1// SPDX-License-Identifier: GPL-2.0-or-later 2/* 3 * Hierarchical Budget Worst-case Fair Weighted Fair Queueing 4 * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O 5 * scheduler schedules generic entities. The latter can represent 6 * either single bfq queues (associated with processes) or groups of 7 * bfq queues (associated with cgroups). 8 */ 9#include "bfq-iosched.h" 10 11/** 12 * bfq_gt - compare two timestamps. 13 * @a: first ts. 14 * @b: second ts. 15 * 16 * Return @a > @b, dealing with wrapping correctly. 17 */ 18static int bfq_gt(u64 a, u64 b) 19{ 20 return (s64)(a - b) > 0; 21} 22 23static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree) 24{ 25 struct rb_node *node = tree->rb_node; 26 27 return rb_entry(node, struct bfq_entity, rb_node); 28} 29 30static unsigned int bfq_class_idx(struct bfq_entity *entity) 31{ 32 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 33 34 return bfqq ? bfqq->ioprio_class - 1 : 35 BFQ_DEFAULT_GRP_CLASS - 1; 36} 37 38unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd) 39{ 40 return bfqd->busy_queues[0] + bfqd->busy_queues[1] + 41 bfqd->busy_queues[2]; 42} 43 44static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, 45 bool expiration); 46 47static bool bfq_update_parent_budget(struct bfq_entity *next_in_service); 48 49/** 50 * bfq_update_next_in_service - update sd->next_in_service 51 * @sd: sched_data for which to perform the update. 52 * @new_entity: if not NULL, pointer to the entity whose activation, 53 * requeueing or repositioning triggered the invocation of 54 * this function. 55 * @expiration: id true, this function is being invoked after the 56 * expiration of the in-service entity 57 * 58 * This function is called to update sd->next_in_service, which, in 59 * its turn, may change as a consequence of the insertion or 60 * extraction of an entity into/from one of the active trees of 61 * sd. These insertions/extractions occur as a consequence of 62 * activations/deactivations of entities, with some activations being 63 * 'true' activations, and other activations being requeueings (i.e., 64 * implementing the second, requeueing phase of the mechanism used to 65 * reposition an entity in its active tree; see comments on 66 * __bfq_activate_entity and __bfq_requeue_entity for details). In 67 * both the last two activation sub-cases, new_entity points to the 68 * just activated or requeued entity. 69 * 70 * Returns true if sd->next_in_service changes in such a way that 71 * entity->parent may become the next_in_service for its parent 72 * entity. 73 */ 74static bool bfq_update_next_in_service(struct bfq_sched_data *sd, 75 struct bfq_entity *new_entity, 76 bool expiration) 77{ 78 struct bfq_entity *next_in_service = sd->next_in_service; 79 bool parent_sched_may_change = false; 80 bool change_without_lookup = false; 81 82 /* 83 * If this update is triggered by the activation, requeueing 84 * or repositioning of an entity that does not coincide with 85 * sd->next_in_service, then a full lookup in the active tree 86 * can be avoided. In fact, it is enough to check whether the 87 * just-modified entity has the same priority as 88 * sd->next_in_service, is eligible and has a lower virtual 89 * finish time than sd->next_in_service. If this compound 90 * condition holds, then the new entity becomes the new 91 * next_in_service. Otherwise no change is needed. 92 */ 93 if (new_entity && new_entity != sd->next_in_service) { 94 /* 95 * Flag used to decide whether to replace 96 * sd->next_in_service with new_entity. Tentatively 97 * set to true, and left as true if 98 * sd->next_in_service is NULL. 99 */ 100 change_without_lookup = true; 101 102 /* 103 * If there is already a next_in_service candidate 104 * entity, then compare timestamps to decide whether 105 * to replace sd->service_tree with new_entity. 106 */ 107 if (next_in_service) { 108 unsigned int new_entity_class_idx = 109 bfq_class_idx(new_entity); 110 struct bfq_service_tree *st = 111 sd->service_tree + new_entity_class_idx; 112 113 change_without_lookup = 114 (new_entity_class_idx == 115 bfq_class_idx(next_in_service) 116 && 117 !bfq_gt(new_entity->start, st->vtime) 118 && 119 bfq_gt(next_in_service->finish, 120 new_entity->finish)); 121 } 122 123 if (change_without_lookup) 124 next_in_service = new_entity; 125 } 126 127 if (!change_without_lookup) /* lookup needed */ 128 next_in_service = bfq_lookup_next_entity(sd, expiration); 129 130 if (next_in_service) { 131 bool new_budget_triggers_change = 132 bfq_update_parent_budget(next_in_service); 133 134 parent_sched_may_change = !sd->next_in_service || 135 new_budget_triggers_change; 136 } 137 138 sd->next_in_service = next_in_service; 139 140 return parent_sched_may_change; 141} 142 143#ifdef CONFIG_BFQ_GROUP_IOSCHED 144 145struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) 146{ 147 struct bfq_entity *group_entity = bfqq->entity.parent; 148 149 if (!group_entity) 150 group_entity = &bfqq->bfqd->root_group->entity; 151 152 return container_of(group_entity, struct bfq_group, entity); 153} 154 155/* 156 * Returns true if this budget changes may let next_in_service->parent 157 * become the next_in_service entity for its parent entity. 158 */ 159static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) 160{ 161 struct bfq_entity *bfqg_entity; 162 struct bfq_group *bfqg; 163 struct bfq_sched_data *group_sd; 164 bool ret = false; 165 166 group_sd = next_in_service->sched_data; 167 168 bfqg = container_of(group_sd, struct bfq_group, sched_data); 169 /* 170 * bfq_group's my_entity field is not NULL only if the group 171 * is not the root group. We must not touch the root entity 172 * as it must never become an in-service entity. 173 */ 174 bfqg_entity = bfqg->my_entity; 175 if (bfqg_entity) { 176 if (bfqg_entity->budget > next_in_service->budget) 177 ret = true; 178 bfqg_entity->budget = next_in_service->budget; 179 } 180 181 return ret; 182} 183 184/* 185 * This function tells whether entity stops being a candidate for next 186 * service, according to the restrictive definition of the field 187 * next_in_service. In particular, this function is invoked for an 188 * entity that is about to be set in service. 189 * 190 * If entity is a queue, then the entity is no longer a candidate for 191 * next service according to the that definition, because entity is 192 * about to become the in-service queue. This function then returns 193 * true if entity is a queue. 194 * 195 * In contrast, entity could still be a candidate for next service if 196 * it is not a queue, and has more than one active child. In fact, 197 * even if one of its children is about to be set in service, other 198 * active children may still be the next to serve, for the parent 199 * entity, even according to the above definition. As a consequence, a 200 * non-queue entity is not a candidate for next-service only if it has 201 * only one active child. And only if this condition holds, then this 202 * function returns true for a non-queue entity. 203 */ 204static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) 205{ 206 struct bfq_group *bfqg; 207 208 if (bfq_entity_to_bfqq(entity)) 209 return true; 210 211 bfqg = container_of(entity, struct bfq_group, entity); 212 213 /* 214 * The field active_entities does not always contain the 215 * actual number of active children entities: it happens to 216 * not account for the in-service entity in case the latter is 217 * removed from its active tree (which may get done after 218 * invoking the function bfq_no_longer_next_in_service in 219 * bfq_get_next_queue). Fortunately, here, i.e., while 220 * bfq_no_longer_next_in_service is not yet completed in 221 * bfq_get_next_queue, bfq_active_extract has not yet been 222 * invoked, and thus active_entities still coincides with the 223 * actual number of active entities. 224 */ 225 if (bfqg->active_entities == 1) 226 return true; 227 228 return false; 229} 230 231#else /* CONFIG_BFQ_GROUP_IOSCHED */ 232 233struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) 234{ 235 return bfqq->bfqd->root_group; 236} 237 238static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) 239{ 240 return false; 241} 242 243static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) 244{ 245 return true; 246} 247 248#endif /* CONFIG_BFQ_GROUP_IOSCHED */ 249 250/* 251 * Shift for timestamp calculations. This actually limits the maximum 252 * service allowed in one timestamp delta (small shift values increase it), 253 * the maximum total weight that can be used for the queues in the system 254 * (big shift values increase it), and the period of virtual time 255 * wraparounds. 256 */ 257#define WFQ_SERVICE_SHIFT 22 258 259struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) 260{ 261 struct bfq_queue *bfqq = NULL; 262 263 if (!entity->my_sched_data) 264 bfqq = container_of(entity, struct bfq_queue, entity); 265 266 return bfqq; 267} 268 269 270/** 271 * bfq_delta - map service into the virtual time domain. 272 * @service: amount of service. 273 * @weight: scale factor (weight of an entity or weight sum). 274 */ 275static u64 bfq_delta(unsigned long service, unsigned long weight) 276{ 277 return div64_ul((u64)service << WFQ_SERVICE_SHIFT, weight); 278} 279 280/** 281 * bfq_calc_finish - assign the finish time to an entity. 282 * @entity: the entity to act upon. 283 * @service: the service to be charged to the entity. 284 */ 285static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) 286{ 287 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 288 289 entity->finish = entity->start + 290 bfq_delta(service, entity->weight); 291 292 if (bfqq) { 293 bfq_log_bfqq(bfqq->bfqd, bfqq, 294 "calc_finish: serv %lu, w %d", 295 service, entity->weight); 296 bfq_log_bfqq(bfqq->bfqd, bfqq, 297 "calc_finish: start %llu, finish %llu, delta %llu", 298 entity->start, entity->finish, 299 bfq_delta(service, entity->weight)); 300 } 301} 302 303/** 304 * bfq_entity_of - get an entity from a node. 305 * @node: the node field of the entity. 306 * 307 * Convert a node pointer to the relative entity. This is used only 308 * to simplify the logic of some functions and not as the generic 309 * conversion mechanism because, e.g., in the tree walking functions, 310 * the check for a %NULL value would be redundant. 311 */ 312struct bfq_entity *bfq_entity_of(struct rb_node *node) 313{ 314 struct bfq_entity *entity = NULL; 315 316 if (node) 317 entity = rb_entry(node, struct bfq_entity, rb_node); 318 319 return entity; 320} 321 322/** 323 * bfq_extract - remove an entity from a tree. 324 * @root: the tree root. 325 * @entity: the entity to remove. 326 */ 327static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) 328{ 329 entity->tree = NULL; 330 rb_erase(&entity->rb_node, root); 331} 332 333/** 334 * bfq_idle_extract - extract an entity from the idle tree. 335 * @st: the service tree of the owning @entity. 336 * @entity: the entity being removed. 337 */ 338static void bfq_idle_extract(struct bfq_service_tree *st, 339 struct bfq_entity *entity) 340{ 341 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 342 struct rb_node *next; 343 344 if (entity == st->first_idle) { 345 next = rb_next(&entity->rb_node); 346 st->first_idle = bfq_entity_of(next); 347 } 348 349 if (entity == st->last_idle) { 350 next = rb_prev(&entity->rb_node); 351 st->last_idle = bfq_entity_of(next); 352 } 353 354 bfq_extract(&st->idle, entity); 355 356 if (bfqq) 357 list_del(&bfqq->bfqq_list); 358} 359 360/** 361 * bfq_insert - generic tree insertion. 362 * @root: tree root. 363 * @entity: entity to insert. 364 * 365 * This is used for the idle and the active tree, since they are both 366 * ordered by finish time. 367 */ 368static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) 369{ 370 struct bfq_entity *entry; 371 struct rb_node **node = &root->rb_node; 372 struct rb_node *parent = NULL; 373 374 while (*node) { 375 parent = *node; 376 entry = rb_entry(parent, struct bfq_entity, rb_node); 377 378 if (bfq_gt(entry->finish, entity->finish)) 379 node = &parent->rb_left; 380 else 381 node = &parent->rb_right; 382 } 383 384 rb_link_node(&entity->rb_node, parent, node); 385 rb_insert_color(&entity->rb_node, root); 386 387 entity->tree = root; 388} 389 390/** 391 * bfq_update_min - update the min_start field of a entity. 392 * @entity: the entity to update. 393 * @node: one of its children. 394 * 395 * This function is called when @entity may store an invalid value for 396 * min_start due to updates to the active tree. The function assumes 397 * that the subtree rooted at @node (which may be its left or its right 398 * child) has a valid min_start value. 399 */ 400static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) 401{ 402 struct bfq_entity *child; 403 404 if (node) { 405 child = rb_entry(node, struct bfq_entity, rb_node); 406 if (bfq_gt(entity->min_start, child->min_start)) 407 entity->min_start = child->min_start; 408 } 409} 410 411/** 412 * bfq_update_active_node - recalculate min_start. 413 * @node: the node to update. 414 * 415 * @node may have changed position or one of its children may have moved, 416 * this function updates its min_start value. The left and right subtrees 417 * are assumed to hold a correct min_start value. 418 */ 419static void bfq_update_active_node(struct rb_node *node) 420{ 421 struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); 422 423 entity->min_start = entity->start; 424 bfq_update_min(entity, node->rb_right); 425 bfq_update_min(entity, node->rb_left); 426} 427 428/** 429 * bfq_update_active_tree - update min_start for the whole active tree. 430 * @node: the starting node. 431 * 432 * @node must be the deepest modified node after an update. This function 433 * updates its min_start using the values held by its children, assuming 434 * that they did not change, and then updates all the nodes that may have 435 * changed in the path to the root. The only nodes that may have changed 436 * are the ones in the path or their siblings. 437 */ 438static void bfq_update_active_tree(struct rb_node *node) 439{ 440 struct rb_node *parent; 441 442up: 443 bfq_update_active_node(node); 444 445 parent = rb_parent(node); 446 if (!parent) 447 return; 448 449 if (node == parent->rb_left && parent->rb_right) 450 bfq_update_active_node(parent->rb_right); 451 else if (parent->rb_left) 452 bfq_update_active_node(parent->rb_left); 453 454 node = parent; 455 goto up; 456} 457 458/** 459 * bfq_active_insert - insert an entity in the active tree of its 460 * group/device. 461 * @st: the service tree of the entity. 462 * @entity: the entity being inserted. 463 * 464 * The active tree is ordered by finish time, but an extra key is kept 465 * per each node, containing the minimum value for the start times of 466 * its children (and the node itself), so it's possible to search for 467 * the eligible node with the lowest finish time in logarithmic time. 468 */ 469static void bfq_active_insert(struct bfq_service_tree *st, 470 struct bfq_entity *entity) 471{ 472 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 473 struct rb_node *node = &entity->rb_node; 474#ifdef CONFIG_BFQ_GROUP_IOSCHED 475 struct bfq_sched_data *sd = NULL; 476 struct bfq_group *bfqg = NULL; 477 struct bfq_data *bfqd = NULL; 478#endif 479 480 bfq_insert(&st->active, entity); 481 482 if (node->rb_left) 483 node = node->rb_left; 484 else if (node->rb_right) 485 node = node->rb_right; 486 487 bfq_update_active_tree(node); 488 489#ifdef CONFIG_BFQ_GROUP_IOSCHED 490 sd = entity->sched_data; 491 bfqg = container_of(sd, struct bfq_group, sched_data); 492 bfqd = (struct bfq_data *)bfqg->bfqd; 493#endif 494 if (bfqq) 495 list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); 496#ifdef CONFIG_BFQ_GROUP_IOSCHED 497 if (bfqg != bfqd->root_group) 498 bfqg->active_entities++; 499#endif 500} 501 502/** 503 * bfq_ioprio_to_weight - calc a weight from an ioprio. 504 * @ioprio: the ioprio value to convert. 505 */ 506unsigned short bfq_ioprio_to_weight(int ioprio) 507{ 508 return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; 509} 510 511/** 512 * bfq_weight_to_ioprio - calc an ioprio from a weight. 513 * @weight: the weight value to convert. 514 * 515 * To preserve as much as possible the old only-ioprio user interface, 516 * 0 is used as an escape ioprio value for weights (numerically) equal or 517 * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF. 518 */ 519static unsigned short bfq_weight_to_ioprio(int weight) 520{ 521 return max_t(int, 0, 522 IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight); 523} 524 525static void bfq_get_entity(struct bfq_entity *entity) 526{ 527 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 528 529 if (bfqq) { 530 bfqq->ref++; 531 bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", 532 bfqq, bfqq->ref); 533 } 534} 535 536/** 537 * bfq_find_deepest - find the deepest node that an extraction can modify. 538 * @node: the node being removed. 539 * 540 * Do the first step of an extraction in an rb tree, looking for the 541 * node that will replace @node, and returning the deepest node that 542 * the following modifications to the tree can touch. If @node is the 543 * last node in the tree return %NULL. 544 */ 545static struct rb_node *bfq_find_deepest(struct rb_node *node) 546{ 547 struct rb_node *deepest; 548 549 if (!node->rb_right && !node->rb_left) 550 deepest = rb_parent(node); 551 else if (!node->rb_right) 552 deepest = node->rb_left; 553 else if (!node->rb_left) 554 deepest = node->rb_right; 555 else { 556 deepest = rb_next(node); 557 if (deepest->rb_right) 558 deepest = deepest->rb_right; 559 else if (rb_parent(deepest) != node) 560 deepest = rb_parent(deepest); 561 } 562 563 return deepest; 564} 565 566/** 567 * bfq_active_extract - remove an entity from the active tree. 568 * @st: the service_tree containing the tree. 569 * @entity: the entity being removed. 570 */ 571static void bfq_active_extract(struct bfq_service_tree *st, 572 struct bfq_entity *entity) 573{ 574 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 575 struct rb_node *node; 576#ifdef CONFIG_BFQ_GROUP_IOSCHED 577 struct bfq_sched_data *sd = NULL; 578 struct bfq_group *bfqg = NULL; 579 struct bfq_data *bfqd = NULL; 580#endif 581 582 node = bfq_find_deepest(&entity->rb_node); 583 bfq_extract(&st->active, entity); 584 585 if (node) 586 bfq_update_active_tree(node); 587 588#ifdef CONFIG_BFQ_GROUP_IOSCHED 589 sd = entity->sched_data; 590 bfqg = container_of(sd, struct bfq_group, sched_data); 591 bfqd = (struct bfq_data *)bfqg->bfqd; 592#endif 593 if (bfqq) 594 list_del(&bfqq->bfqq_list); 595#ifdef CONFIG_BFQ_GROUP_IOSCHED 596 if (bfqg != bfqd->root_group) 597 bfqg->active_entities--; 598#endif 599} 600 601/** 602 * bfq_idle_insert - insert an entity into the idle tree. 603 * @st: the service tree containing the tree. 604 * @entity: the entity to insert. 605 */ 606static void bfq_idle_insert(struct bfq_service_tree *st, 607 struct bfq_entity *entity) 608{ 609 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 610 struct bfq_entity *first_idle = st->first_idle; 611 struct bfq_entity *last_idle = st->last_idle; 612 613 if (!first_idle || bfq_gt(first_idle->finish, entity->finish)) 614 st->first_idle = entity; 615 if (!last_idle || bfq_gt(entity->finish, last_idle->finish)) 616 st->last_idle = entity; 617 618 bfq_insert(&st->idle, entity); 619 620 if (bfqq) 621 list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); 622} 623 624/** 625 * bfq_forget_entity - do not consider entity any longer for scheduling 626 * @st: the service tree. 627 * @entity: the entity being removed. 628 * @is_in_service: true if entity is currently the in-service entity. 629 * 630 * Forget everything about @entity. In addition, if entity represents 631 * a queue, and the latter is not in service, then release the service 632 * reference to the queue (the one taken through bfq_get_entity). In 633 * fact, in this case, there is really no more service reference to 634 * the queue, as the latter is also outside any service tree. If, 635 * instead, the queue is in service, then __bfq_bfqd_reset_in_service 636 * will take care of putting the reference when the queue finally 637 * stops being served. 638 */ 639static void bfq_forget_entity(struct bfq_service_tree *st, 640 struct bfq_entity *entity, 641 bool is_in_service) 642{ 643 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 644 645 entity->on_st_or_in_serv = false; 646 st->wsum -= entity->weight; 647 if (bfqq && !is_in_service) 648 bfq_put_queue(bfqq); 649} 650 651/** 652 * bfq_put_idle_entity - release the idle tree ref of an entity. 653 * @st: service tree for the entity. 654 * @entity: the entity being released. 655 */ 656void bfq_put_idle_entity(struct bfq_service_tree *st, struct bfq_entity *entity) 657{ 658 bfq_idle_extract(st, entity); 659 bfq_forget_entity(st, entity, 660 entity == entity->sched_data->in_service_entity); 661} 662 663/** 664 * bfq_forget_idle - update the idle tree if necessary. 665 * @st: the service tree to act upon. 666 * 667 * To preserve the global O(log N) complexity we only remove one entry here; 668 * as the idle tree will not grow indefinitely this can be done safely. 669 */ 670static void bfq_forget_idle(struct bfq_service_tree *st) 671{ 672 struct bfq_entity *first_idle = st->first_idle; 673 struct bfq_entity *last_idle = st->last_idle; 674 675 if (RB_EMPTY_ROOT(&st->active) && last_idle && 676 !bfq_gt(last_idle->finish, st->vtime)) { 677 /* 678 * Forget the whole idle tree, increasing the vtime past 679 * the last finish time of idle entities. 680 */ 681 st->vtime = last_idle->finish; 682 } 683 684 if (first_idle && !bfq_gt(first_idle->finish, st->vtime)) 685 bfq_put_idle_entity(st, first_idle); 686} 687 688struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity) 689{ 690 struct bfq_sched_data *sched_data = entity->sched_data; 691 unsigned int idx = bfq_class_idx(entity); 692 693 return sched_data->service_tree + idx; 694} 695 696/* 697 * Update weight and priority of entity. If update_class_too is true, 698 * then update the ioprio_class of entity too. 699 * 700 * The reason why the update of ioprio_class is controlled through the 701 * last parameter is as follows. Changing the ioprio class of an 702 * entity implies changing the destination service trees for that 703 * entity. If such a change occurred when the entity is already on one 704 * of the service trees for its previous class, then the state of the 705 * entity would become more complex: none of the new possible service 706 * trees for the entity, according to bfq_entity_service_tree(), would 707 * match any of the possible service trees on which the entity 708 * is. Complex operations involving these trees, such as entity 709 * activations and deactivations, should take into account this 710 * additional complexity. To avoid this issue, this function is 711 * invoked with update_class_too unset in the points in the code where 712 * entity may happen to be on some tree. 713 */ 714struct bfq_service_tree * 715__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, 716 struct bfq_entity *entity, 717 bool update_class_too) 718{ 719 struct bfq_service_tree *new_st = old_st; 720 721 if (entity->prio_changed) { 722 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 723 unsigned int prev_weight, new_weight; 724 struct bfq_data *bfqd = NULL; 725 struct rb_root_cached *root; 726#ifdef CONFIG_BFQ_GROUP_IOSCHED 727 struct bfq_sched_data *sd; 728 struct bfq_group *bfqg; 729#endif 730 731 if (bfqq) 732 bfqd = bfqq->bfqd; 733#ifdef CONFIG_BFQ_GROUP_IOSCHED 734 else { 735 sd = entity->my_sched_data; 736 bfqg = container_of(sd, struct bfq_group, sched_data); 737 bfqd = (struct bfq_data *)bfqg->bfqd; 738 } 739#endif 740 741 /* Matches the smp_wmb() in bfq_group_set_weight. */ 742 smp_rmb(); 743 old_st->wsum -= entity->weight; 744 745 if (entity->new_weight != entity->orig_weight) { 746 if (entity->new_weight < BFQ_MIN_WEIGHT || 747 entity->new_weight > BFQ_MAX_WEIGHT) { 748 pr_crit("update_weight_prio: new_weight %d\n", 749 entity->new_weight); 750 if (entity->new_weight < BFQ_MIN_WEIGHT) 751 entity->new_weight = BFQ_MIN_WEIGHT; 752 else 753 entity->new_weight = BFQ_MAX_WEIGHT; 754 } 755 entity->orig_weight = entity->new_weight; 756 if (bfqq) 757 bfqq->ioprio = 758 bfq_weight_to_ioprio(entity->orig_weight); 759 } 760 761 if (bfqq && update_class_too) 762 bfqq->ioprio_class = bfqq->new_ioprio_class; 763 764 /* 765 * Reset prio_changed only if the ioprio_class change 766 * is not pending any longer. 767 */ 768 if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class) 769 entity->prio_changed = 0; 770 771 /* 772 * NOTE: here we may be changing the weight too early, 773 * this will cause unfairness. The correct approach 774 * would have required additional complexity to defer 775 * weight changes to the proper time instants (i.e., 776 * when entity->finish <= old_st->vtime). 777 */ 778 new_st = bfq_entity_service_tree(entity); 779 780 prev_weight = entity->weight; 781 new_weight = entity->orig_weight * 782 (bfqq ? bfqq->wr_coeff : 1); 783 /* 784 * If the weight of the entity changes, and the entity is a 785 * queue, remove the entity from its old weight counter (if 786 * there is a counter associated with the entity). 787 */ 788 if (prev_weight != new_weight && bfqq) { 789 root = &bfqd->queue_weights_tree; 790 __bfq_weights_tree_remove(bfqd, bfqq, root); 791 } 792 entity->weight = new_weight; 793 /* 794 * Add the entity, if it is not a weight-raised queue, 795 * to the counter associated with its new weight. 796 */ 797 if (prev_weight != new_weight && bfqq && bfqq->wr_coeff == 1) { 798 /* If we get here, root has been initialized. */ 799 bfq_weights_tree_add(bfqd, bfqq, root); 800 } 801 802 new_st->wsum += entity->weight; 803 804 if (new_st != old_st) 805 entity->start = new_st->vtime; 806 } 807 808 return new_st; 809} 810 811/** 812 * bfq_bfqq_served - update the scheduler status after selection for 813 * service. 814 * @bfqq: the queue being served. 815 * @served: bytes to transfer. 816 * 817 * NOTE: this can be optimized, as the timestamps of upper level entities 818 * are synchronized every time a new bfqq is selected for service. By now, 819 * we keep it to better check consistency. 820 */ 821void bfq_bfqq_served(struct bfq_queue *bfqq, int served) 822{ 823 struct bfq_entity *entity = &bfqq->entity; 824 struct bfq_service_tree *st; 825 826 if (!bfqq->service_from_backlogged) 827 bfqq->first_IO_time = jiffies; 828 829 if (bfqq->wr_coeff > 1) 830 bfqq->service_from_wr += served; 831 832 bfqq->service_from_backlogged += served; 833 for_each_entity(entity) { 834 st = bfq_entity_service_tree(entity); 835 836 entity->service += served; 837 838 st->vtime += bfq_delta(served, st->wsum); 839 bfq_forget_idle(st); 840 } 841 bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served); 842} 843 844/** 845 * bfq_bfqq_charge_time - charge an amount of service equivalent to the length 846 * of the time interval during which bfqq has been in 847 * service. 848 * @bfqd: the device 849 * @bfqq: the queue that needs a service update. 850 * @time_ms: the amount of time during which the queue has received service 851 * 852 * If a queue does not consume its budget fast enough, then providing 853 * the queue with service fairness may impair throughput, more or less 854 * severely. For this reason, queues that consume their budget slowly 855 * are provided with time fairness instead of service fairness. This 856 * goal is achieved through the BFQ scheduling engine, even if such an 857 * engine works in the service, and not in the time domain. The trick 858 * is charging these queues with an inflated amount of service, equal 859 * to the amount of service that they would have received during their 860 * service slot if they had been fast, i.e., if their requests had 861 * been dispatched at a rate equal to the estimated peak rate. 862 * 863 * It is worth noting that time fairness can cause important 864 * distortions in terms of bandwidth distribution, on devices with 865 * internal queueing. The reason is that I/O requests dispatched 866 * during the service slot of a queue may be served after that service 867 * slot is finished, and may have a total processing time loosely 868 * correlated with the duration of the service slot. This is 869 * especially true for short service slots. 870 */ 871void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq, 872 unsigned long time_ms) 873{ 874 struct bfq_entity *entity = &bfqq->entity; 875 unsigned long timeout_ms = jiffies_to_msecs(bfq_timeout); 876 unsigned long bounded_time_ms = min(time_ms, timeout_ms); 877 int serv_to_charge_for_time = 878 (bfqd->bfq_max_budget * bounded_time_ms) / timeout_ms; 879 int tot_serv_to_charge = max(serv_to_charge_for_time, entity->service); 880 881 /* Increase budget to avoid inconsistencies */ 882 if (tot_serv_to_charge > entity->budget) 883 entity->budget = tot_serv_to_charge; 884 885 bfq_bfqq_served(bfqq, 886 max_t(int, 0, tot_serv_to_charge - entity->service)); 887} 888 889static void bfq_update_fin_time_enqueue(struct bfq_entity *entity, 890 struct bfq_service_tree *st, 891 bool backshifted) 892{ 893 struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); 894 895 /* 896 * When this function is invoked, entity is not in any service 897 * tree, then it is safe to invoke next function with the last 898 * parameter set (see the comments on the function). 899 */ 900 st = __bfq_entity_update_weight_prio(st, entity, true); 901 bfq_calc_finish(entity, entity->budget); 902 903 /* 904 * If some queues enjoy backshifting for a while, then their 905 * (virtual) finish timestamps may happen to become lower and 906 * lower than the system virtual time. In particular, if 907 * these queues often happen to be idle for short time 908 * periods, and during such time periods other queues with 909 * higher timestamps happen to be busy, then the backshifted 910 * timestamps of the former queues can become much lower than 911 * the system virtual time. In fact, to serve the queues with 912 * higher timestamps while the ones with lower timestamps are 913 * idle, the system virtual time may be pushed-up to much 914 * higher values than the finish timestamps of the idle 915 * queues. As a consequence, the finish timestamps of all new 916 * or newly activated queues may end up being much larger than 917 * those of lucky queues with backshifted timestamps. The 918 * latter queues may then monopolize the device for a lot of 919 * time. This would simply break service guarantees. 920 * 921 * To reduce this problem, push up a little bit the 922 * backshifted timestamps of the queue associated with this 923 * entity (only a queue can happen to have the backshifted 924 * flag set): just enough to let the finish timestamp of the 925 * queue be equal to the current value of the system virtual 926 * time. This may introduce a little unfairness among queues 927 * with backshifted timestamps, but it does not break 928 * worst-case fairness guarantees. 929 * 930 * As a special case, if bfqq is weight-raised, push up 931 * timestamps much less, to keep very low the probability that 932 * this push up causes the backshifted finish timestamps of 933 * weight-raised queues to become higher than the backshifted 934 * finish timestamps of non weight-raised queues. 935 */ 936 if (backshifted && bfq_gt(st->vtime, entity->finish)) { 937 unsigned long delta = st->vtime - entity->finish; 938 939 if (bfqq) 940 delta /= bfqq->wr_coeff; 941 942 entity->start += delta; 943 entity->finish += delta; 944 } 945 946 bfq_active_insert(st, entity); 947} 948 949/** 950 * __bfq_activate_entity - handle activation of entity. 951 * @entity: the entity being activated. 952 * @non_blocking_wait_rq: true if entity was waiting for a request 953 * 954 * Called for a 'true' activation, i.e., if entity is not active and 955 * one of its children receives a new request. 956 * 957 * Basically, this function updates the timestamps of entity and 958 * inserts entity into its active tree, after possibly extracting it 959 * from its idle tree. 960 */ 961static void __bfq_activate_entity(struct bfq_entity *entity, 962 bool non_blocking_wait_rq) 963{ 964 struct bfq_service_tree *st = bfq_entity_service_tree(entity); 965 bool backshifted = false; 966 unsigned long long min_vstart; 967 968 /* See comments on bfq_fqq_update_budg_for_activation */ 969 if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) { 970 backshifted = true; 971 min_vstart = entity->finish; 972 } else 973 min_vstart = st->vtime; 974 975 if (entity->tree == &st->idle) { 976 /* 977 * Must be on the idle tree, bfq_idle_extract() will 978 * check for that. 979 */ 980 bfq_idle_extract(st, entity); 981 entity->start = bfq_gt(min_vstart, entity->finish) ? 982 min_vstart : entity->finish; 983 } else { 984 /* 985 * The finish time of the entity may be invalid, and 986 * it is in the past for sure, otherwise the queue 987 * would have been on the idle tree. 988 */ 989 entity->start = min_vstart; 990 st->wsum += entity->weight; 991 /* 992 * entity is about to be inserted into a service tree, 993 * and then set in service: get a reference to make 994 * sure entity does not disappear until it is no 995 * longer in service or scheduled for service. 996 */ 997 bfq_get_entity(entity); 998 999 entity->on_st_or_in_serv = true; 1000 }
1001 1002#ifdef CONFIG_BFQ_GROUP_IOSCHED 1003 if (!bfq_entity_to_bfqq(entity)) { /* bfq_group */ 1004 struct bfq_group *bfqg = 1005 container_of(entity, struct bfq_group, entity); 1006 struct bfq_data *bfqd = bfqg->bfqd; 1007 1008 if (!entity->in_groups_with_pending_reqs) { 1009 entity->in_groups_with_pending_reqs = true; 1010 bfqd->num_groups_with_pending_reqs++; 1011 } 1012 } 1013#endif 1014 1015 bfq_update_fin_time_enqueue(entity, st, backshifted); 1016} 1017 1018/** 1019 * __bfq_requeue_entity - handle requeueing or repositioning of an entity. 1020 * @entity: the entity being requeued or repositioned. 1021 * 1022 * Requeueing is needed if this entity stops being served, which 1023 * happens if a leaf descendant entity has expired. On the other hand, 1024 * repositioning is needed if the next_inservice_entity for the child 1025 * entity has changed. See the comments inside the function for 1026 * details. 1027 * 1028 * Basically, this function: 1) removes entity from its active tree if 1029 * present there, 2) updates the timestamps of entity and 3) inserts 1030 * entity back into its active tree (in the new, right position for 1031 * the new values of the timestamps). 1032 */ 1033static void __bfq_requeue_entity(struct bfq_entity *entity) 1034{ 1035 struct bfq_sched_data *sd = entity->sched_data; 1036 struct bfq_service_tree *st = bfq_entity_service_tree(entity); 1037 1038 if (entity == sd->in_service_entity) { 1039 /* 1040 * We are requeueing the current in-service entity, 1041 * which may have to be done for one of the following 1042 * reasons: 1043 * - entity represents the in-service queue, and the 1044 * in-service queue is being requeued after an 1045 * expiration; 1046 * - entity represents a group, and its budget has 1047 * changed because one of its child entities has 1048 * just been either activated or requeued for some 1049 * reason; the timestamps of the entity need then to 1050 * be updated, and the entity needs to be enqueued 1051 * or repositioned accordingly. 1052 * 1053 * In particular, before requeueing, the start time of 1054 * the entity must be moved forward to account for the 1055 * service that the entity has received while in 1056 * service. This is done by the next instructions. The 1057 * finish time will then be updated according to this 1058 * new value of the start time, and to the budget of 1059 * the entity. 1060 */ 1061 bfq_calc_finish(entity, entity->service); 1062 entity->start = entity->finish; 1063 /* 1064 * In addition, if the entity had more than one child 1065 * when set in service, then it was not extracted from 1066 * the active tree. This implies that the position of 1067 * the entity in the active tree may need to be 1068 * changed now, because we have just updated the start 1069 * time of the entity, and we will update its finish 1070 * time in a moment (the requeueing is then, more 1071 * precisely, a repositioning in this case). To 1072 * implement this repositioning, we: 1) dequeue the 1073 * entity here, 2) update the finish time and requeue 1074 * the entity according to the new timestamps below. 1075 */ 1076 if (entity->tree) 1077 bfq_active_extract(st, entity); 1078 } else { /* The entity is already active, and not in service */ 1079 /* 1080 * In this case, this function gets called only if the 1081 * next_in_service entity below this entity has 1082 * changed, and this change has caused the budget of 1083 * this entity to change, which, finally implies that 1084 * the finish time of this entity must be 1085 * updated. Such an update may cause the scheduling, 1086 * i.e., the position in the active tree, of this 1087 * entity to change. We handle this change by: 1) 1088 * dequeueing the entity here, 2) updating the finish 1089 * time and requeueing the entity according to the new 1090 * timestamps below. This is the same approach as the 1091 * non-extracted-entity sub-case above. 1092 */ 1093 bfq_active_extract(st, entity); 1094 } 1095 1096 bfq_update_fin_time_enqueue(entity, st, false); 1097} 1098 1099static void __bfq_activate_requeue_entity(struct bfq_entity *entity, 1100 struct bfq_sched_data *sd, 1101 bool non_blocking_wait_rq) 1102{ 1103 struct bfq_service_tree *st = bfq_entity_service_tree(entity); 1104 1105 if (sd->in_service_entity == entity || entity->tree == &st->active) 1106 /* 1107 * in service or already queued on the active tree, 1108 * requeue or reposition 1109 */ 1110 __bfq_requeue_entity(entity); 1111 else 1112 /* 1113 * Not in service and not queued on its active tree: 1114 * the activity is idle and this is a true activation. 1115 */ 1116 __bfq_activate_entity(entity, non_blocking_wait_rq); 1117} 1118 1119 1120/** 1121 * bfq_activate_requeue_entity - activate or requeue an entity representing a 1122 * bfq_queue, and activate, requeue or reposition 1123 * all ancestors for which such an update becomes 1124 * necessary. 1125 * @entity: the entity to activate. 1126 * @non_blocking_wait_rq: true if this entity was waiting for a request 1127 * @requeue: true if this is a requeue, which implies that bfqq is 1128 * being expired; thus ALL its ancestors stop being served and must 1129 * therefore be requeued 1130 * @expiration: true if this function is being invoked in the expiration path 1131 * of the in-service queue 1132 */ 1133static void bfq_activate_requeue_entity(struct bfq_entity *entity, 1134 bool non_blocking_wait_rq, 1135 bool requeue, bool expiration) 1136{ 1137 struct bfq_sched_data *sd; 1138 1139 for_each_entity(entity) { 1140 sd = entity->sched_data; 1141 __bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq); 1142 1143 if (!bfq_update_next_in_service(sd, entity, expiration) && 1144 !requeue) 1145 break; 1146 } 1147} 1148 1149/** 1150 * __bfq_deactivate_entity - update sched_data and service trees for 1151 * entity, so as to represent entity as inactive 1152 * @entity: the entity being deactivated. 1153 * @ins_into_idle_tree: if false, the entity will not be put into the 1154 * idle tree. 1155 * 1156 * If necessary and allowed, puts entity into the idle tree. NOTE: 1157 * entity may be on no tree if in service. 1158 */ 1159bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree) 1160{ 1161 struct bfq_sched_data *sd = entity->sched_data; 1162 struct bfq_service_tree *st; 1163 bool is_in_service; 1164 1165 if (!entity->on_st_or_in_serv) /* 1166 * entity never activated, or 1167 * already inactive 1168 */ 1169 return false; 1170 1171 /* 1172 * If we get here, then entity is active, which implies that 1173 * bfq_group_set_parent has already been invoked for the group 1174 * represented by entity. Therefore, the field 1175 * entity->sched_data has been set, and we can safely use it. 1176 */ 1177 st = bfq_entity_service_tree(entity); 1178 is_in_service = entity == sd->in_service_entity; 1179 1180 bfq_calc_finish(entity, entity->service); 1181 1182 if (is_in_service) 1183 sd->in_service_entity = NULL; 1184 else 1185 /* 1186 * Non in-service entity: nobody will take care of 1187 * resetting its service counter on expiration. Do it 1188 * now. 1189 */ 1190 entity->service = 0; 1191 1192 if (entity->tree == &st->active) 1193 bfq_active_extract(st, entity); 1194 else if (!is_in_service && entity->tree == &st->idle) 1195 bfq_idle_extract(st, entity); 1196 1197 if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime)) 1198 bfq_forget_entity(st, entity, is_in_service); 1199 else 1200 bfq_idle_insert(st, entity); 1201 1202 return true; 1203} 1204 1205/** 1206 * bfq_deactivate_entity - deactivate an entity representing a bfq_queue. 1207 * @entity: the entity to deactivate. 1208 * @ins_into_idle_tree: true if the entity can be put into the idle tree 1209 * @expiration: true if this function is being invoked in the expiration path 1210 * of the in-service queue 1211 */ 1212static void bfq_deactivate_entity(struct bfq_entity *entity, 1213 bool ins_into_idle_tree, 1214 bool expiration) 1215{ 1216 struct bfq_sched_data *sd; 1217 struct bfq_entity *parent = NULL; 1218 1219 for_each_entity_safe(entity, parent) { 1220 sd = entity->sched_data; 1221 1222 if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) { 1223 /* 1224 * entity is not in any tree any more, so 1225 * this deactivation is a no-op, and there is 1226 * nothing to change for upper-level entities 1227 * (in case of expiration, this can never 1228 * happen). 1229 */ 1230 return; 1231 } 1232 1233 if (sd->next_in_service == entity) 1234 /* 1235 * entity was the next_in_service entity, 1236 * then, since entity has just been 1237 * deactivated, a new one must be found. 1238 */ 1239 bfq_update_next_in_service(sd, NULL, expiration); 1240 1241 if (sd->next_in_service || sd->in_service_entity) { 1242 /* 1243 * The parent entity is still active, because 1244 * either next_in_service or in_service_entity 1245 * is not NULL. So, no further upwards 1246 * deactivation must be performed. Yet, 1247 * next_in_service has changed. Then the 1248 * schedule does need to be updated upwards. 1249 * 1250 * NOTE If in_service_entity is not NULL, then 1251 * next_in_service may happen to be NULL, 1252 * although the parent entity is evidently 1253 * active. This happens if 1) the entity 1254 * pointed by in_service_entity is the only 1255 * active entity in the parent entity, and 2) 1256 * according to the definition of 1257 * next_in_service, the in_service_entity 1258 * cannot be considered as 1259 * next_in_service. See the comments on the 1260 * definition of next_in_service for details. 1261 */ 1262 break; 1263 } 1264 1265 /* 1266 * If we get here, then the parent is no more 1267 * backlogged and we need to propagate the 1268 * deactivation upwards. Thus let the loop go on. 1269 */ 1270 1271 /* 1272 * Also let parent be queued into the idle tree on 1273 * deactivation, to preserve service guarantees, and 1274 * assuming that who invoked this function does not 1275 * need parent entities too to be removed completely. 1276 */ 1277 ins_into_idle_tree = true; 1278 } 1279 1280 /* 1281 * If the deactivation loop is fully executed, then there are 1282 * no more entities to touch and next loop is not executed at 1283 * all. Otherwise, requeue remaining entities if they are 1284 * about to stop receiving service, or reposition them if this 1285 * is not the case. 1286 */ 1287 entity = parent; 1288 for_each_entity(entity) { 1289 /* 1290 * Invoke __bfq_requeue_entity on entity, even if 1291 * already active, to requeue/reposition it in the 1292 * active tree (because sd->next_in_service has 1293 * changed) 1294 */ 1295 __bfq_requeue_entity(entity); 1296 1297 sd = entity->sched_data; 1298 if (!bfq_update_next_in_service(sd, entity, expiration) && 1299 !expiration) 1300 /* 1301 * next_in_service unchanged or not causing 1302 * any change in entity->parent->sd, and no 1303 * requeueing needed for expiration: stop 1304 * here. 1305 */ 1306 break; 1307 } 1308} 1309 1310/** 1311 * bfq_calc_vtime_jump - compute the value to which the vtime should jump, 1312 * if needed, to have at least one entity eligible. 1313 * @st: the service tree to act upon. 1314 * 1315 * Assumes that st is not empty. 1316 */ 1317static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st) 1318{ 1319 struct bfq_entity *root_entity = bfq_root_active_entity(&st->active); 1320 1321 if (bfq_gt(root_entity->min_start, st->vtime)) 1322 return root_entity->min_start; 1323 1324 return st->vtime; 1325} 1326 1327static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value) 1328{ 1329 if (new_value > st->vtime) { 1330 st->vtime = new_value; 1331 bfq_forget_idle(st); 1332 } 1333} 1334 1335/** 1336 * bfq_first_active_entity - find the eligible entity with 1337 * the smallest finish time 1338 * @st: the service tree to select from. 1339 * @vtime: the system virtual to use as a reference for eligibility 1340 * 1341 * This function searches the first schedulable entity, starting from the 1342 * root of the tree and going on the left every time on this side there is 1343 * a subtree with at least one eligible (start <= vtime) entity. The path on 1344 * the right is followed only if a) the left subtree contains no eligible 1345 * entities and b) no eligible entity has been found yet. 1346 */ 1347static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st, 1348 u64 vtime) 1349{ 1350 struct bfq_entity *entry, *first = NULL; 1351 struct rb_node *node = st->active.rb_node; 1352 1353 while (node) { 1354 entry = rb_entry(node, struct bfq_entity, rb_node); 1355left: 1356 if (!bfq_gt(entry->start, vtime)) 1357 first = entry; 1358 1359 if (node->rb_left) { 1360 entry = rb_entry(node->rb_left, 1361 struct bfq_entity, rb_node); 1362 if (!bfq_gt(entry->min_start, vtime)) { 1363 node = node->rb_left; 1364 goto left; 1365 } 1366 } 1367 if (first) 1368 break; 1369 node = node->rb_right; 1370 } 1371 1372 return first; 1373} 1374 1375/** 1376 * __bfq_lookup_next_entity - return the first eligible entity in @st. 1377 * @st: the service tree. 1378 * 1379 * If there is no in-service entity for the sched_data st belongs to, 1380 * then return the entity that will be set in service if: 1381 * 1) the parent entity this st belongs to is set in service; 1382 * 2) no entity belonging to such parent entity undergoes a state change 1383 * that would influence the timestamps of the entity (e.g., becomes idle, 1384 * becomes backlogged, changes its budget, ...). 1385 * 1386 * In this first case, update the virtual time in @st too (see the 1387 * comments on this update inside the function). 1388 * 1389 * In contrast, if there is an in-service entity, then return the 1390 * entity that would be set in service if not only the above 1391 * conditions, but also the next one held true: the currently 1392 * in-service entity, on expiration, 1393 * 1) gets a finish time equal to the current one, or 1394 * 2) is not eligible any more, or 1395 * 3) is idle. 1396 */ 1397static struct bfq_entity * 1398__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service) 1399{ 1400 struct bfq_entity *entity; 1401 u64 new_vtime; 1402 1403 if (RB_EMPTY_ROOT(&st->active)) 1404 return NULL; 1405 1406 /* 1407 * Get the value of the system virtual time for which at 1408 * least one entity is eligible. 1409 */ 1410 new_vtime = bfq_calc_vtime_jump(st); 1411 1412 /* 1413 * If there is no in-service entity for the sched_data this 1414 * active tree belongs to, then push the system virtual time 1415 * up to the value that guarantees that at least one entity is 1416 * eligible. If, instead, there is an in-service entity, then 1417 * do not make any such update, because there is already an 1418 * eligible entity, namely the in-service one (even if the 1419 * entity is not on st, because it was extracted when set in 1420 * service). 1421 */ 1422 if (!in_service) 1423 bfq_update_vtime(st, new_vtime); 1424 1425 entity = bfq_first_active_entity(st, new_vtime); 1426 1427 return entity; 1428} 1429 1430/** 1431 * bfq_lookup_next_entity - return the first eligible entity in @sd. 1432 * @sd: the sched_data. 1433 * @expiration: true if we are on the expiration path of the in-service queue 1434 * 1435 * This function is invoked when there has been a change in the trees 1436 * for sd, and we need to know what is the new next entity to serve 1437 * after this change. 1438 */ 1439static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, 1440 bool expiration) 1441{ 1442 struct bfq_service_tree *st = sd->service_tree; 1443 struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1); 1444 struct bfq_entity *entity = NULL; 1445 int class_idx = 0; 1446 1447 /* 1448 * Choose from idle class, if needed to guarantee a minimum 1449 * bandwidth to this class (and if there is some active entity 1450 * in idle class). This should also mitigate 1451 * priority-inversion problems in case a low priority task is 1452 * holding file system resources. 1453 */ 1454 if (time_is_before_jiffies(sd->bfq_class_idle_last_service + 1455 BFQ_CL_IDLE_TIMEOUT)) { 1456 if (!RB_EMPTY_ROOT(&idle_class_st->active)) 1457 class_idx = BFQ_IOPRIO_CLASSES - 1; 1458 /* About to be served if backlogged, or not yet backlogged */ 1459 sd->bfq_class_idle_last_service = jiffies; 1460 } 1461 1462 /* 1463 * Find the next entity to serve for the highest-priority 1464 * class, unless the idle class needs to be served. 1465 */ 1466 for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) { 1467 /* 1468 * If expiration is true, then bfq_lookup_next_entity 1469 * is being invoked as a part of the expiration path 1470 * of the in-service queue. In this case, even if 1471 * sd->in_service_entity is not NULL, 1472 * sd->in_service_entity at this point is actually not 1473 * in service any more, and, if needed, has already 1474 * been properly queued or requeued into the right 1475 * tree. The reason why sd->in_service_entity is still 1476 * not NULL here, even if expiration is true, is that 1477 * sd->in_service_entity is reset as a last step in the 1478 * expiration path. So, if expiration is true, tell 1479 * __bfq_lookup_next_entity that there is no 1480 * sd->in_service_entity. 1481 */ 1482 entity = __bfq_lookup_next_entity(st + class_idx, 1483 sd->in_service_entity && 1484 !expiration); 1485 1486 if (entity) 1487 break; 1488 } 1489 1490 if (!entity) 1491 return NULL; 1492 1493 return entity; 1494} 1495 1496bool next_queue_may_preempt(struct bfq_data *bfqd) 1497{ 1498 struct bfq_sched_data *sd = &bfqd->root_group->sched_data; 1499 1500 return sd->next_in_service != sd->in_service_entity; 1501} 1502 1503/* 1504 * Get next queue for service. 1505 */ 1506struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) 1507{ 1508 struct bfq_entity *entity = NULL; 1509 struct bfq_sched_data *sd; 1510 struct bfq_queue *bfqq; 1511 1512 if (bfq_tot_busy_queues(bfqd) == 0) 1513 return NULL; 1514 1515 /* 1516 * Traverse the path from the root to the leaf entity to 1517 * serve. Set in service all the entities visited along the 1518 * way. 1519 */ 1520 sd = &bfqd->root_group->sched_data; 1521 for (; sd ; sd = entity->my_sched_data) { 1522 /* 1523 * WARNING. We are about to set the in-service entity 1524 * to sd->next_in_service, i.e., to the (cached) value 1525 * returned by bfq_lookup_next_entity(sd) the last 1526 * time it was invoked, i.e., the last time when the 1527 * service order in sd changed as a consequence of the 1528 * activation or deactivation of an entity. In this 1529 * respect, if we execute bfq_lookup_next_entity(sd) 1530 * in this very moment, it may, although with low 1531 * probability, yield a different entity than that 1532 * pointed to by sd->next_in_service. This rare event 1533 * happens in case there was no CLASS_IDLE entity to 1534 * serve for sd when bfq_lookup_next_entity(sd) was 1535 * invoked for the last time, while there is now one 1536 * such entity. 1537 * 1538 * If the above event happens, then the scheduling of 1539 * such entity in CLASS_IDLE is postponed until the 1540 * service of the sd->next_in_service entity 1541 * finishes. In fact, when the latter is expired, 1542 * bfq_lookup_next_entity(sd) gets called again, 1543 * exactly to update sd->next_in_service. 1544 */ 1545 1546 /* Make next_in_service entity become in_service_entity */ 1547 entity = sd->next_in_service; 1548 sd->in_service_entity = entity; 1549 1550 /* 1551 * If entity is no longer a candidate for next 1552 * service, then it must be extracted from its active 1553 * tree, so as to make sure that it won't be 1554 * considered when computing next_in_service. See the 1555 * comments on the function 1556 * bfq_no_longer_next_in_service() for details. 1557 */ 1558 if (bfq_no_longer_next_in_service(entity)) 1559 bfq_active_extract(bfq_entity_service_tree(entity), 1560 entity); 1561 1562 /* 1563 * Even if entity is not to be extracted according to 1564 * the above check, a descendant entity may get 1565 * extracted in one of the next iterations of this 1566 * loop. Such an event could cause a change in 1567 * next_in_service for the level of the descendant 1568 * entity, and thus possibly back to this level. 1569 * 1570 * However, we cannot perform the resulting needed 1571 * update of next_in_service for this level before the 1572 * end of the whole loop, because, to know which is 1573 * the correct next-to-serve candidate entity for each 1574 * level, we need first to find the leaf entity to set 1575 * in service. In fact, only after we know which is 1576 * the next-to-serve leaf entity, we can discover 1577 * whether the parent entity of the leaf entity 1578 * becomes the next-to-serve, and so on. 1579 */ 1580 } 1581 1582 bfqq = bfq_entity_to_bfqq(entity); 1583 1584 /* 1585 * We can finally update all next-to-serve entities along the 1586 * path from the leaf entity just set in service to the root. 1587 */ 1588 for_each_entity(entity) { 1589 struct bfq_sched_data *sd = entity->sched_data; 1590 1591 if (!bfq_update_next_in_service(sd, NULL, false)) 1592 break; 1593 } 1594 1595 return bfqq; 1596} 1597 1598/* returns true if the in-service queue gets freed */ 1599bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) 1600{ 1601 struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; 1602 struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; 1603 struct bfq_entity *entity = in_serv_entity; 1604 1605 bfq_clear_bfqq_wait_request(in_serv_bfqq); 1606 hrtimer_try_to_cancel(&bfqd->idle_slice_timer); 1607 bfqd->in_service_queue = NULL; 1608 1609 /* 1610 * When this function is called, all in-service entities have 1611 * been properly deactivated or requeued, so we can safely 1612 * execute the final step: reset in_service_entity along the 1613 * path from entity to the root. 1614 */ 1615 for_each_entity(entity) 1616 entity->sched_data->in_service_entity = NULL; 1617 1618 /* 1619 * in_serv_entity is no longer in service, so, if it is in no 1620 * service tree either, then release the service reference to 1621 * the queue it represents (taken with bfq_get_entity). 1622 */ 1623 if (!in_serv_entity->on_st_or_in_serv) { 1624 /* 1625 * If no process is referencing in_serv_bfqq any 1626 * longer, then the service reference may be the only 1627 * reference to the queue. If this is the case, then 1628 * bfqq gets freed here. 1629 */ 1630 int ref = in_serv_bfqq->ref; 1631 bfq_put_queue(in_serv_bfqq); 1632 if (ref == 1) 1633 return true; 1634 } 1635 1636 return false; 1637} 1638 1639void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, 1640 bool ins_into_idle_tree, bool expiration) 1641{ 1642 struct bfq_entity *entity = &bfqq->entity; 1643 1644 bfq_deactivate_entity(entity, ins_into_idle_tree, expiration); 1645} 1646 1647void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) 1648{ 1649 struct bfq_entity *entity = &bfqq->entity; 1650 1651 bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq), 1652 false, false); 1653 bfq_clear_bfqq_non_blocking_wait_rq(bfqq); 1654} 1655 1656void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, 1657 bool expiration) 1658{ 1659 struct bfq_entity *entity = &bfqq->entity; 1660 1661 bfq_activate_requeue_entity(entity, false, 1662 bfqq == bfqd->in_service_queue, expiration); 1663} 1664 1665/* 1666 * Called when the bfqq no longer has requests pending, remove it from 1667 * the service tree. As a special case, it can be invoked during an 1668 * expiration. 1669 */ 1670void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, 1671 bool expiration) 1672{ 1673 bfq_log_bfqq(bfqd, bfqq, "del from busy"); 1674 1675 bfq_clear_bfqq_busy(bfqq); 1676 1677 bfqd->busy_queues[bfqq->ioprio_class - 1]--; 1678 1679 if (bfqq->wr_coeff > 1) 1680 bfqd->wr_busy_queues--; 1681 1682 bfqg_stats_update_dequeue(bfqq_group(bfqq)); 1683 1684 bfq_deactivate_bfqq(bfqd, bfqq, true, expiration); 1685 1686 if (!bfqq->dispatched) 1687 bfq_weights_tree_remove(bfqd, bfqq); 1688} 1689 1690/* 1691 * Called when an inactive queue receives a new request. 1692 */ 1693void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) 1694{ 1695 bfq_log_bfqq(bfqd, bfqq, "add to busy"); 1696 1697 bfq_activate_bfqq(bfqd, bfqq); 1698 1699 bfq_mark_bfqq_busy(bfqq); 1700 bfqd->busy_queues[bfqq->ioprio_class - 1]++; 1701 1702 if (!bfqq->dispatched) 1703 if (bfqq->wr_coeff == 1) 1704 bfq_weights_tree_add(bfqd, bfqq, 1705 &bfqd->queue_weights_tree); 1706 1707 if (bfqq->wr_coeff > 1) 1708 bfqd->wr_busy_queues++; 1709 1710 /* Move bfqq to the head of the woken list of its waker */ 1711 if (!hlist_unhashed(&bfqq->woken_list_node) && 1712 &bfqq->woken_list_node != bfqq->waker_bfqq->woken_list.first) { 1713 hlist_del_init(&bfqq->woken_list_node); 1714 hlist_add_head(&bfqq->woken_list_node, 1715 &bfqq->waker_bfqq->woken_list); 1716 } 1717} 1718