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 21 */ 22 23 #include <linux/sched.h> 24 #include <linux/latencytop.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 * 41 * NOTE: this latency value is not the same as the concept of 42 * 'timeslice length' - timeslices in CFS are of variable length 43 * and have no persistent notion like in traditional, time-slice 44 * based scheduling concepts. 45 * 46 * (to see the precise effective timeslice length of your workload, 47 * run vmstat and monitor the context-switches (cs) field) 48 * 49 * (default: 6ms * (1 + ilog(ncpus)), units: nanoseconds) 50 */ 51 unsigned int sysctl_sched_latency = 6000000ULL; 52 unsigned int normalized_sysctl_sched_latency = 6000000ULL; 53 54 /* 55 * The initial- and re-scaling of tunables is configurable 56 * 57 * Options are: 58 * 59 * SCHED_TUNABLESCALING_NONE - unscaled, always *1 60 * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus) 61 * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus 62 * 63 * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus)) 64 */ 65 enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG; 66 67 /* 68 * Minimal preemption granularity for CPU-bound tasks: 69 * 70 * (default: 0.75 msec * (1 + ilog(ncpus)), units: nanoseconds) 71 */ 72 unsigned int sysctl_sched_min_granularity = 750000ULL; 73 unsigned int normalized_sysctl_sched_min_granularity = 750000ULL; 74 75 /* 76 * This value is kept at sysctl_sched_latency/sysctl_sched_min_granularity 77 */ 78 static unsigned int sched_nr_latency = 8; 79 80 /* 81 * After fork, child runs first. If set to 0 (default) then 82 * parent will (try to) run first. 83 */ 84 unsigned int sysctl_sched_child_runs_first __read_mostly; 85 86 /* 87 * SCHED_OTHER wake-up granularity. 88 * 89 * This option delays the preemption effects of decoupled workloads 90 * and reduces their over-scheduling. Synchronous workloads will still 91 * have immediate wakeup/sleep latencies. 92 * 93 * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds) 94 */ 95 unsigned int sysctl_sched_wakeup_granularity = 1000000UL; 96 unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; 97 98 const_debug unsigned int sysctl_sched_migration_cost = 500000UL; 99 100 #ifdef CONFIG_SMP 101 /* 102 * For asym packing, by default the lower numbered cpu has higher priority. 103 */ 104 int __weak arch_asym_cpu_priority(int cpu) 105 { 106 return -cpu; 107 } 108 #endif 109 110 #ifdef CONFIG_CFS_BANDWIDTH 111 /* 112 * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool 113 * each time a cfs_rq requests quota. 114 * 115 * Note: in the case that the slice exceeds the runtime remaining (either due 116 * to consumption or the quota being specified to be smaller than the slice) 117 * we will always only issue the remaining available time. 118 * 119 * (default: 5 msec, units: microseconds) 120 */ 121 unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; 122 #endif 123 124 /* 125 * The margin used when comparing utilization with CPU capacity: 126 * util * margin < capacity * 1024 127 * 128 * (default: ~20%) 129 */ 130 unsigned int capacity_margin = 1280; 131 132 static inline void update_load_add(struct load_weight *lw, unsigned long inc) 133 { 134 lw->weight += inc; 135 lw->inv_weight = 0; 136 } 137 138 static inline void update_load_sub(struct load_weight *lw, unsigned long dec) 139 { 140 lw->weight -= dec; 141 lw->inv_weight = 0; 142 } 143 144 static inline void update_load_set(struct load_weight *lw, unsigned long w) 145 { 146 lw->weight = w; 147 lw->inv_weight = 0; 148 } 149 150 /* 151 * Increase the granularity value when there are more CPUs, 152 * because with more CPUs the 'effective latency' as visible 153 * to users decreases. But the relationship is not linear, 154 * so pick a second-best guess by going with the log2 of the 155 * number of CPUs. 156 * 157 * This idea comes from the SD scheduler of Con Kolivas: 158 */ 159 static unsigned int get_update_sysctl_factor(void) 160 { 161 unsigned int cpus = min_t(unsigned int, num_online_cpus(), 8); 162 unsigned int factor; 163 164 switch (sysctl_sched_tunable_scaling) { 165 case SCHED_TUNABLESCALING_NONE: 166 factor = 1; 167 break; 168 case SCHED_TUNABLESCALING_LINEAR: 169 factor = cpus; 170 break; 171 case SCHED_TUNABLESCALING_LOG: 172 default: 173 factor = 1 + ilog2(cpus); 174 break; 175 } 176 177 return factor; 178 } 179 180 static void update_sysctl(void) 181 { 182 unsigned int factor = get_update_sysctl_factor(); 183 184 #define SET_SYSCTL(name) \ 185 (sysctl_##name = (factor) * normalized_sysctl_##name) 186 SET_SYSCTL(sched_min_granularity); 187 SET_SYSCTL(sched_latency); 188 SET_SYSCTL(sched_wakeup_granularity); 189 #undef SET_SYSCTL 190 } 191 192 void sched_init_granularity(void) 193 { 194 update_sysctl(); 195 } 196 197 #define WMULT_CONST (~0U) 198 #define WMULT_SHIFT 32 199 200 static void __update_inv_weight(struct load_weight *lw) 201 { 202 unsigned long w; 203 204 if (likely(lw->inv_weight)) 205 return; 206 207 w = scale_load_down(lw->weight); 208 209 if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST)) 210 lw->inv_weight = 1; 211 else if (unlikely(!w)) 212 lw->inv_weight = WMULT_CONST; 213 else 214 lw->inv_weight = WMULT_CONST / w; 215 } 216 217 /* 218 * delta_exec * weight / lw.weight 219 * OR 220 * (delta_exec * (weight * lw->inv_weight)) >> WMULT_SHIFT 221 * 222 * Either weight := NICE_0_LOAD and lw \e sched_prio_to_wmult[], in which case 223 * we're guaranteed shift stays positive because inv_weight is guaranteed to 224 * fit 32 bits, and NICE_0_LOAD gives another 10 bits; therefore shift >= 22. 225 * 226 * Or, weight =< lw.weight (because lw.weight is the runqueue weight), thus 227 * weight/lw.weight <= 1, and therefore our shift will also be positive. 228 */ 229 static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw) 230 { 231 u64 fact = scale_load_down(weight); 232 int shift = WMULT_SHIFT; 233 234 __update_inv_weight(lw); 235 236 if (unlikely(fact >> 32)) { 237 while (fact >> 32) { 238 fact >>= 1; 239 shift--; 240 } 241 } 242 243 /* hint to use a 32x32->64 mul */ 244 fact = (u64)(u32)fact * lw->inv_weight; 245 246 while (fact >> 32) { 247 fact >>= 1; 248 shift--; 249 } 250 251 return mul_u64_u32_shr(delta_exec, fact, shift); 252 } 253 254 255 const struct sched_class fair_sched_class; 256 257 /************************************************************** 258 * CFS operations on generic schedulable entities: 259 */ 260 261 #ifdef CONFIG_FAIR_GROUP_SCHED 262 263 /* cpu runqueue to which this cfs_rq is attached */ 264 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 265 { 266 return cfs_rq->rq; 267 } 268 269 /* An entity is a task if it doesn't "own" a runqueue */ 270 #define entity_is_task(se) (!se->my_q) 271 272 static inline struct task_struct *task_of(struct sched_entity *se) 273 { 274 SCHED_WARN_ON(!entity_is_task(se)); 275 return container_of(se, struct task_struct, se); 276 } 277 278 /* Walk up scheduling entities hierarchy */ 279 #define for_each_sched_entity(se) \ 280 for (; se; se = se->parent) 281 282 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 283 { 284 return p->se.cfs_rq; 285 } 286 287 /* runqueue on which this entity is (to be) queued */ 288 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 289 { 290 return se->cfs_rq; 291 } 292 293 /* runqueue "owned" by this group */ 294 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 295 { 296 return grp->my_q; 297 } 298 299 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 300 { 301 if (!cfs_rq->on_list) { 302 struct rq *rq = rq_of(cfs_rq); 303 int cpu = cpu_of(rq); 304 /* 305 * Ensure we either appear before our parent (if already 306 * enqueued) or force our parent to appear after us when it is 307 * enqueued. The fact that we always enqueue bottom-up 308 * reduces this to two cases and a special case for the root 309 * cfs_rq. Furthermore, it also means that we will always reset 310 * tmp_alone_branch either when the branch is connected 311 * to a tree or when we reach the beg of the tree 312 */ 313 if (cfs_rq->tg->parent && 314 cfs_rq->tg->parent->cfs_rq[cpu]->on_list) { 315 /* 316 * If parent is already on the list, we add the child 317 * just before. Thanks to circular linked property of 318 * the list, this means to put the child at the tail 319 * of the list that starts by parent. 320 */ 321 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, 322 &(cfs_rq->tg->parent->cfs_rq[cpu]->leaf_cfs_rq_list)); 323 /* 324 * The branch is now connected to its tree so we can 325 * reset tmp_alone_branch to the beginning of the 326 * list. 327 */ 328 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; 329 } else if (!cfs_rq->tg->parent) { 330 /* 331 * cfs rq without parent should be put 332 * at the tail of the list. 333 */ 334 list_add_tail_rcu(&cfs_rq->leaf_cfs_rq_list, 335 &rq->leaf_cfs_rq_list); 336 /* 337 * We have reach the beg of a tree so we can reset 338 * tmp_alone_branch to the beginning of the list. 339 */ 340 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; 341 } else { 342 /* 343 * The parent has not already been added so we want to 344 * make sure that it will be put after us. 345 * tmp_alone_branch points to the beg of the branch 346 * where we will add parent. 347 */ 348 list_add_rcu(&cfs_rq->leaf_cfs_rq_list, 349 rq->tmp_alone_branch); 350 /* 351 * update tmp_alone_branch to points to the new beg 352 * of the branch 353 */ 354 rq->tmp_alone_branch = &cfs_rq->leaf_cfs_rq_list; 355 } 356 357 cfs_rq->on_list = 1; 358 } 359 } 360 361 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 362 { 363 if (cfs_rq->on_list) { 364 list_del_rcu(&cfs_rq->leaf_cfs_rq_list); 365 cfs_rq->on_list = 0; 366 } 367 } 368 369 /* Iterate thr' all leaf cfs_rq's on a runqueue */ 370 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 371 list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list) 372 373 /* Do the two (enqueued) entities belong to the same group ? */ 374 static inline struct cfs_rq * 375 is_same_group(struct sched_entity *se, struct sched_entity *pse) 376 { 377 if (se->cfs_rq == pse->cfs_rq) 378 return se->cfs_rq; 379 380 return NULL; 381 } 382 383 static inline struct sched_entity *parent_entity(struct sched_entity *se) 384 { 385 return se->parent; 386 } 387 388 static void 389 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 390 { 391 int se_depth, pse_depth; 392 393 /* 394 * preemption test can be made between sibling entities who are in the 395 * same cfs_rq i.e who have a common parent. Walk up the hierarchy of 396 * both tasks until we find their ancestors who are siblings of common 397 * parent. 398 */ 399 400 /* First walk up until both entities are at same depth */ 401 se_depth = (*se)->depth; 402 pse_depth = (*pse)->depth; 403 404 while (se_depth > pse_depth) { 405 se_depth--; 406 *se = parent_entity(*se); 407 } 408 409 while (pse_depth > se_depth) { 410 pse_depth--; 411 *pse = parent_entity(*pse); 412 } 413 414 while (!is_same_group(*se, *pse)) { 415 *se = parent_entity(*se); 416 *pse = parent_entity(*pse); 417 } 418 } 419 420 #else /* !CONFIG_FAIR_GROUP_SCHED */ 421 422 static inline struct task_struct *task_of(struct sched_entity *se) 423 { 424 return container_of(se, struct task_struct, se); 425 } 426 427 static inline struct rq *rq_of(struct cfs_rq *cfs_rq) 428 { 429 return container_of(cfs_rq, struct rq, cfs); 430 } 431 432 #define entity_is_task(se) 1 433 434 #define for_each_sched_entity(se) \ 435 for (; se; se = NULL) 436 437 static inline struct cfs_rq *task_cfs_rq(struct task_struct *p) 438 { 439 return &task_rq(p)->cfs; 440 } 441 442 static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se) 443 { 444 struct task_struct *p = task_of(se); 445 struct rq *rq = task_rq(p); 446 447 return &rq->cfs; 448 } 449 450 /* runqueue "owned" by this group */ 451 static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp) 452 { 453 return NULL; 454 } 455 456 static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq) 457 { 458 } 459 460 static inline void list_del_leaf_cfs_rq(struct cfs_rq *cfs_rq) 461 { 462 } 463 464 #define for_each_leaf_cfs_rq(rq, cfs_rq) \ 465 for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL) 466 467 static inline struct sched_entity *parent_entity(struct sched_entity *se) 468 { 469 return NULL; 470 } 471 472 static inline void 473 find_matching_se(struct sched_entity **se, struct sched_entity **pse) 474 { 475 } 476 477 #endif /* CONFIG_FAIR_GROUP_SCHED */ 478 479 static __always_inline 480 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec); 481 482 /************************************************************** 483 * Scheduling class tree data structure manipulation methods: 484 */ 485 486 static inline u64 max_vruntime(u64 max_vruntime, u64 vruntime) 487 { 488 s64 delta = (s64)(vruntime - max_vruntime); 489 if (delta > 0) 490 max_vruntime = vruntime; 491 492 return max_vruntime; 493 } 494 495 static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime) 496 { 497 s64 delta = (s64)(vruntime - min_vruntime); 498 if (delta < 0) 499 min_vruntime = vruntime; 500 501 return min_vruntime; 502 } 503 504 static inline int entity_before(struct sched_entity *a, 505 struct sched_entity *b) 506 { 507 return (s64)(a->vruntime - b->vruntime) < 0; 508 } 509 510 static void update_min_vruntime(struct cfs_rq *cfs_rq) 511 { 512 struct sched_entity *curr = cfs_rq->curr; 513 514 u64 vruntime = cfs_rq->min_vruntime; 515 516 if (curr) { 517 if (curr->on_rq) 518 vruntime = curr->vruntime; 519 else 520 curr = NULL; 521 } 522 523 if (cfs_rq->rb_leftmost) { 524 struct sched_entity *se = rb_entry(cfs_rq->rb_leftmost, 525 struct sched_entity, 526 run_node); 527 528 if (!curr) 529 vruntime = se->vruntime; 530 else 531 vruntime = min_vruntime(vruntime, se->vruntime); 532 } 533 534 /* ensure we never gain time by being placed backwards. */ 535 cfs_rq->min_vruntime = max_vruntime(cfs_rq->min_vruntime, vruntime); 536 #ifndef CONFIG_64BIT 537 smp_wmb(); 538 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 539 #endif 540 } 541 542 /* 543 * Enqueue an entity into the rb-tree: 544 */ 545 static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 546 { 547 struct rb_node **link = &cfs_rq->tasks_timeline.rb_node; 548 struct rb_node *parent = NULL; 549 struct sched_entity *entry; 550 int leftmost = 1; 551 552 /* 553 * Find the right place in the rbtree: 554 */ 555 while (*link) { 556 parent = *link; 557 entry = rb_entry(parent, struct sched_entity, run_node); 558 /* 559 * We dont care about collisions. Nodes with 560 * the same key stay together. 561 */ 562 if (entity_before(se, entry)) { 563 link = &parent->rb_left; 564 } else { 565 link = &parent->rb_right; 566 leftmost = 0; 567 } 568 } 569 570 /* 571 * Maintain a cache of leftmost tree entries (it is frequently 572 * used): 573 */ 574 if (leftmost) 575 cfs_rq->rb_leftmost = &se->run_node; 576 577 rb_link_node(&se->run_node, parent, link); 578 rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline); 579 } 580 581 static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 582 { 583 if (cfs_rq->rb_leftmost == &se->run_node) { 584 struct rb_node *next_node; 585 586 next_node = rb_next(&se->run_node); 587 cfs_rq->rb_leftmost = next_node; 588 } 589 590 rb_erase(&se->run_node, &cfs_rq->tasks_timeline); 591 } 592 593 struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) 594 { 595 struct rb_node *left = cfs_rq->rb_leftmost; 596 597 if (!left) 598 return NULL; 599 600 return rb_entry(left, struct sched_entity, run_node); 601 } 602 603 static struct sched_entity *__pick_next_entity(struct sched_entity *se) 604 { 605 struct rb_node *next = rb_next(&se->run_node); 606 607 if (!next) 608 return NULL; 609 610 return rb_entry(next, struct sched_entity, run_node); 611 } 612 613 #ifdef CONFIG_SCHED_DEBUG 614 struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq) 615 { 616 struct rb_node *last = rb_last(&cfs_rq->tasks_timeline); 617 618 if (!last) 619 return NULL; 620 621 return rb_entry(last, struct sched_entity, run_node); 622 } 623 624 /************************************************************** 625 * Scheduling class statistics methods: 626 */ 627 628 int sched_proc_update_handler(struct ctl_table *table, int write, 629 void __user *buffer, size_t *lenp, 630 loff_t *ppos) 631 { 632 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); 633 unsigned int factor = get_update_sysctl_factor(); 634 635 if (ret || !write) 636 return ret; 637 638 sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency, 639 sysctl_sched_min_granularity); 640 641 #define WRT_SYSCTL(name) \ 642 (normalized_sysctl_##name = sysctl_##name / (factor)) 643 WRT_SYSCTL(sched_min_granularity); 644 WRT_SYSCTL(sched_latency); 645 WRT_SYSCTL(sched_wakeup_granularity); 646 #undef WRT_SYSCTL 647 648 return 0; 649 } 650 #endif 651 652 /* 653 * delta /= w 654 */ 655 static inline u64 calc_delta_fair(u64 delta, struct sched_entity *se) 656 { 657 if (unlikely(se->load.weight != NICE_0_LOAD)) 658 delta = __calc_delta(delta, NICE_0_LOAD, &se->load); 659 660 return delta; 661 } 662 663 /* 664 * The idea is to set a period in which each task runs once. 665 * 666 * When there are too many tasks (sched_nr_latency) we have to stretch 667 * this period because otherwise the slices get too small. 668 * 669 * p = (nr <= nl) ? l : l*nr/nl 670 */ 671 static u64 __sched_period(unsigned long nr_running) 672 { 673 if (unlikely(nr_running > sched_nr_latency)) 674 return nr_running * sysctl_sched_min_granularity; 675 else 676 return sysctl_sched_latency; 677 } 678 679 /* 680 * We calculate the wall-time slice from the period by taking a part 681 * proportional to the weight. 682 * 683 * s = p*P[w/rw] 684 */ 685 static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 686 { 687 u64 slice = __sched_period(cfs_rq->nr_running + !se->on_rq); 688 689 for_each_sched_entity(se) { 690 struct load_weight *load; 691 struct load_weight lw; 692 693 cfs_rq = cfs_rq_of(se); 694 load = &cfs_rq->load; 695 696 if (unlikely(!se->on_rq)) { 697 lw = cfs_rq->load; 698 699 update_load_add(&lw, se->load.weight); 700 load = &lw; 701 } 702 slice = __calc_delta(slice, se->load.weight, load); 703 } 704 return slice; 705 } 706 707 /* 708 * We calculate the vruntime slice of a to-be-inserted task. 709 * 710 * vs = s/w 711 */ 712 static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se) 713 { 714 return calc_delta_fair(sched_slice(cfs_rq, se), se); 715 } 716 717 #ifdef CONFIG_SMP 718 static int select_idle_sibling(struct task_struct *p, int prev_cpu, int cpu); 719 static unsigned long task_h_load(struct task_struct *p); 720 721 /* 722 * We choose a half-life close to 1 scheduling period. 723 * Note: The tables runnable_avg_yN_inv and runnable_avg_yN_sum are 724 * dependent on this value. 725 */ 726 #define LOAD_AVG_PERIOD 32 727 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */ 728 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */ 729 730 /* Give new sched_entity start runnable values to heavy its load in infant time */ 731 void init_entity_runnable_average(struct sched_entity *se) 732 { 733 struct sched_avg *sa = &se->avg; 734 735 sa->last_update_time = 0; 736 /* 737 * sched_avg's period_contrib should be strictly less then 1024, so 738 * we give it 1023 to make sure it is almost a period (1024us), and 739 * will definitely be update (after enqueue). 740 */ 741 sa->period_contrib = 1023; 742 /* 743 * Tasks are intialized with full load to be seen as heavy tasks until 744 * they get a chance to stabilize to their real load level. 745 * Group entities are intialized with zero load to reflect the fact that 746 * nothing has been attached to the task group yet. 747 */ 748 if (entity_is_task(se)) 749 sa->load_avg = scale_load_down(se->load.weight); 750 sa->load_sum = sa->load_avg * LOAD_AVG_MAX; 751 /* 752 * At this point, util_avg won't be used in select_task_rq_fair anyway 753 */ 754 sa->util_avg = 0; 755 sa->util_sum = 0; 756 /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ 757 } 758 759 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); 760 static void attach_entity_cfs_rq(struct sched_entity *se); 761 762 /* 763 * With new tasks being created, their initial util_avgs are extrapolated 764 * based on the cfs_rq's current util_avg: 765 * 766 * util_avg = cfs_rq->util_avg / (cfs_rq->load_avg + 1) * se.load.weight 767 * 768 * However, in many cases, the above util_avg does not give a desired 769 * value. Moreover, the sum of the util_avgs may be divergent, such 770 * as when the series is a harmonic series. 771 * 772 * To solve this problem, we also cap the util_avg of successive tasks to 773 * only 1/2 of the left utilization budget: 774 * 775 * util_avg_cap = (1024 - cfs_rq->avg.util_avg) / 2^n 776 * 777 * where n denotes the nth task. 778 * 779 * For example, a simplest series from the beginning would be like: 780 * 781 * task util_avg: 512, 256, 128, 64, 32, 16, 8, ... 782 * cfs_rq util_avg: 512, 768, 896, 960, 992, 1008, 1016, ... 783 * 784 * Finally, that extrapolated util_avg is clamped to the cap (util_avg_cap) 785 * if util_avg > util_avg_cap. 786 */ 787 void post_init_entity_util_avg(struct sched_entity *se) 788 { 789 struct cfs_rq *cfs_rq = cfs_rq_of(se); 790 struct sched_avg *sa = &se->avg; 791 long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2; 792 793 if (cap > 0) { 794 if (cfs_rq->avg.util_avg != 0) { 795 sa->util_avg = cfs_rq->avg.util_avg * se->load.weight; 796 sa->util_avg /= (cfs_rq->avg.load_avg + 1); 797 798 if (sa->util_avg > cap) 799 sa->util_avg = cap; 800 } else { 801 sa->util_avg = cap; 802 } 803 sa->util_sum = sa->util_avg * LOAD_AVG_MAX; 804 } 805 806 if (entity_is_task(se)) { 807 struct task_struct *p = task_of(se); 808 if (p->sched_class != &fair_sched_class) { 809 /* 810 * For !fair tasks do: 811 * 812 update_cfs_rq_load_avg(now, cfs_rq, false); 813 attach_entity_load_avg(cfs_rq, se); 814 switched_from_fair(rq, p); 815 * 816 * such that the next switched_to_fair() has the 817 * expected state. 818 */ 819 se->avg.last_update_time = cfs_rq_clock_task(cfs_rq); 820 return; 821 } 822 } 823 824 attach_entity_cfs_rq(se); 825 } 826 827 #else /* !CONFIG_SMP */ 828 void init_entity_runnable_average(struct sched_entity *se) 829 { 830 } 831 void post_init_entity_util_avg(struct sched_entity *se) 832 { 833 } 834 static void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) 835 { 836 } 837 #endif /* CONFIG_SMP */ 838 839 /* 840 * Update the current task's runtime statistics. 841 */ 842 static void update_curr(struct cfs_rq *cfs_rq) 843 { 844 struct sched_entity *curr = cfs_rq->curr; 845 u64 now = rq_clock_task(rq_of(cfs_rq)); 846 u64 delta_exec; 847 848 if (unlikely(!curr)) 849 return; 850 851 delta_exec = now - curr->exec_start; 852 if (unlikely((s64)delta_exec <= 0)) 853 return; 854 855 curr->exec_start = now; 856 857 schedstat_set(curr->statistics.exec_max, 858 max(delta_exec, curr->statistics.exec_max)); 859 860 curr->sum_exec_runtime += delta_exec; 861 schedstat_add(cfs_rq->exec_clock, delta_exec); 862 863 curr->vruntime += calc_delta_fair(delta_exec, curr); 864 update_min_vruntime(cfs_rq); 865 866 if (entity_is_task(curr)) { 867 struct task_struct *curtask = task_of(curr); 868 869 trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); 870 cpuacct_charge(curtask, delta_exec); 871 account_group_exec_runtime(curtask, delta_exec); 872 } 873 874 account_cfs_rq_runtime(cfs_rq, delta_exec); 875 } 876 877 static void update_curr_fair(struct rq *rq) 878 { 879 update_curr(cfs_rq_of(&rq->curr->se)); 880 } 881 882 static inline void 883 update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 884 { 885 u64 wait_start, prev_wait_start; 886 887 if (!schedstat_enabled()) 888 return; 889 890 wait_start = rq_clock(rq_of(cfs_rq)); 891 prev_wait_start = schedstat_val(se->statistics.wait_start); 892 893 if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) && 894 likely(wait_start > prev_wait_start)) 895 wait_start -= prev_wait_start; 896 897 schedstat_set(se->statistics.wait_start, wait_start); 898 } 899 900 static inline void 901 update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se) 902 { 903 struct task_struct *p; 904 u64 delta; 905 906 if (!schedstat_enabled()) 907 return; 908 909 delta = rq_clock(rq_of(cfs_rq)) - schedstat_val(se->statistics.wait_start); 910 911 if (entity_is_task(se)) { 912 p = task_of(se); 913 if (task_on_rq_migrating(p)) { 914 /* 915 * Preserve migrating task's wait time so wait_start 916 * time stamp can be adjusted to accumulate wait time 917 * prior to migration. 918 */ 919 schedstat_set(se->statistics.wait_start, delta); 920 return; 921 } 922 trace_sched_stat_wait(p, delta); 923 } 924 925 schedstat_set(se->statistics.wait_max, 926 max(schedstat_val(se->statistics.wait_max), delta)); 927 schedstat_inc(se->statistics.wait_count); 928 schedstat_add(se->statistics.wait_sum, delta); 929 schedstat_set(se->statistics.wait_start, 0); 930 } 931 932 static inline void 933 update_stats_enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se) 934 { 935 struct task_struct *tsk = NULL; 936 u64 sleep_start, block_start; 937 938 if (!schedstat_enabled()) 939 return; 940 941 sleep_start = schedstat_val(se->statistics.sleep_start); 942 block_start = schedstat_val(se->statistics.block_start); 943 944 if (entity_is_task(se)) 945 tsk = task_of(se); 946 947 if (sleep_start) { 948 u64 delta = rq_clock(rq_of(cfs_rq)) - sleep_start; 949 950 if ((s64)delta < 0) 951 delta = 0; 952 953 if (unlikely(delta > schedstat_val(se->statistics.sleep_max))) 954 schedstat_set(se->statistics.sleep_max, delta); 955 956 schedstat_set(se->statistics.sleep_start, 0); 957 schedstat_add(se->statistics.sum_sleep_runtime, delta); 958 959 if (tsk) { 960 account_scheduler_latency(tsk, delta >> 10, 1); 961 trace_sched_stat_sleep(tsk, delta); 962 } 963 } 964 if (block_start) { 965 u64 delta = rq_clock(rq_of(cfs_rq)) - block_start; 966 967 if ((s64)delta < 0) 968 delta = 0; 969 970 if (unlikely(delta > schedstat_val(se->statistics.block_max))) 971 schedstat_set(se->statistics.block_max, delta); 972 973 schedstat_set(se->statistics.block_start, 0); 974 schedstat_add(se->statistics.sum_sleep_runtime, delta); 975 976 if (tsk) { 977 if (tsk->in_iowait) { 978 schedstat_add(se->statistics.iowait_sum, delta); 979 schedstat_inc(se->statistics.iowait_count); 980 trace_sched_stat_iowait(tsk, delta); 981 } 982 983 trace_sched_stat_blocked(tsk, delta); 984 985 /* 986 * Blocking time is in units of nanosecs, so shift by 987 * 20 to get a milliseconds-range estimation of the 988 * amount of time that the task spent sleeping: 989 */ 990 if (unlikely(prof_on == SLEEP_PROFILING)) { 991 profile_hits(SLEEP_PROFILING, 992 (void *)get_wchan(tsk), 993 delta >> 20); 994 } 995 account_scheduler_latency(tsk, delta >> 10, 0); 996 } 997 } 998 } 999 1000 /* 1001 * Task is being enqueued - update stats: 1002 */ 1003 static inline void 1004 update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 1005 { 1006 if (!schedstat_enabled()) 1007 return; 1008 1009 /* 1010 * Are we enqueueing a waiting task? (for current tasks 1011 * a dequeue/enqueue event is a NOP) 1012 */ 1013 if (se != cfs_rq->curr) 1014 update_stats_wait_start(cfs_rq, se); 1015 1016 if (flags & ENQUEUE_WAKEUP) 1017 update_stats_enqueue_sleeper(cfs_rq, se); 1018 } 1019 1020 static inline void 1021 update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 1022 { 1023 1024 if (!schedstat_enabled()) 1025 return; 1026 1027 /* 1028 * Mark the end of the wait period if dequeueing a 1029 * waiting task: 1030 */ 1031 if (se != cfs_rq->curr) 1032 update_stats_wait_end(cfs_rq, se); 1033 1034 if ((flags & DEQUEUE_SLEEP) && entity_is_task(se)) { 1035 struct task_struct *tsk = task_of(se); 1036 1037 if (tsk->state & TASK_INTERRUPTIBLE) 1038 schedstat_set(se->statistics.sleep_start, 1039 rq_clock(rq_of(cfs_rq))); 1040 if (tsk->state & TASK_UNINTERRUPTIBLE) 1041 schedstat_set(se->statistics.block_start, 1042 rq_clock(rq_of(cfs_rq))); 1043 } 1044 } 1045 1046 /* 1047 * We are picking a new current task - update its stats: 1048 */ 1049 static inline void 1050 update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se) 1051 { 1052 /* 1053 * We are starting a new run period: 1054 */ 1055 se->exec_start = rq_clock_task(rq_of(cfs_rq)); 1056 } 1057 1058 /************************************************** 1059 * Scheduling class queueing methods: 1060 */ 1061 1062 #ifdef CONFIG_NUMA_BALANCING 1063 /* 1064 * Approximate time to scan a full NUMA task in ms. The task scan period is 1065 * calculated based on the tasks virtual memory size and 1066 * numa_balancing_scan_size. 1067 */ 1068 unsigned int sysctl_numa_balancing_scan_period_min = 1000; 1069 unsigned int sysctl_numa_balancing_scan_period_max = 60000; 1070 1071 /* Portion of address space to scan in MB */ 1072 unsigned int sysctl_numa_balancing_scan_size = 256; 1073 1074 /* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */ 1075 unsigned int sysctl_numa_balancing_scan_delay = 1000; 1076 1077 static unsigned int task_nr_scan_windows(struct task_struct *p) 1078 { 1079 unsigned long rss = 0; 1080 unsigned long nr_scan_pages; 1081 1082 /* 1083 * Calculations based on RSS as non-present and empty pages are skipped 1084 * by the PTE scanner and NUMA hinting faults should be trapped based 1085 * on resident pages 1086 */ 1087 nr_scan_pages = sysctl_numa_balancing_scan_size << (20 - PAGE_SHIFT); 1088 rss = get_mm_rss(p->mm); 1089 if (!rss) 1090 rss = nr_scan_pages; 1091 1092 rss = round_up(rss, nr_scan_pages); 1093 return rss / nr_scan_pages; 1094 } 1095 1096 /* For sanitys sake, never scan more PTEs than MAX_SCAN_WINDOW MB/sec. */ 1097 #define MAX_SCAN_WINDOW 2560 1098 1099 static unsigned int task_scan_min(struct task_struct *p) 1100 { 1101 unsigned int scan_size = READ_ONCE(sysctl_numa_balancing_scan_size); 1102 unsigned int scan, floor; 1103 unsigned int windows = 1; 1104 1105 if (scan_size < MAX_SCAN_WINDOW) 1106 windows = MAX_SCAN_WINDOW / scan_size; 1107 floor = 1000 / windows; 1108 1109 scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p); 1110 return max_t(unsigned int, floor, scan); 1111 } 1112 1113 static unsigned int task_scan_max(struct task_struct *p) 1114 { 1115 unsigned int smin = task_scan_min(p); 1116 unsigned int smax; 1117 1118 /* Watch for min being lower than max due to floor calculations */ 1119 smax = sysctl_numa_balancing_scan_period_max / task_nr_scan_windows(p); 1120 return max(smin, smax); 1121 } 1122 1123 static void account_numa_enqueue(struct rq *rq, struct task_struct *p) 1124 { 1125 rq->nr_numa_running += (p->numa_preferred_nid != -1); 1126 rq->nr_preferred_running += (p->numa_preferred_nid == task_node(p)); 1127 } 1128 1129 static void account_numa_dequeue(struct rq *rq, struct task_struct *p) 1130 { 1131 rq->nr_numa_running -= (p->numa_preferred_nid != -1); 1132 rq->nr_preferred_running -= (p->numa_preferred_nid == task_node(p)); 1133 } 1134 1135 struct numa_group { 1136 atomic_t refcount; 1137 1138 spinlock_t lock; /* nr_tasks, tasks */ 1139 int nr_tasks; 1140 pid_t gid; 1141 int active_nodes; 1142 1143 struct rcu_head rcu; 1144 unsigned long total_faults; 1145 unsigned long max_faults_cpu; 1146 /* 1147 * Faults_cpu is used to decide whether memory should move 1148 * towards the CPU. As a consequence, these stats are weighted 1149 * more by CPU use than by memory faults. 1150 */ 1151 unsigned long *faults_cpu; 1152 unsigned long faults[0]; 1153 }; 1154 1155 /* Shared or private faults. */ 1156 #define NR_NUMA_HINT_FAULT_TYPES 2 1157 1158 /* Memory and CPU locality */ 1159 #define NR_NUMA_HINT_FAULT_STATS (NR_NUMA_HINT_FAULT_TYPES * 2) 1160 1161 /* Averaged statistics, and temporary buffers. */ 1162 #define NR_NUMA_HINT_FAULT_BUCKETS (NR_NUMA_HINT_FAULT_STATS * 2) 1163 1164 pid_t task_numa_group_id(struct task_struct *p) 1165 { 1166 return p->numa_group ? p->numa_group->gid : 0; 1167 } 1168 1169 /* 1170 * The averaged statistics, shared & private, memory & cpu, 1171 * occupy the first half of the array. The second half of the 1172 * array is for current counters, which are averaged into the 1173 * first set by task_numa_placement. 1174 */ 1175 static inline int task_faults_idx(enum numa_faults_stats s, int nid, int priv) 1176 { 1177 return NR_NUMA_HINT_FAULT_TYPES * (s * nr_node_ids + nid) + priv; 1178 } 1179 1180 static inline unsigned long task_faults(struct task_struct *p, int nid) 1181 { 1182 if (!p->numa_faults) 1183 return 0; 1184 1185 return p->numa_faults[task_faults_idx(NUMA_MEM, nid, 0)] + 1186 p->numa_faults[task_faults_idx(NUMA_MEM, nid, 1)]; 1187 } 1188 1189 static inline unsigned long group_faults(struct task_struct *p, int nid) 1190 { 1191 if (!p->numa_group) 1192 return 0; 1193 1194 return p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 0)] + 1195 p->numa_group->faults[task_faults_idx(NUMA_MEM, nid, 1)]; 1196 } 1197 1198 static inline unsigned long group_faults_cpu(struct numa_group *group, int nid) 1199 { 1200 return group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 0)] + 1201 group->faults_cpu[task_faults_idx(NUMA_MEM, nid, 1)]; 1202 } 1203 1204 /* 1205 * A node triggering more than 1/3 as many NUMA faults as the maximum is 1206 * considered part of a numa group's pseudo-interleaving set. Migrations 1207 * between these nodes are slowed down, to allow things to settle down. 1208 */ 1209 #define ACTIVE_NODE_FRACTION 3 1210 1211 static bool numa_is_active_node(int nid, struct numa_group *ng) 1212 { 1213 return group_faults_cpu(ng, nid) * ACTIVE_NODE_FRACTION > ng->max_faults_cpu; 1214 } 1215 1216 /* Handle placement on systems where not all nodes are directly connected. */ 1217 static unsigned long score_nearby_nodes(struct task_struct *p, int nid, 1218 int maxdist, bool task) 1219 { 1220 unsigned long score = 0; 1221 int node; 1222 1223 /* 1224 * All nodes are directly connected, and the same distance 1225 * from each other. No need for fancy placement algorithms. 1226 */ 1227 if (sched_numa_topology_type == NUMA_DIRECT) 1228 return 0; 1229 1230 /* 1231 * This code is called for each node, introducing N^2 complexity, 1232 * which should be ok given the number of nodes rarely exceeds 8. 1233 */ 1234 for_each_online_node(node) { 1235 unsigned long faults; 1236 int dist = node_distance(nid, node); 1237 1238 /* 1239 * The furthest away nodes in the system are not interesting 1240 * for placement; nid was already counted. 1241 */ 1242 if (dist == sched_max_numa_distance || node == nid) 1243 continue; 1244 1245 /* 1246 * On systems with a backplane NUMA topology, compare groups 1247 * of nodes, and move tasks towards the group with the most 1248 * memory accesses. When comparing two nodes at distance 1249 * "hoplimit", only nodes closer by than "hoplimit" are part 1250 * of each group. Skip other nodes. 1251 */ 1252 if (sched_numa_topology_type == NUMA_BACKPLANE && 1253 dist > maxdist) 1254 continue; 1255 1256 /* Add up the faults from nearby nodes. */ 1257 if (task) 1258 faults = task_faults(p, node); 1259 else 1260 faults = group_faults(p, node); 1261 1262 /* 1263 * On systems with a glueless mesh NUMA topology, there are 1264 * no fixed "groups of nodes". Instead, nodes that are not 1265 * directly connected bounce traffic through intermediate 1266 * nodes; a numa_group can occupy any set of nodes. 1267 * The further away a node is, the less the faults count. 1268 * This seems to result in good task placement. 1269 */ 1270 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { 1271 faults *= (sched_max_numa_distance - dist); 1272 faults /= (sched_max_numa_distance - LOCAL_DISTANCE); 1273 } 1274 1275 score += faults; 1276 } 1277 1278 return score; 1279 } 1280 1281 /* 1282 * These return the fraction of accesses done by a particular task, or 1283 * task group, on a particular numa node. The group weight is given a 1284 * larger multiplier, in order to group tasks together that are almost 1285 * evenly spread out between numa nodes. 1286 */ 1287 static inline unsigned long task_weight(struct task_struct *p, int nid, 1288 int dist) 1289 { 1290 unsigned long faults, total_faults; 1291 1292 if (!p->numa_faults) 1293 return 0; 1294 1295 total_faults = p->total_numa_faults; 1296 1297 if (!total_faults) 1298 return 0; 1299 1300 faults = task_faults(p, nid); 1301 faults += score_nearby_nodes(p, nid, dist, true); 1302 1303 return 1000 * faults / total_faults; 1304 } 1305 1306 static inline unsigned long group_weight(struct task_struct *p, int nid, 1307 int dist) 1308 { 1309 unsigned long faults, total_faults; 1310 1311 if (!p->numa_group) 1312 return 0; 1313 1314 total_faults = p->numa_group->total_faults; 1315 1316 if (!total_faults) 1317 return 0; 1318 1319 faults = group_faults(p, nid); 1320 faults += score_nearby_nodes(p, nid, dist, false); 1321 1322 return 1000 * faults / total_faults; 1323 } 1324 1325 bool should_numa_migrate_memory(struct task_struct *p, struct page * page, 1326 int src_nid, int dst_cpu) 1327 { 1328 struct numa_group *ng = p->numa_group; 1329 int dst_nid = cpu_to_node(dst_cpu); 1330 int last_cpupid, this_cpupid; 1331 1332 this_cpupid = cpu_pid_to_cpupid(dst_cpu, current->pid); 1333 1334 /* 1335 * Multi-stage node selection is used in conjunction with a periodic 1336 * migration fault to build a temporal task<->page relation. By using 1337 * a two-stage filter we remove short/unlikely relations. 1338 * 1339 * Using P(p) ~ n_p / n_t as per frequentist probability, we can equate 1340 * a task's usage of a particular page (n_p) per total usage of this 1341 * page (n_t) (in a given time-span) to a probability. 1342 * 1343 * Our periodic faults will sample this probability and getting the 1344 * same result twice in a row, given these samples are fully 1345 * independent, is then given by P(n)^2, provided our sample period 1346 * is sufficiently short compared to the usage pattern. 1347 * 1348 * This quadric squishes small probabilities, making it less likely we 1349 * act on an unlikely task<->page relation. 1350 */ 1351 last_cpupid = page_cpupid_xchg_last(page, this_cpupid); 1352 if (!cpupid_pid_unset(last_cpupid) && 1353 cpupid_to_nid(last_cpupid) != dst_nid) 1354 return false; 1355 1356 /* Always allow migrate on private faults */ 1357 if (cpupid_match_pid(p, last_cpupid)) 1358 return true; 1359 1360 /* A shared fault, but p->numa_group has not been set up yet. */ 1361 if (!ng) 1362 return true; 1363 1364 /* 1365 * Destination node is much more heavily used than the source 1366 * node? Allow migration. 1367 */ 1368 if (group_faults_cpu(ng, dst_nid) > group_faults_cpu(ng, src_nid) * 1369 ACTIVE_NODE_FRACTION) 1370 return true; 1371 1372 /* 1373 * Distribute memory according to CPU & memory use on each node, 1374 * with 3/4 hysteresis to avoid unnecessary memory migrations: 1375 * 1376 * faults_cpu(dst) 3 faults_cpu(src) 1377 * --------------- * - > --------------- 1378 * faults_mem(dst) 4 faults_mem(src) 1379 */ 1380 return group_faults_cpu(ng, dst_nid) * group_faults(p, src_nid) * 3 > 1381 group_faults_cpu(ng, src_nid) * group_faults(p, dst_nid) * 4; 1382 } 1383 1384 static unsigned long weighted_cpuload(const int cpu); 1385 static unsigned long source_load(int cpu, int type); 1386 static unsigned long target_load(int cpu, int type); 1387 static unsigned long capacity_of(int cpu); 1388 static long effective_load(struct task_group *tg, int cpu, long wl, long wg); 1389 1390 /* Cached statistics for all CPUs within a node */ 1391 struct numa_stats { 1392 unsigned long nr_running; 1393 unsigned long load; 1394 1395 /* Total compute capacity of CPUs on a node */ 1396 unsigned long compute_capacity; 1397 1398 /* Approximate capacity in terms of runnable tasks on a node */ 1399 unsigned long task_capacity; 1400 int has_free_capacity; 1401 }; 1402 1403 /* 1404 * XXX borrowed from update_sg_lb_stats 1405 */ 1406 static void update_numa_stats(struct numa_stats *ns, int nid) 1407 { 1408 int smt, cpu, cpus = 0; 1409 unsigned long capacity; 1410 1411 memset(ns, 0, sizeof(*ns)); 1412 for_each_cpu(cpu, cpumask_of_node(nid)) { 1413 struct rq *rq = cpu_rq(cpu); 1414 1415 ns->nr_running += rq->nr_running; 1416 ns->load += weighted_cpuload(cpu); 1417 ns->compute_capacity += capacity_of(cpu); 1418 1419 cpus++; 1420 } 1421 1422 /* 1423 * If we raced with hotplug and there are no CPUs left in our mask 1424 * the @ns structure is NULL'ed and task_numa_compare() will 1425 * not find this node attractive. 1426 * 1427 * We'll either bail at !has_free_capacity, or we'll detect a huge 1428 * imbalance and bail there. 1429 */ 1430 if (!cpus) 1431 return; 1432 1433 /* smt := ceil(cpus / capacity), assumes: 1 < smt_power < 2 */ 1434 smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, ns->compute_capacity); 1435 capacity = cpus / smt; /* cores */ 1436 1437 ns->task_capacity = min_t(unsigned, capacity, 1438 DIV_ROUND_CLOSEST(ns->compute_capacity, SCHED_CAPACITY_SCALE)); 1439 ns->has_free_capacity = (ns->nr_running < ns->task_capacity); 1440 } 1441 1442 struct task_numa_env { 1443 struct task_struct *p; 1444 1445 int src_cpu, src_nid; 1446 int dst_cpu, dst_nid; 1447 1448 struct numa_stats src_stats, dst_stats; 1449 1450 int imbalance_pct; 1451 int dist; 1452 1453 struct task_struct *best_task; 1454 long best_imp; 1455 int best_cpu; 1456 }; 1457 1458 static void task_numa_assign(struct task_numa_env *env, 1459 struct task_struct *p, long imp) 1460 { 1461 if (env->best_task) 1462 put_task_struct(env->best_task); 1463 if (p) 1464 get_task_struct(p); 1465 1466 env->best_task = p; 1467 env->best_imp = imp; 1468 env->best_cpu = env->dst_cpu; 1469 } 1470 1471 static bool load_too_imbalanced(long src_load, long dst_load, 1472 struct task_numa_env *env) 1473 { 1474 long imb, old_imb; 1475 long orig_src_load, orig_dst_load; 1476 long src_capacity, dst_capacity; 1477 1478 /* 1479 * The load is corrected for the CPU capacity available on each node. 1480 * 1481 * src_load dst_load 1482 * ------------ vs --------- 1483 * src_capacity dst_capacity 1484 */ 1485 src_capacity = env->src_stats.compute_capacity; 1486 dst_capacity = env->dst_stats.compute_capacity; 1487 1488 /* We care about the slope of the imbalance, not the direction. */ 1489 if (dst_load < src_load) 1490 swap(dst_load, src_load); 1491 1492 /* Is the difference below the threshold? */ 1493 imb = dst_load * src_capacity * 100 - 1494 src_load * dst_capacity * env->imbalance_pct; 1495 if (imb <= 0) 1496 return false; 1497 1498 /* 1499 * The imbalance is above the allowed threshold. 1500 * Compare it with the old imbalance. 1501 */ 1502 orig_src_load = env->src_stats.load; 1503 orig_dst_load = env->dst_stats.load; 1504 1505 if (orig_dst_load < orig_src_load) 1506 swap(orig_dst_load, orig_src_load); 1507 1508 old_imb = orig_dst_load * src_capacity * 100 - 1509 orig_src_load * dst_capacity * env->imbalance_pct; 1510 1511 /* Would this change make things worse? */ 1512 return (imb > old_imb); 1513 } 1514 1515 /* 1516 * This checks if the overall compute and NUMA accesses of the system would 1517 * be improved if the source tasks was migrated to the target dst_cpu taking 1518 * into account that it might be best if task running on the dst_cpu should 1519 * be exchanged with the source task 1520 */ 1521 static void task_numa_compare(struct task_numa_env *env, 1522 long taskimp, long groupimp) 1523 { 1524 struct rq *src_rq = cpu_rq(env->src_cpu); 1525 struct rq *dst_rq = cpu_rq(env->dst_cpu); 1526 struct task_struct *cur; 1527 long src_load, dst_load; 1528 long load; 1529 long imp = env->p->numa_group ? groupimp : taskimp; 1530 long moveimp = imp; 1531 int dist = env->dist; 1532 1533 rcu_read_lock(); 1534 cur = task_rcu_dereference(&dst_rq->curr); 1535 if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) 1536 cur = NULL; 1537 1538 /* 1539 * Because we have preemption enabled we can get migrated around and 1540 * end try selecting ourselves (current == env->p) as a swap candidate. 1541 */ 1542 if (cur == env->p) 1543 goto unlock; 1544 1545 /* 1546 * "imp" is the fault differential for the source task between the 1547 * source and destination node. Calculate the total differential for 1548 * the source task and potential destination task. The more negative 1549 * the value is, the more rmeote accesses that would be expected to 1550 * be incurred if the tasks were swapped. 1551 */ 1552 if (cur) { 1553 /* Skip this swap candidate if cannot move to the source cpu */ 1554 if (!cpumask_test_cpu(env->src_cpu, tsk_cpus_allowed(cur))) 1555 goto unlock; 1556 1557 /* 1558 * If dst and source tasks are in the same NUMA group, or not 1559 * in any group then look only at task weights. 1560 */ 1561 if (cur->numa_group == env->p->numa_group) { 1562 imp = taskimp + task_weight(cur, env->src_nid, dist) - 1563 task_weight(cur, env->dst_nid, dist); 1564 /* 1565 * Add some hysteresis to prevent swapping the 1566 * tasks within a group over tiny differences. 1567 */ 1568 if (cur->numa_group) 1569 imp -= imp/16; 1570 } else { 1571 /* 1572 * Compare the group weights. If a task is all by 1573 * itself (not part of a group), use the task weight 1574 * instead. 1575 */ 1576 if (cur->numa_group) 1577 imp += group_weight(cur, env->src_nid, dist) - 1578 group_weight(cur, env->dst_nid, dist); 1579 else 1580 imp += task_weight(cur, env->src_nid, dist) - 1581 task_weight(cur, env->dst_nid, dist); 1582 } 1583 } 1584 1585 if (imp <= env->best_imp && moveimp <= env->best_imp) 1586 goto unlock; 1587 1588 if (!cur) { 1589 /* Is there capacity at our destination? */ 1590 if (env->src_stats.nr_running <= env->src_stats.task_capacity && 1591 !env->dst_stats.has_free_capacity) 1592 goto unlock; 1593 1594 goto balance; 1595 } 1596 1597 /* Balance doesn't matter much if we're running a task per cpu */ 1598 if (imp > env->best_imp && src_rq->nr_running == 1 && 1599 dst_rq->nr_running == 1) 1600 goto assign; 1601 1602 /* 1603 * In the overloaded case, try and keep the load balanced. 1604 */ 1605 balance: 1606 load = task_h_load(env->p); 1607 dst_load = env->dst_stats.load + load; 1608 src_load = env->src_stats.load - load; 1609 1610 if (moveimp > imp && moveimp > env->best_imp) { 1611 /* 1612 * If the improvement from just moving env->p direction is 1613 * better than swapping tasks around, check if a move is 1614 * possible. Store a slightly smaller score than moveimp, 1615 * so an actually idle CPU will win. 1616 */ 1617 if (!load_too_imbalanced(src_load, dst_load, env)) { 1618 imp = moveimp - 1; 1619 cur = NULL; 1620 goto assign; 1621 } 1622 } 1623 1624 if (imp <= env->best_imp) 1625 goto unlock; 1626 1627 if (cur) { 1628 load = task_h_load(cur); 1629 dst_load -= load; 1630 src_load += load; 1631 } 1632 1633 if (load_too_imbalanced(src_load, dst_load, env)) 1634 goto unlock; 1635 1636 /* 1637 * One idle CPU per node is evaluated for a task numa move. 1638 * Call select_idle_sibling to maybe find a better one. 1639 */ 1640 if (!cur) { 1641 /* 1642 * select_idle_siblings() uses an per-cpu cpumask that 1643 * can be used from IRQ context. 1644 */ 1645 local_irq_disable(); 1646 env->dst_cpu = select_idle_sibling(env->p, env->src_cpu, 1647 env->dst_cpu); 1648 local_irq_enable(); 1649 } 1650 1651 assign: 1652 task_numa_assign(env, cur, imp); 1653 unlock: 1654 rcu_read_unlock(); 1655 } 1656 1657 static void task_numa_find_cpu(struct task_numa_env *env, 1658 long taskimp, long groupimp) 1659 { 1660 int cpu; 1661 1662 for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) { 1663 /* Skip this CPU if the source task cannot migrate */ 1664 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(env->p))) 1665 continue; 1666 1667 env->dst_cpu = cpu; 1668 task_numa_compare(env, taskimp, groupimp); 1669 } 1670 } 1671 1672 /* Only move tasks to a NUMA node less busy than the current node. */ 1673 static bool numa_has_capacity(struct task_numa_env *env) 1674 { 1675 struct numa_stats *src = &env->src_stats; 1676 struct numa_stats *dst = &env->dst_stats; 1677 1678 if (src->has_free_capacity && !dst->has_free_capacity) 1679 return false; 1680 1681 /* 1682 * Only consider a task move if the source has a higher load 1683 * than the destination, corrected for CPU capacity on each node. 1684 * 1685 * src->load dst->load 1686 * --------------------- vs --------------------- 1687 * src->compute_capacity dst->compute_capacity 1688 */ 1689 if (src->load * dst->compute_capacity * env->imbalance_pct > 1690 1691 dst->load * src->compute_capacity * 100) 1692 return true; 1693 1694 return false; 1695 } 1696 1697 static int task_numa_migrate(struct task_struct *p) 1698 { 1699 struct task_numa_env env = { 1700 .p = p, 1701 1702 .src_cpu = task_cpu(p), 1703 .src_nid = task_node(p), 1704 1705 .imbalance_pct = 112, 1706 1707 .best_task = NULL, 1708 .best_imp = 0, 1709 .best_cpu = -1, 1710 }; 1711 struct sched_domain *sd; 1712 unsigned long taskweight, groupweight; 1713 int nid, ret, dist; 1714 long taskimp, groupimp; 1715 1716 /* 1717 * Pick the lowest SD_NUMA domain, as that would have the smallest 1718 * imbalance and would be the first to start moving tasks about. 1719 * 1720 * And we want to avoid any moving of tasks about, as that would create 1721 * random movement of tasks -- counter the numa conditions we're trying 1722 * to satisfy here. 1723 */ 1724 rcu_read_lock(); 1725 sd = rcu_dereference(per_cpu(sd_numa, env.src_cpu)); 1726 if (sd) 1727 env.imbalance_pct = 100 + (sd->imbalance_pct - 100) / 2; 1728 rcu_read_unlock(); 1729 1730 /* 1731 * Cpusets can break the scheduler domain tree into smaller 1732 * balance domains, some of which do not cross NUMA boundaries. 1733 * Tasks that are "trapped" in such domains cannot be migrated 1734 * elsewhere, so there is no point in (re)trying. 1735 */ 1736 if (unlikely(!sd)) { 1737 p->numa_preferred_nid = task_node(p); 1738 return -EINVAL; 1739 } 1740 1741 env.dst_nid = p->numa_preferred_nid; 1742 dist = env.dist = node_distance(env.src_nid, env.dst_nid); 1743 taskweight = task_weight(p, env.src_nid, dist); 1744 groupweight = group_weight(p, env.src_nid, dist); 1745 update_numa_stats(&env.src_stats, env.src_nid); 1746 taskimp = task_weight(p, env.dst_nid, dist) - taskweight; 1747 groupimp = group_weight(p, env.dst_nid, dist) - groupweight; 1748 update_numa_stats(&env.dst_stats, env.dst_nid); 1749 1750 /* Try to find a spot on the preferred nid. */ 1751 if (numa_has_capacity(&env)) 1752 task_numa_find_cpu(&env, taskimp, groupimp); 1753 1754 /* 1755 * Look at other nodes in these cases: 1756 * - there is no space available on the preferred_nid 1757 * - the task is part of a numa_group that is interleaved across 1758 * multiple NUMA nodes; in order to better consolidate the group, 1759 * we need to check other locations. 1760 */ 1761 if (env.best_cpu == -1 || (p->numa_group && p->numa_group->active_nodes > 1)) { 1762 for_each_online_node(nid) { 1763 if (nid == env.src_nid || nid == p->numa_preferred_nid) 1764 continue; 1765 1766 dist = node_distance(env.src_nid, env.dst_nid); 1767 if (sched_numa_topology_type == NUMA_BACKPLANE && 1768 dist != env.dist) { 1769 taskweight = task_weight(p, env.src_nid, dist); 1770 groupweight = group_weight(p, env.src_nid, dist); 1771 } 1772 1773 /* Only consider nodes where both task and groups benefit */ 1774 taskimp = task_weight(p, nid, dist) - taskweight; 1775 groupimp = group_weight(p, nid, dist) - groupweight; 1776 if (taskimp < 0 && groupimp < 0) 1777 continue; 1778 1779 env.dist = dist; 1780 env.dst_nid = nid; 1781 update_numa_stats(&env.dst_stats, env.dst_nid); 1782 if (numa_has_capacity(&env)) 1783 task_numa_find_cpu(&env, taskimp, groupimp); 1784 } 1785 } 1786 1787 /* 1788 * If the task is part of a workload that spans multiple NUMA nodes, 1789 * and is migrating into one of the workload's active nodes, remember 1790 * this node as the task's preferred numa node, so the workload can 1791 * settle down. 1792 * A task that migrated to a second choice node will be better off 1793 * trying for a better one later. Do not set the preferred node here. 1794 */ 1795 if (p->numa_group) { 1796 struct numa_group *ng = p->numa_group; 1797 1798 if (env.best_cpu == -1) 1799 nid = env.src_nid; 1800 else 1801 nid = env.dst_nid; 1802 1803 if (ng->active_nodes > 1 && numa_is_active_node(env.dst_nid, ng)) 1804 sched_setnuma(p, env.dst_nid); 1805 } 1806 1807 /* No better CPU than the current one was found. */ 1808 if (env.best_cpu == -1) 1809 return -EAGAIN; 1810 1811 /* 1812 * Reset the scan period if the task is being rescheduled on an 1813 * alternative node to recheck if the tasks is now properly placed. 1814 */ 1815 p->numa_scan_period = task_scan_min(p); 1816 1817 if (env.best_task == NULL) { 1818 ret = migrate_task_to(p, env.best_cpu); 1819 if (ret != 0) 1820 trace_sched_stick_numa(p, env.src_cpu, env.best_cpu); 1821 return ret; 1822 } 1823 1824 ret = migrate_swap(p, env.best_task); 1825 if (ret != 0) 1826 trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task)); 1827 put_task_struct(env.best_task); 1828 return ret; 1829 } 1830 1831 /* Attempt to migrate a task to a CPU on the preferred node. */ 1832 static void numa_migrate_preferred(struct task_struct *p) 1833 { 1834 unsigned long interval = HZ; 1835 1836 /* This task has no NUMA fault statistics yet */ 1837 if (unlikely(p->numa_preferred_nid == -1 || !p->numa_faults)) 1838 return; 1839 1840 /* Periodically retry migrating the task to the preferred node */ 1841 interval = min(interval, msecs_to_jiffies(p->numa_scan_period) / 16); 1842 p->numa_migrate_retry = jiffies + interval; 1843 1844 /* Success if task is already running on preferred CPU */ 1845 if (task_node(p) == p->numa_preferred_nid) 1846 return; 1847 1848 /* Otherwise, try migrate to a CPU on the preferred node */ 1849 task_numa_migrate(p); 1850 } 1851 1852 /* 1853 * Find out how many nodes on the workload is actively running on. Do this by 1854 * tracking the nodes from which NUMA hinting faults are triggered. This can 1855 * be different from the set of nodes where the workload's memory is currently 1856 * located. 1857 */ 1858 static void numa_group_count_active_nodes(struct numa_group *numa_group) 1859 { 1860 unsigned long faults, max_faults = 0; 1861 int nid, active_nodes = 0; 1862 1863 for_each_online_node(nid) { 1864 faults = group_faults_cpu(numa_group, nid); 1865 if (faults > max_faults) 1866 max_faults = faults; 1867 } 1868 1869 for_each_online_node(nid) { 1870 faults = group_faults_cpu(numa_group, nid); 1871 if (faults * ACTIVE_NODE_FRACTION > max_faults) 1872 active_nodes++; 1873 } 1874 1875 numa_group->max_faults_cpu = max_faults; 1876 numa_group->active_nodes = active_nodes; 1877 } 1878 1879 /* 1880 * When adapting the scan rate, the period is divided into NUMA_PERIOD_SLOTS 1881 * increments. The more local the fault statistics are, the higher the scan 1882 * period will be for the next scan window. If local/(local+remote) ratio is 1883 * below NUMA_PERIOD_THRESHOLD (where range of ratio is 1..NUMA_PERIOD_SLOTS) 1884 * the scan period will decrease. Aim for 70% local accesses. 1885 */ 1886 #define NUMA_PERIOD_SLOTS 10 1887 #define NUMA_PERIOD_THRESHOLD 7 1888 1889 /* 1890 * Increase the scan period (slow down scanning) if the majority of 1891 * our memory is already on our local node, or if the majority of 1892 * the page accesses are shared with other processes. 1893 * Otherwise, decrease the scan period. 1894 */ 1895 static void update_task_scan_period(struct task_struct *p, 1896 unsigned long shared, unsigned long private) 1897 { 1898 unsigned int period_slot; 1899 int ratio; 1900 int diff; 1901 1902 unsigned long remote = p->numa_faults_locality[0]; 1903 unsigned long local = p->numa_faults_locality[1]; 1904 1905 /* 1906 * If there were no record hinting faults then either the task is 1907 * completely idle or all activity is areas that are not of interest 1908 * to automatic numa balancing. Related to that, if there were failed 1909 * migration then it implies we are migrating too quickly or the local 1910 * node is overloaded. In either case, scan slower 1911 */ 1912 if (local + shared == 0 || p->numa_faults_locality[2]) { 1913 p->numa_scan_period = min(p->numa_scan_period_max, 1914 p->numa_scan_period << 1); 1915 1916 p->mm->numa_next_scan = jiffies + 1917 msecs_to_jiffies(p->numa_scan_period); 1918 1919 return; 1920 } 1921 1922 /* 1923 * Prepare to scale scan period relative to the current period. 1924 * == NUMA_PERIOD_THRESHOLD scan period stays the same 1925 * < NUMA_PERIOD_THRESHOLD scan period decreases (scan faster) 1926 * >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower) 1927 */ 1928 period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS); 1929 ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote); 1930 if (ratio >= NUMA_PERIOD_THRESHOLD) { 1931 int slot = ratio - NUMA_PERIOD_THRESHOLD; 1932 if (!slot) 1933 slot = 1; 1934 diff = slot * period_slot; 1935 } else { 1936 diff = -(NUMA_PERIOD_THRESHOLD - ratio) * period_slot; 1937 1938 /* 1939 * Scale scan rate increases based on sharing. There is an 1940 * inverse relationship between the degree of sharing and 1941 * the adjustment made to the scanning period. Broadly 1942 * speaking the intent is that there is little point 1943 * scanning faster if shared accesses dominate as it may 1944 * simply bounce migrations uselessly 1945 */ 1946 ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1)); 1947 diff = (diff * ratio) / NUMA_PERIOD_SLOTS; 1948 } 1949 1950 p->numa_scan_period = clamp(p->numa_scan_period + diff, 1951 task_scan_min(p), task_scan_max(p)); 1952 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 1953 } 1954 1955 /* 1956 * Get the fraction of time the task has been running since the last 1957 * NUMA placement cycle. The scheduler keeps similar statistics, but 1958 * decays those on a 32ms period, which is orders of magnitude off 1959 * from the dozens-of-seconds NUMA balancing period. Use the scheduler 1960 * stats only if the task is so new there are no NUMA statistics yet. 1961 */ 1962 static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period) 1963 { 1964 u64 runtime, delta, now; 1965 /* Use the start of this time slice to avoid calculations. */ 1966 now = p->se.exec_start; 1967 runtime = p->se.sum_exec_runtime; 1968 1969 if (p->last_task_numa_placement) { 1970 delta = runtime - p->last_sum_exec_runtime; 1971 *period = now - p->last_task_numa_placement; 1972 } else { 1973 delta = p->se.avg.load_sum / p->se.load.weight; 1974 *period = LOAD_AVG_MAX; 1975 } 1976 1977 p->last_sum_exec_runtime = runtime; 1978 p->last_task_numa_placement = now; 1979 1980 return delta; 1981 } 1982 1983 /* 1984 * Determine the preferred nid for a task in a numa_group. This needs to 1985 * be done in a way that produces consistent results with group_weight, 1986 * otherwise workloads might not converge. 1987 */ 1988 static int preferred_group_nid(struct task_struct *p, int nid) 1989 { 1990 nodemask_t nodes; 1991 int dist; 1992 1993 /* Direct connections between all NUMA nodes. */ 1994 if (sched_numa_topology_type == NUMA_DIRECT) 1995 return nid; 1996 1997 /* 1998 * On a system with glueless mesh NUMA topology, group_weight 1999 * scores nodes according to the number of NUMA hinting faults on 2000 * both the node itself, and on nearby nodes. 2001 */ 2002 if (sched_numa_topology_type == NUMA_GLUELESS_MESH) { 2003 unsigned long score, max_score = 0; 2004 int node, max_node = nid; 2005 2006 dist = sched_max_numa_distance; 2007 2008 for_each_online_node(node) { 2009 score = group_weight(p, node, dist); 2010 if (score > max_score) { 2011 max_score = score; 2012 max_node = node; 2013 } 2014 } 2015 return max_node; 2016 } 2017 2018 /* 2019 * Finding the preferred nid in a system with NUMA backplane 2020 * interconnect topology is more involved. The goal is to locate 2021 * tasks from numa_groups near each other in the system, and 2022 * untangle workloads from different sides of the system. This requires 2023 * searching down the hierarchy of node groups, recursively searching 2024 * inside the highest scoring group of nodes. The nodemask tricks 2025 * keep the complexity of the search down. 2026 */ 2027 nodes = node_online_map; 2028 for (dist = sched_max_numa_distance; dist > LOCAL_DISTANCE; dist--) { 2029 unsigned long max_faults = 0; 2030 nodemask_t max_group = NODE_MASK_NONE; 2031 int a, b; 2032 2033 /* Are there nodes at this distance from each other? */ 2034 if (!find_numa_distance(dist)) 2035 continue; 2036 2037 for_each_node_mask(a, nodes) { 2038 unsigned long faults = 0; 2039 nodemask_t this_group; 2040 nodes_clear(this_group); 2041 2042 /* Sum group's NUMA faults; includes a==b case. */ 2043 for_each_node_mask(b, nodes) { 2044 if (node_distance(a, b) < dist) { 2045 faults += group_faults(p, b); 2046 node_set(b, this_group); 2047 node_clear(b, nodes); 2048 } 2049 } 2050 2051 /* Remember the top group. */ 2052 if (faults > max_faults) { 2053 max_faults = faults; 2054 max_group = this_group; 2055 /* 2056 * subtle: at the smallest distance there is 2057 * just one node left in each "group", the 2058 * winner is the preferred nid. 2059 */ 2060 nid = a; 2061 } 2062 } 2063 /* Next round, evaluate the nodes within max_group. */ 2064 if (!max_faults) 2065 break; 2066 nodes = max_group; 2067 } 2068 return nid; 2069 } 2070 2071 static void task_numa_placement(struct task_struct *p) 2072 { 2073 int seq, nid, max_nid = -1, max_group_nid = -1; 2074 unsigned long max_faults = 0, max_group_faults = 0; 2075 unsigned long fault_types[2] = { 0, 0 }; 2076 unsigned long total_faults; 2077 u64 runtime, period; 2078 spinlock_t *group_lock = NULL; 2079 2080 /* 2081 * The p->mm->numa_scan_seq field gets updated without 2082 * exclusive access. Use READ_ONCE() here to ensure 2083 * that the field is read in a single access: 2084 */ 2085 seq = READ_ONCE(p->mm->numa_scan_seq); 2086 if (p->numa_scan_seq == seq) 2087 return; 2088 p->numa_scan_seq = seq; 2089 p->numa_scan_period_max = task_scan_max(p); 2090 2091 total_faults = p->numa_faults_locality[0] + 2092 p->numa_faults_locality[1]; 2093 runtime = numa_get_avg_runtime(p, &period); 2094 2095 /* If the task is part of a group prevent parallel updates to group stats */ 2096 if (p->numa_group) { 2097 group_lock = &p->numa_group->lock; 2098 spin_lock_irq(group_lock); 2099 } 2100 2101 /* Find the node with the highest number of faults */ 2102 for_each_online_node(nid) { 2103 /* Keep track of the offsets in numa_faults array */ 2104 int mem_idx, membuf_idx, cpu_idx, cpubuf_idx; 2105 unsigned long faults = 0, group_faults = 0; 2106 int priv; 2107 2108 for (priv = 0; priv < NR_NUMA_HINT_FAULT_TYPES; priv++) { 2109 long diff, f_diff, f_weight; 2110 2111 mem_idx = task_faults_idx(NUMA_MEM, nid, priv); 2112 membuf_idx = task_faults_idx(NUMA_MEMBUF, nid, priv); 2113 cpu_idx = task_faults_idx(NUMA_CPU, nid, priv); 2114 cpubuf_idx = task_faults_idx(NUMA_CPUBUF, nid, priv); 2115 2116 /* Decay existing window, copy faults since last scan */ 2117 diff = p->numa_faults[membuf_idx] - p->numa_faults[mem_idx] / 2; 2118 fault_types[priv] += p->numa_faults[membuf_idx]; 2119 p->numa_faults[membuf_idx] = 0; 2120 2121 /* 2122 * Normalize the faults_from, so all tasks in a group 2123 * count according to CPU use, instead of by the raw 2124 * number of faults. Tasks with little runtime have 2125 * little over-all impact on throughput, and thus their 2126 * faults are less important. 2127 */ 2128 f_weight = div64_u64(runtime << 16, period + 1); 2129 f_weight = (f_weight * p->numa_faults[cpubuf_idx]) / 2130 (total_faults + 1); 2131 f_diff = f_weight - p->numa_faults[cpu_idx] / 2; 2132 p->numa_faults[cpubuf_idx] = 0; 2133 2134 p->numa_faults[mem_idx] += diff; 2135 p->numa_faults[cpu_idx] += f_diff; 2136 faults += p->numa_faults[mem_idx]; 2137 p->total_numa_faults += diff; 2138 if (p->numa_group) { 2139 /* 2140 * safe because we can only change our own group 2141 * 2142 * mem_idx represents the offset for a given 2143 * nid and priv in a specific region because it 2144 * is at the beginning of the numa_faults array. 2145 */ 2146 p->numa_group->faults[mem_idx] += diff; 2147 p->numa_group->faults_cpu[mem_idx] += f_diff; 2148 p->numa_group->total_faults += diff; 2149 group_faults += p->numa_group->faults[mem_idx]; 2150 } 2151 } 2152 2153 if (faults > max_faults) { 2154 max_faults = faults; 2155 max_nid = nid; 2156 } 2157 2158 if (group_faults > max_group_faults) { 2159 max_group_faults = group_faults; 2160 max_group_nid = nid; 2161 } 2162 } 2163 2164 update_task_scan_period(p, fault_types[0], fault_types[1]); 2165 2166 if (p->numa_group) { 2167 numa_group_count_active_nodes(p->numa_group); 2168 spin_unlock_irq(group_lock); 2169 max_nid = preferred_group_nid(p, max_group_nid); 2170 } 2171 2172 if (max_faults) { 2173 /* Set the new preferred node */ 2174 if (max_nid != p->numa_preferred_nid) 2175 sched_setnuma(p, max_nid); 2176 2177 if (task_node(p) != p->numa_preferred_nid) 2178 numa_migrate_preferred(p); 2179 } 2180 } 2181 2182 static inline int get_numa_group(struct numa_group *grp) 2183 { 2184 return atomic_inc_not_zero(&grp->refcount); 2185 } 2186 2187 static inline void put_numa_group(struct numa_group *grp) 2188 { 2189 if (atomic_dec_and_test(&grp->refcount)) 2190 kfree_rcu(grp, rcu); 2191 } 2192 2193 static void task_numa_group(struct task_struct *p, int cpupid, int flags, 2194 int *priv) 2195 { 2196 struct numa_group *grp, *my_grp; 2197 struct task_struct *tsk; 2198 bool join = false; 2199 int cpu = cpupid_to_cpu(cpupid); 2200 int i; 2201 2202 if (unlikely(!p->numa_group)) { 2203 unsigned int size = sizeof(struct numa_group) + 2204 4*nr_node_ids*sizeof(unsigned long); 2205 2206 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN); 2207 if (!grp) 2208 return; 2209 2210 atomic_set(&grp->refcount, 1); 2211 grp->active_nodes = 1; 2212 grp->max_faults_cpu = 0; 2213 spin_lock_init(&grp->lock); 2214 grp->gid = p->pid; 2215 /* Second half of the array tracks nids where faults happen */ 2216 grp->faults_cpu = grp->faults + NR_NUMA_HINT_FAULT_TYPES * 2217 nr_node_ids; 2218 2219 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 2220 grp->faults[i] = p->numa_faults[i]; 2221 2222 grp->total_faults = p->total_numa_faults; 2223 2224 grp->nr_tasks++; 2225 rcu_assign_pointer(p->numa_group, grp); 2226 } 2227 2228 rcu_read_lock(); 2229 tsk = READ_ONCE(cpu_rq(cpu)->curr); 2230 2231 if (!cpupid_match_pid(tsk, cpupid)) 2232 goto no_join; 2233 2234 grp = rcu_dereference(tsk->numa_group); 2235 if (!grp) 2236 goto no_join; 2237 2238 my_grp = p->numa_group; 2239 if (grp == my_grp) 2240 goto no_join; 2241 2242 /* 2243 * Only join the other group if its bigger; if we're the bigger group, 2244 * the other task will join us. 2245 */ 2246 if (my_grp->nr_tasks > grp->nr_tasks) 2247 goto no_join; 2248 2249 /* 2250 * Tie-break on the grp address. 2251 */ 2252 if (my_grp->nr_tasks == grp->nr_tasks && my_grp > grp) 2253 goto no_join; 2254 2255 /* Always join threads in the same process. */ 2256 if (tsk->mm == current->mm) 2257 join = true; 2258 2259 /* Simple filter to avoid false positives due to PID collisions */ 2260 if (flags & TNF_SHARED) 2261 join = true; 2262 2263 /* Update priv based on whether false sharing was detected */ 2264 *priv = !join; 2265 2266 if (join && !get_numa_group(grp)) 2267 goto no_join; 2268 2269 rcu_read_unlock(); 2270 2271 if (!join) 2272 return; 2273 2274 BUG_ON(irqs_disabled()); 2275 double_lock_irq(&my_grp->lock, &grp->lock); 2276 2277 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) { 2278 my_grp->faults[i] -= p->numa_faults[i]; 2279 grp->faults[i] += p->numa_faults[i]; 2280 } 2281 my_grp->total_faults -= p->total_numa_faults; 2282 grp->total_faults += p->total_numa_faults; 2283 2284 my_grp->nr_tasks--; 2285 grp->nr_tasks++; 2286 2287 spin_unlock(&my_grp->lock); 2288 spin_unlock_irq(&grp->lock); 2289 2290 rcu_assign_pointer(p->numa_group, grp); 2291 2292 put_numa_group(my_grp); 2293 return; 2294 2295 no_join: 2296 rcu_read_unlock(); 2297 return; 2298 } 2299 2300 void task_numa_free(struct task_struct *p) 2301 { 2302 struct numa_group *grp = p->numa_group; 2303 void *numa_faults = p->numa_faults; 2304 unsigned long flags; 2305 int i; 2306 2307 if (grp) { 2308 spin_lock_irqsave(&grp->lock, flags); 2309 for (i = 0; i < NR_NUMA_HINT_FAULT_STATS * nr_node_ids; i++) 2310 grp->faults[i] -= p->numa_faults[i]; 2311 grp->total_faults -= p->total_numa_faults; 2312 2313 grp->nr_tasks--; 2314 spin_unlock_irqrestore(&grp->lock, flags); 2315 RCU_INIT_POINTER(p->numa_group, NULL); 2316 put_numa_group(grp); 2317 } 2318 2319 p->numa_faults = NULL; 2320 kfree(numa_faults); 2321 } 2322 2323 /* 2324 * Got a PROT_NONE fault for a page on @node. 2325 */ 2326 void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags) 2327 { 2328 struct task_struct *p = current; 2329 bool migrated = flags & TNF_MIGRATED; 2330 int cpu_node = task_node(current); 2331 int local = !!(flags & TNF_FAULT_LOCAL); 2332 struct numa_group *ng; 2333 int priv; 2334 2335 if (!static_branch_likely(&sched_numa_balancing)) 2336 return; 2337 2338 /* for example, ksmd faulting in a user's mm */ 2339 if (!p->mm) 2340 return; 2341 2342 /* Allocate buffer to track faults on a per-node basis */ 2343 if (unlikely(!p->numa_faults)) { 2344 int size = sizeof(*p->numa_faults) * 2345 NR_NUMA_HINT_FAULT_BUCKETS * nr_node_ids; 2346 2347 p->numa_faults = kzalloc(size, GFP_KERNEL|__GFP_NOWARN); 2348 if (!p->numa_faults) 2349 return; 2350 2351 p->total_numa_faults = 0; 2352 memset(p->numa_faults_locality, 0, sizeof(p->numa_faults_locality)); 2353 } 2354 2355 /* 2356 * First accesses are treated as private, otherwise consider accesses 2357 * to be private if the accessing pid has not changed 2358 */ 2359 if (unlikely(last_cpupid == (-1 & LAST_CPUPID_MASK))) { 2360 priv = 1; 2361 } else { 2362 priv = cpupid_match_pid(p, last_cpupid); 2363 if (!priv && !(flags & TNF_NO_GROUP)) 2364 task_numa_group(p, last_cpupid, flags, &priv); 2365 } 2366 2367 /* 2368 * If a workload spans multiple NUMA nodes, a shared fault that 2369 * occurs wholly within the set of nodes that the workload is 2370 * actively using should be counted as local. This allows the 2371 * scan rate to slow down when a workload has settled down. 2372 */ 2373 ng = p->numa_group; 2374 if (!priv && !local && ng && ng->active_nodes > 1 && 2375 numa_is_active_node(cpu_node, ng) && 2376 numa_is_active_node(mem_node, ng)) 2377 local = 1; 2378 2379 task_numa_placement(p); 2380 2381 /* 2382 * Retry task to preferred node migration periodically, in case it 2383 * case it previously failed, or the scheduler moved us. 2384 */ 2385 if (time_after(jiffies, p->numa_migrate_retry)) 2386 numa_migrate_preferred(p); 2387 2388 if (migrated) 2389 p->numa_pages_migrated += pages; 2390 if (flags & TNF_MIGRATE_FAIL) 2391 p->numa_faults_locality[2] += pages; 2392 2393 p->numa_faults[task_faults_idx(NUMA_MEMBUF, mem_node, priv)] += pages; 2394 p->numa_faults[task_faults_idx(NUMA_CPUBUF, cpu_node, priv)] += pages; 2395 p->numa_faults_locality[local] += pages; 2396 } 2397 2398 static void reset_ptenuma_scan(struct task_struct *p) 2399 { 2400 /* 2401 * We only did a read acquisition of the mmap sem, so 2402 * p->mm->numa_scan_seq is written to without exclusive access 2403 * and the update is not guaranteed to be atomic. That's not 2404 * much of an issue though, since this is just used for 2405 * statistical sampling. Use READ_ONCE/WRITE_ONCE, which are not 2406 * expensive, to avoid any form of compiler optimizations: 2407 */ 2408 WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1); 2409 p->mm->numa_scan_offset = 0; 2410 } 2411 2412 /* 2413 * The expensive part of numa migration is done from task_work context. 2414 * Triggered from task_tick_numa(). 2415 */ 2416 void task_numa_work(struct callback_head *work) 2417 { 2418 unsigned long migrate, next_scan, now = jiffies; 2419 struct task_struct *p = current; 2420 struct mm_struct *mm = p->mm; 2421 u64 runtime = p->se.sum_exec_runtime; 2422 struct vm_area_struct *vma; 2423 unsigned long start, end; 2424 unsigned long nr_pte_updates = 0; 2425 long pages, virtpages; 2426 2427 SCHED_WARN_ON(p != container_of(work, struct task_struct, numa_work)); 2428 2429 work->next = work; /* protect against double add */ 2430 /* 2431 * Who cares about NUMA placement when they're dying. 2432 * 2433 * NOTE: make sure not to dereference p->mm before this check, 2434 * exit_task_work() happens _after_ exit_mm() so we could be called 2435 * without p->mm even though we still had it when we enqueued this 2436 * work. 2437 */ 2438 if (p->flags & PF_EXITING) 2439 return; 2440 2441 if (!mm->numa_next_scan) { 2442 mm->numa_next_scan = now + 2443 msecs_to_jiffies(sysctl_numa_balancing_scan_delay); 2444 } 2445 2446 /* 2447 * Enforce maximal scan/migration frequency.. 2448 */ 2449 migrate = mm->numa_next_scan; 2450 if (time_before(now, migrate)) 2451 return; 2452 2453 if (p->numa_scan_period == 0) { 2454 p->numa_scan_period_max = task_scan_max(p); 2455 p->numa_scan_period = task_scan_min(p); 2456 } 2457 2458 next_scan = now + msecs_to_jiffies(p->numa_scan_period); 2459 if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate) 2460 return; 2461 2462 /* 2463 * Delay this task enough that another task of this mm will likely win 2464 * the next time around. 2465 */ 2466 p->node_stamp += 2 * TICK_NSEC; 2467 2468 start = mm->numa_scan_offset; 2469 pages = sysctl_numa_balancing_scan_size; 2470 pages <<= 20 - PAGE_SHIFT; /* MB in pages */ 2471 virtpages = pages * 8; /* Scan up to this much virtual space */ 2472 if (!pages) 2473 return; 2474 2475 2476 down_read(&mm->mmap_sem); 2477 vma = find_vma(mm, start); 2478 if (!vma) { 2479 reset_ptenuma_scan(p); 2480 start = 0; 2481 vma = mm->mmap; 2482 } 2483 for (; vma; vma = vma->vm_next) { 2484 if (!vma_migratable(vma) || !vma_policy_mof(vma) || 2485 is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) { 2486 continue; 2487 } 2488 2489 /* 2490 * Shared library pages mapped by multiple processes are not 2491 * migrated as it is expected they are cache replicated. Avoid 2492 * hinting faults in read-only file-backed mappings or the vdso 2493 * as migrating the pages will be of marginal benefit. 2494 */ 2495 if (!vma->vm_mm || 2496 (vma->vm_file && (vma->vm_flags & (VM_READ|VM_WRITE)) == (VM_READ))) 2497 continue; 2498 2499 /* 2500 * Skip inaccessible VMAs to avoid any confusion between 2501 * PROT_NONE and NUMA hinting ptes 2502 */ 2503 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 2504 continue; 2505 2506 do { 2507 start = max(start, vma->vm_start); 2508 end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE); 2509 end = min(end, vma->vm_end); 2510 nr_pte_updates = change_prot_numa(vma, start, end); 2511 2512 /* 2513 * Try to scan sysctl_numa_balancing_size worth of 2514 * hpages that have at least one present PTE that 2515 * is not already pte-numa. If the VMA contains 2516 * areas that are unused or already full of prot_numa 2517 * PTEs, scan up to virtpages, to skip through those 2518 * areas faster. 2519 */ 2520 if (nr_pte_updates) 2521 pages -= (end - start) >> PAGE_SHIFT; 2522 virtpages -= (end - start) >> PAGE_SHIFT; 2523 2524 start = end; 2525 if (pages <= 0 || virtpages <= 0) 2526 goto out; 2527 2528 cond_resched(); 2529 } while (end != vma->vm_end); 2530 } 2531 2532 out: 2533 /* 2534 * It is possible to reach the end of the VMA list but the last few 2535 * VMAs are not guaranteed to the vma_migratable. If they are not, we 2536 * would find the !migratable VMA on the next scan but not reset the 2537 * scanner to the start so check it now. 2538 */ 2539 if (vma) 2540 mm->numa_scan_offset = start; 2541 else 2542 reset_ptenuma_scan(p); 2543 up_read(&mm->mmap_sem); 2544 2545 /* 2546 * Make sure tasks use at least 32x as much time to run other code 2547 * than they used here, to limit NUMA PTE scanning overhead to 3% max. 2548 * Usually update_task_scan_period slows down scanning enough; on an 2549 * overloaded system we need to limit overhead on a per task basis. 2550 */ 2551 if (unlikely(p->se.sum_exec_runtime != runtime)) { 2552 u64 diff = p->se.sum_exec_runtime - runtime; 2553 p->node_stamp += 32 * diff; 2554 } 2555 } 2556 2557 /* 2558 * Drive the periodic memory faults.. 2559 */ 2560 void task_tick_numa(struct rq *rq, struct task_struct *curr) 2561 { 2562 struct callback_head *work = &curr->numa_work; 2563 u64 period, now; 2564 2565 /* 2566 * We don't care about NUMA placement if we don't have memory. 2567 */ 2568 if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work) 2569 return; 2570 2571 /* 2572 * Using runtime rather than walltime has the dual advantage that 2573 * we (mostly) drive the selection from busy threads and that the 2574 * task needs to have done some actual work before we bother with 2575 * NUMA placement. 2576 */ 2577 now = curr->se.sum_exec_runtime; 2578 period = (u64)curr->numa_scan_period * NSEC_PER_MSEC; 2579 2580 if (now > curr->node_stamp + period) { 2581 if (!curr->node_stamp) 2582 curr->numa_scan_period = task_scan_min(curr); 2583 curr->node_stamp += period; 2584 2585 if (!time_before(jiffies, curr->mm->numa_next_scan)) { 2586 init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */ 2587 task_work_add(curr, work, true); 2588 } 2589 } 2590 } 2591 #else 2592 static void task_tick_numa(struct rq *rq, struct task_struct *curr) 2593 { 2594 } 2595 2596 static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p) 2597 { 2598 } 2599 2600 static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p) 2601 { 2602 } 2603 #endif /* CONFIG_NUMA_BALANCING */ 2604 2605 static void 2606 account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2607 { 2608 update_load_add(&cfs_rq->load, se->load.weight); 2609 if (!parent_entity(se)) 2610 update_load_add(&rq_of(cfs_rq)->load, se->load.weight); 2611 #ifdef CONFIG_SMP 2612 if (entity_is_task(se)) { 2613 struct rq *rq = rq_of(cfs_rq); 2614 2615 account_numa_enqueue(rq, task_of(se)); 2616 list_add(&se->group_node, &rq->cfs_tasks); 2617 } 2618 #endif 2619 cfs_rq->nr_running++; 2620 } 2621 2622 static void 2623 account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se) 2624 { 2625 update_load_sub(&cfs_rq->load, se->load.weight); 2626 if (!parent_entity(se)) 2627 update_load_sub(&rq_of(cfs_rq)->load, se->load.weight); 2628 #ifdef CONFIG_SMP 2629 if (entity_is_task(se)) { 2630 account_numa_dequeue(rq_of(cfs_rq), task_of(se)); 2631 list_del_init(&se->group_node); 2632 } 2633 #endif 2634 cfs_rq->nr_running--; 2635 } 2636 2637 #ifdef CONFIG_FAIR_GROUP_SCHED 2638 # ifdef CONFIG_SMP 2639 static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2640 { 2641 long tg_weight, load, shares; 2642 2643 /* 2644 * This really should be: cfs_rq->avg.load_avg, but instead we use 2645 * cfs_rq->load.weight, which is its upper bound. This helps ramp up 2646 * the shares for small weight interactive tasks. 2647 */ 2648 load = scale_load_down(cfs_rq->load.weight); 2649 2650 tg_weight = atomic_long_read(&tg->load_avg); 2651 2652 /* Ensure tg_weight >= load */ 2653 tg_weight -= cfs_rq->tg_load_avg_contrib; 2654 tg_weight += load; 2655 2656 shares = (tg->shares * load); 2657 if (tg_weight) 2658 shares /= tg_weight; 2659 2660 if (shares < MIN_SHARES) 2661 shares = MIN_SHARES; 2662 if (shares > tg->shares) 2663 shares = tg->shares; 2664 2665 return shares; 2666 } 2667 # else /* CONFIG_SMP */ 2668 static inline long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 2669 { 2670 return tg->shares; 2671 } 2672 # endif /* CONFIG_SMP */ 2673 2674 static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, 2675 unsigned long weight) 2676 { 2677 if (se->on_rq) { 2678 /* commit outstanding execution time */ 2679 if (cfs_rq->curr == se) 2680 update_curr(cfs_rq); 2681 account_entity_dequeue(cfs_rq, se); 2682 } 2683 2684 update_load_set(&se->load, weight); 2685 2686 if (se->on_rq) 2687 account_entity_enqueue(cfs_rq, se); 2688 } 2689 2690 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq); 2691 2692 static void update_cfs_shares(struct cfs_rq *cfs_rq) 2693 { 2694 struct task_group *tg; 2695 struct sched_entity *se; 2696 long shares; 2697 2698 tg = cfs_rq->tg; 2699 se = tg->se[cpu_of(rq_of(cfs_rq))]; 2700 if (!se || throttled_hierarchy(cfs_rq)) 2701 return; 2702 #ifndef CONFIG_SMP 2703 if (likely(se->load.weight == tg->shares)) 2704 return; 2705 #endif 2706 shares = calc_cfs_shares(cfs_rq, tg); 2707 2708 reweight_entity(cfs_rq_of(se), se, shares); 2709 } 2710 #else /* CONFIG_FAIR_GROUP_SCHED */ 2711 static inline void update_cfs_shares(struct cfs_rq *cfs_rq) 2712 { 2713 } 2714 #endif /* CONFIG_FAIR_GROUP_SCHED */ 2715 2716 #ifdef CONFIG_SMP 2717 /* Precomputed fixed inverse multiplies for multiplication by y^n */ 2718 static const u32 runnable_avg_yN_inv[] = { 2719 0xffffffff, 0xfa83b2da, 0xf5257d14, 0xefe4b99a, 0xeac0c6e6, 0xe5b906e6, 2720 0xe0ccdeeb, 0xdbfbb796, 0xd744fcc9, 0xd2a81d91, 0xce248c14, 0xc9b9bd85, 2721 0xc5672a10, 0xc12c4cc9, 0xbd08a39e, 0xb8fbaf46, 0xb504f333, 0xb123f581, 2722 0xad583ee9, 0xa9a15ab4, 0xa5fed6a9, 0xa2704302, 0x9ef5325f, 0x9b8d39b9, 2723 0x9837f050, 0x94f4efa8, 0x91c3d373, 0x8ea4398a, 0x8b95c1e3, 0x88980e80, 2724 0x85aac367, 0x82cd8698, 2725 }; 2726 2727 /* 2728 * Precomputed \Sum y^k { 1<=k<=n }. These are floor(true_value) to prevent 2729 * over-estimates when re-combining. 2730 */ 2731 static const u32 runnable_avg_yN_sum[] = { 2732 0, 1002, 1982, 2941, 3880, 4798, 5697, 6576, 7437, 8279, 9103, 2733 9909,10698,11470,12226,12966,13690,14398,15091,15769,16433,17082, 2734 17718,18340,18949,19545,20128,20698,21256,21802,22336,22859,23371, 2735 }; 2736 2737 /* 2738 * Precomputed \Sum y^k { 1<=k<=n, where n%32=0). Values are rolled down to 2739 * lower integers. See Documentation/scheduler/sched-avg.txt how these 2740 * were generated: 2741 */ 2742 static const u32 __accumulated_sum_N32[] = { 2743 0, 23371, 35056, 40899, 43820, 45281, 2744 46011, 46376, 46559, 46650, 46696, 46719, 2745 }; 2746 2747 /* 2748 * Approximate: 2749 * val * y^n, where y^32 ~= 0.5 (~1 scheduling period) 2750 */ 2751 static __always_inline u64 decay_load(u64 val, u64 n) 2752 { 2753 unsigned int local_n; 2754 2755 if (!n) 2756 return val; 2757 else if (unlikely(n > LOAD_AVG_PERIOD * 63)) 2758 return 0; 2759 2760 /* after bounds checking we can collapse to 32-bit */ 2761 local_n = n; 2762 2763 /* 2764 * As y^PERIOD = 1/2, we can combine 2765 * y^n = 1/2^(n/PERIOD) * y^(n%PERIOD) 2766 * With a look-up table which covers y^n (n<PERIOD) 2767 * 2768 * To achieve constant time decay_load. 2769 */ 2770 if (unlikely(local_n >= LOAD_AVG_PERIOD)) { 2771 val >>= local_n / LOAD_AVG_PERIOD; 2772 local_n %= LOAD_AVG_PERIOD; 2773 } 2774 2775 val = mul_u64_u32_shr(val, runnable_avg_yN_inv[local_n], 32); 2776 return val; 2777 } 2778 2779 /* 2780 * For updates fully spanning n periods, the contribution to runnable 2781 * average will be: \Sum 1024*y^n 2782 * 2783 * We can compute this reasonably efficiently by combining: 2784 * y^PERIOD = 1/2 with precomputed \Sum 1024*y^n {for n <PERIOD} 2785 */ 2786 static u32 __compute_runnable_contrib(u64 n) 2787 { 2788 u32 contrib = 0; 2789 2790 if (likely(n <= LOAD_AVG_PERIOD)) 2791 return runnable_avg_yN_sum[n]; 2792 else if (unlikely(n >= LOAD_AVG_MAX_N)) 2793 return LOAD_AVG_MAX; 2794 2795 /* Since n < LOAD_AVG_MAX_N, n/LOAD_AVG_PERIOD < 11 */ 2796 contrib = __accumulated_sum_N32[n/LOAD_AVG_PERIOD]; 2797 n %= LOAD_AVG_PERIOD; 2798 contrib = decay_load(contrib, n); 2799 return contrib + runnable_avg_yN_sum[n]; 2800 } 2801 2802 #define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT) 2803 2804 /* 2805 * We can represent the historical contribution to runnable average as the 2806 * coefficients of a geometric series. To do this we sub-divide our runnable 2807 * history into segments of approximately 1ms (1024us); label the segment that 2808 * occurred N-ms ago p_N, with p_0 corresponding to the current period, e.g. 2809 * 2810 * [<- 1024us ->|<- 1024us ->|<- 1024us ->| ... 2811 * p0 p1 p2 2812 * (now) (~1ms ago) (~2ms ago) 2813 * 2814 * Let u_i denote the fraction of p_i that the entity was runnable. 2815 * 2816 * We then designate the fractions u_i as our co-efficients, yielding the 2817 * following representation of historical load: 2818 * u_0 + u_1*y + u_2*y^2 + u_3*y^3 + ... 2819 * 2820 * We choose y based on the with of a reasonably scheduling period, fixing: 2821 * y^32 = 0.5 2822 * 2823 * This means that the contribution to load ~32ms ago (u_32) will be weighted 2824 * approximately half as much as the contribution to load within the last ms 2825 * (u_0). 2826 * 2827 * When a period "rolls over" and we have new u_0`, multiplying the previous 2828 * sum again by y is sufficient to update: 2829 * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) 2830 * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] 2831 */ 2832 static __always_inline int 2833 __update_load_avg(u64 now, int cpu, struct sched_avg *sa, 2834 unsigned long weight, int running, struct cfs_rq *cfs_rq) 2835 { 2836 u64 delta, scaled_delta, periods; 2837 u32 contrib; 2838 unsigned int delta_w, scaled_delta_w, decayed = 0; 2839 unsigned long scale_freq, scale_cpu; 2840 2841 delta = now - sa->last_update_time; 2842 /* 2843 * This should only happen when time goes backwards, which it 2844 * unfortunately does during sched clock init when we swap over to TSC. 2845 */ 2846 if ((s64)delta < 0) { 2847 sa->last_update_time = now; 2848 return 0; 2849 } 2850 2851 /* 2852 * Use 1024ns as the unit of measurement since it's a reasonable 2853 * approximation of 1us and fast to compute. 2854 */ 2855 delta >>= 10; 2856 if (!delta) 2857 return 0; 2858 sa->last_update_time = now; 2859 2860 scale_freq = arch_scale_freq_capacity(NULL, cpu); 2861 scale_cpu = arch_scale_cpu_capacity(NULL, cpu); 2862 2863 /* delta_w is the amount already accumulated against our next period */ 2864 delta_w = sa->period_contrib; 2865 if (delta + delta_w >= 1024) { 2866 decayed = 1; 2867 2868 /* how much left for next period will start over, we don't know yet */ 2869 sa->period_contrib = 0; 2870 2871 /* 2872 * Now that we know we're crossing a period boundary, figure 2873 * out how much from delta we need to complete the current 2874 * period and accrue it. 2875 */ 2876 delta_w = 1024 - delta_w; 2877 scaled_delta_w = cap_scale(delta_w, scale_freq); 2878 if (weight) { 2879 sa->load_sum += weight * scaled_delta_w; 2880 if (cfs_rq) { 2881 cfs_rq->runnable_load_sum += 2882 weight * scaled_delta_w; 2883 } 2884 } 2885 if (running) 2886 sa->util_sum += scaled_delta_w * scale_cpu; 2887 2888 delta -= delta_w; 2889 2890 /* Figure out how many additional periods this update spans */ 2891 periods = delta / 1024; 2892 delta %= 1024; 2893 2894 sa->load_sum = decay_load(sa->load_sum, periods + 1); 2895 if (cfs_rq) { 2896 cfs_rq->runnable_load_sum = 2897 decay_load(cfs_rq->runnable_load_sum, periods + 1); 2898 } 2899 sa->util_sum = decay_load((u64)(sa->util_sum), periods + 1); 2900 2901 /* Efficiently calculate \sum (1..n_period) 1024*y^i */ 2902 contrib = __compute_runnable_contrib(periods); 2903 contrib = cap_scale(contrib, scale_freq); 2904 if (weight) { 2905 sa->load_sum += weight * contrib; 2906 if (cfs_rq) 2907 cfs_rq->runnable_load_sum += weight * contrib; 2908 } 2909 if (running) 2910 sa->util_sum += contrib * scale_cpu; 2911 } 2912 2913 /* Remainder of delta accrued against u_0` */ 2914 scaled_delta = cap_scale(delta, scale_freq); 2915 if (weight) { 2916 sa->load_sum += weight * scaled_delta; 2917 if (cfs_rq) 2918 cfs_rq->runnable_load_sum += weight * scaled_delta; 2919 } 2920 if (running) 2921 sa->util_sum += scaled_delta * scale_cpu; 2922 2923 sa->period_contrib += delta; 2924 2925 if (decayed) { 2926 sa->load_avg = div_u64(sa->load_sum, LOAD_AVG_MAX); 2927 if (cfs_rq) { 2928 cfs_rq->runnable_load_avg = 2929 div_u64(cfs_rq->runnable_load_sum, LOAD_AVG_MAX); 2930 } 2931 sa->util_avg = sa->util_sum / LOAD_AVG_MAX; 2932 } 2933 2934 return decayed; 2935 } 2936 2937 /* 2938 * Signed add and clamp on underflow. 2939 * 2940 * Explicitly do a load-store to ensure the intermediate value never hits 2941 * memory. This allows lockless observations without ever seeing the negative 2942 * values. 2943 */ 2944 #define add_positive(_ptr, _val) do { \ 2945 typeof(_ptr) ptr = (_ptr); \ 2946 typeof(_val) val = (_val); \ 2947 typeof(*ptr) res, var = READ_ONCE(*ptr); \ 2948 \ 2949 res = var + val; \ 2950 \ 2951 if (val < 0 && res > var) \ 2952 res = 0; \ 2953 \ 2954 WRITE_ONCE(*ptr, res); \ 2955 } while (0) 2956 2957 #ifdef CONFIG_FAIR_GROUP_SCHED 2958 /** 2959 * update_tg_load_avg - update the tg's load avg 2960 * @cfs_rq: the cfs_rq whose avg changed 2961 * @force: update regardless of how small the difference 2962 * 2963 * This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load. 2964 * However, because tg->load_avg is a global value there are performance 2965 * considerations. 2966 * 2967 * In order to avoid having to look at the other cfs_rq's, we use a 2968 * differential update where we store the last value we propagated. This in 2969 * turn allows skipping updates if the differential is 'small'. 2970 * 2971 * Updating tg's load_avg is necessary before update_cfs_share() (which is 2972 * done) and effective_load() (which is not done because it is too costly). 2973 */ 2974 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) 2975 { 2976 long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib; 2977 2978 /* 2979 * No need to update load_avg for root_task_group as it is not used. 2980 */ 2981 if (cfs_rq->tg == &root_task_group) 2982 return; 2983 2984 if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) { 2985 atomic_long_add(delta, &cfs_rq->tg->load_avg); 2986 cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg; 2987 } 2988 } 2989 2990 /* 2991 * Called within set_task_rq() right before setting a task's cpu. The 2992 * caller only guarantees p->pi_lock is held; no other assumptions, 2993 * including the state of rq->lock, should be made. 2994 */ 2995 void set_task_rq_fair(struct sched_entity *se, 2996 struct cfs_rq *prev, struct cfs_rq *next) 2997 { 2998 if (!sched_feat(ATTACH_AGE_LOAD)) 2999 return; 3000 3001 /* 3002 * We are supposed to update the task to "current" time, then its up to 3003 * date and ready to go to new CPU/cfs_rq. But we have difficulty in 3004 * getting what current time is, so simply throw away the out-of-date 3005 * time. This will result in the wakee task is less decayed, but giving 3006 * the wakee more load sounds not bad. 3007 */ 3008 if (se->avg.last_update_time && prev) { 3009 u64 p_last_update_time; 3010 u64 n_last_update_time; 3011 3012 #ifndef CONFIG_64BIT 3013 u64 p_last_update_time_copy; 3014 u64 n_last_update_time_copy; 3015 3016 do { 3017 p_last_update_time_copy = prev->load_last_update_time_copy; 3018 n_last_update_time_copy = next->load_last_update_time_copy; 3019 3020 smp_rmb(); 3021 3022 p_last_update_time = prev->avg.last_update_time; 3023 n_last_update_time = next->avg.last_update_time; 3024 3025 } while (p_last_update_time != p_last_update_time_copy || 3026 n_last_update_time != n_last_update_time_copy); 3027 #else 3028 p_last_update_time = prev->avg.last_update_time; 3029 n_last_update_time = next->avg.last_update_time; 3030 #endif 3031 __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)), 3032 &se->avg, 0, 0, NULL); 3033 se->avg.last_update_time = n_last_update_time; 3034 } 3035 } 3036 3037 /* Take into account change of utilization of a child task group */ 3038 static inline void 3039 update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se) 3040 { 3041 struct cfs_rq *gcfs_rq = group_cfs_rq(se); 3042 long delta = gcfs_rq->avg.util_avg - se->avg.util_avg; 3043 3044 /* Nothing to update */ 3045 if (!delta) 3046 return; 3047 3048 /* Set new sched_entity's utilization */ 3049 se->avg.util_avg = gcfs_rq->avg.util_avg; 3050 se->avg.util_sum = se->avg.util_avg * LOAD_AVG_MAX; 3051 3052 /* Update parent cfs_rq utilization */ 3053 add_positive(&cfs_rq->avg.util_avg, delta); 3054 cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * LOAD_AVG_MAX; 3055 } 3056 3057 /* Take into account change of load of a child task group */ 3058 static inline void 3059 update_tg_cfs_load(struct cfs_rq *cfs_rq, struct sched_entity *se) 3060 { 3061 struct cfs_rq *gcfs_rq = group_cfs_rq(se); 3062 long delta, load = gcfs_rq->avg.load_avg; 3063 3064 /* 3065 * If the load of group cfs_rq is null, the load of the 3066 * sched_entity will also be null so we can skip the formula 3067 */ 3068 if (load) { 3069 long tg_load; 3070 3071 /* Get tg's load and ensure tg_load > 0 */ 3072 tg_load = atomic_long_read(&gcfs_rq->tg->load_avg) + 1; 3073 3074 /* Ensure tg_load >= load and updated with current load*/ 3075 tg_load -= gcfs_rq->tg_load_avg_contrib; 3076 tg_load += load; 3077 3078 /* 3079 * We need to compute a correction term in the case that the 3080 * task group is consuming more CPU than a task of equal 3081 * weight. A task with a weight equals to tg->shares will have 3082 * a load less or equal to scale_load_down(tg->shares). 3083 * Similarly, the sched_entities that represent the task group 3084 * at parent level, can't have a load higher than 3085 * scale_load_down(tg->shares). And the Sum of sched_entities' 3086 * load must be <= scale_load_down(tg->shares). 3087 */ 3088 if (tg_load > scale_load_down(gcfs_rq->tg->shares)) { 3089 /* scale gcfs_rq's load into tg's shares*/ 3090 load *= scale_load_down(gcfs_rq->tg->shares); 3091 load /= tg_load; 3092 } 3093 } 3094 3095 delta = load - se->avg.load_avg; 3096 3097 /* Nothing to update */ 3098 if (!delta) 3099 return; 3100 3101 /* Set new sched_entity's load */ 3102 se->avg.load_avg = load; 3103 se->avg.load_sum = se->avg.load_avg * LOAD_AVG_MAX; 3104 3105 /* Update parent cfs_rq load */ 3106 add_positive(&cfs_rq->avg.load_avg, delta); 3107 cfs_rq->avg.load_sum = cfs_rq->avg.load_avg * LOAD_AVG_MAX; 3108 3109 /* 3110 * If the sched_entity is already enqueued, we also have to update the 3111 * runnable load avg. 3112 */ 3113 if (se->on_rq) { 3114 /* Update parent cfs_rq runnable_load_avg */ 3115 add_positive(&cfs_rq->runnable_load_avg, delta); 3116 cfs_rq->runnable_load_sum = cfs_rq->runnable_load_avg * LOAD_AVG_MAX; 3117 } 3118 } 3119 3120 static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq) 3121 { 3122 cfs_rq->propagate_avg = 1; 3123 } 3124 3125 static inline int test_and_clear_tg_cfs_propagate(struct sched_entity *se) 3126 { 3127 struct cfs_rq *cfs_rq = group_cfs_rq(se); 3128 3129 if (!cfs_rq->propagate_avg) 3130 return 0; 3131 3132 cfs_rq->propagate_avg = 0; 3133 return 1; 3134 } 3135 3136 /* Update task and its cfs_rq load average */ 3137 static inline int propagate_entity_load_avg(struct sched_entity *se) 3138 { 3139 struct cfs_rq *cfs_rq; 3140 3141 if (entity_is_task(se)) 3142 return 0; 3143 3144 if (!test_and_clear_tg_cfs_propagate(se)) 3145 return 0; 3146 3147 cfs_rq = cfs_rq_of(se); 3148 3149 set_tg_cfs_propagate(cfs_rq); 3150 3151 update_tg_cfs_util(cfs_rq, se); 3152 update_tg_cfs_load(cfs_rq, se); 3153 3154 return 1; 3155 } 3156 3157 #else /* CONFIG_FAIR_GROUP_SCHED */ 3158 3159 static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {} 3160 3161 static inline int propagate_entity_load_avg(struct sched_entity *se) 3162 { 3163 return 0; 3164 } 3165 3166 static inline void set_tg_cfs_propagate(struct cfs_rq *cfs_rq) {} 3167 3168 #endif /* CONFIG_FAIR_GROUP_SCHED */ 3169 3170 static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq) 3171 { 3172 if (&this_rq()->cfs == cfs_rq) { 3173 /* 3174 * There are a few boundary cases this might miss but it should 3175 * get called often enough that that should (hopefully) not be 3176 * a real problem -- added to that it only calls on the local 3177 * CPU, so if we enqueue remotely we'll miss an update, but 3178 * the next tick/schedule should update. 3179 * 3180 * It will not get called when we go idle, because the idle 3181 * thread is a different class (!fair), nor will the utilization 3182 * number include things like RT tasks. 3183 * 3184 * As is, the util number is not freq-invariant (we'd have to 3185 * implement arch_scale_freq_capacity() for that). 3186 * 3187 * See cpu_util(). 3188 */ 3189 cpufreq_update_util(rq_of(cfs_rq), 0); 3190 } 3191 } 3192 3193 /* 3194 * Unsigned subtract and clamp on underflow. 3195 * 3196 * Explicitly do a load-store to ensure the intermediate value never hits 3197 * memory. This allows lockless observations without ever seeing the negative 3198 * values. 3199 */ 3200 #define sub_positive(_ptr, _val) do { \ 3201 typeof(_ptr) ptr = (_ptr); \ 3202 typeof(*ptr) val = (_val); \ 3203 typeof(*ptr) res, var = READ_ONCE(*ptr); \ 3204 res = var - val; \ 3205 if (res > var) \ 3206 res = 0; \ 3207 WRITE_ONCE(*ptr, res); \ 3208 } while (0) 3209 3210 /** 3211 * update_cfs_rq_load_avg - update the cfs_rq's load/util averages 3212 * @now: current time, as per cfs_rq_clock_task() 3213 * @cfs_rq: cfs_rq to update 3214 * @update_freq: should we call cfs_rq_util_change() or will the call do so 3215 * 3216 * The cfs_rq avg is the direct sum of all its entities (blocked and runnable) 3217 * avg. The immediate corollary is that all (fair) tasks must be attached, see 3218 * post_init_entity_util_avg(). 3219 * 3220 * cfs_rq->avg is used for task_h_load() and update_cfs_share() for example. 3221 * 3222 * Returns true if the load decayed or we removed load. 3223 * 3224 * Since both these conditions indicate a changed cfs_rq->avg.load we should 3225 * call update_tg_load_avg() when this function returns true. 3226 */ 3227 static inline int 3228 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) 3229 { 3230 struct sched_avg *sa = &cfs_rq->avg; 3231 int decayed, removed_load = 0, removed_util = 0; 3232 3233 if (atomic_long_read(&cfs_rq->removed_load_avg)) { 3234 s64 r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0); 3235 sub_positive(&sa->load_avg, r); 3236 sub_positive(&sa->load_sum, r * LOAD_AVG_MAX); 3237 removed_load = 1; 3238 set_tg_cfs_propagate(cfs_rq); 3239 } 3240 3241 if (atomic_long_read(&cfs_rq->removed_util_avg)) { 3242 long r = atomic_long_xchg(&cfs_rq->removed_util_avg, 0); 3243 sub_positive(&sa->util_avg, r); 3244 sub_positive(&sa->util_sum, r * LOAD_AVG_MAX); 3245 removed_util = 1; 3246 set_tg_cfs_propagate(cfs_rq); 3247 } 3248 3249 decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa, 3250 scale_load_down(cfs_rq->load.weight), cfs_rq->curr != NULL, cfs_rq); 3251 3252 #ifndef CONFIG_64BIT 3253 smp_wmb(); 3254 cfs_rq->load_last_update_time_copy = sa->last_update_time; 3255 #endif 3256 3257 if (update_freq && (decayed || removed_util)) 3258 cfs_rq_util_change(cfs_rq); 3259 3260 return decayed || removed_load; 3261 } 3262 3263 /* 3264 * Optional action to be done while updating the load average 3265 */ 3266 #define UPDATE_TG 0x1 3267 #define SKIP_AGE_LOAD 0x2 3268 3269 /* Update task and its cfs_rq load average */ 3270 static inline void update_load_avg(struct sched_entity *se, int flags) 3271 { 3272 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3273 u64 now = cfs_rq_clock_task(cfs_rq); 3274 struct rq *rq = rq_of(cfs_rq); 3275 int cpu = cpu_of(rq); 3276 int decayed; 3277 3278 /* 3279 * Track task load average for carrying it to new CPU after migrated, and 3280 * track group sched_entity load average for task_h_load calc in migration 3281 */ 3282 if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD)) { 3283 __update_load_avg(now, cpu, &se->avg, 3284 se->on_rq * scale_load_down(se->load.weight), 3285 cfs_rq->curr == se, NULL); 3286 } 3287 3288 decayed = update_cfs_rq_load_avg(now, cfs_rq, true); 3289 decayed |= propagate_entity_load_avg(se); 3290 3291 if (decayed && (flags & UPDATE_TG)) 3292 update_tg_load_avg(cfs_rq, 0); 3293 } 3294 3295 /** 3296 * attach_entity_load_avg - attach this entity to its cfs_rq load avg 3297 * @cfs_rq: cfs_rq to attach to 3298 * @se: sched_entity to attach 3299 * 3300 * Must call update_cfs_rq_load_avg() before this, since we rely on 3301 * cfs_rq->avg.last_update_time being current. 3302 */ 3303 static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) 3304 { 3305 se->avg.last_update_time = cfs_rq->avg.last_update_time; 3306 cfs_rq->avg.load_avg += se->avg.load_avg; 3307 cfs_rq->avg.load_sum += se->avg.load_sum; 3308 cfs_rq->avg.util_avg += se->avg.util_avg; 3309 cfs_rq->avg.util_sum += se->avg.util_sum; 3310 set_tg_cfs_propagate(cfs_rq); 3311 3312 cfs_rq_util_change(cfs_rq); 3313 } 3314 3315 /** 3316 * detach_entity_load_avg - detach this entity from its cfs_rq load avg 3317 * @cfs_rq: cfs_rq to detach from 3318 * @se: sched_entity to detach 3319 * 3320 * Must call update_cfs_rq_load_avg() before this, since we rely on 3321 * cfs_rq->avg.last_update_time being current. 3322 */ 3323 static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) 3324 { 3325 3326 sub_positive(&cfs_rq->avg.load_avg, se->avg.load_avg); 3327 sub_positive(&cfs_rq->avg.load_sum, se->avg.load_sum); 3328 sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg); 3329 sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum); 3330 set_tg_cfs_propagate(cfs_rq); 3331 3332 cfs_rq_util_change(cfs_rq); 3333 } 3334 3335 /* Add the load generated by se into cfs_rq's load average */ 3336 static inline void 3337 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) 3338 { 3339 struct sched_avg *sa = &se->avg; 3340 3341 cfs_rq->runnable_load_avg += sa->load_avg; 3342 cfs_rq->runnable_load_sum += sa->load_sum; 3343 3344 if (!sa->last_update_time) { 3345 attach_entity_load_avg(cfs_rq, se); 3346 update_tg_load_avg(cfs_rq, 0); 3347 } 3348 } 3349 3350 /* Remove the runnable load generated by se from cfs_rq's runnable load average */ 3351 static inline void 3352 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) 3353 { 3354 cfs_rq->runnable_load_avg = 3355 max_t(long, cfs_rq->runnable_load_avg - se->avg.load_avg, 0); 3356 cfs_rq->runnable_load_sum = 3357 max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0); 3358 } 3359 3360 #ifndef CONFIG_64BIT 3361 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) 3362 { 3363 u64 last_update_time_copy; 3364 u64 last_update_time; 3365 3366 do { 3367 last_update_time_copy = cfs_rq->load_last_update_time_copy; 3368 smp_rmb(); 3369 last_update_time = cfs_rq->avg.last_update_time; 3370 } while (last_update_time != last_update_time_copy); 3371 3372 return last_update_time; 3373 } 3374 #else 3375 static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq) 3376 { 3377 return cfs_rq->avg.last_update_time; 3378 } 3379 #endif 3380 3381 /* 3382 * Synchronize entity load avg of dequeued entity without locking 3383 * the previous rq. 3384 */ 3385 void sync_entity_load_avg(struct sched_entity *se) 3386 { 3387 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3388 u64 last_update_time; 3389 3390 last_update_time = cfs_rq_last_update_time(cfs_rq); 3391 __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL); 3392 } 3393 3394 /* 3395 * Task first catches up with cfs_rq, and then subtract 3396 * itself from the cfs_rq (task must be off the queue now). 3397 */ 3398 void remove_entity_load_avg(struct sched_entity *se) 3399 { 3400 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3401 3402 /* 3403 * tasks cannot exit without having gone through wake_up_new_task() -> 3404 * post_init_entity_util_avg() which will have added things to the 3405 * cfs_rq, so we can remove unconditionally. 3406 * 3407 * Similarly for groups, they will have passed through 3408 * post_init_entity_util_avg() before unregister_sched_fair_group() 3409 * calls this. 3410 */ 3411 3412 sync_entity_load_avg(se); 3413 atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg); 3414 atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg); 3415 } 3416 3417 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq) 3418 { 3419 return cfs_rq->runnable_load_avg; 3420 } 3421 3422 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq) 3423 { 3424 return cfs_rq->avg.load_avg; 3425 } 3426 3427 static int idle_balance(struct rq *this_rq); 3428 3429 #else /* CONFIG_SMP */ 3430 3431 static inline int 3432 update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) 3433 { 3434 return 0; 3435 } 3436 3437 #define UPDATE_TG 0x0 3438 #define SKIP_AGE_LOAD 0x0 3439 3440 static inline void update_load_avg(struct sched_entity *se, int not_used1) 3441 { 3442 cpufreq_update_util(rq_of(cfs_rq_of(se)), 0); 3443 } 3444 3445 static inline void 3446 enqueue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} 3447 static inline void 3448 dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} 3449 static inline void remove_entity_load_avg(struct sched_entity *se) {} 3450 3451 static inline void 3452 attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} 3453 static inline void 3454 detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {} 3455 3456 static inline int idle_balance(struct rq *rq) 3457 { 3458 return 0; 3459 } 3460 3461 #endif /* CONFIG_SMP */ 3462 3463 static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se) 3464 { 3465 #ifdef CONFIG_SCHED_DEBUG 3466 s64 d = se->vruntime - cfs_rq->min_vruntime; 3467 3468 if (d < 0) 3469 d = -d; 3470 3471 if (d > 3*sysctl_sched_latency) 3472 schedstat_inc(cfs_rq->nr_spread_over); 3473 #endif 3474 } 3475 3476 static void 3477 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial) 3478 { 3479 u64 vruntime = cfs_rq->min_vruntime; 3480 3481 /* 3482 * The 'current' period is already promised to the current tasks, 3483 * however the extra weight of the new task will slow them down a 3484 * little, place the new task so that it fits in the slot that 3485 * stays open at the end. 3486 */ 3487 if (initial && sched_feat(START_DEBIT)) 3488 vruntime += sched_vslice(cfs_rq, se); 3489 3490 /* sleeps up to a single latency don't count. */ 3491 if (!initial) { 3492 unsigned long thresh = sysctl_sched_latency; 3493 3494 /* 3495 * Halve their sleep time's effect, to allow 3496 * for a gentler effect of sleepers: 3497 */ 3498 if (sched_feat(GENTLE_FAIR_SLEEPERS)) 3499 thresh >>= 1; 3500 3501 vruntime -= thresh; 3502 } 3503 3504 /* ensure we never gain time by being placed backwards. */ 3505 se->vruntime = max_vruntime(se->vruntime, vruntime); 3506 } 3507 3508 static void check_enqueue_throttle(struct cfs_rq *cfs_rq); 3509 3510 static inline void check_schedstat_required(void) 3511 { 3512 #ifdef CONFIG_SCHEDSTATS 3513 if (schedstat_enabled()) 3514 return; 3515 3516 /* Force schedstat enabled if a dependent tracepoint is active */ 3517 if (trace_sched_stat_wait_enabled() || 3518 trace_sched_stat_sleep_enabled() || 3519 trace_sched_stat_iowait_enabled() || 3520 trace_sched_stat_blocked_enabled() || 3521 trace_sched_stat_runtime_enabled()) { 3522 printk_deferred_once("Scheduler tracepoints stat_sleep, stat_iowait, " 3523 "stat_blocked and stat_runtime require the " 3524 "kernel parameter schedstats=enabled or " 3525 "kernel.sched_schedstats=1\n"); 3526 } 3527 #endif 3528 } 3529 3530 3531 /* 3532 * MIGRATION 3533 * 3534 * dequeue 3535 * update_curr() 3536 * update_min_vruntime() 3537 * vruntime -= min_vruntime 3538 * 3539 * enqueue 3540 * update_curr() 3541 * update_min_vruntime() 3542 * vruntime += min_vruntime 3543 * 3544 * this way the vruntime transition between RQs is done when both 3545 * min_vruntime are up-to-date. 3546 * 3547 * WAKEUP (remote) 3548 * 3549 * ->migrate_task_rq_fair() (p->state == TASK_WAKING) 3550 * vruntime -= min_vruntime 3551 * 3552 * enqueue 3553 * update_curr() 3554 * update_min_vruntime() 3555 * vruntime += min_vruntime 3556 * 3557 * this way we don't have the most up-to-date min_vruntime on the originating 3558 * CPU and an up-to-date min_vruntime on the destination CPU. 3559 */ 3560 3561 static void 3562 enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 3563 { 3564 bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_MIGRATED); 3565 bool curr = cfs_rq->curr == se; 3566 3567 /* 3568 * If we're the current task, we must renormalise before calling 3569 * update_curr(). 3570 */ 3571 if (renorm && curr) 3572 se->vruntime += cfs_rq->min_vruntime; 3573 3574 update_curr(cfs_rq); 3575 3576 /* 3577 * Otherwise, renormalise after, such that we're placed at the current 3578 * moment in time, instead of some random moment in the past. Being 3579 * placed in the past could significantly boost this task to the 3580 * fairness detriment of existing tasks. 3581 */ 3582 if (renorm && !curr) 3583 se->vruntime += cfs_rq->min_vruntime; 3584 3585 update_load_avg(se, UPDATE_TG); 3586 enqueue_entity_load_avg(cfs_rq, se); 3587 account_entity_enqueue(cfs_rq, se); 3588 update_cfs_shares(cfs_rq); 3589 3590 if (flags & ENQUEUE_WAKEUP) 3591 place_entity(cfs_rq, se, 0); 3592 3593 check_schedstat_required(); 3594 update_stats_enqueue(cfs_rq, se, flags); 3595 check_spread(cfs_rq, se); 3596 if (!curr) 3597 __enqueue_entity(cfs_rq, se); 3598 se->on_rq = 1; 3599 3600 if (cfs_rq->nr_running == 1) { 3601 list_add_leaf_cfs_rq(cfs_rq); 3602 check_enqueue_throttle(cfs_rq); 3603 } 3604 } 3605 3606 static void __clear_buddies_last(struct sched_entity *se) 3607 { 3608 for_each_sched_entity(se) { 3609 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3610 if (cfs_rq->last != se) 3611 break; 3612 3613 cfs_rq->last = NULL; 3614 } 3615 } 3616 3617 static void __clear_buddies_next(struct sched_entity *se) 3618 { 3619 for_each_sched_entity(se) { 3620 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3621 if (cfs_rq->next != se) 3622 break; 3623 3624 cfs_rq->next = NULL; 3625 } 3626 } 3627 3628 static void __clear_buddies_skip(struct sched_entity *se) 3629 { 3630 for_each_sched_entity(se) { 3631 struct cfs_rq *cfs_rq = cfs_rq_of(se); 3632 if (cfs_rq->skip != se) 3633 break; 3634 3635 cfs_rq->skip = NULL; 3636 } 3637 } 3638 3639 static void clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se) 3640 { 3641 if (cfs_rq->last == se) 3642 __clear_buddies_last(se); 3643 3644 if (cfs_rq->next == se) 3645 __clear_buddies_next(se); 3646 3647 if (cfs_rq->skip == se) 3648 __clear_buddies_skip(se); 3649 } 3650 3651 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq); 3652 3653 static void 3654 dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 3655 { 3656 /* 3657 * Update run-time statistics of the 'current'. 3658 */ 3659 update_curr(cfs_rq); 3660 update_load_avg(se, UPDATE_TG); 3661 dequeue_entity_load_avg(cfs_rq, se); 3662 3663 update_stats_dequeue(cfs_rq, se, flags); 3664 3665 clear_buddies(cfs_rq, se); 3666 3667 if (se != cfs_rq->curr) 3668 __dequeue_entity(cfs_rq, se); 3669 se->on_rq = 0; 3670 account_entity_dequeue(cfs_rq, se); 3671 3672 /* 3673 * Normalize after update_curr(); which will also have moved 3674 * min_vruntime if @se is the one holding it back. But before doing 3675 * update_min_vruntime() again, which will discount @se's position and 3676 * can move min_vruntime forward still more. 3677 */ 3678 if (!(flags & DEQUEUE_SLEEP)) 3679 se->vruntime -= cfs_rq->min_vruntime; 3680 3681 /* return excess runtime on last dequeue */ 3682 return_cfs_rq_runtime(cfs_rq); 3683 3684 update_cfs_shares(cfs_rq); 3685 3686 /* 3687 * Now advance min_vruntime if @se was the entity holding it back, 3688 * except when: DEQUEUE_SAVE && !DEQUEUE_MOVE, in this case we'll be 3689 * put back on, and if we advance min_vruntime, we'll be placed back 3690 * further than we started -- ie. we'll be penalized. 3691 */ 3692 if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE) 3693 update_min_vruntime(cfs_rq); 3694 } 3695 3696 /* 3697 * Preempt the current task with a newly woken task if needed: 3698 */ 3699 static void 3700 check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 3701 { 3702 unsigned long ideal_runtime, delta_exec; 3703 struct sched_entity *se; 3704 s64 delta; 3705 3706 ideal_runtime = sched_slice(cfs_rq, curr); 3707 delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime; 3708 if (delta_exec > ideal_runtime) { 3709 resched_curr(rq_of(cfs_rq)); 3710 /* 3711 * The current task ran long enough, ensure it doesn't get 3712 * re-elected due to buddy favours. 3713 */ 3714 clear_buddies(cfs_rq, curr); 3715 return; 3716 } 3717 3718 /* 3719 * Ensure that a task that missed wakeup preemption by a 3720 * narrow margin doesn't have to wait for a full slice. 3721 * This also mitigates buddy induced latencies under load. 3722 */ 3723 if (delta_exec < sysctl_sched_min_granularity) 3724 return; 3725 3726 se = __pick_first_entity(cfs_rq); 3727 delta = curr->vruntime - se->vruntime; 3728 3729 if (delta < 0) 3730 return; 3731 3732 if (delta > ideal_runtime) 3733 resched_curr(rq_of(cfs_rq)); 3734 } 3735 3736 static void 3737 set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 3738 { 3739 /* 'current' is not kept within the tree. */ 3740 if (se->on_rq) { 3741 /* 3742 * Any task has to be enqueued before it get to execute on 3743 * a CPU. So account for the time it spent waiting on the 3744 * runqueue. 3745 */ 3746 update_stats_wait_end(cfs_rq, se); 3747 __dequeue_entity(cfs_rq, se); 3748 update_load_avg(se, UPDATE_TG); 3749 } 3750 3751 update_stats_curr_start(cfs_rq, se); 3752 cfs_rq->curr = se; 3753 3754 /* 3755 * Track our maximum slice length, if the CPU's load is at 3756 * least twice that of our own weight (i.e. dont track it 3757 * when there are only lesser-weight tasks around): 3758 */ 3759 if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) { 3760 schedstat_set(se->statistics.slice_max, 3761 max((u64)schedstat_val(se->statistics.slice_max), 3762 se->sum_exec_runtime - se->prev_sum_exec_runtime)); 3763 } 3764 3765 se->prev_sum_exec_runtime = se->sum_exec_runtime; 3766 } 3767 3768 static int 3769 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se); 3770 3771 /* 3772 * Pick the next process, keeping these things in mind, in this order: 3773 * 1) keep things fair between processes/task groups 3774 * 2) pick the "next" process, since someone really wants that to run 3775 * 3) pick the "last" process, for cache locality 3776 * 4) do not run the "skip" process, if something else is available 3777 */ 3778 static struct sched_entity * 3779 pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) 3780 { 3781 struct sched_entity *left = __pick_first_entity(cfs_rq); 3782 struct sched_entity *se; 3783 3784 /* 3785 * If curr is set we have to see if its left of the leftmost entity 3786 * still in the tree, provided there was anything in the tree at all. 3787 */ 3788 if (!left || (curr && entity_before(curr, left))) 3789 left = curr; 3790 3791 se = left; /* ideally we run the leftmost entity */ 3792 3793 /* 3794 * Avoid running the skip buddy, if running something else can 3795 * be done without getting too unfair. 3796 */ 3797 if (cfs_rq->skip == se) { 3798 struct sched_entity *second; 3799 3800 if (se == curr) { 3801 second = __pick_first_entity(cfs_rq); 3802 } else { 3803 second = __pick_next_entity(se); 3804 if (!second || (curr && entity_before(curr, second))) 3805 second = curr; 3806 } 3807 3808 if (second && wakeup_preempt_entity(second, left) < 1) 3809 se = second; 3810 } 3811 3812 /* 3813 * Prefer last buddy, try to return the CPU to a preempted task. 3814 */ 3815 if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) 3816 se = cfs_rq->last; 3817 3818 /* 3819 * Someone really wants this to run. If it's not unfair, run it. 3820 */ 3821 if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) 3822 se = cfs_rq->next; 3823 3824 clear_buddies(cfs_rq, se); 3825 3826 return se; 3827 } 3828 3829 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq); 3830 3831 static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev) 3832 { 3833 /* 3834 * If still on the runqueue then deactivate_task() 3835 * was not called and update_curr() has to be done: 3836 */ 3837 if (prev->on_rq) 3838 update_curr(cfs_rq); 3839 3840 /* throttle cfs_rqs exceeding runtime */ 3841 check_cfs_rq_runtime(cfs_rq); 3842 3843 check_spread(cfs_rq, prev); 3844 3845 if (prev->on_rq) { 3846 update_stats_wait_start(cfs_rq, prev); 3847 /* Put 'current' back into the tree. */ 3848 __enqueue_entity(cfs_rq, prev); 3849 /* in !on_rq case, update occurred at dequeue */ 3850 update_load_avg(prev, 0); 3851 } 3852 cfs_rq->curr = NULL; 3853 } 3854 3855 static void 3856 entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued) 3857 { 3858 /* 3859 * Update run-time statistics of the 'current'. 3860 */ 3861 update_curr(cfs_rq); 3862 3863 /* 3864 * Ensure that runnable average is periodically updated. 3865 */ 3866 update_load_avg(curr, UPDATE_TG); 3867 update_cfs_shares(cfs_rq); 3868 3869 #ifdef CONFIG_SCHED_HRTICK 3870 /* 3871 * queued ticks are scheduled to match the slice, so don't bother 3872 * validating it and just reschedule. 3873 */ 3874 if (queued) { 3875 resched_curr(rq_of(cfs_rq)); 3876 return; 3877 } 3878 /* 3879 * don't let the period tick interfere with the hrtick preemption 3880 */ 3881 if (!sched_feat(DOUBLE_TICK) && 3882 hrtimer_active(&rq_of(cfs_rq)->hrtick_timer)) 3883 return; 3884 #endif 3885 3886 if (cfs_rq->nr_running > 1) 3887 check_preempt_tick(cfs_rq, curr); 3888 } 3889 3890 3891 /************************************************** 3892 * CFS bandwidth control machinery 3893 */ 3894 3895 #ifdef CONFIG_CFS_BANDWIDTH 3896 3897 #ifdef HAVE_JUMP_LABEL 3898 static struct static_key __cfs_bandwidth_used; 3899 3900 static inline bool cfs_bandwidth_used(void) 3901 { 3902 return static_key_false(&__cfs_bandwidth_used); 3903 } 3904 3905 void cfs_bandwidth_usage_inc(void) 3906 { 3907 static_key_slow_inc(&__cfs_bandwidth_used); 3908 } 3909 3910 void cfs_bandwidth_usage_dec(void) 3911 { 3912 static_key_slow_dec(&__cfs_bandwidth_used); 3913 } 3914 #else /* HAVE_JUMP_LABEL */ 3915 static bool cfs_bandwidth_used(void) 3916 { 3917 return true; 3918 } 3919 3920 void cfs_bandwidth_usage_inc(void) {} 3921 void cfs_bandwidth_usage_dec(void) {} 3922 #endif /* HAVE_JUMP_LABEL */ 3923 3924 /* 3925 * default period for cfs group bandwidth. 3926 * default: 0.1s, units: nanoseconds 3927 */ 3928 static inline u64 default_cfs_period(void) 3929 { 3930 return 100000000ULL; 3931 } 3932 3933 static inline u64 sched_cfs_bandwidth_slice(void) 3934 { 3935 return (u64)sysctl_sched_cfs_bandwidth_slice * NSEC_PER_USEC; 3936 } 3937 3938 /* 3939 * Replenish runtime according to assigned quota and update expiration time. 3940 * We use sched_clock_cpu directly instead of rq->clock to avoid adding 3941 * additional synchronization around rq->lock. 3942 * 3943 * requires cfs_b->lock 3944 */ 3945 void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) 3946 { 3947 u64 now; 3948 3949 if (cfs_b->quota == RUNTIME_INF) 3950 return; 3951 3952 now = sched_clock_cpu(smp_processor_id()); 3953 cfs_b->runtime = cfs_b->quota; 3954 cfs_b->runtime_expires = now + ktime_to_ns(cfs_b->period); 3955 } 3956 3957 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 3958 { 3959 return &tg->cfs_bandwidth; 3960 } 3961 3962 /* rq->task_clock normalized against any time this cfs_rq has spent throttled */ 3963 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 3964 { 3965 if (unlikely(cfs_rq->throttle_count)) 3966 return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time; 3967 3968 return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; 3969 } 3970 3971 /* returns 0 on failure to allocate runtime */ 3972 static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) 3973 { 3974 struct task_group *tg = cfs_rq->tg; 3975 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(tg); 3976 u64 amount = 0, min_amount, expires; 3977 3978 /* note: this is a positive sum as runtime_remaining <= 0 */ 3979 min_amount = sched_cfs_bandwidth_slice() - cfs_rq->runtime_remaining; 3980 3981 raw_spin_lock(&cfs_b->lock); 3982 if (cfs_b->quota == RUNTIME_INF) 3983 amount = min_amount; 3984 else { 3985 start_cfs_bandwidth(cfs_b); 3986 3987 if (cfs_b->runtime > 0) { 3988 amount = min(cfs_b->runtime, min_amount); 3989 cfs_b->runtime -= amount; 3990 cfs_b->idle = 0; 3991 } 3992 } 3993 expires = cfs_b->runtime_expires; 3994 raw_spin_unlock(&cfs_b->lock); 3995 3996 cfs_rq->runtime_remaining += amount; 3997 /* 3998 * we may have advanced our local expiration to account for allowed 3999 * spread between our sched_clock and the one on which runtime was 4000 * issued. 4001 */ 4002 if ((s64)(expires - cfs_rq->runtime_expires) > 0) 4003 cfs_rq->runtime_expires = expires; 4004 4005 return cfs_rq->runtime_remaining > 0; 4006 } 4007 4008 /* 4009 * Note: This depends on the synchronization provided by sched_clock and the 4010 * fact that rq->clock snapshots this value. 4011 */ 4012 static void expire_cfs_rq_runtime(struct cfs_rq *cfs_rq) 4013 { 4014 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 4015 4016 /* if the deadline is ahead of our clock, nothing to do */ 4017 if (likely((s64)(rq_clock(rq_of(cfs_rq)) - cfs_rq->runtime_expires) < 0)) 4018 return; 4019 4020 if (cfs_rq->runtime_remaining < 0) 4021 return; 4022 4023 /* 4024 * If the local deadline has passed we have to consider the 4025 * possibility that our sched_clock is 'fast' and the global deadline 4026 * has not truly expired. 4027 * 4028 * Fortunately we can check determine whether this the case by checking 4029 * whether the global deadline has advanced. It is valid to compare 4030 * cfs_b->runtime_expires without any locks since we only care about 4031 * exact equality, so a partial write will still work. 4032 */ 4033 4034 if (cfs_rq->runtime_expires != cfs_b->runtime_expires) { 4035 /* extend local deadline, drift is bounded above by 2 ticks */ 4036 cfs_rq->runtime_expires += TICK_NSEC; 4037 } else { 4038 /* global deadline is ahead, expiration has passed */ 4039 cfs_rq->runtime_remaining = 0; 4040 } 4041 } 4042 4043 static void __account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 4044 { 4045 /* dock delta_exec before expiring quota (as it could span periods) */ 4046 cfs_rq->runtime_remaining -= delta_exec; 4047 expire_cfs_rq_runtime(cfs_rq); 4048 4049 if (likely(cfs_rq->runtime_remaining > 0)) 4050 return; 4051 4052 /* 4053 * if we're unable to extend our runtime we resched so that the active 4054 * hierarchy can be throttled 4055 */ 4056 if (!assign_cfs_rq_runtime(cfs_rq) && likely(cfs_rq->curr)) 4057 resched_curr(rq_of(cfs_rq)); 4058 } 4059 4060 static __always_inline 4061 void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) 4062 { 4063 if (!cfs_bandwidth_used() || !cfs_rq->runtime_enabled) 4064 return; 4065 4066 __account_cfs_rq_runtime(cfs_rq, delta_exec); 4067 } 4068 4069 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 4070 { 4071 return cfs_bandwidth_used() && cfs_rq->throttled; 4072 } 4073 4074 /* check whether cfs_rq, or any parent, is throttled */ 4075 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 4076 { 4077 return cfs_bandwidth_used() && cfs_rq->throttle_count; 4078 } 4079 4080 /* 4081 * Ensure that neither of the group entities corresponding to src_cpu or 4082 * dest_cpu are members of a throttled hierarchy when performing group 4083 * load-balance operations. 4084 */ 4085 static inline int throttled_lb_pair(struct task_group *tg, 4086 int src_cpu, int dest_cpu) 4087 { 4088 struct cfs_rq *src_cfs_rq, *dest_cfs_rq; 4089 4090 src_cfs_rq = tg->cfs_rq[src_cpu]; 4091 dest_cfs_rq = tg->cfs_rq[dest_cpu]; 4092 4093 return throttled_hierarchy(src_cfs_rq) || 4094 throttled_hierarchy(dest_cfs_rq); 4095 } 4096 4097 /* updated child weight may affect parent so we have to do this bottom up */ 4098 static int tg_unthrottle_up(struct task_group *tg, void *data) 4099 { 4100 struct rq *rq = data; 4101 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 4102 4103 cfs_rq->throttle_count--; 4104 if (!cfs_rq->throttle_count) { 4105 /* adjust cfs_rq_clock_task() */ 4106 cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - 4107 cfs_rq->throttled_clock_task; 4108 } 4109 4110 return 0; 4111 } 4112 4113 static int tg_throttle_down(struct task_group *tg, void *data) 4114 { 4115 struct rq *rq = data; 4116 struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)]; 4117 4118 /* group is entering throttled state, stop time */ 4119 if (!cfs_rq->throttle_count) 4120 cfs_rq->throttled_clock_task = rq_clock_task(rq); 4121 cfs_rq->throttle_count++; 4122 4123 return 0; 4124 } 4125 4126 static void throttle_cfs_rq(struct cfs_rq *cfs_rq) 4127 { 4128 struct rq *rq = rq_of(cfs_rq); 4129 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 4130 struct sched_entity *se; 4131 long task_delta, dequeue = 1; 4132 bool empty; 4133 4134 se = cfs_rq->tg->se[cpu_of(rq_of(cfs_rq))]; 4135 4136 /* freeze hierarchy runnable averages while throttled */ 4137 rcu_read_lock(); 4138 walk_tg_tree_from(cfs_rq->tg, tg_throttle_down, tg_nop, (void *)rq); 4139 rcu_read_unlock(); 4140 4141 task_delta = cfs_rq->h_nr_running; 4142 for_each_sched_entity(se) { 4143 struct cfs_rq *qcfs_rq = cfs_rq_of(se); 4144 /* throttled entity or throttle-on-deactivate */ 4145 if (!se->on_rq) 4146 break; 4147 4148 if (dequeue) 4149 dequeue_entity(qcfs_rq, se, DEQUEUE_SLEEP); 4150 qcfs_rq->h_nr_running -= task_delta; 4151 4152 if (qcfs_rq->load.weight) 4153 dequeue = 0; 4154 } 4155 4156 if (!se) 4157 sub_nr_running(rq, task_delta); 4158 4159 cfs_rq->throttled = 1; 4160 cfs_rq->throttled_clock = rq_clock(rq); 4161 raw_spin_lock(&cfs_b->lock); 4162 empty = list_empty(&cfs_b->throttled_cfs_rq); 4163 4164 /* 4165 * Add to the _head_ of the list, so that an already-started 4166 * distribute_cfs_runtime will not see us 4167 */ 4168 list_add_rcu(&cfs_rq->throttled_list, &cfs_b->throttled_cfs_rq); 4169 4170 /* 4171 * If we're the first throttled task, make sure the bandwidth 4172 * timer is running. 4173 */ 4174 if (empty) 4175 start_cfs_bandwidth(cfs_b); 4176 4177 raw_spin_unlock(&cfs_b->lock); 4178 } 4179 4180 void unthrottle_cfs_rq(struct cfs_rq *cfs_rq) 4181 { 4182 struct rq *rq = rq_of(cfs_rq); 4183 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 4184 struct sched_entity *se; 4185 int enqueue = 1; 4186 long task_delta; 4187 4188 se = cfs_rq->tg->se[cpu_of(rq)]; 4189 4190 cfs_rq->throttled = 0; 4191 4192 update_rq_clock(rq); 4193 4194 raw_spin_lock(&cfs_b->lock); 4195 cfs_b->throttled_time += rq_clock(rq) - cfs_rq->throttled_clock; 4196 list_del_rcu(&cfs_rq->throttled_list); 4197 raw_spin_unlock(&cfs_b->lock); 4198 4199 /* update hierarchical throttle state */ 4200 walk_tg_tree_from(cfs_rq->tg, tg_nop, tg_unthrottle_up, (void *)rq); 4201 4202 if (!cfs_rq->load.weight) 4203 return; 4204 4205 task_delta = cfs_rq->h_nr_running; 4206 for_each_sched_entity(se) { 4207 if (se->on_rq) 4208 enqueue = 0; 4209 4210 cfs_rq = cfs_rq_of(se); 4211 if (enqueue) 4212 enqueue_entity(cfs_rq, se, ENQUEUE_WAKEUP); 4213 cfs_rq->h_nr_running += task_delta; 4214 4215 if (cfs_rq_throttled(cfs_rq)) 4216 break; 4217 } 4218 4219 if (!se) 4220 add_nr_running(rq, task_delta); 4221 4222 /* determine whether we need to wake up potentially idle cpu */ 4223 if (rq->curr == rq->idle && rq->cfs.nr_running) 4224 resched_curr(rq); 4225 } 4226 4227 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b, 4228 u64 remaining, u64 expires) 4229 { 4230 struct cfs_rq *cfs_rq; 4231 u64 runtime; 4232 u64 starting_runtime = remaining; 4233 4234 rcu_read_lock(); 4235 list_for_each_entry_rcu(cfs_rq, &cfs_b->throttled_cfs_rq, 4236 throttled_list) { 4237 struct rq *rq = rq_of(cfs_rq); 4238 4239 raw_spin_lock(&rq->lock); 4240 if (!cfs_rq_throttled(cfs_rq)) 4241 goto next; 4242 4243 runtime = -cfs_rq->runtime_remaining + 1; 4244 if (runtime > remaining) 4245 runtime = remaining; 4246 remaining -= runtime; 4247 4248 cfs_rq->runtime_remaining += runtime; 4249 cfs_rq->runtime_expires = expires; 4250 4251 /* we check whether we're throttled above */ 4252 if (cfs_rq->runtime_remaining > 0) 4253 unthrottle_cfs_rq(cfs_rq); 4254 4255 next: 4256 raw_spin_unlock(&rq->lock); 4257 4258 if (!remaining) 4259 break; 4260 } 4261 rcu_read_unlock(); 4262 4263 return starting_runtime - remaining; 4264 } 4265 4266 /* 4267 * Responsible for refilling a task_group's bandwidth and unthrottling its 4268 * cfs_rqs as appropriate. If there has been no activity within the last 4269 * period the timer is deactivated until scheduling resumes; cfs_b->idle is 4270 * used to track this state. 4271 */ 4272 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun) 4273 { 4274 u64 runtime, runtime_expires; 4275 int throttled; 4276 4277 /* no need to continue the timer with no bandwidth constraint */ 4278 if (cfs_b->quota == RUNTIME_INF) 4279 goto out_deactivate; 4280 4281 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 4282 cfs_b->nr_periods += overrun; 4283 4284 /* 4285 * idle depends on !throttled (for the case of a large deficit), and if 4286 * we're going inactive then everything else can be deferred 4287 */ 4288 if (cfs_b->idle && !throttled) 4289 goto out_deactivate; 4290 4291 __refill_cfs_bandwidth_runtime(cfs_b); 4292 4293 if (!throttled) { 4294 /* mark as potentially idle for the upcoming period */ 4295 cfs_b->idle = 1; 4296 return 0; 4297 } 4298 4299 /* account preceding periods in which throttling occurred */ 4300 cfs_b->nr_throttled += overrun; 4301 4302 runtime_expires = cfs_b->runtime_expires; 4303 4304 /* 4305 * This check is repeated as we are holding onto the new bandwidth while 4306 * we unthrottle. This can potentially race with an unthrottled group 4307 * trying to acquire new bandwidth from the global pool. This can result 4308 * in us over-using our runtime if it is all used during this loop, but 4309 * only by limited amounts in that extreme case. 4310 */ 4311 while (throttled && cfs_b->runtime > 0) { 4312 runtime = cfs_b->runtime; 4313 raw_spin_unlock(&cfs_b->lock); 4314 /* we can't nest cfs_b->lock while distributing bandwidth */ 4315 runtime = distribute_cfs_runtime(cfs_b, runtime, 4316 runtime_expires); 4317 raw_spin_lock(&cfs_b->lock); 4318 4319 throttled = !list_empty(&cfs_b->throttled_cfs_rq); 4320 4321 cfs_b->runtime -= min(runtime, cfs_b->runtime); 4322 } 4323 4324 /* 4325 * While we are ensured activity in the period following an 4326 * unthrottle, this also covers the case in which the new bandwidth is 4327 * insufficient to cover the existing bandwidth deficit. (Forcing the 4328 * timer to remain active while there are any throttled entities.) 4329 */ 4330 cfs_b->idle = 0; 4331 4332 return 0; 4333 4334 out_deactivate: 4335 return 1; 4336 } 4337 4338 /* a cfs_rq won't donate quota below this amount */ 4339 static const u64 min_cfs_rq_runtime = 1 * NSEC_PER_MSEC; 4340 /* minimum remaining period time to redistribute slack quota */ 4341 static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC; 4342 /* how long we wait to gather additional slack before distributing */ 4343 static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC; 4344 4345 /* 4346 * Are we near the end of the current quota period? 4347 * 4348 * Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the 4349 * hrtimer base being cleared by hrtimer_start. In the case of 4350 * migrate_hrtimers, base is never cleared, so we are fine. 4351 */ 4352 static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire) 4353 { 4354 struct hrtimer *refresh_timer = &cfs_b->period_timer; 4355 u64 remaining; 4356 4357 /* if the call-back is running a quota refresh is already occurring */ 4358 if (hrtimer_callback_running(refresh_timer)) 4359 return 1; 4360 4361 /* is a quota refresh about to occur? */ 4362 remaining = ktime_to_ns(hrtimer_expires_remaining(refresh_timer)); 4363 if (remaining < min_expire) 4364 return 1; 4365 4366 return 0; 4367 } 4368 4369 static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) 4370 { 4371 u64 min_left = cfs_bandwidth_slack_period + min_bandwidth_expiration; 4372 4373 /* if there's a quota refresh soon don't bother with slack */ 4374 if (runtime_refresh_within(cfs_b, min_left)) 4375 return; 4376 4377 hrtimer_start(&cfs_b->slack_timer, 4378 ns_to_ktime(cfs_bandwidth_slack_period), 4379 HRTIMER_MODE_REL); 4380 } 4381 4382 /* we know any runtime found here is valid as update_curr() precedes return */ 4383 static void __return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 4384 { 4385 struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg); 4386 s64 slack_runtime = cfs_rq->runtime_remaining - min_cfs_rq_runtime; 4387 4388 if (slack_runtime <= 0) 4389 return; 4390 4391 raw_spin_lock(&cfs_b->lock); 4392 if (cfs_b->quota != RUNTIME_INF && 4393 cfs_rq->runtime_expires == cfs_b->runtime_expires) { 4394 cfs_b->runtime += slack_runtime; 4395 4396 /* we are under rq->lock, defer unthrottling using a timer */ 4397 if (cfs_b->runtime > sched_cfs_bandwidth_slice() && 4398 !list_empty(&cfs_b->throttled_cfs_rq)) 4399 start_cfs_slack_bandwidth(cfs_b); 4400 } 4401 raw_spin_unlock(&cfs_b->lock); 4402 4403 /* even if it's not valid for return we don't want to try again */ 4404 cfs_rq->runtime_remaining -= slack_runtime; 4405 } 4406 4407 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) 4408 { 4409 if (!cfs_bandwidth_used()) 4410 return; 4411 4412 if (!cfs_rq->runtime_enabled || cfs_rq->nr_running) 4413 return; 4414 4415 __return_cfs_rq_runtime(cfs_rq); 4416 } 4417 4418 /* 4419 * This is done with a timer (instead of inline with bandwidth return) since 4420 * it's necessary to juggle rq->locks to unthrottle their respective cfs_rqs. 4421 */ 4422 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) 4423 { 4424 u64 runtime = 0, slice = sched_cfs_bandwidth_slice(); 4425 u64 expires; 4426 4427 /* confirm we're still not at a refresh boundary */ 4428 raw_spin_lock(&cfs_b->lock); 4429 if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) { 4430 raw_spin_unlock(&cfs_b->lock); 4431 return; 4432 } 4433 4434 if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) 4435 runtime = cfs_b->runtime; 4436 4437 expires = cfs_b->runtime_expires; 4438 raw_spin_unlock(&cfs_b->lock); 4439 4440 if (!runtime) 4441 return; 4442 4443 runtime = distribute_cfs_runtime(cfs_b, runtime, expires); 4444 4445 raw_spin_lock(&cfs_b->lock); 4446 if (expires == cfs_b->runtime_expires) 4447 cfs_b->runtime -= min(runtime, cfs_b->runtime); 4448 raw_spin_unlock(&cfs_b->lock); 4449 } 4450 4451 /* 4452 * When a group wakes up we want to make sure that its quota is not already 4453 * expired/exceeded, otherwise it may be allowed to steal additional ticks of 4454 * runtime as update_curr() throttling can not not trigger until it's on-rq. 4455 */ 4456 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) 4457 { 4458 if (!cfs_bandwidth_used()) 4459 return; 4460 4461 /* an active group must be handled by the update_curr()->put() path */ 4462 if (!cfs_rq->runtime_enabled || cfs_rq->curr) 4463 return; 4464 4465 /* ensure the group is not already throttled */ 4466 if (cfs_rq_throttled(cfs_rq)) 4467 return; 4468 4469 /* update runtime allocation */ 4470 account_cfs_rq_runtime(cfs_rq, 0); 4471 if (cfs_rq->runtime_remaining <= 0) 4472 throttle_cfs_rq(cfs_rq); 4473 } 4474 4475 static void sync_throttle(struct task_group *tg, int cpu) 4476 { 4477 struct cfs_rq *pcfs_rq, *cfs_rq; 4478 4479 if (!cfs_bandwidth_used()) 4480 return; 4481 4482 if (!tg->parent) 4483 return; 4484 4485 cfs_rq = tg->cfs_rq[cpu]; 4486 pcfs_rq = tg->parent->cfs_rq[cpu]; 4487 4488 cfs_rq->throttle_count = pcfs_rq->throttle_count; 4489 cfs_rq->throttled_clock_task = rq_clock_task(cpu_rq(cpu)); 4490 } 4491 4492 /* conditionally throttle active cfs_rq's from put_prev_entity() */ 4493 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) 4494 { 4495 if (!cfs_bandwidth_used()) 4496 return false; 4497 4498 if (likely(!cfs_rq->runtime_enabled || cfs_rq->runtime_remaining > 0)) 4499 return false; 4500 4501 /* 4502 * it's possible for a throttled entity to be forced into a running 4503 * state (e.g. set_curr_task), in this case we're finished. 4504 */ 4505 if (cfs_rq_throttled(cfs_rq)) 4506 return true; 4507 4508 throttle_cfs_rq(cfs_rq); 4509 return true; 4510 } 4511 4512 static enum hrtimer_restart sched_cfs_slack_timer(struct hrtimer *timer) 4513 { 4514 struct cfs_bandwidth *cfs_b = 4515 container_of(timer, struct cfs_bandwidth, slack_timer); 4516 4517 do_sched_cfs_slack_timer(cfs_b); 4518 4519 return HRTIMER_NORESTART; 4520 } 4521 4522 static enum hrtimer_restart sched_cfs_period_timer(struct hrtimer *timer) 4523 { 4524 struct cfs_bandwidth *cfs_b = 4525 container_of(timer, struct cfs_bandwidth, period_timer); 4526 int overrun; 4527 int idle = 0; 4528 4529 raw_spin_lock(&cfs_b->lock); 4530 for (;;) { 4531 overrun = hrtimer_forward_now(timer, cfs_b->period); 4532 if (!overrun) 4533 break; 4534 4535 idle = do_sched_cfs_period_timer(cfs_b, overrun); 4536 } 4537 if (idle) 4538 cfs_b->period_active = 0; 4539 raw_spin_unlock(&cfs_b->lock); 4540 4541 return idle ? HRTIMER_NORESTART : HRTIMER_RESTART; 4542 } 4543 4544 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 4545 { 4546 raw_spin_lock_init(&cfs_b->lock); 4547 cfs_b->runtime = 0; 4548 cfs_b->quota = RUNTIME_INF; 4549 cfs_b->period = ns_to_ktime(default_cfs_period()); 4550 4551 INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); 4552 hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); 4553 cfs_b->period_timer.function = sched_cfs_period_timer; 4554 hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 4555 cfs_b->slack_timer.function = sched_cfs_slack_timer; 4556 } 4557 4558 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) 4559 { 4560 cfs_rq->runtime_enabled = 0; 4561 INIT_LIST_HEAD(&cfs_rq->throttled_list); 4562 } 4563 4564 void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 4565 { 4566 lockdep_assert_held(&cfs_b->lock); 4567 4568 if (!cfs_b->period_active) { 4569 cfs_b->period_active = 1; 4570 hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); 4571 hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); 4572 } 4573 } 4574 4575 static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) 4576 { 4577 /* init_cfs_bandwidth() was not called */ 4578 if (!cfs_b->throttled_cfs_rq.next) 4579 return; 4580 4581 hrtimer_cancel(&cfs_b->period_timer); 4582 hrtimer_cancel(&cfs_b->slack_timer); 4583 } 4584 4585 static void __maybe_unused update_runtime_enabled(struct rq *rq) 4586 { 4587 struct cfs_rq *cfs_rq; 4588 4589 for_each_leaf_cfs_rq(rq, cfs_rq) { 4590 struct cfs_bandwidth *cfs_b = &cfs_rq->tg->cfs_bandwidth; 4591 4592 raw_spin_lock(&cfs_b->lock); 4593 cfs_rq->runtime_enabled = cfs_b->quota != RUNTIME_INF; 4594 raw_spin_unlock(&cfs_b->lock); 4595 } 4596 } 4597 4598 static void __maybe_unused unthrottle_offline_cfs_rqs(struct rq *rq) 4599 { 4600 struct cfs_rq *cfs_rq; 4601 4602 for_each_leaf_cfs_rq(rq, cfs_rq) { 4603 if (!cfs_rq->runtime_enabled) 4604 continue; 4605 4606 /* 4607 * clock_task is not advancing so we just need to make sure 4608 * there's some valid quota amount 4609 */ 4610 cfs_rq->runtime_remaining = 1; 4611 /* 4612 * Offline rq is schedulable till cpu is completely disabled 4613 * in take_cpu_down(), so we prevent new cfs throttling here. 4614 */ 4615 cfs_rq->runtime_enabled = 0; 4616 4617 if (cfs_rq_throttled(cfs_rq)) 4618 unthrottle_cfs_rq(cfs_rq); 4619 } 4620 } 4621 4622 #else /* CONFIG_CFS_BANDWIDTH */ 4623 static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) 4624 { 4625 return rq_clock_task(rq_of(cfs_rq)); 4626 } 4627 4628 static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} 4629 static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } 4630 static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} 4631 static inline void sync_throttle(struct task_group *tg, int cpu) {} 4632 static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 4633 4634 static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 4635 { 4636 return 0; 4637 } 4638 4639 static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) 4640 { 4641 return 0; 4642 } 4643 4644 static inline int throttled_lb_pair(struct task_group *tg, 4645 int src_cpu, int dest_cpu) 4646 { 4647 return 0; 4648 } 4649 4650 void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 4651 4652 #ifdef CONFIG_FAIR_GROUP_SCHED 4653 static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) {} 4654 #endif 4655 4656 static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) 4657 { 4658 return NULL; 4659 } 4660 static inline void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b) {} 4661 static inline void update_runtime_enabled(struct rq *rq) {} 4662 static inline void unthrottle_offline_cfs_rqs(struct rq *rq) {} 4663 4664 #endif /* CONFIG_CFS_BANDWIDTH */ 4665 4666 /************************************************** 4667 * CFS operations on tasks: 4668 */ 4669 4670 #ifdef CONFIG_SCHED_HRTICK 4671 static void hrtick_start_fair(struct rq *rq, struct task_struct *p) 4672 { 4673 struct sched_entity *se = &p->se; 4674 struct cfs_rq *cfs_rq = cfs_rq_of(se); 4675 4676 SCHED_WARN_ON(task_rq(p) != rq); 4677 4678 if (rq->cfs.h_nr_running > 1) { 4679 u64 slice = sched_slice(cfs_rq, se); 4680 u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; 4681 s64 delta = slice - ran; 4682 4683 if (delta < 0) { 4684 if (rq->curr == p) 4685 resched_curr(rq); 4686 return; 4687 } 4688 hrtick_start(rq, delta); 4689 } 4690 } 4691 4692 /* 4693 * called from enqueue/dequeue and updates the hrtick when the 4694 * current task is from our class and nr_running is low enough 4695 * to matter. 4696 */ 4697 static void hrtick_update(struct rq *rq) 4698 { 4699 struct task_struct *curr = rq->curr; 4700 4701 if (!hrtick_enabled(rq) || curr->sched_class != &fair_sched_class) 4702 return; 4703 4704 if (cfs_rq_of(&curr->se)->nr_running < sched_nr_latency) 4705 hrtick_start_fair(rq, curr); 4706 } 4707 #else /* !CONFIG_SCHED_HRTICK */ 4708 static inline void 4709 hrtick_start_fair(struct rq *rq, struct task_struct *p) 4710 { 4711 } 4712 4713 static inline void hrtick_update(struct rq *rq) 4714 { 4715 } 4716 #endif 4717 4718 /* 4719 * The enqueue_task method is called before nr_running is 4720 * increased. Here we update the fair scheduling stats and 4721 * then put the task into the rbtree: 4722 */ 4723 static void 4724 enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 4725 { 4726 struct cfs_rq *cfs_rq; 4727 struct sched_entity *se = &p->se; 4728 4729 /* 4730 * If in_iowait is set, the code below may not trigger any cpufreq 4731 * utilization updates, so do it here explicitly with the IOWAIT flag 4732 * passed. 4733 */ 4734 if (p->in_iowait) 4735 cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT); 4736 4737 for_each_sched_entity(se) { 4738 if (se->on_rq) 4739 break; 4740 cfs_rq = cfs_rq_of(se); 4741 enqueue_entity(cfs_rq, se, flags); 4742 4743 /* 4744 * end evaluation on encountering a throttled cfs_rq 4745 * 4746 * note: in the case of encountering a throttled cfs_rq we will 4747 * post the final h_nr_running increment below. 4748 */ 4749 if (cfs_rq_throttled(cfs_rq)) 4750 break; 4751 cfs_rq->h_nr_running++; 4752 4753 flags = ENQUEUE_WAKEUP; 4754 } 4755 4756 for_each_sched_entity(se) { 4757 cfs_rq = cfs_rq_of(se); 4758 cfs_rq->h_nr_running++; 4759 4760 if (cfs_rq_throttled(cfs_rq)) 4761 break; 4762 4763 update_load_avg(se, UPDATE_TG); 4764 update_cfs_shares(cfs_rq); 4765 } 4766 4767 if (!se) 4768 add_nr_running(rq, 1); 4769 4770 hrtick_update(rq); 4771 } 4772 4773 static void set_next_buddy(struct sched_entity *se); 4774 4775 /* 4776 * The dequeue_task method is called before nr_running is 4777 * decreased. We remove the task from the rbtree and 4778 * update the fair scheduling stats: 4779 */ 4780 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 4781 { 4782 struct cfs_rq *cfs_rq; 4783 struct sched_entity *se = &p->se; 4784 int task_sleep = flags & DEQUEUE_SLEEP; 4785 4786 for_each_sched_entity(se) { 4787 cfs_rq = cfs_rq_of(se); 4788 dequeue_entity(cfs_rq, se, flags); 4789 4790 /* 4791 * end evaluation on encountering a throttled cfs_rq 4792 * 4793 * note: in the case of encountering a throttled cfs_rq we will 4794 * post the final h_nr_running decrement below. 4795 */ 4796 if (cfs_rq_throttled(cfs_rq)) 4797 break; 4798 cfs_rq->h_nr_running--; 4799 4800 /* Don't dequeue parent if it has other entities besides us */ 4801 if (cfs_rq->load.weight) { 4802 /* Avoid re-evaluating load for this entity: */ 4803 se = parent_entity(se); 4804 /* 4805 * Bias pick_next to pick a task from this cfs_rq, as 4806 * p is sleeping when it is within its sched_slice. 4807 */ 4808 if (task_sleep && se && !throttled_hierarchy(cfs_rq)) 4809 set_next_buddy(se); 4810 break; 4811 } 4812 flags |= DEQUEUE_SLEEP; 4813 } 4814 4815 for_each_sched_entity(se) { 4816 cfs_rq = cfs_rq_of(se); 4817 cfs_rq->h_nr_running--; 4818 4819 if (cfs_rq_throttled(cfs_rq)) 4820 break; 4821 4822 update_load_avg(se, UPDATE_TG); 4823 update_cfs_shares(cfs_rq); 4824 } 4825 4826 if (!se) 4827 sub_nr_running(rq, 1); 4828 4829 hrtick_update(rq); 4830 } 4831 4832 #ifdef CONFIG_SMP 4833 4834 /* Working cpumask for: load_balance, load_balance_newidle. */ 4835 DEFINE_PER_CPU(cpumask_var_t, load_balance_mask); 4836 DEFINE_PER_CPU(cpumask_var_t, select_idle_mask); 4837 4838 #ifdef CONFIG_NO_HZ_COMMON 4839 /* 4840 * per rq 'load' arrray crap; XXX kill this. 4841 */ 4842 4843 /* 4844 * The exact cpuload calculated at every tick would be: 4845 * 4846 * load' = (1 - 1/2^i) * load + (1/2^i) * cur_load 4847 * 4848 * If a cpu misses updates for n ticks (as it was idle) and update gets 4849 * called on the n+1-th tick when cpu may be busy, then we have: 4850 * 4851 * load_n = (1 - 1/2^i)^n * load_0 4852 * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * cur_load 4853 * 4854 * decay_load_missed() below does efficient calculation of 4855 * 4856 * load' = (1 - 1/2^i)^n * load 4857 * 4858 * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors. 4859 * This allows us to precompute the above in said factors, thereby allowing the 4860 * reduction of an arbitrary n in O(log_2 n) steps. (See also 4861 * fixed_power_int()) 4862 * 4863 * The calculation is approximated on a 128 point scale. 4864 */ 4865 #define DEGRADE_SHIFT 7 4866 4867 static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128}; 4868 static const u8 degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = { 4869 { 0, 0, 0, 0, 0, 0, 0, 0 }, 4870 { 64, 32, 8, 0, 0, 0, 0, 0 }, 4871 { 96, 72, 40, 12, 1, 0, 0, 0 }, 4872 { 112, 98, 75, 43, 15, 1, 0, 0 }, 4873 { 120, 112, 98, 76, 45, 16, 2, 0 } 4874 }; 4875 4876 /* 4877 * Update cpu_load for any missed ticks, due to tickless idle. The backlog 4878 * would be when CPU is idle and so we just decay the old load without 4879 * adding any new load. 4880 */ 4881 static unsigned long 4882 decay_load_missed(unsigned long load, unsigned long missed_updates, int idx) 4883 { 4884 int j = 0; 4885 4886 if (!missed_updates) 4887 return load; 4888 4889 if (missed_updates >= degrade_zero_ticks[idx]) 4890 return 0; 4891 4892 if (idx == 1) 4893 return load >> missed_updates; 4894 4895 while (missed_updates) { 4896 if (missed_updates % 2) 4897 load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT; 4898 4899 missed_updates >>= 1; 4900 j++; 4901 } 4902 return load; 4903 } 4904 #endif /* CONFIG_NO_HZ_COMMON */ 4905 4906 /** 4907 * __cpu_load_update - update the rq->cpu_load[] statistics 4908 * @this_rq: The rq to update statistics for 4909 * @this_load: The current load 4910 * @pending_updates: The number of missed updates 4911 * 4912 * Update rq->cpu_load[] statistics. This function is usually called every 4913 * scheduler tick (TICK_NSEC). 4914 * 4915 * This function computes a decaying average: 4916 * 4917 * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load 4918 * 4919 * Because of NOHZ it might not get called on every tick which gives need for 4920 * the @pending_updates argument. 4921 * 4922 * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1 4923 * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load 4924 * = A * (A * load[i]_n-2 + B) + B 4925 * = A * (A * (A * load[i]_n-3 + B) + B) + B 4926 * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B 4927 * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B 4928 * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B 4929 * = (1 - 1/2^i)^n * (load[i]_0 - load) + load 4930 * 4931 * In the above we've assumed load_n := load, which is true for NOHZ_FULL as 4932 * any change in load would have resulted in the tick being turned back on. 4933 * 4934 * For regular NOHZ, this reduces to: 4935 * 4936 * load[i]_n = (1 - 1/2^i)^n * load[i]_0 4937 * 4938 * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra 4939 * term. 4940 */ 4941 static void cpu_load_update(struct rq *this_rq, unsigned long this_load, 4942 unsigned long pending_updates) 4943 { 4944 unsigned long __maybe_unused tickless_load = this_rq->cpu_load[0]; 4945 int i, scale; 4946 4947 this_rq->nr_load_updates++; 4948 4949 /* Update our load: */ 4950 this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */ 4951 for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) { 4952 unsigned long old_load, new_load; 4953 4954 /* scale is effectively 1 << i now, and >> i divides by scale */ 4955 4956 old_load = this_rq->cpu_load[i]; 4957 #ifdef CONFIG_NO_HZ_COMMON 4958 old_load = decay_load_missed(old_load, pending_updates - 1, i); 4959 if (tickless_load) { 4960 old_load -= decay_load_missed(tickless_load, pending_updates - 1, i); 4961 /* 4962 * old_load can never be a negative value because a 4963 * decayed tickless_load cannot be greater than the 4964 * original tickless_load. 4965 */ 4966 old_load += tickless_load; 4967 } 4968 #endif 4969 new_load = this_load; 4970 /* 4971 * Round up the averaging division if load is increasing. This 4972 * prevents us from getting stuck on 9 if the load is 10, for 4973 * example. 4974 */ 4975 if (new_load > old_load) 4976 new_load += scale - 1; 4977 4978 this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i; 4979 } 4980 4981 sched_avg_update(this_rq); 4982 } 4983 4984 /* Used instead of source_load when we know the type == 0 */ 4985 static unsigned long weighted_cpuload(const int cpu) 4986 { 4987 return cfs_rq_runnable_load_avg(&cpu_rq(cpu)->cfs); 4988 } 4989 4990 #ifdef CONFIG_NO_HZ_COMMON 4991 /* 4992 * There is no sane way to deal with nohz on smp when using jiffies because the 4993 * cpu doing the jiffies update might drift wrt the cpu doing the jiffy reading 4994 * causing off-by-one errors in observed deltas; {0,2} instead of {1,1}. 4995 * 4996 * Therefore we need to avoid the delta approach from the regular tick when 4997 * possible since that would seriously skew the load calculation. This is why we 4998 * use cpu_load_update_periodic() for CPUs out of nohz. However we'll rely on 4999 * jiffies deltas for updates happening while in nohz mode (idle ticks, idle 5000 * loop exit, nohz_idle_balance, nohz full exit...) 5001 * 5002 * This means we might still be one tick off for nohz periods. 5003 */ 5004 5005 static void cpu_load_update_nohz(struct rq *this_rq, 5006 unsigned long curr_jiffies, 5007 unsigned long load) 5008 { 5009 unsigned long pending_updates; 5010 5011 pending_updates = curr_jiffies - this_rq->last_load_update_tick; 5012 if (pending_updates) { 5013 this_rq->last_load_update_tick = curr_jiffies; 5014 /* 5015 * In the regular NOHZ case, we were idle, this means load 0. 5016 * In the NOHZ_FULL case, we were non-idle, we should consider 5017 * its weighted load. 5018 */ 5019 cpu_load_update(this_rq, load, pending_updates); 5020 } 5021 } 5022 5023 /* 5024 * Called from nohz_idle_balance() to update the load ratings before doing the 5025 * idle balance. 5026 */ 5027 static void cpu_load_update_idle(struct rq *this_rq) 5028 { 5029 /* 5030 * bail if there's load or we're actually up-to-date. 5031 */ 5032 if (weighted_cpuload(cpu_of(this_rq))) 5033 return; 5034 5035 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), 0); 5036 } 5037 5038 /* 5039 * Record CPU load on nohz entry so we know the tickless load to account 5040 * on nohz exit. cpu_load[0] happens then to be updated more frequently 5041 * than other cpu_load[idx] but it should be fine as cpu_load readers 5042 * shouldn't rely into synchronized cpu_load[*] updates. 5043 */ 5044 void cpu_load_update_nohz_start(void) 5045 { 5046 struct rq *this_rq = this_rq(); 5047 5048 /* 5049 * This is all lockless but should be fine. If weighted_cpuload changes 5050 * concurrently we'll exit nohz. And cpu_load write can race with 5051 * cpu_load_update_idle() but both updater would be writing the same. 5052 */ 5053 this_rq->cpu_load[0] = weighted_cpuload(cpu_of(this_rq)); 5054 } 5055 5056 /* 5057 * Account the tickless load in the end of a nohz frame. 5058 */ 5059 void cpu_load_update_nohz_stop(void) 5060 { 5061 unsigned long curr_jiffies = READ_ONCE(jiffies); 5062 struct rq *this_rq = this_rq(); 5063 unsigned long load; 5064 5065 if (curr_jiffies == this_rq->last_load_update_tick) 5066 return; 5067 5068 load = weighted_cpuload(cpu_of(this_rq)); 5069 raw_spin_lock(&this_rq->lock); 5070 update_rq_clock(this_rq); 5071 cpu_load_update_nohz(this_rq, curr_jiffies, load); 5072 raw_spin_unlock(&this_rq->lock); 5073 } 5074 #else /* !CONFIG_NO_HZ_COMMON */ 5075 static inline void cpu_load_update_nohz(struct rq *this_rq, 5076 unsigned long curr_jiffies, 5077 unsigned long load) { } 5078 #endif /* CONFIG_NO_HZ_COMMON */ 5079 5080 static void cpu_load_update_periodic(struct rq *this_rq, unsigned long load) 5081 { 5082 #ifdef CONFIG_NO_HZ_COMMON 5083 /* See the mess around cpu_load_update_nohz(). */ 5084 this_rq->last_load_update_tick = READ_ONCE(jiffies); 5085 #endif 5086 cpu_load_update(this_rq, load, 1); 5087 } 5088 5089 /* 5090 * Called from scheduler_tick() 5091 */ 5092 void cpu_load_update_active(struct rq *this_rq) 5093 { 5094 unsigned long load = weighted_cpuload(cpu_of(this_rq)); 5095 5096 if (tick_nohz_tick_stopped()) 5097 cpu_load_update_nohz(this_rq, READ_ONCE(jiffies), load); 5098 else 5099 cpu_load_update_periodic(this_rq, load); 5100 } 5101 5102 /* 5103 * Return a low guess at the load of a migration-source cpu weighted 5104 * according to the scheduling class and "nice" value. 5105 * 5106 * We want to under-estimate the load of migration sources, to 5107 * balance conservatively. 5108 */ 5109 static unsigned long source_load(int cpu, int type) 5110 { 5111 struct rq *rq = cpu_rq(cpu); 5112 unsigned long total = weighted_cpuload(cpu); 5113 5114 if (type == 0 || !sched_feat(LB_BIAS)) 5115 return total; 5116 5117 return min(rq->cpu_load[type-1], total); 5118 } 5119 5120 /* 5121 * Return a high guess at the load of a migration-target cpu weighted 5122 * according to the scheduling class and "nice" value. 5123 */ 5124 static unsigned long target_load(int cpu, int type) 5125 { 5126 struct rq *rq = cpu_rq(cpu); 5127 unsigned long total = weighted_cpuload(cpu); 5128 5129 if (type == 0 || !sched_feat(LB_BIAS)) 5130 return total; 5131 5132 return max(rq->cpu_load[type-1], total); 5133 } 5134 5135 static unsigned long capacity_of(int cpu) 5136 { 5137 return cpu_rq(cpu)->cpu_capacity; 5138 } 5139 5140 static unsigned long capacity_orig_of(int cpu) 5141 { 5142 return cpu_rq(cpu)->cpu_capacity_orig; 5143 } 5144 5145 static unsigned long cpu_avg_load_per_task(int cpu) 5146 { 5147 struct rq *rq = cpu_rq(cpu); 5148 unsigned long nr_running = READ_ONCE(rq->cfs.h_nr_running); 5149 unsigned long load_avg = weighted_cpuload(cpu); 5150 5151 if (nr_running) 5152 return load_avg / nr_running; 5153 5154 return 0; 5155 } 5156 5157 #ifdef CONFIG_FAIR_GROUP_SCHED 5158 /* 5159 * effective_load() calculates the load change as seen from the root_task_group 5160 * 5161 * Adding load to a group doesn't make a group heavier, but can cause movement 5162 * of group shares between cpus. Assuming the shares were perfectly aligned one 5163 * can calculate the shift in shares. 5164 * 5165 * Calculate the effective load difference if @wl is added (subtracted) to @tg 5166 * on this @cpu and results in a total addition (subtraction) of @wg to the 5167 * total group weight. 5168 * 5169 * Given a runqueue weight distribution (rw_i) we can compute a shares 5170 * distribution (s_i) using: 5171 * 5172 * s_i = rw_i / \Sum rw_j (1) 5173 * 5174 * Suppose we have 4 CPUs and our @tg is a direct child of the root group and 5175 * has 7 equal weight tasks, distributed as below (rw_i), with the resulting 5176 * shares distribution (s_i): 5177 * 5178 * rw_i = { 2, 4, 1, 0 } 5179 * s_i = { 2/7, 4/7, 1/7, 0 } 5180 * 5181 * As per wake_affine() we're interested in the load of two CPUs (the CPU the 5182 * task used to run on and the CPU the waker is running on), we need to 5183 * compute the effect of waking a task on either CPU and, in case of a sync 5184 * wakeup, compute the effect of the current task going to sleep. 5185 * 5186 * So for a change of @wl to the local @cpu with an overall group weight change 5187 * of @wl we can compute the new shares distribution (s'_i) using: 5188 * 5189 * s'_i = (rw_i + @wl) / (@wg + \Sum rw_j) (2) 5190 * 5191 * Suppose we're interested in CPUs 0 and 1, and want to compute the load 5192 * differences in waking a task to CPU 0. The additional task changes the 5193 * weight and shares distributions like: 5194 * 5195 * rw'_i = { 3, 4, 1, 0 } 5196 * s'_i = { 3/8, 4/8, 1/8, 0 } 5197 * 5198 * We can then compute the difference in effective weight by using: 5199 * 5200 * dw_i = S * (s'_i - s_i) (3) 5201 * 5202 * Where 'S' is the group weight as seen by its parent. 5203 * 5204 * Therefore the effective change in loads on CPU 0 would be 5/56 (3/8 - 2/7) 5205 * times the weight of the group. The effect on CPU 1 would be -4/56 (4/8 - 5206 * 4/7) times the weight of the group. 5207 */ 5208 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 5209 { 5210 struct sched_entity *se = tg->se[cpu]; 5211 5212 if (!tg->parent) /* the trivial, non-cgroup case */ 5213 return wl; 5214 5215 for_each_sched_entity(se) { 5216 struct cfs_rq *cfs_rq = se->my_q; 5217 long W, w = cfs_rq_load_avg(cfs_rq); 5218 5219 tg = cfs_rq->tg; 5220 5221 /* 5222 * W = @wg + \Sum rw_j 5223 */ 5224 W = wg + atomic_long_read(&tg->load_avg); 5225 5226 /* Ensure \Sum rw_j >= rw_i */ 5227 W -= cfs_rq->tg_load_avg_contrib; 5228 W += w; 5229 5230 /* 5231 * w = rw_i + @wl 5232 */ 5233 w += wl; 5234 5235 /* 5236 * wl = S * s'_i; see (2) 5237 */ 5238 if (W > 0 && w < W) 5239 wl = (w * (long)scale_load_down(tg->shares)) / W; 5240 else 5241 wl = scale_load_down(tg->shares); 5242 5243 /* 5244 * Per the above, wl is the new se->load.weight value; since 5245 * those are clipped to [MIN_SHARES, ...) do so now. See 5246 * calc_cfs_shares(). 5247 */ 5248 if (wl < MIN_SHARES) 5249 wl = MIN_SHARES; 5250 5251 /* 5252 * wl = dw_i = S * (s'_i - s_i); see (3) 5253 */ 5254 wl -= se->avg.load_avg; 5255 5256 /* 5257 * Recursively apply this logic to all parent groups to compute 5258 * the final effective load change on the root group. Since 5259 * only the @tg group gets extra weight, all parent groups can 5260 * only redistribute existing shares. @wl is the shift in shares 5261 * resulting from this level per the above. 5262 */ 5263 wg = 0; 5264 } 5265 5266 return wl; 5267 } 5268 #else 5269 5270 static long effective_load(struct task_group *tg, int cpu, long wl, long wg) 5271 { 5272 return wl; 5273 } 5274 5275 #endif 5276 5277 static void record_wakee(struct task_struct *p) 5278 { 5279 /* 5280 * Only decay a single time; tasks that have less then 1 wakeup per 5281 * jiffy will not have built up many flips. 5282 */ 5283 if (time_after(jiffies, current->wakee_flip_decay_ts + HZ)) { 5284 current->wakee_flips >>= 1; 5285 current->wakee_flip_decay_ts = jiffies; 5286 } 5287 5288 if (current->last_wakee != p) { 5289 current->last_wakee = p; 5290 current->wakee_flips++; 5291 } 5292 } 5293 5294 /* 5295 * Detect M:N waker/wakee relationships via a switching-frequency heuristic. 5296 * 5297 * A waker of many should wake a different task than the one last awakened 5298 * at a frequency roughly N times higher than one of its wakees. 5299 * 5300 * In order to determine whether we should let the load spread vs consolidating 5301 * to shared cache, we look for a minimum 'flip' frequency of llc_size in one 5302 * partner, and a factor of lls_size higher frequency in the other. 5303 * 5304 * With both conditions met, we can be relatively sure that the relationship is 5305 * non-monogamous, with partner count exceeding socket size. 5306 * 5307 * Waker/wakee being client/server, worker/dispatcher, interrupt source or 5308 * whatever is irrelevant, spread criteria is apparent partner count exceeds 5309 * socket size. 5310 */ 5311 static int wake_wide(struct task_struct *p) 5312 { 5313 unsigned int master = current->wakee_flips; 5314 unsigned int slave = p->wakee_flips; 5315 int factor = this_cpu_read(sd_llc_size); 5316 5317 if (master < slave) 5318 swap(master, slave); 5319 if (slave < factor || master < slave * factor) 5320 return 0; 5321 return 1; 5322 } 5323 5324 static int wake_affine(struct sched_domain *sd, struct task_struct *p, 5325 int prev_cpu, int sync) 5326 { 5327 s64 this_load, load; 5328 s64 this_eff_load, prev_eff_load; 5329 int idx, this_cpu; 5330 struct task_group *tg; 5331 unsigned long weight; 5332 int balanced; 5333 5334 idx = sd->wake_idx; 5335 this_cpu = smp_processor_id(); 5336 load = source_load(prev_cpu, idx); 5337 this_load = target_load(this_cpu, idx); 5338 5339 /* 5340 * If sync wakeup then subtract the (maximum possible) 5341 * effect of the currently running task from the load 5342 * of the current CPU: 5343 */ 5344 if (sync) { 5345 tg = task_group(current); 5346 weight = current->se.avg.load_avg; 5347 5348 this_load += effective_load(tg, this_cpu, -weight, -weight); 5349 load += effective_load(tg, prev_cpu, 0, -weight); 5350 } 5351 5352 tg = task_group(p); 5353 weight = p->se.avg.load_avg; 5354 5355 /* 5356 * In low-load situations, where prev_cpu is idle and this_cpu is idle 5357 * due to the sync cause above having dropped this_load to 0, we'll 5358 * always have an imbalance, but there's really nothing you can do 5359 * about that, so that's good too. 5360 * 5361 * Otherwise check if either cpus are near enough in load to allow this 5362 * task to be woken on this_cpu. 5363 */ 5364 this_eff_load = 100; 5365 this_eff_load *= capacity_of(prev_cpu); 5366 5367 prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2; 5368 prev_eff_load *= capacity_of(this_cpu); 5369 5370 if (this_load > 0) { 5371 this_eff_load *= this_load + 5372 effective_load(tg, this_cpu, weight, weight); 5373 5374 prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight); 5375 } 5376 5377 balanced = this_eff_load <= prev_eff_load; 5378 5379 schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts); 5380 5381 if (!balanced) 5382 return 0; 5383 5384 schedstat_inc(sd->ttwu_move_affine); 5385 schedstat_inc(p->se.statistics.nr_wakeups_affine); 5386 5387 return 1; 5388 } 5389 5390 static inline int task_util(struct task_struct *p); 5391 static int cpu_util_wake(int cpu, struct task_struct *p); 5392 5393 static unsigned long capacity_spare_wake(int cpu, struct task_struct *p) 5394 { 5395 return capacity_orig_of(cpu) - cpu_util_wake(cpu, p); 5396 } 5397 5398 /* 5399 * find_idlest_group finds and returns the least busy CPU group within the 5400 * domain. 5401 */ 5402 static struct sched_group * 5403 find_idlest_group(struct sched_domain *sd, struct task_struct *p, 5404 int this_cpu, int sd_flag) 5405 { 5406 struct sched_group *idlest = NULL, *group = sd->groups; 5407 struct sched_group *most_spare_sg = NULL; 5408 unsigned long min_runnable_load = ULONG_MAX, this_runnable_load = 0; 5409 unsigned long min_avg_load = ULONG_MAX, this_avg_load = 0; 5410 unsigned long most_spare = 0, this_spare = 0; 5411 int load_idx = sd->forkexec_idx; 5412 int imbalance_scale = 100 + (sd->imbalance_pct-100)/2; 5413 unsigned long imbalance = scale_load_down(NICE_0_LOAD) * 5414 (sd->imbalance_pct-100) / 100; 5415 5416 if (sd_flag & SD_BALANCE_WAKE) 5417 load_idx = sd->wake_idx; 5418 5419 do { 5420 unsigned long load, avg_load, runnable_load; 5421 unsigned long spare_cap, max_spare_cap; 5422 int local_group; 5423 int i; 5424 5425 /* Skip over this group if it has no CPUs allowed */ 5426 if (!cpumask_intersects(sched_group_cpus(group), 5427 tsk_cpus_allowed(p))) 5428 continue; 5429 5430 local_group = cpumask_test_cpu(this_cpu, 5431 sched_group_cpus(group)); 5432 5433 /* 5434 * Tally up the load of all CPUs in the group and find 5435 * the group containing the CPU with most spare capacity. 5436 */ 5437 avg_load = 0; 5438 runnable_load = 0; 5439 max_spare_cap = 0; 5440 5441 for_each_cpu(i, sched_group_cpus(group)) { 5442 /* Bias balancing toward cpus of our domain */ 5443 if (local_group) 5444 load = source_load(i, load_idx); 5445 else 5446 load = target_load(i, load_idx); 5447 5448 runnable_load += load; 5449 5450 avg_load += cfs_rq_load_avg(&cpu_rq(i)->cfs); 5451 5452 spare_cap = capacity_spare_wake(i, p); 5453 5454 if (spare_cap > max_spare_cap) 5455 max_spare_cap = spare_cap; 5456 } 5457 5458 /* Adjust by relative CPU capacity of the group */ 5459 avg_load = (avg_load * SCHED_CAPACITY_SCALE) / 5460 group->sgc->capacity; 5461 runnable_load = (runnable_load * SCHED_CAPACITY_SCALE) / 5462 group->sgc->capacity; 5463 5464 if (local_group) { 5465 this_runnable_load = runnable_load; 5466 this_avg_load = avg_load; 5467 this_spare = max_spare_cap; 5468 } else { 5469 if (min_runnable_load > (runnable_load + imbalance)) { 5470 /* 5471 * The runnable load is significantly smaller 5472 * so we can pick this new cpu 5473 */ 5474 min_runnable_load = runnable_load; 5475 min_avg_load = avg_load; 5476 idlest = group; 5477 } else if ((runnable_load < (min_runnable_load + imbalance)) && 5478 (100*min_avg_load > imbalance_scale*avg_load)) { 5479 /* 5480 * The runnable loads are close so take the 5481 * blocked load into account through avg_load. 5482 */ 5483 min_avg_load = avg_load; 5484 idlest = group; 5485 } 5486 5487 if (most_spare < max_spare_cap) { 5488 most_spare = max_spare_cap; 5489 most_spare_sg = group; 5490 } 5491 } 5492 } while (group = group->next, group != sd->groups); 5493 5494 /* 5495 * The cross-over point between using spare capacity or least load 5496 * is too conservative for high utilization tasks on partially 5497 * utilized systems if we require spare_capacity > task_util(p), 5498 * so we allow for some task stuffing by using 5499 * spare_capacity > task_util(p)/2. 5500 * 5501 * Spare capacity can't be used for fork because the utilization has 5502 * not been set yet, we must first select a rq to compute the initial 5503 * utilization. 5504 */ 5505 if (sd_flag & SD_BALANCE_FORK) 5506 goto skip_spare; 5507 5508 if (this_spare > task_util(p) / 2 && 5509 imbalance_scale*this_spare > 100*most_spare) 5510 return NULL; 5511 5512 if (most_spare > task_util(p) / 2) 5513 return most_spare_sg; 5514 5515 skip_spare: 5516 if (!idlest) 5517 return NULL; 5518 5519 if (min_runnable_load > (this_runnable_load + imbalance)) 5520 return NULL; 5521 5522 if ((this_runnable_load < (min_runnable_load + imbalance)) && 5523 (100*this_avg_load < imbalance_scale*min_avg_load)) 5524 return NULL; 5525 5526 return idlest; 5527 } 5528 5529 /* 5530 * find_idlest_cpu - find the idlest cpu among the cpus in group. 5531 */ 5532 static int 5533 find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 5534 { 5535 unsigned long load, min_load = ULONG_MAX; 5536 unsigned int min_exit_latency = UINT_MAX; 5537 u64 latest_idle_timestamp = 0; 5538 int least_loaded_cpu = this_cpu; 5539 int shallowest_idle_cpu = -1; 5540 int i; 5541 5542 /* Check if we have any choice: */ 5543 if (group->group_weight == 1) 5544 return cpumask_first(sched_group_cpus(group)); 5545 5546 /* Traverse only the allowed CPUs */ 5547 for_each_cpu_and(i, sched_group_cpus(group), tsk_cpus_allowed(p)) { 5548 if (idle_cpu(i)) { 5549 struct rq *rq = cpu_rq(i); 5550 struct cpuidle_state *idle = idle_get_state(rq); 5551 if (idle && idle->exit_latency < min_exit_latency) { 5552 /* 5553 * We give priority to a CPU whose idle state 5554 * has the smallest exit latency irrespective 5555 * of any idle timestamp. 5556 */ 5557 min_exit_latency = idle->exit_latency; 5558 latest_idle_timestamp = rq->idle_stamp; 5559 shallowest_idle_cpu = i; 5560 } else if ((!idle || idle->exit_latency == min_exit_latency) && 5561 rq->idle_stamp > latest_idle_timestamp) { 5562 /* 5563 * If equal or no active idle state, then 5564 * the most recently idled CPU might have 5565 * a warmer cache. 5566 */ 5567 latest_idle_timestamp = rq->idle_stamp; 5568 shallowest_idle_cpu = i; 5569 } 5570 } else if (shallowest_idle_cpu == -1) { 5571 load = weighted_cpuload(i); 5572 if (load < min_load || (load == min_load && i == this_cpu)) { 5573 min_load = load; 5574 least_loaded_cpu = i; 5575 } 5576 } 5577 } 5578 5579 return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; 5580 } 5581 5582 /* 5583 * Implement a for_each_cpu() variant that starts the scan at a given cpu 5584 * (@start), and wraps around. 5585 * 5586 * This is used to scan for idle CPUs; such that not all CPUs looking for an 5587 * idle CPU find the same CPU. The down-side is that tasks tend to cycle 5588 * through the LLC domain. 5589 * 5590 * Especially tbench is found sensitive to this. 5591 */ 5592 5593 static int cpumask_next_wrap(int n, const struct cpumask *mask, int start, int *wrapped) 5594 { 5595 int next; 5596 5597 again: 5598 next = find_next_bit(cpumask_bits(mask), nr_cpumask_bits, n+1); 5599 5600 if (*wrapped) { 5601 if (next >= start) 5602 return nr_cpumask_bits; 5603 } else { 5604 if (next >= nr_cpumask_bits) { 5605 *wrapped = 1; 5606 n = -1; 5607 goto again; 5608 } 5609 } 5610 5611 return next; 5612 } 5613 5614 #define for_each_cpu_wrap(cpu, mask, start, wrap) \ 5615 for ((wrap) = 0, (cpu) = (start)-1; \ 5616 (cpu) = cpumask_next_wrap((cpu), (mask), (start), &(wrap)), \ 5617 (cpu) < nr_cpumask_bits; ) 5618 5619 #ifdef CONFIG_SCHED_SMT 5620 5621 static inline void set_idle_cores(int cpu, int val) 5622 { 5623 struct sched_domain_shared *sds; 5624 5625 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); 5626 if (sds) 5627 WRITE_ONCE(sds->has_idle_cores, val); 5628 } 5629 5630 static inline bool test_idle_cores(int cpu, bool def) 5631 { 5632 struct sched_domain_shared *sds; 5633 5634 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); 5635 if (sds) 5636 return READ_ONCE(sds->has_idle_cores); 5637 5638 return def; 5639 } 5640 5641 /* 5642 * Scans the local SMT mask to see if the entire core is idle, and records this 5643 * information in sd_llc_shared->has_idle_cores. 5644 * 5645 * Since SMT siblings share all cache levels, inspecting this limited remote 5646 * state should be fairly cheap. 5647 */ 5648 void __update_idle_core(struct rq *rq) 5649 { 5650 int core = cpu_of(rq); 5651 int cpu; 5652 5653 rcu_read_lock(); 5654 if (test_idle_cores(core, true)) 5655 goto unlock; 5656 5657 for_each_cpu(cpu, cpu_smt_mask(core)) { 5658 if (cpu == core) 5659 continue; 5660 5661 if (!idle_cpu(cpu)) 5662 goto unlock; 5663 } 5664 5665 set_idle_cores(core, 1); 5666 unlock: 5667 rcu_read_unlock(); 5668 } 5669 5670 /* 5671 * Scan the entire LLC domain for idle cores; this dynamically switches off if 5672 * there are no idle cores left in the system; tracked through 5673 * sd_llc->shared->has_idle_cores and enabled through update_idle_core() above. 5674 */ 5675 static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) 5676 { 5677 struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask); 5678 int core, cpu, wrap; 5679 5680 if (!static_branch_likely(&sched_smt_present)) 5681 return -1; 5682 5683 if (!test_idle_cores(target, false)) 5684 return -1; 5685 5686 cpumask_and(cpus, sched_domain_span(sd), tsk_cpus_allowed(p)); 5687 5688 for_each_cpu_wrap(core, cpus, target, wrap) { 5689 bool idle = true; 5690 5691 for_each_cpu(cpu, cpu_smt_mask(core)) { 5692 cpumask_clear_cpu(cpu, cpus); 5693 if (!idle_cpu(cpu)) 5694 idle = false; 5695 } 5696 5697 if (idle) 5698 return core; 5699 } 5700 5701 /* 5702 * Failed to find an idle core; stop looking for one. 5703 */ 5704 set_idle_cores(target, 0); 5705 5706 return -1; 5707 } 5708 5709 /* 5710 * Scan the local SMT mask for idle CPUs. 5711 */ 5712 static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target) 5713 { 5714 int cpu; 5715 5716 if (!static_branch_likely(&sched_smt_present)) 5717 return -1; 5718 5719 for_each_cpu(cpu, cpu_smt_mask(target)) { 5720 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) 5721 continue; 5722 if (idle_cpu(cpu)) 5723 return cpu; 5724 } 5725 5726 return -1; 5727 } 5728 5729 #else /* CONFIG_SCHED_SMT */ 5730 5731 static inline int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target) 5732 { 5733 return -1; 5734 } 5735 5736 static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target) 5737 { 5738 return -1; 5739 } 5740 5741 #endif /* CONFIG_SCHED_SMT */ 5742 5743 /* 5744 * Scan the LLC domain for idle CPUs; this is dynamically regulated by 5745 * comparing the average scan cost (tracked in sd->avg_scan_cost) against the 5746 * average idle time for this rq (as found in rq->avg_idle). 5747 */ 5748 static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int target) 5749 { 5750 struct sched_domain *this_sd; 5751 u64 avg_cost, avg_idle = this_rq()->avg_idle; 5752 u64 time, cost; 5753 s64 delta; 5754 int cpu, wrap; 5755 5756 this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc)); 5757 if (!this_sd) 5758 return -1; 5759 5760 avg_cost = this_sd->avg_scan_cost; 5761 5762 /* 5763 * Due to large variance we need a large fuzz factor; hackbench in 5764 * particularly is sensitive here. 5765 */ 5766 if ((avg_idle / 512) < avg_cost) 5767 return -1; 5768 5769 time = local_clock(); 5770 5771 for_each_cpu_wrap(cpu, sched_domain_span(sd), target, wrap) { 5772 if (!cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) 5773 continue; 5774 if (idle_cpu(cpu)) 5775 break; 5776 } 5777 5778 time = local_clock() - time; 5779 cost = this_sd->avg_scan_cost; 5780 delta = (s64)(time - cost) / 8; 5781 this_sd->avg_scan_cost += delta; 5782 5783 return cpu; 5784 } 5785 5786 /* 5787 * Try and locate an idle core/thread in the LLC cache domain. 5788 */ 5789 static int select_idle_sibling(struct task_struct *p, int prev, int target) 5790 { 5791 struct sched_domain *sd; 5792 int i; 5793 5794 if (idle_cpu(target)) 5795 return target; 5796 5797 /* 5798 * If the previous cpu is cache affine and idle, don't be stupid. 5799 */ 5800 if (prev != target && cpus_share_cache(prev, target) && idle_cpu(prev)) 5801 return prev; 5802 5803 sd = rcu_dereference(per_cpu(sd_llc, target)); 5804 if (!sd) 5805 return target; 5806 5807 i = select_idle_core(p, sd, target); 5808 if ((unsigned)i < nr_cpumask_bits) 5809 return i; 5810 5811 i = select_idle_cpu(p, sd, target); 5812 if ((unsigned)i < nr_cpumask_bits) 5813 return i; 5814 5815 i = select_idle_smt(p, sd, target); 5816 if ((unsigned)i < nr_cpumask_bits) 5817 return i; 5818 5819 return target; 5820 } 5821 5822 /* 5823 * cpu_util returns the amount of capacity of a CPU that is used by CFS 5824 * tasks. The unit of the return value must be the one of capacity so we can 5825 * compare the utilization with the capacity of the CPU that is available for 5826 * CFS task (ie cpu_capacity). 5827 * 5828 * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the 5829 * recent utilization of currently non-runnable tasks on a CPU. It represents 5830 * the amount of utilization of a CPU in the range [0..capacity_orig] where 5831 * capacity_orig is the cpu_capacity available at the highest frequency 5832 * (arch_scale_freq_capacity()). 5833 * The utilization of a CPU converges towards a sum equal to or less than the 5834 * current capacity (capacity_curr <= capacity_orig) of the CPU because it is 5835 * the running time on this CPU scaled by capacity_curr. 5836 * 5837 * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even 5838 * higher than capacity_orig because of unfortunate rounding in 5839 * cfs.avg.util_avg or just after migrating tasks and new task wakeups until 5840 * the average stabilizes with the new running time. We need to check that the 5841 * utilization stays within the range of [0..capacity_orig] and cap it if 5842 * necessary. Without utilization capping, a group could be seen as overloaded 5843 * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of 5844 * available capacity. We allow utilization to overshoot capacity_curr (but not 5845 * capacity_orig) as it useful for predicting the capacity required after task 5846 * migrations (scheduler-driven DVFS). 5847 */ 5848 static int cpu_util(int cpu) 5849 { 5850 unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg; 5851 unsigned long capacity = capacity_orig_of(cpu); 5852 5853 return (util >= capacity) ? capacity : util; 5854 } 5855 5856 static inline int task_util(struct task_struct *p) 5857 { 5858 return p->se.avg.util_avg; 5859 } 5860 5861 /* 5862 * cpu_util_wake: Compute cpu utilization with any contributions from 5863 * the waking task p removed. 5864 */ 5865 static int cpu_util_wake(int cpu, struct task_struct *p) 5866 { 5867 unsigned long util, capacity; 5868 5869 /* Task has no contribution or is new */ 5870 if (cpu != task_cpu(p) || !p->se.avg.last_update_time) 5871 return cpu_util(cpu); 5872 5873 capacity = capacity_orig_of(cpu); 5874 util = max_t(long, cpu_rq(cpu)->cfs.avg.util_avg - task_util(p), 0); 5875 5876 return (util >= capacity) ? capacity : util; 5877 } 5878 5879 /* 5880 * Disable WAKE_AFFINE in the case where task @p doesn't fit in the 5881 * capacity of either the waking CPU @cpu or the previous CPU @prev_cpu. 5882 * 5883 * In that case WAKE_AFFINE doesn't make sense and we'll let 5884 * BALANCE_WAKE sort things out. 5885 */ 5886 static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) 5887 { 5888 long min_cap, max_cap; 5889 5890 min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu)); 5891 max_cap = cpu_rq(cpu)->rd->max_cpu_capacity; 5892 5893 /* Minimum capacity is close to max, no need to abort wake_affine */ 5894 if (max_cap - min_cap < max_cap >> 3) 5895 return 0; 5896 5897 /* Bring task utilization in sync with prev_cpu */ 5898 sync_entity_load_avg(&p->se); 5899 5900 return min_cap * 1024 < task_util(p) * capacity_margin; 5901 } 5902 5903 /* 5904 * select_task_rq_fair: Select target runqueue for the waking task in domains 5905 * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, 5906 * SD_BALANCE_FORK, or SD_BALANCE_EXEC. 5907 * 5908 * Balances load by selecting the idlest cpu in the idlest group, or under 5909 * certain conditions an idle sibling cpu if the domain has SD_WAKE_AFFINE set. 5910 * 5911 * Returns the target cpu number. 5912 * 5913 * preempt must be disabled. 5914 */ 5915 static int 5916 select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_flags) 5917 { 5918 struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL; 5919 int cpu = smp_processor_id(); 5920 int new_cpu = prev_cpu; 5921 int want_affine = 0; 5922 int sync = wake_flags & WF_SYNC; 5923 5924 if (sd_flag & SD_BALANCE_WAKE) { 5925 record_wakee(p); 5926 want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) 5927 && cpumask_test_cpu(cpu, tsk_cpus_allowed(p)); 5928 } 5929 5930 rcu_read_lock(); 5931 for_each_domain(cpu, tmp) { 5932 if (!(tmp->flags & SD_LOAD_BALANCE)) 5933 break; 5934 5935 /* 5936 * If both cpu and prev_cpu are part of this domain, 5937 * cpu is a valid SD_WAKE_AFFINE target. 5938 */ 5939 if (want_affine && (tmp->flags & SD_WAKE_AFFINE) && 5940 cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) { 5941 affine_sd = tmp; 5942 break; 5943 } 5944 5945 if (tmp->flags & sd_flag) 5946 sd = tmp; 5947 else if (!want_affine) 5948 break; 5949 } 5950 5951 if (affine_sd) { 5952 sd = NULL; /* Prefer wake_affine over balance flags */ 5953 if (cpu != prev_cpu && wake_affine(affine_sd, p, prev_cpu, sync)) 5954 new_cpu = cpu; 5955 } 5956 5957 if (!sd) { 5958 if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */ 5959 new_cpu = select_idle_sibling(p, prev_cpu, new_cpu); 5960 5961 } else while (sd) { 5962 struct sched_group *group; 5963 int weight; 5964 5965 if (!(sd->flags & sd_flag)) { 5966 sd = sd->child; 5967 continue; 5968 } 5969 5970 group = find_idlest_group(sd, p, cpu, sd_flag); 5971 if (!group) { 5972 sd = sd->child; 5973 continue; 5974 } 5975 5976 new_cpu = find_idlest_cpu(group, p, cpu); 5977 if (new_cpu == -1 || new_cpu == cpu) { 5978 /* Now try balancing at a lower domain level of cpu */ 5979 sd = sd->child; 5980 continue; 5981 } 5982 5983 /* Now try balancing at a lower domain level of new_cpu */ 5984 cpu = new_cpu; 5985 weight = sd->span_weight; 5986 sd = NULL; 5987 for_each_domain(cpu, tmp) { 5988 if (weight <= tmp->span_weight) 5989 break; 5990 if (tmp->flags & sd_flag) 5991 sd = tmp; 5992 } 5993 /* while loop will break here if sd == NULL */ 5994 } 5995 rcu_read_unlock(); 5996 5997 return new_cpu; 5998 } 5999 6000 /* 6001 * Called immediately before a task is migrated to a new cpu; task_cpu(p) and 6002 * cfs_rq_of(p) references at time of call are still valid and identify the 6003 * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held. 6004 */ 6005 static void migrate_task_rq_fair(struct task_struct *p) 6006 { 6007 /* 6008 * As blocked tasks retain absolute vruntime the migration needs to 6009 * deal with this by subtracting the old and adding the new 6010 * min_vruntime -- the latter is done by enqueue_entity() when placing 6011 * the task on the new runqueue. 6012 */ 6013 if (p->state == TASK_WAKING) { 6014 struct sched_entity *se = &p->se; 6015 struct cfs_rq *cfs_rq = cfs_rq_of(se); 6016 u64 min_vruntime; 6017 6018 #ifndef CONFIG_64BIT 6019 u64 min_vruntime_copy; 6020 6021 do { 6022 min_vruntime_copy = cfs_rq->min_vruntime_copy; 6023 smp_rmb(); 6024 min_vruntime = cfs_rq->min_vruntime; 6025 } while (min_vruntime != min_vruntime_copy); 6026 #else 6027 min_vruntime = cfs_rq->min_vruntime; 6028 #endif 6029 6030 se->vruntime -= min_vruntime; 6031 } 6032 6033 /* 6034 * We are supposed to update the task to "current" time, then its up to date 6035 * and ready to go to new CPU/cfs_rq. But we have difficulty in getting 6036 * what current time is, so simply throw away the out-of-date time. This 6037 * will result in the wakee task is less decayed, but giving the wakee more 6038 * load sounds not bad. 6039 */ 6040 remove_entity_load_avg(&p->se); 6041 6042 /* Tell new CPU we are migrated */ 6043 p->se.avg.last_update_time = 0; 6044 6045 /* We have migrated, no longer consider this task hot */ 6046 p->se.exec_start = 0; 6047 } 6048 6049 static void task_dead_fair(struct task_struct *p) 6050 { 6051 remove_entity_load_avg(&p->se); 6052 } 6053 #endif /* CONFIG_SMP */ 6054 6055 static unsigned long 6056 wakeup_gran(struct sched_entity *curr, struct sched_entity *se) 6057 { 6058 unsigned long gran = sysctl_sched_wakeup_granularity; 6059 6060 /* 6061 * Since its curr running now, convert the gran from real-time 6062 * to virtual-time in his units. 6063 * 6064 * By using 'se' instead of 'curr' we penalize light tasks, so 6065 * they get preempted easier. That is, if 'se' < 'curr' then 6066 * the resulting gran will be larger, therefore penalizing the 6067 * lighter, if otoh 'se' > 'curr' then the resulting gran will 6068 * be smaller, again penalizing the lighter task. 6069 * 6070 * This is especially important for buddies when the leftmost 6071 * task is higher priority than the buddy. 6072 */ 6073 return calc_delta_fair(gran, se); 6074 } 6075 6076 /* 6077 * Should 'se' preempt 'curr'. 6078 * 6079 * |s1 6080 * |s2 6081 * |s3 6082 * g 6083 * |<--->|c 6084 * 6085 * w(c, s1) = -1 6086 * w(c, s2) = 0 6087 * w(c, s3) = 1 6088 * 6089 */ 6090 static int 6091 wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se) 6092 { 6093 s64 gran, vdiff = curr->vruntime - se->vruntime; 6094 6095 if (vdiff <= 0) 6096 return -1; 6097 6098 gran = wakeup_gran(curr, se); 6099 if (vdiff > gran) 6100 return 1; 6101 6102 return 0; 6103 } 6104 6105 static void set_last_buddy(struct sched_entity *se) 6106 { 6107 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 6108 return; 6109 6110 for_each_sched_entity(se) 6111 cfs_rq_of(se)->last = se; 6112 } 6113 6114 static void set_next_buddy(struct sched_entity *se) 6115 { 6116 if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE)) 6117 return; 6118 6119 for_each_sched_entity(se) 6120 cfs_rq_of(se)->next = se; 6121 } 6122 6123 static void set_skip_buddy(struct sched_entity *se) 6124 { 6125 for_each_sched_entity(se) 6126 cfs_rq_of(se)->skip = se; 6127 } 6128 6129 /* 6130 * Preempt the current task with a newly woken task if needed: 6131 */ 6132 static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) 6133 { 6134 struct task_struct *curr = rq->curr; 6135 struct sched_entity *se = &curr->se, *pse = &p->se; 6136 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 6137 int scale = cfs_rq->nr_running >= sched_nr_latency; 6138 int next_buddy_marked = 0; 6139 6140 if (unlikely(se == pse)) 6141 return; 6142 6143 /* 6144 * This is possible from callers such as attach_tasks(), in which we 6145 * unconditionally check_prempt_curr() after an enqueue (which may have 6146 * lead to a throttle). This both saves work and prevents false 6147 * next-buddy nomination below. 6148 */ 6149 if (unlikely(throttled_hierarchy(cfs_rq_of(pse)))) 6150 return; 6151 6152 if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK)) { 6153 set_next_buddy(pse); 6154 next_buddy_marked = 1; 6155 } 6156 6157 /* 6158 * We can come here with TIF_NEED_RESCHED already set from new task 6159 * wake up path. 6160 * 6161 * Note: this also catches the edge-case of curr being in a throttled 6162 * group (e.g. via set_curr_task), since update_curr() (in the 6163 * enqueue of curr) will have resulted in resched being set. This 6164 * prevents us from potentially nominating it as a false LAST_BUDDY 6165 * below. 6166 */ 6167 if (test_tsk_need_resched(curr)) 6168 return; 6169 6170 /* Idle tasks are by definition preempted by non-idle tasks. */ 6171 if (unlikely(curr->policy == SCHED_IDLE) && 6172 likely(p->policy != SCHED_IDLE)) 6173 goto preempt; 6174 6175 /* 6176 * Batch and idle tasks do not preempt non-idle tasks (their preemption 6177 * is driven by the tick): 6178 */ 6179 if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION)) 6180 return; 6181 6182 find_matching_se(&se, &pse); 6183 update_curr(cfs_rq_of(se)); 6184 BUG_ON(!pse); 6185 if (wakeup_preempt_entity(se, pse) == 1) { 6186 /* 6187 * Bias pick_next to pick the sched entity that is 6188 * triggering this preemption. 6189 */ 6190 if (!next_buddy_marked) 6191 set_next_buddy(pse); 6192 goto preempt; 6193 } 6194 6195 return; 6196 6197 preempt: 6198 resched_curr(rq); 6199 /* 6200 * Only set the backward buddy when the current task is still 6201 * on the rq. This can happen when a wakeup gets interleaved 6202 * with schedule on the ->pre_schedule() or idle_balance() 6203 * point, either of which can * drop the rq lock. 6204 * 6205 * Also, during early boot the idle thread is in the fair class, 6206 * for obvious reasons its a bad idea to schedule back to it. 6207 */ 6208 if (unlikely(!se->on_rq || curr == rq->idle)) 6209 return; 6210 6211 if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se)) 6212 set_last_buddy(se); 6213 } 6214 6215 static struct task_struct * 6216 pick_next_task_fair(struct rq *rq, struct task_struct *prev, struct pin_cookie cookie) 6217 { 6218 struct cfs_rq *cfs_rq = &rq->cfs; 6219 struct sched_entity *se; 6220 struct task_struct *p; 6221 int new_tasks; 6222 6223 again: 6224 #ifdef CONFIG_FAIR_GROUP_SCHED 6225 if (!cfs_rq->nr_running) 6226 goto idle; 6227 6228 if (prev->sched_class != &fair_sched_class) 6229 goto simple; 6230 6231 /* 6232 * Because of the set_next_buddy() in dequeue_task_fair() it is rather 6233 * likely that a next task is from the same cgroup as the current. 6234 * 6235 * Therefore attempt to avoid putting and setting the entire cgroup 6236 * hierarchy, only change the part that actually changes. 6237 */ 6238 6239 do { 6240 struct sched_entity *curr = cfs_rq->curr; 6241 6242 /* 6243 * Since we got here without doing put_prev_entity() we also 6244 * have to consider cfs_rq->curr. If it is still a runnable 6245 * entity, update_curr() will update its vruntime, otherwise 6246 * forget we've ever seen it. 6247 */ 6248 if (curr) { 6249 if (curr->on_rq) 6250 update_curr(cfs_rq); 6251 else 6252 curr = NULL; 6253 6254 /* 6255 * This call to check_cfs_rq_runtime() will do the 6256 * throttle and dequeue its entity in the parent(s). 6257 * Therefore the 'simple' nr_running test will indeed 6258 * be correct. 6259 */ 6260 if (unlikely(check_cfs_rq_runtime(cfs_rq))) 6261 goto simple; 6262 } 6263 6264 se = pick_next_entity(cfs_rq, curr); 6265 cfs_rq = group_cfs_rq(se); 6266 } while (cfs_rq); 6267 6268 p = task_of(se); 6269 6270 /* 6271 * Since we haven't yet done put_prev_entity and if the selected task 6272 * is a different task than we started out with, try and touch the 6273 * least amount of cfs_rqs. 6274 */ 6275 if (prev != p) { 6276 struct sched_entity *pse = &prev->se; 6277 6278 while (!(cfs_rq = is_same_group(se, pse))) { 6279 int se_depth = se->depth; 6280 int pse_depth = pse->depth; 6281 6282 if (se_depth <= pse_depth) { 6283 put_prev_entity(cfs_rq_of(pse), pse); 6284 pse = parent_entity(pse); 6285 } 6286 if (se_depth >= pse_depth) { 6287 set_next_entity(cfs_rq_of(se), se); 6288 se = parent_entity(se); 6289 } 6290 } 6291 6292 put_prev_entity(cfs_rq, pse); 6293 set_next_entity(cfs_rq, se); 6294 } 6295 6296 if (hrtick_enabled(rq)) 6297 hrtick_start_fair(rq, p); 6298 6299 return p; 6300 simple: 6301 cfs_rq = &rq->cfs; 6302 #endif 6303 6304 if (!cfs_rq->nr_running) 6305 goto idle; 6306 6307 put_prev_task(rq, prev); 6308 6309 do { 6310 se = pick_next_entity(cfs_rq, NULL); 6311 set_next_entity(cfs_rq, se); 6312 cfs_rq = group_cfs_rq(se); 6313 } while (cfs_rq); 6314 6315 p = task_of(se); 6316 6317 if (hrtick_enabled(rq)) 6318 hrtick_start_fair(rq, p); 6319 6320 return p; 6321 6322 idle: 6323 /* 6324 * This is OK, because current is on_cpu, which avoids it being picked 6325 * for load-balance and preemption/IRQs are still disabled avoiding 6326 * further scheduler activity on it and we're being very careful to 6327 * re-start the picking loop. 6328 */ 6329 lockdep_unpin_lock(&rq->lock, cookie); 6330 new_tasks = idle_balance(rq); 6331 lockdep_repin_lock(&rq->lock, cookie); 6332 /* 6333 * Because idle_balance() releases (and re-acquires) rq->lock, it is 6334 * possible for any higher priority task to appear. In that case we 6335 * must re-start the pick_next_entity() loop. 6336 */ 6337 if (new_tasks < 0) 6338 return RETRY_TASK; 6339 6340 if (new_tasks > 0) 6341 goto again; 6342 6343 return NULL; 6344 } 6345 6346 /* 6347 * Account for a descheduled task: 6348 */ 6349 static void put_prev_task_fair(struct rq *rq, struct task_struct *prev) 6350 { 6351 struct sched_entity *se = &prev->se; 6352 struct cfs_rq *cfs_rq; 6353 6354 for_each_sched_entity(se) { 6355 cfs_rq = cfs_rq_of(se); 6356 put_prev_entity(cfs_rq, se); 6357 } 6358 } 6359 6360 /* 6361 * sched_yield() is very simple 6362 * 6363 * The magic of dealing with the ->skip buddy is in pick_next_entity. 6364 */ 6365 static void yield_task_fair(struct rq *rq) 6366 { 6367 struct task_struct *curr = rq->curr; 6368 struct cfs_rq *cfs_rq = task_cfs_rq(curr); 6369 struct sched_entity *se = &curr->se; 6370 6371 /* 6372 * Are we the only task in the tree? 6373 */ 6374 if (unlikely(rq->nr_running == 1)) 6375 return; 6376 6377 clear_buddies(cfs_rq, se); 6378 6379 if (curr->policy != SCHED_BATCH) { 6380 update_rq_clock(rq); 6381 /* 6382 * Update run-time statistics of the 'current'. 6383 */ 6384 update_curr(cfs_rq); 6385 /* 6386 * Tell update_rq_clock() that we've just updated, 6387 * so we don't do microscopic update in schedule() 6388 * and double the fastpath cost. 6389 */ 6390 rq_clock_skip_update(rq, true); 6391 } 6392 6393 set_skip_buddy(se); 6394 } 6395 6396 static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preempt) 6397 { 6398 struct sched_entity *se = &p->se; 6399 6400 /* throttled hierarchies are not runnable */ 6401 if (!se->on_rq || throttled_hierarchy(cfs_rq_of(se))) 6402 return false; 6403 6404 /* Tell the scheduler that we'd really like pse to run next. */ 6405 set_next_buddy(se); 6406 6407 yield_task_fair(rq); 6408 6409 return true; 6410 } 6411 6412 #ifdef CONFIG_SMP 6413 /************************************************** 6414 * Fair scheduling class load-balancing methods. 6415 * 6416 * BASICS 6417 * 6418 * The purpose of load-balancing is to achieve the same basic fairness the 6419 * per-cpu scheduler provides, namely provide a proportional amount of compute 6420 * time to each task. This is expressed in the following equation: 6421 * 6422 * W_i,n/P_i == W_j,n/P_j for all i,j (1) 6423 * 6424 * Where W_i,n is the n-th weight average for cpu i. The instantaneous weight 6425 * W_i,0 is defined as: 6426 * 6427 * W_i,0 = \Sum_j w_i,j (2) 6428 * 6429 * Where w_i,j is the weight of the j-th runnable task on cpu i. This weight 6430 * is derived from the nice value as per sched_prio_to_weight[]. 6431 * 6432 * The weight average is an exponential decay average of the instantaneous 6433 * weight: 6434 * 6435 * W'_i,n = (2^n - 1) / 2^n * W_i,n + 1 / 2^n * W_i,0 (3) 6436 * 6437 * C_i is the compute capacity of cpu i, typically it is the 6438 * fraction of 'recent' time available for SCHED_OTHER task execution. But it 6439 * can also include other factors [XXX]. 6440 * 6441 * To achieve this balance we define a measure of imbalance which follows 6442 * directly from (1): 6443 * 6444 * imb_i,j = max{ avg(W/C), W_i/C_i } - min{ avg(W/C), W_j/C_j } (4) 6445 * 6446 * We them move tasks around to minimize the imbalance. In the continuous 6447 * function space it is obvious this converges, in the discrete case we get 6448 * a few fun cases generally called infeasible weight scenarios. 6449 * 6450 * [XXX expand on: 6451 * - infeasible weights; 6452 * - local vs global optima in the discrete case. ] 6453 * 6454 * 6455 * SCHED DOMAINS 6456 * 6457 * In order to solve the imbalance equation (4), and avoid the obvious O(n^2) 6458 * for all i,j solution, we create a tree of cpus that follows the hardware 6459 * topology where each level pairs two lower groups (or better). This results 6460 * in O(log n) layers. Furthermore we reduce the number of cpus going up the 6461 * tree to only the first of the previous level and we decrease the frequency 6462 * of load-balance at each level inv. proportional to the number of cpus in 6463 * the groups. 6464 * 6465 * This yields: 6466 * 6467 * log_2 n 1 n 6468 * \Sum { --- * --- * 2^i } = O(n) (5) 6469 * i = 0 2^i 2^i 6470 * `- size of each group 6471 * | | `- number of cpus doing load-balance 6472 * | `- freq 6473 * `- sum over all levels 6474 * 6475 * Coupled with a limit on how many tasks we can migrate every balance pass, 6476 * this makes (5) the runtime complexity of the balancer. 6477 * 6478 * An important property here is that each CPU is still (indirectly) connected 6479 * to every other cpu in at most O(log n) steps: 6480 * 6481 * The adjacency matrix of the resulting graph is given by: 6482 * 6483 * log_2 n 6484 * A_i,j = \Union (i % 2^k == 0) && i / 2^(k+1) == j / 2^(k+1) (6) 6485 * k = 0 6486 * 6487 * And you'll find that: 6488 * 6489 * A^(log_2 n)_i,j != 0 for all i,j (7) 6490 * 6491 * Showing there's indeed a path between every cpu in at most O(log n) steps. 6492 * The task movement gives a factor of O(m), giving a convergence complexity 6493 * of: 6494 * 6495 * O(nm log n), n := nr_cpus, m := nr_tasks (8) 6496 * 6497 * 6498 * WORK CONSERVING 6499 * 6500 * In order to avoid CPUs going idle while there's still work to do, new idle 6501 * balancing is more aggressive and has the newly idle cpu iterate up the domain 6502 * tree itself instead of relying on other CPUs to bring it work. 6503 * 6504 * This adds some complexity to both (5) and (8) but it reduces the total idle 6505 * time. 6506 * 6507 * [XXX more?] 6508 * 6509 * 6510 * CGROUPS 6511 * 6512 * Cgroups make a horror show out of (2), instead of a simple sum we get: 6513 * 6514 * s_k,i 6515 * W_i,0 = \Sum_j \Prod_k w_k * ----- (9) 6516 * S_k 6517 * 6518 * Where 6519 * 6520 * s_k,i = \Sum_j w_i,j,k and S_k = \Sum_i s_k,i (10) 6521 * 6522 * w_i,j,k is the weight of the j-th runnable task in the k-th cgroup on cpu i. 6523 * 6524 * The big problem is S_k, its a global sum needed to compute a local (W_i) 6525 * property. 6526 * 6527 * [XXX write more on how we solve this.. _after_ merging pjt's patches that 6528 * rewrite all of this once again.] 6529 */ 6530 6531 static unsigned long __read_mostly max_load_balance_interval = HZ/10; 6532 6533 enum fbq_type { regular, remote, all }; 6534 6535 #define LBF_ALL_PINNED 0x01 6536 #define LBF_NEED_BREAK 0x02 6537 #define LBF_DST_PINNED 0x04 6538 #define LBF_SOME_PINNED 0x08 6539 6540 struct lb_env { 6541 struct sched_domain *sd; 6542 6543 struct rq *src_rq; 6544 int src_cpu; 6545 6546 int dst_cpu; 6547 struct rq *dst_rq; 6548 6549 struct cpumask *dst_grpmask; 6550 int new_dst_cpu; 6551 enum cpu_idle_type idle; 6552 long imbalance; 6553 /* The set of CPUs under consideration for load-balancing */ 6554 struct cpumask *cpus; 6555 6556 unsigned int flags; 6557 6558 unsigned int loop; 6559 unsigned int loop_break; 6560 unsigned int loop_max; 6561 6562 enum fbq_type fbq_type; 6563 struct list_head tasks; 6564 }; 6565 6566 /* 6567 * Is this task likely cache-hot: 6568 */ 6569 static int task_hot(struct task_struct *p, struct lb_env *env) 6570 { 6571 s64 delta; 6572 6573 lockdep_assert_held(&env->src_rq->lock); 6574 6575 if (p->sched_class != &fair_sched_class) 6576 return 0; 6577 6578 if (unlikely(p->policy == SCHED_IDLE)) 6579 return 0; 6580 6581 /* 6582 * Buddy candidates are cache hot: 6583 */ 6584 if (sched_feat(CACHE_HOT_BUDDY) && env->dst_rq->nr_running && 6585 (&p->se == cfs_rq_of(&p->se)->next || 6586 &p->se == cfs_rq_of(&p->se)->last)) 6587 return 1; 6588 6589 if (sysctl_sched_migration_cost == -1) 6590 return 1; 6591 if (sysctl_sched_migration_cost == 0) 6592 return 0; 6593 6594 delta = rq_clock_task(env->src_rq) - p->se.exec_start; 6595 6596 return delta < (s64)sysctl_sched_migration_cost; 6597 } 6598 6599 #ifdef CONFIG_NUMA_BALANCING 6600 /* 6601 * Returns 1, if task migration degrades locality 6602 * Returns 0, if task migration improves locality i.e migration preferred. 6603 * Returns -1, if task migration is not affected by locality. 6604 */ 6605 static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env) 6606 { 6607 struct numa_group *numa_group = rcu_dereference(p->numa_group); 6608 unsigned long src_faults, dst_faults; 6609 int src_nid, dst_nid; 6610 6611 if (!static_branch_likely(&sched_numa_balancing)) 6612 return -1; 6613 6614 if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) 6615 return -1; 6616 6617 src_nid = cpu_to_node(env->src_cpu); 6618 dst_nid = cpu_to_node(env->dst_cpu); 6619 6620 if (src_nid == dst_nid) 6621 return -1; 6622 6623 /* Migrating away from the preferred node is always bad. */ 6624 if (src_nid == p->numa_preferred_nid) { 6625 if (env->src_rq->nr_running > env->src_rq->nr_preferred_running) 6626 return 1; 6627 else 6628 return -1; 6629 } 6630 6631 /* Encourage migration to the preferred node. */ 6632 if (dst_nid == p->numa_preferred_nid) 6633 return 0; 6634 6635 if (numa_group) { 6636 src_faults = group_faults(p, src_nid); 6637 dst_faults = group_faults(p, dst_nid); 6638 } else { 6639 src_faults = task_faults(p, src_nid); 6640 dst_faults = task_faults(p, dst_nid); 6641 } 6642 6643 return dst_faults < src_faults; 6644 } 6645 6646 #else 6647 static inline int migrate_degrades_locality(struct task_struct *p, 6648 struct lb_env *env) 6649 { 6650 return -1; 6651 } 6652 #endif 6653 6654 /* 6655 * can_migrate_task - may task p from runqueue rq be migrated to this_cpu? 6656 */ 6657 static 6658 int can_migrate_task(struct task_struct *p, struct lb_env *env) 6659 { 6660 int tsk_cache_hot; 6661 6662 lockdep_assert_held(&env->src_rq->lock); 6663 6664 /* 6665 * We do not migrate tasks that are: 6666 * 1) throttled_lb_pair, or 6667 * 2) cannot be migrated to this CPU due to cpus_allowed, or 6668 * 3) running (obviously), or 6669 * 4) are cache-hot on their current CPU. 6670 */ 6671 if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) 6672 return 0; 6673 6674 if (!cpumask_test_cpu(env->dst_cpu, tsk_cpus_allowed(p))) { 6675 int cpu; 6676 6677 schedstat_inc(p->se.statistics.nr_failed_migrations_affine); 6678 6679 env->flags |= LBF_SOME_PINNED; 6680 6681 /* 6682 * Remember if this task can be migrated to any other cpu in 6683 * our sched_group. We may want to revisit it if we couldn't 6684 * meet load balance goals by pulling other tasks on src_cpu. 6685 * 6686 * Also avoid computing new_dst_cpu if we have already computed 6687 * one in current iteration. 6688 */ 6689 if (!env->dst_grpmask || (env->flags & LBF_DST_PINNED)) 6690 return 0; 6691 6692 /* Prevent to re-select dst_cpu via env's cpus */ 6693 for_each_cpu_and(cpu, env->dst_grpmask, env->cpus) { 6694 if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) { 6695 env->flags |= LBF_DST_PINNED; 6696 env->new_dst_cpu = cpu; 6697 break; 6698 } 6699 } 6700 6701 return 0; 6702 } 6703 6704 /* Record that we found atleast one task that could run on dst_cpu */ 6705 env->flags &= ~LBF_ALL_PINNED; 6706 6707 if (task_running(env->src_rq, p)) { 6708 schedstat_inc(p->se.statistics.nr_failed_migrations_running); 6709 return 0; 6710 } 6711 6712 /* 6713 * Aggressive migration if: 6714 * 1) destination numa is preferred 6715 * 2) task is cache cold, or 6716 * 3) too many balance attempts have failed. 6717 */ 6718 tsk_cache_hot = migrate_degrades_locality(p, env); 6719 if (tsk_cache_hot == -1) 6720 tsk_cache_hot = task_hot(p, env); 6721 6722 if (tsk_cache_hot <= 0 || 6723 env->sd->nr_balance_failed > env->sd->cache_nice_tries) { 6724 if (tsk_cache_hot == 1) { 6725 schedstat_inc(env->sd->lb_hot_gained[env->idle]); 6726 schedstat_inc(p->se.statistics.nr_forced_migrations); 6727 } 6728 return 1; 6729 } 6730 6731 schedstat_inc(p->se.statistics.nr_failed_migrations_hot); 6732 return 0; 6733 } 6734 6735 /* 6736 * detach_task() -- detach the task for the migration specified in env 6737 */ 6738 static void detach_task(struct task_struct *p, struct lb_env *env) 6739 { 6740 lockdep_assert_held(&env->src_rq->lock); 6741 6742 p->on_rq = TASK_ON_RQ_MIGRATING; 6743 deactivate_task(env->src_rq, p, 0); 6744 set_task_cpu(p, env->dst_cpu); 6745 } 6746 6747 /* 6748 * detach_one_task() -- tries to dequeue exactly one task from env->src_rq, as 6749 * part of active balancing operations within "domain". 6750 * 6751 * Returns a task if successful and NULL otherwise. 6752 */ 6753 static struct task_struct *detach_one_task(struct lb_env *env) 6754 { 6755 struct task_struct *p, *n; 6756 6757 lockdep_assert_held(&env->src_rq->lock); 6758 6759 list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) { 6760 if (!can_migrate_task(p, env)) 6761 continue; 6762 6763 detach_task(p, env); 6764 6765 /* 6766 * Right now, this is only the second place where 6767 * lb_gained[env->idle] is updated (other is detach_tasks) 6768 * so we can safely collect stats here rather than 6769 * inside detach_tasks(). 6770 */ 6771 schedstat_inc(env->sd->lb_gained[env->idle]); 6772 return p; 6773 } 6774 return NULL; 6775 } 6776 6777 static const unsigned int sched_nr_migrate_break = 32; 6778 6779 /* 6780 * detach_tasks() -- tries to detach up to imbalance weighted load from 6781 * busiest_rq, as part of a balancing operation within domain "sd". 6782 * 6783 * Returns number of detached tasks if successful and 0 otherwise. 6784 */ 6785 static int detach_tasks(struct lb_env *env) 6786 { 6787 struct list_head *tasks = &env->src_rq->cfs_tasks; 6788 struct task_struct *p; 6789 unsigned long load; 6790 int detached = 0; 6791 6792 lockdep_assert_held(&env->src_rq->lock); 6793 6794 if (env->imbalance <= 0) 6795 return 0; 6796 6797 while (!list_empty(tasks)) { 6798 /* 6799 * We don't want to steal all, otherwise we may be treated likewise, 6800 * which could at worst lead to a livelock crash. 6801 */ 6802 if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) 6803 break; 6804 6805 p = list_first_entry(tasks, struct task_struct, se.group_node); 6806 6807 env->loop++; 6808 /* We've more or less seen every task there is, call it quits */ 6809 if (env->loop > env->loop_max) 6810 break; 6811 6812 /* take a breather every nr_migrate tasks */ 6813 if (env->loop > env->loop_break) { 6814 env->loop_break += sched_nr_migrate_break; 6815 env->flags |= LBF_NEED_BREAK; 6816 break; 6817 } 6818 6819 if (!can_migrate_task(p, env)) 6820 goto next; 6821 6822 load = task_h_load(p); 6823 6824 if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) 6825 goto next; 6826 6827 if ((load / 2) > env->imbalance) 6828 goto next; 6829 6830 detach_task(p, env); 6831 list_add(&p->se.group_node, &env->tasks); 6832 6833 detached++; 6834 env->imbalance -= load; 6835 6836 #ifdef CONFIG_PREEMPT 6837 /* 6838 * NEWIDLE balancing is a source of latency, so preemptible 6839 * kernels will stop after the first task is detached to minimize 6840 * the critical section. 6841 */ 6842 if (env->idle == CPU_NEWLY_IDLE) 6843 break; 6844 #endif 6845 6846 /* 6847 * We only want to steal up to the prescribed amount of 6848 * weighted load. 6849 */ 6850 if (env->imbalance <= 0) 6851 break; 6852 6853 continue; 6854 next: 6855 list_move_tail(&p->se.group_node, tasks); 6856 } 6857 6858 /* 6859 * Right now, this is one of only two places we collect this stat 6860 * so we can safely collect detach_one_task() stats here rather 6861 * than inside detach_one_task(). 6862 */ 6863 schedstat_add(env->sd->lb_gained[env->idle], detached); 6864 6865 return detached; 6866 } 6867 6868 /* 6869 * attach_task() -- attach the task detached by detach_task() to its new rq. 6870 */ 6871 static void attach_task(struct rq *rq, struct task_struct *p) 6872 { 6873 lockdep_assert_held(&rq->lock); 6874 6875 BUG_ON(task_rq(p) != rq); 6876 activate_task(rq, p, 0); 6877 p->on_rq = TASK_ON_RQ_QUEUED; 6878 check_preempt_curr(rq, p, 0); 6879 } 6880 6881 /* 6882 * attach_one_task() -- attaches the task returned from detach_one_task() to 6883 * its new rq. 6884 */ 6885 static void attach_one_task(struct rq *rq, struct task_struct *p) 6886 { 6887 raw_spin_lock(&rq->lock); 6888 attach_task(rq, p); 6889 raw_spin_unlock(&rq->lock); 6890 } 6891 6892 /* 6893 * attach_tasks() -- attaches all tasks detached by detach_tasks() to their 6894 * new rq. 6895 */ 6896 static void attach_tasks(struct lb_env *env) 6897 { 6898 struct list_head *tasks = &env->tasks; 6899 struct task_struct *p; 6900 6901 raw_spin_lock(&env->dst_rq->lock); 6902 6903 while (!list_empty(tasks)) { 6904 p = list_first_entry(tasks, struct task_struct, se.group_node); 6905 list_del_init(&p->se.group_node); 6906 6907 attach_task(env->dst_rq, p); 6908 } 6909 6910 raw_spin_unlock(&env->dst_rq->lock); 6911 } 6912 6913 #ifdef CONFIG_FAIR_GROUP_SCHED 6914 static void update_blocked_averages(int cpu) 6915 { 6916 struct rq *rq = cpu_rq(cpu); 6917 struct cfs_rq *cfs_rq; 6918 unsigned long flags; 6919 6920 raw_spin_lock_irqsave(&rq->lock, flags); 6921 update_rq_clock(rq); 6922 6923 /* 6924 * Iterates the task_group tree in a bottom up fashion, see 6925 * list_add_leaf_cfs_rq() for details. 6926 */ 6927 for_each_leaf_cfs_rq(rq, cfs_rq) { 6928 /* throttled entities do not contribute to load */ 6929 if (throttled_hierarchy(cfs_rq)) 6930 continue; 6931 6932 if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true)) 6933 update_tg_load_avg(cfs_rq, 0); 6934 6935 /* Propagate pending load changes to the parent */ 6936 if (cfs_rq->tg->se[cpu]) 6937 update_load_avg(cfs_rq->tg->se[cpu], 0); 6938 } 6939 raw_spin_unlock_irqrestore(&rq->lock, flags); 6940 } 6941 6942 /* 6943 * Compute the hierarchical load factor for cfs_rq and all its ascendants. 6944 * This needs to be done in a top-down fashion because the load of a child 6945 * group is a fraction of its parents load. 6946 */ 6947 static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) 6948 { 6949 struct rq *rq = rq_of(cfs_rq); 6950 struct sched_entity *se = cfs_rq->tg->se[cpu_of(rq)]; 6951 unsigned long now = jiffies; 6952 unsigned long load; 6953 6954 if (cfs_rq->last_h_load_update == now) 6955 return; 6956 6957 cfs_rq->h_load_next = NULL; 6958 for_each_sched_entity(se) { 6959 cfs_rq = cfs_rq_of(se); 6960 cfs_rq->h_load_next = se; 6961 if (cfs_rq->last_h_load_update == now) 6962 break; 6963 } 6964 6965 if (!se) { 6966 cfs_rq->h_load = cfs_rq_load_avg(cfs_rq); 6967 cfs_rq->last_h_load_update = now; 6968 } 6969 6970 while ((se = cfs_rq->h_load_next) != NULL) { 6971 load = cfs_rq->h_load; 6972 load = div64_ul(load * se->avg.load_avg, 6973 cfs_rq_load_avg(cfs_rq) + 1); 6974 cfs_rq = group_cfs_rq(se); 6975 cfs_rq->h_load = load; 6976 cfs_rq->last_h_load_update = now; 6977 } 6978 } 6979 6980 static unsigned long task_h_load(struct task_struct *p) 6981 { 6982 struct cfs_rq *cfs_rq = task_cfs_rq(p); 6983 6984 update_cfs_rq_h_load(cfs_rq); 6985 return div64_ul(p->se.avg.load_avg * cfs_rq->h_load, 6986 cfs_rq_load_avg(cfs_rq) + 1); 6987 } 6988 #else 6989 static inline void update_blocked_averages(int cpu) 6990 { 6991 struct rq *rq = cpu_rq(cpu); 6992 struct cfs_rq *cfs_rq = &rq->cfs; 6993 unsigned long flags; 6994 6995 raw_spin_lock_irqsave(&rq->lock, flags); 6996 update_rq_clock(rq); 6997 update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true); 6998 raw_spin_unlock_irqrestore(&rq->lock, flags); 6999 } 7000 7001 static unsigned long task_h_load(struct task_struct *p) 7002 { 7003 return p->se.avg.load_avg; 7004 } 7005 #endif 7006 7007 /********** Helpers for find_busiest_group ************************/ 7008 7009 enum group_type { 7010 group_other = 0, 7011 group_imbalanced, 7012 group_overloaded, 7013 }; 7014 7015 /* 7016 * sg_lb_stats - stats of a sched_group required for load_balancing 7017 */ 7018 struct sg_lb_stats { 7019 unsigned long avg_load; /*Avg load across the CPUs of the group */ 7020 unsigned long group_load; /* Total load over the CPUs of the group */ 7021 unsigned long sum_weighted_load; /* Weighted load of group's tasks */ 7022 unsigned long load_per_task; 7023 unsigned long group_capacity; 7024 unsigned long group_util; /* Total utilization of the group */ 7025 unsigned int sum_nr_running; /* Nr tasks running in the group */ 7026 unsigned int idle_cpus; 7027 unsigned int group_weight; 7028 enum group_type group_type; 7029 int group_no_capacity; 7030 #ifdef CONFIG_NUMA_BALANCING 7031 unsigned int nr_numa_running; 7032 unsigned int nr_preferred_running; 7033 #endif 7034 }; 7035 7036 /* 7037 * sd_lb_stats - Structure to store the statistics of a sched_domain 7038 * during load balancing. 7039 */ 7040 struct sd_lb_stats { 7041 struct sched_group *busiest; /* Busiest group in this sd */ 7042 struct sched_group *local; /* Local group in this sd */ 7043 unsigned long total_load; /* Total load of all groups in sd */ 7044 unsigned long total_capacity; /* Total capacity of all groups in sd */ 7045 unsigned long avg_load; /* Average load across all groups in sd */ 7046 7047 struct sg_lb_stats busiest_stat;/* Statistics of the busiest group */ 7048 struct sg_lb_stats local_stat; /* Statistics of the local group */ 7049 }; 7050 7051 static inline void init_sd_lb_stats(struct sd_lb_stats *sds) 7052 { 7053 /* 7054 * Skimp on the clearing to avoid duplicate work. We can avoid clearing 7055 * local_stat because update_sg_lb_stats() does a full clear/assignment. 7056 * We must however clear busiest_stat::avg_load because 7057 * update_sd_pick_busiest() reads this before assignment. 7058 */ 7059 *sds = (struct sd_lb_stats){ 7060 .busiest = NULL, 7061 .local = NULL, 7062 .total_load = 0UL, 7063 .total_capacity = 0UL, 7064 .busiest_stat = { 7065 .avg_load = 0UL, 7066 .sum_nr_running = 0, 7067 .group_type = group_other, 7068 }, 7069 }; 7070 } 7071 7072 /** 7073 * get_sd_load_idx - Obtain the load index for a given sched domain. 7074 * @sd: The sched_domain whose load_idx is to be obtained. 7075 * @idle: The idle status of the CPU for whose sd load_idx is obtained. 7076 * 7077 * Return: The load index. 7078 */ 7079 static inline int get_sd_load_idx(struct sched_domain *sd, 7080 enum cpu_idle_type idle) 7081 { 7082 int load_idx; 7083 7084 switch (idle) { 7085 case CPU_NOT_IDLE: 7086 load_idx = sd->busy_idx; 7087 break; 7088 7089 case CPU_NEWLY_IDLE: 7090 load_idx = sd->newidle_idx; 7091 break; 7092 default: 7093 load_idx = sd->idle_idx; 7094 break; 7095 } 7096 7097 return load_idx; 7098 } 7099 7100 static unsigned long scale_rt_capacity(int cpu) 7101 { 7102 struct rq *rq = cpu_rq(cpu); 7103 u64 total, used, age_stamp, avg; 7104 s64 delta; 7105 7106 /* 7107 * Since we're reading these variables without serialization make sure 7108 * we read them once before doing sanity checks on them. 7109 */ 7110 age_stamp = READ_ONCE(rq->age_stamp); 7111 avg = READ_ONCE(rq->rt_avg); 7112 delta = __rq_clock_broken(rq) - age_stamp; 7113 7114 if (unlikely(delta < 0)) 7115 delta = 0; 7116 7117 total = sched_avg_period() + delta; 7118 7119 used = div_u64(avg, total); 7120 7121 if (likely(used < SCHED_CAPACITY_SCALE)) 7122 return SCHED_CAPACITY_SCALE - used; 7123 7124 return 1; 7125 } 7126 7127 static void update_cpu_capacity(struct sched_domain *sd, int cpu) 7128 { 7129 unsigned long capacity = arch_scale_cpu_capacity(sd, cpu); 7130 struct sched_group *sdg = sd->groups; 7131 7132 cpu_rq(cpu)->cpu_capacity_orig = capacity; 7133 7134 capacity *= scale_rt_capacity(cpu); 7135 capacity >>= SCHED_CAPACITY_SHIFT; 7136 7137 if (!capacity) 7138 capacity = 1; 7139 7140 cpu_rq(cpu)->cpu_capacity = capacity; 7141 sdg->sgc->capacity = capacity; 7142 sdg->sgc->min_capacity = capacity; 7143 } 7144 7145 void update_group_capacity(struct sched_domain *sd, int cpu) 7146 { 7147 struct sched_domain *child = sd->child; 7148 struct sched_group *group, *sdg = sd->groups; 7149 unsigned long capacity, min_capacity; 7150 unsigned long interval; 7151 7152 interval = msecs_to_jiffies(sd->balance_interval); 7153 interval = clamp(interval, 1UL, max_load_balance_interval); 7154 sdg->sgc->next_update = jiffies + interval; 7155 7156 if (!child) { 7157 update_cpu_capacity(sd, cpu); 7158 return; 7159 } 7160 7161 capacity = 0; 7162 min_capacity = ULONG_MAX; 7163 7164 if (child->flags & SD_OVERLAP) { 7165 /* 7166 * SD_OVERLAP domains cannot assume that child groups 7167 * span the current group. 7168 */ 7169 7170 for_each_cpu(cpu, sched_group_cpus(sdg)) { 7171 struct sched_group_capacity *sgc; 7172 struct rq *rq = cpu_rq(cpu); 7173 7174 /* 7175 * build_sched_domains() -> init_sched_groups_capacity() 7176 * gets here before we've attached the domains to the 7177 * runqueues. 7178 * 7179 * Use capacity_of(), which is set irrespective of domains 7180 * in update_cpu_capacity(). 7181 * 7182 * This avoids capacity from being 0 and 7183 * causing divide-by-zero issues on boot. 7184 */ 7185 if (unlikely(!rq->sd)) { 7186 capacity += capacity_of(cpu); 7187 } else { 7188 sgc = rq->sd->groups->sgc; 7189 capacity += sgc->capacity; 7190 } 7191 7192 min_capacity = min(capacity, min_capacity); 7193 } 7194 } else { 7195 /* 7196 * !SD_OVERLAP domains can assume that child groups 7197 * span the current group. 7198 */ 7199 7200 group = child->groups; 7201 do { 7202 struct sched_group_capacity *sgc = group->sgc; 7203 7204 capacity += sgc->capacity; 7205 min_capacity = min(sgc->min_capacity, min_capacity); 7206 group = group->next; 7207 } while (group != child->groups); 7208 } 7209 7210 sdg->sgc->capacity = capacity; 7211 sdg->sgc->min_capacity = min_capacity; 7212 } 7213 7214 /* 7215 * Check whether the capacity of the rq has been noticeably reduced by side 7216 * activity. The imbalance_pct is used for the threshold. 7217 * Return true is the capacity is reduced 7218 */ 7219 static inline int 7220 check_cpu_capacity(struct rq *rq, struct sched_domain *sd) 7221 { 7222 return ((rq->cpu_capacity * sd->imbalance_pct) < 7223 (rq->cpu_capacity_orig * 100)); 7224 } 7225 7226 /* 7227 * Group imbalance indicates (and tries to solve) the problem where balancing 7228 * groups is inadequate due to tsk_cpus_allowed() constraints. 7229 * 7230 * Imagine a situation of two groups of 4 cpus each and 4 tasks each with a 7231 * cpumask covering 1 cpu of the first group and 3 cpus of the second group. 7232 * Something like: 7233 * 7234 * { 0 1 2 3 } { 4 5 6 7 } 7235 * * * * * 7236 * 7237 * If we were to balance group-wise we'd place two tasks in the first group and 7238 * two tasks in the second group. Clearly this is undesired as it will overload 7239 * cpu 3 and leave one of the cpus in the second group unused. 7240 * 7241 * The current solution to this issue is detecting the skew in the first group 7242 * by noticing the lower domain failed to reach balance and had difficulty 7243 * moving tasks due to affinity constraints. 7244 * 7245 * When this is so detected; this group becomes a candidate for busiest; see 7246 * update_sd_pick_busiest(). And calculate_imbalance() and 7247 * find_busiest_group() avoid some of the usual balance conditions to allow it 7248 * to create an effective group imbalance. 7249 * 7250 * This is a somewhat tricky proposition since the next run might not find the 7251 * group imbalance and decide the groups need to be balanced again. A most 7252 * subtle and fragile situation. 7253 */ 7254 7255 static inline int sg_imbalanced(struct sched_group *group) 7256 { 7257 return group->sgc->imbalance; 7258 } 7259 7260 /* 7261 * group_has_capacity returns true if the group has spare capacity that could 7262 * be used by some tasks. 7263 * We consider that a group has spare capacity if the * number of task is 7264 * smaller than the number of CPUs or if the utilization is lower than the 7265 * available capacity for CFS tasks. 7266 * For the latter, we use a threshold to stabilize the state, to take into 7267 * account the variance of the tasks' load and to return true if the available 7268 * capacity in meaningful for the load balancer. 7269 * As an example, an available capacity of 1% can appear but it doesn't make 7270 * any benefit for the load balance. 7271 */ 7272 static inline bool 7273 group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs) 7274 { 7275 if (sgs->sum_nr_running < sgs->group_weight) 7276 return true; 7277 7278 if ((sgs->group_capacity * 100) > 7279 (sgs->group_util * env->sd->imbalance_pct)) 7280 return true; 7281 7282 return false; 7283 } 7284 7285 /* 7286 * group_is_overloaded returns true if the group has more tasks than it can 7287 * handle. 7288 * group_is_overloaded is not equals to !group_has_capacity because a group 7289 * with the exact right number of tasks, has no more spare capacity but is not 7290 * overloaded so both group_has_capacity and group_is_overloaded return 7291 * false. 7292 */ 7293 static inline bool 7294 group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs) 7295 { 7296 if (sgs->sum_nr_running <= sgs->group_weight) 7297 return false; 7298 7299 if ((sgs->group_capacity * 100) < 7300 (sgs->group_util * env->sd->imbalance_pct)) 7301 return true; 7302 7303 return false; 7304 } 7305 7306 /* 7307 * group_smaller_cpu_capacity: Returns true if sched_group sg has smaller 7308 * per-CPU capacity than sched_group ref. 7309 */ 7310 static inline bool 7311 group_smaller_cpu_capacity(struct sched_group *sg, struct sched_group *ref) 7312 { 7313 return sg->sgc->min_capacity * capacity_margin < 7314 ref->sgc->min_capacity * 1024; 7315 } 7316 7317 static inline enum 7318 group_type group_classify(struct sched_group *group, 7319 struct sg_lb_stats *sgs) 7320 { 7321 if (sgs->group_no_capacity) 7322 return group_overloaded; 7323 7324 if (sg_imbalanced(group)) 7325 return group_imbalanced; 7326 7327 return group_other; 7328 } 7329 7330 /** 7331 * update_sg_lb_stats - Update sched_group's statistics for load balancing. 7332 * @env: The load balancing environment. 7333 * @group: sched_group whose statistics are to be updated. 7334 * @load_idx: Load index of sched_domain of this_cpu for load calc. 7335 * @local_group: Does group contain this_cpu. 7336 * @sgs: variable to hold the statistics for this group. 7337 * @overload: Indicate more than one runnable task for any CPU. 7338 */ 7339 static inline void update_sg_lb_stats(struct lb_env *env, 7340 struct sched_group *group, int load_idx, 7341 int local_group, struct sg_lb_stats *sgs, 7342 bool *overload) 7343 { 7344 unsigned long load; 7345 int i, nr_running; 7346 7347 memset(sgs, 0, sizeof(*sgs)); 7348 7349 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 7350 struct rq *rq = cpu_rq(i); 7351 7352 /* Bias balancing toward cpus of our domain */ 7353 if (local_group) 7354 load = target_load(i, load_idx); 7355 else 7356 load = source_load(i, load_idx); 7357 7358 sgs->group_load += load; 7359 sgs->group_util += cpu_util(i); 7360 sgs->sum_nr_running += rq->cfs.h_nr_running; 7361 7362 nr_running = rq->nr_running; 7363 if (nr_running > 1) 7364 *overload = true; 7365 7366 #ifdef CONFIG_NUMA_BALANCING 7367 sgs->nr_numa_running += rq->nr_numa_running; 7368 sgs->nr_preferred_running += rq->nr_preferred_running; 7369 #endif 7370 sgs->sum_weighted_load += weighted_cpuload(i); 7371 /* 7372 * No need to call idle_cpu() if nr_running is not 0 7373 */ 7374 if (!nr_running && idle_cpu(i)) 7375 sgs->idle_cpus++; 7376 } 7377 7378 /* Adjust by relative CPU capacity of the group */ 7379 sgs->group_capacity = group->sgc->capacity; 7380 sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity; 7381 7382 if (sgs->sum_nr_running) 7383 sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running; 7384 7385 sgs->group_weight = group->group_weight; 7386 7387 sgs->group_no_capacity = group_is_overloaded(env, sgs); 7388 sgs->group_type = group_classify(group, sgs); 7389 } 7390 7391 /** 7392 * update_sd_pick_busiest - return 1 on busiest group 7393 * @env: The load balancing environment. 7394 * @sds: sched_domain statistics 7395 * @sg: sched_group candidate to be checked for being the busiest 7396 * @sgs: sched_group statistics 7397 * 7398 * Determine if @sg is a busier group than the previously selected 7399 * busiest group. 7400 * 7401 * Return: %true if @sg is a busier group than the previously selected 7402 * busiest group. %false otherwise. 7403 */ 7404 static bool update_sd_pick_busiest(struct lb_env *env, 7405 struct sd_lb_stats *sds, 7406 struct sched_group *sg, 7407 struct sg_lb_stats *sgs) 7408 { 7409 struct sg_lb_stats *busiest = &sds->busiest_stat; 7410 7411 if (sgs->group_type > busiest->group_type) 7412 return true; 7413 7414 if (sgs->group_type < busiest->group_type) 7415 return false; 7416 7417 if (sgs->avg_load <= busiest->avg_load) 7418 return false; 7419 7420 if (!(env->sd->flags & SD_ASYM_CPUCAPACITY)) 7421 goto asym_packing; 7422 7423 /* 7424 * Candidate sg has no more than one task per CPU and 7425 * has higher per-CPU capacity. Migrating tasks to less 7426 * capable CPUs may harm throughput. Maximize throughput, 7427 * power/energy consequences are not considered. 7428 */ 7429 if (sgs->sum_nr_running <= sgs->group_weight && 7430 group_smaller_cpu_capacity(sds->local, sg)) 7431 return false; 7432 7433 asym_packing: 7434 /* This is the busiest node in its class. */ 7435 if (!(env->sd->flags & SD_ASYM_PACKING)) 7436 return true; 7437 7438 /* No ASYM_PACKING if target cpu is already busy */ 7439 if (env->idle == CPU_NOT_IDLE) 7440 return true; 7441 /* 7442 * ASYM_PACKING needs to move all the work to the highest 7443 * prority CPUs in the group, therefore mark all groups 7444 * of lower priority than ourself as busy. 7445 */ 7446 if (sgs->sum_nr_running && 7447 sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) { 7448 if (!sds->busiest) 7449 return true; 7450 7451 /* Prefer to move from lowest priority cpu's work */ 7452 if (sched_asym_prefer(sds->busiest->asym_prefer_cpu, 7453 sg->asym_prefer_cpu)) 7454 return true; 7455 } 7456 7457 return false; 7458 } 7459 7460 #ifdef CONFIG_NUMA_BALANCING 7461 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 7462 { 7463 if (sgs->sum_nr_running > sgs->nr_numa_running) 7464 return regular; 7465 if (sgs->sum_nr_running > sgs->nr_preferred_running) 7466 return remote; 7467 return all; 7468 } 7469 7470 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 7471 { 7472 if (rq->nr_running > rq->nr_numa_running) 7473 return regular; 7474 if (rq->nr_running > rq->nr_preferred_running) 7475 return remote; 7476 return all; 7477 } 7478 #else 7479 static inline enum fbq_type fbq_classify_group(struct sg_lb_stats *sgs) 7480 { 7481 return all; 7482 } 7483 7484 static inline enum fbq_type fbq_classify_rq(struct rq *rq) 7485 { 7486 return regular; 7487 } 7488 #endif /* CONFIG_NUMA_BALANCING */ 7489 7490 /** 7491 * update_sd_lb_stats - Update sched_domain's statistics for load balancing. 7492 * @env: The load balancing environment. 7493 * @sds: variable to hold the statistics for this sched_domain. 7494 */ 7495 static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) 7496 { 7497 struct sched_domain *child = env->sd->child; 7498 struct sched_group *sg = env->sd->groups; 7499 struct sg_lb_stats tmp_sgs; 7500 int load_idx, prefer_sibling = 0; 7501 bool overload = false; 7502 7503 if (child && child->flags & SD_PREFER_SIBLING) 7504 prefer_sibling = 1; 7505 7506 load_idx = get_sd_load_idx(env->sd, env->idle); 7507 7508 do { 7509 struct sg_lb_stats *sgs = &tmp_sgs; 7510 int local_group; 7511 7512 local_group = cpumask_test_cpu(env->dst_cpu, sched_group_cpus(sg)); 7513 if (local_group) { 7514 sds->local = sg; 7515 sgs = &sds->local_stat; 7516 7517 if (env->idle != CPU_NEWLY_IDLE || 7518 time_after_eq(jiffies, sg->sgc->next_update)) 7519 update_group_capacity(env->sd, env->dst_cpu); 7520 } 7521 7522 update_sg_lb_stats(env, sg, load_idx, local_group, sgs, 7523 &overload); 7524 7525 if (local_group) 7526 goto next_group; 7527 7528 /* 7529 * In case the child domain prefers tasks go to siblings 7530 * first, lower the sg capacity so that we'll try 7531 * and move all the excess tasks away. We lower the capacity 7532 * of a group only if the local group has the capacity to fit 7533 * these excess tasks. The extra check prevents the case where 7534 * you always pull from the heaviest group when it is already 7535 * under-utilized (possible with a large weight task outweighs 7536 * the tasks on the system). 7537 */ 7538 if (prefer_sibling && sds->local && 7539 group_has_capacity(env, &sds->local_stat) && 7540 (sgs->sum_nr_running > 1)) { 7541 sgs->group_no_capacity = 1; 7542 sgs->group_type = group_classify(sg, sgs); 7543 } 7544 7545 if (update_sd_pick_busiest(env, sds, sg, sgs)) { 7546 sds->busiest = sg; 7547 sds->busiest_stat = *sgs; 7548 } 7549 7550 next_group: 7551 /* Now, start updating sd_lb_stats */ 7552 sds->total_load += sgs->group_load; 7553 sds->total_capacity += sgs->group_capacity; 7554 7555 sg = sg->next; 7556 } while (sg != env->sd->groups); 7557 7558 if (env->sd->flags & SD_NUMA) 7559 env->fbq_type = fbq_classify_group(&sds->busiest_stat); 7560 7561 if (!env->sd->parent) { 7562 /* update overload indicator if we are at root domain */ 7563 if (env->dst_rq->rd->overload != overload) 7564 env->dst_rq->rd->overload = overload; 7565 } 7566 7567 } 7568 7569 /** 7570 * check_asym_packing - Check to see if the group is packed into the 7571 * sched doman. 7572 * 7573 * This is primarily intended to used at the sibling level. Some 7574 * cores like POWER7 prefer to use lower numbered SMT threads. In the 7575 * case of POWER7, it can move to lower SMT modes only when higher 7576 * threads are idle. When in lower SMT modes, the threads will 7577 * perform better since they share less core resources. Hence when we 7578 * have idle threads, we want them to be the higher ones. 7579 * 7580 * This packing function is run on idle threads. It checks to see if 7581 * the busiest CPU in this domain (core in the P7 case) has a higher 7582 * CPU number than the packing function is being run on. Here we are 7583 * assuming lower CPU number will be equivalent to lower a SMT thread 7584 * number. 7585 * 7586 * Return: 1 when packing is required and a task should be moved to 7587 * this CPU. The amount of the imbalance is returned in *imbalance. 7588 * 7589 * @env: The load balancing environment. 7590 * @sds: Statistics of the sched_domain which is to be packed 7591 */ 7592 static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) 7593 { 7594 int busiest_cpu; 7595 7596 if (!(env->sd->flags & SD_ASYM_PACKING)) 7597 return 0; 7598 7599 if (env->idle == CPU_NOT_IDLE) 7600 return 0; 7601 7602 if (!sds->busiest) 7603 return 0; 7604 7605 busiest_cpu = sds->busiest->asym_prefer_cpu; 7606 if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) 7607 return 0; 7608 7609 env->imbalance = DIV_ROUND_CLOSEST( 7610 sds->busiest_stat.avg_load * sds->busiest_stat.group_capacity, 7611 SCHED_CAPACITY_SCALE); 7612 7613 return 1; 7614 } 7615 7616 /** 7617 * fix_small_imbalance - Calculate the minor imbalance that exists 7618 * amongst the groups of a sched_domain, during 7619 * load balancing. 7620 * @env: The load balancing environment. 7621 * @sds: Statistics of the sched_domain whose imbalance is to be calculated. 7622 */ 7623 static inline 7624 void fix_small_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 7625 { 7626 unsigned long tmp, capa_now = 0, capa_move = 0; 7627 unsigned int imbn = 2; 7628 unsigned long scaled_busy_load_per_task; 7629 struct sg_lb_stats *local, *busiest; 7630 7631 local = &sds->local_stat; 7632 busiest = &sds->busiest_stat; 7633 7634 if (!local->sum_nr_running) 7635 local->load_per_task = cpu_avg_load_per_task(env->dst_cpu); 7636 else if (busiest->load_per_task > local->load_per_task) 7637 imbn = 1; 7638 7639 scaled_busy_load_per_task = 7640 (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 7641 busiest->group_capacity; 7642 7643 if (busiest->avg_load + scaled_busy_load_per_task >= 7644 local->avg_load + (scaled_busy_load_per_task * imbn)) { 7645 env->imbalance = busiest->load_per_task; 7646 return; 7647 } 7648 7649 /* 7650 * OK, we don't have enough imbalance to justify moving tasks, 7651 * however we may be able to increase total CPU capacity used by 7652 * moving them. 7653 */ 7654 7655 capa_now += busiest->group_capacity * 7656 min(busiest->load_per_task, busiest->avg_load); 7657 capa_now += local->group_capacity * 7658 min(local->load_per_task, local->avg_load); 7659 capa_now /= SCHED_CAPACITY_SCALE; 7660 7661 /* Amount of load we'd subtract */ 7662 if (busiest->avg_load > scaled_busy_load_per_task) { 7663 capa_move += busiest->group_capacity * 7664 min(busiest->load_per_task, 7665 busiest->avg_load - scaled_busy_load_per_task); 7666 } 7667 7668 /* Amount of load we'd add */ 7669 if (busiest->avg_load * busiest->group_capacity < 7670 busiest->load_per_task * SCHED_CAPACITY_SCALE) { 7671 tmp = (busiest->avg_load * busiest->group_capacity) / 7672 local->group_capacity; 7673 } else { 7674 tmp = (busiest->load_per_task * SCHED_CAPACITY_SCALE) / 7675 local->group_capacity; 7676 } 7677 capa_move += local->group_capacity * 7678 min(local->load_per_task, local->avg_load + tmp); 7679 capa_move /= SCHED_CAPACITY_SCALE; 7680 7681 /* Move if we gain throughput */ 7682 if (capa_move > capa_now) 7683 env->imbalance = busiest->load_per_task; 7684 } 7685 7686 /** 7687 * calculate_imbalance - Calculate the amount of imbalance present within the 7688 * groups of a given sched_domain during load balance. 7689 * @env: load balance environment 7690 * @sds: statistics of the sched_domain whose imbalance is to be calculated. 7691 */ 7692 static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *sds) 7693 { 7694 unsigned long max_pull, load_above_capacity = ~0UL; 7695 struct sg_lb_stats *local, *busiest; 7696 7697 local = &sds->local_stat; 7698 busiest = &sds->busiest_stat; 7699 7700 if (busiest->group_type == group_imbalanced) { 7701 /* 7702 * In the group_imb case we cannot rely on group-wide averages 7703 * to ensure cpu-load equilibrium, look at wider averages. XXX 7704 */ 7705 busiest->load_per_task = 7706 min(busiest->load_per_task, sds->avg_load); 7707 } 7708 7709 /* 7710 * Avg load of busiest sg can be less and avg load of local sg can 7711 * be greater than avg load across all sgs of sd because avg load 7712 * factors in sg capacity and sgs with smaller group_type are 7713 * skipped when updating the busiest sg: 7714 */ 7715 if (busiest->avg_load <= sds->avg_load || 7716 local->avg_load >= sds->avg_load) { 7717 env->imbalance = 0; 7718 return fix_small_imbalance(env, sds); 7719 } 7720 7721 /* 7722 * If there aren't any idle cpus, avoid creating some. 7723 */ 7724 if (busiest->group_type == group_overloaded && 7725 local->group_type == group_overloaded) { 7726 load_above_capacity = busiest->sum_nr_running * SCHED_CAPACITY_SCALE; 7727 if (load_above_capacity > busiest->group_capacity) { 7728 load_above_capacity -= busiest->group_capacity; 7729 load_above_capacity *= scale_load_down(NICE_0_LOAD); 7730 load_above_capacity /= busiest->group_capacity; 7731 } else 7732 load_above_capacity = ~0UL; 7733 } 7734 7735 /* 7736 * We're trying to get all the cpus to the average_load, so we don't 7737 * want to push ourselves above the average load, nor do we wish to 7738 * reduce the max loaded cpu below the average load. At the same time, 7739 * we also don't want to reduce the group load below the group 7740 * capacity. Thus we look for the minimum possible imbalance. 7741 */ 7742 max_pull = min(busiest->avg_load - sds->avg_load, load_above_capacity); 7743 7744 /* How much load to actually move to equalise the imbalance */ 7745 env->imbalance = min( 7746 max_pull * busiest->group_capacity, 7747 (sds->avg_load - local->avg_load) * local->group_capacity 7748 ) / SCHED_CAPACITY_SCALE; 7749 7750 /* 7751 * if *imbalance is less than the average load per runnable task 7752 * there is no guarantee that any tasks will be moved so we'll have 7753 * a think about bumping its value to force at least one task to be 7754 * moved 7755 */ 7756 if (env->imbalance < busiest->load_per_task) 7757 return fix_small_imbalance(env, sds); 7758 } 7759 7760 /******* find_busiest_group() helpers end here *********************/ 7761 7762 /** 7763 * find_busiest_group - Returns the busiest group within the sched_domain 7764 * if there is an imbalance. 7765 * 7766 * Also calculates the amount of weighted load which should be moved 7767 * to restore balance. 7768 * 7769 * @env: The load balancing environment. 7770 * 7771 * Return: - The busiest group if imbalance exists. 7772 */ 7773 static struct sched_group *find_busiest_group(struct lb_env *env) 7774 { 7775 struct sg_lb_stats *local, *busiest; 7776 struct sd_lb_stats sds; 7777 7778 init_sd_lb_stats(&sds); 7779 7780 /* 7781 * Compute the various statistics relavent for load balancing at 7782 * this level. 7783 */ 7784 update_sd_lb_stats(env, &sds); 7785 local = &sds.local_stat; 7786 busiest = &sds.busiest_stat; 7787 7788 /* ASYM feature bypasses nice load balance check */ 7789 if (check_asym_packing(env, &sds)) 7790 return sds.busiest; 7791 7792 /* There is no busy sibling group to pull tasks from */ 7793 if (!sds.busiest || busiest->sum_nr_running == 0) 7794 goto out_balanced; 7795 7796 sds.avg_load = (SCHED_CAPACITY_SCALE * sds.total_load) 7797 / sds.total_capacity; 7798 7799 /* 7800 * If the busiest group is imbalanced the below checks don't 7801 * work because they assume all things are equal, which typically 7802 * isn't true due to cpus_allowed constraints and the like. 7803 */ 7804 if (busiest->group_type == group_imbalanced) 7805 goto force_balance; 7806 7807 /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */ 7808 if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) && 7809 busiest->group_no_capacity) 7810 goto force_balance; 7811 7812 /* 7813 * If the local group is busier than the selected busiest group 7814 * don't try and pull any tasks. 7815 */ 7816 if (local->avg_load >= busiest->avg_load) 7817 goto out_balanced; 7818 7819 /* 7820 * Don't pull any tasks if this group is already above the domain 7821 * average load. 7822 */ 7823 if (local->avg_load >= sds.avg_load) 7824 goto out_balanced; 7825 7826 if (env->idle == CPU_IDLE) { 7827 /* 7828 * This cpu is idle. If the busiest group is not overloaded 7829 * and there is no imbalance between this and busiest group 7830 * wrt idle cpus, it is balanced. The imbalance becomes 7831 * significant if the diff is greater than 1 otherwise we 7832 * might end up to just move the imbalance on another group 7833 */ 7834 if ((busiest->group_type != group_overloaded) && 7835 (local->idle_cpus <= (busiest->idle_cpus + 1))) 7836 goto out_balanced; 7837 } else { 7838 /* 7839 * In the CPU_NEWLY_IDLE, CPU_NOT_IDLE cases, use 7840 * imbalance_pct to be conservative. 7841 */ 7842 if (100 * busiest->avg_load <= 7843 env->sd->imbalance_pct * local->avg_load) 7844 goto out_balanced; 7845 } 7846 7847 force_balance: 7848 /* Looks like there is an imbalance. Compute it */ 7849 calculate_imbalance(env, &sds); 7850 return sds.busiest; 7851 7852 out_balanced: 7853 env->imbalance = 0; 7854 return NULL; 7855 } 7856 7857 /* 7858 * find_busiest_queue - find the busiest runqueue among the cpus in group. 7859 */ 7860 static struct rq *find_busiest_queue(struct lb_env *env, 7861 struct sched_group *group) 7862 { 7863 struct rq *busiest = NULL, *rq; 7864 unsigned long busiest_load = 0, busiest_capacity = 1; 7865 int i; 7866 7867 for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { 7868 unsigned long capacity, wl; 7869 enum fbq_type rt; 7870 7871 rq = cpu_rq(i); 7872 rt = fbq_classify_rq(rq); 7873 7874 /* 7875 * We classify groups/runqueues into three groups: 7876 * - regular: there are !numa tasks 7877 * - remote: there are numa tasks that run on the 'wrong' node 7878 * - all: there is no distinction 7879 * 7880 * In order to avoid migrating ideally placed numa tasks, 7881 * ignore those when there's better options. 7882 * 7883 * If we ignore the actual busiest queue to migrate another 7884 * task, the next balance pass can still reduce the busiest 7885 * queue by moving tasks around inside the node. 7886 * 7887 * If we cannot move enough load due to this classification 7888 * the next pass will adjust the group classification and 7889 * allow migration of more tasks. 7890 * 7891 * Both cases only affect the total convergence complexity. 7892 */ 7893 if (rt > env->fbq_type) 7894 continue; 7895 7896 capacity = capacity_of(i); 7897 7898 wl = weighted_cpuload(i); 7899 7900 /* 7901 * When comparing with imbalance, use weighted_cpuload() 7902 * which is not scaled with the cpu capacity. 7903 */ 7904 7905 if (rq->nr_running == 1 && wl > env->imbalance && 7906 !check_cpu_capacity(rq, env->sd)) 7907 continue; 7908 7909 /* 7910 * For the load comparisons with the other cpu's, consider 7911 * the weighted_cpuload() scaled with the cpu capacity, so 7912 * that the load can be moved away from the cpu that is 7913 * potentially running at a lower capacity. 7914 * 7915 * Thus we're looking for max(wl_i / capacity_i), crosswise 7916 * multiplication to rid ourselves of the division works out 7917 * to: wl_i * capacity_j > wl_j * capacity_i; where j is 7918 * our previous maximum. 7919 */ 7920 if (wl * busiest_capacity > busiest_load * capacity) { 7921 busiest_load = wl; 7922 busiest_capacity = capacity; 7923 busiest = rq; 7924 } 7925 } 7926 7927 return busiest; 7928 } 7929 7930 /* 7931 * Max backoff if we encounter pinned tasks. Pretty arbitrary value, but 7932 * so long as it is large enough. 7933 */ 7934 #define MAX_PINNED_INTERVAL 512 7935 7936 static int need_active_balance(struct lb_env *env) 7937 { 7938 struct sched_domain *sd = env->sd; 7939 7940 if (env->idle == CPU_NEWLY_IDLE) { 7941 7942 /* 7943 * ASYM_PACKING needs to force migrate tasks from busy but 7944 * lower priority CPUs in order to pack all tasks in the 7945 * highest priority CPUs. 7946 */ 7947 if ((sd->flags & SD_ASYM_PACKING) && 7948 sched_asym_prefer(env->dst_cpu, env->src_cpu)) 7949 return 1; 7950 } 7951 7952 /* 7953 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task. 7954 * It's worth migrating the task if the src_cpu's capacity is reduced 7955 * because of other sched_class or IRQs if more capacity stays 7956 * available on dst_cpu. 7957 */ 7958 if ((env->idle != CPU_NOT_IDLE) && 7959 (env->src_rq->cfs.h_nr_running == 1)) { 7960 if ((check_cpu_capacity(env->src_rq, sd)) && 7961 (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) 7962 return 1; 7963 } 7964 7965 return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2); 7966 } 7967 7968 static int active_load_balance_cpu_stop(void *data); 7969 7970 static int should_we_balance(struct lb_env *env) 7971 { 7972 struct sched_group *sg = env->sd->groups; 7973 struct cpumask *sg_cpus, *sg_mask; 7974 int cpu, balance_cpu = -1; 7975 7976 /* 7977 * In the newly idle case, we will allow all the cpu's 7978 * to do the newly idle load balance. 7979 */ 7980 if (env->idle == CPU_NEWLY_IDLE) 7981 return 1; 7982 7983 sg_cpus = sched_group_cpus(sg); 7984 sg_mask = sched_group_mask(sg); 7985 /* Try to find first idle cpu */ 7986 for_each_cpu_and(cpu, sg_cpus, env->cpus) { 7987 if (!cpumask_test_cpu(cpu, sg_mask) || !idle_cpu(cpu)) 7988 continue; 7989 7990 balance_cpu = cpu; 7991 break; 7992 } 7993 7994 if (balance_cpu == -1) 7995 balance_cpu = group_balance_cpu(sg); 7996 7997 /* 7998 * First idle cpu or the first cpu(busiest) in this sched group 7999 * is eligible for doing load balancing at this and above domains. 8000 */ 8001 return balance_cpu == env->dst_cpu; 8002 } 8003 8004 /* 8005 * Check this_cpu to ensure it is balanced within domain. Attempt to move 8006 * tasks if there is an imbalance. 8007 */ 8008 static int load_balance(int this_cpu, struct rq *this_rq, 8009 struct sched_domain *sd, enum cpu_idle_type idle, 8010 int *continue_balancing) 8011 { 8012 int ld_moved, cur_ld_moved, active_balance = 0; 8013 struct sched_domain *sd_parent = sd->parent; 8014 struct sched_group *group; 8015 struct rq *busiest; 8016 unsigned long flags; 8017 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask); 8018 8019 struct lb_env env = { 8020 .sd = sd, 8021 .dst_cpu = this_cpu, 8022 .dst_rq = this_rq, 8023 .dst_grpmask = sched_group_cpus(sd->groups), 8024 .idle = idle, 8025 .loop_break = sched_nr_migrate_break, 8026 .cpus = cpus, 8027 .fbq_type = all, 8028 .tasks = LIST_HEAD_INIT(env.tasks), 8029 }; 8030 8031 /* 8032 * For NEWLY_IDLE load_balancing, we don't need to consider 8033 * other cpus in our group 8034 */ 8035 if (idle == CPU_NEWLY_IDLE) 8036 env.dst_grpmask = NULL; 8037 8038 cpumask_copy(cpus, cpu_active_mask); 8039 8040 schedstat_inc(sd->lb_count[idle]); 8041 8042 redo: 8043 if (!should_we_balance(&env)) { 8044 *continue_balancing = 0; 8045 goto out_balanced; 8046 } 8047 8048 group = find_busiest_group(&env); 8049 if (!group) { 8050 schedstat_inc(sd->lb_nobusyg[idle]); 8051 goto out_balanced; 8052 } 8053 8054 busiest = find_busiest_queue(&env, group); 8055 if (!busiest) { 8056 schedstat_inc(sd->lb_nobusyq[idle]); 8057 goto out_balanced; 8058 } 8059 8060 BUG_ON(busiest == env.dst_rq); 8061 8062 schedstat_add(sd->lb_imbalance[idle], env.imbalance); 8063 8064 env.src_cpu = busiest->cpu; 8065 env.src_rq = busiest; 8066 8067 ld_moved = 0; 8068 if (busiest->nr_running > 1) { 8069 /* 8070 * Attempt to move tasks. If find_busiest_group has found 8071 * an imbalance but busiest->nr_running <= 1, the group is 8072 * still unbalanced. ld_moved simply stays zero, so it is 8073 * correctly treated as an imbalance. 8074 */ 8075 env.flags |= LBF_ALL_PINNED; 8076 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running); 8077 8078 more_balance: 8079 raw_spin_lock_irqsave(&busiest->lock, flags); 8080 8081 /* 8082 * cur_ld_moved - load moved in current iteration 8083 * ld_moved - cumulative load moved across iterations 8084 */ 8085 cur_ld_moved = detach_tasks(&env); 8086 8087 /* 8088 * We've detached some tasks from busiest_rq. Every 8089 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely 8090 * unlock busiest->lock, and we are able to be sure 8091 * that nobody can manipulate the tasks in parallel. 8092 * See task_rq_lock() family for the details. 8093 */ 8094 8095 raw_spin_unlock(&busiest->lock); 8096 8097 if (cur_ld_moved) { 8098 attach_tasks(&env); 8099 ld_moved += cur_ld_moved; 8100 } 8101 8102 local_irq_restore(flags); 8103 8104 if (env.flags & LBF_NEED_BREAK) { 8105 env.flags &= ~LBF_NEED_BREAK; 8106 goto more_balance; 8107 } 8108 8109 /* 8110 * Revisit (affine) tasks on src_cpu that couldn't be moved to 8111 * us and move them to an alternate dst_cpu in our sched_group 8112 * where they can run. The upper limit on how many times we 8113 * iterate on same src_cpu is dependent on number of cpus in our 8114 * sched_group. 8115 * 8116 * This changes load balance semantics a bit on who can move 8117 * load to a given_cpu. In addition to the given_cpu itself 8118 * (or a ilb_cpu acting on its behalf where given_cpu is 8119 * nohz-idle), we now have balance_cpu in a position to move 8120 * load to given_cpu. In rare situations, this may cause 8121 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding 8122 * _independently_ and at _same_ time to move some load to 8123 * given_cpu) causing exceess load to be moved to given_cpu. 8124 * This however should not happen so much in practice and 8125 * moreover subsequent load balance cycles should correct the 8126 * excess load moved. 8127 */ 8128 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) { 8129 8130 /* Prevent to re-select dst_cpu via env's cpus */ 8131 cpumask_clear_cpu(env.dst_cpu, env.cpus); 8132 8133 env.dst_rq = cpu_rq(env.new_dst_cpu); 8134 env.dst_cpu = env.new_dst_cpu; 8135 env.flags &= ~LBF_DST_PINNED; 8136 env.loop = 0; 8137 env.loop_break = sched_nr_migrate_break; 8138 8139 /* 8140 * Go back to "more_balance" rather than "redo" since we 8141 * need to continue with same src_cpu. 8142 */ 8143 goto more_balance; 8144 } 8145 8146 /* 8147 * We failed to reach balance because of affinity. 8148 */ 8149 if (sd_parent) { 8150 int *group_imbalance = &sd_parent->groups->sgc->imbalance; 8151 8152 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0) 8153 *group_imbalance = 1; 8154 } 8155 8156 /* All tasks on this runqueue were pinned by CPU affinity */ 8157 if (unlikely(env.flags & LBF_ALL_PINNED)) { 8158 cpumask_clear_cpu(cpu_of(busiest), cpus); 8159 if (!cpumask_empty(cpus)) { 8160 env.loop = 0; 8161 env.loop_break = sched_nr_migrate_break; 8162 goto redo; 8163 } 8164 goto out_all_pinned; 8165 } 8166 } 8167 8168 if (!ld_moved) { 8169 schedstat_inc(sd->lb_failed[idle]); 8170 /* 8171 * Increment the failure counter only on periodic balance. 8172 * We do not want newidle balance, which can be very 8173 * frequent, pollute the failure counter causing 8174 * excessive cache_hot migrations and active balances. 8175 */ 8176 if (idle != CPU_NEWLY_IDLE) 8177 sd->nr_balance_failed++; 8178 8179 if (need_active_balance(&env)) { 8180 raw_spin_lock_irqsave(&busiest->lock, flags); 8181 8182 /* don't kick the active_load_balance_cpu_stop, 8183 * if the curr task on busiest cpu can't be 8184 * moved to this_cpu 8185 */ 8186 if (!cpumask_test_cpu(this_cpu, 8187 tsk_cpus_allowed(busiest->curr))) { 8188 raw_spin_unlock_irqrestore(&busiest->lock, 8189 flags); 8190 env.flags |= LBF_ALL_PINNED; 8191 goto out_one_pinned; 8192 } 8193 8194 /* 8195 * ->active_balance synchronizes accesses to 8196 * ->active_balance_work. Once set, it's cleared 8197 * only after active load balance is finished. 8198 */ 8199 if (!busiest->active_balance) { 8200 busiest->active_balance = 1; 8201 busiest->push_cpu = this_cpu; 8202 active_balance = 1; 8203 } 8204 raw_spin_unlock_irqrestore(&busiest->lock, flags); 8205 8206 if (active_balance) { 8207 stop_one_cpu_nowait(cpu_of(busiest), 8208 active_load_balance_cpu_stop, busiest, 8209 &busiest->active_balance_work); 8210 } 8211 8212 /* We've kicked active balancing, force task migration. */ 8213 sd->nr_balance_failed = sd->cache_nice_tries+1; 8214 } 8215 } else 8216 sd->nr_balance_failed = 0; 8217 8218 if (likely(!active_balance)) { 8219 /* We were unbalanced, so reset the balancing interval */ 8220 sd->balance_interval = sd->min_interval; 8221 } else { 8222 /* 8223 * If we've begun active balancing, start to back off. This 8224 * case may not be covered by the all_pinned logic if there 8225 * is only 1 task on the busy runqueue (because we don't call 8226 * detach_tasks). 8227 */ 8228 if (sd->balance_interval < sd->max_interval) 8229 sd->balance_interval *= 2; 8230 } 8231 8232 goto out; 8233 8234 out_balanced: 8235 /* 8236 * We reach balance although we may have faced some affinity 8237 * constraints. Clear the imbalance flag if it was set. 8238 */ 8239 if (sd_parent) { 8240 int *group_imbalance = &sd_parent->groups->sgc->imbalance; 8241 8242 if (*group_imbalance) 8243 *group_imbalance = 0; 8244 } 8245 8246 out_all_pinned: 8247 /* 8248 * We reach balance because all tasks are pinned at this level so 8249 * we can't migrate them. Let the imbalance flag set so parent level 8250 * can try to migrate them. 8251 */ 8252 schedstat_inc(sd->lb_balanced[idle]); 8253 8254 sd->nr_balance_failed = 0; 8255 8256 out_one_pinned: 8257 /* tune up the balancing interval */ 8258 if (((env.flags & LBF_ALL_PINNED) && 8259 sd->balance_interval < MAX_PINNED_INTERVAL) || 8260 (sd->balance_interval < sd->max_interval)) 8261 sd->balance_interval *= 2; 8262 8263 ld_moved = 0; 8264 out: 8265 return ld_moved; 8266 } 8267 8268 static inline unsigned long 8269 get_sd_balance_interval(struct sched_domain *sd, int cpu_busy) 8270 { 8271 unsigned long interval = sd->balance_interval; 8272 8273 if (cpu_busy) 8274 interval *= sd->busy_factor; 8275 8276 /* scale ms to jiffies */ 8277 interval = msecs_to_jiffies(interval); 8278 interval = clamp(interval, 1UL, max_load_balance_interval); 8279 8280 return interval; 8281 } 8282 8283 static inline void 8284 update_next_balance(struct sched_domain *sd, unsigned long *next_balance) 8285 { 8286 unsigned long interval, next; 8287 8288 /* used by idle balance, so cpu_busy = 0 */ 8289 interval = get_sd_balance_interval(sd, 0); 8290 next = sd->last_balance + interval; 8291 8292 if (time_after(*next_balance, next)) 8293 *next_balance = next; 8294 } 8295 8296 /* 8297 * idle_balance is called by schedule() if this_cpu is about to become 8298 * idle. Attempts to pull tasks from other CPUs. 8299 */ 8300 static int idle_balance(struct rq *this_rq) 8301 { 8302 unsigned long next_balance = jiffies + HZ; 8303 int this_cpu = this_rq->cpu; 8304 struct sched_domain *sd; 8305 int pulled_task = 0; 8306 u64 curr_cost = 0; 8307 8308 /* 8309 * We must set idle_stamp _before_ calling idle_balance(), such that we 8310 * measure the duration of idle_balance() as idle time. 8311 */ 8312 this_rq->idle_stamp = rq_clock(this_rq); 8313 8314 if (this_rq->avg_idle < sysctl_sched_migration_cost || 8315 !this_rq->rd->overload) { 8316 rcu_read_lock(); 8317 sd = rcu_dereference_check_sched_domain(this_rq->sd); 8318 if (sd) 8319 update_next_balance(sd, &next_balance); 8320 rcu_read_unlock(); 8321 8322 goto out; 8323 } 8324 8325 raw_spin_unlock(&this_rq->lock); 8326 8327 update_blocked_averages(this_cpu); 8328 rcu_read_lock(); 8329 for_each_domain(this_cpu, sd) { 8330 int continue_balancing = 1; 8331 u64 t0, domain_cost; 8332 8333 if (!(sd->flags & SD_LOAD_BALANCE)) 8334 continue; 8335 8336 if (this_rq->avg_idle < curr_cost + sd->max_newidle_lb_cost) { 8337 update_next_balance(sd, &next_balance); 8338 break; 8339 } 8340 8341 if (sd->flags & SD_BALANCE_NEWIDLE) { 8342 t0 = sched_clock_cpu(this_cpu); 8343 8344 pulled_task = load_balance(this_cpu, this_rq, 8345 sd, CPU_NEWLY_IDLE, 8346 &continue_balancing); 8347 8348 domain_cost = sched_clock_cpu(this_cpu) - t0; 8349 if (domain_cost > sd->max_newidle_lb_cost) 8350 sd->max_newidle_lb_cost = domain_cost; 8351 8352 curr_cost += domain_cost; 8353 } 8354 8355 update_next_balance(sd, &next_balance); 8356 8357 /* 8358 * Stop searching for tasks to pull if there are 8359 * now runnable tasks on this rq. 8360 */ 8361 if (pulled_task || this_rq->nr_running > 0) 8362 break; 8363 } 8364 rcu_read_unlock(); 8365 8366 raw_spin_lock(&this_rq->lock); 8367 8368 if (curr_cost > this_rq->max_idle_balance_cost) 8369 this_rq->max_idle_balance_cost = curr_cost; 8370 8371 /* 8372 * While browsing the domains, we released the rq lock, a task could 8373 * have been enqueued in the meantime. Since we're not going idle, 8374 * pretend we pulled a task. 8375 */ 8376 if (this_rq->cfs.h_nr_running && !pulled_task) 8377 pulled_task = 1; 8378 8379 out: 8380 /* Move the next balance forward */ 8381 if (time_after(this_rq->next_balance, next_balance)) 8382 this_rq->next_balance = next_balance; 8383 8384 /* Is there a task of a high priority class? */ 8385 if (this_rq->nr_running != this_rq->cfs.h_nr_running) 8386 pulled_task = -1; 8387 8388 if (pulled_task) 8389 this_rq->idle_stamp = 0; 8390 8391 return pulled_task; 8392 } 8393 8394 /* 8395 * active_load_balance_cpu_stop is run by cpu stopper. It pushes 8396 * running tasks off the busiest CPU onto idle CPUs. It requires at 8397 * least 1 task to be running on each physical CPU where possible, and 8398 * avoids physical / logical imbalances. 8399 */ 8400 static int active_load_balance_cpu_stop(void *data) 8401 { 8402 struct rq *busiest_rq = data; 8403 int busiest_cpu = cpu_of(busiest_rq); 8404 int target_cpu = busiest_rq->push_cpu; 8405 struct rq *target_rq = cpu_rq(target_cpu); 8406 struct sched_domain *sd; 8407 struct task_struct *p = NULL; 8408 8409 raw_spin_lock_irq(&busiest_rq->lock); 8410 8411 /* make sure the requested cpu hasn't gone down in the meantime */ 8412 if (unlikely(busiest_cpu != smp_processor_id() || 8413 !busiest_rq->active_balance)) 8414 goto out_unlock; 8415 8416 /* Is there any task to move? */ 8417 if (busiest_rq->nr_running <= 1) 8418 goto out_unlock; 8419 8420 /* 8421 * This condition is "impossible", if it occurs 8422 * we need to fix it. Originally reported by 8423 * Bjorn Helgaas on a 128-cpu setup. 8424 */ 8425 BUG_ON(busiest_rq == target_rq); 8426 8427 /* Search for an sd spanning us and the target CPU. */ 8428 rcu_read_lock(); 8429 for_each_domain(target_cpu, sd) { 8430 if ((sd->flags & SD_LOAD_BALANCE) && 8431 cpumask_test_cpu(busiest_cpu, sched_domain_span(sd))) 8432 break; 8433 } 8434 8435 if (likely(sd)) { 8436 struct lb_env env = { 8437 .sd = sd, 8438 .dst_cpu = target_cpu, 8439 .dst_rq = target_rq, 8440 .src_cpu = busiest_rq->cpu, 8441 .src_rq = busiest_rq, 8442 .idle = CPU_IDLE, 8443 }; 8444 8445 schedstat_inc(sd->alb_count); 8446 8447 p = detach_one_task(&env); 8448 if (p) { 8449 schedstat_inc(sd->alb_pushed); 8450 /* Active balancing done, reset the failure counter. */ 8451 sd->nr_balance_failed = 0; 8452 } else { 8453 schedstat_inc(sd->alb_failed); 8454 } 8455 } 8456 rcu_read_unlock(); 8457 out_unlock: 8458 busiest_rq->active_balance = 0; 8459 raw_spin_unlock(&busiest_rq->lock); 8460 8461 if (p) 8462 attach_one_task(target_rq, p); 8463 8464 local_irq_enable(); 8465 8466 return 0; 8467 } 8468 8469 static inline int on_null_domain(struct rq *rq) 8470 { 8471 return unlikely(!rcu_dereference_sched(rq->sd)); 8472 } 8473 8474 #ifdef CONFIG_NO_HZ_COMMON 8475 /* 8476 * idle load balancing details 8477 * - When one of the busy CPUs notice that there may be an idle rebalancing 8478 * needed, they will kick the idle load balancer, which then does idle 8479 * load balancing for all the idle CPUs. 8480 */ 8481 static struct { 8482 cpumask_var_t idle_cpus_mask; 8483 atomic_t nr_cpus; 8484 unsigned long next_balance; /* in jiffy units */ 8485 } nohz ____cacheline_aligned; 8486 8487 static inline int find_new_ilb(void) 8488 { 8489 int ilb = cpumask_first(nohz.idle_cpus_mask); 8490 8491 if (ilb < nr_cpu_ids && idle_cpu(ilb)) 8492 return ilb; 8493 8494 return nr_cpu_ids; 8495 } 8496 8497 /* 8498 * Kick a CPU to do the nohz balancing, if it is time for it. We pick the 8499 * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle 8500 * CPU (if there is one). 8501 */ 8502 static void nohz_balancer_kick(void) 8503 { 8504 int ilb_cpu; 8505 8506 nohz.next_balance++; 8507 8508 ilb_cpu = find_new_ilb(); 8509 8510 if (ilb_cpu >= nr_cpu_ids) 8511 return; 8512 8513 if (test_and_set_bit(NOHZ_BALANCE_KICK, nohz_flags(ilb_cpu))) 8514 return; 8515 /* 8516 * Use smp_send_reschedule() instead of resched_cpu(). 8517 * This way we generate a sched IPI on the target cpu which 8518 * is idle. And the softirq performing nohz idle load balance 8519 * will be run before returning from the IPI. 8520 */ 8521 smp_send_reschedule(ilb_cpu); 8522 return; 8523 } 8524 8525 void nohz_balance_exit_idle(unsigned int cpu) 8526 { 8527 if (unlikely(test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))) { 8528 /* 8529 * Completely isolated CPUs don't ever set, so we must test. 8530 */ 8531 if (likely(cpumask_test_cpu(cpu, nohz.idle_cpus_mask))) { 8532 cpumask_clear_cpu(cpu, nohz.idle_cpus_mask); 8533 atomic_dec(&nohz.nr_cpus); 8534 } 8535 clear_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 8536 } 8537 } 8538 8539 static inline void set_cpu_sd_state_busy(void) 8540 { 8541 struct sched_domain *sd; 8542 int cpu = smp_processor_id(); 8543 8544 rcu_read_lock(); 8545 sd = rcu_dereference(per_cpu(sd_llc, cpu)); 8546 8547 if (!sd || !sd->nohz_idle) 8548 goto unlock; 8549 sd->nohz_idle = 0; 8550 8551 atomic_inc(&sd->shared->nr_busy_cpus); 8552 unlock: 8553 rcu_read_unlock(); 8554 } 8555 8556 void set_cpu_sd_state_idle(void) 8557 { 8558 struct sched_domain *sd; 8559 int cpu = smp_processor_id(); 8560 8561 rcu_read_lock(); 8562 sd = rcu_dereference(per_cpu(sd_llc, cpu)); 8563 8564 if (!sd || sd->nohz_idle) 8565 goto unlock; 8566 sd->nohz_idle = 1; 8567 8568 atomic_dec(&sd->shared->nr_busy_cpus); 8569 unlock: 8570 rcu_read_unlock(); 8571 } 8572 8573 /* 8574 * This routine will record that the cpu is going idle with tick stopped. 8575 * This info will be used in performing idle load balancing in the future. 8576 */ 8577 void nohz_balance_enter_idle(int cpu) 8578 { 8579 /* 8580 * If this cpu is going down, then nothing needs to be done. 8581 */ 8582 if (!cpu_active(cpu)) 8583 return; 8584 8585 if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu))) 8586 return; 8587 8588 /* 8589 * If we're a completely isolated CPU, we don't play. 8590 */ 8591 if (on_null_domain(cpu_rq(cpu))) 8592 return; 8593 8594 cpumask_set_cpu(cpu, nohz.idle_cpus_mask); 8595 atomic_inc(&nohz.nr_cpus); 8596 set_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)); 8597 } 8598 #endif 8599 8600 static DEFINE_SPINLOCK(balancing); 8601 8602 /* 8603 * Scale the max load_balance interval with the number of CPUs in the system. 8604 * This trades load-balance latency on larger machines for less cross talk. 8605 */ 8606 void update_max_interval(void) 8607 { 8608 max_load_balance_interval = HZ*num_online_cpus()/10; 8609 } 8610 8611 /* 8612 * It checks each scheduling domain to see if it is due to be balanced, 8613 * and initiates a balancing operation if so. 8614 * 8615 * Balancing parameters are set up in init_sched_domains. 8616 */ 8617 static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) 8618 { 8619 int continue_balancing = 1; 8620 int cpu = rq->cpu; 8621 unsigned long interval; 8622 struct sched_domain *sd; 8623 /* Earliest time when we have to do rebalance again */ 8624 unsigned long next_balance = jiffies + 60*HZ; 8625 int update_next_balance = 0; 8626 int need_serialize, need_decay = 0; 8627 u64 max_cost = 0; 8628 8629 update_blocked_averages(cpu); 8630 8631 rcu_read_lock(); 8632 for_each_domain(cpu, sd) { 8633 /* 8634 * Decay the newidle max times here because this is a regular 8635 * visit to all the domains. Decay ~1% per second. 8636 */ 8637 if (time_after(jiffies, sd->next_decay_max_lb_cost)) { 8638 sd->max_newidle_lb_cost = 8639 (sd->max_newidle_lb_cost * 253) / 256; 8640 sd->next_decay_max_lb_cost = jiffies + HZ; 8641 need_decay = 1; 8642 } 8643 max_cost += sd->max_newidle_lb_cost; 8644 8645 if (!(sd->flags & SD_LOAD_BALANCE)) 8646 continue; 8647 8648 /* 8649 * Stop the load balance at this level. There is another 8650 * CPU in our sched group which is doing load balancing more 8651 * actively. 8652 */ 8653 if (!continue_balancing) { 8654 if (need_decay) 8655 continue; 8656 break; 8657 } 8658 8659 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 8660 8661 need_serialize = sd->flags & SD_SERIALIZE; 8662 if (need_serialize) { 8663 if (!spin_trylock(&balancing)) 8664 goto out; 8665 } 8666 8667 if (time_after_eq(jiffies, sd->last_balance + interval)) { 8668 if (load_balance(cpu, rq, sd, idle, &continue_balancing)) { 8669 /* 8670 * The LBF_DST_PINNED logic could have changed 8671 * env->dst_cpu, so we can't know our idle 8672 * state even if we migrated tasks. Update it. 8673 */ 8674 idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; 8675 } 8676 sd->last_balance = jiffies; 8677 interval = get_sd_balance_interval(sd, idle != CPU_IDLE); 8678 } 8679 if (need_serialize) 8680 spin_unlock(&balancing); 8681 out: 8682 if (time_after(next_balance, sd->last_balance + interval)) { 8683 next_balance = sd->last_balance + interval; 8684 update_next_balance = 1; 8685 } 8686 } 8687 if (need_decay) { 8688 /* 8689 * Ensure the rq-wide value also decays but keep it at a 8690 * reasonable floor to avoid funnies with rq->avg_idle. 8691 */ 8692 rq->max_idle_balance_cost = 8693 max((u64)sysctl_sched_migration_cost, max_cost); 8694 } 8695 rcu_read_unlock(); 8696 8697 /* 8698 * next_balance will be updated only when there is a need. 8699 * When the cpu is attached to null domain for ex, it will not be 8700 * updated. 8701 */ 8702 if (likely(update_next_balance)) { 8703 rq->next_balance = next_balance; 8704 8705 #ifdef CONFIG_NO_HZ_COMMON 8706 /* 8707 * If this CPU has been elected to perform the nohz idle 8708 * balance. Other idle CPUs have already rebalanced with 8709 * nohz_idle_balance() and nohz.next_balance has been 8710 * updated accordingly. This CPU is now running the idle load 8711 * balance for itself and we need to update the 8712 * nohz.next_balance accordingly. 8713 */ 8714 if ((idle == CPU_IDLE) && time_after(nohz.next_balance, rq->next_balance)) 8715 nohz.next_balance = rq->next_balance; 8716 #endif 8717 } 8718 } 8719 8720 #ifdef CONFIG_NO_HZ_COMMON 8721 /* 8722 * In CONFIG_NO_HZ_COMMON case, the idle balance kickee will do the 8723 * rebalancing for all the cpus for whom scheduler ticks are stopped. 8724 */ 8725 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) 8726 { 8727 int this_cpu = this_rq->cpu; 8728 struct rq *rq; 8729 int balance_cpu; 8730 /* Earliest time when we have to do rebalance again */ 8731 unsigned long next_balance = jiffies + 60*HZ; 8732 int update_next_balance = 0; 8733 8734 if (idle != CPU_IDLE || 8735 !test_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu))) 8736 goto end; 8737 8738 for_each_cpu(balance_cpu, nohz.idle_cpus_mask) { 8739 if (balance_cpu == this_cpu || !idle_cpu(balance_cpu)) 8740 continue; 8741 8742 /* 8743 * If this cpu gets work to do, stop the load balancing 8744 * work being done for other cpus. Next load 8745 * balancing owner will pick it up. 8746 */ 8747 if (need_resched()) 8748 break; 8749 8750 rq = cpu_rq(balance_cpu); 8751 8752 /* 8753 * If time for next balance is due, 8754 * do the balance. 8755 */ 8756 if (time_after_eq(jiffies, rq->next_balance)) { 8757 raw_spin_lock_irq(&rq->lock); 8758 update_rq_clock(rq); 8759 cpu_load_update_idle(rq); 8760 raw_spin_unlock_irq(&rq->lock); 8761 rebalance_domains(rq, CPU_IDLE); 8762 } 8763 8764 if (time_after(next_balance, rq->next_balance)) { 8765 next_balance = rq->next_balance; 8766 update_next_balance = 1; 8767 } 8768 } 8769 8770 /* 8771 * next_balance will be updated only when there is a need. 8772 * When the CPU is attached to null domain for ex, it will not be 8773 * updated. 8774 */ 8775 if (likely(update_next_balance)) 8776 nohz.next_balance = next_balance; 8777 end: 8778 clear_bit(NOHZ_BALANCE_KICK, nohz_flags(this_cpu)); 8779 } 8780 8781 /* 8782 * Current heuristic for kicking the idle load balancer in the presence 8783 * of an idle cpu in the system. 8784 * - This rq has more than one task. 8785 * - This rq has at least one CFS task and the capacity of the CPU is 8786 * significantly reduced because of RT tasks or IRQs. 8787 * - At parent of LLC scheduler domain level, this cpu's scheduler group has 8788 * multiple busy cpu. 8789 * - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler 8790 * domain span are idle. 8791 */ 8792 static inline bool nohz_kick_needed(struct rq *rq) 8793 { 8794 unsigned long now = jiffies; 8795 struct sched_domain_shared *sds; 8796 struct sched_domain *sd; 8797 int nr_busy, i, cpu = rq->cpu; 8798 bool kick = false; 8799 8800 if (unlikely(rq->idle_balance)) 8801 return false; 8802 8803 /* 8804 * We may be recently in ticked or tickless idle mode. At the first 8805 * busy tick after returning from idle, we will update the busy stats. 8806 */ 8807 set_cpu_sd_state_busy(); 8808 nohz_balance_exit_idle(cpu); 8809 8810 /* 8811 * None are in tickless mode and hence no need for NOHZ idle load 8812 * balancing. 8813 */ 8814 if (likely(!atomic_read(&nohz.nr_cpus))) 8815 return false; 8816 8817 if (time_before(now, nohz.next_balance)) 8818 return false; 8819 8820 if (rq->nr_running >= 2) 8821 return true; 8822 8823 rcu_read_lock(); 8824 sds = rcu_dereference(per_cpu(sd_llc_shared, cpu)); 8825 if (sds) { 8826 /* 8827 * XXX: write a coherent comment on why we do this. 8828 * See also: http://lkml.kernel.org/r/20111202010832.602203411@sbsiddha-desk.sc.intel.com 8829 */ 8830 nr_busy = atomic_read(&sds->nr_busy_cpus); 8831 if (nr_busy > 1) { 8832 kick = true; 8833 goto unlock; 8834 } 8835 8836 } 8837 8838 sd = rcu_dereference(rq->sd); 8839 if (sd) { 8840 if ((rq->cfs.h_nr_running >= 1) && 8841 check_cpu_capacity(rq, sd)) { 8842 kick = true; 8843 goto unlock; 8844 } 8845 } 8846 8847 sd = rcu_dereference(per_cpu(sd_asym, cpu)); 8848 if (sd) { 8849 for_each_cpu(i, sched_domain_span(sd)) { 8850 if (i == cpu || 8851 !cpumask_test_cpu(i, nohz.idle_cpus_mask)) 8852 continue; 8853 8854 if (sched_asym_prefer(i, cpu)) { 8855 kick = true; 8856 goto unlock; 8857 } 8858 } 8859 } 8860 unlock: 8861 rcu_read_unlock(); 8862 return kick; 8863 } 8864 #else 8865 static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { } 8866 #endif 8867 8868 /* 8869 * run_rebalance_domains is triggered when needed from the scheduler tick. 8870 * Also triggered for nohz idle balancing (with nohz_balancing_kick set). 8871 */ 8872 static __latent_entropy void run_rebalance_domains(struct softirq_action *h) 8873 { 8874 struct rq *this_rq = this_rq(); 8875 enum cpu_idle_type idle = this_rq->idle_balance ? 8876 CPU_IDLE : CPU_NOT_IDLE; 8877 8878 /* 8879 * If this cpu has a pending nohz_balance_kick, then do the 8880 * balancing on behalf of the other idle cpus whose ticks are 8881 * stopped. Do nohz_idle_balance *before* rebalance_domains to 8882 * give the idle cpus a chance to load balance. Else we may 8883 * load balance only within the local sched_domain hierarchy 8884 * and abort nohz_idle_balance altogether if we pull some load. 8885 */ 8886 nohz_idle_balance(this_rq, idle); 8887 rebalance_domains(this_rq, idle); 8888 } 8889 8890 /* 8891 * Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing. 8892 */ 8893 void trigger_load_balance(struct rq *rq) 8894 { 8895 /* Don't need to rebalance while attached to NULL domain */ 8896 if (unlikely(on_null_domain(rq))) 8897 return; 8898 8899 if (time_after_eq(jiffies, rq->next_balance)) 8900 raise_softirq(SCHED_SOFTIRQ); 8901 #ifdef CONFIG_NO_HZ_COMMON 8902 if (nohz_kick_needed(rq)) 8903 nohz_balancer_kick(); 8904 #endif 8905 } 8906 8907 static void rq_online_fair(struct rq *rq) 8908 { 8909 update_sysctl(); 8910 8911 update_runtime_enabled(rq); 8912 } 8913 8914 static void rq_offline_fair(struct rq *rq) 8915 { 8916 update_sysctl(); 8917 8918 /* Ensure any throttled groups are reachable by pick_next_task */ 8919 unthrottle_offline_cfs_rqs(rq); 8920 } 8921 8922 #endif /* CONFIG_SMP */ 8923 8924 /* 8925 * scheduler tick hitting a task of our scheduling class: 8926 */ 8927 static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued) 8928 { 8929 struct cfs_rq *cfs_rq; 8930 struct sched_entity *se = &curr->se; 8931 8932 for_each_sched_entity(se) { 8933 cfs_rq = cfs_rq_of(se); 8934 entity_tick(cfs_rq, se, queued); 8935 } 8936 8937 if (static_branch_unlikely(&sched_numa_balancing)) 8938 task_tick_numa(rq, curr); 8939 } 8940 8941 /* 8942 * called on fork with the child task as argument from the parent's context 8943 * - child not yet on the tasklist 8944 * - preemption disabled 8945 */ 8946 static void task_fork_fair(struct task_struct *p) 8947 { 8948 struct cfs_rq *cfs_rq; 8949 struct sched_entity *se = &p->se, *curr; 8950 struct rq *rq = this_rq(); 8951 8952 raw_spin_lock(&rq->lock); 8953 update_rq_clock(rq); 8954 8955 cfs_rq = task_cfs_rq(current); 8956 curr = cfs_rq->curr; 8957 if (curr) { 8958 update_curr(cfs_rq); 8959 se->vruntime = curr->vruntime; 8960 } 8961 place_entity(cfs_rq, se, 1); 8962 8963 if (sysctl_sched_child_runs_first && curr && entity_before(curr, se)) { 8964 /* 8965 * Upon rescheduling, sched_class::put_prev_task() will place 8966 * 'current' within the tree based on its new key value. 8967 */ 8968 swap(curr->vruntime, se->vruntime); 8969 resched_curr(rq); 8970 } 8971 8972 se->vruntime -= cfs_rq->min_vruntime; 8973 raw_spin_unlock(&rq->lock); 8974 } 8975 8976 /* 8977 * Priority of the task has changed. Check to see if we preempt 8978 * the current task. 8979 */ 8980 static void 8981 prio_changed_fair(struct rq *rq, struct task_struct *p, int oldprio) 8982 { 8983 if (!task_on_rq_queued(p)) 8984 return; 8985 8986 /* 8987 * Reschedule if we are currently running on this runqueue and 8988 * our priority decreased, or if we are not currently running on 8989 * this runqueue and our priority is higher than the current's 8990 */ 8991 if (rq->curr == p) { 8992 if (p->prio > oldprio) 8993 resched_curr(rq); 8994 } else 8995 check_preempt_curr(rq, p, 0); 8996 } 8997 8998 static inline bool vruntime_normalized(struct task_struct *p) 8999 { 9000 struct sched_entity *se = &p->se; 9001 9002 /* 9003 * In both the TASK_ON_RQ_QUEUED and TASK_ON_RQ_MIGRATING cases, 9004 * the dequeue_entity(.flags=0) will already have normalized the 9005 * vruntime. 9006 */ 9007 if (p->on_rq) 9008 return true; 9009 9010 /* 9011 * When !on_rq, vruntime of the task has usually NOT been normalized. 9012 * But there are some cases where it has already been normalized: 9013 * 9014 * - A forked child which is waiting for being woken up by 9015 * wake_up_new_task(). 9016 * - A task which has been woken up by try_to_wake_up() and 9017 * waiting for actually being woken up by sched_ttwu_pending(). 9018 */ 9019 if (!se->sum_exec_runtime || p->state == TASK_WAKING) 9020 return true; 9021 9022 return false; 9023 } 9024 9025 #ifdef CONFIG_FAIR_GROUP_SCHED 9026 /* 9027 * Propagate the changes of the sched_entity across the tg tree to make it 9028 * visible to the root 9029 */ 9030 static void propagate_entity_cfs_rq(struct sched_entity *se) 9031 { 9032 struct cfs_rq *cfs_rq; 9033 9034 /* Start to propagate at parent */ 9035 se = se->parent; 9036 9037 for_each_sched_entity(se) { 9038 cfs_rq = cfs_rq_of(se); 9039 9040 if (cfs_rq_throttled(cfs_rq)) 9041 break; 9042 9043 update_load_avg(se, UPDATE_TG); 9044 } 9045 } 9046 #else 9047 static void propagate_entity_cfs_rq(struct sched_entity *se) { } 9048 #endif 9049 9050 static void detach_entity_cfs_rq(struct sched_entity *se) 9051 { 9052 struct cfs_rq *cfs_rq = cfs_rq_of(se); 9053 9054 /* Catch up with the cfs_rq and remove our load when we leave */ 9055 update_load_avg(se, 0); 9056 detach_entity_load_avg(cfs_rq, se); 9057 update_tg_load_avg(cfs_rq, false); 9058 propagate_entity_cfs_rq(se); 9059 } 9060 9061 static void attach_entity_cfs_rq(struct sched_entity *se) 9062 { 9063 struct cfs_rq *cfs_rq = cfs_rq_of(se); 9064 9065 #ifdef CONFIG_FAIR_GROUP_SCHED 9066 /* 9067 * Since the real-depth could have been changed (only FAIR 9068 * class maintain depth value), reset depth properly. 9069 */ 9070 se->depth = se->parent ? se->parent->depth + 1 : 0; 9071 #endif 9072 9073 /* Synchronize entity with its cfs_rq */ 9074 update_load_avg(se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD); 9075 attach_entity_load_avg(cfs_rq, se); 9076 update_tg_load_avg(cfs_rq, false); 9077 propagate_entity_cfs_rq(se); 9078 } 9079 9080 static void detach_task_cfs_rq(struct task_struct *p) 9081 { 9082 struct sched_entity *se = &p->se; 9083 struct cfs_rq *cfs_rq = cfs_rq_of(se); 9084 9085 if (!vruntime_normalized(p)) { 9086 /* 9087 * Fix up our vruntime so that the current sleep doesn't 9088 * cause 'unlimited' sleep bonus. 9089 */ 9090 place_entity(cfs_rq, se, 0); 9091 se->vruntime -= cfs_rq->min_vruntime; 9092 } 9093 9094 detach_entity_cfs_rq(se); 9095 } 9096 9097 static void attach_task_cfs_rq(struct task_struct *p) 9098 { 9099 struct sched_entity *se = &p->se; 9100 struct cfs_rq *cfs_rq = cfs_rq_of(se); 9101 9102 attach_entity_cfs_rq(se); 9103 9104 if (!vruntime_normalized(p)) 9105 se->vruntime += cfs_rq->min_vruntime; 9106 } 9107 9108 static void switched_from_fair(struct rq *rq, struct task_struct *p) 9109 { 9110 detach_task_cfs_rq(p); 9111 } 9112 9113 static void switched_to_fair(struct rq *rq, struct task_struct *p) 9114 { 9115 attach_task_cfs_rq(p); 9116 9117 if (task_on_rq_queued(p)) { 9118 /* 9119 * We were most likely switched from sched_rt, so 9120 * kick off the schedule if running, otherwise just see 9121 * if we can still preempt the current task. 9122 */ 9123 if (rq->curr == p) 9124 resched_curr(rq); 9125 else 9126 check_preempt_curr(rq, p, 0); 9127 } 9128 } 9129 9130 /* Account for a task changing its policy or group. 9131 * 9132 * This routine is mostly called to set cfs_rq->curr field when a task 9133 * migrates between groups/classes. 9134 */ 9135 static void set_curr_task_fair(struct rq *rq) 9136 { 9137 struct sched_entity *se = &rq->curr->se; 9138 9139 for_each_sched_entity(se) { 9140 struct cfs_rq *cfs_rq = cfs_rq_of(se); 9141 9142 set_next_entity(cfs_rq, se); 9143 /* ensure bandwidth has been allocated on our new cfs_rq */ 9144 account_cfs_rq_runtime(cfs_rq, 0); 9145 } 9146 } 9147 9148 void init_cfs_rq(struct cfs_rq *cfs_rq) 9149 { 9150 cfs_rq->tasks_timeline = RB_ROOT; 9151 cfs_rq->min_vruntime = (u64)(-(1LL << 20)); 9152 #ifndef CONFIG_64BIT 9153 cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime; 9154 #endif 9155 #ifdef CONFIG_SMP 9156 #ifdef CONFIG_FAIR_GROUP_SCHED 9157 cfs_rq->propagate_avg = 0; 9158 #endif 9159 atomic_long_set(&cfs_rq->removed_load_avg, 0); 9160 atomic_long_set(&cfs_rq->removed_util_avg, 0); 9161 #endif 9162 } 9163 9164 #ifdef CONFIG_FAIR_GROUP_SCHED 9165 static void task_set_group_fair(struct task_struct *p) 9166 { 9167 struct sched_entity *se = &p->se; 9168 9169 set_task_rq(p, task_cpu(p)); 9170 se->depth = se->parent ? se->parent->depth + 1 : 0; 9171 } 9172 9173 static void task_move_group_fair(struct task_struct *p) 9174 { 9175 detach_task_cfs_rq(p); 9176 set_task_rq(p, task_cpu(p)); 9177 9178 #ifdef CONFIG_SMP 9179 /* Tell se's cfs_rq has been changed -- migrated */ 9180 p->se.avg.last_update_time = 0; 9181 #endif 9182 attach_task_cfs_rq(p); 9183 } 9184 9185 static void task_change_group_fair(struct task_struct *p, int type) 9186 { 9187 switch (type) { 9188 case TASK_SET_GROUP: 9189 task_set_group_fair(p); 9190 break; 9191 9192 case TASK_MOVE_GROUP: 9193 task_move_group_fair(p); 9194 break; 9195 } 9196 } 9197 9198 void free_fair_sched_group(struct task_group *tg) 9199 { 9200 int i; 9201 9202 destroy_cfs_bandwidth(tg_cfs_bandwidth(tg)); 9203 9204 for_each_possible_cpu(i) { 9205 if (tg->cfs_rq) 9206 kfree(tg->cfs_rq[i]); 9207 if (tg->se) 9208 kfree(tg->se[i]); 9209 } 9210 9211 kfree(tg->cfs_rq); 9212 kfree(tg->se); 9213 } 9214 9215 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 9216 { 9217 struct sched_entity *se; 9218 struct cfs_rq *cfs_rq; 9219 int i; 9220 9221 tg->cfs_rq = kzalloc(sizeof(cfs_rq) * nr_cpu_ids, GFP_KERNEL); 9222 if (!tg->cfs_rq) 9223 goto err; 9224 tg->se = kzalloc(sizeof(se) * nr_cpu_ids, GFP_KERNEL); 9225 if (!tg->se) 9226 goto err; 9227 9228 tg->shares = NICE_0_LOAD; 9229 9230 init_cfs_bandwidth(tg_cfs_bandwidth(tg)); 9231 9232 for_each_possible_cpu(i) { 9233 cfs_rq = kzalloc_node(sizeof(struct cfs_rq), 9234 GFP_KERNEL, cpu_to_node(i)); 9235 if (!cfs_rq) 9236 goto err; 9237 9238 se = kzalloc_node(sizeof(struct sched_entity), 9239 GFP_KERNEL, cpu_to_node(i)); 9240 if (!se) 9241 goto err_free_rq; 9242 9243 init_cfs_rq(cfs_rq); 9244 init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]); 9245 init_entity_runnable_average(se); 9246 } 9247 9248 return 1; 9249 9250 err_free_rq: 9251 kfree(cfs_rq); 9252 err: 9253 return 0; 9254 } 9255 9256 void online_fair_sched_group(struct task_group *tg) 9257 { 9258 struct sched_entity *se; 9259 struct rq *rq; 9260 int i; 9261 9262 for_each_possible_cpu(i) { 9263 rq = cpu_rq(i); 9264 se = tg->se[i]; 9265 9266 raw_spin_lock_irq(&rq->lock); 9267 attach_entity_cfs_rq(se); 9268 sync_throttle(tg, i); 9269 raw_spin_unlock_irq(&rq->lock); 9270 } 9271 } 9272 9273 void unregister_fair_sched_group(struct task_group *tg) 9274 { 9275 unsigned long flags; 9276 struct rq *rq; 9277 int cpu; 9278 9279 for_each_possible_cpu(cpu) { 9280 if (tg->se[cpu]) 9281 remove_entity_load_avg(tg->se[cpu]); 9282 9283 /* 9284 * Only empty task groups can be destroyed; so we can speculatively 9285 * check on_list without danger of it being re-added. 9286 */ 9287 if (!tg->cfs_rq[cpu]->on_list) 9288 continue; 9289 9290 rq = cpu_rq(cpu); 9291 9292 raw_spin_lock_irqsave(&rq->lock, flags); 9293 list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); 9294 raw_spin_unlock_irqrestore(&rq->lock, flags); 9295 } 9296 } 9297 9298 void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, 9299 struct sched_entity *se, int cpu, 9300 struct sched_entity *parent) 9301 { 9302 struct rq *rq = cpu_rq(cpu); 9303 9304 cfs_rq->tg = tg; 9305 cfs_rq->rq = rq; 9306 init_cfs_rq_runtime(cfs_rq); 9307 9308 tg->cfs_rq[cpu] = cfs_rq; 9309 tg->se[cpu] = se; 9310 9311 /* se could be NULL for root_task_group */ 9312 if (!se) 9313 return; 9314 9315 if (!parent) { 9316 se->cfs_rq = &rq->cfs; 9317 se->depth = 0; 9318 } else { 9319 se->cfs_rq = parent->my_q; 9320 se->depth = parent->depth + 1; 9321 } 9322 9323 se->my_q = cfs_rq; 9324 /* guarantee group entities always have weight */ 9325 update_load_set(&se->load, NICE_0_LOAD); 9326 se->parent = parent; 9327 } 9328 9329 static DEFINE_MUTEX(shares_mutex); 9330 9331 int sched_group_set_shares(struct task_group *tg, unsigned long shares) 9332 { 9333 int i; 9334 unsigned long flags; 9335 9336 /* 9337 * We can't change the weight of the root cgroup. 9338 */ 9339 if (!tg->se[0]) 9340 return -EINVAL; 9341 9342 shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES)); 9343 9344 mutex_lock(&shares_mutex); 9345 if (tg->shares == shares) 9346 goto done; 9347 9348 tg->shares = shares; 9349 for_each_possible_cpu(i) { 9350 struct rq *rq = cpu_rq(i); 9351 struct sched_entity *se; 9352 9353 se = tg->se[i]; 9354 /* Propagate contribution to hierarchy */ 9355 raw_spin_lock_irqsave(&rq->lock, flags); 9356 9357 /* Possible calls to update_curr() need rq clock */ 9358 update_rq_clock(rq); 9359 for_each_sched_entity(se) 9360 update_cfs_shares(group_cfs_rq(se)); 9361 raw_spin_unlock_irqrestore(&rq->lock, flags); 9362 } 9363 9364 done: 9365 mutex_unlock(&shares_mutex); 9366 return 0; 9367 } 9368 #else /* CONFIG_FAIR_GROUP_SCHED */ 9369 9370 void free_fair_sched_group(struct task_group *tg) { } 9371 9372 int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent) 9373 { 9374 return 1; 9375 } 9376 9377 void online_fair_sched_group(struct task_group *tg) { } 9378 9379 void unregister_fair_sched_group(struct task_group *tg) { } 9380 9381 #endif /* CONFIG_FAIR_GROUP_SCHED */ 9382 9383 9384 static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task) 9385 { 9386 struct sched_entity *se = &task->se; 9387 unsigned int rr_interval = 0; 9388 9389 /* 9390 * Time slice is 0 for SCHED_OTHER tasks that are on an otherwise 9391 * idle runqueue: 9392 */ 9393 if (rq->cfs.load.weight) 9394 rr_interval = NS_TO_JIFFIES(sched_slice(cfs_rq_of(se), se)); 9395 9396 return rr_interval; 9397 } 9398 9399 /* 9400 * All the scheduling class methods: 9401 */ 9402 const struct sched_class fair_sched_class = { 9403 .next = &idle_sched_class, 9404 .enqueue_task = enqueue_task_fair, 9405 .dequeue_task = dequeue_task_fair, 9406 .yield_task = yield_task_fair, 9407 .yield_to_task = yield_to_task_fair, 9408 9409 .check_preempt_curr = check_preempt_wakeup, 9410 9411 .pick_next_task = pick_next_task_fair, 9412 .put_prev_task = put_prev_task_fair, 9413 9414 #ifdef CONFIG_SMP 9415 .select_task_rq = select_task_rq_fair, 9416 .migrate_task_rq = migrate_task_rq_fair, 9417 9418 .rq_online = rq_online_fair, 9419 .rq_offline = rq_offline_fair, 9420 9421 .task_dead = task_dead_fair, 9422 .set_cpus_allowed = set_cpus_allowed_common, 9423 #endif 9424 9425 .set_curr_task = set_curr_task_fair, 9426 .task_tick = task_tick_fair, 9427 .task_fork = task_fork_fair, 9428 9429 .prio_changed = prio_changed_fair, 9430 .switched_from = switched_from_fair, 9431 .switched_to = switched_to_fair, 9432 9433 .get_rr_interval = get_rr_interval_fair, 9434 9435 .update_curr = update_curr_fair, 9436 9437 #ifdef CONFIG_FAIR_GROUP_SCHED 9438 .task_change_group = task_change_group_fair, 9439 #endif 9440 }; 9441 9442 #ifdef CONFIG_SCHED_DEBUG 9443 void print_cfs_stats(struct seq_file *m, int cpu) 9444 { 9445 struct cfs_rq *cfs_rq; 9446 9447 rcu_read_lock(); 9448 for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq) 9449 print_cfs_rq(m, cpu, cfs_rq); 9450 rcu_read_unlock(); 9451 } 9452 9453 #ifdef CONFIG_NUMA_BALANCING 9454 void show_numa_stats(struct task_struct *p, struct seq_file *m) 9455 { 9456 int node; 9457 unsigned long tsf = 0, tpf = 0, gsf = 0, gpf = 0; 9458 9459 for_each_online_node(node) { 9460 if (p->numa_faults) { 9461 tsf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 0)]; 9462 tpf = p->numa_faults[task_faults_idx(NUMA_MEM, node, 1)]; 9463 } 9464 if (p->numa_group) { 9465 gsf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 0)], 9466 gpf = p->numa_group->faults[task_faults_idx(NUMA_MEM, node, 1)]; 9467 } 9468 print_numa_stats(m, node, tsf, tpf, gsf, gpf); 9469 } 9470 } 9471 #endif /* CONFIG_NUMA_BALANCING */ 9472 #endif /* CONFIG_SCHED_DEBUG */ 9473 9474 __init void init_sched_fair_class(void) 9475 { 9476 #ifdef CONFIG_SMP 9477 open_softirq(SCHED_SOFTIRQ, run_rebalance_domains); 9478 9479 #ifdef CONFIG_NO_HZ_COMMON 9480 nohz.next_balance = jiffies; 9481 zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT); 9482 #endif 9483 #endif /* SMP */ 9484 9485 } 9486