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/cpuidle.h> 27 #include <linux/slab.h> 28 #include <linux/profile.h> 29 #include <linux/interrupt.h> 30 #include <linux/mempolicy.h> 31 #include <linux/migrate.h> 32 #include <linux/task_work.h> 33 34 #include <trace/events/sched.h> 35 36 #include "sched.h" 37 38 /* 39 * Targeted preemption latency for CPU-bound tasks: 40 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) 41 * 42 * NOTE: this latency value is not the same as the concept of 43 * 'timeslice length' - timeslices in CFS are of variable length 44 * and have no persistent notion like in traditional, time-slice 45 * based scheduling concepts. 46 * 47 * (to see the precise effective timeslice length of your workload, 48 * run vmstat and monitor the context-switches (cs) field) 49 */ 50 unsigned int sysctl_sched_latency = 6000000ULL; 51 unsigned int normalized_sysctl_sched_latency = 6000000ULL; 52 53 /* 54 * The initial- and re-scaling of tunables is configurable 55 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) 56 * 57 * Options are: 58 * SCHED_TUNABLESCALING_NONE - unscaled, always *1 59 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) 60 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus 61 */ 62 enum sched_tunable_scaling sysctl_sched_tunable_scaling 63 = SCHED_TUNABLESCALING_LOG; 64 65 /* 66 * Minimal preemption granularity for CPU-bound tasks: 67 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) 68 */ 69 unsigned int sysctl_sched_min_granularity = 750000ULL; 70 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; 71 72 /* 73 * is kept at sysctl_sched_latency / sysctl_sched_min_granularity 74 */ 75 static unsigned int sched_nr_latency = 8; 76 77 /* 78 * After fork, child runs first. If set to 0 (default) then 79 * parent will (try to) run first. 80 */ 81 unsigned int sysctl_sched_child_runs_first __read_mostly; 82 83 /* 84 * SCHED_OTHER wake-up granularity. 85 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) 86 * 87 * This option delays the preemption effects of decoupled workloads 88 * and reduces their over-scheduling. Synchronous workloads will still 89 * have immediate wakeup/sleep latencies. 90 */ 91 unsigned int sysctl_sched_wakeup_granularity = 1000000UL; 92 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; 93 94 const_debug unsigned int sysctl_sched_migration_cost = 500000UL; 95 96 /* 97 * The exponential sliding window over which load is averaged for shares 98 * distribution. 99 * (default: 10msec) 100 */ 101 unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; 102 103 #ifdef CONFIG_CFS_BANDWIDTH 104 /* 105 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool 106 * each time a cfs_rq requests quota. 107 * 108 * Note: in the case that the slice exceeds the runtime remaining (either due 109 * to consumption or the quota being specified to be smaller than the slice) 110 * we will always only issue the remaining available time. 111 * 112 * default: 5 msec, units: microseconds 113 */ 114 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; 115 #endif 116 117 static inline void update_load_add(struct load_weight *lw, unsigned long inc) 118 { 119 lw->weight += inc; 120 lw->inv_weight = 0; 121 } 122 123 static inline void update_load_sub(struct load_weight *lw, unsigned long dec) 124 { 125 lw->weight -= dec; 126 lw->inv_weight = 0; 127 } 128 129 static inline void update_load_set(struct load_weight *lw, unsigned long w) 130 { 131 lw->weight = w; 132 lw->inv_weight = 0; 133 } 134 135 /* 136 * Increase the granularity value when there are more CPUs, 137 * because with more CPUs the 'effective latency' as visible 138 * to users decreases. But the relationship is not linear, 139 * so pick a second-best guess by going with the log2 of the 140 * number of CPUs. 141 * 142 * This idea comes from the SD scheduler of Con Kolivas: 143 */ 144 static int get_update_sysctl_factor(void) 145 { 146 unsigned int cpus = min_t(int, num_online_cpus(), 8); 147 unsigned int factor; 148 149 switch (sysctl_sched_tunable_scaling) { 150 case SCHED_TUNABLESCALING_NONE: 151 factor = 1; 152 break; 153 case SCHED_TUNABLESCALING_LINEAR: 154 factor = cpus; 155 break; 156 case SCHED_TUNABLESCALING_LOG: 157 default: 158 factor = 1 + ilog2(cpus); 159 break; 160 } 161 162 return factor; 163 } 164 165 static void update_sysctl(void) 166 { 167 unsigned int factor = get_update_sysctl_factor(); 168 169 #define SET_SYSCTL(name) \ 170 (sysctl_##name = (factor) * normalized_sysctl_##name) 171 SET_SYSCTL(sched_min_granularity); 172 SET_SYSCTL(sched_latency); 173 SET_SYSCTL(sched_wakeup_granularity); 174 #undef SET_SYSCTL 175 } 176 177 void sched_init_granularity(void) 178 { 179 update_sysctl(); 180 } 181 182 #define WMULT_CONST (~0U) 183 #define WMULT_SHIFT 32 184 185 static void __update_inv_weight(struct load_weight *lw) 186 { 187 unsigned long w; 188 189 if (likely(lw->inv_weight)) 190 return; 191 192 w = scale_load_down(lw->weight); 193 194 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) 195 lw->inv_weight = 1; 196 else if (unlikely(!w)) 197 lw->inv_weight = WMULT_CONST; 198 else 199 lw->inv_weight = WMULT_CONST / w; 200 } 201 202 /* 203 * delta_exec * weight / lw.weight 204 * OR 205 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT 206 * 207 * Either weight := NICE_0_LOAD and lw \e prio_to_wmult[], in which case 208 * we're guaranteed shift stays positive because inv_weight is guaranteed to 209 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. 210 * 211 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus 212 * weight/lw.weight <= 1, and therefore our shift will also be positive. 213 */ 214 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) 215 { 216 u64 fact = scale_load_down(weight); 217 int shift = WMULT_SHIFT; 218 219 __update_inv_weight(lw); 220 221 if (unlikely(fact >> 32)) { 222 while (fact >> 32) { 223 fact >>= 1; 224 shift--; 225 } 226 } 227 228 /* hint to use a 32x32->64 mul */ 229 fact = (u64)(u32)fact * lw->inv_weight; 230 231 while (fact >> 32) { 232 fact >>= 1; 233 shift--; 234 } 235 236 return mul_u64_u32_shr(delta_exec, fact, shift); 237 } 238 239 240 const struct sched_class fair_sched_class; 241 242 /************************************************************** 243 * CFS operations on generic schedulable entities: 244 */ 245 246 #ifdef CONFIG_FAIR_GROUP_SCHED 247 248 /* cpu runqueue to which this cfs_rq is attached */ 249 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 250 { 251 return cfs_rq->rq; 252 } 253 254 /* An entity is a task if it doesn't "own" a runqueue */ 255 #define entity_is_task(se) (!se->my_q) 256 257 static inline struct task_struct *task_of(struct sched_entity *se) 258 { 259 #ifdef CONFIG_SCHED_DEBUG 260 WARN_ON_ONCE(!entity_is_task(se)); 261 #endif 262 return container_of(se, struct task_struct, se); 263 } 264 265 /* Walk up scheduling entities hierarchy */ 266 #define for_each_sched_entity(se) \ 267 for (; se; se = se->parent) 268 269 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 270 { 271 return p->se.cfs_rq; 272 } 273 274 /* runqueue on which this entity is (to be) queued */ 275 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 276 { 277 return se->cfs_rq; 278 } 279 280 /* runqueue "owned" by this group */ 281 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 282 { 283 return grp->my_q; 284 } 285 286 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, 287 int force_update); 288 289 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 290 { 291 if (!cfs_rq->on_list) { 292 /* 293 * Ensure we either appear before our parent (if already 294 * enqueued) or force our parent to appear after us when it is 295 * enqueued. The fact that we always enqueue bottom-up 296 * reduces this to two cases. 297 */ 298 if (cfs_rq->tg->parent && 299 cfs_rq->tg->parent->cfs_rq[cpu_of(rq_of(cfs_rq))]->on_list) { 300 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, 301 &rq_of(cfs_rq)->leaf_cfs_rq_list); 302 } else { 303 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, 304 &rq_of(cfs_rq)->leaf_cfs_rq_list); 305 } 306 307 cfs_rq->on_list = 1; 308 /* We should have no load, but we need to update last_decay. */ 309 update_cfs_rq_blocked_load(cfs_rq, 0); 310 } 311 } 312 313 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 314 { 315 if (cfs_rq->on_list) { 316 list_del_rcu(&cfs_rq->leaf_cfs_rq_list); 317 cfs_rq->on_list = 0; 318 } 319 } 320 321 /* Iterate thr' all leaf cfs_rq's on a runqueue */ 322 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 323 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) 324 325 /* Do the two (enqueued) entities belong to the same group ? */ 326 static inline struct cfs_rq * 327 is_same_group(struct sched_entity *se, struct sched_entity *pse) 328 { 329 if (se->cfs_rq == pse->cfs_rq) 330 return se->cfs_rq; 331 332 return NULL; 333 } 334 335 static inline struct sched_entity *parent_entity(struct sched_entity *se) 336 { 337 return se->parent; 338 } 339 340 static void 341 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 342 { 343 int se_depth, pse_depth; 344 345 /* 346 * preemption test can be made between sibling entities who are in the 347 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of 348 * both tasks until we find their ancestors who are siblings of common 349 * parent. 350 */ 351 352 /* First walk up until both entities are at same depth */ 353 se_depth = (*se)->depth; 354 pse_depth = (*pse)->depth; 355 356 while (se_depth > pse_depth) { 357 se_depth--; 358 *se = parent_entity(*se); 359 } 360 361 while (pse_depth > se_depth) { 362 pse_depth--; 363 *pse = parent_entity(*pse); 364 } 365 366 while (!is_same_group(*se, *pse)) { 367 *se = parent_entity(*se); 368 *pse = parent_entity(*pse); 369 } 370 } 371 372 #else /* !CONFIG_FAIR_GROUP_SCHED */ 373 374 static inline struct task_struct *task_of(struct sched_entity *se) 375 { 376 return container_of(se, struct task_struct, se); 377 } 378 379 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 380 { 381 return container_of(cfs_rq, struct rq, cfs); 382 } 383 384 #define entity_is_task(se) 1 385 386 #define for_each_sched_entity(se) \ 387 for (; se; se = NULL) 388 389 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 390 { 391 return &task_rq(p)->cfs; 392 } 393 394 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 395 { 396 struct task_struct *p = task_of(se); 397 struct rq *rq = task_rq(p); 398 399 return &rq->cfs; 400 } 401 402 /* runqueue "owned" by this group */ 403 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 404 { 405 return NULL; 406 } 407 408 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 409 { 410 } 411 412 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 413 { 414 } 415 416 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 417 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) 418 419 static inline struct sched_entity *parent_entity(struct sched_entity *se) 420 { 421 return NULL; 422 } 423 424 static inline void 425 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 426 { 427 } 428 429 #endif /* CONFIG_FAIR_GROUP_SCHED */ 430 431 static __always_inline 432 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); 433 434 /************************************************************** 435 * Scheduling class tree data structure manipulation methods: 436 */ 437 438 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) 439 { 440 s64 delta = (s64)(vruntime - max_vruntime); 441 if (delta > 0) 442 max_vruntime = vruntime; 443 444 return max_vruntime; 445 } 446 447 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) 448 { 449 s64 delta = (s64)(vruntime - min_vruntime); 450 if (delta < 0) 451 min_vruntime = vruntime; 452 453 return min_vruntime; 454 } 455 456 static inline int entity_before(struct sched_entity *a, 457 struct sched_entity *b) 458 { 459 return (s64)(a->vruntime - b->vruntime) < 0; 460 } 461 462 static void update_min_vruntime(struct cfs_rq *cfs_rq) 463 { 464 u64 vruntime = cfs_rq->min_vruntime; 465 466 if (cfs_rq->curr) 467 vruntime = cfs_rq->curr->vruntime; 468 469 if (cfs_rq->rb_leftmost) { 470 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, 471 struct sched_entity, 472 run_node); 473 474 if (!cfs_rq->curr) 475 vruntime = se->vruntime; 476 else 477 vruntime = min_vruntime(vruntime, se->vruntime); 478 } 479 480 /* ensure we never gain time by being placed backwards. */ 481 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); 482 #ifndef CONFIG_64BIT 483 smp_wmb(); 484 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 485 #endif 486 } 487 488 /* 489 * Enqueue an entity into the rb-tree: 490 */ 491 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 492 { 493 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; 494 struct rb_node *parent = NULL; 495 struct sched_entity *entry; 496 int leftmost = 1; 497 498 /* 499 * Find the right place in the rbtree: 500 */ 501 while (*link) { 502 parent = *link; 503 entry = rb_entry(parent, struct sched_entity, run_node); 504 /* 505 * We dont care about collisions. Nodes with 506 * the same key stay together. 507 */ 508 if (entity_before(se, entry)) { 509 link = &parent->rb_left; 510 } else { 511 link = &parent->rb_right; 512 leftmost = 0; 513 } 514 } 515 516 /* 517 * Maintain a cache of leftmost tree entries (it is frequently 518 * used): 519 */ 520 if (leftmost) 521 cfs_rq->rb_leftmost = &se->run_node; 522 523 rb_link_node(&se->run_node, parent, link); 524 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); 525 } 526 527 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 528 { 529 if (cfs_rq->rb_leftmost == &se->run_node) { 530 struct rb_node *next_node; 531 532 next_node = rb_next(&se->run_node); 533 cfs_rq->rb_leftmost = next_node; 534 } 535 536 rb_erase(&se->run_node, &cfs_rq->tasks_timeline); 537 } 538 539 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) 540 { 541 struct rb_node *left = cfs_rq->rb_leftmost; 542 543 if (!left) 544 return NULL; 545 546 return rb_entry(left, struct sched_entity, run_node); 547 } 548 549 static struct sched_entity *__pick_next_entity(struct sched_entity *se) 550 { 551 struct rb_node *next = rb_next(&se->run_node); 552 553 if (!next) 554 return NULL; 555 556 return rb_entry(next, struct sched_entity, run_node); 557 } 558 559 #ifdef CONFIG_SCHED_DEBUG 560 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) 561 { 562 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); 563 564 if (!last) 565 return NULL; 566 567 return rb_entry(last, struct sched_entity, run_node); 568 } 569 570 /************************************************************** 571 * Scheduling class statistics methods: 572 */ 573 574 int sched_proc_update_handler(struct ctl_table *table, int write, 575 void __user *buffer, size_t *lenp, 576 loff_t *ppos) 577 { 578 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 579 int factor = get_update_sysctl_factor(); 580 581 if (ret || !write) 582 return ret; 583 584 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, 585 sysctl_sched_min_granularity); 586 587 #define WRT_SYSCTL(name) \ 588 (normalized_sysctl_##name = sysctl_##name / (factor)) 589 WRT_SYSCTL(sched_min_granularity); 590 WRT_SYSCTL(sched_latency); 591 WRT_SYSCTL(sched_wakeup_granularity); 592 #undef WRT_SYSCTL 593 594 return 0; 595 } 596 #endif 597 598 /* 599 * delta /= w 600 */ 601 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) 602 { 603 if (unlikely(se->load.weight != NICE_0_LOAD)) 604 delta = __calc_delta(delta, NICE_0_LOAD, &se->load); 605 606 return delta; 607 } 608 609 /* 610 * The idea is to set a period in which each task runs once. 611 * 612 * When there are too many tasks (sched_nr_latency) we have to stretch 613 * this period because otherwise the slices get too small. 614 * 615 * p = (nr <= nl) ? l : l*nr/nl 616 */ 617 static u64 __sched_period(unsigned long nr_running) 618 { 619 u64 period = sysctl_sched_latency; 620 unsigned long nr_latency = sched_nr_latency; 621 622 if (unlikely(nr_running > nr_latency)) { 623 period = sysctl_sched_min_granularity; 624 period *= nr_running; 625 } 626 627 return period; 628 } 629 630 /* 631 * We calculate the wall-time slice from the period by taking a part 632 * proportional to the weight. 633 * 634 * s = p*P[w/rw] 635 */ 636 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 637 { 638 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); 639 640 for_each_sched_entity(se) { 641 struct load_weight *load; 642 struct load_weight lw; 643 644 cfs_rq = cfs_rq_of(se); 645 load = &cfs_rq->load; 646 647 if (unlikely(!se->on_rq)) { 648 lw = cfs_rq->load; 649 650 update_load_add(&lw, se->load.weight); 651 load = &lw; 652 } 653 slice = __calc_delta(slice, se->load.weight, load); 654 } 655 return slice; 656 } 657 658 /* 659 * We calculate the vruntime slice of a to-be-inserted task. 660 * 661 * vs = s/w 662 */ 663 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) 664 { 665 return calc_delta_fair(sched_slice(cfs_rq, se), se); 666 } 667 668 #ifdef CONFIG_SMP 669 static int select_idle_sibling(struct task_struct *p, int cpu); 670 static unsigned long task_h_load(struct task_struct *p); 671 672 static inline void __update_task_entity_contrib(struct sched_entity *se); 673 674 /* Give new task start runnable values to heavy its load in infant time */ 675 void init_task_runnable_average(struct task_struct *p) 676 { 677 u32 slice; 678 679 p->se.avg.decay_count = 0; 680 slice = sched_slice(task_cfs_rq(p), &p->se) >> 10; 681 p->se.avg.runnable_avg_sum = slice; 682 p->se.avg.runnable_avg_period = slice; 683 __update_task_entity_contrib(&p->se); 684 } 685 #else 686 void init_task_runnable_average(struct task_struct *p) 687 { 688 } 689 #endif 690 691 /* 692 * Update the current task's runtime statistics. 693 */ 694 static void update_curr(struct cfs_rq *cfs_rq) 695 { 696 struct sched_entity *curr = cfs_rq->curr; 697 u64 now = rq_clock_task(rq_of(cfs_rq)); 698 u64 delta_exec; 699 700 if (unlikely(!curr)) 701 return; 702 703 delta_exec = now - curr->exec_start; 704 if (unlikely((s64)delta_exec <= 0)) 705 return; 706 707 curr->exec_start = now; 708 709 schedstat_set(curr->statistics.exec_max, 710 max(delta_exec, curr->statistics.exec_max)); 711 712 curr->sum_exec_runtime += delta_exec; 713 schedstat_add(cfs_rq, exec_clock, delta_exec); 714 715 curr->vruntime += calc_delta_fair(delta_exec, curr); 716 update_min_vruntime(cfs_rq); 717 718 if (entity_is_task(curr)) { 719 struct task_struct *curtask = task_of(curr); 720 721 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); 722 cpuacct_charge(curtask, delta_exec); 723 account_group_exec_runtime(curtask, delta_exec); 724 } 725 726 account_cfs_rq_runtime(cfs_rq, delta_exec); 727 } 728 729 static void update_curr_fair(struct rq *rq) 730 { 731 update_curr(cfs_rq_of(&rq->curr->se)); 732 } 733 734 static inline void 735 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 736 { 737 schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq))); 738 } 739 740 /* 741 * Task is being enqueued - update stats: 742 */ 743 static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 744 { 745 /* 746 * Are we enqueueing a waiting task? (for current tasks 747 * a dequeue/enqueue event is a NOP) 748 */ 749 if (se != cfs_rq->curr) 750 update_stats_wait_start(cfs_rq, se); 751 } 752 753 static void 754 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) 755 { 756 schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max, 757 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start)); 758 schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1); 759 schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum + 760 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); 761 #ifdef CONFIG_SCHEDSTATS 762 if (entity_is_task(se)) { 763 trace_sched_stat_wait(task_of(se), 764 rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start); 765 } 766 #endif 767 schedstat_set(se->statistics.wait_start, 0); 768 } 769 770 static inline void 771 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 772 { 773 /* 774 * Mark the end of the wait period if dequeueing a 775 * waiting task: 776 */ 777 if (se != cfs_rq->curr) 778 update_stats_wait_end(cfs_rq, se); 779 } 780 781 /* 782 * We are picking a new current task - update its stats: 783 */ 784 static inline void 785 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 786 { 787 /* 788 * We are starting a new run period: 789 */ 790 se->exec_start = rq_clock_task(rq_of(cfs_rq)); 791 } 792 793 /************************************************** 794 * Scheduling class queueing methods: 795 */ 796 797 #ifdef CONFIG_NUMA_BALANCING 798 /* 799 * Approximate time to scan a full NUMA task in ms. The task scan period is 800 * calculated based on the tasks virtual memory size and 801 * numa_balancing_scan_size. 802 */ 803 unsigned int sysctl_numa_balancing_scan_period_min = 1000; 804 unsigned int sysctl_numa_balancing_scan_period_max = 60000; 805 806 /* Portion of address space to scan in MB */ 807 unsigned int sysctl_numa_balancing_scan_size = 256; 808 809 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ 810 unsigned int sysctl_numa_balancing_scan_delay = 1000; 811 812 static unsigned int task_nr_scan_windows(struct task_struct *p) 813 { 814 unsigned long rss = 0; 815 unsigned long nr_scan_pages; 816 817 /* 818 * Calculations based on RSS as non-present and empty pages are skipped 819 * by the PTE scanner and NUMA hinting faults should be trapped based 820 * on resident pages 821 */ 822 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); 823 rss = get_mm_rss(p->mm); 824 if (!rss) 825 rss = nr_scan_pages; 826 827 rss = round_up(rss, nr_scan_pages); 828 return rss / nr_scan_pages; 829 } 830 831 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ 832 #define MAX_SCAN_WINDOW 2560 833 834 static unsigned int task_scan_min(struct task_struct *p) 835 { 836 unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size); 837 unsigned int scan, floor; 838 unsigned int windows = 1; 839 840 if (scan_size < MAX_SCAN_WINDOW) 841 windows = MAX_SCAN_WINDOW / scan_size; 842 floor = 1000 / windows; 843 844 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); 845 return max_t(unsigned int, floor, scan); 846 } 847 848 static unsigned int task_scan_max(struct task_struct *p) 849 { 850 unsigned int smin = task_scan_min(p); 851 unsigned int smax; 852 853 /* Watch for min being lower than max due to floor calculations */ 854 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); 855 return max(smin, smax); 856 } 857 858 static void account_numa_enqueue(struct rq *rq, struct task_struct *p) 859 { 860 rq->nr_numa_running += (p->numa_preferred_nid != -1); 861 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); 862 } 863 864 static void account_numa_dequeue(struct rq *rq, struct task_struct *p) 865 { 866 rq->nr_numa_running -= (p->numa_preferred_nid != -1); 867 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); 868 } 869 870 struct numa_group { 871 atomic_t refcount; 872 873 spinlock_t lock; /* nr_tasks, tasks */ 874 int nr_tasks; 875 pid_t gid; 876 877 struct rcu_head rcu; 878 nodemask_t active_nodes; 879 unsigned long total_faults; 880 /* 881 * Faults_cpu is used to decide whether memory should move 882 * towards the CPU. As a consequence, these stats are weighted 883 * more by CPU use than by memory faults. 884 */ 885 unsigned long *faults_cpu; 886 unsigned long faults[0]; 887 }; 888 889 /* Shared or private faults. */ 890 #define NR_NUMA_HINT_FAULT_TYPES 2 891 892 /* Memory and CPU locality */ 893 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) 894 895 /* Averaged statistics, and temporary buffers. */ 896 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) 897 898 pid_t task_numa_group_id(struct task_struct *p) 899 { 900 return p->numa_group ? p->numa_group->gid : 0; 901 } 902 903 /* 904 * The averaged statistics, shared & private, memory & cpu, 905 * occupy the first half of the array. The second half of the 906 * array is for current counters, which are averaged into the 907 * first set by task_numa_placement. 908 */ 909 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv) 910 { 911 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv; 912 } 913 914 static inline unsigned long task_faults(struct task_struct *p, int nid) 915 { 916 if (!p->numa_faults) 917 return 0; 918 919 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + 920 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)]; 921 } 922 923 static inline unsigned long group_faults(struct task_struct *p, int nid) 924 { 925 if (!p->numa_group) 926 return 0; 927 928 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] + 929 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)]; 930 } 931 932 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) 933 { 934 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + 935 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)]; 936 } 937 938 /* Handle placement on systems where not all nodes are directly connected. */ 939 static unsigned long score_nearby_nodes(struct task_struct *p, int nid, 940 int maxdist, bool task) 941 { 942 unsigned long score = 0; 943 int node; 944 945 /* 946 * All nodes are directly connected, and the same distance 947 * from each other. No need for fancy placement algorithms. 948 */ 949 if (sched_numa_topology_type == NUMA_DIRECT) 950 return 0; 951 952 /* 953 * This code is called for each node, introducing N^2 complexity, 954 * which should be ok given the number of nodes rarely exceeds 8. 955 */ 956 for_each_online_node(node) { 957 unsigned long faults; 958 int dist = node_distance(nid, node); 959 960 /* 961 * The furthest away nodes in the system are not interesting 962 * for placement; nid was already counted. 963 */ 964 if (dist == sched_max_numa_distance || node == nid) 965 continue; 966 967 /* 968 * On systems with a backplane NUMA topology, compare groups 969 * of nodes, and move tasks towards the group with the most 970 * memory accesses. When comparing two nodes at distance 971 * "hoplimit", only nodes closer by than "hoplimit" are part 972 * of each group. Skip other nodes. 973 */ 974 if (sched_numa_topology_type == NUMA_BACKPLANE && 975 dist > maxdist) 976 continue; 977 978 /* Add up the faults from nearby nodes. */ 979 if (task) 980 faults = task_faults(p, node); 981 else 982 faults = group_faults(p, node); 983 984 /* 985 * On systems with a glueless mesh NUMA topology, there are 986 * no fixed "groups of nodes". Instead, nodes that are not 987 * directly connected bounce traffic through intermediate 988 * nodes; a numa_group can occupy any set of nodes. 989 * The further away a node is, the less the faults count. 990 * This seems to result in good task placement. 991 */ 992 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { 993 faults *= (sched_max_numa_distance - dist); 994 faults /= (sched_max_numa_distance - LOCAL_DISTANCE); 995 } 996 997 score += faults; 998 } 999 1000 return score; 1001 } 1002 1003 /* 1004 * These return the fraction of accesses done by a particular task, or 1005 * task group, on a particular numa node. The group weight is given a 1006 * larger multiplier, in order to group tasks together that are almost 1007 * evenly spread out between numa nodes. 1008 */ 1009 static inline unsigned long task_weight(struct task_struct *p, int nid, 1010 int dist) 1011 { 1012 unsigned long faults, total_faults; 1013 1014 if (!p->numa_faults) 1015 return 0; 1016 1017 total_faults = p->total_numa_faults; 1018 1019 if (!total_faults) 1020 return 0; 1021 1022 faults = task_faults(p, nid); 1023 faults += score_nearby_nodes(p, nid, dist, true); 1024 1025 return 1000 * faults / total_faults; 1026 } 1027 1028 static inline unsigned long group_weight(struct task_struct *p, int nid, 1029 int dist) 1030 { 1031 unsigned long faults, total_faults; 1032 1033 if (!p->numa_group) 1034 return 0; 1035 1036 total_faults = p->numa_group->total_faults; 1037 1038 if (!total_faults) 1039 return 0; 1040 1041 faults = group_faults(p, nid); 1042 faults += score_nearby_nodes(p, nid, dist, false); 1043 1044 return 1000 * faults / total_faults; 1045 } 1046 1047 bool should_numa_migrate_memory(struct task_struct *p, struct page * page, 1048 int src_nid, int dst_cpu) 1049 { 1050 struct numa_group *ng = p->numa_group; 1051 int dst_nid = cpu_to_node(dst_cpu); 1052 int last_cpupid, this_cpupid; 1053 1054 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); 1055 1056 /* 1057 * Multi-stage node selection is used in conjunction with a periodic 1058 * migration fault to build a temporal task<->page relation. By using 1059 * a two-stage filter we remove short/unlikely relations. 1060 * 1061 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate 1062 * a task's usage of a particular page (n_p) per total usage of this 1063 * page (n_t) (in a given time-span) to a probability. 1064 * 1065 * Our periodic faults will sample this probability and getting the 1066 * same result twice in a row, given these samples are fully 1067 * independent, is then given by P(n)^2, provided our sample period 1068 * is sufficiently short compared to the usage pattern. 1069 * 1070 * This quadric squishes small probabilities, making it less likely we 1071 * act on an unlikely task<->page relation. 1072 */ 1073 last_cpupid = page_cpupid_xchg_last(page, this_cpupid); 1074 if (!cpupid_pid_unset(last_cpupid) && 1075 cpupid_to_nid(last_cpupid) != dst_nid) 1076 return false; 1077 1078 /* Always allow migrate on private faults */ 1079 if (cpupid_match_pid(p, last_cpupid)) 1080 return true; 1081 1082 /* A shared fault, but p->numa_group has not been set up yet. */ 1083 if (!ng) 1084 return true; 1085 1086 /* 1087 * Do not migrate if the destination is not a node that 1088 * is actively used by this numa group. 1089 */ 1090 if (!node_isset(dst_nid, ng->active_nodes)) 1091 return false; 1092 1093 /* 1094 * Source is a node that is not actively used by this 1095 * numa group, while the destination is. Migrate. 1096 */ 1097 if (!node_isset(src_nid, ng->active_nodes)) 1098 return true; 1099 1100 /* 1101 * Both source and destination are nodes in active 1102 * use by this numa group. Maximize memory bandwidth 1103 * by migrating from more heavily used groups, to less 1104 * heavily used ones, spreading the load around. 1105 * Use a 1/4 hysteresis to avoid spurious page movement. 1106 */ 1107 return group_faults(p, dst_nid) < (group_faults(p, src_nid) * 3 / 4); 1108 } 1109 1110 static unsigned long weighted_cpuload(const int cpu); 1111 static unsigned long source_load(int cpu, int type); 1112 static unsigned long target_load(int cpu, int type); 1113 static unsigned long capacity_of(int cpu); 1114 static long effective_load(struct task_group *tg, int cpu, long wl, long wg); 1115 1116 /* Cached statistics for all CPUs within a node */ 1117 struct numa_stats { 1118 unsigned long nr_running; 1119 unsigned long load; 1120 1121 /* Total compute capacity of CPUs on a node */ 1122 unsigned long compute_capacity; 1123 1124 /* Approximate capacity in terms of runnable tasks on a node */ 1125 unsigned long task_capacity; 1126 int has_free_capacity; 1127 }; 1128 1129 /* 1130 * XXX borrowed from update_sg_lb_stats 1131 */ 1132 static void update_numa_stats(struct numa_stats *ns, int nid) 1133 { 1134 int smt, cpu, cpus = 0; 1135 unsigned long capacity; 1136 1137 memset(ns, 0, sizeof(*ns)); 1138 for_each_cpu(cpu, cpumask_of_node(nid)) { 1139 struct rq *rq = cpu_rq(cpu); 1140 1141 ns->nr_running += rq->nr_running; 1142 ns->load += weighted_cpuload(cpu); 1143 ns->compute_capacity += capacity_of(cpu); 1144 1145 cpus++; 1146 } 1147 1148 /* 1149 * If we raced with hotplug and there are no CPUs left in our mask 1150 * the @ns structure is NULL'ed and task_numa_compare() will 1151 * not find this node attractive. 1152 * 1153 * We'll either bail at !has_free_capacity, or we'll detect a huge 1154 * imbalance and bail there. 1155 */ 1156 if (!cpus) 1157 return; 1158 1159 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */ 1160 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity); 1161 capacity = cpus / smt; /* cores */ 1162 1163 ns->task_capacity = min_t(unsigned, capacity, 1164 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); 1165 ns->has_free_capacity = (ns->nr_running < ns->task_capacity); 1166 } 1167 1168 struct task_numa_env { 1169 struct task_struct *p; 1170 1171 int src_cpu, src_nid; 1172 int dst_cpu, dst_nid; 1173 1174 struct numa_stats src_stats, dst_stats; 1175 1176 int imbalance_pct; 1177 int dist; 1178 1179 struct task_struct *best_task; 1180 long best_imp; 1181 int best_cpu; 1182 }; 1183 1184 static void task_numa_assign(struct task_numa_env *env, 1185 struct task_struct *p, long imp) 1186 { 1187 if (env->best_task) 1188 put_task_struct(env->best_task); 1189 if (p) 1190 get_task_struct(p); 1191 1192 env->best_task = p; 1193 env->best_imp = imp; 1194 env->best_cpu = env->dst_cpu; 1195 } 1196 1197 static bool load_too_imbalanced(long src_load, long dst_load, 1198 struct task_numa_env *env) 1199 { 1200 long imb, old_imb; 1201 long orig_src_load, orig_dst_load; 1202 long src_capacity, dst_capacity; 1203 1204 /* 1205 * The load is corrected for the CPU capacity available on each node. 1206 * 1207 * src_load dst_load 1208 * ------------ vs --------- 1209 * src_capacity dst_capacity 1210 */ 1211 src_capacity = env->src_stats.compute_capacity; 1212 dst_capacity = env->dst_stats.compute_capacity; 1213 1214 /* We care about the slope of the imbalance, not the direction. */ 1215 if (dst_load < src_load) 1216 swap(dst_load, src_load); 1217 1218 /* Is the difference below the threshold? */ 1219 imb = dst_load * src_capacity * 100 - 1220 src_load * dst_capacity * env->imbalance_pct; 1221 if (imb <= 0) 1222 return false; 1223 1224 /* 1225 * The imbalance is above the allowed threshold. 1226 * Compare it with the old imbalance. 1227 */ 1228 orig_src_load = env->src_stats.load; 1229 orig_dst_load = env->dst_stats.load; 1230 1231 if (orig_dst_load < orig_src_load) 1232 swap(orig_dst_load, orig_src_load); 1233 1234 old_imb = orig_dst_load * src_capacity * 100 - 1235 orig_src_load * dst_capacity * env->imbalance_pct; 1236 1237 /* Would this change make things worse? */ 1238 return (imb > old_imb); 1239 } 1240 1241 /* 1242 * This checks if the overall compute and NUMA accesses of the system would 1243 * be improved if the source tasks was migrated to the target dst_cpu taking 1244 * into account that it might be best if task running on the dst_cpu should 1245 * be exchanged with the source task 1246 */ 1247 static void task_numa_compare(struct task_numa_env *env, 1248 long taskimp, long groupimp) 1249 { 1250 struct rq *src_rq = cpu_rq(env->src_cpu); 1251 struct rq *dst_rq = cpu_rq(env->dst_cpu); 1252 struct task_struct *cur; 1253 long src_load, dst_load; 1254 long load; 1255 long imp = env->p->numa_group ? groupimp : taskimp; 1256 long moveimp = imp; 1257 int dist = env->dist; 1258 1259 rcu_read_lock(); 1260 1261 raw_spin_lock_irq(&dst_rq->lock); 1262 cur = dst_rq->curr; 1263 /* 1264 * No need to move the exiting task, and this ensures that ->curr 1265 * wasn't reaped and thus get_task_struct() in task_numa_assign() 1266 * is safe under RCU read lock. 1267 * Note that rcu_read_lock() itself can't protect from the final 1268 * put_task_struct() after the last schedule(). 1269 */ 1270 if ((cur->flags & PF_EXITING) || is_idle_task(cur)) 1271 cur = NULL; 1272 raw_spin_unlock_irq(&dst_rq->lock); 1273 1274 /* 1275 * Because we have preemption enabled we can get migrated around and 1276 * end try selecting ourselves (current == env->p) as a swap candidate. 1277 */ 1278 if (cur == env->p) 1279 goto unlock; 1280 1281 /* 1282 * "imp" is the fault differential for the source task between the 1283 * source and destination node. Calculate the total differential for 1284 * the source task and potential destination task. The more negative 1285 * the value is, the more rmeote accesses that would be expected to 1286 * be incurred if the tasks were swapped. 1287 */ 1288 if (cur) { 1289 /* Skip this swap candidate if cannot move to the source cpu */ 1290 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur))) 1291 goto unlock; 1292 1293 /* 1294 * If dst and source tasks are in the same NUMA group, or not 1295 * in any group then look only at task weights. 1296 */ 1297 if (cur->numa_group == env->p->numa_group) { 1298 imp = taskimp + task_weight(cur, env->src_nid, dist) - 1299 task_weight(cur, env->dst_nid, dist); 1300 /* 1301 * Add some hysteresis to prevent swapping the 1302 * tasks within a group over tiny differences. 1303 */ 1304 if (cur->numa_group) 1305 imp -= imp/16; 1306 } else { 1307 /* 1308 * Compare the group weights. If a task is all by 1309 * itself (not part of a group), use the task weight 1310 * instead. 1311 */ 1312 if (cur->numa_group) 1313 imp += group_weight(cur, env->src_nid, dist) - 1314 group_weight(cur, env->dst_nid, dist); 1315 else 1316 imp += task_weight(cur, env->src_nid, dist) - 1317 task_weight(cur, env->dst_nid, dist); 1318 } 1319 } 1320 1321 if (imp <= env->best_imp && moveimp <= env->best_imp) 1322 goto unlock; 1323 1324 if (!cur) { 1325 /* Is there capacity at our destination? */ 1326 if (env->src_stats.nr_running <= env->src_stats.task_capacity && 1327 !env->dst_stats.has_free_capacity) 1328 goto unlock; 1329 1330 goto balance; 1331 } 1332 1333 /* Balance doesn't matter much if we're running a task per cpu */ 1334 if (imp > env->best_imp && src_rq->nr_running == 1 && 1335 dst_rq->nr_running == 1) 1336 goto assign; 1337 1338 /* 1339 * In the overloaded case, try and keep the load balanced. 1340 */ 1341 balance: 1342 load = task_h_load(env->p); 1343 dst_load = env->dst_stats.load + load; 1344 src_load = env->src_stats.load - load; 1345 1346 if (moveimp > imp && moveimp > env->best_imp) { 1347 /* 1348 * If the improvement from just moving env->p direction is 1349 * better than swapping tasks around, check if a move is 1350 * possible. Store a slightly smaller score than moveimp, 1351 * so an actually idle CPU will win. 1352 */ 1353 if (!load_too_imbalanced(src_load, dst_load, env)) { 1354 imp = moveimp - 1; 1355 cur = NULL; 1356 goto assign; 1357 } 1358 } 1359 1360 if (imp <= env->best_imp) 1361 goto unlock; 1362 1363 if (cur) { 1364 load = task_h_load(cur); 1365 dst_load -= load; 1366 src_load += load; 1367 } 1368 1369 if (load_too_imbalanced(src_load, dst_load, env)) 1370 goto unlock; 1371 1372 /* 1373 * One idle CPU per node is evaluated for a task numa move. 1374 * Call select_idle_sibling to maybe find a better one. 1375 */ 1376 if (!cur) 1377 env->dst_cpu = select_idle_sibling(env->p, env->dst_cpu); 1378 1379 assign: 1380 task_numa_assign(env, cur, imp); 1381 unlock: 1382 rcu_read_unlock(); 1383 } 1384 1385 static void task_numa_find_cpu(struct task_numa_env *env, 1386 long taskimp, long groupimp) 1387 { 1388 int cpu; 1389 1390 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { 1391 /* Skip this CPU if the source task cannot migrate */ 1392 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p))) 1393 continue; 1394 1395 env->dst_cpu = cpu; 1396 task_numa_compare(env, taskimp, groupimp); 1397 } 1398 } 1399 1400 static int task_numa_migrate(struct task_struct *p) 1401 { 1402 struct task_numa_env env = { 1403 .p = p, 1404 1405 .src_cpu = task_cpu(p), 1406 .src_nid = task_node(p), 1407 1408 .imbalance_pct = 112, 1409 1410 .best_task = NULL, 1411 .best_imp = 0, 1412 .best_cpu = -1 1413 }; 1414 struct sched_domain *sd; 1415 unsigned long taskweight, groupweight; 1416 int nid, ret, dist; 1417 long taskimp, groupimp; 1418 1419 /* 1420 * Pick the lowest SD_NUMA domain, as that would have the smallest 1421 * imbalance and would be the first to start moving tasks about. 1422 * 1423 * And we want to avoid any moving of tasks about, as that would create 1424 * random movement of tasks -- counter the numa conditions we're trying 1425 * to satisfy here. 1426 */ 1427 rcu_read_lock(); 1428 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); 1429 if (sd) 1430 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; 1431 rcu_read_unlock(); 1432 1433 /* 1434 * Cpusets can break the scheduler domain tree into smaller 1435 * balance domains, some of which do not cross NUMA boundaries. 1436 * Tasks that are "trapped" in such domains cannot be migrated 1437 * elsewhere, so there is no point in (re)trying. 1438 */ 1439 if (unlikely(!sd)) { 1440 p->numa_preferred_nid = task_node(p); 1441 return -EINVAL; 1442 } 1443 1444 env.dst_nid = p->numa_preferred_nid; 1445 dist = env.dist = node_distance(env.src_nid, env.dst_nid); 1446 taskweight = task_weight(p, env.src_nid, dist); 1447 groupweight = group_weight(p, env.src_nid, dist); 1448 update_numa_stats(&env.src_stats, env.src_nid); 1449 taskimp = task_weight(p, env.dst_nid, dist) - taskweight; 1450 groupimp = group_weight(p, env.dst_nid, dist) - groupweight; 1451 update_numa_stats(&env.dst_stats, env.dst_nid); 1452 1453 /* Try to find a spot on the preferred nid. */ 1454 task_numa_find_cpu(&env, taskimp, groupimp); 1455 1456 /* 1457 * Look at other nodes in these cases: 1458 * - there is no space available on the preferred_nid 1459 * - the task is part of a numa_group that is interleaved across 1460 * multiple NUMA nodes; in order to better consolidate the group, 1461 * we need to check other locations. 1462 */ 1463 if (env.best_cpu == -1 || (p->numa_group && 1464 nodes_weight(p->numa_group->active_nodes) > 1)) { 1465 for_each_online_node(nid) { 1466 if (nid == env.src_nid || nid == p->numa_preferred_nid) 1467 continue; 1468 1469 dist = node_distance(env.src_nid, env.dst_nid); 1470 if (sched_numa_topology_type == NUMA_BACKPLANE && 1471 dist != env.dist) { 1472 taskweight = task_weight(p, env.src_nid, dist); 1473 groupweight = group_weight(p, env.src_nid, dist); 1474 } 1475 1476 /* Only consider nodes where both task and groups benefit */ 1477 taskimp = task_weight(p, nid, dist) - taskweight; 1478 groupimp = group_weight(p, nid, dist) - groupweight; 1479 if (taskimp < 0 && groupimp < 0) 1480 continue; 1481 1482 env.dist = dist; 1483 env.dst_nid = nid; 1484 update_numa_stats(&env.dst_stats, env.dst_nid); 1485 task_numa_find_cpu(&env, taskimp, groupimp); 1486 } 1487 } 1488 1489 /* 1490 * If the task is part of a workload that spans multiple NUMA nodes, 1491 * and is migrating into one of the workload's active nodes, remember 1492 * this node as the task's preferred numa node, so the workload can 1493 * settle down. 1494 * A task that migrated to a second choice node will be better off 1495 * trying for a better one later. Do not set the preferred node here. 1496 */ 1497 if (p->numa_group) { 1498 if (env.best_cpu == -1) 1499 nid = env.src_nid; 1500 else 1501 nid = env.dst_nid; 1502 1503 if (node_isset(nid, p->numa_group->active_nodes)) 1504 sched_setnuma(p, env.dst_nid); 1505 } 1506 1507 /* No better CPU than the current one was found. */ 1508 if (env.best_cpu == -1) 1509 return -EAGAIN; 1510 1511 /* 1512 * Reset the scan period if the task is being rescheduled on an 1513 * alternative node to recheck if the tasks is now properly placed. 1514 */ 1515 p->numa_scan_period = task_scan_min(p); 1516 1517 if (env.best_task == NULL) { 1518 ret = migrate_task_to(p, env.best_cpu); 1519 if (ret != 0) 1520 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); 1521 return ret; 1522 } 1523 1524 ret = migrate_swap(p, env.best_task); 1525 if (ret != 0) 1526 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); 1527 put_task_struct(env.best_task); 1528 return ret; 1529 } 1530 1531 /* Attempt to migrate a task to a CPU on the preferred node. */ 1532 static void numa_migrate_preferred(struct task_struct *p) 1533 { 1534 unsigned long interval = HZ; 1535 1536 /* This task has no NUMA fault statistics yet */ 1537 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults)) 1538 return; 1539 1540 /* Periodically retry migrating the task to the preferred node */ 1541 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); 1542 p->numa_migrate_retry = jiffies + interval; 1543 1544 /* Success if task is already running on preferred CPU */ 1545 if (task_node(p) == p->numa_preferred_nid) 1546 return; 1547 1548 /* Otherwise, try migrate to a CPU on the preferred node */ 1549 task_numa_migrate(p); 1550 } 1551 1552 /* 1553 * Find the nodes on which the workload is actively running. We do this by 1554 * tracking the nodes from which NUMA hinting faults are triggered. This can 1555 * be different from the set of nodes where the workload's memory is currently 1556 * located. 1557 * 1558 * The bitmask is used to make smarter decisions on when to do NUMA page 1559 * migrations, To prevent flip-flopping, and excessive page migrations, nodes 1560 * are added when they cause over 6/16 of the maximum number of faults, but 1561 * only removed when they drop below 3/16. 1562 */ 1563 static void update_numa_active_node_mask(struct numa_group *numa_group) 1564 { 1565 unsigned long faults, max_faults = 0; 1566 int nid; 1567 1568 for_each_online_node(nid) { 1569 faults = group_faults_cpu(numa_group, nid); 1570 if (faults > max_faults) 1571 max_faults = faults; 1572 } 1573 1574 for_each_online_node(nid) { 1575 faults = group_faults_cpu(numa_group, nid); 1576 if (!node_isset(nid, numa_group->active_nodes)) { 1577 if (faults > max_faults * 6 / 16) 1578 node_set(nid, numa_group->active_nodes); 1579 } else if (faults < max_faults * 3 / 16) 1580 node_clear(nid, numa_group->active_nodes); 1581 } 1582 } 1583 1584 /* 1585 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS 1586 * increments. The more local the fault statistics are, the higher the scan 1587 * period will be for the next scan window. If local/(local+remote) ratio is 1588 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) 1589 * the scan period will decrease. Aim for 70% local accesses. 1590 */ 1591 #define NUMA_PERIOD_SLOTS 10 1592 #define NUMA_PERIOD_THRESHOLD 7 1593 1594 /* 1595 * Increase the scan period (slow down scanning) if the majority of 1596 * our memory is already on our local node, or if the majority of 1597 * the page accesses are shared with other processes. 1598 * Otherwise, decrease the scan period. 1599 */ 1600 static void update_task_scan_period(struct task_struct *p, 1601 unsigned long shared, unsigned long private) 1602 { 1603 unsigned int period_slot; 1604 int ratio; 1605 int diff; 1606 1607 unsigned long remote = p->numa_faults_locality[0]; 1608 unsigned long local = p->numa_faults_locality[1]; 1609 1610 /* 1611 * If there were no record hinting faults then either the task is 1612 * completely idle or all activity is areas that are not of interest 1613 * to automatic numa balancing. Scan slower 1614 */ 1615 if (local + shared == 0) { 1616 p->numa_scan_period = min(p->numa_scan_period_max, 1617 p->numa_scan_period << 1); 1618 1619 p->mm->numa_next_scan = jiffies + 1620 msecs_to_jiffies(p->numa_scan_period); 1621 1622 return; 1623 } 1624 1625 /* 1626 * Prepare to scale scan period relative to the current period. 1627 * == NUMA_PERIOD_THRESHOLD scan period stays the same 1628 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) 1629 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) 1630 */ 1631 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); 1632 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); 1633 if (ratio >= NUMA_PERIOD_THRESHOLD) { 1634 int slot = ratio - NUMA_PERIOD_THRESHOLD; 1635 if (!slot) 1636 slot = 1; 1637 diff = slot * period_slot; 1638 } else { 1639 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; 1640 1641 /* 1642 * Scale scan rate increases based on sharing. There is an 1643 * inverse relationship between the degree of sharing and 1644 * the adjustment made to the scanning period. Broadly 1645 * speaking the intent is that there is little point 1646 * scanning faster if shared accesses dominate as it may 1647 * simply bounce migrations uselessly 1648 */ 1649 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1)); 1650 diff = (diff * ratio) / NUMA_PERIOD_SLOTS; 1651 } 1652 1653 p->numa_scan_period = clamp(p->numa_scan_period + diff, 1654 task_scan_min(p), task_scan_max(p)); 1655 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 1656 } 1657 1658 /* 1659 * Get the fraction of time the task has been running since the last 1660 * NUMA placement cycle. The scheduler keeps similar statistics, but 1661 * decays those on a 32ms period, which is orders of magnitude off 1662 * from the dozens-of-seconds NUMA balancing period. Use the scheduler 1663 * stats only if the task is so new there are no NUMA statistics yet. 1664 */ 1665 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) 1666 { 1667 u64 runtime, delta, now; 1668 /* Use the start of this time slice to avoid calculations. */ 1669 now = p->se.exec_start; 1670 runtime = p->se.sum_exec_runtime; 1671 1672 if (p->last_task_numa_placement) { 1673 delta = runtime - p->last_sum_exec_runtime; 1674 *period = now - p->last_task_numa_placement; 1675 } else { 1676 delta = p->se.avg.runnable_avg_sum; 1677 *period = p->se.avg.runnable_avg_period; 1678 } 1679 1680 p->last_sum_exec_runtime = runtime; 1681 p->last_task_numa_placement = now; 1682 1683 return delta; 1684 } 1685 1686 /* 1687 * Determine the preferred nid for a task in a numa_group. This needs to 1688 * be done in a way that produces consistent results with group_weight, 1689 * otherwise workloads might not converge. 1690 */ 1691 static int preferred_group_nid(struct task_struct *p, int nid) 1692 { 1693 nodemask_t nodes; 1694 int dist; 1695 1696 /* Direct connections between all NUMA nodes. */ 1697 if (sched_numa_topology_type == NUMA_DIRECT) 1698 return nid; 1699 1700 /* 1701 * On a system with glueless mesh NUMA topology, group_weight 1702 * scores nodes according to the number of NUMA hinting faults on 1703 * both the node itself, and on nearby nodes. 1704 */ 1705 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { 1706 unsigned long score, max_score = 0; 1707 int node, max_node = nid; 1708 1709 dist = sched_max_numa_distance; 1710 1711 for_each_online_node(node) { 1712 score = group_weight(p, node, dist); 1713 if (score > max_score) { 1714 max_score = score; 1715 max_node = node; 1716 } 1717 } 1718 return max_node; 1719 } 1720 1721 /* 1722 * Finding the preferred nid in a system with NUMA backplane 1723 * interconnect topology is more involved. The goal is to locate 1724 * tasks from numa_groups near each other in the system, and 1725 * untangle workloads from different sides of the system. This requires 1726 * searching down the hierarchy of node groups, recursively searching 1727 * inside the highest scoring group of nodes. The nodemask tricks 1728 * keep the complexity of the search down. 1729 */ 1730 nodes = node_online_map; 1731 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { 1732 unsigned long max_faults = 0; 1733 nodemask_t max_group; 1734 int a, b; 1735 1736 /* Are there nodes at this distance from each other? */ 1737 if (!find_numa_distance(dist)) 1738 continue; 1739 1740 for_each_node_mask(a, nodes) { 1741 unsigned long faults = 0; 1742 nodemask_t this_group; 1743 nodes_clear(this_group); 1744 1745 /* Sum group's NUMA faults; includes a==b case. */ 1746 for_each_node_mask(b, nodes) { 1747 if (node_distance(a, b) < dist) { 1748 faults += group_faults(p, b); 1749 node_set(b, this_group); 1750 node_clear(b, nodes); 1751 } 1752 } 1753 1754 /* Remember the top group. */ 1755 if (faults > max_faults) { 1756 max_faults = faults; 1757 max_group = this_group; 1758 /* 1759 * subtle: at the smallest distance there is 1760 * just one node left in each "group", the 1761 * winner is the preferred nid. 1762 */ 1763 nid = a; 1764 } 1765 } 1766 /* Next round, evaluate the nodes within max_group. */ 1767 nodes = max_group; 1768 } 1769 return nid; 1770 } 1771 1772 static void task_numa_placement(struct task_struct *p) 1773 { 1774 int seq, nid, max_nid = -1, max_group_nid = -1; 1775 unsigned long max_faults = 0, max_group_faults = 0; 1776 unsigned long fault_types[2] = { 0, 0 }; 1777 unsigned long total_faults; 1778 u64 runtime, period; 1779 spinlock_t *group_lock = NULL; 1780 1781 seq = ACCESS_ONCE(p->mm->numa_scan_seq); 1782 if (p->numa_scan_seq == seq) 1783 return; 1784 p->numa_scan_seq = seq; 1785 p->numa_scan_period_max = task_scan_max(p); 1786 1787 total_faults = p->numa_faults_locality[0] + 1788 p->numa_faults_locality[1]; 1789 runtime = numa_get_avg_runtime(p, &period); 1790 1791 /* If the task is part of a group prevent parallel updates to group stats */ 1792 if (p->numa_group) { 1793 group_lock = &p->numa_group->lock; 1794 spin_lock_irq(group_lock); 1795 } 1796 1797 /* Find the node with the highest number of faults */ 1798 for_each_online_node(nid) { 1799 /* Keep track of the offsets in numa_faults array */ 1800 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx; 1801 unsigned long faults = 0, group_faults = 0; 1802 int priv; 1803 1804 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { 1805 long diff, f_diff, f_weight; 1806 1807 mem_idx = task_faults_idx(NUMA_MEM, nid, priv); 1808 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv); 1809 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv); 1810 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv); 1811 1812 /* Decay existing window, copy faults since last scan */ 1813 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2; 1814 fault_types[priv] += p->numa_faults[membuf_idx]; 1815 p->numa_faults[membuf_idx] = 0; 1816 1817 /* 1818 * Normalize the faults_from, so all tasks in a group 1819 * count according to CPU use, instead of by the raw 1820 * number of faults. Tasks with little runtime have 1821 * little over-all impact on throughput, and thus their 1822 * faults are less important. 1823 */ 1824 f_weight = div64_u64(runtime << 16, period + 1); 1825 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / 1826 (total_faults + 1); 1827 f_diff = f_weight - p->numa_faults[cpu_idx] / 2; 1828 p->numa_faults[cpubuf_idx] = 0; 1829 1830 p->numa_faults[mem_idx] += diff; 1831 p->numa_faults[cpu_idx] += f_diff; 1832 faults += p->numa_faults[mem_idx]; 1833 p->total_numa_faults += diff; 1834 if (p->numa_group) { 1835 /* 1836 * safe because we can only change our own group 1837 * 1838 * mem_idx represents the offset for a given 1839 * nid and priv in a specific region because it 1840 * is at the beginning of the numa_faults array. 1841 */ 1842 p->numa_group->faults[mem_idx] += diff; 1843 p->numa_group->faults_cpu[mem_idx] += f_diff; 1844 p->numa_group->total_faults += diff; 1845 group_faults += p->numa_group->faults[mem_idx]; 1846 } 1847 } 1848 1849 if (faults > max_faults) { 1850 max_faults = faults; 1851 max_nid = nid; 1852 } 1853 1854 if (group_faults > max_group_faults) { 1855 max_group_faults = group_faults; 1856 max_group_nid = nid; 1857 } 1858 } 1859 1860 update_task_scan_period(p, fault_types[0], fault_types[1]); 1861 1862 if (p->numa_group) { 1863 update_numa_active_node_mask(p->numa_group); 1864 spin_unlock_irq(group_lock); 1865 max_nid = preferred_group_nid(p, max_group_nid); 1866 } 1867 1868 if (max_faults) { 1869 /* Set the new preferred node */ 1870 if (max_nid != p->numa_preferred_nid) 1871 sched_setnuma(p, max_nid); 1872 1873 if (task_node(p) != p->numa_preferred_nid) 1874 numa_migrate_preferred(p); 1875 } 1876 } 1877 1878 static inline int get_numa_group(struct numa_group *grp) 1879 { 1880 return atomic_inc_not_zero(&grp->refcount); 1881 } 1882 1883 static inline void put_numa_group(struct numa_group *grp) 1884 { 1885 if (atomic_dec_and_test(&grp->refcount)) 1886 kfree_rcu(grp, rcu); 1887 } 1888 1889 static void task_numa_group(struct task_struct *p, int cpupid, int flags, 1890 int *priv) 1891 { 1892 struct numa_group *grp, *my_grp; 1893 struct task_struct *tsk; 1894 bool join = false; 1895 int cpu = cpupid_to_cpu(cpupid); 1896 int i; 1897 1898 if (unlikely(!p->numa_group)) { 1899 unsigned int size = sizeof(struct numa_group) + 1900 4*nr_node_ids*sizeof(unsigned long); 1901 1902 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); 1903 if (!grp) 1904 return; 1905 1906 atomic_set(&grp->refcount, 1); 1907 spin_lock_init(&grp->lock); 1908 grp->gid = p->pid; 1909 /* Second half of the array tracks nids where faults happen */ 1910 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * 1911 nr_node_ids; 1912 1913 node_set(task_node(current), grp->active_nodes); 1914 1915 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 1916 grp->faults[i] = p->numa_faults[i]; 1917 1918 grp->total_faults = p->total_numa_faults; 1919 1920 grp->nr_tasks++; 1921 rcu_assign_pointer(p->numa_group, grp); 1922 } 1923 1924 rcu_read_lock(); 1925 tsk = ACCESS_ONCE(cpu_rq(cpu)->curr); 1926 1927 if (!cpupid_match_pid(tsk, cpupid)) 1928 goto no_join; 1929 1930 grp = rcu_dereference(tsk->numa_group); 1931 if (!grp) 1932 goto no_join; 1933 1934 my_grp = p->numa_group; 1935 if (grp == my_grp) 1936 goto no_join; 1937 1938 /* 1939 * Only join the other group if its bigger; if we're the bigger group, 1940 * the other task will join us. 1941 */ 1942 if (my_grp->nr_tasks > grp->nr_tasks) 1943 goto no_join; 1944 1945 /* 1946 * Tie-break on the grp address. 1947 */ 1948 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) 1949 goto no_join; 1950 1951 /* Always join threads in the same process. */ 1952 if (tsk->mm == current->mm) 1953 join = true; 1954 1955 /* Simple filter to avoid false positives due to PID collisions */ 1956 if (flags & TNF_SHARED) 1957 join = true; 1958 1959 /* Update priv based on whether false sharing was detected */ 1960 *priv = !join; 1961 1962 if (join && !get_numa_group(grp)) 1963 goto no_join; 1964 1965 rcu_read_unlock(); 1966 1967 if (!join) 1968 return; 1969 1970 BUG_ON(irqs_disabled()); 1971 double_lock_irq(&my_grp->lock, &grp->lock); 1972 1973 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { 1974 my_grp->faults[i] -= p->numa_faults[i]; 1975 grp->faults[i] += p->numa_faults[i]; 1976 } 1977 my_grp->total_faults -= p->total_numa_faults; 1978 grp->total_faults += p->total_numa_faults; 1979 1980 my_grp->nr_tasks--; 1981 grp->nr_tasks++; 1982 1983 spin_unlock(&my_grp->lock); 1984 spin_unlock_irq(&grp->lock); 1985 1986 rcu_assign_pointer(p->numa_group, grp); 1987 1988 put_numa_group(my_grp); 1989 return; 1990 1991 no_join: 1992 rcu_read_unlock(); 1993 return; 1994 } 1995 1996 void task_numa_free(struct task_struct *p) 1997 { 1998 struct numa_group *grp = p->numa_group; 1999 void *numa_faults = p->numa_faults; 2000 unsigned long flags; 2001 int i; 2002 2003 if (grp) { 2004 spin_lock_irqsave(&grp->lock, flags); 2005 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 2006 grp->faults[i] -= p->numa_faults[i]; 2007 grp->total_faults -= p->total_numa_faults; 2008 2009 grp->nr_tasks--; 2010 spin_unlock_irqrestore(&grp->lock, flags); 2011 RCU_INIT_POINTER(p->numa_group, NULL); 2012 put_numa_group(grp); 2013 } 2014 2015 p->numa_faults = NULL; 2016 kfree(numa_faults); 2017 } 2018 2019 /* 2020 * Got a PROT_NONE fault for a page on @node. 2021 */ 2022 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) 2023 { 2024 struct task_struct *p = current; 2025 bool migrated = flags & TNF_MIGRATED; 2026 int cpu_node = task_node(current); 2027 int local = !!(flags & TNF_FAULT_LOCAL); 2028 int priv; 2029 2030 if (!numabalancing_enabled) 2031 return; 2032 2033 /* for example, ksmd faulting in a user's mm */ 2034 if (!p->mm) 2035 return; 2036 2037 /* Allocate buffer to track faults on a per-node basis */ 2038 if (unlikely(!p->numa_faults)) { 2039 int size = sizeof(*p->numa_faults) * 2040 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; 2041 2042 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); 2043 if (!p->numa_faults) 2044 return; 2045 2046 p->total_numa_faults = 0; 2047 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 2048 } 2049 2050 /* 2051 * First accesses are treated as private, otherwise consider accesses 2052 * to be private if the accessing pid has not changed 2053 */ 2054 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { 2055 priv = 1; 2056 } else { 2057 priv = cpupid_match_pid(p, last_cpupid); 2058 if (!priv && !(flags & TNF_NO_GROUP)) 2059 task_numa_group(p, last_cpupid, flags, &priv); 2060 } 2061 2062 /* 2063 * If a workload spans multiple NUMA nodes, a shared fault that 2064 * occurs wholly within the set of nodes that the workload is 2065 * actively using should be counted as local. This allows the 2066 * scan rate to slow down when a workload has settled down. 2067 */ 2068 if (!priv && !local && p->numa_group && 2069 node_isset(cpu_node, p->numa_group->active_nodes) && 2070 node_isset(mem_node, p->numa_group->active_nodes)) 2071 local = 1; 2072 2073 task_numa_placement(p); 2074 2075 /* 2076 * Retry task to preferred node migration periodically, in case it 2077 * case it previously failed, or the scheduler moved us. 2078 */ 2079 if (time_after(jiffies, p->numa_migrate_retry)) 2080 numa_migrate_preferred(p); 2081 2082 if (migrated) 2083 p->numa_pages_migrated += pages; 2084 2085 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages; 2086 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages; 2087 p->numa_faults_locality[local] += pages; 2088 } 2089 2090 static void reset_ptenuma_scan(struct task_struct *p) 2091 { 2092 ACCESS_ONCE(p->mm->numa_scan_seq)++; 2093 p->mm->numa_scan_offset = 0; 2094 } 2095 2096 /* 2097 * The expensive part of numa migration is done from task_work context. 2098 * Triggered from task_tick_numa(). 2099 */ 2100 void task_numa_work(struct callback_head *work) 2101 { 2102 unsigned long migrate, next_scan, now = jiffies; 2103 struct task_struct *p = current; 2104 struct mm_struct *mm = p->mm; 2105 struct vm_area_struct *vma; 2106 unsigned long start, end; 2107 unsigned long nr_pte_updates = 0; 2108 long pages; 2109 2110 WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work)); 2111 2112 work->next = work; /* protect against double add */ 2113 /* 2114 * Who cares about NUMA placement when they're dying. 2115 * 2116 * NOTE: make sure not to dereference p->mm before this check, 2117 * exit_task_work() happens _after_ exit_mm() so we could be called 2118 * without p->mm even though we still had it when we enqueued this 2119 * work. 2120 */ 2121 if (p->flags & PF_EXITING) 2122 return; 2123 2124 if (!mm->numa_next_scan) { 2125 mm->numa_next_scan = now + 2126 msecs_to_jiffies(sysctl_numa_balancing_scan_delay); 2127 } 2128 2129 /* 2130 * Enforce maximal scan/migration frequency.. 2131 */ 2132 migrate = mm->numa_next_scan; 2133 if (time_before(now, migrate)) 2134 return; 2135 2136 if (p->numa_scan_period == 0) { 2137 p->numa_scan_period_max = task_scan_max(p); 2138 p->numa_scan_period = task_scan_min(p); 2139 } 2140 2141 next_scan = now + msecs_to_jiffies(p->numa_scan_period); 2142 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) 2143 return; 2144 2145 /* 2146 * Delay this task enough that another task of this mm will likely win 2147 * the next time around. 2148 */ 2149 p->node_stamp += 2 * TICK_NSEC; 2150 2151 start = mm->numa_scan_offset; 2152 pages = sysctl_numa_balancing_scan_size; 2153 pages <<= 20 - PAGE_SHIFT; /* MB in pages */ 2154 if (!pages) 2155 return; 2156 2157 down_read(&mm->mmap_sem); 2158 vma = find_vma(mm, start); 2159 if (!vma) { 2160 reset_ptenuma_scan(p); 2161 start = 0; 2162 vma = mm->mmap; 2163 } 2164 for (; vma; vma = vma->vm_next) { 2165 if (!vma_migratable(vma) || !vma_policy_mof(vma)) 2166 continue; 2167 2168 /* 2169 * Shared library pages mapped by multiple processes are not 2170 * migrated as it is expected they are cache replicated. Avoid 2171 * hinting faults in read-only file-backed mappings or the vdso 2172 * as migrating the pages will be of marginal benefit. 2173 */ 2174 if (!vma->vm_mm || 2175 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) 2176 continue; 2177 2178 /* 2179 * Skip inaccessible VMAs to avoid any confusion between 2180 * PROT_NONE and NUMA hinting ptes 2181 */ 2182 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 2183 continue; 2184 2185 do { 2186 start = max(start, vma->vm_start); 2187 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); 2188 end = min(end, vma->vm_end); 2189 nr_pte_updates += change_prot_numa(vma, start, end); 2190 2191 /* 2192 * Scan sysctl_numa_balancing_scan_size but ensure that 2193 * at least one PTE is updated so that unused virtual 2194 * address space is quickly skipped. 2195 */ 2196 if (nr_pte_updates) 2197 pages -= (end - start) >> PAGE_SHIFT; 2198 2199 start = end; 2200 if (pages <= 0) 2201 goto out; 2202 2203 cond_resched(); 2204 } while (end != vma->vm_end); 2205 } 2206 2207 out: 2208 /* 2209 * It is possible to reach the end of the VMA list but the last few 2210 * VMAs are not guaranteed to the vma_migratable. If they are not, we 2211 * would find the !migratable VMA on the next scan but not reset the 2212 * scanner to the start so check it now. 2213 */ 2214 if (vma) 2215 mm->numa_scan_offset = start; 2216 else 2217 reset_ptenuma_scan(p); 2218 up_read(&mm->mmap_sem); 2219 } 2220 2221 /* 2222 * Drive the periodic memory faults.. 2223 */ 2224 void task_tick_numa(struct rq *rq, struct task_struct *curr) 2225 { 2226 struct callback_head *work = &curr->numa_work; 2227 u64 period, now; 2228 2229 /* 2230 * We don't care about NUMA placement if we don't have memory. 2231 */ 2232 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) 2233 return; 2234 2235 /* 2236 * Using runtime rather than walltime has the dual advantage that 2237 * we (mostly) drive the selection from busy threads and that the 2238 * task needs to have done some actual work before we bother with 2239 * NUMA placement. 2240 */ 2241 now = curr->se.sum_exec_runtime; 2242 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; 2243 2244 if (now - curr->node_stamp > period) { 2245 if (!curr->node_stamp) 2246 curr->numa_scan_period = task_scan_min(curr); 2247 curr->node_stamp += period; 2248 2249 if (!time_before(jiffies, curr->mm->numa_next_scan)) { 2250 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ 2251 task_work_add(curr, work, true); 2252 } 2253 } 2254 } 2255 #else 2256 static void task_tick_numa(struct rq *rq, struct task_struct *curr) 2257 { 2258 } 2259 2260 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) 2261 { 2262 } 2263 2264 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) 2265 { 2266 } 2267 #endif /* CONFIG_NUMA_BALANCING */ 2268 2269 static void 2270 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2271 { 2272 update_load_add(&cfs_rq->load, se->load.weight); 2273 if (!parent_entity(se)) 2274 update_load_add(&rq_of(cfs_rq)->load, se->load.weight); 2275 #ifdef CONFIG_SMP 2276 if (entity_is_task(se)) { 2277 struct rq *rq = rq_of(cfs_rq); 2278 2279 account_numa_enqueue(rq, task_of(se)); 2280 list_add(&se->group_node, &rq->cfs_tasks); 2281 } 2282 #endif 2283 cfs_rq->nr_running++; 2284 } 2285 2286 static void 2287 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2288 { 2289 update_load_sub(&cfs_rq->load, se->load.weight); 2290 if (!parent_entity(se)) 2291 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight); 2292 if (entity_is_task(se)) { 2293 account_numa_dequeue(rq_of(cfs_rq), task_of(se)); 2294 list_del_init(&se->group_node); 2295 } 2296 cfs_rq->nr_running--; 2297 } 2298 2299 #ifdef CONFIG_FAIR_GROUP_SCHED 2300 # ifdef CONFIG_SMP 2301 static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq) 2302 { 2303 long tg_weight; 2304 2305 /* 2306 * Use this CPU's actual weight instead of the last load_contribution 2307 * to gain a more accurate current total weight. See 2308 * update_cfs_rq_load_contribution(). 2309 */ 2310 tg_weight = atomic_long_read(&tg->load_avg); 2311 tg_weight -= cfs_rq->tg_load_contrib; 2312 tg_weight += cfs_rq->load.weight; 2313 2314 return tg_weight; 2315 } 2316 2317 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2318 { 2319 long tg_weight, load, shares; 2320 2321 tg_weight = calc_tg_weight(tg, cfs_rq); 2322 load = cfs_rq->load.weight; 2323 2324 shares = (tg->shares * load); 2325 if (tg_weight) 2326 shares /= tg_weight; 2327 2328 if (shares < MIN_SHARES) 2329 shares = MIN_SHARES; 2330 if (shares > tg->shares) 2331 shares = tg->shares; 2332 2333 return shares; 2334 } 2335 # else /* CONFIG_SMP */ 2336 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2337 { 2338 return tg->shares; 2339 } 2340 # endif /* CONFIG_SMP */ 2341 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, 2342 unsigned long weight) 2343 { 2344 if (se->on_rq) { 2345 /* commit outstanding execution time */ 2346 if (cfs_rq->curr == se) 2347 update_curr(cfs_rq); 2348 account_entity_dequeue(cfs_rq, se); 2349 } 2350 2351 update_load_set(&se->load, weight); 2352 2353 if (se->on_rq) 2354 account_entity_enqueue(cfs_rq, se); 2355 } 2356 2357 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); 2358 2359 static void update_cfs_shares(struct cfs_rq *cfs_rq) 2360 { 2361 struct task_group *tg; 2362 struct sched_entity *se; 2363 long shares; 2364 2365 tg = cfs_rq->tg; 2366 se = tg->se[cpu_of(rq_of(cfs_rq))]; 2367 if (!se || throttled_hierarchy(cfs_rq)) 2368 return; 2369 #ifndef CONFIG_SMP 2370 if (likely(se->load.weight == tg->shares)) 2371 return; 2372 #endif 2373 shares = calc_cfs_shares(cfs_rq, tg); 2374 2375 reweight_entity(cfs_rq_of(se), se, shares); 2376 } 2377 #else /* CONFIG_FAIR_GROUP_SCHED */ 2378 static inline void update_cfs_shares(struct cfs_rq *cfs_rq) 2379 { 2380 } 2381 #endif /* CONFIG_FAIR_GROUP_SCHED */ 2382 2383 #ifdef CONFIG_SMP 2384 /* 2385 * We choose a half-life close to 1 scheduling period. 2386 * Note: The tables below are dependent on this value. 2387 */ 2388 #define LOAD_AVG_PERIOD 32 2389 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */ 2390 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */ 2391 2392 /* Precomputed fixed inverse multiplies for multiplication by y^n */ 2393 static const u32 runnable_avg_yN_inv[] = { 2394 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6, 2395 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85, 2396 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581, 2397 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9, 2398 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80, 2399 0x85aac367, 0x82cd8698, 2400 }; 2401 2402 /* 2403 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent 2404 * over-estimates when re-combining. 2405 */ 2406 static const u32 runnable_avg_yN_sum[] = { 2407 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103, 2408 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082, 2409 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371, 2410 }; 2411 2412 /* 2413 * Approximate: 2414 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period) 2415 */ 2416 static __always_inline u64 decay_load(u64 val, u64 n) 2417 { 2418 unsigned int local_n; 2419 2420 if (!n) 2421 return val; 2422 else if (unlikely(n > LOAD_AVG_PERIOD * 63)) 2423 return 0; 2424 2425 /* after bounds checking we can collapse to 32-bit */ 2426 local_n = n; 2427 2428 /* 2429 * As y^PERIOD = 1/2, we can combine 2430 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD) 2431 * With a look-up table which covers y^n (n<PERIOD) 2432 * 2433 * To achieve constant time decay_load. 2434 */ 2435 if (unlikely(local_n >= LOAD_AVG_PERIOD)) { 2436 val >>= local_n / LOAD_AVG_PERIOD; 2437 local_n %= LOAD_AVG_PERIOD; 2438 } 2439 2440 val *= runnable_avg_yN_inv[local_n]; 2441 /* We don't use SRR here since we always want to round down. */ 2442 return val >> 32; 2443 } 2444 2445 /* 2446 * For updates fully spanning n periods, the contribution to runnable 2447 * average will be: \Sum 1024*y^n 2448 * 2449 * We can compute this reasonably efficiently by combining: 2450 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD} 2451 */ 2452 static u32 __compute_runnable_contrib(u64 n) 2453 { 2454 u32 contrib = 0; 2455 2456 if (likely(n <= LOAD_AVG_PERIOD)) 2457 return runnable_avg_yN_sum[n]; 2458 else if (unlikely(n >= LOAD_AVG_MAX_N)) 2459 return LOAD_AVG_MAX; 2460 2461 /* Compute \Sum k^n combining precomputed values for k^i, \Sum k^j */ 2462 do { 2463 contrib /= 2; /* y^LOAD_AVG_PERIOD = 1/2 */ 2464 contrib += runnable_avg_yN_sum[LOAD_AVG_PERIOD]; 2465 2466 n -= LOAD_AVG_PERIOD; 2467 } while (n > LOAD_AVG_PERIOD); 2468 2469 contrib = decay_load(contrib, n); 2470 return contrib + runnable_avg_yN_sum[n]; 2471 } 2472 2473 /* 2474 * We can represent the historical contribution to runnable average as the 2475 * coefficients of a geometric series. To do this we sub-divide our runnable 2476 * history into segments of approximately 1ms (1024us); label the segment that 2477 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g. 2478 * 2479 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ... 2480 * p0 p1 p2 2481 * (now) (~1ms ago) (~2ms ago) 2482 * 2483 * Let u_i denote the fraction of p_i that the entity was runnable. 2484 * 2485 * We then designate the fractions u_i as our co-efficients, yielding the 2486 * following representation of historical load: 2487 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ... 2488 * 2489 * We choose y based on the with of a reasonably scheduling period, fixing: 2490 * y^32 = 0.5 2491 * 2492 * This means that the contribution to load ~32ms ago (u_32) will be weighted 2493 * approximately half as much as the contribution to load within the last ms 2494 * (u_0). 2495 * 2496 * When a period "rolls over" and we have new u_0`, multiplying the previous 2497 * sum again by y is sufficient to update: 2498 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) 2499 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] 2500 */ 2501 static __always_inline int __update_entity_runnable_avg(u64 now, 2502 struct sched_avg *sa, 2503 int runnable) 2504 { 2505 u64 delta, periods; 2506 u32 runnable_contrib; 2507 int delta_w, decayed = 0; 2508 2509 delta = now - sa->last_runnable_update; 2510 /* 2511 * This should only happen when time goes backwards, which it 2512 * unfortunately does during sched clock init when we swap over to TSC. 2513 */ 2514 if ((s64)delta < 0) { 2515 sa->last_runnable_update = now; 2516 return 0; 2517 } 2518 2519 /* 2520 * Use 1024ns as the unit of measurement since it's a reasonable 2521 * approximation of 1us and fast to compute. 2522 */ 2523 delta >>= 10; 2524 if (!delta) 2525 return 0; 2526 sa->last_runnable_update = now; 2527 2528 /* delta_w is the amount already accumulated against our next period */ 2529 delta_w = sa->runnable_avg_period % 1024; 2530 if (delta + delta_w >= 1024) { 2531 /* period roll-over */ 2532 decayed = 1; 2533 2534 /* 2535 * Now that we know we're crossing a period boundary, figure 2536 * out how much from delta we need to complete the current 2537 * period and accrue it. 2538 */ 2539 delta_w = 1024 - delta_w; 2540 if (runnable) 2541 sa->runnable_avg_sum += delta_w; 2542 sa->runnable_avg_period += delta_w; 2543 2544 delta -= delta_w; 2545 2546 /* Figure out how many additional periods this update spans */ 2547 periods = delta / 1024; 2548 delta %= 1024; 2549 2550 sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum, 2551 periods + 1); 2552 sa->runnable_avg_period = decay_load(sa->runnable_avg_period, 2553 periods + 1); 2554 2555 /* Efficiently calculate \sum (1..n_period) 1024*y^i */ 2556 runnable_contrib = __compute_runnable_contrib(periods); 2557 if (runnable) 2558 sa->runnable_avg_sum += runnable_contrib; 2559 sa->runnable_avg_period += runnable_contrib; 2560 } 2561 2562 /* Remainder of delta accrued against u_0` */ 2563 if (runnable) 2564 sa->runnable_avg_sum += delta; 2565 sa->runnable_avg_period += delta; 2566 2567 return decayed; 2568 } 2569 2570 /* Synchronize an entity's decay with its parenting cfs_rq.*/ 2571 static inline u64 __synchronize_entity_decay(struct sched_entity *se) 2572 { 2573 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2574 u64 decays = atomic64_read(&cfs_rq->decay_counter); 2575 2576 decays -= se->avg.decay_count; 2577 if (!decays) 2578 return 0; 2579 2580 se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays); 2581 se->avg.decay_count = 0; 2582 2583 return decays; 2584 } 2585 2586 #ifdef CONFIG_FAIR_GROUP_SCHED 2587 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, 2588 int force_update) 2589 { 2590 struct task_group *tg = cfs_rq->tg; 2591 long tg_contrib; 2592 2593 tg_contrib = cfs_rq->runnable_load_avg + cfs_rq->blocked_load_avg; 2594 tg_contrib -= cfs_rq->tg_load_contrib; 2595 2596 if (!tg_contrib) 2597 return; 2598 2599 if (force_update || abs(tg_contrib) > cfs_rq->tg_load_contrib / 8) { 2600 atomic_long_add(tg_contrib, &tg->load_avg); 2601 cfs_rq->tg_load_contrib += tg_contrib; 2602 } 2603 } 2604 2605 /* 2606 * Aggregate cfs_rq runnable averages into an equivalent task_group 2607 * representation for computing load contributions. 2608 */ 2609 static inline void __update_tg_runnable_avg(struct sched_avg *sa, 2610 struct cfs_rq *cfs_rq) 2611 { 2612 struct task_group *tg = cfs_rq->tg; 2613 long contrib; 2614 2615 /* The fraction of a cpu used by this cfs_rq */ 2616 contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT, 2617 sa->runnable_avg_period + 1); 2618 contrib -= cfs_rq->tg_runnable_contrib; 2619 2620 if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) { 2621 atomic_add(contrib, &tg->runnable_avg); 2622 cfs_rq->tg_runnable_contrib += contrib; 2623 } 2624 } 2625 2626 static inline void __update_group_entity_contrib(struct sched_entity *se) 2627 { 2628 struct cfs_rq *cfs_rq = group_cfs_rq(se); 2629 struct task_group *tg = cfs_rq->tg; 2630 int runnable_avg; 2631 2632 u64 contrib; 2633 2634 contrib = cfs_rq->tg_load_contrib * tg->shares; 2635 se->avg.load_avg_contrib = div_u64(contrib, 2636 atomic_long_read(&tg->load_avg) + 1); 2637 2638 /* 2639 * For group entities we need to compute a correction term in the case 2640 * that they are consuming <1 cpu so that we would contribute the same 2641 * load as a task of equal weight. 2642 * 2643 * Explicitly co-ordinating this measurement would be expensive, but 2644 * fortunately the sum of each cpus contribution forms a usable 2645 * lower-bound on the true value. 2646 * 2647 * Consider the aggregate of 2 contributions. Either they are disjoint 2648 * (and the sum represents true value) or they are disjoint and we are 2649 * understating by the aggregate of their overlap. 2650 * 2651 * Extending this to N cpus, for a given overlap, the maximum amount we 2652 * understand is then n_i(n_i+1)/2 * w_i where n_i is the number of 2653 * cpus that overlap for this interval and w_i is the interval width. 2654 * 2655 * On a small machine; the first term is well-bounded which bounds the 2656 * total error since w_i is a subset of the period. Whereas on a 2657 * larger machine, while this first term can be larger, if w_i is the 2658 * of consequential size guaranteed to see n_i*w_i quickly converge to 2659 * our upper bound of 1-cpu. 2660 */ 2661 runnable_avg = atomic_read(&tg->runnable_avg); 2662 if (runnable_avg < NICE_0_LOAD) { 2663 se->avg.load_avg_contrib *= runnable_avg; 2664 se->avg.load_avg_contrib >>= NICE_0_SHIFT; 2665 } 2666 } 2667 2668 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) 2669 { 2670 __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable); 2671 __update_tg_runnable_avg(&rq->avg, &rq->cfs); 2672 } 2673 #else /* CONFIG_FAIR_GROUP_SCHED */ 2674 static inline void __update_cfs_rq_tg_load_contrib(struct cfs_rq *cfs_rq, 2675 int force_update) {} 2676 static inline void __update_tg_runnable_avg(struct sched_avg *sa, 2677 struct cfs_rq *cfs_rq) {} 2678 static inline void __update_group_entity_contrib(struct sched_entity *se) {} 2679 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} 2680 #endif /* CONFIG_FAIR_GROUP_SCHED */ 2681 2682 static inline void __update_task_entity_contrib(struct sched_entity *se) 2683 { 2684 u32 contrib; 2685 2686 /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */ 2687 contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight); 2688 contrib /= (se->avg.runnable_avg_period + 1); 2689 se->avg.load_avg_contrib = scale_load(contrib); 2690 } 2691 2692 /* Compute the current contribution to load_avg by se, return any delta */ 2693 static long __update_entity_load_avg_contrib(struct sched_entity *se) 2694 { 2695 long old_contrib = se->avg.load_avg_contrib; 2696 2697 if (entity_is_task(se)) { 2698 __update_task_entity_contrib(se); 2699 } else { 2700 __update_tg_runnable_avg(&se->avg, group_cfs_rq(se)); 2701 __update_group_entity_contrib(se); 2702 } 2703 2704 return se->avg.load_avg_contrib - old_contrib; 2705 } 2706 2707 static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq, 2708 long load_contrib) 2709 { 2710 if (likely(load_contrib < cfs_rq->blocked_load_avg)) 2711 cfs_rq->blocked_load_avg -= load_contrib; 2712 else 2713 cfs_rq->blocked_load_avg = 0; 2714 } 2715 2716 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); 2717 2718 /* Update a sched_entity's runnable average */ 2719 static inline void update_entity_load_avg(struct sched_entity *se, 2720 int update_cfs_rq) 2721 { 2722 struct cfs_rq *cfs_rq = cfs_rq_of(se); 2723 long contrib_delta; 2724 u64 now; 2725 2726 /* 2727 * For a group entity we need to use their owned cfs_rq_clock_task() in 2728 * case they are the parent of a throttled hierarchy. 2729 */ 2730 if (entity_is_task(se)) 2731 now = cfs_rq_clock_task(cfs_rq); 2732 else 2733 now = cfs_rq_clock_task(group_cfs_rq(se)); 2734 2735 if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq)) 2736 return; 2737 2738 contrib_delta = __update_entity_load_avg_contrib(se); 2739 2740 if (!update_cfs_rq) 2741 return; 2742 2743 if (se->on_rq) 2744 cfs_rq->runnable_load_avg += contrib_delta; 2745 else 2746 subtract_blocked_load_contrib(cfs_rq, -contrib_delta); 2747 } 2748 2749 /* 2750 * Decay the load contributed by all blocked children and account this so that 2751 * their contribution may appropriately discounted when they wake up. 2752 */ 2753 static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update) 2754 { 2755 u64 now = cfs_rq_clock_task(cfs_rq) >> 20; 2756 u64 decays; 2757 2758 decays = now - cfs_rq->last_decay; 2759 if (!decays && !force_update) 2760 return; 2761 2762 if (atomic_long_read(&cfs_rq->removed_load)) { 2763 unsigned long removed_load; 2764 removed_load = atomic_long_xchg(&cfs_rq->removed_load, 0); 2765 subtract_blocked_load_contrib(cfs_rq, removed_load); 2766 } 2767 2768 if (decays) { 2769 cfs_rq->blocked_load_avg = decay_load(cfs_rq->blocked_load_avg, 2770 decays); 2771 atomic64_add(decays, &cfs_rq->decay_counter); 2772 cfs_rq->last_decay = now; 2773 } 2774 2775 __update_cfs_rq_tg_load_contrib(cfs_rq, force_update); 2776 } 2777 2778 /* Add the load generated by se into cfs_rq's child load-average */ 2779 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, 2780 struct sched_entity *se, 2781 int wakeup) 2782 { 2783 /* 2784 * We track migrations using entity decay_count <= 0, on a wake-up 2785 * migration we use a negative decay count to track the remote decays 2786 * accumulated while sleeping. 2787 * 2788 * Newly forked tasks are enqueued with se->avg.decay_count == 0, they 2789 * are seen by enqueue_entity_load_avg() as a migration with an already 2790 * constructed load_avg_contrib. 2791 */ 2792 if (unlikely(se->avg.decay_count <= 0)) { 2793 se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq)); 2794 if (se->avg.decay_count) { 2795 /* 2796 * In a wake-up migration we have to approximate the 2797 * time sleeping. This is because we can't synchronize 2798 * clock_task between the two cpus, and it is not 2799 * guaranteed to be read-safe. Instead, we can 2800 * approximate this using our carried decays, which are 2801 * explicitly atomically readable. 2802 */ 2803 se->avg.last_runnable_update -= (-se->avg.decay_count) 2804 << 20; 2805 update_entity_load_avg(se, 0); 2806 /* Indicate that we're now synchronized and on-rq */ 2807 se->avg.decay_count = 0; 2808 } 2809 wakeup = 0; 2810 } else { 2811 __synchronize_entity_decay(se); 2812 } 2813 2814 /* migrated tasks did not contribute to our blocked load */ 2815 if (wakeup) { 2816 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); 2817 update_entity_load_avg(se, 0); 2818 } 2819 2820 cfs_rq->runnable_load_avg += se->avg.load_avg_contrib; 2821 /* we force update consideration on load-balancer moves */ 2822 update_cfs_rq_blocked_load(cfs_rq, !wakeup); 2823 } 2824 2825 /* 2826 * Remove se's load from this cfs_rq child load-average, if the entity is 2827 * transitioning to a blocked state we track its projected decay using 2828 * blocked_load_avg. 2829 */ 2830 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, 2831 struct sched_entity *se, 2832 int sleep) 2833 { 2834 update_entity_load_avg(se, 1); 2835 /* we force update consideration on load-balancer moves */ 2836 update_cfs_rq_blocked_load(cfs_rq, !sleep); 2837 2838 cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib; 2839 if (sleep) { 2840 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; 2841 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); 2842 } /* migrations, e.g. sleep=0 leave decay_count == 0 */ 2843 } 2844 2845 /* 2846 * Update the rq's load with the elapsed running time before entering 2847 * idle. if the last scheduled task is not a CFS task, idle_enter will 2848 * be the only way to update the runnable statistic. 2849 */ 2850 void idle_enter_fair(struct rq *this_rq) 2851 { 2852 update_rq_runnable_avg(this_rq, 1); 2853 } 2854 2855 /* 2856 * Update the rq's load with the elapsed idle time before a task is 2857 * scheduled. if the newly scheduled task is not a CFS task, idle_exit will 2858 * be the only way to update the runnable statistic. 2859 */ 2860 void idle_exit_fair(struct rq *this_rq) 2861 { 2862 update_rq_runnable_avg(this_rq, 0); 2863 } 2864 2865 static int idle_balance(struct rq *this_rq); 2866 2867 #else /* CONFIG_SMP */ 2868 2869 static inline void update_entity_load_avg(struct sched_entity *se, 2870 int update_cfs_rq) {} 2871 static inline void update_rq_runnable_avg(struct rq *rq, int runnable) {} 2872 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq, 2873 struct sched_entity *se, 2874 int wakeup) {} 2875 static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq, 2876 struct sched_entity *se, 2877 int sleep) {} 2878 static inline void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, 2879 int force_update) {} 2880 2881 static inline int idle_balance(struct rq *rq) 2882 { 2883 return 0; 2884 } 2885 2886 #endif /* CONFIG_SMP */ 2887 2888 static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) 2889 { 2890 #ifdef CONFIG_SCHEDSTATS 2891 struct task_struct *tsk = NULL; 2892 2893 if (entity_is_task(se)) 2894 tsk = task_of(se); 2895 2896 if (se->statistics.sleep_start) { 2897 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.sleep_start; 2898 2899 if ((s64)delta < 0) 2900 delta = 0; 2901 2902 if (unlikely(delta > se->statistics.sleep_max)) 2903 se->statistics.sleep_max = delta; 2904 2905 se->statistics.sleep_start = 0; 2906 se->statistics.sum_sleep_runtime += delta; 2907 2908 if (tsk) { 2909 account_scheduler_latency(tsk, delta >> 10, 1); 2910 trace_sched_stat_sleep(tsk, delta); 2911 } 2912 } 2913 if (se->statistics.block_start) { 2914 u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.block_start; 2915 2916 if ((s64)delta < 0) 2917 delta = 0; 2918 2919 if (unlikely(delta > se->statistics.block_max)) 2920 se->statistics.block_max = delta; 2921 2922 se->statistics.block_start = 0; 2923 se->statistics.sum_sleep_runtime += delta; 2924 2925 if (tsk) { 2926 if (tsk->in_iowait) { 2927 se->statistics.iowait_sum += delta; 2928 se->statistics.iowait_count++; 2929 trace_sched_stat_iowait(tsk, delta); 2930 } 2931 2932 trace_sched_stat_blocked(tsk, delta); 2933 2934 /* 2935 * Blocking time is in units of nanosecs, so shift by 2936 * 20 to get a milliseconds-range estimation of the 2937 * amount of time that the task spent sleeping: 2938 */ 2939 if (unlikely(prof_on == SLEEP_PROFILING)) { 2940 profile_hits(SLEEP_PROFILING, 2941 (void *)get_wchan(tsk), 2942 delta >> 20); 2943 } 2944 account_scheduler_latency(tsk, delta >> 10, 0); 2945 } 2946 } 2947 #endif 2948 } 2949 2950 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) 2951 { 2952 #ifdef CONFIG_SCHED_DEBUG 2953 s64 d = se->vruntime - cfs_rq->min_vruntime; 2954 2955 if (d < 0) 2956 d = -d; 2957 2958 if (d > 3*sysctl_sched_latency) 2959 schedstat_inc(cfs_rq, nr_spread_over); 2960 #endif 2961 } 2962 2963 static void 2964 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 2965 { 2966 u64 vruntime = cfs_rq->min_vruntime; 2967 2968 /* 2969 * The 'current' period is already promised to the current tasks, 2970 * however the extra weight of the new task will slow them down a 2971 * little, place the new task so that it fits in the slot that 2972 * stays open at the end. 2973 */ 2974 if (initial && sched_feat(START_DEBIT)) 2975 vruntime += sched_vslice(cfs_rq, se); 2976 2977 /* sleeps up to a single latency don't count. */ 2978 if (!initial) { 2979 unsigned long thresh = sysctl_sched_latency; 2980 2981 /* 2982 * Halve their sleep time's effect, to allow 2983 * for a gentler effect of sleepers: 2984 */ 2985 if (sched_feat(GENTLE_FAIR_SLEEPERS)) 2986 thresh >>= 1; 2987 2988 vruntime -= thresh; 2989 } 2990 2991 /* ensure we never gain time by being placed backwards. */ 2992 se->vruntime = max_vruntime(se->vruntime, vruntime); 2993 } 2994 2995 static void check_enqueue_throttle(struct cfs_rq *cfs_rq); 2996 2997 static void 2998 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 2999 { 3000 /* 3001 * Update the normalized vruntime before updating min_vruntime 3002 * through calling update_curr(). 3003 */ 3004 if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) 3005 se->vruntime += cfs_rq->min_vruntime; 3006 3007 /* 3008 * Update run-time statistics of the 'current'. 3009 */ 3010 update_curr(cfs_rq); 3011 enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP); 3012 account_entity_enqueue(cfs_rq, se); 3013 update_cfs_shares(cfs_rq); 3014 3015 if (flags & ENQUEUE_WAKEUP) { 3016 place_entity(cfs_rq, se, 0); 3017 enqueue_sleeper(cfs_rq, se); 3018 } 3019 3020 update_stats_enqueue(cfs_rq, se); 3021 check_spread(cfs_rq, se); 3022 if (se != cfs_rq->curr) 3023 __enqueue_entity(cfs_rq, se); 3024 se->on_rq = 1; 3025 3026 if (cfs_rq->nr_running == 1) { 3027 list_add_leaf_cfs_rq(cfs_rq); 3028 check_enqueue_throttle(cfs_rq); 3029 } 3030 } 3031 3032 static void __clear_buddies_last(struct sched_entity *se) 3033 { 3034 for_each_sched_entity(se) { 3035 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3036 if (cfs_rq->last != se) 3037 break; 3038 3039 cfs_rq->last = NULL; 3040 } 3041 } 3042 3043 static void __clear_buddies_next(struct sched_entity *se) 3044 { 3045 for_each_sched_entity(se) { 3046 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3047 if (cfs_rq->next != se) 3048 break; 3049 3050 cfs_rq->next = NULL; 3051 } 3052 } 3053 3054 static void __clear_buddies_skip(struct sched_entity *se) 3055 { 3056 for_each_sched_entity(se) { 3057 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3058 if (cfs_rq->skip != se) 3059 break; 3060 3061 cfs_rq->skip = NULL; 3062 } 3063 } 3064 3065 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) 3066 { 3067 if (cfs_rq->last == se) 3068 __clear_buddies_last(se); 3069 3070 if (cfs_rq->next == se) 3071 __clear_buddies_next(se); 3072 3073 if (cfs_rq->skip == se) 3074 __clear_buddies_skip(se); 3075 } 3076 3077 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); 3078 3079 static void 3080 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 3081 { 3082 /* 3083 * Update run-time statistics of the 'current'. 3084 */ 3085 update_curr(cfs_rq); 3086 dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP); 3087 3088 update_stats_dequeue(cfs_rq, se); 3089 if (flags & DEQUEUE_SLEEP) { 3090 #ifdef CONFIG_SCHEDSTATS 3091 if (entity_is_task(se)) { 3092 struct task_struct *tsk = task_of(se); 3093 3094 if (tsk->state & TASK_INTERRUPTIBLE) 3095 se->statistics.sleep_start = rq_clock(rq_of(cfs_rq)); 3096 if (tsk->state & TASK_UNINTERRUPTIBLE) 3097 se->statistics.block_start = rq_clock(rq_of(cfs_rq)); 3098 } 3099 #endif 3100 } 3101 3102 clear_buddies(cfs_rq, se); 3103 3104 if (se != cfs_rq->curr) 3105 __dequeue_entity(cfs_rq, se); 3106 se->on_rq = 0; 3107 account_entity_dequeue(cfs_rq, se); 3108 3109 /* 3110 * Normalize the entity after updating the min_vruntime because the 3111 * update can refer to the ->curr item and we need to reflect this 3112 * movement in our normalized position. 3113 */ 3114 if (!(flags & DEQUEUE_SLEEP)) 3115 se->vruntime -= cfs_rq->min_vruntime; 3116 3117 /* return excess runtime on last dequeue */ 3118 return_cfs_rq_runtime(cfs_rq); 3119 3120 update_min_vruntime(cfs_rq); 3121 update_cfs_shares(cfs_rq); 3122 } 3123 3124 /* 3125 * Preempt the current task with a newly woken task if needed: 3126 */ 3127 static void 3128 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 3129 { 3130 unsigned long ideal_runtime, delta_exec; 3131 struct sched_entity *se; 3132 s64 delta; 3133 3134 ideal_runtime = sched_slice(cfs_rq, curr); 3135 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; 3136 if (delta_exec > ideal_runtime) { 3137 resched_curr(rq_of(cfs_rq)); 3138 /* 3139 * The current task ran long enough, ensure it doesn't get 3140 * re-elected due to buddy favours. 3141 */ 3142 clear_buddies(cfs_rq, curr); 3143 return; 3144 } 3145 3146 /* 3147 * Ensure that a task that missed wakeup preemption by a 3148 * narrow margin doesn't have to wait for a full slice. 3149 * This also mitigates buddy induced latencies under load. 3150 */ 3151 if (delta_exec < sysctl_sched_min_granularity) 3152 return; 3153 3154 se = __pick_first_entity(cfs_rq); 3155 delta = curr->vruntime - se->vruntime; 3156 3157 if (delta < 0) 3158 return; 3159 3160 if (delta > ideal_runtime) 3161 resched_curr(rq_of(cfs_rq)); 3162 } 3163 3164 static void 3165 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 3166 { 3167 /* 'current' is not kept within the tree. */ 3168 if (se->on_rq) { 3169 /* 3170 * Any task has to be enqueued before it get to execute on 3171 * a CPU. So account for the time it spent waiting on the 3172 * runqueue. 3173 */ 3174 update_stats_wait_end(cfs_rq, se); 3175 __dequeue_entity(cfs_rq, se); 3176 } 3177 3178 update_stats_curr_start(cfs_rq, se); 3179 cfs_rq->curr = se; 3180 #ifdef CONFIG_SCHEDSTATS 3181 /* 3182 * Track our maximum slice length, if the CPU's load is at 3183 * least twice that of our own weight (i.e. dont track it 3184 * when there are only lesser-weight tasks around): 3185 */ 3186 if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { 3187 se->statistics.slice_max = max(se->statistics.slice_max, 3188 se->sum_exec_runtime - se->prev_sum_exec_runtime); 3189 } 3190 #endif 3191 se->prev_sum_exec_runtime = se->sum_exec_runtime; 3192 } 3193 3194 static int 3195 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); 3196 3197 /* 3198 * Pick the next process, keeping these things in mind, in this order: 3199 * 1) keep things fair between processes/task groups 3200 * 2) pick the "next" process, since someone really wants that to run 3201 * 3) pick the "last" process, for cache locality 3202 * 4) do not run the "skip" process, if something else is available 3203 */ 3204 static struct sched_entity * 3205 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) 3206 { 3207 struct sched_entity *left = __pick_first_entity(cfs_rq); 3208 struct sched_entity *se; 3209 3210 /* 3211 * If curr is set we have to see if its left of the leftmost entity 3212 * still in the tree, provided there was anything in the tree at all. 3213 */ 3214 if (!left || (curr && entity_before(curr, left))) 3215 left = curr; 3216 3217 se = left; /* ideally we run the leftmost entity */ 3218 3219 /* 3220 * Avoid running the skip buddy, if running something else can 3221 * be done without getting too unfair. 3222 */ 3223 if (cfs_rq->skip == se) { 3224 struct sched_entity *second; 3225 3226 if (se == curr) { 3227 second = __pick_first_entity(cfs_rq); 3228 } else { 3229 second = __pick_next_entity(se); 3230 if (!second || (curr && entity_before(curr, second))) 3231 second = curr; 3232 } 3233 3234 if (second && wakeup_preempt_entity(second, left) < 1) 3235 se = second; 3236 } 3237 3238 /* 3239 * Prefer last buddy, try to return the CPU to a preempted task. 3240 */ 3241 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) 3242 se = cfs_rq->last; 3243 3244 /* 3245 * Someone really wants this to run. If it's not unfair, run it. 3246 */ 3247 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) 3248 se = cfs_rq->next; 3249 3250 clear_buddies(cfs_rq, se); 3251 3252 return se; 3253 } 3254 3255 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); 3256 3257 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) 3258 { 3259 /* 3260 * If still on the runqueue then deactivate_task() 3261 * was not called and update_curr() has to be done: 3262 */ 3263 if (prev->on_rq) 3264 update_curr(cfs_rq); 3265 3266 /* throttle cfs_rqs exceeding runtime */ 3267 check_cfs_rq_runtime(cfs_rq); 3268 3269 check_spread(cfs_rq, prev); 3270 if (prev->on_rq) { 3271 update_stats_wait_start(cfs_rq, prev); 3272 /* Put 'current' back into the tree. */ 3273 __enqueue_entity(cfs_rq, prev); 3274 /* in !on_rq case, update occurred at dequeue */ 3275 update_entity_load_avg(prev, 1); 3276 } 3277 cfs_rq->curr = NULL; 3278 } 3279 3280 static void 3281 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) 3282 { 3283 /* 3284 * Update run-time statistics of the 'current'. 3285 */ 3286 update_curr(cfs_rq); 3287 3288 /* 3289 * Ensure that runnable average is periodically updated. 3290 */ 3291 update_entity_load_avg(curr, 1); 3292 update_cfs_rq_blocked_load(cfs_rq, 1); 3293 update_cfs_shares(cfs_rq); 3294 3295 #ifdef CONFIG_SCHED_HRTICK 3296 /* 3297 * queued ticks are scheduled to match the slice, so don't bother 3298 * validating it and just reschedule. 3299 */ 3300 if (queued) { 3301 resched_curr(rq_of(cfs_rq)); 3302 return; 3303 } 3304 /* 3305 * don't let the period tick interfere with the hrtick preemption 3306 */ 3307 if (!sched_feat(DOUBLE_TICK) && 3308 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) 3309 return; 3310 #endif 3311 3312 if (cfs_rq->nr_running > 1) 3313 check_preempt_tick(cfs_rq, curr); 3314 } 3315 3316 3317 /************************************************** 3318 * CFS bandwidth control machinery 3319 */ 3320 3321 #ifdef CONFIG_CFS_BANDWIDTH 3322 3323 #ifdef HAVE_JUMP_LABEL 3324 static struct static_key __cfs_bandwidth_used; 3325 3326 static inline bool cfs_bandwidth_used(void) 3327 { 3328 return static_key_false(&__cfs_bandwidth_used); 3329 } 3330 3331 void cfs_bandwidth_usage_inc(void) 3332 { 3333 static_key_slow_inc(&__cfs_bandwidth_used); 3334 } 3335 3336 void cfs_bandwidth_usage_dec(void) 3337 { 3338 static_key_slow_dec(&__cfs_bandwidth_used); 3339 } 3340 #else /* HAVE_JUMP_LABEL */ 3341 static bool cfs_bandwidth_used(void) 3342 { 3343 return true; 3344 } 3345 3346 void cfs_bandwidth_usage_inc(void) {} 3347 void cfs_bandwidth_usage_dec(void) {} 3348 #endif /* HAVE_JUMP_LABEL */ 3349 3350 /* 3351 * default period for cfs group bandwidth. 3352 * default: 0.1s, units: nanoseconds 3353 */ 3354 static inline u64 default_cfs_period(void) 3355 { 3356 return 100000000ULL; 3357 } 3358 3359 static inline u64 sched_cfs_bandwidth_slice(void) 3360 { 3361 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; 3362 } 3363 3364 /* 3365 * Replenish runtime according to assigned quota and update expiration time. 3366 * We use sched_clock_cpu directly instead of rq->clock to avoid adding 3367 * additional synchronization around rq->lock. 3368 * 3369 * requires cfs_b->lock 3370 */ 3371 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) 3372 { 3373 u64 now; 3374 3375 if (cfs_b->quota == RUNTIME_INF) 3376 return; 3377 3378 now = sched_clock_cpu(smp_processor_id()); 3379 cfs_b->runtime = cfs_b->quota; 3380 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); 3381 } 3382 3383 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 3384 { 3385 return &tg->cfs_bandwidth; 3386 } 3387 3388 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */ 3389 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 3390 { 3391 if (unlikely(cfs_rq->throttle_count)) 3392 return cfs_rq->throttled_clock_task; 3393 3394 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; 3395 } 3396 3397 /* returns 0 on failure to allocate runtime */ 3398 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3399 { 3400 struct task_group *tg = cfs_rq->tg; 3401 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); 3402 u64 amount = 0, min_amount, expires; 3403 3404 /* note: this is a positive sum as runtime_remaining <= 0 */ 3405 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; 3406 3407 raw_spin_lock(&cfs_b->lock); 3408 if (cfs_b->quota == RUNTIME_INF) 3409 amount = min_amount; 3410 else { 3411 /* 3412 * If the bandwidth pool has become inactive, then at least one 3413 * period must have elapsed since the last consumption. 3414 * Refresh the global state and ensure bandwidth timer becomes 3415 * active. 3416 */ 3417 if (!cfs_b->timer_active) { 3418 __refill_cfs_bandwidth_runtime(cfs_b); 3419 __start_cfs_bandwidth(cfs_b, false); 3420 } 3421 3422 if (cfs_b->runtime > 0) { 3423 amount = min(cfs_b->runtime, min_amount); 3424 cfs_b->runtime -= amount; 3425 cfs_b->idle = 0; 3426 } 3427 } 3428 expires = cfs_b->runtime_expires; 3429 raw_spin_unlock(&cfs_b->lock); 3430 3431 cfs_rq->runtime_remaining += amount; 3432 /* 3433 * we may have advanced our local expiration to account for allowed 3434 * spread between our sched_clock and the one on which runtime was 3435 * issued. 3436 */ 3437 if ((s64)(expires - cfs_rq->runtime_expires) > 0) 3438 cfs_rq->runtime_expires = expires; 3439 3440 return cfs_rq->runtime_remaining > 0; 3441 } 3442 3443 /* 3444 * Note: This depends on the synchronization provided by sched_clock and the 3445 * fact that rq->clock snapshots this value. 3446 */ 3447 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3448 { 3449 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3450 3451 /* if the deadline is ahead of our clock, nothing to do */ 3452 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0)) 3453 return; 3454 3455 if (cfs_rq->runtime_remaining < 0) 3456 return; 3457 3458 /* 3459 * If the local deadline has passed we have to consider the 3460 * possibility that our sched_clock is 'fast' and the global deadline 3461 * has not truly expired. 3462 * 3463 * Fortunately we can check determine whether this the case by checking 3464 * whether the global deadline has advanced. It is valid to compare 3465 * cfs_b->runtime_expires without any locks since we only care about 3466 * exact equality, so a partial write will still work. 3467 */ 3468 3469 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) { 3470 /* extend local deadline, drift is bounded above by 2 ticks */ 3471 cfs_rq->runtime_expires += TICK_NSEC; 3472 } else { 3473 /* global deadline is ahead, expiration has passed */ 3474 cfs_rq->runtime_remaining = 0; 3475 } 3476 } 3477 3478 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 3479 { 3480 /* dock delta_exec before expiring quota (as it could span periods) */ 3481 cfs_rq->runtime_remaining -= delta_exec; 3482 expire_cfs_rq_runtime(cfs_rq); 3483 3484 if (likely(cfs_rq->runtime_remaining > 0)) 3485 return; 3486 3487 /* 3488 * if we're unable to extend our runtime we resched so that the active 3489 * hierarchy can be throttled 3490 */ 3491 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) 3492 resched_curr(rq_of(cfs_rq)); 3493 } 3494 3495 static __always_inline 3496 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 3497 { 3498 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) 3499 return; 3500 3501 __account_cfs_rq_runtime(cfs_rq, delta_exec); 3502 } 3503 3504 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 3505 { 3506 return cfs_bandwidth_used() && cfs_rq->throttled; 3507 } 3508 3509 /* check whether cfs_rq, or any parent, is throttled */ 3510 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 3511 { 3512 return cfs_bandwidth_used() && cfs_rq->throttle_count; 3513 } 3514 3515 /* 3516 * Ensure that neither of the group entities corresponding to src_cpu or 3517 * dest_cpu are members of a throttled hierarchy when performing group 3518 * load-balance operations. 3519 */ 3520 static inline int throttled_lb_pair(struct task_group *tg, 3521 int src_cpu, int dest_cpu) 3522 { 3523 struct cfs_rq *src_cfs_rq, *dest_cfs_rq; 3524 3525 src_cfs_rq = tg->cfs_rq[src_cpu]; 3526 dest_cfs_rq = tg->cfs_rq[dest_cpu]; 3527 3528 return throttled_hierarchy(src_cfs_rq) || 3529 throttled_hierarchy(dest_cfs_rq); 3530 } 3531 3532 /* updated child weight may affect parent so we have to do this bottom up */ 3533 static int tg_unthrottle_up(struct task_group *tg, void *data) 3534 { 3535 struct rq *rq = data; 3536 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 3537 3538 cfs_rq->throttle_count--; 3539 #ifdef CONFIG_SMP 3540 if (!cfs_rq->throttle_count) { 3541 /* adjust cfs_rq_clock_task() */ 3542 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - 3543 cfs_rq->throttled_clock_task; 3544 } 3545 #endif 3546 3547 return 0; 3548 } 3549 3550 static int tg_throttle_down(struct task_group *tg, void *data) 3551 { 3552 struct rq *rq = data; 3553 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 3554 3555 /* group is entering throttled state, stop time */ 3556 if (!cfs_rq->throttle_count) 3557 cfs_rq->throttled_clock_task = rq_clock_task(rq); 3558 cfs_rq->throttle_count++; 3559 3560 return 0; 3561 } 3562 3563 static void throttle_cfs_rq(struct cfs_rq *cfs_rq) 3564 { 3565 struct rq *rq = rq_of(cfs_rq); 3566 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3567 struct sched_entity *se; 3568 long task_delta, dequeue = 1; 3569 3570 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; 3571 3572 /* freeze hierarchy runnable averages while throttled */ 3573 rcu_read_lock(); 3574 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); 3575 rcu_read_unlock(); 3576 3577 task_delta = cfs_rq->h_nr_running; 3578 for_each_sched_entity(se) { 3579 struct cfs_rq *qcfs_rq = cfs_rq_of(se); 3580 /* throttled entity or throttle-on-deactivate */ 3581 if (!se->on_rq) 3582 break; 3583 3584 if (dequeue) 3585 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); 3586 qcfs_rq->h_nr_running -= task_delta; 3587 3588 if (qcfs_rq->load.weight) 3589 dequeue = 0; 3590 } 3591 3592 if (!se) 3593 sub_nr_running(rq, task_delta); 3594 3595 cfs_rq->throttled = 1; 3596 cfs_rq->throttled_clock = rq_clock(rq); 3597 raw_spin_lock(&cfs_b->lock); 3598 /* 3599 * Add to the _head_ of the list, so that an already-started 3600 * distribute_cfs_runtime will not see us 3601 */ 3602 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); 3603 if (!cfs_b->timer_active) 3604 __start_cfs_bandwidth(cfs_b, false); 3605 raw_spin_unlock(&cfs_b->lock); 3606 } 3607 3608 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 3609 { 3610 struct rq *rq = rq_of(cfs_rq); 3611 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3612 struct sched_entity *se; 3613 int enqueue = 1; 3614 long task_delta; 3615 3616 se = cfs_rq->tg->se[cpu_of(rq)]; 3617 3618 cfs_rq->throttled = 0; 3619 3620 update_rq_clock(rq); 3621 3622 raw_spin_lock(&cfs_b->lock); 3623 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; 3624 list_del_rcu(&cfs_rq->throttled_list); 3625 raw_spin_unlock(&cfs_b->lock); 3626 3627 /* update hierarchical throttle state */ 3628 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); 3629 3630 if (!cfs_rq->load.weight) 3631 return; 3632 3633 task_delta = cfs_rq->h_nr_running; 3634 for_each_sched_entity(se) { 3635 if (se->on_rq) 3636 enqueue = 0; 3637 3638 cfs_rq = cfs_rq_of(se); 3639 if (enqueue) 3640 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); 3641 cfs_rq->h_nr_running += task_delta; 3642 3643 if (cfs_rq_throttled(cfs_rq)) 3644 break; 3645 } 3646 3647 if (!se) 3648 add_nr_running(rq, task_delta); 3649 3650 /* determine whether we need to wake up potentially idle cpu */ 3651 if (rq->curr == rq->idle && rq->cfs.nr_running) 3652 resched_curr(rq); 3653 } 3654 3655 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, 3656 u64 remaining, u64 expires) 3657 { 3658 struct cfs_rq *cfs_rq; 3659 u64 runtime; 3660 u64 starting_runtime = remaining; 3661 3662 rcu_read_lock(); 3663 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, 3664 throttled_list) { 3665 struct rq *rq = rq_of(cfs_rq); 3666 3667 raw_spin_lock(&rq->lock); 3668 if (!cfs_rq_throttled(cfs_rq)) 3669 goto next; 3670 3671 runtime = -cfs_rq->runtime_remaining + 1; 3672 if (runtime > remaining) 3673 runtime = remaining; 3674 remaining -= runtime; 3675 3676 cfs_rq->runtime_remaining += runtime; 3677 cfs_rq->runtime_expires = expires; 3678 3679 /* we check whether we're throttled above */ 3680 if (cfs_rq->runtime_remaining > 0) 3681 unthrottle_cfs_rq(cfs_rq); 3682 3683 next: 3684 raw_spin_unlock(&rq->lock); 3685 3686 if (!remaining) 3687 break; 3688 } 3689 rcu_read_unlock(); 3690 3691 return starting_runtime - remaining; 3692 } 3693 3694 /* 3695 * Responsible for refilling a task_group's bandwidth and unthrottling its 3696 * cfs_rqs as appropriate. If there has been no activity within the last 3697 * period the timer is deactivated until scheduling resumes; cfs_b->idle is 3698 * used to track this state. 3699 */ 3700 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) 3701 { 3702 u64 runtime, runtime_expires; 3703 int throttled; 3704 3705 /* no need to continue the timer with no bandwidth constraint */ 3706 if (cfs_b->quota == RUNTIME_INF) 3707 goto out_deactivate; 3708 3709 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 3710 cfs_b->nr_periods += overrun; 3711 3712 /* 3713 * idle depends on !throttled (for the case of a large deficit), and if 3714 * we're going inactive then everything else can be deferred 3715 */ 3716 if (cfs_b->idle && !throttled) 3717 goto out_deactivate; 3718 3719 /* 3720 * if we have relooped after returning idle once, we need to update our 3721 * status as actually running, so that other cpus doing 3722 * __start_cfs_bandwidth will stop trying to cancel us. 3723 */ 3724 cfs_b->timer_active = 1; 3725 3726 __refill_cfs_bandwidth_runtime(cfs_b); 3727 3728 if (!throttled) { 3729 /* mark as potentially idle for the upcoming period */ 3730 cfs_b->idle = 1; 3731 return 0; 3732 } 3733 3734 /* account preceding periods in which throttling occurred */ 3735 cfs_b->nr_throttled += overrun; 3736 3737 runtime_expires = cfs_b->runtime_expires; 3738 3739 /* 3740 * This check is repeated as we are holding onto the new bandwidth while 3741 * we unthrottle. This can potentially race with an unthrottled group 3742 * trying to acquire new bandwidth from the global pool. This can result 3743 * in us over-using our runtime if it is all used during this loop, but 3744 * only by limited amounts in that extreme case. 3745 */ 3746 while (throttled && cfs_b->runtime > 0) { 3747 runtime = cfs_b->runtime; 3748 raw_spin_unlock(&cfs_b->lock); 3749 /* we can't nest cfs_b->lock while distributing bandwidth */ 3750 runtime = distribute_cfs_runtime(cfs_b, runtime, 3751 runtime_expires); 3752 raw_spin_lock(&cfs_b->lock); 3753 3754 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 3755 3756 cfs_b->runtime -= min(runtime, cfs_b->runtime); 3757 } 3758 3759 /* 3760 * While we are ensured activity in the period following an 3761 * unthrottle, this also covers the case in which the new bandwidth is 3762 * insufficient to cover the existing bandwidth deficit. (Forcing the 3763 * timer to remain active while there are any throttled entities.) 3764 */ 3765 cfs_b->idle = 0; 3766 3767 return 0; 3768 3769 out_deactivate: 3770 cfs_b->timer_active = 0; 3771 return 1; 3772 } 3773 3774 /* a cfs_rq won't donate quota below this amount */ 3775 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; 3776 /* minimum remaining period time to redistribute slack quota */ 3777 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; 3778 /* how long we wait to gather additional slack before distributing */ 3779 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; 3780 3781 /* 3782 * Are we near the end of the current quota period? 3783 * 3784 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the 3785 * hrtimer base being cleared by __hrtimer_start_range_ns. In the case of 3786 * migrate_hrtimers, base is never cleared, so we are fine. 3787 */ 3788 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) 3789 { 3790 struct hrtimer *refresh_timer = &cfs_b->period_timer; 3791 u64 remaining; 3792 3793 /* if the call-back is running a quota refresh is already occurring */ 3794 if (hrtimer_callback_running(refresh_timer)) 3795 return 1; 3796 3797 /* is a quota refresh about to occur? */ 3798 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); 3799 if (remaining < min_expire) 3800 return 1; 3801 3802 return 0; 3803 } 3804 3805 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) 3806 { 3807 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; 3808 3809 /* if there's a quota refresh soon don't bother with slack */ 3810 if (runtime_refresh_within(cfs_b, min_left)) 3811 return; 3812 3813 start_bandwidth_timer(&cfs_b->slack_timer, 3814 ns_to_ktime(cfs_bandwidth_slack_period)); 3815 } 3816 3817 /* we know any runtime found here is valid as update_curr() precedes return */ 3818 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3819 { 3820 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 3821 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; 3822 3823 if (slack_runtime <= 0) 3824 return; 3825 3826 raw_spin_lock(&cfs_b->lock); 3827 if (cfs_b->quota != RUNTIME_INF && 3828 cfs_rq->runtime_expires == cfs_b->runtime_expires) { 3829 cfs_b->runtime += slack_runtime; 3830 3831 /* we are under rq->lock, defer unthrottling using a timer */ 3832 if (cfs_b->runtime > sched_cfs_bandwidth_slice() && 3833 !list_empty(&cfs_b->throttled_cfs_rq)) 3834 start_cfs_slack_bandwidth(cfs_b); 3835 } 3836 raw_spin_unlock(&cfs_b->lock); 3837 3838 /* even if it's not valid for return we don't want to try again */ 3839 cfs_rq->runtime_remaining -= slack_runtime; 3840 } 3841 3842 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3843 { 3844 if (!cfs_bandwidth_used()) 3845 return; 3846 3847 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) 3848 return; 3849 3850 __return_cfs_rq_runtime(cfs_rq); 3851 } 3852 3853 /* 3854 * This is done with a timer (instead of inline with bandwidth return) since 3855 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. 3856 */ 3857 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) 3858 { 3859 u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); 3860 u64 expires; 3861 3862 /* confirm we're still not at a refresh boundary */ 3863 raw_spin_lock(&cfs_b->lock); 3864 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { 3865 raw_spin_unlock(&cfs_b->lock); 3866 return; 3867 } 3868 3869 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) 3870 runtime = cfs_b->runtime; 3871 3872 expires = cfs_b->runtime_expires; 3873 raw_spin_unlock(&cfs_b->lock); 3874 3875 if (!runtime) 3876 return; 3877 3878 runtime = distribute_cfs_runtime(cfs_b, runtime, expires); 3879 3880 raw_spin_lock(&cfs_b->lock); 3881 if (expires == cfs_b->runtime_expires) 3882 cfs_b->runtime -= min(runtime, cfs_b->runtime); 3883 raw_spin_unlock(&cfs_b->lock); 3884 } 3885 3886 /* 3887 * When a group wakes up we want to make sure that its quota is not already 3888 * expired/exceeded, otherwise it may be allowed to steal additional ticks of 3889 * runtime as update_curr() throttling can not not trigger until it's on-rq. 3890 */ 3891 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) 3892 { 3893 if (!cfs_bandwidth_used()) 3894 return; 3895 3896 /* an active group must be handled by the update_curr()->put() path */ 3897 if (!cfs_rq->runtime_enabled || cfs_rq->curr) 3898 return; 3899 3900 /* ensure the group is not already throttled */ 3901 if (cfs_rq_throttled(cfs_rq)) 3902 return; 3903 3904 /* update runtime allocation */ 3905 account_cfs_rq_runtime(cfs_rq, 0); 3906 if (cfs_rq->runtime_remaining <= 0) 3907 throttle_cfs_rq(cfs_rq); 3908 } 3909 3910 /* conditionally throttle active cfs_rq's from put_prev_entity() */ 3911 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3912 { 3913 if (!cfs_bandwidth_used()) 3914 return false; 3915 3916 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) 3917 return false; 3918 3919 /* 3920 * it's possible for a throttled entity to be forced into a running 3921 * state (e.g. set_curr_task), in this case we're finished. 3922 */ 3923 if (cfs_rq_throttled(cfs_rq)) 3924 return true; 3925 3926 throttle_cfs_rq(cfs_rq); 3927 return true; 3928 } 3929 3930 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) 3931 { 3932 struct cfs_bandwidth *cfs_b = 3933 container_of(timer, struct cfs_bandwidth, slack_timer); 3934 do_sched_cfs_slack_timer(cfs_b); 3935 3936 return HRTIMER_NORESTART; 3937 } 3938 3939 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 3940 { 3941 struct cfs_bandwidth *cfs_b = 3942 container_of(timer, struct cfs_bandwidth, period_timer); 3943 ktime_t now; 3944 int overrun; 3945 int idle = 0; 3946 3947 raw_spin_lock(&cfs_b->lock); 3948 for (;;) { 3949 now = hrtimer_cb_get_time(timer); 3950 overrun = hrtimer_forward(timer, now, cfs_b->period); 3951 3952 if (!overrun) 3953 break; 3954 3955 idle = do_sched_cfs_period_timer(cfs_b, overrun); 3956 } 3957 raw_spin_unlock(&cfs_b->lock); 3958 3959 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 3960 } 3961 3962 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 3963 { 3964 raw_spin_lock_init(&cfs_b->lock); 3965 cfs_b->runtime = 0; 3966 cfs_b->quota = RUNTIME_INF; 3967 cfs_b->period = ns_to_ktime(default_cfs_period()); 3968 3969 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); 3970 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 3971 cfs_b->period_timer.function = sched_cfs_period_timer; 3972 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 3973 cfs_b->slack_timer.function = sched_cfs_slack_timer; 3974 } 3975 3976 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3977 { 3978 cfs_rq->runtime_enabled = 0; 3979 INIT_LIST_HEAD(&cfs_rq->throttled_list); 3980 } 3981 3982 /* requires cfs_b->lock, may release to reprogram timer */ 3983 void __start_cfs_bandwidth(struct cfs_bandwidth *cfs_b, bool force) 3984 { 3985 /* 3986 * The timer may be active because we're trying to set a new bandwidth 3987 * period or because we're racing with the tear-down path 3988 * (timer_active==0 becomes visible before the hrtimer call-back 3989 * terminates). In either case we ensure that it's re-programmed 3990 */ 3991 while (unlikely(hrtimer_active(&cfs_b->period_timer)) && 3992 hrtimer_try_to_cancel(&cfs_b->period_timer) < 0) { 3993 /* bounce the lock to allow do_sched_cfs_period_timer to run */ 3994 raw_spin_unlock(&cfs_b->lock); 3995 cpu_relax(); 3996 raw_spin_lock(&cfs_b->lock); 3997 /* if someone else restarted the timer then we're done */ 3998 if (!force && cfs_b->timer_active) 3999 return; 4000 } 4001 4002 cfs_b->timer_active = 1; 4003 start_bandwidth_timer(&cfs_b->period_timer, cfs_b->period); 4004 } 4005 4006 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 4007 { 4008 /* init_cfs_bandwidth() was not called */ 4009 if (!cfs_b->throttled_cfs_rq.next) 4010 return; 4011 4012 hrtimer_cancel(&cfs_b->period_timer); 4013 hrtimer_cancel(&cfs_b->slack_timer); 4014 } 4015 4016 static void __maybe_unused update_runtime_enabled(struct rq *rq) 4017 { 4018 struct cfs_rq *cfs_rq; 4019 4020 for_each_leaf_cfs_rq(rq, cfs_rq) { 4021 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth; 4022 4023 raw_spin_lock(&cfs_b->lock); 4024 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; 4025 raw_spin_unlock(&cfs_b->lock); 4026 } 4027 } 4028 4029 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) 4030 { 4031 struct cfs_rq *cfs_rq; 4032 4033 for_each_leaf_cfs_rq(rq, cfs_rq) { 4034 if (!cfs_rq->runtime_enabled) 4035 continue; 4036 4037 /* 4038 * clock_task is not advancing so we just need to make sure 4039 * there's some valid quota amount 4040 */ 4041 cfs_rq->runtime_remaining = 1; 4042 /* 4043 * Offline rq is schedulable till cpu is completely disabled 4044 * in take_cpu_down(), so we prevent new cfs throttling here. 4045 */ 4046 cfs_rq->runtime_enabled = 0; 4047 4048 if (cfs_rq_throttled(cfs_rq)) 4049 unthrottle_cfs_rq(cfs_rq); 4050 } 4051 } 4052 4053 #else /* CONFIG_CFS_BANDWIDTH */ 4054 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 4055 { 4056 return rq_clock_task(rq_of(cfs_rq)); 4057 } 4058 4059 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} 4060 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } 4061 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} 4062 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 4063 4064 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 4065 { 4066 return 0; 4067 } 4068 4069 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 4070 { 4071 return 0; 4072 } 4073 4074 static inline int throttled_lb_pair(struct task_group *tg, 4075 int src_cpu, int dest_cpu) 4076 { 4077 return 0; 4078 } 4079 4080 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 4081 4082 #ifdef CONFIG_FAIR_GROUP_SCHED 4083 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 4084 #endif 4085 4086 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 4087 { 4088 return NULL; 4089 } 4090 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 4091 static inline void update_runtime_enabled(struct rq *rq) {} 4092 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} 4093 4094 #endif /* CONFIG_CFS_BANDWIDTH */ 4095 4096 /************************************************** 4097 * CFS operations on tasks: 4098 */ 4099 4100 #ifdef CONFIG_SCHED_HRTICK 4101 static void hrtick_start_fair(struct rq *rq, struct task_struct *p) 4102 { 4103 struct sched_entity *se = &p->se; 4104 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4105 4106 WARN_ON(task_rq(p) != rq); 4107 4108 if (cfs_rq->nr_running > 1) { 4109 u64 slice = sched_slice(cfs_rq, se); 4110 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; 4111 s64 delta = slice - ran; 4112 4113 if (delta < 0) { 4114 if (rq->curr == p) 4115 resched_curr(rq); 4116 return; 4117 } 4118 hrtick_start(rq, delta); 4119 } 4120 } 4121 4122 /* 4123 * called from enqueue/dequeue and updates the hrtick when the 4124 * current task is from our class and nr_running is low enough 4125 * to matter. 4126 */ 4127 static void hrtick_update(struct rq *rq) 4128 { 4129 struct task_struct *curr = rq->curr; 4130 4131 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) 4132 return; 4133 4134 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) 4135 hrtick_start_fair(rq, curr); 4136 } 4137 #else /* !CONFIG_SCHED_HRTICK */ 4138 static inline void 4139 hrtick_start_fair(struct rq *rq, struct task_struct *p) 4140 { 4141 } 4142 4143 static inline void hrtick_update(struct rq *rq) 4144 { 4145 } 4146 #endif 4147 4148 /* 4149 * The enqueue_task method is called before nr_running is 4150 * increased. Here we update the fair scheduling stats and 4151 * then put the task into the rbtree: 4152 */ 4153 static void 4154 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 4155 { 4156 struct cfs_rq *cfs_rq; 4157 struct sched_entity *se = &p->se; 4158 4159 for_each_sched_entity(se) { 4160 if (se->on_rq) 4161 break; 4162 cfs_rq = cfs_rq_of(se); 4163 enqueue_entity(cfs_rq, se, flags); 4164 4165 /* 4166 * end evaluation on encountering a throttled cfs_rq 4167 * 4168 * note: in the case of encountering a throttled cfs_rq we will 4169 * post the final h_nr_running increment below. 4170 */ 4171 if (cfs_rq_throttled(cfs_rq)) 4172 break; 4173 cfs_rq->h_nr_running++; 4174 4175 flags = ENQUEUE_WAKEUP; 4176 } 4177 4178 for_each_sched_entity(se) { 4179 cfs_rq = cfs_rq_of(se); 4180 cfs_rq->h_nr_running++; 4181 4182 if (cfs_rq_throttled(cfs_rq)) 4183 break; 4184 4185 update_cfs_shares(cfs_rq); 4186 update_entity_load_avg(se, 1); 4187 } 4188 4189 if (!se) { 4190 update_rq_runnable_avg(rq, rq->nr_running); 4191 add_nr_running(rq, 1); 4192 } 4193 hrtick_update(rq); 4194 } 4195 4196 static void set_next_buddy(struct sched_entity *se); 4197 4198 /* 4199 * The dequeue_task method is called before nr_running is 4200 * decreased. We remove the task from the rbtree and 4201 * update the fair scheduling stats: 4202 */ 4203 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 4204 { 4205 struct cfs_rq *cfs_rq; 4206 struct sched_entity *se = &p->se; 4207 int task_sleep = flags & DEQUEUE_SLEEP; 4208 4209 for_each_sched_entity(se) { 4210 cfs_rq = cfs_rq_of(se); 4211 dequeue_entity(cfs_rq, se, flags); 4212 4213 /* 4214 * end evaluation on encountering a throttled cfs_rq 4215 * 4216 * note: in the case of encountering a throttled cfs_rq we will 4217 * post the final h_nr_running decrement below. 4218 */ 4219 if (cfs_rq_throttled(cfs_rq)) 4220 break; 4221 cfs_rq->h_nr_running--; 4222 4223 /* Don't dequeue parent if it has other entities besides us */ 4224 if (cfs_rq->load.weight) { 4225 /* 4226 * Bias pick_next to pick a task from this cfs_rq, as 4227 * p is sleeping when it is within its sched_slice. 4228 */ 4229 if (task_sleep && parent_entity(se)) 4230 set_next_buddy(parent_entity(se)); 4231 4232 /* avoid re-evaluating load for this entity */ 4233 se = parent_entity(se); 4234 break; 4235 } 4236 flags |= DEQUEUE_SLEEP; 4237 } 4238 4239 for_each_sched_entity(se) { 4240 cfs_rq = cfs_rq_of(se); 4241 cfs_rq->h_nr_running--; 4242 4243 if (cfs_rq_throttled(cfs_rq)) 4244 break; 4245 4246 update_cfs_shares(cfs_rq); 4247 update_entity_load_avg(se, 1); 4248 } 4249 4250 if (!se) { 4251 sub_nr_running(rq, 1); 4252 update_rq_runnable_avg(rq, 1); 4253 } 4254 hrtick_update(rq); 4255 } 4256 4257 #ifdef CONFIG_SMP 4258 /* Used instead of source_load when we know the type == 0 */ 4259 static unsigned long weighted_cpuload(const int cpu) 4260 { 4261 return cpu_rq(cpu)->cfs.runnable_load_avg; 4262 } 4263 4264 /* 4265 * Return a low guess at the load of a migration-source cpu weighted 4266 * according to the scheduling class and "nice" value. 4267 * 4268 * We want to under-estimate the load of migration sources, to 4269 * balance conservatively. 4270 */ 4271 static unsigned long source_load(int cpu, int type) 4272 { 4273 struct rq *rq = cpu_rq(cpu); 4274 unsigned long total = weighted_cpuload(cpu); 4275 4276 if (type == 0 || !sched_feat(LB_BIAS)) 4277 return total; 4278 4279 return min(rq->cpu_load[type-1], total); 4280 } 4281 4282 /* 4283 * Return a high guess at the load of a migration-target cpu weighted 4284 * according to the scheduling class and "nice" value. 4285 */ 4286 static unsigned long target_load(int cpu, int type) 4287 { 4288 struct rq *rq = cpu_rq(cpu); 4289 unsigned long total = weighted_cpuload(cpu); 4290 4291 if (type == 0 || !sched_feat(LB_BIAS)) 4292 return total; 4293 4294 return max(rq->cpu_load[type-1], total); 4295 } 4296 4297 static unsigned long capacity_of(int cpu) 4298 { 4299 return cpu_rq(cpu)->cpu_capacity; 4300 } 4301 4302 static unsigned long cpu_avg_load_per_task(int cpu) 4303 { 4304 struct rq *rq = cpu_rq(cpu); 4305 unsigned long nr_running = ACCESS_ONCE(rq->cfs.h_nr_running); 4306 unsigned long load_avg = rq->cfs.runnable_load_avg; 4307 4308 if (nr_running) 4309 return load_avg / nr_running; 4310 4311 return 0; 4312 } 4313 4314 static void record_wakee(struct task_struct *p) 4315 { 4316 /* 4317 * Rough decay (wiping) for cost saving, don't worry 4318 * about the boundary, really active task won't care 4319 * about the loss. 4320 */ 4321 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { 4322 current->wakee_flips >>= 1; 4323 current->wakee_flip_decay_ts = jiffies; 4324 } 4325 4326 if (current->last_wakee != p) { 4327 current->last_wakee = p; 4328 current->wakee_flips++; 4329 } 4330 } 4331 4332 static void task_waking_fair(struct task_struct *p) 4333 { 4334 struct sched_entity *se = &p->se; 4335 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4336 u64 min_vruntime; 4337 4338 #ifndef CONFIG_64BIT 4339 u64 min_vruntime_copy; 4340 4341 do { 4342 min_vruntime_copy = cfs_rq->min_vruntime_copy; 4343 smp_rmb(); 4344 min_vruntime = cfs_rq->min_vruntime; 4345 } while (min_vruntime != min_vruntime_copy); 4346 #else 4347 min_vruntime = cfs_rq->min_vruntime; 4348 #endif 4349 4350 se->vruntime -= min_vruntime; 4351 record_wakee(p); 4352 } 4353 4354 #ifdef CONFIG_FAIR_GROUP_SCHED 4355 /* 4356 * effective_load() calculates the load change as seen from the root_task_group 4357 * 4358 * Adding load to a group doesn't make a group heavier, but can cause movement 4359 * of group shares between cpus. Assuming the shares were perfectly aligned one 4360 * can calculate the shift in shares. 4361 * 4362 * Calculate the effective load difference if @wl is added (subtracted) to @tg 4363 * on this @cpu and results in a total addition (subtraction) of @wg to the 4364 * total group weight. 4365 * 4366 * Given a runqueue weight distribution (rw_i) we can compute a shares 4367 * distribution (s_i) using: 4368 * 4369 * s_i = rw_i / \Sum rw_j (1) 4370 * 4371 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and 4372 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting 4373 * shares distribution (s_i): 4374 * 4375 * rw_i = { 2, 4, 1, 0 } 4376 * s_i = { 2/7, 4/7, 1/7, 0 } 4377 * 4378 * As per wake_affine() we're interested in the load of two CPUs (the CPU the 4379 * task used to run on and the CPU the waker is running on), we need to 4380 * compute the effect of waking a task on either CPU and, in case of a sync 4381 * wakeup, compute the effect of the current task going to sleep. 4382 * 4383 * So for a change of @wl to the local @cpu with an overall group weight change 4384 * of @wl we can compute the new shares distribution (s'_i) using: 4385 * 4386 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) 4387 * 4388 * Suppose we're interested in CPUs 0 and 1, and want to compute the load 4389 * differences in waking a task to CPU 0. The additional task changes the 4390 * weight and shares distributions like: 4391 * 4392 * rw'_i = { 3, 4, 1, 0 } 4393 * s'_i = { 3/8, 4/8, 1/8, 0 } 4394 * 4395 * We can then compute the difference in effective weight by using: 4396 * 4397 * dw_i = S * (s'_i - s_i) (3) 4398 * 4399 * Where 'S' is the group weight as seen by its parent. 4400 * 4401 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) 4402 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - 4403 * 4/7) times the weight of the group. 4404 */ 4405 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 4406 { 4407 struct sched_entity *se = tg->se[cpu]; 4408 4409 if (!tg->parent) /* the trivial, non-cgroup case */ 4410 return wl; 4411 4412 for_each_sched_entity(se) { 4413 long w, W; 4414 4415 tg = se->my_q->tg; 4416 4417 /* 4418 * W = @wg + \Sum rw_j 4419 */ 4420 W = wg + calc_tg_weight(tg, se->my_q); 4421 4422 /* 4423 * w = rw_i + @wl 4424 */ 4425 w = se->my_q->load.weight + wl; 4426 4427 /* 4428 * wl = S * s'_i; see (2) 4429 */ 4430 if (W > 0 && w < W) 4431 wl = (w * (long)tg->shares) / W; 4432 else 4433 wl = tg->shares; 4434 4435 /* 4436 * Per the above, wl is the new se->load.weight value; since 4437 * those are clipped to [MIN_SHARES, ...) do so now. See 4438 * calc_cfs_shares(). 4439 */ 4440 if (wl < MIN_SHARES) 4441 wl = MIN_SHARES; 4442 4443 /* 4444 * wl = dw_i = S * (s'_i - s_i); see (3) 4445 */ 4446 wl -= se->load.weight; 4447 4448 /* 4449 * Recursively apply this logic to all parent groups to compute 4450 * the final effective load change on the root group. Since 4451 * only the @tg group gets extra weight, all parent groups can 4452 * only redistribute existing shares. @wl is the shift in shares 4453 * resulting from this level per the above. 4454 */ 4455 wg = 0; 4456 } 4457 4458 return wl; 4459 } 4460 #else 4461 4462 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 4463 { 4464 return wl; 4465 } 4466 4467 #endif 4468 4469 static int wake_wide(struct task_struct *p) 4470 { 4471 int factor = this_cpu_read(sd_llc_size); 4472 4473 /* 4474 * Yeah, it's the switching-frequency, could means many wakee or 4475 * rapidly switch, use factor here will just help to automatically 4476 * adjust the loose-degree, so bigger node will lead to more pull. 4477 */ 4478 if (p->wakee_flips > factor) { 4479 /* 4480 * wakee is somewhat hot, it needs certain amount of cpu 4481 * resource, so if waker is far more hot, prefer to leave 4482 * it alone. 4483 */ 4484 if (current->wakee_flips > (factor * p->wakee_flips)) 4485 return 1; 4486 } 4487 4488 return 0; 4489 } 4490 4491 static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) 4492 { 4493 s64 this_load, load; 4494 s64 this_eff_load, prev_eff_load; 4495 int idx, this_cpu, prev_cpu; 4496 struct task_group *tg; 4497 unsigned long weight; 4498 int balanced; 4499 4500 /* 4501 * If we wake multiple tasks be careful to not bounce 4502 * ourselves around too much. 4503 */ 4504 if (wake_wide(p)) 4505 return 0; 4506 4507 idx = sd->wake_idx; 4508 this_cpu = smp_processor_id(); 4509 prev_cpu = task_cpu(p); 4510 load = source_load(prev_cpu, idx); 4511 this_load = target_load(this_cpu, idx); 4512 4513 /* 4514 * If sync wakeup then subtract the (maximum possible) 4515 * effect of the currently running task from the load 4516 * of the current CPU: 4517 */ 4518 if (sync) { 4519 tg = task_group(current); 4520 weight = current->se.load.weight; 4521 4522 this_load += effective_load(tg, this_cpu, -weight, -weight); 4523 load += effective_load(tg, prev_cpu, 0, -weight); 4524 } 4525 4526 tg = task_group(p); 4527 weight = p->se.load.weight; 4528 4529 /* 4530 * In low-load situations, where prev_cpu is idle and this_cpu is idle 4531 * due to the sync cause above having dropped this_load to 0, we'll 4532 * always have an imbalance, but there's really nothing you can do 4533 * about that, so that's good too. 4534 * 4535 * Otherwise check if either cpus are near enough in load to allow this 4536 * task to be woken on this_cpu. 4537 */ 4538 this_eff_load = 100; 4539 this_eff_load *= capacity_of(prev_cpu); 4540 4541 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; 4542 prev_eff_load *= capacity_of(this_cpu); 4543 4544 if (this_load > 0) { 4545 this_eff_load *= this_load + 4546 effective_load(tg, this_cpu, weight, weight); 4547 4548 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); 4549 } 4550 4551 balanced = this_eff_load <= prev_eff_load; 4552 4553 schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); 4554 4555 if (!balanced) 4556 return 0; 4557 4558 schedstat_inc(sd, ttwu_move_affine); 4559 schedstat_inc(p, se.statistics.nr_wakeups_affine); 4560 4561 return 1; 4562 } 4563 4564 /* 4565 * find_idlest_group finds and returns the least busy CPU group within the 4566 * domain. 4567 */ 4568 static struct sched_group * 4569 find_idlest_group(struct sched_domain *sd, struct task_struct *p, 4570 int this_cpu, int sd_flag) 4571 { 4572 struct sched_group *idlest = NULL, *group = sd->groups; 4573 unsigned long min_load = ULONG_MAX, this_load = 0; 4574 int load_idx = sd->forkexec_idx; 4575 int imbalance = 100 + (sd->imbalance_pct-100)/2; 4576 4577 if (sd_flag & SD_BALANCE_WAKE) 4578 load_idx = sd->wake_idx; 4579 4580 do { 4581 unsigned long load, avg_load; 4582 int local_group; 4583 int i; 4584 4585 /* Skip over this group if it has no CPUs allowed */ 4586 if (!cpumask_intersects(sched_group_cpus(group), 4587 tsk_cpus_allowed(p))) 4588 continue; 4589 4590 local_group = cpumask_test_cpu(this_cpu, 4591 sched_group_cpus(group)); 4592 4593 /* Tally up the load of all CPUs in the group */ 4594 avg_load = 0; 4595 4596 for_each_cpu(i, sched_group_cpus(group)) { 4597 /* Bias balancing toward cpus of our domain */ 4598 if (local_group) 4599 load = source_load(i, load_idx); 4600 else 4601 load = target_load(i, load_idx); 4602 4603 avg_load += load; 4604 } 4605 4606 /* Adjust by relative CPU capacity of the group */ 4607 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / group->sgc->capacity; 4608 4609 if (local_group) { 4610 this_load = avg_load; 4611 } else if (avg_load < min_load) { 4612 min_load = avg_load; 4613 idlest = group; 4614 } 4615 } while (group = group->next, group != sd->groups); 4616 4617 if (!idlest || 100*this_load < imbalance*min_load) 4618 return NULL; 4619 return idlest; 4620 } 4621 4622 /* 4623 * find_idlest_cpu - find the idlest cpu among the cpus in group. 4624 */ 4625 static int 4626 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 4627 { 4628 unsigned long load, min_load = ULONG_MAX; 4629 unsigned int min_exit_latency = UINT_MAX; 4630 u64 latest_idle_timestamp = 0; 4631 int least_loaded_cpu = this_cpu; 4632 int shallowest_idle_cpu = -1; 4633 int i; 4634 4635 /* Traverse only the allowed CPUs */ 4636 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { 4637 if (idle_cpu(i)) { 4638 struct rq *rq = cpu_rq(i); 4639 struct cpuidle_state *idle = idle_get_state(rq); 4640 if (idle && idle->exit_latency < min_exit_latency) { 4641 /* 4642 * We give priority to a CPU whose idle state 4643 * has the smallest exit latency irrespective 4644 * of any idle timestamp. 4645 */ 4646 min_exit_latency = idle->exit_latency; 4647 latest_idle_timestamp = rq->idle_stamp; 4648 shallowest_idle_cpu = i; 4649 } else if ((!idle || idle->exit_latency == min_exit_latency) && 4650 rq->idle_stamp > latest_idle_timestamp) { 4651 /* 4652 * If equal or no active idle state, then 4653 * the most recently idled CPU might have 4654 * a warmer cache. 4655 */ 4656 latest_idle_timestamp = rq->idle_stamp; 4657 shallowest_idle_cpu = i; 4658 } 4659 } else if (shallowest_idle_cpu == -1) { 4660 load = weighted_cpuload(i); 4661 if (load < min_load || (load == min_load && i == this_cpu)) { 4662 min_load = load; 4663 least_loaded_cpu = i; 4664 } 4665 } 4666 } 4667 4668 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; 4669 } 4670 4671 /* 4672 * Try and locate an idle CPU in the sched_domain. 4673 */ 4674 static int select_idle_sibling(struct task_struct *p, int target) 4675 { 4676 struct sched_domain *sd; 4677 struct sched_group *sg; 4678 int i = task_cpu(p); 4679 4680 if (idle_cpu(target)) 4681 return target; 4682 4683 /* 4684 * If the prevous cpu is cache affine and idle, don't be stupid. 4685 */ 4686 if (i != target && cpus_share_cache(i, target) && idle_cpu(i)) 4687 return i; 4688 4689 /* 4690 * Otherwise, iterate the domains and find an elegible idle cpu. 4691 */ 4692 sd = rcu_dereference(per_cpu(sd_llc, target)); 4693 for_each_lower_domain(sd) { 4694 sg = sd->groups; 4695 do { 4696 if (!cpumask_intersects(sched_group_cpus(sg), 4697 tsk_cpus_allowed(p))) 4698 goto next; 4699 4700 for_each_cpu(i, sched_group_cpus(sg)) { 4701 if (i == target || !idle_cpu(i)) 4702 goto next; 4703 } 4704 4705 target = cpumask_first_and(sched_group_cpus(sg), 4706 tsk_cpus_allowed(p)); 4707 goto done; 4708 next: 4709 sg = sg->next; 4710 } while (sg != sd->groups); 4711 } 4712 done: 4713 return target; 4714 } 4715 4716 /* 4717 * select_task_rq_fair: Select target runqueue for the waking task in domains 4718 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, 4719 * SD_BALANCE_FORK, or SD_BALANCE_EXEC. 4720 * 4721 * Balances load by selecting the idlest cpu in the idlest group, or under 4722 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set. 4723 * 4724 * Returns the target cpu number. 4725 * 4726 * preempt must be disabled. 4727 */ 4728 static int 4729 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) 4730 { 4731 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; 4732 int cpu = smp_processor_id(); 4733 int new_cpu = cpu; 4734 int want_affine = 0; 4735 int sync = wake_flags & WF_SYNC; 4736 4737 if (sd_flag & SD_BALANCE_WAKE) 4738 want_affine = cpumask_test_cpu(cpu, tsk_cpus_allowed(p)); 4739 4740 rcu_read_lock(); 4741 for_each_domain(cpu, tmp) { 4742 if (!(tmp->flags & SD_LOAD_BALANCE)) 4743 continue; 4744 4745 /* 4746 * If both cpu and prev_cpu are part of this domain, 4747 * cpu is a valid SD_WAKE_AFFINE target. 4748 */ 4749 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && 4750 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { 4751 affine_sd = tmp; 4752 break; 4753 } 4754 4755 if (tmp->flags & sd_flag) 4756 sd = tmp; 4757 } 4758 4759 if (affine_sd && cpu != prev_cpu && wake_affine(affine_sd, p, sync)) 4760 prev_cpu = cpu; 4761 4762 if (sd_flag & SD_BALANCE_WAKE) { 4763 new_cpu = select_idle_sibling(p, prev_cpu); 4764 goto unlock; 4765 } 4766 4767 while (sd) { 4768 struct sched_group *group; 4769 int weight; 4770 4771 if (!(sd->flags & sd_flag)) { 4772 sd = sd->child; 4773 continue; 4774 } 4775 4776 group = find_idlest_group(sd, p, cpu, sd_flag); 4777 if (!group) { 4778 sd = sd->child; 4779 continue; 4780 } 4781 4782 new_cpu = find_idlest_cpu(group, p, cpu); 4783 if (new_cpu == -1 || new_cpu == cpu) { 4784 /* Now try balancing at a lower domain level of cpu */ 4785 sd = sd->child; 4786 continue; 4787 } 4788 4789 /* Now try balancing at a lower domain level of new_cpu */ 4790 cpu = new_cpu; 4791 weight = sd->span_weight; 4792 sd = NULL; 4793 for_each_domain(cpu, tmp) { 4794 if (weight <= tmp->span_weight) 4795 break; 4796 if (tmp->flags & sd_flag) 4797 sd = tmp; 4798 } 4799 /* while loop will break here if sd == NULL */ 4800 } 4801 unlock: 4802 rcu_read_unlock(); 4803 4804 return new_cpu; 4805 } 4806 4807 /* 4808 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and 4809 * cfs_rq_of(p) references at time of call are still valid and identify the 4810 * previous cpu. However, the caller only guarantees p->pi_lock is held; no 4811 * other assumptions, including the state of rq->lock, should be made. 4812 */ 4813 static void 4814 migrate_task_rq_fair(struct task_struct *p, int next_cpu) 4815 { 4816 struct sched_entity *se = &p->se; 4817 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4818 4819 /* 4820 * Load tracking: accumulate removed load so that it can be processed 4821 * when we next update owning cfs_rq under rq->lock. Tasks contribute 4822 * to blocked load iff they have a positive decay-count. It can never 4823 * be negative here since on-rq tasks have decay-count == 0. 4824 */ 4825 if (se->avg.decay_count) { 4826 se->avg.decay_count = -__synchronize_entity_decay(se); 4827 atomic_long_add(se->avg.load_avg_contrib, 4828 &cfs_rq->removed_load); 4829 } 4830 4831 /* We have migrated, no longer consider this task hot */ 4832 se->exec_start = 0; 4833 } 4834 #endif /* CONFIG_SMP */ 4835 4836 static unsigned long 4837 wakeup_gran(struct sched_entity *curr, struct sched_entity *se) 4838 { 4839 unsigned long gran = sysctl_sched_wakeup_granularity; 4840 4841 /* 4842 * Since its curr running now, convert the gran from real-time 4843 * to virtual-time in his units. 4844 * 4845 * By using 'se' instead of 'curr' we penalize light tasks, so 4846 * they get preempted easier. That is, if 'se' < 'curr' then 4847 * the resulting gran will be larger, therefore penalizing the 4848 * lighter, if otoh 'se' > 'curr' then the resulting gran will 4849 * be smaller, again penalizing the lighter task. 4850 * 4851 * This is especially important for buddies when the leftmost 4852 * task is higher priority than the buddy. 4853 */ 4854 return calc_delta_fair(gran, se); 4855 } 4856 4857 /* 4858 * Should 'se' preempt 'curr'. 4859 * 4860 * |s1 4861 * |s2 4862 * |s3 4863 * g 4864 * |<--->|c 4865 * 4866 * w(c, s1) = -1 4867 * w(c, s2) = 0 4868 * w(c, s3) = 1 4869 * 4870 */ 4871 static int 4872 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) 4873 { 4874 s64 gran, vdiff = curr->vruntime - se->vruntime; 4875 4876 if (vdiff <= 0) 4877 return -1; 4878 4879 gran = wakeup_gran(curr, se); 4880 if (vdiff > gran) 4881 return 1; 4882 4883 return 0; 4884 } 4885 4886 static void set_last_buddy(struct sched_entity *se) 4887 { 4888 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 4889 return; 4890 4891 for_each_sched_entity(se) 4892 cfs_rq_of(se)->last = se; 4893 } 4894 4895 static void set_next_buddy(struct sched_entity *se) 4896 { 4897 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 4898 return; 4899 4900 for_each_sched_entity(se) 4901 cfs_rq_of(se)->next = se; 4902 } 4903 4904 static void set_skip_buddy(struct sched_entity *se) 4905 { 4906 for_each_sched_entity(se) 4907 cfs_rq_of(se)->skip = se; 4908 } 4909 4910 /* 4911 * Preempt the current task with a newly woken task if needed: 4912 */ 4913 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 4914 { 4915 struct task_struct *curr = rq->curr; 4916 struct sched_entity *se = &curr->se, *pse = &p->se; 4917 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 4918 int scale = cfs_rq->nr_running >= sched_nr_latency; 4919 int next_buddy_marked = 0; 4920 4921 if (unlikely(se == pse)) 4922 return; 4923 4924 /* 4925 * This is possible from callers such as attach_tasks(), in which we 4926 * unconditionally check_prempt_curr() after an enqueue (which may have 4927 * lead to a throttle). This both saves work and prevents false 4928 * next-buddy nomination below. 4929 */ 4930 if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) 4931 return; 4932 4933 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { 4934 set_next_buddy(pse); 4935 next_buddy_marked = 1; 4936 } 4937 4938 /* 4939 * We can come here with TIF_NEED_RESCHED already set from new task 4940 * wake up path. 4941 * 4942 * Note: this also catches the edge-case of curr being in a throttled 4943 * group (e.g. via set_curr_task), since update_curr() (in the 4944 * enqueue of curr) will have resulted in resched being set. This 4945 * prevents us from potentially nominating it as a false LAST_BUDDY 4946 * below. 4947 */ 4948 if (test_tsk_need_resched(curr)) 4949 return; 4950 4951 /* Idle tasks are by definition preempted by non-idle tasks. */ 4952 if (unlikely(curr->policy == SCHED_IDLE) && 4953 likely(p->policy != SCHED_IDLE)) 4954 goto preempt; 4955 4956 /* 4957 * Batch and idle tasks do not preempt non-idle tasks (their preemption 4958 * is driven by the tick): 4959 */ 4960 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) 4961 return; 4962 4963 find_matching_se(&se, &pse); 4964 update_curr(cfs_rq_of(se)); 4965 BUG_ON(!pse); 4966 if (wakeup_preempt_entity(se, pse) == 1) { 4967 /* 4968 * Bias pick_next to pick the sched entity that is 4969 * triggering this preemption. 4970 */ 4971 if (!next_buddy_marked) 4972 set_next_buddy(pse); 4973 goto preempt; 4974 } 4975 4976 return; 4977 4978 preempt: 4979 resched_curr(rq); 4980 /* 4981 * Only set the backward buddy when the current task is still 4982 * on the rq. This can happen when a wakeup gets interleaved 4983 * with schedule on the ->pre_schedule() or idle_balance() 4984 * point, either of which can * drop the rq lock. 4985 * 4986 * Also, during early boot the idle thread is in the fair class, 4987 * for obvious reasons its a bad idea to schedule back to it. 4988 */ 4989 if (unlikely(!se->on_rq || curr == rq->idle)) 4990 return; 4991 4992 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) 4993 set_last_buddy(se); 4994 } 4995 4996 static struct task_struct * 4997 pick_next_task_fair(struct rq *rq, struct task_struct *prev) 4998 { 4999 struct cfs_rq *cfs_rq = &rq->cfs; 5000 struct sched_entity *se; 5001 struct task_struct *p; 5002 int new_tasks; 5003 5004 again: 5005 #ifdef CONFIG_FAIR_GROUP_SCHED 5006 if (!cfs_rq->nr_running) 5007 goto idle; 5008 5009 if (prev->sched_class != &fair_sched_class) 5010 goto simple; 5011 5012 /* 5013 * Because of the set_next_buddy() in dequeue_task_fair() it is rather 5014 * likely that a next task is from the same cgroup as the current. 5015 * 5016 * Therefore attempt to avoid putting and setting the entire cgroup 5017 * hierarchy, only change the part that actually changes. 5018 */ 5019 5020 do { 5021 struct sched_entity *curr = cfs_rq->curr; 5022 5023 /* 5024 * Since we got here without doing put_prev_entity() we also 5025 * have to consider cfs_rq->curr. If it is still a runnable 5026 * entity, update_curr() will update its vruntime, otherwise 5027 * forget we've ever seen it. 5028 */ 5029 if (curr && curr->on_rq) 5030 update_curr(cfs_rq); 5031 else 5032 curr = NULL; 5033 5034 /* 5035 * This call to check_cfs_rq_runtime() will do the throttle and 5036 * dequeue its entity in the parent(s). Therefore the 'simple' 5037 * nr_running test will indeed be correct. 5038 */ 5039 if (unlikely(check_cfs_rq_runtime(cfs_rq))) 5040 goto simple; 5041 5042 se = pick_next_entity(cfs_rq, curr); 5043 cfs_rq = group_cfs_rq(se); 5044 } while (cfs_rq); 5045 5046 p = task_of(se); 5047 5048 /* 5049 * Since we haven't yet done put_prev_entity and if the selected task 5050 * is a different task than we started out with, try and touch the 5051 * least amount of cfs_rqs. 5052 */ 5053 if (prev != p) { 5054 struct sched_entity *pse = &prev->se; 5055 5056 while (!(cfs_rq = is_same_group(se, pse))) { 5057 int se_depth = se->depth; 5058 int pse_depth = pse->depth; 5059 5060 if (se_depth <= pse_depth) { 5061 put_prev_entity(cfs_rq_of(pse), pse); 5062 pse = parent_entity(pse); 5063 } 5064 if (se_depth >= pse_depth) { 5065 set_next_entity(cfs_rq_of(se), se); 5066 se = parent_entity(se); 5067 } 5068 } 5069 5070 put_prev_entity(cfs_rq, pse); 5071 set_next_entity(cfs_rq, se); 5072 } 5073 5074 if (hrtick_enabled(rq)) 5075 hrtick_start_fair(rq, p); 5076 5077 return p; 5078 simple: 5079 cfs_rq = &rq->cfs; 5080 #endif 5081 5082 if (!cfs_rq->nr_running) 5083 goto idle; 5084 5085 put_prev_task(rq, prev); 5086 5087 do { 5088 se = pick_next_entity(cfs_rq, NULL); 5089 set_next_entity(cfs_rq, se); 5090 cfs_rq = group_cfs_rq(se); 5091 } while (cfs_rq); 5092 5093 p = task_of(se); 5094 5095 if (hrtick_enabled(rq)) 5096 hrtick_start_fair(rq, p); 5097 5098 return p; 5099 5100 idle: 5101 new_tasks = idle_balance(rq); 5102 /* 5103 * Because idle_balance() releases (and re-acquires) rq->lock, it is 5104 * possible for any higher priority task to appear. In that case we 5105 * must re-start the pick_next_entity() loop. 5106 */ 5107 if (new_tasks < 0) 5108 return RETRY_TASK; 5109 5110 if (new_tasks > 0) 5111 goto again; 5112 5113 return NULL; 5114 } 5115 5116 /* 5117 * Account for a descheduled task: 5118 */ 5119 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) 5120 { 5121 struct sched_entity *se = &prev->se; 5122 struct cfs_rq *cfs_rq; 5123 5124 for_each_sched_entity(se) { 5125 cfs_rq = cfs_rq_of(se); 5126 put_prev_entity(cfs_rq, se); 5127 } 5128 } 5129 5130 /* 5131 * sched_yield() is very simple 5132 * 5133 * The magic of dealing with the ->skip buddy is in pick_next_entity. 5134 */ 5135 static void yield_task_fair(struct rq *rq) 5136 { 5137 struct task_struct *curr = rq->curr; 5138 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 5139 struct sched_entity *se = &curr->se; 5140 5141 /* 5142 * Are we the only task in the tree? 5143 */ 5144 if (unlikely(rq->nr_running == 1)) 5145 return; 5146 5147 clear_buddies(cfs_rq, se); 5148 5149 if (curr->policy != SCHED_BATCH) { 5150 update_rq_clock(rq); 5151 /* 5152 * Update run-time statistics of the 'current'. 5153 */ 5154 update_curr(cfs_rq); 5155 /* 5156 * Tell update_rq_clock() that we've just updated, 5157 * so we don't do microscopic update in schedule() 5158 * and double the fastpath cost. 5159 */ 5160 rq->skip_clock_update = 1; 5161 } 5162 5163 set_skip_buddy(se); 5164 } 5165 5166 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) 5167 { 5168 struct sched_entity *se = &p->se; 5169 5170 /* throttled hierarchies are not runnable */ 5171 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) 5172 return false; 5173 5174 /* Tell the scheduler that we'd really like pse to run next. */ 5175 set_next_buddy(se); 5176 5177 yield_task_fair(rq); 5178 5179 return true; 5180 } 5181 5182 #ifdef CONFIG_SMP 5183 /************************************************** 5184 * Fair scheduling class load-balancing methods. 5185 * 5186 * BASICS 5187 * 5188 * The purpose of load-balancing is to achieve the same basic fairness the 5189 * per-cpu scheduler provides, namely provide a proportional amount of compute 5190 * time to each task. This is expressed in the following equation: 5191 * 5192 * W_i,n/P_i == W_j,n/P_j for all i,j (1) 5193 * 5194 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight 5195 * W_i,0 is defined as: 5196 * 5197 * W_i,0 = \Sum_j w_i,j (2) 5198 * 5199 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight 5200 * is derived from the nice value as per prio_to_weight[]. 5201 * 5202 * The weight average is an exponential decay average of the instantaneous 5203 * weight: 5204 * 5205 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) 5206 * 5207 * C_i is the compute capacity of cpu i, typically it is the 5208 * fraction of 'recent' time available for SCHED_OTHER task execution. But it 5209 * can also include other factors [XXX]. 5210 * 5211 * To achieve this balance we define a measure of imbalance which follows 5212 * directly from (1): 5213 * 5214 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) 5215 * 5216 * We them move tasks around to minimize the imbalance. In the continuous 5217 * function space it is obvious this converges, in the discrete case we get 5218 * a few fun cases generally called infeasible weight scenarios. 5219 * 5220 * [XXX expand on: 5221 * - infeasible weights; 5222 * - local vs global optima in the discrete case. ] 5223 * 5224 * 5225 * SCHED DOMAINS 5226 * 5227 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) 5228 * for all i,j solution, we create a tree of cpus that follows the hardware 5229 * topology where each level pairs two lower groups (or better). This results 5230 * in O(log n) layers. Furthermore we reduce the number of cpus going up the 5231 * tree to only the first of the previous level and we decrease the frequency 5232 * of load-balance at each level inv. proportional to the number of cpus in 5233 * the groups. 5234 * 5235 * This yields: 5236 * 5237 * log_2 n 1 n 5238 * \Sum { --- * --- * 2^i } = O(n) (5) 5239 * i = 0 2^i 2^i 5240 * `- size of each group 5241 * | | `- number of cpus doing load-balance 5242 * | `- freq 5243 * `- sum over all levels 5244 * 5245 * Coupled with a limit on how many tasks we can migrate every balance pass, 5246 * this makes (5) the runtime complexity of the balancer. 5247 * 5248 * An important property here is that each CPU is still (indirectly) connected 5249 * to every other cpu in at most O(log n) steps: 5250 * 5251 * The adjacency matrix of the resulting graph is given by: 5252 * 5253 * log_2 n 5254 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) 5255 * k = 0 5256 * 5257 * And you'll find that: 5258 * 5259 * A^(log_2 n)_i,j != 0 for all i,j (7) 5260 * 5261 * Showing there's indeed a path between every cpu in at most O(log n) steps. 5262 * The task movement gives a factor of O(m), giving a convergence complexity 5263 * of: 5264 * 5265 * O(nm log n), n := nr_cpus, m := nr_tasks (8) 5266 * 5267 * 5268 * WORK CONSERVING 5269 * 5270 * In order to avoid CPUs going idle while there's still work to do, new idle 5271 * balancing is more aggressive and has the newly idle cpu iterate up the domain 5272 * tree itself instead of relying on other CPUs to bring it work. 5273 * 5274 * This adds some complexity to both (5) and (8) but it reduces the total idle 5275 * time. 5276 * 5277 * [XXX more?] 5278 * 5279 * 5280 * CGROUPS 5281 * 5282 * Cgroups make a horror show out of (2), instead of a simple sum we get: 5283 * 5284 * s_k,i 5285 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) 5286 * S_k 5287 * 5288 * Where 5289 * 5290 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) 5291 * 5292 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i. 5293 * 5294 * The big problem is S_k, its a global sum needed to compute a local (W_i) 5295 * property. 5296 * 5297 * [XXX write more on how we solve this.. _after_ merging pjt's patches that 5298 * rewrite all of this once again.] 5299 */ 5300 5301 static unsigned long __read_mostly max_load_balance_interval = HZ/10; 5302 5303 enum fbq_type { regular, remote, all }; 5304 5305 #define LBF_ALL_PINNED 0x01 5306 #define LBF_NEED_BREAK 0x02 5307 #define LBF_DST_PINNED 0x04 5308 #define LBF_SOME_PINNED 0x08 5309 5310 struct lb_env { 5311 struct sched_domain *sd; 5312 5313 struct rq *src_rq; 5314 int src_cpu; 5315 5316 int dst_cpu; 5317 struct rq *dst_rq; 5318 5319 struct cpumask *dst_grpmask; 5320 int new_dst_cpu; 5321 enum cpu_idle_type idle; 5322 long imbalance; 5323 /* The set of CPUs under consideration for load-balancing */ 5324 struct cpumask *cpus; 5325 5326 unsigned int flags; 5327 5328 unsigned int loop; 5329 unsigned int loop_break; 5330 unsigned int loop_max; 5331 5332 enum fbq_type fbq_type; 5333 struct list_head tasks; 5334 }; 5335 5336 /* 5337 * Is this task likely cache-hot: 5338 */ 5339 static int task_hot(struct task_struct *p, struct lb_env *env) 5340 { 5341 s64 delta; 5342 5343 lockdep_assert_held(&env->src_rq->lock); 5344 5345 if (p->sched_class != &fair_sched_class) 5346 return 0; 5347 5348 if (unlikely(p->policy == SCHED_IDLE)) 5349 return 0; 5350 5351 /* 5352 * Buddy candidates are cache hot: 5353 */ 5354 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running && 5355 (&p->se == cfs_rq_of(&p->se)->next || 5356 &p->se == cfs_rq_of(&p->se)->last)) 5357 return 1; 5358 5359 if (sysctl_sched_migration_cost == -1) 5360 return 1; 5361 if (sysctl_sched_migration_cost == 0) 5362 return 0; 5363 5364 delta = rq_clock_task(env->src_rq) - p->se.exec_start; 5365 5366 return delta < (s64)sysctl_sched_migration_cost; 5367 } 5368 5369 #ifdef CONFIG_NUMA_BALANCING 5370 /* Returns true if the destination node has incurred more faults */ 5371 static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env) 5372 { 5373 struct numa_group *numa_group = rcu_dereference(p->numa_group); 5374 int src_nid, dst_nid; 5375 5376 if (!sched_feat(NUMA_FAVOUR_HIGHER) || !p->numa_faults || 5377 !(env->sd->flags & SD_NUMA)) { 5378 return false; 5379 } 5380 5381 src_nid = cpu_to_node(env->src_cpu); 5382 dst_nid = cpu_to_node(env->dst_cpu); 5383 5384 if (src_nid == dst_nid) 5385 return false; 5386 5387 if (numa_group) { 5388 /* Task is already in the group's interleave set. */ 5389 if (node_isset(src_nid, numa_group->active_nodes)) 5390 return false; 5391 5392 /* Task is moving into the group's interleave set. */ 5393 if (node_isset(dst_nid, numa_group->active_nodes)) 5394 return true; 5395 5396 return group_faults(p, dst_nid) > group_faults(p, src_nid); 5397 } 5398 5399 /* Encourage migration to the preferred node. */ 5400 if (dst_nid == p->numa_preferred_nid) 5401 return true; 5402 5403 return task_faults(p, dst_nid) > task_faults(p, src_nid); 5404 } 5405 5406 5407 static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env) 5408 { 5409 struct numa_group *numa_group = rcu_dereference(p->numa_group); 5410 int src_nid, dst_nid; 5411 5412 if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER)) 5413 return false; 5414 5415 if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) 5416 return false; 5417 5418 src_nid = cpu_to_node(env->src_cpu); 5419 dst_nid = cpu_to_node(env->dst_cpu); 5420 5421 if (src_nid == dst_nid) 5422 return false; 5423 5424 if (numa_group) { 5425 /* Task is moving within/into the group's interleave set. */ 5426 if (node_isset(dst_nid, numa_group->active_nodes)) 5427 return false; 5428 5429 /* Task is moving out of the group's interleave set. */ 5430 if (node_isset(src_nid, numa_group->active_nodes)) 5431 return true; 5432 5433 return group_faults(p, dst_nid) < group_faults(p, src_nid); 5434 } 5435 5436 /* Migrating away from the preferred node is always bad. */ 5437 if (src_nid == p->numa_preferred_nid) 5438 return true; 5439 5440 return task_faults(p, dst_nid) < task_faults(p, src_nid); 5441 } 5442 5443 #else 5444 static inline bool migrate_improves_locality(struct task_struct *p, 5445 struct lb_env *env) 5446 { 5447 return false; 5448 } 5449 5450 static inline bool migrate_degrades_locality(struct task_struct *p, 5451 struct lb_env *env) 5452 { 5453 return false; 5454 } 5455 #endif 5456 5457 /* 5458 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? 5459 */ 5460 static 5461 int can_migrate_task(struct task_struct *p, struct lb_env *env) 5462 { 5463 int tsk_cache_hot = 0; 5464 5465 lockdep_assert_held(&env->src_rq->lock); 5466 5467 /* 5468 * We do not migrate tasks that are: 5469 * 1) throttled_lb_pair, or 5470 * 2) cannot be migrated to this CPU due to cpus_allowed, or 5471 * 3) running (obviously), or 5472 * 4) are cache-hot on their current CPU. 5473 */ 5474 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) 5475 return 0; 5476 5477 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { 5478 int cpu; 5479 5480 schedstat_inc(p, se.statistics.nr_failed_migrations_affine); 5481 5482 env->flags |= LBF_SOME_PINNED; 5483 5484 /* 5485 * Remember if this task can be migrated to any other cpu in 5486 * our sched_group. We may want to revisit it if we couldn't 5487 * meet load balance goals by pulling other tasks on src_cpu. 5488 * 5489 * Also avoid computing new_dst_cpu if we have already computed 5490 * one in current iteration. 5491 */ 5492 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED)) 5493 return 0; 5494 5495 /* Prevent to re-select dst_cpu via env's cpus */ 5496 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { 5497 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) { 5498 env->flags |= LBF_DST_PINNED; 5499 env->new_dst_cpu = cpu; 5500 break; 5501 } 5502 } 5503 5504 return 0; 5505 } 5506 5507 /* Record that we found atleast one task that could run on dst_cpu */ 5508 env->flags &= ~LBF_ALL_PINNED; 5509 5510 if (task_running(env->src_rq, p)) { 5511 schedstat_inc(p, se.statistics.nr_failed_migrations_running); 5512 return 0; 5513 } 5514 5515 /* 5516 * Aggressive migration if: 5517 * 1) destination numa is preferred 5518 * 2) task is cache cold, or 5519 * 3) too many balance attempts have failed. 5520 */ 5521 tsk_cache_hot = task_hot(p, env); 5522 if (!tsk_cache_hot) 5523 tsk_cache_hot = migrate_degrades_locality(p, env); 5524 5525 if (migrate_improves_locality(p, env) || !tsk_cache_hot || 5526 env->sd->nr_balance_failed > env->sd->cache_nice_tries) { 5527 if (tsk_cache_hot) { 5528 schedstat_inc(env->sd, lb_hot_gained[env->idle]); 5529 schedstat_inc(p, se.statistics.nr_forced_migrations); 5530 } 5531 return 1; 5532 } 5533 5534 schedstat_inc(p, se.statistics.nr_failed_migrations_hot); 5535 return 0; 5536 } 5537 5538 /* 5539 * detach_task() -- detach the task for the migration specified in env 5540 */ 5541 static void detach_task(struct task_struct *p, struct lb_env *env) 5542 { 5543 lockdep_assert_held(&env->src_rq->lock); 5544 5545 deactivate_task(env->src_rq, p, 0); 5546 p->on_rq = TASK_ON_RQ_MIGRATING; 5547 set_task_cpu(p, env->dst_cpu); 5548 } 5549 5550 /* 5551 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as 5552 * part of active balancing operations within "domain". 5553 * 5554 * Returns a task if successful and NULL otherwise. 5555 */ 5556 static struct task_struct *detach_one_task(struct lb_env *env) 5557 { 5558 struct task_struct *p, *n; 5559 5560 lockdep_assert_held(&env->src_rq->lock); 5561 5562 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) { 5563 if (!can_migrate_task(p, env)) 5564 continue; 5565 5566 detach_task(p, env); 5567 5568 /* 5569 * Right now, this is only the second place where 5570 * lb_gained[env->idle] is updated (other is detach_tasks) 5571 * so we can safely collect stats here rather than 5572 * inside detach_tasks(). 5573 */ 5574 schedstat_inc(env->sd, lb_gained[env->idle]); 5575 return p; 5576 } 5577 return NULL; 5578 } 5579 5580 static const unsigned int sched_nr_migrate_break = 32; 5581 5582 /* 5583 * detach_tasks() -- tries to detach up to imbalance weighted load from 5584 * busiest_rq, as part of a balancing operation within domain "sd". 5585 * 5586 * Returns number of detached tasks if successful and 0 otherwise. 5587 */ 5588 static int detach_tasks(struct lb_env *env) 5589 { 5590 struct list_head *tasks = &env->src_rq->cfs_tasks; 5591 struct task_struct *p; 5592 unsigned long load; 5593 int detached = 0; 5594 5595 lockdep_assert_held(&env->src_rq->lock); 5596 5597 if (env->imbalance <= 0) 5598 return 0; 5599 5600 while (!list_empty(tasks)) { 5601 p = list_first_entry(tasks, struct task_struct, se.group_node); 5602 5603 env->loop++; 5604 /* We've more or less seen every task there is, call it quits */ 5605 if (env->loop > env->loop_max) 5606 break; 5607 5608 /* take a breather every nr_migrate tasks */ 5609 if (env->loop > env->loop_break) { 5610 env->loop_break += sched_nr_migrate_break; 5611 env->flags |= LBF_NEED_BREAK; 5612 break; 5613 } 5614 5615 if (!can_migrate_task(p, env)) 5616 goto next; 5617 5618 load = task_h_load(p); 5619 5620 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) 5621 goto next; 5622 5623 if ((load / 2) > env->imbalance) 5624 goto next; 5625 5626 detach_task(p, env); 5627 list_add(&p->se.group_node, &env->tasks); 5628 5629 detached++; 5630 env->imbalance -= load; 5631 5632 #ifdef CONFIG_PREEMPT 5633 /* 5634 * NEWIDLE balancing is a source of latency, so preemptible 5635 * kernels will stop after the first task is detached to minimize 5636 * the critical section. 5637 */ 5638 if (env->idle == CPU_NEWLY_IDLE) 5639 break; 5640 #endif 5641 5642 /* 5643 * We only want to steal up to the prescribed amount of 5644 * weighted load. 5645 */ 5646 if (env->imbalance <= 0) 5647 break; 5648 5649 continue; 5650 next: 5651 list_move_tail(&p->se.group_node, tasks); 5652 } 5653 5654 /* 5655 * Right now, this is one of only two places we collect this stat 5656 * so we can safely collect detach_one_task() stats here rather 5657 * than inside detach_one_task(). 5658 */ 5659 schedstat_add(env->sd, lb_gained[env->idle], detached); 5660 5661 return detached; 5662 } 5663 5664 /* 5665 * attach_task() -- attach the task detached by detach_task() to its new rq. 5666 */ 5667 static void attach_task(struct rq *rq, struct task_struct *p) 5668 { 5669 lockdep_assert_held(&rq->lock); 5670 5671 BUG_ON(task_rq(p) != rq); 5672 p->on_rq = TASK_ON_RQ_QUEUED; 5673 activate_task(rq, p, 0); 5674 check_preempt_curr(rq, p, 0); 5675 } 5676 5677 /* 5678 * attach_one_task() -- attaches the task returned from detach_one_task() to 5679 * its new rq. 5680 */ 5681 static void attach_one_task(struct rq *rq, struct task_struct *p) 5682 { 5683 raw_spin_lock(&rq->lock); 5684 attach_task(rq, p); 5685 raw_spin_unlock(&rq->lock); 5686 } 5687 5688 /* 5689 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their 5690 * new rq. 5691 */ 5692 static void attach_tasks(struct lb_env *env) 5693 { 5694 struct list_head *tasks = &env->tasks; 5695 struct task_struct *p; 5696 5697 raw_spin_lock(&env->dst_rq->lock); 5698 5699 while (!list_empty(tasks)) { 5700 p = list_first_entry(tasks, struct task_struct, se.group_node); 5701 list_del_init(&p->se.group_node); 5702 5703 attach_task(env->dst_rq, p); 5704 } 5705 5706 raw_spin_unlock(&env->dst_rq->lock); 5707 } 5708 5709 #ifdef CONFIG_FAIR_GROUP_SCHED 5710 /* 5711 * update tg->load_weight by folding this cpu's load_avg 5712 */ 5713 static void __update_blocked_averages_cpu(struct task_group *tg, int cpu) 5714 { 5715 struct sched_entity *se = tg->se[cpu]; 5716 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu]; 5717 5718 /* throttled entities do not contribute to load */ 5719 if (throttled_hierarchy(cfs_rq)) 5720 return; 5721 5722 update_cfs_rq_blocked_load(cfs_rq, 1); 5723 5724 if (se) { 5725 update_entity_load_avg(se, 1); 5726 /* 5727 * We pivot on our runnable average having decayed to zero for 5728 * list removal. This generally implies that all our children 5729 * have also been removed (modulo rounding error or bandwidth 5730 * control); however, such cases are rare and we can fix these 5731 * at enqueue. 5732 * 5733 * TODO: fix up out-of-order children on enqueue. 5734 */ 5735 if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running) 5736 list_del_leaf_cfs_rq(cfs_rq); 5737 } else { 5738 struct rq *rq = rq_of(cfs_rq); 5739 update_rq_runnable_avg(rq, rq->nr_running); 5740 } 5741 } 5742 5743 static void update_blocked_averages(int cpu) 5744 { 5745 struct rq *rq = cpu_rq(cpu); 5746 struct cfs_rq *cfs_rq; 5747 unsigned long flags; 5748 5749 raw_spin_lock_irqsave(&rq->lock, flags); 5750 update_rq_clock(rq); 5751 /* 5752 * Iterates the task_group tree in a bottom up fashion, see 5753 * list_add_leaf_cfs_rq() for details. 5754 */ 5755 for_each_leaf_cfs_rq(rq, cfs_rq) { 5756 /* 5757 * Note: We may want to consider periodically releasing 5758 * rq->lock about these updates so that creating many task 5759 * groups does not result in continually extending hold time. 5760 */ 5761 __update_blocked_averages_cpu(cfs_rq->tg, rq->cpu); 5762 } 5763 5764 raw_spin_unlock_irqrestore(&rq->lock, flags); 5765 } 5766 5767 /* 5768 * Compute the hierarchical load factor for cfs_rq and all its ascendants. 5769 * This needs to be done in a top-down fashion because the load of a child 5770 * group is a fraction of its parents load. 5771 */ 5772 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) 5773 { 5774 struct rq *rq = rq_of(cfs_rq); 5775 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; 5776 unsigned long now = jiffies; 5777 unsigned long load; 5778 5779 if (cfs_rq->last_h_load_update == now) 5780 return; 5781 5782 cfs_rq->h_load_next = NULL; 5783 for_each_sched_entity(se) { 5784 cfs_rq = cfs_rq_of(se); 5785 cfs_rq->h_load_next = se; 5786 if (cfs_rq->last_h_load_update == now) 5787 break; 5788 } 5789 5790 if (!se) { 5791 cfs_rq->h_load = cfs_rq->runnable_load_avg; 5792 cfs_rq->last_h_load_update = now; 5793 } 5794 5795 while ((se = cfs_rq->h_load_next) != NULL) { 5796 load = cfs_rq->h_load; 5797 load = div64_ul(load * se->avg.load_avg_contrib, 5798 cfs_rq->runnable_load_avg + 1); 5799 cfs_rq = group_cfs_rq(se); 5800 cfs_rq->h_load = load; 5801 cfs_rq->last_h_load_update = now; 5802 } 5803 } 5804 5805 static unsigned long task_h_load(struct task_struct *p) 5806 { 5807 struct cfs_rq *cfs_rq = task_cfs_rq(p); 5808 5809 update_cfs_rq_h_load(cfs_rq); 5810 return div64_ul(p->se.avg.load_avg_contrib * cfs_rq->h_load, 5811 cfs_rq->runnable_load_avg + 1); 5812 } 5813 #else 5814 static inline void update_blocked_averages(int cpu) 5815 { 5816 } 5817 5818 static unsigned long task_h_load(struct task_struct *p) 5819 { 5820 return p->se.avg.load_avg_contrib; 5821 } 5822 #endif 5823 5824 /********** Helpers for find_busiest_group ************************/ 5825 5826 enum group_type { 5827 group_other = 0, 5828 group_imbalanced, 5829 group_overloaded, 5830 }; 5831 5832 /* 5833 * sg_lb_stats - stats of a sched_group required for load_balancing 5834 */ 5835 struct sg_lb_stats { 5836 unsigned long avg_load; /*Avg load across the CPUs of the group */ 5837 unsigned long group_load; /* Total load over the CPUs of the group */ 5838 unsigned long sum_weighted_load; /* Weighted load of group's tasks */ 5839 unsigned long load_per_task; 5840 unsigned long group_capacity; 5841 unsigned int sum_nr_running; /* Nr tasks running in the group */ 5842 unsigned int group_capacity_factor; 5843 unsigned int idle_cpus; 5844 unsigned int group_weight; 5845 enum group_type group_type; 5846 int group_has_free_capacity; 5847 #ifdef CONFIG_NUMA_BALANCING 5848 unsigned int nr_numa_running; 5849 unsigned int nr_preferred_running; 5850 #endif 5851 }; 5852 5853 /* 5854 * sd_lb_stats - Structure to store the statistics of a sched_domain 5855 * during load balancing. 5856 */ 5857 struct sd_lb_stats { 5858 struct sched_group *busiest; /* Busiest group in this sd */ 5859 struct sched_group *local; /* Local group in this sd */ 5860 unsigned long total_load; /* Total load of all groups in sd */ 5861 unsigned long total_capacity; /* Total capacity of all groups in sd */ 5862 unsigned long avg_load; /* Average load across all groups in sd */ 5863 5864 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ 5865 struct sg_lb_stats local_stat; /* Statistics of the local group */ 5866 }; 5867 5868 static inline void init_sd_lb_stats(struct sd_lb_stats *sds) 5869 { 5870 /* 5871 * Skimp on the clearing to avoid duplicate work. We can avoid clearing 5872 * local_stat because update_sg_lb_stats() does a full clear/assignment. 5873 * We must however clear busiest_stat::avg_load because 5874 * update_sd_pick_busiest() reads this before assignment. 5875 */ 5876 *sds = (struct sd_lb_stats){ 5877 .busiest = NULL, 5878 .local = NULL, 5879 .total_load = 0UL, 5880 .total_capacity = 0UL, 5881 .busiest_stat = { 5882 .avg_load = 0UL, 5883 .sum_nr_running = 0, 5884 .group_type = group_other, 5885 }, 5886 }; 5887 } 5888 5889 /** 5890 * get_sd_load_idx - Obtain the load index for a given sched domain. 5891 * @sd: The sched_domain whose load_idx is to be obtained. 5892 * @idle: The idle status of the CPU for whose sd load_idx is obtained. 5893 * 5894 * Return: The load index. 5895 */ 5896 static inline int get_sd_load_idx(struct sched_domain *sd, 5897 enum cpu_idle_type idle) 5898 { 5899 int load_idx; 5900 5901 switch (idle) { 5902 case CPU_NOT_IDLE: 5903 load_idx = sd->busy_idx; 5904 break; 5905 5906 case CPU_NEWLY_IDLE: 5907 load_idx = sd->newidle_idx; 5908 break; 5909 default: 5910 load_idx = sd->idle_idx; 5911 break; 5912 } 5913 5914 return load_idx; 5915 } 5916 5917 static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu) 5918 { 5919 return SCHED_CAPACITY_SCALE; 5920 } 5921 5922 unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu) 5923 { 5924 return default_scale_capacity(sd, cpu); 5925 } 5926 5927 static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu) 5928 { 5929 if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1)) 5930 return sd->smt_gain / sd->span_weight; 5931 5932 return SCHED_CAPACITY_SCALE; 5933 } 5934 5935 unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) 5936 { 5937 return default_scale_cpu_capacity(sd, cpu); 5938 } 5939 5940 static unsigned long scale_rt_capacity(int cpu) 5941 { 5942 struct rq *rq = cpu_rq(cpu); 5943 u64 total, available, age_stamp, avg; 5944 s64 delta; 5945 5946 /* 5947 * Since we're reading these variables without serialization make sure 5948 * we read them once before doing sanity checks on them. 5949 */ 5950 age_stamp = ACCESS_ONCE(rq->age_stamp); 5951 avg = ACCESS_ONCE(rq->rt_avg); 5952 5953 delta = rq_clock(rq) - age_stamp; 5954 if (unlikely(delta < 0)) 5955 delta = 0; 5956 5957 total = sched_avg_period() + delta; 5958 5959 if (unlikely(total < avg)) { 5960 /* Ensures that capacity won't end up being negative */ 5961 available = 0; 5962 } else { 5963 available = total - avg; 5964 } 5965 5966 if (unlikely((s64)total < SCHED_CAPACITY_SCALE)) 5967 total = SCHED_CAPACITY_SCALE; 5968 5969 total >>= SCHED_CAPACITY_SHIFT; 5970 5971 return div_u64(available, total); 5972 } 5973 5974 static void update_cpu_capacity(struct sched_domain *sd, int cpu) 5975 { 5976 unsigned long capacity = SCHED_CAPACITY_SCALE; 5977 struct sched_group *sdg = sd->groups; 5978 5979 if (sched_feat(ARCH_CAPACITY)) 5980 capacity *= arch_scale_cpu_capacity(sd, cpu); 5981 else 5982 capacity *= default_scale_cpu_capacity(sd, cpu); 5983 5984 capacity >>= SCHED_CAPACITY_SHIFT; 5985 5986 sdg->sgc->capacity_orig = capacity; 5987 5988 if (sched_feat(ARCH_CAPACITY)) 5989 capacity *= arch_scale_freq_capacity(sd, cpu); 5990 else 5991 capacity *= default_scale_capacity(sd, cpu); 5992 5993 capacity >>= SCHED_CAPACITY_SHIFT; 5994 5995 capacity *= scale_rt_capacity(cpu); 5996 capacity >>= SCHED_CAPACITY_SHIFT; 5997 5998 if (!capacity) 5999 capacity = 1; 6000 6001 cpu_rq(cpu)->cpu_capacity = capacity; 6002 sdg->sgc->capacity = capacity; 6003 } 6004 6005 void update_group_capacity(struct sched_domain *sd, int cpu) 6006 { 6007 struct sched_domain *child = sd->child; 6008 struct sched_group *group, *sdg = sd->groups; 6009 unsigned long capacity, capacity_orig; 6010 unsigned long interval; 6011 6012 interval = msecs_to_jiffies(sd->balance_interval); 6013 interval = clamp(interval, 1UL, max_load_balance_interval); 6014 sdg->sgc->next_update = jiffies + interval; 6015 6016 if (!child) { 6017 update_cpu_capacity(sd, cpu); 6018 return; 6019 } 6020 6021 capacity_orig = capacity = 0; 6022 6023 if (child->flags & SD_OVERLAP) { 6024 /* 6025 * SD_OVERLAP domains cannot assume that child groups 6026 * span the current group. 6027 */ 6028 6029 for_each_cpu(cpu, sched_group_cpus(sdg)) { 6030 struct sched_group_capacity *sgc; 6031 struct rq *rq = cpu_rq(cpu); 6032 6033 /* 6034 * build_sched_domains() -> init_sched_groups_capacity() 6035 * gets here before we've attached the domains to the 6036 * runqueues. 6037 * 6038 * Use capacity_of(), which is set irrespective of domains 6039 * in update_cpu_capacity(). 6040 * 6041 * This avoids capacity/capacity_orig from being 0 and 6042 * causing divide-by-zero issues on boot. 6043 * 6044 * Runtime updates will correct capacity_orig. 6045 */ 6046 if (unlikely(!rq->sd)) { 6047 capacity_orig += capacity_of(cpu); 6048 capacity += capacity_of(cpu); 6049 continue; 6050 } 6051 6052 sgc = rq->sd->groups->sgc; 6053 capacity_orig += sgc->capacity_orig; 6054 capacity += sgc->capacity; 6055 } 6056 } else { 6057 /* 6058 * !SD_OVERLAP domains can assume that child groups 6059 * span the current group. 6060 */ 6061 6062 group = child->groups; 6063 do { 6064 capacity_orig += group->sgc->capacity_orig; 6065 capacity += group->sgc->capacity; 6066 group = group->next; 6067 } while (group != child->groups); 6068 } 6069 6070 sdg->sgc->capacity_orig = capacity_orig; 6071 sdg->sgc->capacity = capacity; 6072 } 6073 6074 /* 6075 * Try and fix up capacity for tiny siblings, this is needed when 6076 * things like SD_ASYM_PACKING need f_b_g to select another sibling 6077 * which on its own isn't powerful enough. 6078 * 6079 * See update_sd_pick_busiest() and check_asym_packing(). 6080 */ 6081 static inline int 6082 fix_small_capacity(struct sched_domain *sd, struct sched_group *group) 6083 { 6084 /* 6085 * Only siblings can have significantly less than SCHED_CAPACITY_SCALE 6086 */ 6087 if (!(sd->flags & SD_SHARE_CPUCAPACITY)) 6088 return 0; 6089 6090 /* 6091 * If ~90% of the cpu_capacity is still there, we're good. 6092 */ 6093 if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29) 6094 return 1; 6095 6096 return 0; 6097 } 6098 6099 /* 6100 * Group imbalance indicates (and tries to solve) the problem where balancing 6101 * groups is inadequate due to tsk_cpus_allowed() constraints. 6102 * 6103 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a 6104 * cpumask covering 1 cpu of the first group and 3 cpus of the second group. 6105 * Something like: 6106 * 6107 * { 0 1 2 3 } { 4 5 6 7 } 6108 * * * * * 6109 * 6110 * If we were to balance group-wise we'd place two tasks in the first group and 6111 * two tasks in the second group. Clearly this is undesired as it will overload 6112 * cpu 3 and leave one of the cpus in the second group unused. 6113 * 6114 * The current solution to this issue is detecting the skew in the first group 6115 * by noticing the lower domain failed to reach balance and had difficulty 6116 * moving tasks due to affinity constraints. 6117 * 6118 * When this is so detected; this group becomes a candidate for busiest; see 6119 * update_sd_pick_busiest(). And calculate_imbalance() and 6120 * find_busiest_group() avoid some of the usual balance conditions to allow it 6121 * to create an effective group imbalance. 6122 * 6123 * This is a somewhat tricky proposition since the next run might not find the 6124 * group imbalance and decide the groups need to be balanced again. A most 6125 * subtle and fragile situation. 6126 */ 6127 6128 static inline int sg_imbalanced(struct sched_group *group) 6129 { 6130 return group->sgc->imbalance; 6131 } 6132 6133 /* 6134 * Compute the group capacity factor. 6135 * 6136 * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by 6137 * first dividing out the smt factor and computing the actual number of cores 6138 * and limit unit capacity with that. 6139 */ 6140 static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group) 6141 { 6142 unsigned int capacity_factor, smt, cpus; 6143 unsigned int capacity, capacity_orig; 6144 6145 capacity = group->sgc->capacity; 6146 capacity_orig = group->sgc->capacity_orig; 6147 cpus = group->group_weight; 6148 6149 /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */ 6150 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig); 6151 capacity_factor = cpus / smt; /* cores */ 6152 6153 capacity_factor = min_t(unsigned, 6154 capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE)); 6155 if (!capacity_factor) 6156 capacity_factor = fix_small_capacity(env->sd, group); 6157 6158 return capacity_factor; 6159 } 6160 6161 static enum group_type 6162 group_classify(struct sched_group *group, struct sg_lb_stats *sgs) 6163 { 6164 if (sgs->sum_nr_running > sgs->group_capacity_factor) 6165 return group_overloaded; 6166 6167 if (sg_imbalanced(group)) 6168 return group_imbalanced; 6169 6170 return group_other; 6171 } 6172 6173 /** 6174 * update_sg_lb_stats - Update sched_group's statistics for load balancing. 6175 * @env: The load balancing environment. 6176 * @group: sched_group whose statistics are to be updated. 6177 * @load_idx: Load index of sched_domain of this_cpu for load calc. 6178 * @local_group: Does group contain this_cpu. 6179 * @sgs: variable to hold the statistics for this group. 6180 * @overload: Indicate more than one runnable task for any CPU. 6181 */ 6182 static inline void update_sg_lb_stats(struct lb_env *env, 6183 struct sched_group *group, int load_idx, 6184 int local_group, struct sg_lb_stats *sgs, 6185 bool *overload) 6186 { 6187 unsigned long load; 6188 int i; 6189 6190 memset(sgs, 0, sizeof(*sgs)); 6191 6192 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 6193 struct rq *rq = cpu_rq(i); 6194 6195 /* Bias balancing toward cpus of our domain */ 6196 if (local_group) 6197 load = target_load(i, load_idx); 6198 else 6199 load = source_load(i, load_idx); 6200 6201 sgs->group_load += load; 6202 sgs->sum_nr_running += rq->cfs.h_nr_running; 6203 6204 if (rq->nr_running > 1) 6205 *overload = true; 6206 6207 #ifdef CONFIG_NUMA_BALANCING 6208 sgs->nr_numa_running += rq->nr_numa_running; 6209 sgs->nr_preferred_running += rq->nr_preferred_running; 6210 #endif 6211 sgs->sum_weighted_load += weighted_cpuload(i); 6212 if (idle_cpu(i)) 6213 sgs->idle_cpus++; 6214 } 6215 6216 /* Adjust by relative CPU capacity of the group */ 6217 sgs->group_capacity = group->sgc->capacity; 6218 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; 6219 6220 if (sgs->sum_nr_running) 6221 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; 6222 6223 sgs->group_weight = group->group_weight; 6224 sgs->group_capacity_factor = sg_capacity_factor(env, group); 6225 sgs->group_type = group_classify(group, sgs); 6226 6227 if (sgs->group_capacity_factor > sgs->sum_nr_running) 6228 sgs->group_has_free_capacity = 1; 6229 } 6230 6231 /** 6232 * update_sd_pick_busiest - return 1 on busiest group 6233 * @env: The load balancing environment. 6234 * @sds: sched_domain statistics 6235 * @sg: sched_group candidate to be checked for being the busiest 6236 * @sgs: sched_group statistics 6237 * 6238 * Determine if @sg is a busier group than the previously selected 6239 * busiest group. 6240 * 6241 * Return: %true if @sg is a busier group than the previously selected 6242 * busiest group. %false otherwise. 6243 */ 6244 static bool update_sd_pick_busiest(struct lb_env *env, 6245 struct sd_lb_stats *sds, 6246 struct sched_group *sg, 6247 struct sg_lb_stats *sgs) 6248 { 6249 struct sg_lb_stats *busiest = &sds->busiest_stat; 6250 6251 if (sgs->group_type > busiest->group_type) 6252 return true; 6253 6254 if (sgs->group_type < busiest->group_type) 6255 return false; 6256 6257 if (sgs->avg_load <= busiest->avg_load) 6258 return false; 6259 6260 /* This is the busiest node in its class. */ 6261 if (!(env->sd->flags & SD_ASYM_PACKING)) 6262 return true; 6263 6264 /* 6265 * ASYM_PACKING needs to move all the work to the lowest 6266 * numbered CPUs in the group, therefore mark all groups 6267 * higher than ourself as busy. 6268 */ 6269 if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) { 6270 if (!sds->busiest) 6271 return true; 6272 6273 if (group_first_cpu(sds->busiest) > group_first_cpu(sg)) 6274 return true; 6275 } 6276 6277 return false; 6278 } 6279 6280 #ifdef CONFIG_NUMA_BALANCING 6281 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 6282 { 6283 if (sgs->sum_nr_running > sgs->nr_numa_running) 6284 return regular; 6285 if (sgs->sum_nr_running > sgs->nr_preferred_running) 6286 return remote; 6287 return all; 6288 } 6289 6290 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 6291 { 6292 if (rq->nr_running > rq->nr_numa_running) 6293 return regular; 6294 if (rq->nr_running > rq->nr_preferred_running) 6295 return remote; 6296 return all; 6297 } 6298 #else 6299 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 6300 { 6301 return all; 6302 } 6303 6304 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 6305 { 6306 return regular; 6307 } 6308 #endif /* CONFIG_NUMA_BALANCING */ 6309 6310 /** 6311 * update_sd_lb_stats - Update sched_domain's statistics for load balancing. 6312 * @env: The load balancing environment. 6313 * @sds: variable to hold the statistics for this sched_domain. 6314 */ 6315 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) 6316 { 6317 struct sched_domain *child = env->sd->child; 6318 struct sched_group *sg = env->sd->groups; 6319 struct sg_lb_stats tmp_sgs; 6320 int load_idx, prefer_sibling = 0; 6321 bool overload = false; 6322 6323 if (child && child->flags & SD_PREFER_SIBLING) 6324 prefer_sibling = 1; 6325 6326 load_idx = get_sd_load_idx(env->sd, env->idle); 6327 6328 do { 6329 struct sg_lb_stats *sgs = &tmp_sgs; 6330 int local_group; 6331 6332 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg)); 6333 if (local_group) { 6334 sds->local = sg; 6335 sgs = &sds->local_stat; 6336 6337 if (env->idle != CPU_NEWLY_IDLE || 6338 time_after_eq(jiffies, sg->sgc->next_update)) 6339 update_group_capacity(env->sd, env->dst_cpu); 6340 } 6341 6342 update_sg_lb_stats(env, sg, load_idx, local_group, sgs, 6343 &overload); 6344 6345 if (local_group) 6346 goto next_group; 6347 6348 /* 6349 * In case the child domain prefers tasks go to siblings 6350 * first, lower the sg capacity factor to one so that we'll try 6351 * and move all the excess tasks away. We lower the capacity 6352 * of a group only if the local group has the capacity to fit 6353 * these excess tasks, i.e. nr_running < group_capacity_factor. The 6354 * extra check prevents the case where you always pull from the 6355 * heaviest group when it is already under-utilized (possible 6356 * with a large weight task outweighs the tasks on the system). 6357 */ 6358 if (prefer_sibling && sds->local && 6359 sds->local_stat.group_has_free_capacity) { 6360 sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U); 6361 sgs->group_type = group_classify(sg, sgs); 6362 } 6363 6364 if (update_sd_pick_busiest(env, sds, sg, sgs)) { 6365 sds->busiest = sg; 6366 sds->busiest_stat = *sgs; 6367 } 6368 6369 next_group: 6370 /* Now, start updating sd_lb_stats */ 6371 sds->total_load += sgs->group_load; 6372 sds->total_capacity += sgs->group_capacity; 6373 6374 sg = sg->next; 6375 } while (sg != env->sd->groups); 6376 6377 if (env->sd->flags & SD_NUMA) 6378 env->fbq_type = fbq_classify_group(&sds->busiest_stat); 6379 6380 if (!env->sd->parent) { 6381 /* update overload indicator if we are at root domain */ 6382 if (env->dst_rq->rd->overload != overload) 6383 env->dst_rq->rd->overload = overload; 6384 } 6385 6386 } 6387 6388 /** 6389 * check_asym_packing - Check to see if the group is packed into the 6390 * sched doman. 6391 * 6392 * This is primarily intended to used at the sibling level. Some 6393 * cores like POWER7 prefer to use lower numbered SMT threads. In the 6394 * case of POWER7, it can move to lower SMT modes only when higher 6395 * threads are idle. When in lower SMT modes, the threads will 6396 * perform better since they share less core resources. Hence when we 6397 * have idle threads, we want them to be the higher ones. 6398 * 6399 * This packing function is run on idle threads. It checks to see if 6400 * the busiest CPU in this domain (core in the P7 case) has a higher 6401 * CPU number than the packing function is being run on. Here we are 6402 * assuming lower CPU number will be equivalent to lower a SMT thread 6403 * number. 6404 * 6405 * Return: 1 when packing is required and a task should be moved to 6406 * this CPU. The amount of the imbalance is returned in *imbalance. 6407 * 6408 * @env: The load balancing environment. 6409 * @sds: Statistics of the sched_domain which is to be packed 6410 */ 6411 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) 6412 { 6413 int busiest_cpu; 6414 6415 if (!(env->sd->flags & SD_ASYM_PACKING)) 6416 return 0; 6417 6418 if (!sds->busiest) 6419 return 0; 6420 6421 busiest_cpu = group_first_cpu(sds->busiest); 6422 if (env->dst_cpu > busiest_cpu) 6423 return 0; 6424 6425 env->imbalance = DIV_ROUND_CLOSEST( 6426 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, 6427 SCHED_CAPACITY_SCALE); 6428 6429 return 1; 6430 } 6431 6432 /** 6433 * fix_small_imbalance - Calculate the minor imbalance that exists 6434 * amongst the groups of a sched_domain, during 6435 * load balancing. 6436 * @env: The load balancing environment. 6437 * @sds: Statistics of the sched_domain whose imbalance is to be calculated. 6438 */ 6439 static inline 6440 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 6441 { 6442 unsigned long tmp, capa_now = 0, capa_move = 0; 6443 unsigned int imbn = 2; 6444 unsigned long scaled_busy_load_per_task; 6445 struct sg_lb_stats *local, *busiest; 6446 6447 local = &sds->local_stat; 6448 busiest = &sds->busiest_stat; 6449 6450 if (!local->sum_nr_running) 6451 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu); 6452 else if (busiest->load_per_task > local->load_per_task) 6453 imbn = 1; 6454 6455 scaled_busy_load_per_task = 6456 (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 6457 busiest->group_capacity; 6458 6459 if (busiest->avg_load + scaled_busy_load_per_task >= 6460 local->avg_load + (scaled_busy_load_per_task * imbn)) { 6461 env->imbalance = busiest->load_per_task; 6462 return; 6463 } 6464 6465 /* 6466 * OK, we don't have enough imbalance to justify moving tasks, 6467 * however we may be able to increase total CPU capacity used by 6468 * moving them. 6469 */ 6470 6471 capa_now += busiest->group_capacity * 6472 min(busiest->load_per_task, busiest->avg_load); 6473 capa_now += local->group_capacity * 6474 min(local->load_per_task, local->avg_load); 6475 capa_now /= SCHED_CAPACITY_SCALE; 6476 6477 /* Amount of load we'd subtract */ 6478 if (busiest->avg_load > scaled_busy_load_per_task) { 6479 capa_move += busiest->group_capacity * 6480 min(busiest->load_per_task, 6481 busiest->avg_load - scaled_busy_load_per_task); 6482 } 6483 6484 /* Amount of load we'd add */ 6485 if (busiest->avg_load * busiest->group_capacity < 6486 busiest->load_per_task * SCHED_CAPACITY_SCALE) { 6487 tmp = (busiest->avg_load * busiest->group_capacity) / 6488 local->group_capacity; 6489 } else { 6490 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 6491 local->group_capacity; 6492 } 6493 capa_move += local->group_capacity * 6494 min(local->load_per_task, local->avg_load + tmp); 6495 capa_move /= SCHED_CAPACITY_SCALE; 6496 6497 /* Move if we gain throughput */ 6498 if (capa_move > capa_now) 6499 env->imbalance = busiest->load_per_task; 6500 } 6501 6502 /** 6503 * calculate_imbalance - Calculate the amount of imbalance present within the 6504 * groups of a given sched_domain during load balance. 6505 * @env: load balance environment 6506 * @sds: statistics of the sched_domain whose imbalance is to be calculated. 6507 */ 6508 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 6509 { 6510 unsigned long max_pull, load_above_capacity = ~0UL; 6511 struct sg_lb_stats *local, *busiest; 6512 6513 local = &sds->local_stat; 6514 busiest = &sds->busiest_stat; 6515 6516 if (busiest->group_type == group_imbalanced) { 6517 /* 6518 * In the group_imb case we cannot rely on group-wide averages 6519 * to ensure cpu-load equilibrium, look at wider averages. XXX 6520 */ 6521 busiest->load_per_task = 6522 min(busiest->load_per_task, sds->avg_load); 6523 } 6524 6525 /* 6526 * In the presence of smp nice balancing, certain scenarios can have 6527 * max load less than avg load(as we skip the groups at or below 6528 * its cpu_capacity, while calculating max_load..) 6529 */ 6530 if (busiest->avg_load <= sds->avg_load || 6531 local->avg_load >= sds->avg_load) { 6532 env->imbalance = 0; 6533 return fix_small_imbalance(env, sds); 6534 } 6535 6536 /* 6537 * If there aren't any idle cpus, avoid creating some. 6538 */ 6539 if (busiest->group_type == group_overloaded && 6540 local->group_type == group_overloaded) { 6541 load_above_capacity = 6542 (busiest->sum_nr_running - busiest->group_capacity_factor); 6543 6544 load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE); 6545 load_above_capacity /= busiest->group_capacity; 6546 } 6547 6548 /* 6549 * We're trying to get all the cpus to the average_load, so we don't 6550 * want to push ourselves above the average load, nor do we wish to 6551 * reduce the max loaded cpu below the average load. At the same time, 6552 * we also don't want to reduce the group load below the group capacity 6553 * (so that we can implement power-savings policies etc). Thus we look 6554 * for the minimum possible imbalance. 6555 */ 6556 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity); 6557 6558 /* How much load to actually move to equalise the imbalance */ 6559 env->imbalance = min( 6560 max_pull * busiest->group_capacity, 6561 (sds->avg_load - local->avg_load) * local->group_capacity 6562 ) / SCHED_CAPACITY_SCALE; 6563 6564 /* 6565 * if *imbalance is less than the average load per runnable task 6566 * there is no guarantee that any tasks will be moved so we'll have 6567 * a think about bumping its value to force at least one task to be 6568 * moved 6569 */ 6570 if (env->imbalance < busiest->load_per_task) 6571 return fix_small_imbalance(env, sds); 6572 } 6573 6574 /******* find_busiest_group() helpers end here *********************/ 6575 6576 /** 6577 * find_busiest_group - Returns the busiest group within the sched_domain 6578 * if there is an imbalance. If there isn't an imbalance, and 6579 * the user has opted for power-savings, it returns a group whose 6580 * CPUs can be put to idle by rebalancing those tasks elsewhere, if 6581 * such a group exists. 6582 * 6583 * Also calculates the amount of weighted load which should be moved 6584 * to restore balance. 6585 * 6586 * @env: The load balancing environment. 6587 * 6588 * Return: - The busiest group if imbalance exists. 6589 * - If no imbalance and user has opted for power-savings balance, 6590 * return the least loaded group whose CPUs can be 6591 * put to idle by rebalancing its tasks onto our group. 6592 */ 6593 static struct sched_group *find_busiest_group(struct lb_env *env) 6594 { 6595 struct sg_lb_stats *local, *busiest; 6596 struct sd_lb_stats sds; 6597 6598 init_sd_lb_stats(&sds); 6599 6600 /* 6601 * Compute the various statistics relavent for load balancing at 6602 * this level. 6603 */ 6604 update_sd_lb_stats(env, &sds); 6605 local = &sds.local_stat; 6606 busiest = &sds.busiest_stat; 6607 6608 if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) && 6609 check_asym_packing(env, &sds)) 6610 return sds.busiest; 6611 6612 /* There is no busy sibling group to pull tasks from */ 6613 if (!sds.busiest || busiest->sum_nr_running == 0) 6614 goto out_balanced; 6615 6616 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load) 6617 / sds.total_capacity; 6618 6619 /* 6620 * If the busiest group is imbalanced the below checks don't 6621 * work because they assume all things are equal, which typically 6622 * isn't true due to cpus_allowed constraints and the like. 6623 */ 6624 if (busiest->group_type == group_imbalanced) 6625 goto force_balance; 6626 6627 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ 6628 if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity && 6629 !busiest->group_has_free_capacity) 6630 goto force_balance; 6631 6632 /* 6633 * If the local group is busier than the selected busiest group 6634 * don't try and pull any tasks. 6635 */ 6636 if (local->avg_load >= busiest->avg_load) 6637 goto out_balanced; 6638 6639 /* 6640 * Don't pull any tasks if this group is already above the domain 6641 * average load. 6642 */ 6643 if (local->avg_load >= sds.avg_load) 6644 goto out_balanced; 6645 6646 if (env->idle == CPU_IDLE) { 6647 /* 6648 * This cpu is idle. If the busiest group is not overloaded 6649 * and there is no imbalance between this and busiest group 6650 * wrt idle cpus, it is balanced. The imbalance becomes 6651 * significant if the diff is greater than 1 otherwise we 6652 * might end up to just move the imbalance on another group 6653 */ 6654 if ((busiest->group_type != group_overloaded) && 6655 (local->idle_cpus <= (busiest->idle_cpus + 1))) 6656 goto out_balanced; 6657 } else { 6658 /* 6659 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use 6660 * imbalance_pct to be conservative. 6661 */ 6662 if (100 * busiest->avg_load <= 6663 env->sd->imbalance_pct * local->avg_load) 6664 goto out_balanced; 6665 } 6666 6667 force_balance: 6668 /* Looks like there is an imbalance. Compute it */ 6669 calculate_imbalance(env, &sds); 6670 return sds.busiest; 6671 6672 out_balanced: 6673 env->imbalance = 0; 6674 return NULL; 6675 } 6676 6677 /* 6678 * find_busiest_queue - find the busiest runqueue among the cpus in group. 6679 */ 6680 static struct rq *find_busiest_queue(struct lb_env *env, 6681 struct sched_group *group) 6682 { 6683 struct rq *busiest = NULL, *rq; 6684 unsigned long busiest_load = 0, busiest_capacity = 1; 6685 int i; 6686 6687 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 6688 unsigned long capacity, capacity_factor, wl; 6689 enum fbq_type rt; 6690 6691 rq = cpu_rq(i); 6692 rt = fbq_classify_rq(rq); 6693 6694 /* 6695 * We classify groups/runqueues into three groups: 6696 * - regular: there are !numa tasks 6697 * - remote: there are numa tasks that run on the 'wrong' node 6698 * - all: there is no distinction 6699 * 6700 * In order to avoid migrating ideally placed numa tasks, 6701 * ignore those when there's better options. 6702 * 6703 * If we ignore the actual busiest queue to migrate another 6704 * task, the next balance pass can still reduce the busiest 6705 * queue by moving tasks around inside the node. 6706 * 6707 * If we cannot move enough load due to this classification 6708 * the next pass will adjust the group classification and 6709 * allow migration of more tasks. 6710 * 6711 * Both cases only affect the total convergence complexity. 6712 */ 6713 if (rt > env->fbq_type) 6714 continue; 6715 6716 capacity = capacity_of(i); 6717 capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE); 6718 if (!capacity_factor) 6719 capacity_factor = fix_small_capacity(env->sd, group); 6720 6721 wl = weighted_cpuload(i); 6722 6723 /* 6724 * When comparing with imbalance, use weighted_cpuload() 6725 * which is not scaled with the cpu capacity. 6726 */ 6727 if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance) 6728 continue; 6729 6730 /* 6731 * For the load comparisons with the other cpu's, consider 6732 * the weighted_cpuload() scaled with the cpu capacity, so 6733 * that the load can be moved away from the cpu that is 6734 * potentially running at a lower capacity. 6735 * 6736 * Thus we're looking for max(wl_i / capacity_i), crosswise 6737 * multiplication to rid ourselves of the division works out 6738 * to: wl_i * capacity_j > wl_j * capacity_i; where j is 6739 * our previous maximum. 6740 */ 6741 if (wl * busiest_capacity > busiest_load * capacity) { 6742 busiest_load = wl; 6743 busiest_capacity = capacity; 6744 busiest = rq; 6745 } 6746 } 6747 6748 return busiest; 6749 } 6750 6751 /* 6752 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but 6753 * so long as it is large enough. 6754 */ 6755 #define MAX_PINNED_INTERVAL 512 6756 6757 /* Working cpumask for load_balance and load_balance_newidle. */ 6758 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); 6759 6760 static int need_active_balance(struct lb_env *env) 6761 { 6762 struct sched_domain *sd = env->sd; 6763 6764 if (env->idle == CPU_NEWLY_IDLE) { 6765 6766 /* 6767 * ASYM_PACKING needs to force migrate tasks from busy but 6768 * higher numbered CPUs in order to pack all tasks in the 6769 * lowest numbered CPUs. 6770 */ 6771 if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) 6772 return 1; 6773 } 6774 6775 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); 6776 } 6777 6778 static int active_load_balance_cpu_stop(void *data); 6779 6780 static int should_we_balance(struct lb_env *env) 6781 { 6782 struct sched_group *sg = env->sd->groups; 6783 struct cpumask *sg_cpus, *sg_mask; 6784 int cpu, balance_cpu = -1; 6785 6786 /* 6787 * In the newly idle case, we will allow all the cpu's 6788 * to do the newly idle load balance. 6789 */ 6790 if (env->idle == CPU_NEWLY_IDLE) 6791 return 1; 6792 6793 sg_cpus = sched_group_cpus(sg); 6794 sg_mask = sched_group_mask(sg); 6795 /* Try to find first idle cpu */ 6796 for_each_cpu_and(cpu, sg_cpus, env->cpus) { 6797 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu)) 6798 continue; 6799 6800 balance_cpu = cpu; 6801 break; 6802 } 6803 6804 if (balance_cpu == -1) 6805 balance_cpu = group_balance_cpu(sg); 6806 6807 /* 6808 * First idle cpu or the first cpu(busiest) in this sched group 6809 * is eligible for doing load balancing at this and above domains. 6810 */ 6811 return balance_cpu == env->dst_cpu; 6812 } 6813 6814 /* 6815 * Check this_cpu to ensure it is balanced within domain. Attempt to move 6816 * tasks if there is an imbalance. 6817 */ 6818 static int load_balance(int this_cpu, struct rq *this_rq, 6819 struct sched_domain *sd, enum cpu_idle_type idle, 6820 int *continue_balancing) 6821 { 6822 int ld_moved, cur_ld_moved, active_balance = 0; 6823 struct sched_domain *sd_parent = sd->parent; 6824 struct sched_group *group; 6825 struct rq *busiest; 6826 unsigned long flags; 6827 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); 6828 6829 struct lb_env env = { 6830 .sd = sd, 6831 .dst_cpu = this_cpu, 6832 .dst_rq = this_rq, 6833 .dst_grpmask = sched_group_cpus(sd->groups), 6834 .idle = idle, 6835 .loop_break = sched_nr_migrate_break, 6836 .cpus = cpus, 6837 .fbq_type = all, 6838 .tasks = LIST_HEAD_INIT(env.tasks), 6839 }; 6840 6841 /* 6842 * For NEWLY_IDLE load_balancing, we don't need to consider 6843 * other cpus in our group 6844 */ 6845 if (idle == CPU_NEWLY_IDLE) 6846 env.dst_grpmask = NULL; 6847 6848 cpumask_copy(cpus, cpu_active_mask); 6849 6850 schedstat_inc(sd, lb_count[idle]); 6851 6852 redo: 6853 if (!should_we_balance(&env)) { 6854 *continue_balancing = 0; 6855 goto out_balanced; 6856 } 6857 6858 group = find_busiest_group(&env); 6859 if (!group) { 6860 schedstat_inc(sd, lb_nobusyg[idle]); 6861 goto out_balanced; 6862 } 6863 6864 busiest = find_busiest_queue(&env, group); 6865 if (!busiest) { 6866 schedstat_inc(sd, lb_nobusyq[idle]); 6867 goto out_balanced; 6868 } 6869 6870 BUG_ON(busiest == env.dst_rq); 6871 6872 schedstat_add(sd, lb_imbalance[idle], env.imbalance); 6873 6874 ld_moved = 0; 6875 if (busiest->nr_running > 1) { 6876 /* 6877 * Attempt to move tasks. If find_busiest_group has found 6878 * an imbalance but busiest->nr_running <= 1, the group is 6879 * still unbalanced. ld_moved simply stays zero, so it is 6880 * correctly treated as an imbalance. 6881 */ 6882 env.flags |= LBF_ALL_PINNED; 6883 env.src_cpu = busiest->cpu; 6884 env.src_rq = busiest; 6885 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); 6886 6887 more_balance: 6888 raw_spin_lock_irqsave(&busiest->lock, flags); 6889 6890 /* 6891 * cur_ld_moved - load moved in current iteration 6892 * ld_moved - cumulative load moved across iterations 6893 */ 6894 cur_ld_moved = detach_tasks(&env); 6895 6896 /* 6897 * We've detached some tasks from busiest_rq. Every 6898 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely 6899 * unlock busiest->lock, and we are able to be sure 6900 * that nobody can manipulate the tasks in parallel. 6901 * See task_rq_lock() family for the details. 6902 */ 6903 6904 raw_spin_unlock(&busiest->lock); 6905 6906 if (cur_ld_moved) { 6907 attach_tasks(&env); 6908 ld_moved += cur_ld_moved; 6909 } 6910 6911 local_irq_restore(flags); 6912 6913 if (env.flags & LBF_NEED_BREAK) { 6914 env.flags &= ~LBF_NEED_BREAK; 6915 goto more_balance; 6916 } 6917 6918 /* 6919 * Revisit (affine) tasks on src_cpu that couldn't be moved to 6920 * us and move them to an alternate dst_cpu in our sched_group 6921 * where they can run. The upper limit on how many times we 6922 * iterate on same src_cpu is dependent on number of cpus in our 6923 * sched_group. 6924 * 6925 * This changes load balance semantics a bit on who can move 6926 * load to a given_cpu. In addition to the given_cpu itself 6927 * (or a ilb_cpu acting on its behalf where given_cpu is 6928 * nohz-idle), we now have balance_cpu in a position to move 6929 * load to given_cpu. In rare situations, this may cause 6930 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding 6931 * _independently_ and at _same_ time to move some load to 6932 * given_cpu) causing exceess load to be moved to given_cpu. 6933 * This however should not happen so much in practice and 6934 * moreover subsequent load balance cycles should correct the 6935 * excess load moved. 6936 */ 6937 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { 6938 6939 /* Prevent to re-select dst_cpu via env's cpus */ 6940 cpumask_clear_cpu(env.dst_cpu, env.cpus); 6941 6942 env.dst_rq = cpu_rq(env.new_dst_cpu); 6943 env.dst_cpu = env.new_dst_cpu; 6944 env.flags &= ~LBF_DST_PINNED; 6945 env.loop = 0; 6946 env.loop_break = sched_nr_migrate_break; 6947 6948 /* 6949 * Go back to "more_balance" rather than "redo" since we 6950 * need to continue with same src_cpu. 6951 */ 6952 goto more_balance; 6953 } 6954 6955 /* 6956 * We failed to reach balance because of affinity. 6957 */ 6958 if (sd_parent) { 6959 int *group_imbalance = &sd_parent->groups->sgc->imbalance; 6960 6961 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) 6962 *group_imbalance = 1; 6963 } 6964 6965 /* All tasks on this runqueue were pinned by CPU affinity */ 6966 if (unlikely(env.flags & LBF_ALL_PINNED)) { 6967 cpumask_clear_cpu(cpu_of(busiest), cpus); 6968 if (!cpumask_empty(cpus)) { 6969 env.loop = 0; 6970 env.loop_break = sched_nr_migrate_break; 6971 goto redo; 6972 } 6973 goto out_all_pinned; 6974 } 6975 } 6976 6977 if (!ld_moved) { 6978 schedstat_inc(sd, lb_failed[idle]); 6979 /* 6980 * Increment the failure counter only on periodic balance. 6981 * We do not want newidle balance, which can be very 6982 * frequent, pollute the failure counter causing 6983 * excessive cache_hot migrations and active balances. 6984 */ 6985 if (idle != CPU_NEWLY_IDLE) 6986 sd->nr_balance_failed++; 6987 6988 if (need_active_balance(&env)) { 6989 raw_spin_lock_irqsave(&busiest->lock, flags); 6990 6991 /* don't kick the active_load_balance_cpu_stop, 6992 * if the curr task on busiest cpu can't be 6993 * moved to this_cpu 6994 */ 6995 if (!cpumask_test_cpu(this_cpu, 6996 tsk_cpus_allowed(busiest->curr))) { 6997 raw_spin_unlock_irqrestore(&busiest->lock, 6998 flags); 6999 env.flags |= LBF_ALL_PINNED; 7000 goto out_one_pinned; 7001 } 7002 7003 /* 7004 * ->active_balance synchronizes accesses to 7005 * ->active_balance_work. Once set, it's cleared 7006 * only after active load balance is finished. 7007 */ 7008 if (!busiest->active_balance) { 7009 busiest->active_balance = 1; 7010 busiest->push_cpu = this_cpu; 7011 active_balance = 1; 7012 } 7013 raw_spin_unlock_irqrestore(&busiest->lock, flags); 7014 7015 if (active_balance) { 7016 stop_one_cpu_nowait(cpu_of(busiest), 7017 active_load_balance_cpu_stop, busiest, 7018 &busiest->active_balance_work); 7019 } 7020 7021 /* 7022 * We've kicked active balancing, reset the failure 7023 * counter. 7024 */ 7025 sd->nr_balance_failed = sd->cache_nice_tries+1; 7026 } 7027 } else 7028 sd->nr_balance_failed = 0; 7029 7030 if (likely(!active_balance)) { 7031 /* We were unbalanced, so reset the balancing interval */ 7032 sd->balance_interval = sd->min_interval; 7033 } else { 7034 /* 7035 * If we've begun active balancing, start to back off. This 7036 * case may not be covered by the all_pinned logic if there 7037 * is only 1 task on the busy runqueue (because we don't call 7038 * detach_tasks). 7039 */ 7040 if (sd->balance_interval < sd->max_interval) 7041 sd->balance_interval *= 2; 7042 } 7043 7044 goto out; 7045 7046 out_balanced: 7047 /* 7048 * We reach balance although we may have faced some affinity 7049 * constraints. Clear the imbalance flag if it was set. 7050 */ 7051 if (sd_parent) { 7052 int *group_imbalance = &sd_parent->groups->sgc->imbalance; 7053 7054 if (*group_imbalance) 7055 *group_imbalance = 0; 7056 } 7057 7058 out_all_pinned: 7059 /* 7060 * We reach balance because all tasks are pinned at this level so 7061 * we can't migrate them. Let the imbalance flag set so parent level 7062 * can try to migrate them. 7063 */ 7064 schedstat_inc(sd, lb_balanced[idle]); 7065 7066 sd->nr_balance_failed = 0; 7067 7068 out_one_pinned: 7069 /* tune up the balancing interval */ 7070 if (((env.flags & LBF_ALL_PINNED) && 7071 sd->balance_interval < MAX_PINNED_INTERVAL) || 7072 (sd->balance_interval < sd->max_interval)) 7073 sd->balance_interval *= 2; 7074 7075 ld_moved = 0; 7076 out: 7077 return ld_moved; 7078 } 7079 7080 static inline unsigned long 7081 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) 7082 { 7083 unsigned long interval = sd->balance_interval; 7084 7085 if (cpu_busy) 7086 interval *= sd->busy_factor; 7087 7088 /* scale ms to jiffies */ 7089 interval = msecs_to_jiffies(interval); 7090 interval = clamp(interval, 1UL, max_load_balance_interval); 7091 7092 return interval; 7093 } 7094 7095 static inline void 7096 update_next_balance(struct sched_domain *sd, int cpu_busy, unsigned long *next_balance) 7097 { 7098 unsigned long interval, next; 7099 7100 interval = get_sd_balance_interval(sd, cpu_busy); 7101 next = sd->last_balance + interval; 7102 7103 if (time_after(*next_balance, next)) 7104 *next_balance = next; 7105 } 7106 7107 /* 7108 * idle_balance is called by schedule() if this_cpu is about to become 7109 * idle. Attempts to pull tasks from other CPUs. 7110 */ 7111 static int idle_balance(struct rq *this_rq) 7112 { 7113 unsigned long next_balance = jiffies + HZ; 7114 int this_cpu = this_rq->cpu; 7115 struct sched_domain *sd; 7116 int pulled_task = 0; 7117 u64 curr_cost = 0; 7118 7119 idle_enter_fair(this_rq); 7120 7121 /* 7122 * We must set idle_stamp _before_ calling idle_balance(), such that we 7123 * measure the duration of idle_balance() as idle time. 7124 */ 7125 this_rq->idle_stamp = rq_clock(this_rq); 7126 7127 if (this_rq->avg_idle < sysctl_sched_migration_cost || 7128 !this_rq->rd->overload) { 7129 rcu_read_lock(); 7130 sd = rcu_dereference_check_sched_domain(this_rq->sd); 7131 if (sd) 7132 update_next_balance(sd, 0, &next_balance); 7133 rcu_read_unlock(); 7134 7135 goto out; 7136 } 7137 7138 /* 7139 * Drop the rq->lock, but keep IRQ/preempt disabled. 7140 */ 7141 raw_spin_unlock(&this_rq->lock); 7142 7143 update_blocked_averages(this_cpu); 7144 rcu_read_lock(); 7145 for_each_domain(this_cpu, sd) { 7146 int continue_balancing = 1; 7147 u64 t0, domain_cost; 7148 7149 if (!(sd->flags & SD_LOAD_BALANCE)) 7150 continue; 7151 7152 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { 7153 update_next_balance(sd, 0, &next_balance); 7154 break; 7155 } 7156 7157 if (sd->flags & SD_BALANCE_NEWIDLE) { 7158 t0 = sched_clock_cpu(this_cpu); 7159 7160 pulled_task = load_balance(this_cpu, this_rq, 7161 sd, CPU_NEWLY_IDLE, 7162 &continue_balancing); 7163 7164 domain_cost = sched_clock_cpu(this_cpu) - t0; 7165 if (domain_cost > sd->max_newidle_lb_cost) 7166 sd->max_newidle_lb_cost = domain_cost; 7167 7168 curr_cost += domain_cost; 7169 } 7170 7171 update_next_balance(sd, 0, &next_balance); 7172 7173 /* 7174 * Stop searching for tasks to pull if there are 7175 * now runnable tasks on this rq. 7176 */ 7177 if (pulled_task || this_rq->nr_running > 0) 7178 break; 7179 } 7180 rcu_read_unlock(); 7181 7182 raw_spin_lock(&this_rq->lock); 7183 7184 if (curr_cost > this_rq->max_idle_balance_cost) 7185 this_rq->max_idle_balance_cost = curr_cost; 7186 7187 /* 7188 * While browsing the domains, we released the rq lock, a task could 7189 * have been enqueued in the meantime. Since we're not going idle, 7190 * pretend we pulled a task. 7191 */ 7192 if (this_rq->cfs.h_nr_running && !pulled_task) 7193 pulled_task = 1; 7194 7195 out: 7196 /* Move the next balance forward */ 7197 if (time_after(this_rq->next_balance, next_balance)) 7198 this_rq->next_balance = next_balance; 7199 7200 /* Is there a task of a high priority class? */ 7201 if (this_rq->nr_running != this_rq->cfs.h_nr_running) 7202 pulled_task = -1; 7203 7204 if (pulled_task) { 7205 idle_exit_fair(this_rq); 7206 this_rq->idle_stamp = 0; 7207 } 7208 7209 return pulled_task; 7210 } 7211 7212 /* 7213 * active_load_balance_cpu_stop is run by cpu stopper. It pushes 7214 * running tasks off the busiest CPU onto idle CPUs. It requires at 7215 * least 1 task to be running on each physical CPU where possible, and 7216 * avoids physical / logical imbalances. 7217 */ 7218 static int active_load_balance_cpu_stop(void *data) 7219 { 7220 struct rq *busiest_rq = data; 7221 int busiest_cpu = cpu_of(busiest_rq); 7222 int target_cpu = busiest_rq->push_cpu; 7223 struct rq *target_rq = cpu_rq(target_cpu); 7224 struct sched_domain *sd; 7225 struct task_struct *p = NULL; 7226 7227 raw_spin_lock_irq(&busiest_rq->lock); 7228 7229 /* make sure the requested cpu hasn't gone down in the meantime */ 7230 if (unlikely(busiest_cpu != smp_processor_id() || 7231 !busiest_rq->active_balance)) 7232 goto out_unlock; 7233 7234 /* Is there any task to move? */ 7235 if (busiest_rq->nr_running <= 1) 7236 goto out_unlock; 7237 7238 /* 7239 * This condition is "impossible", if it occurs 7240 * we need to fix it. Originally reported by 7241 * Bjorn Helgaas on a 128-cpu setup. 7242 */ 7243 BUG_ON(busiest_rq == target_rq); 7244 7245 /* Search for an sd spanning us and the target CPU. */ 7246 rcu_read_lock(); 7247 for_each_domain(target_cpu, sd) { 7248 if ((sd->flags & SD_LOAD_BALANCE) && 7249 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) 7250 break; 7251 } 7252 7253 if (likely(sd)) { 7254 struct lb_env env = { 7255 .sd = sd, 7256 .dst_cpu = target_cpu, 7257 .dst_rq = target_rq, 7258 .src_cpu = busiest_rq->cpu, 7259 .src_rq = busiest_rq, 7260 .idle = CPU_IDLE, 7261 }; 7262 7263 schedstat_inc(sd, alb_count); 7264 7265 p = detach_one_task(&env); 7266 if (p) 7267 schedstat_inc(sd, alb_pushed); 7268 else 7269 schedstat_inc(sd, alb_failed); 7270 } 7271 rcu_read_unlock(); 7272 out_unlock: 7273 busiest_rq->active_balance = 0; 7274 raw_spin_unlock(&busiest_rq->lock); 7275 7276 if (p) 7277 attach_one_task(target_rq, p); 7278 7279 local_irq_enable(); 7280 7281 return 0; 7282 } 7283 7284 static inline int on_null_domain(struct rq *rq) 7285 { 7286 return unlikely(!rcu_dereference_sched(rq->sd)); 7287 } 7288 7289 #ifdef CONFIG_NO_HZ_COMMON 7290 /* 7291 * idle load balancing details 7292 * - When one of the busy CPUs notice that there may be an idle rebalancing 7293 * needed, they will kick the idle load balancer, which then does idle 7294 * load balancing for all the idle CPUs. 7295 */ 7296 static struct { 7297 cpumask_var_t idle_cpus_mask; 7298 atomic_t nr_cpus; 7299 unsigned long next_balance; /* in jiffy units */ 7300 } nohz ____cacheline_aligned; 7301 7302 static inline int find_new_ilb(void) 7303 { 7304 int ilb = cpumask_first(nohz.idle_cpus_mask); 7305 7306 if (ilb < nr_cpu_ids && idle_cpu(ilb)) 7307 return ilb; 7308 7309 return nr_cpu_ids; 7310 } 7311 7312 /* 7313 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the 7314 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle 7315 * CPU (if there is one). 7316 */ 7317 static void nohz_balancer_kick(void) 7318 { 7319 int ilb_cpu; 7320 7321 nohz.next_balance++; 7322 7323 ilb_cpu = find_new_ilb(); 7324 7325 if (ilb_cpu >= nr_cpu_ids) 7326 return; 7327 7328 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu))) 7329 return; 7330 /* 7331 * Use smp_send_reschedule() instead of resched_cpu(). 7332 * This way we generate a sched IPI on the target cpu which 7333 * is idle. And the softirq performing nohz idle load balance 7334 * will be run before returning from the IPI. 7335 */ 7336 smp_send_reschedule(ilb_cpu); 7337 return; 7338 } 7339 7340 static inline void nohz_balance_exit_idle(int cpu) 7341 { 7342 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { 7343 /* 7344 * Completely isolated CPUs don't ever set, so we must test. 7345 */ 7346 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { 7347 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); 7348 atomic_dec(&nohz.nr_cpus); 7349 } 7350 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 7351 } 7352 } 7353 7354 static inline void set_cpu_sd_state_busy(void) 7355 { 7356 struct sched_domain *sd; 7357 int cpu = smp_processor_id(); 7358 7359 rcu_read_lock(); 7360 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 7361 7362 if (!sd || !sd->nohz_idle) 7363 goto unlock; 7364 sd->nohz_idle = 0; 7365 7366 atomic_inc(&sd->groups->sgc->nr_busy_cpus); 7367 unlock: 7368 rcu_read_unlock(); 7369 } 7370 7371 void set_cpu_sd_state_idle(void) 7372 { 7373 struct sched_domain *sd; 7374 int cpu = smp_processor_id(); 7375 7376 rcu_read_lock(); 7377 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 7378 7379 if (!sd || sd->nohz_idle) 7380 goto unlock; 7381 sd->nohz_idle = 1; 7382 7383 atomic_dec(&sd->groups->sgc->nr_busy_cpus); 7384 unlock: 7385 rcu_read_unlock(); 7386 } 7387 7388 /* 7389 * This routine will record that the cpu is going idle with tick stopped. 7390 * This info will be used in performing idle load balancing in the future. 7391 */ 7392 void nohz_balance_enter_idle(int cpu) 7393 { 7394 /* 7395 * If this cpu is going down, then nothing needs to be done. 7396 */ 7397 if (!cpu_active(cpu)) 7398 return; 7399 7400 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) 7401 return; 7402 7403 /* 7404 * If we're a completely isolated CPU, we don't play. 7405 */ 7406 if (on_null_domain(cpu_rq(cpu))) 7407 return; 7408 7409 cpumask_set_cpu(cpu, nohz.idle_cpus_mask); 7410 atomic_inc(&nohz.nr_cpus); 7411 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 7412 } 7413 7414 static int sched_ilb_notifier(struct notifier_block *nfb, 7415 unsigned long action, void *hcpu) 7416 { 7417 switch (action & ~CPU_TASKS_FROZEN) { 7418 case CPU_DYING: 7419 nohz_balance_exit_idle(smp_processor_id()); 7420 return NOTIFY_OK; 7421 default: 7422 return NOTIFY_DONE; 7423 } 7424 } 7425 #endif 7426 7427 static DEFINE_SPINLOCK(balancing); 7428 7429 /* 7430 * Scale the max load_balance interval with the number of CPUs in the system. 7431 * This trades load-balance latency on larger machines for less cross talk. 7432 */ 7433 void update_max_interval(void) 7434 { 7435 max_load_balance_interval = HZ*num_online_cpus()/10; 7436 } 7437 7438 /* 7439 * It checks each scheduling domain to see if it is due to be balanced, 7440 * and initiates a balancing operation if so. 7441 * 7442 * Balancing parameters are set up in init_sched_domains. 7443 */ 7444 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) 7445 { 7446 int continue_balancing = 1; 7447 int cpu = rq->cpu; 7448 unsigned long interval; 7449 struct sched_domain *sd; 7450 /* Earliest time when we have to do rebalance again */ 7451 unsigned long next_balance = jiffies + 60*HZ; 7452 int update_next_balance = 0; 7453 int need_serialize, need_decay = 0; 7454 u64 max_cost = 0; 7455 7456 update_blocked_averages(cpu); 7457 7458 rcu_read_lock(); 7459 for_each_domain(cpu, sd) { 7460 /* 7461 * Decay the newidle max times here because this is a regular 7462 * visit to all the domains. Decay ~1% per second. 7463 */ 7464 if (time_after(jiffies, sd->next_decay_max_lb_cost)) { 7465 sd->max_newidle_lb_cost = 7466 (sd->max_newidle_lb_cost * 253) / 256; 7467 sd->next_decay_max_lb_cost = jiffies + HZ; 7468 need_decay = 1; 7469 } 7470 max_cost += sd->max_newidle_lb_cost; 7471 7472 if (!(sd->flags & SD_LOAD_BALANCE)) 7473 continue; 7474 7475 /* 7476 * Stop the load balance at this level. There is another 7477 * CPU in our sched group which is doing load balancing more 7478 * actively. 7479 */ 7480 if (!continue_balancing) { 7481 if (need_decay) 7482 continue; 7483 break; 7484 } 7485 7486 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 7487 7488 need_serialize = sd->flags & SD_SERIALIZE; 7489 if (need_serialize) { 7490 if (!spin_trylock(&balancing)) 7491 goto out; 7492 } 7493 7494 if (time_after_eq(jiffies, sd->last_balance + interval)) { 7495 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { 7496 /* 7497 * The LBF_DST_PINNED logic could have changed 7498 * env->dst_cpu, so we can't know our idle 7499 * state even if we migrated tasks. Update it. 7500 */ 7501 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; 7502 } 7503 sd->last_balance = jiffies; 7504 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 7505 } 7506 if (need_serialize) 7507 spin_unlock(&balancing); 7508 out: 7509 if (time_after(next_balance, sd->last_balance + interval)) { 7510 next_balance = sd->last_balance + interval; 7511 update_next_balance = 1; 7512 } 7513 } 7514 if (need_decay) { 7515 /* 7516 * Ensure the rq-wide value also decays but keep it at a 7517 * reasonable floor to avoid funnies with rq->avg_idle. 7518 */ 7519 rq->max_idle_balance_cost = 7520 max((u64)sysctl_sched_migration_cost, max_cost); 7521 } 7522 rcu_read_unlock(); 7523 7524 /* 7525 * next_balance will be updated only when there is a need. 7526 * When the cpu is attached to null domain for ex, it will not be 7527 * updated. 7528 */ 7529 if (likely(update_next_balance)) 7530 rq->next_balance = next_balance; 7531 } 7532 7533 #ifdef CONFIG_NO_HZ_COMMON 7534 /* 7535 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the 7536 * rebalancing for all the cpus for whom scheduler ticks are stopped. 7537 */ 7538 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) 7539 { 7540 int this_cpu = this_rq->cpu; 7541 struct rq *rq; 7542 int balance_cpu; 7543 7544 if (idle != CPU_IDLE || 7545 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) 7546 goto end; 7547 7548 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { 7549 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) 7550 continue; 7551 7552 /* 7553 * If this cpu gets work to do, stop the load balancing 7554 * work being done for other cpus. Next load 7555 * balancing owner will pick it up. 7556 */ 7557 if (need_resched()) 7558 break; 7559 7560 rq = cpu_rq(balance_cpu); 7561 7562 /* 7563 * If time for next balance is due, 7564 * do the balance. 7565 */ 7566 if (time_after_eq(jiffies, rq->next_balance)) { 7567 raw_spin_lock_irq(&rq->lock); 7568 update_rq_clock(rq); 7569 update_idle_cpu_load(rq); 7570 raw_spin_unlock_irq(&rq->lock); 7571 rebalance_domains(rq, CPU_IDLE); 7572 } 7573 7574 if (time_after(this_rq->next_balance, rq->next_balance)) 7575 this_rq->next_balance = rq->next_balance; 7576 } 7577 nohz.next_balance = this_rq->next_balance; 7578 end: 7579 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)); 7580 } 7581 7582 /* 7583 * Current heuristic for kicking the idle load balancer in the presence 7584 * of an idle cpu is the system. 7585 * - This rq has more than one task. 7586 * - At any scheduler domain level, this cpu's scheduler group has multiple 7587 * busy cpu's exceeding the group's capacity. 7588 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler 7589 * domain span are idle. 7590 */ 7591 static inline int nohz_kick_needed(struct rq *rq) 7592 { 7593 unsigned long now = jiffies; 7594 struct sched_domain *sd; 7595 struct sched_group_capacity *sgc; 7596 int nr_busy, cpu = rq->cpu; 7597 7598 if (unlikely(rq->idle_balance)) 7599 return 0; 7600 7601 /* 7602 * We may be recently in ticked or tickless idle mode. At the first 7603 * busy tick after returning from idle, we will update the busy stats. 7604 */ 7605 set_cpu_sd_state_busy(); 7606 nohz_balance_exit_idle(cpu); 7607 7608 /* 7609 * None are in tickless mode and hence no need for NOHZ idle load 7610 * balancing. 7611 */ 7612 if (likely(!atomic_read(&nohz.nr_cpus))) 7613 return 0; 7614 7615 if (time_before(now, nohz.next_balance)) 7616 return 0; 7617 7618 if (rq->nr_running >= 2) 7619 goto need_kick; 7620 7621 rcu_read_lock(); 7622 sd = rcu_dereference(per_cpu(sd_busy, cpu)); 7623 7624 if (sd) { 7625 sgc = sd->groups->sgc; 7626 nr_busy = atomic_read(&sgc->nr_busy_cpus); 7627 7628 if (nr_busy > 1) 7629 goto need_kick_unlock; 7630 } 7631 7632 sd = rcu_dereference(per_cpu(sd_asym, cpu)); 7633 7634 if (sd && (cpumask_first_and(nohz.idle_cpus_mask, 7635 sched_domain_span(sd)) < cpu)) 7636 goto need_kick_unlock; 7637 7638 rcu_read_unlock(); 7639 return 0; 7640 7641 need_kick_unlock: 7642 rcu_read_unlock(); 7643 need_kick: 7644 return 1; 7645 } 7646 #else 7647 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { } 7648 #endif 7649 7650 /* 7651 * run_rebalance_domains is triggered when needed from the scheduler tick. 7652 * Also triggered for nohz idle balancing (with nohz_balancing_kick set). 7653 */ 7654 static void run_rebalance_domains(struct softirq_action *h) 7655 { 7656 struct rq *this_rq = this_rq(); 7657 enum cpu_idle_type idle = this_rq->idle_balance ? 7658 CPU_IDLE : CPU_NOT_IDLE; 7659 7660 rebalance_domains(this_rq, idle); 7661 7662 /* 7663 * If this cpu has a pending nohz_balance_kick, then do the 7664 * balancing on behalf of the other idle cpus whose ticks are 7665 * stopped. 7666 */ 7667 nohz_idle_balance(this_rq, idle); 7668 } 7669 7670 /* 7671 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. 7672 */ 7673 void trigger_load_balance(struct rq *rq) 7674 { 7675 /* Don't need to rebalance while attached to NULL domain */ 7676 if (unlikely(on_null_domain(rq))) 7677 return; 7678 7679 if (time_after_eq(jiffies, rq->next_balance)) 7680 raise_softirq(SCHED_SOFTIRQ); 7681 #ifdef CONFIG_NO_HZ_COMMON 7682 if (nohz_kick_needed(rq)) 7683 nohz_balancer_kick(); 7684 #endif 7685 } 7686 7687 static void rq_online_fair(struct rq *rq) 7688 { 7689 update_sysctl(); 7690 7691 update_runtime_enabled(rq); 7692 } 7693 7694 static void rq_offline_fair(struct rq *rq) 7695 { 7696 update_sysctl(); 7697 7698 /* Ensure any throttled groups are reachable by pick_next_task */ 7699 unthrottle_offline_cfs_rqs(rq); 7700 } 7701 7702 #endif /* CONFIG_SMP */ 7703 7704 /* 7705 * scheduler tick hitting a task of our scheduling class: 7706 */ 7707 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) 7708 { 7709 struct cfs_rq *cfs_rq; 7710 struct sched_entity *se = &curr->se; 7711 7712 for_each_sched_entity(se) { 7713 cfs_rq = cfs_rq_of(se); 7714 entity_tick(cfs_rq, se, queued); 7715 } 7716 7717 if (numabalancing_enabled) 7718 task_tick_numa(rq, curr); 7719 7720 update_rq_runnable_avg(rq, 1); 7721 } 7722 7723 /* 7724 * called on fork with the child task as argument from the parent's context 7725 * - child not yet on the tasklist 7726 * - preemption disabled 7727 */ 7728 static void task_fork_fair(struct task_struct *p) 7729 { 7730 struct cfs_rq *cfs_rq; 7731 struct sched_entity *se = &p->se, *curr; 7732 int this_cpu = smp_processor_id(); 7733 struct rq *rq = this_rq(); 7734 unsigned long flags; 7735 7736 raw_spin_lock_irqsave(&rq->lock, flags); 7737 7738 update_rq_clock(rq); 7739 7740 cfs_rq = task_cfs_rq(current); 7741 curr = cfs_rq->curr; 7742 7743 /* 7744 * Not only the cpu but also the task_group of the parent might have 7745 * been changed after parent->se.parent,cfs_rq were copied to 7746 * child->se.parent,cfs_rq. So call __set_task_cpu() to make those 7747 * of child point to valid ones. 7748 */ 7749 rcu_read_lock(); 7750 __set_task_cpu(p, this_cpu); 7751 rcu_read_unlock(); 7752 7753 update_curr(cfs_rq); 7754 7755 if (curr) 7756 se->vruntime = curr->vruntime; 7757 place_entity(cfs_rq, se, 1); 7758 7759 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { 7760 /* 7761 * Upon rescheduling, sched_class::put_prev_task() will place 7762 * 'current' within the tree based on its new key value. 7763 */ 7764 swap(curr->vruntime, se->vruntime); 7765 resched_curr(rq); 7766 } 7767 7768 se->vruntime -= cfs_rq->min_vruntime; 7769 7770 raw_spin_unlock_irqrestore(&rq->lock, flags); 7771 } 7772 7773 /* 7774 * Priority of the task has changed. Check to see if we preempt 7775 * the current task. 7776 */ 7777 static void 7778 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) 7779 { 7780 if (!task_on_rq_queued(p)) 7781 return; 7782 7783 /* 7784 * Reschedule if we are currently running on this runqueue and 7785 * our priority decreased, or if we are not currently running on 7786 * this runqueue and our priority is higher than the current's 7787 */ 7788 if (rq->curr == p) { 7789 if (p->prio > oldprio) 7790 resched_curr(rq); 7791 } else 7792 check_preempt_curr(rq, p, 0); 7793 } 7794 7795 static void switched_from_fair(struct rq *rq, struct task_struct *p) 7796 { 7797 struct sched_entity *se = &p->se; 7798 struct cfs_rq *cfs_rq = cfs_rq_of(se); 7799 7800 /* 7801 * Ensure the task's vruntime is normalized, so that when it's 7802 * switched back to the fair class the enqueue_entity(.flags=0) will 7803 * do the right thing. 7804 * 7805 * If it's queued, then the dequeue_entity(.flags=0) will already 7806 * have normalized the vruntime, if it's !queued, then only when 7807 * the task is sleeping will it still have non-normalized vruntime. 7808 */ 7809 if (!task_on_rq_queued(p) && p->state != TASK_RUNNING) { 7810 /* 7811 * Fix up our vruntime so that the current sleep doesn't 7812 * cause 'unlimited' sleep bonus. 7813 */ 7814 place_entity(cfs_rq, se, 0); 7815 se->vruntime -= cfs_rq->min_vruntime; 7816 } 7817 7818 #ifdef CONFIG_SMP 7819 /* 7820 * Remove our load from contribution when we leave sched_fair 7821 * and ensure we don't carry in an old decay_count if we 7822 * switch back. 7823 */ 7824 if (se->avg.decay_count) { 7825 __synchronize_entity_decay(se); 7826 subtract_blocked_load_contrib(cfs_rq, se->avg.load_avg_contrib); 7827 } 7828 #endif 7829 } 7830 7831 /* 7832 * We switched to the sched_fair class. 7833 */ 7834 static void switched_to_fair(struct rq *rq, struct task_struct *p) 7835 { 7836 #ifdef CONFIG_FAIR_GROUP_SCHED 7837 struct sched_entity *se = &p->se; 7838 /* 7839 * Since the real-depth could have been changed (only FAIR 7840 * class maintain depth value), reset depth properly. 7841 */ 7842 se->depth = se->parent ? se->parent->depth + 1 : 0; 7843 #endif 7844 if (!task_on_rq_queued(p)) 7845 return; 7846 7847 /* 7848 * We were most likely switched from sched_rt, so 7849 * kick off the schedule if running, otherwise just see 7850 * if we can still preempt the current task. 7851 */ 7852 if (rq->curr == p) 7853 resched_curr(rq); 7854 else 7855 check_preempt_curr(rq, p, 0); 7856 } 7857 7858 /* Account for a task changing its policy or group. 7859 * 7860 * This routine is mostly called to set cfs_rq->curr field when a task 7861 * migrates between groups/classes. 7862 */ 7863 static void set_curr_task_fair(struct rq *rq) 7864 { 7865 struct sched_entity *se = &rq->curr->se; 7866 7867 for_each_sched_entity(se) { 7868 struct cfs_rq *cfs_rq = cfs_rq_of(se); 7869 7870 set_next_entity(cfs_rq, se); 7871 /* ensure bandwidth has been allocated on our new cfs_rq */ 7872 account_cfs_rq_runtime(cfs_rq, 0); 7873 } 7874 } 7875 7876 void init_cfs_rq(struct cfs_rq *cfs_rq) 7877 { 7878 cfs_rq->tasks_timeline = RB_ROOT; 7879 cfs_rq->min_vruntime = (u64)(-(1LL << 20)); 7880 #ifndef CONFIG_64BIT 7881 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 7882 #endif 7883 #ifdef CONFIG_SMP 7884 atomic64_set(&cfs_rq->decay_counter, 1); 7885 atomic_long_set(&cfs_rq->removed_load, 0); 7886 #endif 7887 } 7888 7889 #ifdef CONFIG_FAIR_GROUP_SCHED 7890 static void task_move_group_fair(struct task_struct *p, int queued) 7891 { 7892 struct sched_entity *se = &p->se; 7893 struct cfs_rq *cfs_rq; 7894 7895 /* 7896 * If the task was not on the rq at the time of this cgroup movement 7897 * it must have been asleep, sleeping tasks keep their ->vruntime 7898 * absolute on their old rq until wakeup (needed for the fair sleeper 7899 * bonus in place_entity()). 7900 * 7901 * If it was on the rq, we've just 'preempted' it, which does convert 7902 * ->vruntime to a relative base. 7903 * 7904 * Make sure both cases convert their relative position when migrating 7905 * to another cgroup's rq. This does somewhat interfere with the 7906 * fair sleeper stuff for the first placement, but who cares. 7907 */ 7908 /* 7909 * When !queued, vruntime of the task has usually NOT been normalized. 7910 * But there are some cases where it has already been normalized: 7911 * 7912 * - Moving a forked child which is waiting for being woken up by 7913 * wake_up_new_task(). 7914 * - Moving a task which has been woken up by try_to_wake_up() and 7915 * waiting for actually being woken up by sched_ttwu_pending(). 7916 * 7917 * To prevent boost or penalty in the new cfs_rq caused by delta 7918 * min_vruntime between the two cfs_rqs, we skip vruntime adjustment. 7919 */ 7920 if (!queued && (!se->sum_exec_runtime || p->state == TASK_WAKING)) 7921 queued = 1; 7922 7923 if (!queued) 7924 se->vruntime -= cfs_rq_of(se)->min_vruntime; 7925 set_task_rq(p, task_cpu(p)); 7926 se->depth = se->parent ? se->parent->depth + 1 : 0; 7927 if (!queued) { 7928 cfs_rq = cfs_rq_of(se); 7929 se->vruntime += cfs_rq->min_vruntime; 7930 #ifdef CONFIG_SMP 7931 /* 7932 * migrate_task_rq_fair() will have removed our previous 7933 * contribution, but we must synchronize for ongoing future 7934 * decay. 7935 */ 7936 se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter); 7937 cfs_rq->blocked_load_avg += se->avg.load_avg_contrib; 7938 #endif 7939 } 7940 } 7941 7942 void free_fair_sched_group(struct task_group *tg) 7943 { 7944 int i; 7945 7946 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); 7947 7948 for_each_possible_cpu(i) { 7949 if (tg->cfs_rq) 7950 kfree(tg->cfs_rq[i]); 7951 if (tg->se) 7952 kfree(tg->se[i]); 7953 } 7954 7955 kfree(tg->cfs_rq); 7956 kfree(tg->se); 7957 } 7958 7959 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 7960 { 7961 struct cfs_rq *cfs_rq; 7962 struct sched_entity *se; 7963 int i; 7964 7965 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL); 7966 if (!tg->cfs_rq) 7967 goto err; 7968 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL); 7969 if (!tg->se) 7970 goto err; 7971 7972 tg->shares = NICE_0_LOAD; 7973 7974 init_cfs_bandwidth(tg_cfs_bandwidth(tg)); 7975 7976 for_each_possible_cpu(i) { 7977 cfs_rq = kzalloc_node(sizeof(struct cfs_rq), 7978 GFP_KERNEL, cpu_to_node(i)); 7979 if (!cfs_rq) 7980 goto err; 7981 7982 se = kzalloc_node(sizeof(struct sched_entity), 7983 GFP_KERNEL, cpu_to_node(i)); 7984 if (!se) 7985 goto err_free_rq; 7986 7987 init_cfs_rq(cfs_rq); 7988 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); 7989 } 7990 7991 return 1; 7992 7993 err_free_rq: 7994 kfree(cfs_rq); 7995 err: 7996 return 0; 7997 } 7998 7999 void unregister_fair_sched_group(struct task_group *tg, int cpu) 8000 { 8001 struct rq *rq = cpu_rq(cpu); 8002 unsigned long flags; 8003 8004 /* 8005 * Only empty task groups can be destroyed; so we can speculatively 8006 * check on_list without danger of it being re-added. 8007 */ 8008 if (!tg->cfs_rq[cpu]->on_list) 8009 return; 8010 8011 raw_spin_lock_irqsave(&rq->lock, flags); 8012 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); 8013 raw_spin_unlock_irqrestore(&rq->lock, flags); 8014 } 8015 8016 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, 8017 struct sched_entity *se, int cpu, 8018 struct sched_entity *parent) 8019 { 8020 struct rq *rq = cpu_rq(cpu); 8021 8022 cfs_rq->tg = tg; 8023 cfs_rq->rq = rq; 8024 init_cfs_rq_runtime(cfs_rq); 8025 8026 tg->cfs_rq[cpu] = cfs_rq; 8027 tg->se[cpu] = se; 8028 8029 /* se could be NULL for root_task_group */ 8030 if (!se) 8031 return; 8032 8033 if (!parent) { 8034 se->cfs_rq = &rq->cfs; 8035 se->depth = 0; 8036 } else { 8037 se->cfs_rq = parent->my_q; 8038 se->depth = parent->depth + 1; 8039 } 8040 8041 se->my_q = cfs_rq; 8042 /* guarantee group entities always have weight */ 8043 update_load_set(&se->load, NICE_0_LOAD); 8044 se->parent = parent; 8045 } 8046 8047 static DEFINE_MUTEX(shares_mutex); 8048 8049 int sched_group_set_shares(struct task_group *tg, unsigned long shares) 8050 { 8051 int i; 8052 unsigned long flags; 8053 8054 /* 8055 * We can't change the weight of the root cgroup. 8056 */ 8057 if (!tg->se[0]) 8058 return -EINVAL; 8059 8060 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); 8061 8062 mutex_lock(&shares_mutex); 8063 if (tg->shares == shares) 8064 goto done; 8065 8066 tg->shares = shares; 8067 for_each_possible_cpu(i) { 8068 struct rq *rq = cpu_rq(i); 8069 struct sched_entity *se; 8070 8071 se = tg->se[i]; 8072 /* Propagate contribution to hierarchy */ 8073 raw_spin_lock_irqsave(&rq->lock, flags); 8074 8075 /* Possible calls to update_curr() need rq clock */ 8076 update_rq_clock(rq); 8077 for_each_sched_entity(se) 8078 update_cfs_shares(group_cfs_rq(se)); 8079 raw_spin_unlock_irqrestore(&rq->lock, flags); 8080 } 8081 8082 done: 8083 mutex_unlock(&shares_mutex); 8084 return 0; 8085 } 8086 #else /* CONFIG_FAIR_GROUP_SCHED */ 8087 8088 void free_fair_sched_group(struct task_group *tg) { } 8089 8090 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 8091 { 8092 return 1; 8093 } 8094 8095 void unregister_fair_sched_group(struct task_group *tg, int cpu) { } 8096 8097 #endif /* CONFIG_FAIR_GROUP_SCHED */ 8098 8099 8100 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) 8101 { 8102 struct sched_entity *se = &task->se; 8103 unsigned int rr_interval = 0; 8104 8105 /* 8106 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise 8107 * idle runqueue: 8108 */ 8109 if (rq->cfs.load.weight) 8110 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); 8111 8112 return rr_interval; 8113 } 8114 8115 /* 8116 * All the scheduling class methods: 8117 */ 8118 const struct sched_class fair_sched_class = { 8119 .next = &idle_sched_class, 8120 .enqueue_task = enqueue_task_fair, 8121 .dequeue_task = dequeue_task_fair, 8122 .yield_task = yield_task_fair, 8123 .yield_to_task = yield_to_task_fair, 8124 8125 .check_preempt_curr = check_preempt_wakeup, 8126 8127 .pick_next_task = pick_next_task_fair, 8128 .put_prev_task = put_prev_task_fair, 8129 8130 #ifdef CONFIG_SMP 8131 .select_task_rq = select_task_rq_fair, 8132 .migrate_task_rq = migrate_task_rq_fair, 8133 8134 .rq_online = rq_online_fair, 8135 .rq_offline = rq_offline_fair, 8136 8137 .task_waking = task_waking_fair, 8138 #endif 8139 8140 .set_curr_task = set_curr_task_fair, 8141 .task_tick = task_tick_fair, 8142 .task_fork = task_fork_fair, 8143 8144 .prio_changed = prio_changed_fair, 8145 .switched_from = switched_from_fair, 8146 .switched_to = switched_to_fair, 8147 8148 .get_rr_interval = get_rr_interval_fair, 8149 8150 .update_curr = update_curr_fair, 8151 8152 #ifdef CONFIG_FAIR_GROUP_SCHED 8153 .task_move_group = task_move_group_fair, 8154 #endif 8155 }; 8156 8157 #ifdef CONFIG_SCHED_DEBUG 8158 void print_cfs_stats(struct seq_file *m, int cpu) 8159 { 8160 struct cfs_rq *cfs_rq; 8161 8162 rcu_read_lock(); 8163 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) 8164 print_cfs_rq(m, cpu, cfs_rq); 8165 rcu_read_unlock(); 8166 } 8167 #endif 8168 8169 __init void init_sched_fair_class(void) 8170 { 8171 #ifdef CONFIG_SMP 8172 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); 8173 8174 #ifdef CONFIG_NO_HZ_COMMON 8175 nohz.next_balance = jiffies; 8176 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); 8177 cpu_notifier(sched_ilb_notifier, 0); 8178 #endif 8179 #endif /* SMP */ 8180 8181 } 8182