1 // SPDX-License-Identifier: GPL-2.0-or-later
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).
9 #include "bfq-iosched.h"
12 * bfq_gt - compare two timestamps.
16 * Return @a > @b, dealing with wrapping correctly.
18 static int bfq_gt(u64 a
, u64 b
)
20 return (s64
)(a
- b
) > 0;
23 static struct bfq_entity
*bfq_root_active_entity(struct rb_root
*tree
)
25 struct rb_node
*node
= tree
->rb_node
;
27 return rb_entry(node
, struct bfq_entity
, rb_node
);
30 static unsigned int bfq_class_idx(struct bfq_entity
*entity
)
32 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
34 return bfqq
? bfqq
->ioprio_class
- 1 :
35 BFQ_DEFAULT_GRP_CLASS
- 1;
38 unsigned int bfq_tot_busy_queues(struct bfq_data
*bfqd
)
40 return bfqd
->busy_queues
[0] + bfqd
->busy_queues
[1] +
44 static struct bfq_entity
*bfq_lookup_next_entity(struct bfq_sched_data
*sd
,
47 static bool bfq_update_parent_budget(struct bfq_entity
*next_in_service
);
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
55 * @expiration: id true, this function is being invoked after the
56 * expiration of the in-service entity
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.
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
74 static bool bfq_update_next_in_service(struct bfq_sched_data
*sd
,
75 struct bfq_entity
*new_entity
,
78 struct bfq_entity
*next_in_service
= sd
->next_in_service
;
79 bool parent_sched_may_change
= false;
80 bool change_without_lookup
= false;
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.
93 if (new_entity
&& new_entity
!= sd
->next_in_service
) {
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.
100 change_without_lookup
= true;
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.
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
;
113 change_without_lookup
=
114 (new_entity_class_idx
==
115 bfq_class_idx(next_in_service
)
117 !bfq_gt(new_entity
->start
, st
->vtime
)
119 bfq_gt(next_in_service
->finish
,
120 new_entity
->finish
));
123 if (change_without_lookup
)
124 next_in_service
= new_entity
;
127 if (!change_without_lookup
) /* lookup needed */
128 next_in_service
= bfq_lookup_next_entity(sd
, expiration
);
130 if (next_in_service
) {
131 bool new_budget_triggers_change
=
132 bfq_update_parent_budget(next_in_service
);
134 parent_sched_may_change
= !sd
->next_in_service
||
135 new_budget_triggers_change
;
138 sd
->next_in_service
= next_in_service
;
140 return parent_sched_may_change
;
143 #ifdef CONFIG_BFQ_GROUP_IOSCHED
145 struct bfq_group
*bfq_bfqq_to_bfqg(struct bfq_queue
*bfqq
)
147 struct bfq_entity
*group_entity
= bfqq
->entity
.parent
;
150 group_entity
= &bfqq
->bfqd
->root_group
->entity
;
152 return container_of(group_entity
, struct bfq_group
, entity
);
156 * Returns true if this budget changes may let next_in_service->parent
157 * become the next_in_service entity for its parent entity.
159 static bool bfq_update_parent_budget(struct bfq_entity
*next_in_service
)
161 struct bfq_entity
*bfqg_entity
;
162 struct bfq_group
*bfqg
;
163 struct bfq_sched_data
*group_sd
;
166 group_sd
= next_in_service
->sched_data
;
168 bfqg
= container_of(group_sd
, struct bfq_group
, sched_data
);
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.
174 bfqg_entity
= bfqg
->my_entity
;
176 if (bfqg_entity
->budget
> next_in_service
->budget
)
178 bfqg_entity
->budget
= next_in_service
->budget
;
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.
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.
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.
204 static bool bfq_no_longer_next_in_service(struct bfq_entity
*entity
)
206 struct bfq_group
*bfqg
;
208 if (bfq_entity_to_bfqq(entity
))
211 bfqg
= container_of(entity
, struct bfq_group
, entity
);
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.
225 if (bfqg
->active_entities
== 1)
231 #else /* CONFIG_BFQ_GROUP_IOSCHED */
233 struct bfq_group
*bfq_bfqq_to_bfqg(struct bfq_queue
*bfqq
)
235 return bfqq
->bfqd
->root_group
;
238 static bool bfq_update_parent_budget(struct bfq_entity
*next_in_service
)
243 static bool bfq_no_longer_next_in_service(struct bfq_entity
*entity
)
248 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
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
257 #define WFQ_SERVICE_SHIFT 22
259 struct bfq_queue
*bfq_entity_to_bfqq(struct bfq_entity
*entity
)
261 struct bfq_queue
*bfqq
= NULL
;
263 if (!entity
->my_sched_data
)
264 bfqq
= container_of(entity
, struct bfq_queue
, entity
);
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).
275 static u64
bfq_delta(unsigned long service
, unsigned long weight
)
277 return div64_ul((u64
)service
<< WFQ_SERVICE_SHIFT
, weight
);
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.
285 static void bfq_calc_finish(struct bfq_entity
*entity
, unsigned long service
)
287 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
289 entity
->finish
= entity
->start
+
290 bfq_delta(service
, entity
->weight
);
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
));
304 * bfq_entity_of - get an entity from a node.
305 * @node: the node field of the entity.
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.
312 struct bfq_entity
*bfq_entity_of(struct rb_node
*node
)
314 struct bfq_entity
*entity
= NULL
;
317 entity
= rb_entry(node
, struct bfq_entity
, rb_node
);
323 * bfq_extract - remove an entity from a tree.
324 * @root: the tree root.
325 * @entity: the entity to remove.
327 static void bfq_extract(struct rb_root
*root
, struct bfq_entity
*entity
)
330 rb_erase(&entity
->rb_node
, root
);
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.
338 static void bfq_idle_extract(struct bfq_service_tree
*st
,
339 struct bfq_entity
*entity
)
341 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
342 struct rb_node
*next
;
344 if (entity
== st
->first_idle
) {
345 next
= rb_next(&entity
->rb_node
);
346 st
->first_idle
= bfq_entity_of(next
);
349 if (entity
== st
->last_idle
) {
350 next
= rb_prev(&entity
->rb_node
);
351 st
->last_idle
= bfq_entity_of(next
);
354 bfq_extract(&st
->idle
, entity
);
357 list_del(&bfqq
->bfqq_list
);
361 * bfq_insert - generic tree insertion.
363 * @entity: entity to insert.
365 * This is used for the idle and the active tree, since they are both
366 * ordered by finish time.
368 static void bfq_insert(struct rb_root
*root
, struct bfq_entity
*entity
)
370 struct bfq_entity
*entry
;
371 struct rb_node
**node
= &root
->rb_node
;
372 struct rb_node
*parent
= NULL
;
376 entry
= rb_entry(parent
, struct bfq_entity
, rb_node
);
378 if (bfq_gt(entry
->finish
, entity
->finish
))
379 node
= &parent
->rb_left
;
381 node
= &parent
->rb_right
;
384 rb_link_node(&entity
->rb_node
, parent
, node
);
385 rb_insert_color(&entity
->rb_node
, root
);
391 * bfq_update_min - update the min_start field of a entity.
392 * @entity: the entity to update.
393 * @node: one of its children.
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.
400 static void bfq_update_min(struct bfq_entity
*entity
, struct rb_node
*node
)
402 struct bfq_entity
*child
;
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
;
412 * bfq_update_active_node - recalculate min_start.
413 * @node: the node to update.
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.
419 static void bfq_update_active_node(struct rb_node
*node
)
421 struct bfq_entity
*entity
= rb_entry(node
, struct bfq_entity
, rb_node
);
423 entity
->min_start
= entity
->start
;
424 bfq_update_min(entity
, node
->rb_right
);
425 bfq_update_min(entity
, node
->rb_left
);
429 * bfq_update_active_tree - update min_start for the whole active tree.
430 * @node: the starting node.
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.
438 static void bfq_update_active_tree(struct rb_node
*node
)
440 struct rb_node
*parent
;
443 bfq_update_active_node(node
);
445 parent
= rb_parent(node
);
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
);
459 * bfq_active_insert - insert an entity in the active tree of its
461 * @st: the service tree of the entity.
462 * @entity: the entity being inserted.
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.
469 static void bfq_active_insert(struct bfq_service_tree
*st
,
470 struct bfq_entity
*entity
)
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
;
480 bfq_insert(&st
->active
, entity
);
483 node
= node
->rb_left
;
484 else if (node
->rb_right
)
485 node
= node
->rb_right
;
487 bfq_update_active_tree(node
);
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
;
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
++;
503 * bfq_ioprio_to_weight - calc a weight from an ioprio.
504 * @ioprio: the ioprio value to convert.
506 unsigned short bfq_ioprio_to_weight(int ioprio
)
508 return (IOPRIO_NR_LEVELS
- ioprio
) * BFQ_WEIGHT_CONVERSION_COEFF
;
512 * bfq_weight_to_ioprio - calc an ioprio from a weight.
513 * @weight: the weight value to convert.
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_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
519 static unsigned short bfq_weight_to_ioprio(int weight
)
522 IOPRIO_NR_LEVELS
- weight
/ BFQ_WEIGHT_CONVERSION_COEFF
);
525 static void bfq_get_entity(struct bfq_entity
*entity
)
527 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
531 bfq_log_bfqq(bfqq
->bfqd
, bfqq
, "get_entity: %p %d",
537 * bfq_find_deepest - find the deepest node that an extraction can modify.
538 * @node: the node being removed.
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.
545 static struct rb_node
*bfq_find_deepest(struct rb_node
*node
)
547 struct rb_node
*deepest
;
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
;
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
);
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.
571 static void bfq_active_extract(struct bfq_service_tree
*st
,
572 struct bfq_entity
*entity
)
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
;
582 node
= bfq_find_deepest(&entity
->rb_node
);
583 bfq_extract(&st
->active
, entity
);
586 bfq_update_active_tree(node
);
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
;
594 list_del(&bfqq
->bfqq_list
);
595 #ifdef CONFIG_BFQ_GROUP_IOSCHED
596 if (bfqg
!= bfqd
->root_group
)
597 bfqg
->active_entities
--;
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.
606 static void bfq_idle_insert(struct bfq_service_tree
*st
,
607 struct bfq_entity
*entity
)
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
;
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
;
618 bfq_insert(&st
->idle
, entity
);
621 list_add(&bfqq
->bfqq_list
, &bfqq
->bfqd
->idle_list
);
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.
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.
639 static void bfq_forget_entity(struct bfq_service_tree
*st
,
640 struct bfq_entity
*entity
,
643 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
645 entity
->on_st_or_in_serv
= false;
646 st
->wsum
-= entity
->weight
;
647 if (bfqq
&& !is_in_service
)
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.
656 void bfq_put_idle_entity(struct bfq_service_tree
*st
, struct bfq_entity
*entity
)
658 bfq_idle_extract(st
, entity
);
659 bfq_forget_entity(st
, entity
,
660 entity
== entity
->sched_data
->in_service_entity
);
664 * bfq_forget_idle - update the idle tree if necessary.
665 * @st: the service tree to act upon.
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.
670 static void bfq_forget_idle(struct bfq_service_tree
*st
)
672 struct bfq_entity
*first_idle
= st
->first_idle
;
673 struct bfq_entity
*last_idle
= st
->last_idle
;
675 if (RB_EMPTY_ROOT(&st
->active
) && last_idle
&&
676 !bfq_gt(last_idle
->finish
, st
->vtime
)) {
678 * Forget the whole idle tree, increasing the vtime past
679 * the last finish time of idle entities.
681 st
->vtime
= last_idle
->finish
;
684 if (first_idle
&& !bfq_gt(first_idle
->finish
, st
->vtime
))
685 bfq_put_idle_entity(st
, first_idle
);
688 struct bfq_service_tree
*bfq_entity_service_tree(struct bfq_entity
*entity
)
690 struct bfq_sched_data
*sched_data
= entity
->sched_data
;
691 unsigned int idx
= bfq_class_idx(entity
);
693 return sched_data
->service_tree
+ idx
;
697 * Update weight and priority of entity. If update_class_too is true,
698 * then update the ioprio_class of entity too.
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.
714 struct 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
)
719 struct bfq_service_tree
*new_st
= old_st
;
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
;
733 #ifdef CONFIG_BFQ_GROUP_IOSCHED
735 sd
= entity
->my_sched_data
;
736 bfqg
= container_of(sd
, struct bfq_group
, sched_data
);
737 bfqd
= (struct bfq_data
*)bfqg
->bfqd
;
741 /* Matches the smp_wmb() in bfq_group_set_weight. */
743 old_st
->wsum
-= entity
->weight
;
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",
750 if (entity
->new_weight
< BFQ_MIN_WEIGHT
)
751 entity
->new_weight
= BFQ_MIN_WEIGHT
;
753 entity
->new_weight
= BFQ_MAX_WEIGHT
;
755 entity
->orig_weight
= entity
->new_weight
;
758 bfq_weight_to_ioprio(entity
->orig_weight
);
761 if (bfqq
&& update_class_too
)
762 bfqq
->ioprio_class
= bfqq
->new_ioprio_class
;
765 * Reset prio_changed only if the ioprio_class change
766 * is not pending any longer.
768 if (!bfqq
|| bfqq
->ioprio_class
== bfqq
->new_ioprio_class
)
769 entity
->prio_changed
= 0;
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).
778 new_st
= bfq_entity_service_tree(entity
);
780 prev_weight
= entity
->weight
;
781 new_weight
= entity
->orig_weight
*
782 (bfqq
? bfqq
->wr_coeff
: 1);
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).
788 if (prev_weight
!= new_weight
&& bfqq
) {
789 root
= &bfqd
->queue_weights_tree
;
790 __bfq_weights_tree_remove(bfqd
, bfqq
, root
);
792 entity
->weight
= new_weight
;
794 * Add the entity, if it is not a weight-raised queue,
795 * to the counter associated with its new weight.
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
);
802 new_st
->wsum
+= entity
->weight
;
804 if (new_st
!= old_st
)
805 entity
->start
= new_st
->vtime
;
812 * bfq_bfqq_served - update the scheduler status after selection for
814 * @bfqq: the queue being served.
815 * @served: bytes to transfer.
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.
821 void bfq_bfqq_served(struct bfq_queue
*bfqq
, int served
)
823 struct bfq_entity
*entity
= &bfqq
->entity
;
824 struct bfq_service_tree
*st
;
826 if (!bfqq
->service_from_backlogged
)
827 bfqq
->first_IO_time
= jiffies
;
829 if (bfqq
->wr_coeff
> 1)
830 bfqq
->service_from_wr
+= served
;
832 bfqq
->service_from_backlogged
+= served
;
833 for_each_entity(entity
) {
834 st
= bfq_entity_service_tree(entity
);
836 entity
->service
+= served
;
838 st
->vtime
+= bfq_delta(served
, st
->wsum
);
841 bfq_log_bfqq(bfqq
->bfqd
, bfqq
, "bfqq_served %d secs", served
);
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
849 * @bfqq: the queue that needs a service update.
850 * @time_ms: the amount of time during which the queue has received service
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.
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.
871 void bfq_bfqq_charge_time(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
872 unsigned long time_ms
)
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
);
881 /* Increase budget to avoid inconsistencies */
882 if (tot_serv_to_charge
> entity
->budget
)
883 entity
->budget
= tot_serv_to_charge
;
885 bfq_bfqq_served(bfqq
,
886 max_t(int, 0, tot_serv_to_charge
- entity
->service
));
889 static void bfq_update_fin_time_enqueue(struct bfq_entity
*entity
,
890 struct bfq_service_tree
*st
,
893 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
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).
900 st
= __bfq_entity_update_weight_prio(st
, entity
, true);
901 bfq_calc_finish(entity
, entity
->budget
);
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.
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.
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.
936 if (backshifted
&& bfq_gt(st
->vtime
, entity
->finish
)) {
937 unsigned long delta
= st
->vtime
- entity
->finish
;
940 delta
/= bfqq
->wr_coeff
;
942 entity
->start
+= delta
;
943 entity
->finish
+= delta
;
946 bfq_active_insert(st
, entity
);
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
954 * Called for a 'true' activation, i.e., if entity is not active and
955 * one of its children receives a new request.
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.
961 static void __bfq_activate_entity(struct bfq_entity
*entity
,
962 bool non_blocking_wait_rq
)
964 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
965 bool backshifted
= false;
966 unsigned long long min_vstart
;
968 /* See comments on bfq_fqq_update_budg_for_activation */
969 if (non_blocking_wait_rq
&& bfq_gt(st
->vtime
, entity
->finish
)) {
971 min_vstart
= entity
->finish
;
973 min_vstart
= st
->vtime
;
975 if (entity
->tree
== &st
->idle
) {
977 * Must be on the idle tree, bfq_idle_extract() will
980 bfq_idle_extract(st
, entity
);
981 entity
->start
= bfq_gt(min_vstart
, entity
->finish
) ?
982 min_vstart
: entity
->finish
;
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.
989 entity
->start
= min_vstart
;
990 st
->wsum
+= entity
->weight
;
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.
997 bfq_get_entity(entity
);
999 entity
->on_st_or_in_serv
= true;
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
;
1008 if (!entity
->in_groups_with_pending_reqs
) {
1009 entity
->in_groups_with_pending_reqs
= true;
1010 bfqd
->num_groups_with_pending_reqs
++;
1015 bfq_update_fin_time_enqueue(entity
, st
, backshifted
);
1019 * __bfq_requeue_entity - handle requeueing or repositioning of an entity.
1020 * @entity: the entity being requeued or repositioned.
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
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).
1033 static void __bfq_requeue_entity(struct bfq_entity
*entity
)
1035 struct bfq_sched_data
*sd
= entity
->sched_data
;
1036 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
1038 if (entity
== sd
->in_service_entity
) {
1040 * We are requeueing the current in-service entity,
1041 * which may have to be done for one of the following
1043 * - entity represents the in-service queue, and the
1044 * in-service queue is being requeued after an
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.
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
1061 bfq_calc_finish(entity
, entity
->service
);
1062 entity
->start
= entity
->finish
;
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.
1077 bfq_active_extract(st
, entity
);
1078 } else { /* The entity is already active, and not in service */
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.
1093 bfq_active_extract(st
, entity
);
1096 bfq_update_fin_time_enqueue(entity
, st
, false);
1099 static void __bfq_activate_requeue_entity(struct bfq_entity
*entity
,
1100 struct bfq_sched_data
*sd
,
1101 bool non_blocking_wait_rq
)
1103 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
1105 if (sd
->in_service_entity
== entity
|| entity
->tree
== &st
->active
)
1107 * in service or already queued on the active tree,
1108 * requeue or reposition
1110 __bfq_requeue_entity(entity
);
1113 * Not in service and not queued on its active tree:
1114 * the activity is idle and this is a true activation.
1116 __bfq_activate_entity(entity
, non_blocking_wait_rq
);
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
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
1133 static void bfq_activate_requeue_entity(struct bfq_entity
*entity
,
1134 bool non_blocking_wait_rq
,
1135 bool requeue
, bool expiration
)
1137 struct bfq_sched_data
*sd
;
1139 for_each_entity(entity
) {
1140 sd
= entity
->sched_data
;
1141 __bfq_activate_requeue_entity(entity
, sd
, non_blocking_wait_rq
);
1143 if (!bfq_update_next_in_service(sd
, entity
, expiration
) &&
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
1156 * If necessary and allowed, puts entity into the idle tree. NOTE:
1157 * entity may be on no tree if in service.
1159 bool __bfq_deactivate_entity(struct bfq_entity
*entity
, bool ins_into_idle_tree
)
1161 struct bfq_sched_data
*sd
= entity
->sched_data
;
1162 struct bfq_service_tree
*st
;
1165 if (!entity
->on_st_or_in_serv
) /*
1166 * entity never activated, or
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.
1177 st
= bfq_entity_service_tree(entity
);
1178 is_in_service
= entity
== sd
->in_service_entity
;
1180 bfq_calc_finish(entity
, entity
->service
);
1183 sd
->in_service_entity
= NULL
;
1186 * Non in-service entity: nobody will take care of
1187 * resetting its service counter on expiration. Do it
1190 entity
->service
= 0;
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
);
1197 if (!ins_into_idle_tree
|| !bfq_gt(entity
->finish
, st
->vtime
))
1198 bfq_forget_entity(st
, entity
, is_in_service
);
1200 bfq_idle_insert(st
, entity
);
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
1212 static void bfq_deactivate_entity(struct bfq_entity
*entity
,
1213 bool ins_into_idle_tree
,
1216 struct bfq_sched_data
*sd
;
1217 struct bfq_entity
*parent
= NULL
;
1219 for_each_entity_safe(entity
, parent
) {
1220 sd
= entity
->sched_data
;
1222 if (!__bfq_deactivate_entity(entity
, ins_into_idle_tree
)) {
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
1233 if (sd
->next_in_service
== entity
)
1235 * entity was the next_in_service entity,
1236 * then, since entity has just been
1237 * deactivated, a new one must be found.
1239 bfq_update_next_in_service(sd
, NULL
, expiration
);
1241 if (sd
->next_in_service
|| sd
->in_service_entity
) {
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.
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.
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.
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.
1277 ins_into_idle_tree
= true;
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
1288 for_each_entity(entity
) {
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
1295 __bfq_requeue_entity(entity
);
1297 sd
= entity
->sched_data
;
1298 if (!bfq_update_next_in_service(sd
, entity
, expiration
) &&
1301 * next_in_service unchanged or not causing
1302 * any change in entity->parent->sd, and no
1303 * requeueing needed for expiration: stop
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.
1315 * Assumes that st is not empty.
1317 static u64
bfq_calc_vtime_jump(struct bfq_service_tree
*st
)
1319 struct bfq_entity
*root_entity
= bfq_root_active_entity(&st
->active
);
1321 if (bfq_gt(root_entity
->min_start
, st
->vtime
))
1322 return root_entity
->min_start
;
1327 static void bfq_update_vtime(struct bfq_service_tree
*st
, u64 new_value
)
1329 if (new_value
> st
->vtime
) {
1330 st
->vtime
= new_value
;
1331 bfq_forget_idle(st
);
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
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.
1347 static struct bfq_entity
*bfq_first_active_entity(struct bfq_service_tree
*st
,
1350 struct bfq_entity
*entry
, *first
= NULL
;
1351 struct rb_node
*node
= st
->active
.rb_node
;
1354 entry
= rb_entry(node
, struct bfq_entity
, rb_node
);
1356 if (!bfq_gt(entry
->start
, vtime
))
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
;
1369 node
= node
->rb_right
;
1376 * __bfq_lookup_next_entity - return the first eligible entity in @st.
1377 * @st: the service tree.
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, ...).
1386 * In this first case, update the virtual time in @st too (see the
1387 * comments on this update inside the function).
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
1397 static struct bfq_entity
*
1398 __bfq_lookup_next_entity(struct bfq_service_tree
*st
, bool in_service
)
1400 struct bfq_entity
*entity
;
1403 if (RB_EMPTY_ROOT(&st
->active
))
1407 * Get the value of the system virtual time for which at
1408 * least one entity is eligible.
1410 new_vtime
= bfq_calc_vtime_jump(st
);
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
1423 bfq_update_vtime(st
, new_vtime
);
1425 entity
= bfq_first_active_entity(st
, new_vtime
);
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
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.
1439 static struct bfq_entity
*bfq_lookup_next_entity(struct bfq_sched_data
*sd
,
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
;
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.
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
;
1463 * Find the next entity to serve for the highest-priority
1464 * class, unless the idle class needs to be served.
1466 for (; class_idx
< BFQ_IOPRIO_CLASSES
; class_idx
++) {
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.
1482 entity
= __bfq_lookup_next_entity(st
+ class_idx
,
1483 sd
->in_service_entity
&&
1496 bool next_queue_may_preempt(struct bfq_data
*bfqd
)
1498 struct bfq_sched_data
*sd
= &bfqd
->root_group
->sched_data
;
1500 return sd
->next_in_service
!= sd
->in_service_entity
;
1504 * Get next queue for service.
1506 struct bfq_queue
*bfq_get_next_queue(struct bfq_data
*bfqd
)
1508 struct bfq_entity
*entity
= NULL
;
1509 struct bfq_sched_data
*sd
;
1510 struct bfq_queue
*bfqq
;
1512 if (bfq_tot_busy_queues(bfqd
) == 0)
1516 * Traverse the path from the root to the leaf entity to
1517 * serve. Set in service all the entities visited along the
1520 sd
= &bfqd
->root_group
->sched_data
;
1521 for (; sd
; sd
= entity
->my_sched_data
) {
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
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.
1546 /* Make next_in_service entity become in_service_entity */
1547 entity
= sd
->next_in_service
;
1548 sd
->in_service_entity
= entity
;
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.
1558 if (bfq_no_longer_next_in_service(entity
))
1559 bfq_active_extract(bfq_entity_service_tree(entity
),
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.
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.
1582 bfqq
= bfq_entity_to_bfqq(entity
);
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.
1588 for_each_entity(entity
) {
1589 struct bfq_sched_data
*sd
= entity
->sched_data
;
1591 if (!bfq_update_next_in_service(sd
, NULL
, false))
1598 /* returns true if the in-service queue gets freed */
1599 bool __bfq_bfqd_reset_in_service(struct bfq_data
*bfqd
)
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
;
1605 bfq_clear_bfqq_wait_request(in_serv_bfqq
);
1606 hrtimer_try_to_cancel(&bfqd
->idle_slice_timer
);
1607 bfqd
->in_service_queue
= NULL
;
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.
1615 for_each_entity(entity
)
1616 entity
->sched_data
->in_service_entity
= NULL
;
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).
1623 if (!in_serv_entity
->on_st_or_in_serv
) {
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.
1630 int ref
= in_serv_bfqq
->ref
;
1631 bfq_put_queue(in_serv_bfqq
);
1639 void bfq_deactivate_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1640 bool ins_into_idle_tree
, bool expiration
)
1642 struct bfq_entity
*entity
= &bfqq
->entity
;
1644 bfq_deactivate_entity(entity
, ins_into_idle_tree
, expiration
);
1647 void bfq_activate_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
)
1649 struct bfq_entity
*entity
= &bfqq
->entity
;
1651 bfq_activate_requeue_entity(entity
, bfq_bfqq_non_blocking_wait_rq(bfqq
),
1653 bfq_clear_bfqq_non_blocking_wait_rq(bfqq
);
1656 void bfq_requeue_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1659 struct bfq_entity
*entity
= &bfqq
->entity
;
1661 bfq_activate_requeue_entity(entity
, false,
1662 bfqq
== bfqd
->in_service_queue
, expiration
);
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
1670 void bfq_del_bfqq_busy(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1673 bfq_log_bfqq(bfqd
, bfqq
, "del from busy");
1675 bfq_clear_bfqq_busy(bfqq
);
1677 bfqd
->busy_queues
[bfqq
->ioprio_class
- 1]--;
1679 if (bfqq
->wr_coeff
> 1)
1680 bfqd
->wr_busy_queues
--;
1682 bfqg_stats_update_dequeue(bfqq_group(bfqq
));
1684 bfq_deactivate_bfqq(bfqd
, bfqq
, true, expiration
);
1686 if (!bfqq
->dispatched
)
1687 bfq_weights_tree_remove(bfqd
, bfqq
);
1691 * Called when an inactive queue receives a new request.
1693 void bfq_add_bfqq_busy(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
)
1695 bfq_log_bfqq(bfqd
, bfqq
, "add to busy");
1697 bfq_activate_bfqq(bfqd
, bfqq
);
1699 bfq_mark_bfqq_busy(bfqq
);
1700 bfqd
->busy_queues
[bfqq
->ioprio_class
- 1]++;
1702 if (!bfqq
->dispatched
)
1703 if (bfqq
->wr_coeff
== 1)
1704 bfq_weights_tree_add(bfqd
, bfqq
,
1705 &bfqd
->queue_weights_tree
);
1707 if (bfqq
->wr_coeff
> 1)
1708 bfqd
->wr_busy_queues
++;
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
);