outweighs the tasks on the system). 3831 */ 3832 if (prefer_sibling && !local_group && sds->this_has_capacity) 3833 sgs.group_capacity = min(sgs.group_capacity, 1UL); 3834 3835 if (local_group) { 3836 sds->this_load = sgs.avg_load; 3837 sds->this = sg; 3838 sds->this_nr_running = sgs.sum_nr_running; 3839 sds->this_load_per_task = sgs.sum_weighted_load; 3840 sds->this_has_capacity = sgs.group_has_capacity; 3841 sds->this_idle_cpus = sgs.idle_cpus; 3842 } else if (update_sd_pick_busiest(env, sds, sg, &sgs)) { 3843 sds->max_load = sgs.avg_load; 3844 sds->busiest = sg; 3845 sds->busiest_nr_running = sgs.sum_nr_running; 3846 sds->busiest_idle_cpus = sgs.idle_cpus; 3847 sds->busiest_group_capacity = sgs.group_capacity; 3848 sds->busiest_load_per_task = sgs.sum_weighted_load; 3849 sds->busiest_has_capacity = sgs.group_has_capacity; 3850 sds->busiest_group_weight = sgs.group_weight; 3851 sds->group_imb = sgs.group_imb; 3852 } 3853 3854 sg = sg->next; 3855 } while (sg != env->sd->groups); 3856 } 3857 3858 /** 3859 * check_asym_packing - Check to see if the group is packed into the 3860 * sched doman. 3861 * 3862 * This is primarily intended to used at the sibling level. Some 3863 * cores like POWER7 prefer to use lower numbered SMT threads. In the 3864 * case of POWER7, it can move to lower SMT modes only when higher 3865 * threads are idle. When in lower SMT modes, the threads will 3866 * perform better since they share less core resources. Hence when we 3867 * have idle threads, we want them to be the higher ones. 3868 * 3869 * This packing function is run on idle threads. It checks to see if 3870 * the busiest CPU in this domain (core in the P7 case) has a higher 3871 * CPU number than the packing function is being run on. Here we are 3872 * assuming lower CPU number will be equivalent to lower a SMT thread 3873 * number. 3874 * 3875 * Returns 1 when packing is required and a task should be moved to 3876 * this CPU. The amount of the imbalance is returned in *imbalance. 3877 * 3878 * @env: The load balancing environment. 3879 * @sds: Statistics of the sched_domain which is to be packed 3880 */ 3881 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) 3882 { 3883 int busiest_cpu; 3884 3885 if (!(env->sd->flags & SD_ASYM_PACKING)) 3886 return 0; 3887 3888 if (!sds->busiest) 3889 return 0; 3890 3891 busiest_cpu = group_first_cpu(sds->busiest); 3892 if (env->dst_cpu > busiest_cpu) 3893 return 0; 3894 3895 env->imbalance = DIV_ROUND_CLOSEST( 3896 sds->max_load * sds->busiest->sgp->power, SCHED_POWER_SCALE); 3897 3898 return 1; 3899 } 3900 3901 /** 3902 * fix_small_imbalance - Calculate the minor imbalance that exists 3903 * amongst the groups of a sched_domain, during 3904 * load balancing. 3905 * @env: The load balancing environment. 3906 * @sds: Statistics of the sched_domain whose imbalance is to be calculated. 3907 */ 3908 static inline 3909 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 3910 { 3911 unsigned long tmp, pwr_now = 0, pwr_move = 0; 3912 unsigned int imbn = 2; 3913 unsigned long scaled_busy_load_per_task; 3914 3915 if (sds->this_nr_running) { 3916 sds->this_load_per_task /= sds->this_nr_running; 3917 if (sds->busiest_load_per_task > 3918 sds->this_load_per_task) 3919 imbn = 1; 3920 } else { 3921 sds->this_load_per_task = 3922 cpu_avg_load_per_task(env->dst_cpu); 3923 } 3924 3925 scaled_busy_load_per_task = sds->busiest_load_per_task 3926 * SCHED_POWER_SCALE; 3927 scaled_busy_load_per_task /= sds->busiest->sgp->power; 3928 3929 if (sds->max_load - sds->this_load + scaled_busy_load_per_task >= 3930 (scaled_busy_load_per_task * imbn)) { 3931 env->imbalance = sds->busiest_load_per_task; 3932 return; 3933 } 3934 3935 /* 3936 * OK, we don't have enough imbalance to justify moving tasks, 3937 * however we may be able to increase total CPU power used by 3938 * moving them. 3939 */ 3940 3941 pwr_now += sds->busiest->sgp->power * 3942 min(sds->busiest_load_per_task, sds->max_load); 3943 pwr_now += sds->this->sgp->power * 3944 min(sds->this_load_per_task, sds->this_load); 3945 pwr_now /= SCHED_POWER_SCALE; 3946 3947 /* Amount of load we'd subtract */ 3948 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) / 3949 sds->busiest->sgp->power; 3950 if (sds->max_load > tmp) 3951 pwr_move += sds->busiest->sgp->power * 3952 min(sds->busiest_load_per_task, sds->max_load - tmp); 3953 3954 /* Amount of load we'd add */ 3955 if (sds->max_load * sds->busiest->sgp->power < 3956 sds->busiest_load_per_task * SCHED_POWER_SCALE) 3957 tmp = (sds->max_load * sds->busiest->sgp->power) / 3958 sds->this->sgp->power; 3959 else 3960 tmp = (sds->busiest_load_per_task * SCHED_POWER_SCALE) / 3961 sds->this->sgp->power; 3962 pwr_move += sds->this->sgp->power * 3963 min(sds->this_load_per_task, sds->this_load + tmp); 3964 pwr_move /= SCHED_POWER_SCALE; 3965 3966 /* Move if we gain throughput */ 3967 if (pwr_move > pwr_now) 3968 env->imbalance = sds->busiest_load_per_task; 3969 } 3970 3971 /** 3972 * calculate_imbalance - Calculate the amount of imbalance present within the 3973 * groups of a given sched_domain during load balance. 3974 * @env: load balance environment 3975 * @sds: statistics of the sched_domain whose imbalance is to be calculated. 3976 */ 3977 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 3978 { 3979 unsigned long max_pull, load_above_capacity = ~0UL; 3980 3981 sds->busiest_load_per_task /= sds->busiest_nr_running; 3982 if (sds->group_imb) { 3983 sds->busiest_load_per_task = 3984 min(sds->busiest_load_per_task, sds->avg_load); 3985 } 3986 3987 /* 3988 * In the presence of smp nice balancing, certain scenarios can have 3989 * max load less than avg load(as we skip the groups at or below 3990 * its cpu_power, while calculating max_load..) 3991 */ 3992 if (sds->max_load < sds->avg_load) { 3993 env->imbalance = 0; 3994 return fix_small_imbalance(env, sds); 3995 } 3996 3997 if (!sds->group_imb) { 3998 /* 3999 * Don't want to pull so many tasks that a group would go idle. 4000 */ 4001 load_above_capacity = (sds->busiest_nr_running - 4002 sds->busiest_group_capacity); 4003 4004 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_POWER_SCALE); 4005 4006 load_above_capacity /= sds->busiest->sgp->power; 4007 } 4008 4009 /* 4010 * We're trying to get all the cpus to the average_load, so we don't 4011 * want to push ourselves above the average load, nor do we wish to 4012 * reduce the max loaded cpu below the average load. At the same time, 4013 * we also don't want to reduce the group load below the group capacity 4014 * (so that we can implement power-savings policies etc). Thus we look 4015 * for the minimum possible imbalance. 4016 * Be careful of negative numbers as they'll appear as very large values 4017 * with unsigned longs. 4018 */ 4019 max_pull = min(sds->max_load - sds->avg_load, load_above_capacity); 4020 4021 /* How much load to actually move to equalise the imbalance */ 4022 env->imbalance = min(max_pull * sds->busiest->sgp->power, 4023 (sds->avg_load - sds->this_load) * sds->this->sgp->power) 4024 / SCHED_POWER_SCALE; 4025 4026 /* 4027 * if *imbalance is less than the average load per runnable task 4028 * there is no guarantee that any tasks will be moved so we'll have 4029 * a think about bumping its value to force at least one task to be 4030 * moved 4031 */ 4032 if (env->imbalance < sds->busiest_load_per_task) 4033 return fix_small_imbalance(env, sds); 4034 4035 } 4036 4037 /******* find_busiest_group() helpers end here *********************/ 4038 4039 /** 4040 * find_busiest_group - Returns the busiest group within the sched_domain 4041 * if there is an imbalance. If there isn't an imbalance, and 4042 * the user has opted for power-savings, it returns a group whose 4043 * CPUs can be put to idle by rebalancing those tasks elsewhere, if 4044 * such a group exists. 4045 * 4046 * Also calculates the amount of weighted load which should be moved 4047 * to restore balance. 4048 * 4049 * @env: The load balancing environment. 4050 * @balance: Pointer to a variable indicating if this_cpu 4051 * is the appropriate cpu to perform load balancing at this_level. 4052 * 4053 * Returns: - the busiest group if imbalance exists. 4054 * - If no imbalance and user has opted for power-savings balance, 4055 * return the least loaded group whose CPUs can be 4056 * put to idle by rebalancing its tasks onto our group. 4057 */ 4058 static struct sched_group * 4059 find_busiest_group(struct lb_env *env, int *balance) 4060 { 4061 struct sd_lb_stats sds; 4062 4063 memset(&sds, 0, sizeof(sds)); 4064 4065 /* 4066 * Compute the various statistics relavent for load balancing at 4067 * this level. 4068 */ 4069 update_sd_lb_stats(env, balance, &sds); 4070 4071 /* 4072 * this_cpu is not the appropriate cpu to perform load balancing at 4073 * this level. 4074 */ 4075 if (!(*balance)) 4076 goto ret; 4077 4078 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) && 4079 check_asym_packing(env, &sds)) 4080 return sds.busiest; 4081 4082 /* There is no busy sibling group to pull tasks from */ 4083 if (!sds.busiest || sds.busiest_nr_running == 0) 4084 goto out_balanced; 4085 4086 sds.avg_load = (SCHED_POWER_SCALE * sds.total_load) / sds.total_pwr; 4087 4088 /* 4089 * If the busiest group is imbalanced the below checks don't 4090 * work because they assumes all things are equal, which typically 4091 * isn't true due to cpus_allowed constraints and the like. 4092 */ 4093 if (sds.group_imb) 4094 goto force_balance; 4095 4096 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ 4097 if (env->idle == CPU_NEWLY_IDLE && sds.this_has_capacity && 4098 !sds.busiest_has_capacity) 4099 goto force_balance; 4100 4101 /* 4102 * If the local group is more busy than the selected busiest group 4103 * don't try and pull any tasks. 4104 */ 4105 if (sds.this_load >= sds.max_load) 4106 goto out_balanced; 4107 4108 /* 4109 * Don't pull any tasks if this group is already above the domain 4110 * average load. 4111 */ 4112 if (sds.this_load >= sds.avg_load) 4113 goto out_balanced; 4114 4115 if (env->idle == CPU_IDLE) { 4116 /* 4117 * This cpu is idle. If the busiest group load doesn't 4118 * have more tasks than the number of available cpu's and 4119 * there is no imbalance between this and busiest group 4120 * wrt to idle cpu's, it is balanced. 4121 */ 4122 if ((sds.this_idle_cpus <= sds.busiest_idle_cpus + 1) && 4123 sds.busiest_nr_running <= sds.busiest_group_weight) 4124 goto out_balanced; 4125 } else { 4126 /* 4127 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use 4128 * imbalance_pct to be conservative. 4129 */ 4130 if (100 * sds.max_load <= env->sd->imbalance_pct * sds.this_load) 4131 goto out_balanced; 4132 } 4133 4134 force_balance: 4135 /* Looks like there is an imbalance. Compute it */ 4136 calculate_imbalance(env, &sds); 4137 return sds.busiest; 4138 4139 out_balanced: 4140 ret: 4141 env->imbalance = 0; 4142 return NULL; 4143 } 4144 4145 /* 4146 * find_busiest_queue - find the busiest runqueue among the cpus in group. 4147 */ 4148 static struct rq *find_busiest_queue(struct lb_env *env, 4149 struct sched_group *group) 4150 { 4151 struct rq *busiest = NULL, *rq; 4152 unsigned long max_load = 0; 4153 int i; 4154 4155 for_each_cpu(i, sched_group_cpus(group)) { 4156 unsigned long power = power_of(i); 4157 unsigned long capacity = DIV_ROUND_CLOSEST(power, 4158 SCHED_POWER_SCALE); 4159 unsigned long wl; 4160 4161 if (!capacity) 4162 capacity = fix_small_capacity(env->sd, group); 4163 4164 if (!cpumask_test_cpu(i, env->cpus)) 4165 continue; 4166 4167 rq = cpu_rq(i); 4168 wl = weighted_cpuload(i); 4169 4170 /* 4171 * When comparing with imbalance, use weighted_cpuload() 4172 * which is not scaled with the cpu power. 4173 */ 4174 if (capacity && rq->nr_running == 1 && wl > env->imbalance) 4175 continue; 4176 4177 /* 4178 * For the load comparisons with the other cpu's, consider 4179 * the weighted_cpuload() scaled with the cpu power, so that 4180 * the load can be moved away from the cpu that is potentially 4181 * running at a lower capacity. 4182 */ 4183 wl = (wl * SCHED_POWER_SCALE) / power; 4184 4185 if (wl > max_load) { 4186 max_load = wl; 4187 busiest = rq; 4188 } 4189 } 4190 4191 return busiest; 4192 } 4193 4194 /* 4195 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but 4196 * so long as it is large enough. 4197 */ 4198 #define MAX_PINNED_INTERVAL 512 4199 4200 /* Working cpumask for load_balance and load_balance_newidle. */ 4201 DEFINE_PER_CPU(cpumask_var_t, load_balance_tmpmask); 4202 4203 static int need_active_balance(struct lb_env *env) 4204 { 4205 struct sched_domain *sd = env->sd; 4206 4207 if (env->idle == CPU_NEWLY_IDLE) { 4208 4209 /* 4210 * ASYM_PACKING needs to force migrate tasks from busy but 4211 * higher numbered CPUs in order to pack all tasks in the 4212 * lowest numbered CPUs. 4213 */ 4214 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) 4215 return 1; 4216 } 4217 4218 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); 4219 } 4220 4221 static int active_load_balance_cpu_stop(void *data); 4222 4223 /* 4224 * Check this_cpu to ensure it is balanced within domain. Attempt to move 4225 * tasks if there is an imbalance. 4226 */ 4227 static int load_balance(int this_cpu, struct rq *this_rq, 4228 struct sched_domain *sd, enum cpu_idle_type idle, 4229 int *balance) 4230 { 4231 int ld_moved, cur_ld_moved, active_balance = 0; 4232 int lb_iterations, max_lb_iterations; 4233 struct sched_group *group; 4234 struct rq *busiest; 4235 unsigned long flags; 4236 struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask); 4237 4238 struct lb_env env = { 4239 .sd = sd, 4240 .dst_cpu = this_cpu, 4241 .dst_rq = this_rq, 4242 .dst_grpmask = sched_group_cpus(sd->groups), 4243 .idle = idle, 4244 .loop_break = sched_nr_migrate_break, 4245 .cpus = cpus, 4246 }; 4247 4248 cpumask_copy(cpus, cpu_active_mask); 4249 max_lb_iterations = cpumask_weight(env.dst_grpmask); 4250 4251 schedstat_inc(sd, lb_count[idle]); 4252 4253 redo: 4254 group = find_busiest_group(&env, balance); 4255 4256 if (*balance == 0) 4257 goto out_balanced; 4258 4259 if (!group) { 4260 schedstat_inc(sd, lb_nobusyg[idle]); 4261 goto out_balanced; 4262 } 4263 4264 busiest = find_busiest_queue(&env, group); 4265 if (!busiest) { 4266 schedstat_inc(sd, lb_nobusyq[idle]); 4267 goto out_balanced; 4268 } 4269 4270 BUG_ON(busiest == env.dst_rq); 4271 4272 schedstat_add(sd, lb_imbalance[idle], env.imbalance); 4273 4274 ld_moved = 0; 4275 lb_iterations = 1; 4276 if (busiest->nr_running > 1) { 4277 /* 4278 * Attempt to move tasks. If find_busiest_group has found 4279 * an imbalance but busiest->nr_running <= 1, the group is 4280 * still unbalanced. ld_moved simply stays zero, so it is 4281 * correctly treated as an imbalance. 4282 */ 4283 env.flags |= LBF_ALL_PINNED; 4284 env.src_cpu = busiest->cpu; 4285 env.src_rq = busiest; 4286 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); 4287 4288 update_h_load(env.src_cpu); 4289 more_balance: 4290 local_irq_save(flags); 4291 double_rq_lock(env.dst_rq, busiest); 4292 4293 /* 4294 * cur_ld_moved - load moved in current iteration 4295 * ld_moved - cumulative load moved across iterations 4296 */ 4297 cur_ld_moved = move_tasks(&env); 4298 ld_moved += cur_ld_moved; 4299 double_rq_unlock(env.dst_rq, busiest); 4300 local_irq_restore(flags); 4301 4302 if (env.flags & LBF_NEED_BREAK) { 4303 env.flags &= ~LBF_NEED_BREAK; 4304 goto more_balance; 4305 } 4306 4307 /* 4308 * some other cpu did the load balance for us. 4309 */ 4310 if (cur_ld_moved && env.dst_cpu != smp_processor_id()) 4311 resched_cpu(env.dst_cpu); 4312 4313 /* 4314 * Revisit (affine) tasks on src_cpu that couldn't be moved to 4315 * us and move them to an alternate dst_cpu in our sched_group 4316 * where they can run. The upper limit on how many times we 4317 * iterate on same src_cpu is dependent on number of cpus in our 4318 * sched_group. 4319 * 4320 * This changes load balance semantics a bit on who can move 4321 * load to a given_cpu. In addition to the given_cpu itself 4322 * (or a ilb_cpu acting on its behalf where given_cpu is 4323 * nohz-idle), we now have balance_cpu in a position to move 4324 * load to given_cpu. In rare situations, this may cause 4325 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding 4326 * _independently_ and at _same_ time to move some load to 4327 * given_cpu) causing exceess load to be moved to given_cpu. 4328 * This however should not happen so much in practice and 4329 * moreover subsequent load balance cycles should correct the 4330 * excess load moved. 4331 */ 4332 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0 && 4333 lb_iterations++ < max_lb_iterations) { 4334 4335 env.dst_rq = cpu_rq(env.new_dst_cpu); 4336 env.dst_cpu = env.new_dst_cpu; 4337 env.flags &= ~LBF_SOME_PINNED; 4338 env.loop = 0; 4339 env.loop_break = sched_nr_migrate_break; 4340 /* 4341 * Go back to "more_balance" rather than "redo" since we 4342 * need to continue with same src_cpu. 4343 */ 4344 goto more_balance; 4345 } 4346 4347 /* All tasks on this runqueue were pinned by CPU affinity */ 4348 if (unlikely(env.flags & LBF_ALL_PINNED)) { 4349 cpumask_clear_cpu(cpu_of(busiest), cpus); 4350 if (!cpumask_empty(cpus)) { 4351 env.loop = 0; 4352 env.loop_break = sched_nr_migrate_break; 4353 goto redo; 4354 } 4355 goto out_balanced; 4356 } 4357 } 4358 4359 if (!ld_moved) { 4360 schedstat_inc(sd, lb_failed[idle]); 4361 /* 4362 * Increment the failure counter only on periodic balance. 4363 * We do not want newidle balance, which can be very 4364 * frequent, pollute the failure counter causing 4365 * excessive cache_hot migrations and active balances. 4366 */ 4367 if (idle != CPU_NEWLY_IDLE) 4368 sd->nr_balance_failed++; 4369 4370 if (need_active_balance(&env)) { 4371 raw_spin_lock_irqsave(&busiest->lock, flags); 4372 4373 /* don't kick the active_load_balance_cpu_stop, 4374 * if the curr task on busiest cpu can't be 4375 * moved to this_cpu 4376 */ 4377 if (!cpumask_test_cpu(this_cpu, 4378 tsk_cpus_allowed(busiest->curr))) { 4379 raw_spin_unlock_irqrestore(&busiest->lock, 4380 flags); 4381 env.flags |= LBF_ALL_PINNED; 4382 goto out_one_pinned; 4383 } 4384 4385 /* 4386 * ->active_balance synchronizes accesses to 4387 * ->active_balance_work. Once set, it's cleared 4388 * only after active load balance is finished. 4389 */ 4390 if (!busiest->active_balance) { 4391 busiest->active_balance = 1; 4392 busiest->push_cpu = this_cpu; 4393 active_balance = 1; 4394 } 4395 raw_spin_unlock_irqrestore(&busiest->lock, flags); 4396 4397 if (active_balance) { 4398 stop_one_cpu_nowait(cpu_of(busiest), 4399 active_load_balance_cpu_stop, busiest, 4400 &busiest->active_balance_work); 4401 } 4402 4403 /* 4404 * We've kicked active balancing, reset the failure 4405 * counter. 4406 */ 4407 sd->nr_balance_failed = sd->cache_nice_tries+1; 4408 } 4409 } else 4410 sd->nr_balance_failed = 0; 4411 4412 if (likely(!active_balance)) { 4413 /* We were unbalanced, so reset the balancing interval */ 4414 sd->balance_interval = sd->min_interval; 4415 } else { 4416 /* 4417 * If we've begun active balancing, start to back off. This 4418 * case may not be covered by the all_pinned logic if there 4419 * is only 1 task on the busy runqueue (because we don't call 4420 * move_tasks). 4421 */ 4422 if (sd->balance_interval < sd->max_interval) 4423 sd->balance_interval *= 2; 4424 } 4425 4426 goto out; 4427 4428 out_balanced: 4429 schedstat_inc(sd, lb_balanced[idle]); 4430 4431 sd->nr_balance_failed = 0; 4432 4433 out_one_pinned: 4434 /* tune up the balancing interval */ 4435 if (((env.flags & LBF_ALL_PINNED) && 4436 sd->balance_interval < MAX_PINNED_INTERVAL) || 4437 (sd->balance_interval < sd->max_interval)) 4438 sd->balance_interval *= 2; 4439 4440 ld_moved = 0; 4441 out: 4442 return ld_moved; 4443 } 4444 4445 /* 4446 * idle_balance is called by schedule() if this_cpu is about to become 4447 * idle. Attempts to pull tasks from other CPUs. 4448 */ 4449 void idle_balance(int this_cpu, struct rq *this_rq) 4450 { 4451 struct sched_domain *sd; 4452 int pulled_task = 0; 4453 unsigned long next_balance = jiffies + HZ; 4454 4455 this_rq->idle_stamp = this_rq->clock; 4456 4457 if (this_rq->avg_idle < sysctl_sched_migration_cost) 4458 return; 4459 4460 /* 4461 * Drop the rq->lock, but keep IRQ/preempt disabled. 4462 */ 4463 raw_spin_unlock(&this_rq->lock); 4464 4465 update_shares(this_cpu); 4466 rcu_read_lock(); 4467 for_each_domain(this_cpu, sd) { 4468 unsigned long interval; 4469 int balance = 1; 4470 4471 if (!(sd->flags & SD_LOAD_BALANCE)) 4472 continue; 4473 4474 if (sd->flags & SD_BALANCE_NEWIDLE) { 4475 /* If we've pulled tasks over stop searching: */ 4476 pulled_task = load_balance(this_cpu, this_rq, 4477 sd, CPU_NEWLY_IDLE, &balance); 4478 } 4479 4480 interval = msecs_to_jiffies(sd->balance_interval); 4481 if (time_after(next_balance, sd->last_balance + interval)) 4482 next_balance = sd->last_balance + interval; 4483 if (pulled_task) { 4484 this_rq->idle_stamp = 0; 4485 break; 4486 } 4487 } 4488 rcu_read_unlock(); 4489 4490 raw_spin_lock(&this_rq->lock); 4491 4492 if (pulled_task || time_after(jiffies, this_rq->next_balance)) { 4493 /* 4494 * We are going idle. next_balance may be set based on 4495 * a busy processor. So reset next_balance. 4496 */ 4497 this_rq->next_balance = next_balance; 4498 } 4499 } 4500 4501 /* 4502 * active_load_balance_cpu_stop is run by cpu stopper. It pushes 4503 * running tasks off the busiest CPU onto idle CPUs. It requires at 4504 * least 1 task to be running on each physical CPU where possible, and 4505 * avoids physical / logical imbalances. 4506 */ 4507 static int active_load_balance_cpu_stop(void *data) 4508 { 4509 struct rq *busiest_rq = data; 4510 int busiest_cpu = cpu_of(busiest_rq); 4511 int target_cpu = busiest_rq->push_cpu; 4512 struct rq *target_rq = cpu_rq(target_cpu); 4513 struct sched_domain *sd; 4514 4515 raw_spin_lock_irq(&busiest_rq->lock); 4516 4517 /* make sure the requested cpu hasn't gone down in the meantime */ 4518 if (unlikely(busiest_cpu != smp_processor_id() || 4519 !busiest_rq->active_balance)) 4520 goto out_unlock; 4521 4522 /* Is there any task to move? */ 4523 if (busiest_rq->nr_running <= 1) 4524 goto out_unlock; 4525 4526 /* 4527 * This condition is "impossible", if it occurs 4528 * we need to fix it. Originally reported by 4529 * Bjorn Helgaas on a 128-cpu setup. 4530 */ 4531 BUG_ON(busiest_rq == target_rq); 4532 4533 /* move a task from busiest_rq to target_rq */ 4534 double_lock_balance(busiest_rq, target_rq); 4535 4536 /* Search for an sd spanning us and the target CPU. */ 4537 rcu_read_lock(); 4538 for_each_domain(target_cpu, sd) { 4539 if ((sd->flags & SD_LOAD_BALANCE) && 4540 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) 4541 break; 4542 } 4543 4544 if (likely(sd)) { 4545 struct lb_env env = { 4546 .sd = sd, 4547 .dst_cpu = target_cpu, 4548 .dst_rq = target_rq, 4549 .src_cpu = busiest_rq->cpu, 4550 .src_rq = busiest_rq, 4551 .idle = CPU_IDLE, 4552 }; 4553 4554 schedstat_inc(sd, alb_count); 4555 4556 if (move_one_task(&env)) 4557 schedstat_inc(sd, alb_pushed); 4558 else 4559 schedstat_inc(sd, alb_failed); 4560 } 4561 rcu_read_unlock(); 4562 double_unlock_balance(busiest_rq, target_rq); 4563 out_unlock: 4564 busiest_rq->active_balance = 0; 4565 raw_spin_unlock_irq(&busiest_rq->lock); 4566 return 0; 4567 } 4568 4569 #ifdef CONFIG_NO_HZ 4570 /* 4571 * idle load balancing details 4572 * - When one of the busy CPUs notice that there may be an idle rebalancing 4573 * needed, they will kick the idle load balancer, which then does idle 4574 * load balancing for all the idle CPUs. 4575 */ 4576 static struct { 4577 cpumask_var_t idle_cpus_mask; 4578 atomic_t nr_cpus; 4579 unsigned long next_balance; /* in jiffy units */ 4580 } nohz ____cacheline_aligned; 4581 4582 static inline int find_new_ilb(int call_cpu) 4583 { 4584 int ilb = cpumask_first(nohz.idle_cpus_mask); 4585 4586 if (ilb < nr_cpu_ids && idle_cpu(ilb)) 4587 return ilb; 4588 4589 return nr_cpu_ids; 4590 } 4591 4592 /* 4593 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the 4594 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle 4595 * CPU (if there is one). 4596 */ 4597 static void nohz_balancer_kick(int cpu) 4598 { 4599 int ilb_cpu; 4600 4601 nohz.next_balance++; 4602 4603 ilb_cpu = find_new_ilb(cpu); 4604 4605 if (ilb_cpu >= nr_cpu_ids) 4606 return; 4607 4608 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu))) 4609 return; 4610 /* 4611 * Use smp_send_reschedule() instead of resched_cpu(). 4612 * This way we generate a sched IPI on the target cpu which 4613 * is idle. And the softirq performing nohz idle load balance 4614 * will be run before returning from the IPI. 4615 */ 4616 smp_send_reschedule(ilb_cpu); 4617 return; 4618 } 4619 4620 static inline void nohz_balance_exit_idle(int cpu) 4621 { 4622 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { 4623 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); 4624 atomic_dec(&nohz.nr_cpus); 4625 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 4626 } 4627 } 4628 4629 static inline void set_cpu_sd_state_busy(void) 4630 { 4631 struct sched_domain *sd; 4632 int cpu = smp_processor_id(); 4633 4634 if (!test_bit(NOHZ_IDLE, nohz_flags(cpu))) 4635 return; 4636 clear_bit(NOHZ_IDLE, nohz_flags(cpu)); 4637 4638 rcu_read_lock(); 4639 for_each_domain(cpu, sd) 4640 atomic_inc(&sd->groups->sgp->nr_busy_cpus); 4641 rcu_read_unlock(); 4642 } 4643 4644 void set_cpu_sd_state_idle(void) 4645 { 4646 struct sched_domain *sd; 4647 int cpu = smp_processor_id(); 4648 4649 if (test_bit(NOHZ_IDLE, nohz_flags(cpu))) 4650 return; 4651 set_bit(NOHZ_IDLE, nohz_flags(cpu)); 4652 4653 rcu_read_lock(); 4654 for_each_domain(cpu, sd) 4655 atomic_dec(&sd->groups->sgp->nr_busy_cpus); 4656 rcu_read_unlock(); 4657 } 4658 4659 /* 4660 * This routine will record that the cpu is going idle with tick stopped. 4661 * This info will be used in performing idle load balancing in the future. 4662 */ 4663 void nohz_balance_enter_idle(int cpu) 4664 { 4665 /* 4666 * If this cpu is going down, then nothing needs to be done. 4667 */ 4668 if (!cpu_active(cpu)) 4669 return; 4670 4671 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) 4672 return; 4673 4674 cpumask_set_cpu(cpu, nohz.idle_cpus_mask); 4675 atomic_inc(&nohz.nr_cpus); 4676 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 4677 } 4678 4679 static int __cpuinit sched_ilb_notifier(struct notifier_block *nfb, 4680 unsigned long action, void *hcpu) 4681 { 4682 switch (action & ~CPU_TASKS_FROZEN) { 4683 case CPU_DYING: 4684 nohz_balance_exit_idle(smp_processor_id()); 4685 return NOTIFY_OK; 4686 default: 4687 return NOTIFY_DONE; 4688 } 4689 } 4690 #endif 4691 4692 static DEFINE_SPINLOCK(balancing); 4693 4694 /* 4695 * Scale the max load_balance interval with the number of CPUs in the system. 4696 * This trades load-balance latency on larger machines for less cross talk. 4697 */ 4698 void update_max_interval(void) 4699 { 4700 max_load_balance_interval = HZ*num_online_cpus()/10; 4701 } 4702 4703 /* 4704 * It checks each scheduling domain to see if it is due to be balanced, 4705 * and initiates a balancing operation if so. 4706 * 4707 * Balancing parameters are set up in arch_init_sched_domains. 4708 */ 4709 static void rebalance_domains(int cpu, enum cpu_idle_type idle) 4710 { 4711 int balance = 1; 4712 struct rq *rq = cpu_rq(cpu); 4713 unsigned long interval; 4714 struct sched_domain *sd; 4715 /* Earliest time when we have to do rebalance again */ 4716 unsigned long next_balance = jiffies + 60*HZ; 4717 int update_next_balance = 0; 4718 int need_serialize; 4719 4720 update_shares(cpu); 4721 4722 rcu_read_lock(); 4723 for_each_domain(cpu, sd) { 4724 if (!(sd->flags & SD_LOAD_BALANCE)) 4725 continue; 4726 4727 interval = sd->balance_interval; 4728 if (idle != CPU_IDLE) 4729 interval *= sd->busy_factor; 4730 4731 /* scale ms to jiffies */ 4732 interval = msecs_to_jiffies(interval); 4733 interval = clamp(interval, 1UL, max_load_balance_interval); 4734 4735 need_serialize = sd->flags & SD_SERIALIZE; 4736 4737 if (need_serialize) { 4738 if (!spin_trylock(&balancing)) 4739 goto out; 4740 } 4741 4742 if (time_after_eq(jiffies, sd->last_balance + interval)) { 4743 if (load_balance(cpu, rq, sd, idle, &balance)) { 4744 /* 4745 * We've pulled tasks over so either we're no 4746 * longer idle. 4747 */ 4748 idle = CPU_NOT_IDLE; 4749 } 4750 sd->last_balance = jiffies; 4751 } 4752 if (need_serialize) 4753 spin_unlock(&balancing); 4754 out: 4755 if (time_after(next_balance, sd->last_balance + interval)) { 4756 next_balance = sd->last_balance + interval; 4757 update_next_balance = 1; 4758 } 4759 4760 /* 4761 * Stop the load balance at this level. There is another 4762 * CPU in our sched group which is doing load balancing more 4763 * actively. 4764 */ 4765 if (!balance) 4766 break; 4767 } 4768 rcu_read_unlock(); 4769 4770 /* 4771 * next_balance will be updated only when there is a need. 4772 * When the cpu is attached to null domain for ex, it will not be 4773 * updated. 4774 */ 4775 if (likely(update_next_balance)) 4776 rq->next_balance = next_balance; 4777 } 4778 4779 #ifdef CONFIG_NO_HZ 4780 /* 4781 * In CONFIG_NO_HZ case, the idle balance kickee will do the 4782 * rebalancing for all the cpus for whom scheduler ticks are stopped. 4783 */ 4784 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) 4785 { 4786 struct rq *this_rq = cpu_rq(this_cpu); 4787 struct rq *rq; 4788 int balance_cpu; 4789 4790 if (idle != CPU_IDLE || 4791 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) 4792 goto end; 4793 4794 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { 4795 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) 4796 continue; 4797 4798 /* 4799 * If this cpu gets work to do, stop the load balancing 4800 * work being done for other cpus. Next load 4801 * balancing owner will pick it up. 4802 */ 4803 if (need_resched()) 4804 break; 4805 4806 rq = cpu_rq(balance_cpu); 4807 4808 raw_spin_lock_irq(&rq->lock); 4809 update_rq_clock(rq); 4810 update_idle_cpu_load(rq); 4811 raw_spin_unlock_irq(&rq->lock); 4812 4813 rebalance_domains(balance_cpu, CPU_IDLE); 4814 4815 if (time_after(this_rq->next_balance, rq->next_balance)) 4816 this_rq->next_balance = rq->next_balance; 4817 } 4818 nohz.next_balance = this_rq->next_balance; 4819 end: 4820 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)); 4821 } 4822 4823 /* 4824 * Current heuristic for kicking the idle load balancer in the presence 4825 * of an idle cpu is the system. 4826 * - This rq has more than one task. 4827 * - At any scheduler domain level, this cpu's scheduler group has multiple 4828 * busy cpu's exceeding the group's power. 4829 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler 4830 * domain span are idle. 4831 */ 4832 static inline int nohz_kick_needed(struct rq *rq, int cpu) 4833 { 4834 unsigned long now = jiffies; 4835 struct sched_domain *sd; 4836 4837 if (unlikely(idle_cpu(cpu))) 4838 return 0; 4839 4840 /* 4841 * We may be recently in ticked or tickless idle mode. At the first 4842 * busy tick after returning from idle, we will update the busy stats. 4843 */ 4844 set_cpu_sd_state_busy(); 4845 nohz_balance_exit_idle(cpu); 4846 4847 /* 4848 * None are in tickless mode and hence no need for NOHZ idle load 4849 * balancing. 4850 */ 4851 if (likely(!atomic_read(&nohz.nr_cpus))) 4852 return 0; 4853 4854 if (time_before(now, nohz.next_balance)) 4855 return 0; 4856 4857 if (rq->nr_running >= 2) 4858 goto need_kick; 4859 4860 rcu_read_lock(); 4861 for_each_domain(cpu, sd) { 4862 struct sched_group *sg = sd->groups; 4863 struct sched_group_power *sgp = sg->sgp; 4864 int nr_busy = atomic_read(&sgp->nr_busy_cpus); 4865 4866 if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) 4867 goto need_kick_unlock; 4868 4869 if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight 4870 && (cpumask_first_and(nohz.idle_cpus_mask, 4871 sched_domain_span(sd)) < cpu)) 4872 goto need_kick_unlock; 4873 4874 if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING))) 4875 break; 4876 } 4877 rcu_read_unlock(); 4878 return 0; 4879 4880 need_kick_unlock: 4881 rcu_read_unlock(); 4882 need_kick: 4883 return 1; 4884 } 4885 #else 4886 static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { } 4887 #endif 4888 4889 /* 4890 * run_rebalance_domains is triggered when needed from the scheduler tick. 4891 * Also triggered for nohz idle balancing (with nohz_balancing_kick set). 4892 */ 4893 static void run_rebalance_domains(struct softirq_action *h) 4894 { 4895 int this_cpu = smp_processor_id(); 4896 struct rq *this_rq = cpu_rq(this_cpu); 4897 enum cpu_idle_type idle = this_rq->idle_balance ? 4898 CPU_IDLE : CPU_NOT_IDLE; 4899 4900 rebalance_domains(this_cpu, idle); 4901 4902 /* 4903 * If this cpu has a pending nohz_balance_kick, then do the 4904 * balancing on behalf of the other idle cpus whose ticks are 4905 * stopped. 4906 */ 4907 nohz_idle_balance(this_cpu, idle); 4908 } 4909 4910 static inline int on_null_domain(int cpu) 4911 { 4912 return !rcu_dereference_sched(cpu_rq(cpu)->sd); 4913 } 4914 4915 /* 4916 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. 4917 */ 4918 void trigger_load_balance(struct rq *rq, int cpu) 4919 { 4920 /* Don't need to rebalance while attached to NULL domain */ 4921 if (time_after_eq(jiffies, rq->next_balance) && 4922 likely(!on_null_domain(cpu))) 4923 raise_softirq(SCHED_SOFTIRQ); 4924 #ifdef CONFIG_NO_HZ 4925 if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu))) 4926 nohz_balancer_kick(cpu); 4927 #endif 4928 } 4929 4930 static void rq_online_fair(struct rq *rq) 4931 { 4932 update_sysctl(); 4933 } 4934 4935 static void rq_offline_fair(struct rq *rq) 4936 { 4937 update_sysctl(); 4938 4939 /* Ensure any throttled groups are reachable by pick_next_task */ 4940 unthrottle_offline_cfs_rqs(rq); 4941 } 4942 4943 #endif /* CONFIG_SMP */ 4944 4945 /* 4946 * scheduler tick hitting a task of our scheduling class: 4947 */ 4948 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) 4949 { 4950 struct cfs_rq *cfs_rq; 4951 struct sched_entity *se = &curr->se; 4952 4953 for_each_sched_entity(se) { 4954 cfs_rq = cfs_rq_of(se); 4955 entity_tick(cfs_rq, se, queued); 4956 } 4957 } 4958 4959 /* 4960 * called on fork with the child task as argument from the parent's context 4961 * - child not yet on the tasklist 4962 * - preemption disabled 4963 */ 4964 static void task_fork_fair(struct task_struct *p) 4965 { 4966 struct cfs_rq *cfs_rq; 4967 struct sched_entity *se = &p->se, *curr; 4968 int this_cpu = smp_processor_id(); 4969 struct rq *rq = this_rq(); 4970 unsigned long flags; 4971 4972 raw_spin_lock_irqsave(&rq->lock, flags); 4973 4974 update_rq_clock(rq); 4975 4976 cfs_rq = task_cfs_rq(current); 4977 curr = cfs_rq->curr; 4978 4979 if (unlikely(task_cpu(p) != this_cpu)) { 4980 rcu_read_lock(); 4981 __set_task_cpu(p, this_cpu); 4982 rcu_read_unlock(); 4983 } 4984 4985 update_curr(cfs_rq); 4986 4987 if (curr) 4988 se->vruntime = curr->vruntime; 4989 place_entity(cfs_rq, se, 1); 4990 4991 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { 4992 /* 4993 * Upon rescheduling, sched_class::put_prev_task() will place 4994 * 'current' within the tree based on its new key value. 4995 */ 4996 swap(curr->vruntime, se->vruntime); 4997 resched_task(rq->curr); 4998 } 4999 5000 se->vruntime -= cfs_rq->min_vruntime; 5001 5002 raw_spin_unlock_irqrestore(&rq->lock, flags); 5003 } 5004 5005 /* 5006 * Priority of the task has changed. Check to see if we preempt 5007 * the current task. 5008 */ 5009 static void 5010 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) 5011 { 5012 if (!p->se.on_rq) 5013 return; 5014 5015 /* 5016 * Reschedule if we are currently running on this runqueue and 5017 * our priority decreased, or if we are not currently running on 5018 * this runqueue and our priority is higher than the current's 5019 */ 5020 if (rq->curr == p) { 5021 if (p->prio > oldprio) 5022 resched_task(rq->curr); 5023 } else 5024 check_preempt_curr(rq, p, 0); 5025 } 5026 5027 static void switched_from_fair(struct rq *rq, struct task_struct *p) 5028 { 5029 struct sched_entity *se = &p->se; 5030 struct cfs_rq *cfs_rq = cfs_rq_of(se); 5031 5032 /* 5033 * Ensure the task's vruntime is normalized, so that when its 5034 * switched back to the fair class the enqueue_entity(.flags=0) will 5035 * do the right thing. 5036 * 5037 * If it was on_rq, then the dequeue_entity(.flags=0) will already 5038 * have normalized the vruntime, if it was !on_rq, then only when 5039 * the task is sleeping will it still have non-normalized vruntime. 5040 */ 5041 if (!se->on_rq && p->state != TASK_RUNNING) { 5042 /* 5043 * Fix up our vruntime so that the current sleep doesn't 5044 * cause 'unlimited' sleep bonus. 5045 */ 5046 place_entity(cfs_rq, se, 0); 5047 se->vruntime -= cfs_rq->min_vruntime; 5048 } 5049 } 5050 5051 /* 5052 * We switched to the sched_fair class. 5053 */ 5054 static void switched_to_fair(struct rq *rq, struct task_struct *p) 5055 { 5056 if (!p->se.on_rq) 5057 return; 5058 5059 /* 5060 * We were most likely switched from sched_rt, so 5061 * kick off the schedule if running, otherwise just see 5062 * if we can still preempt the current task. 5063 */ 5064 if (rq->curr == p) 5065 resched_task(rq->curr); 5066 else 5067 check_preempt_curr(rq, p, 0); 5068 } 5069 5070 /* Account for a task changing its policy or group. 5071 * 5072 * This routine is mostly called to set cfs_rq->curr field when a task 5073 * migrates between groups/classes. 5074 */ 5075 static void set_curr_task_fair(struct rq *rq) 5076 { 5077 struct sched_entity *se = &rq->curr->se; 5078 5079 for_each_sched_entity(se) { 5080 struct cfs_rq *cfs_rq = cfs_rq_of(se); 5081 5082 set_next_entity(cfs_rq, se); 5083 /* ensure bandwidth has been allocated on our new cfs_rq */ 5084 account_cfs_rq_runtime(cfs_rq, 0); 5085 } 5086 } 5087 5088 void init_cfs_rq(struct cfs_rq *cfs_rq) 5089 { 5090 cfs_rq->tasks_timeline = RB_ROOT; 5091 cfs_rq->min_vruntime = (u64)(-(1LL << 20)); 5092 #ifndef CONFIG_64BIT 5093 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 5094 #endif 5095 } 5096 5097 #ifdef CONFIG_FAIR_GROUP_SCHED 5098 static void task_move_group_fair(struct task_struct *p, int on_rq) 5099 { 5100 /* 5101 * If the task was not on the rq at the time of this cgroup movement 5102 * it must have been asleep, sleeping tasks keep their ->vruntime 5103 * absolute on their old rq until wakeup (needed for the fair sleeper 5104 * bonus in place_entity()). 5105 * 5106 * If it was on the rq, we've just 'preempted' it, which does convert 5107 * ->vruntime to a relative base. 5108 * 5109 * Make sure both cases convert their relative position when migrating 5110 * to another cgroup's rq. This does somewhat interfere with the 5111 * fair sleeper stuff for the first placement, but who cares. 5112 */ 5113 /* 5114 * When !on_rq, vruntime of the task has usually NOT been normalized. 5115 * But there are some cases where it has already been normalized: 5116 * 5117 * - Moving a forked child which is waiting for being woken up by 5118 * wake_up_new_task(). 5119 * - Moving a task which has been woken up by try_to_wake_up() and 5120 * waiting for actually being woken up by sched_ttwu_pending(). 5121 * 5122 * To prevent boost or penalty in the new cfs_rq caused by delta 5123 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. 5124 */ 5125 if (!on_rq && (!p->se.sum_exec_runtime || p->state == TASK_WAKING)) 5126 on_rq = 1; 5127 5128 if (!on_rq) 5129 p->se.vruntime -= cfs_rq_of(&p->se)->min_vruntime; 5130 set_task_rq(p, task_cpu(p)); 5131 if (!on_rq) 5132 p->se.vruntime += cfs_rq_of(&p->se)->min_vruntime; 5133 } 5134 5135 void free_fair_sched_group(struct task_group *tg) 5136 { 5137 int i; 5138 5139 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); 5140 5141 for_each_possible_cpu(i) { 5142 if (tg->cfs_rq) 5143 kfree(tg->cfs_rq[i]); 5144 if (tg->se) 5145 kfree(tg->se[i]); 5146 } 5147 5148 kfree(tg->cfs_rq); 5149 kfree(tg->se); 5150 } 5151 5152 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 5153 { 5154 struct cfs_rq *cfs_rq; 5155 struct sched_entity *se; 5156 int i; 5157 5158 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL); 5159 if (!tg->cfs_rq) 5160 goto err; 5161 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL); 5162 if (!tg->se) 5163 goto err; 5164 5165 tg->shares = NICE_0_LOAD; 5166 5167 init_cfs_bandwidth(tg_cfs_bandwidth(tg)); 5168 5169 for_each_possible_cpu(i) { 5170 cfs_rq = kzalloc_node(sizeof(struct cfs_rq), 5171 GFP_KERNEL, cpu_to_node(i)); 5172 if (!cfs_rq) 5173 goto err; 5174 5175 se = kzalloc_node(sizeof(struct sched_entity), 5176 GFP_KERNEL, cpu_to_node(i)); 5177 if (!se) 5178 goto err_free_rq; 5179 5180 init_cfs_rq(cfs_rq); 5181 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); 5182 } 5183 5184 return 1; 5185 5186 err_free_rq: 5187 kfree(cfs_rq); 5188 err: 5189 return 0; 5190 } 5191 5192 void unregister_fair_sched_group(struct task_group *tg, int cpu) 5193 { 5194 struct rq *rq = cpu_rq(cpu); 5195 unsigned long flags; 5196 5197 /* 5198 * Only empty task groups can be destroyed; so we can speculatively 5199 * check on_list without danger of it being re-added. 5200 */ 5201 if (!tg->cfs_rq[cpu]->on_list) 5202 return; 5203 5204 raw_spin_lock_irqsave(&rq->lock, flags); 5205 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); 5206 raw_spin_unlock_irqrestore(&rq->lock, flags); 5207 } 5208 5209 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, 5210 struct sched_entity *se, int cpu, 5211 struct sched_entity *parent) 5212 { 5213 struct rq *rq = cpu_rq(cpu); 5214 5215 cfs_rq->tg = tg; 5216 cfs_rq->rq = rq; 5217 #ifdef CONFIG_SMP 5218 /* allow initial update_cfs_load() to truncate */ 5219 cfs_rq->load_stamp = 1; 5220 #endif 5221 init_cfs_rq_runtime(cfs_rq); 5222 5223 tg->cfs_rq[cpu] = cfs_rq; 5224 tg->se[cpu] = se; 5225 5226 /* se could be NULL for root_task_group */ 5227 if (!se) 5228 return; 5229 5230 if (!parent) 5231 se->cfs_rq = &rq->cfs; 5232 else 5233 se->cfs_rq = parent->my_q; 5234 5235 se->my_q = cfs_rq; 5236 update_load_set(&se->load, 0); 5237 se->parent = parent; 5238 } 5239 5240 static DEFINE_MUTEX(shares_mutex); 5241 5242 int sched_group_set_shares(struct task_group *tg, unsigned long shares) 5243 { 5244 int i; 5245 unsigned long flags; 5246 5247 /* 5248 * We can't change the weight of the root cgroup. 5249 */ 5250 if (!tg->se[0]) 5251 return -EINVAL; 5252 5253 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); 5254 5255 mutex_lock(&shares_mutex); 5256 if (tg->shares == shares) 5257 goto done; 5258 5259 tg->shares = shares; 5260 for_each_possible_cpu(i) { 5261 struct rq *rq = cpu_rq(i); 5262 struct sched_entity *se; 5263 5264 se = tg->se[i]; 5265 /* Propagate contribution to hierarchy */ 5266 raw_spin_lock_irqsave(&rq->lock, flags); 5267 for_each_sched_entity(se) 5268 update_cfs_shares(group_cfs_rq(se)); 5269 raw_spin_unlock_irqrestore(&rq->lock, flags); 5270 } 5271 5272 done: 5273 mutex_unlock(&shares_mutex); 5274 return 0; 5275 } 5276 #else /* CONFIG_FAIR_GROUP_SCHED */ 5277 5278 void free_fair_sched_group(struct task_group *tg) { } 5279 5280 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 5281 { 5282 return 1; 5283 } 5284 5285 void unregister_fair_sched_group(struct task_group *tg, int cpu) { } 5286 5287 #endif /* CONFIG_FAIR_GROUP_SCHED */ 5288 5289 5290 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) 5291 { 5292 struct sched_entity *se = &task->se; 5293 unsigned int rr_interval = 0; 5294 5295 /* 5296 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise 5297 * idle runqueue: 5298 */ 5299 if (rq->cfs.load.weight) 5300 rr_interval = NS_TO_JIFFIES(sched_slice(&rq->cfs, se)); 5301 5302 return rr_interval; 5303 } 5304 5305 /* 5306 * All the scheduling class methods: 5307 */ 5308 const struct sched_class fair_sched_class = { 5309 .next = &idle_sched_class, 5310 .enqueue_task = enqueue_task_fair, 5311 .dequeue_task = dequeue_task_fair, 5312 .yield_task = yield_task_fair, 5313 .yield_to_task = yield_to_task_fair, 5314 5315 .check_preempt_curr = check_preempt_wakeup, 5316 5317 .pick_next_task = pick_next_task_fair, 5318 .put_prev_task = put_prev_task_fair, 5319 5320 #ifdef CONFIG_SMP 5321 .select_task_rq = select_task_rq_fair, 5322 5323 .rq_online = rq_online_fair, 5324 .rq_offline = rq_offline_fair, 5325 5326 .task_waking = task_waking_fair, 5327 #endif 5328 5329 .set_curr_task = set_curr_task_fair, 5330 .task_tick = task_tick_fair, 5331 .task_fork = task_fork_fair, 5332 5333 .prio_changed = prio_changed_fair, 5334 .switched_from = switched_from_fair, 5335 .switched_to = switched_to_fair, 5336 5337 .get_rr_interval = get_rr_interval_fair, 5338 5339 #ifdef CONFIG_FAIR_GROUP_SCHED 5340 .task_move_group = task_move_group_fair, 5341 #endif 5342 }; 5343 5344 #ifdef CONFIG_SCHED_DEBUG 5345 void print_cfs_stats(struct seq_file *m, int cpu) 5346 { 5347 struct cfs_rq *cfs_rq; 5348 5349 rcu_read_lock(); 5350 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) 5351 print_cfs_rq(m, cpu, cfs_rq); 5352 rcu_read_unlock(); 5353 } 5354 #endif 5355 5356 __init void init_sched_fair_class(void) 5357 { 5358 #ifdef CONFIG_SMP 5359 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); 5360 5361 #ifdef CONFIG_NO_HZ 5362 nohz.next_balance = jiffies; 5363 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); 5364 cpu_notifier(sched_ilb_notifier, 0); 5365 #endif 5366 #endif /* SMP */ 5367 5368 } 5369