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
146 * Returns true if this budget changes may let next_in_service->parent
147 * become the next_in_service entity for its parent entity.
149 static bool bfq_update_parent_budget(struct bfq_entity
*next_in_service
)
151 struct bfq_entity
*bfqg_entity
;
152 struct bfq_group
*bfqg
;
153 struct bfq_sched_data
*group_sd
;
156 group_sd
= next_in_service
->sched_data
;
158 bfqg
= container_of(group_sd
, struct bfq_group
, sched_data
);
160 * bfq_group's my_entity field is not NULL only if the group
161 * is not the root group. We must not touch the root entity
162 * as it must never become an in-service entity.
164 bfqg_entity
= bfqg
->my_entity
;
166 if (bfqg_entity
->budget
> next_in_service
->budget
)
168 bfqg_entity
->budget
= next_in_service
->budget
;
175 * This function tells whether entity stops being a candidate for next
176 * service, according to the restrictive definition of the field
177 * next_in_service. In particular, this function is invoked for an
178 * entity that is about to be set in service.
180 * If entity is a queue, then the entity is no longer a candidate for
181 * next service according to the that definition, because entity is
182 * about to become the in-service queue. This function then returns
183 * true if entity is a queue.
185 * In contrast, entity could still be a candidate for next service if
186 * it is not a queue, and has more than one active child. In fact,
187 * even if one of its children is about to be set in service, other
188 * active children may still be the next to serve, for the parent
189 * entity, even according to the above definition. As a consequence, a
190 * non-queue entity is not a candidate for next-service only if it has
191 * only one active child. And only if this condition holds, then this
192 * function returns true for a non-queue entity.
194 static bool bfq_no_longer_next_in_service(struct bfq_entity
*entity
)
196 struct bfq_group
*bfqg
;
198 if (bfq_entity_to_bfqq(entity
))
201 bfqg
= container_of(entity
, struct bfq_group
, entity
);
204 * The field active_entities does not always contain the
205 * actual number of active children entities: it happens to
206 * not account for the in-service entity in case the latter is
207 * removed from its active tree (which may get done after
208 * invoking the function bfq_no_longer_next_in_service in
209 * bfq_get_next_queue). Fortunately, here, i.e., while
210 * bfq_no_longer_next_in_service is not yet completed in
211 * bfq_get_next_queue, bfq_active_extract has not yet been
212 * invoked, and thus active_entities still coincides with the
213 * actual number of active entities.
215 if (bfqg
->active_entities
== 1)
221 #else /* CONFIG_BFQ_GROUP_IOSCHED */
223 static bool bfq_update_parent_budget(struct bfq_entity
*next_in_service
)
228 static bool bfq_no_longer_next_in_service(struct bfq_entity
*entity
)
233 #endif /* CONFIG_BFQ_GROUP_IOSCHED */
236 * Shift for timestamp calculations. This actually limits the maximum
237 * service allowed in one timestamp delta (small shift values increase it),
238 * the maximum total weight that can be used for the queues in the system
239 * (big shift values increase it), and the period of virtual time
242 #define WFQ_SERVICE_SHIFT 22
244 struct bfq_queue
*bfq_entity_to_bfqq(struct bfq_entity
*entity
)
246 struct bfq_queue
*bfqq
= NULL
;
248 if (!entity
->my_sched_data
)
249 bfqq
= container_of(entity
, struct bfq_queue
, entity
);
256 * bfq_delta - map service into the virtual time domain.
257 * @service: amount of service.
258 * @weight: scale factor (weight of an entity or weight sum).
260 static u64
bfq_delta(unsigned long service
, unsigned long weight
)
262 return div64_ul((u64
)service
<< WFQ_SERVICE_SHIFT
, weight
);
266 * bfq_calc_finish - assign the finish time to an entity.
267 * @entity: the entity to act upon.
268 * @service: the service to be charged to the entity.
270 static void bfq_calc_finish(struct bfq_entity
*entity
, unsigned long service
)
272 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
274 entity
->finish
= entity
->start
+
275 bfq_delta(service
, entity
->weight
);
278 bfq_log_bfqq(bfqq
->bfqd
, bfqq
,
279 "calc_finish: serv %lu, w %d",
280 service
, entity
->weight
);
281 bfq_log_bfqq(bfqq
->bfqd
, bfqq
,
282 "calc_finish: start %llu, finish %llu, delta %llu",
283 entity
->start
, entity
->finish
,
284 bfq_delta(service
, entity
->weight
));
289 * bfq_entity_of - get an entity from a node.
290 * @node: the node field of the entity.
292 * Convert a node pointer to the relative entity. This is used only
293 * to simplify the logic of some functions and not as the generic
294 * conversion mechanism because, e.g., in the tree walking functions,
295 * the check for a %NULL value would be redundant.
297 struct bfq_entity
*bfq_entity_of(struct rb_node
*node
)
299 struct bfq_entity
*entity
= NULL
;
302 entity
= rb_entry(node
, struct bfq_entity
, rb_node
);
308 * bfq_extract - remove an entity from a tree.
309 * @root: the tree root.
310 * @entity: the entity to remove.
312 static void bfq_extract(struct rb_root
*root
, struct bfq_entity
*entity
)
315 rb_erase(&entity
->rb_node
, root
);
319 * bfq_idle_extract - extract an entity from the idle tree.
320 * @st: the service tree of the owning @entity.
321 * @entity: the entity being removed.
323 static void bfq_idle_extract(struct bfq_service_tree
*st
,
324 struct bfq_entity
*entity
)
326 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
327 struct rb_node
*next
;
329 if (entity
== st
->first_idle
) {
330 next
= rb_next(&entity
->rb_node
);
331 st
->first_idle
= bfq_entity_of(next
);
334 if (entity
== st
->last_idle
) {
335 next
= rb_prev(&entity
->rb_node
);
336 st
->last_idle
= bfq_entity_of(next
);
339 bfq_extract(&st
->idle
, entity
);
342 list_del(&bfqq
->bfqq_list
);
346 * bfq_insert - generic tree insertion.
348 * @entity: entity to insert.
350 * This is used for the idle and the active tree, since they are both
351 * ordered by finish time.
353 static void bfq_insert(struct rb_root
*root
, struct bfq_entity
*entity
)
355 struct bfq_entity
*entry
;
356 struct rb_node
**node
= &root
->rb_node
;
357 struct rb_node
*parent
= NULL
;
361 entry
= rb_entry(parent
, struct bfq_entity
, rb_node
);
363 if (bfq_gt(entry
->finish
, entity
->finish
))
364 node
= &parent
->rb_left
;
366 node
= &parent
->rb_right
;
369 rb_link_node(&entity
->rb_node
, parent
, node
);
370 rb_insert_color(&entity
->rb_node
, root
);
376 * bfq_update_min - update the min_start field of a entity.
377 * @entity: the entity to update.
378 * @node: one of its children.
380 * This function is called when @entity may store an invalid value for
381 * min_start due to updates to the active tree. The function assumes
382 * that the subtree rooted at @node (which may be its left or its right
383 * child) has a valid min_start value.
385 static void bfq_update_min(struct bfq_entity
*entity
, struct rb_node
*node
)
387 struct bfq_entity
*child
;
390 child
= rb_entry(node
, struct bfq_entity
, rb_node
);
391 if (bfq_gt(entity
->min_start
, child
->min_start
))
392 entity
->min_start
= child
->min_start
;
397 * bfq_update_active_node - recalculate min_start.
398 * @node: the node to update.
400 * @node may have changed position or one of its children may have moved,
401 * this function updates its min_start value. The left and right subtrees
402 * are assumed to hold a correct min_start value.
404 static void bfq_update_active_node(struct rb_node
*node
)
406 struct bfq_entity
*entity
= rb_entry(node
, struct bfq_entity
, rb_node
);
408 entity
->min_start
= entity
->start
;
409 bfq_update_min(entity
, node
->rb_right
);
410 bfq_update_min(entity
, node
->rb_left
);
414 * bfq_update_active_tree - update min_start for the whole active tree.
415 * @node: the starting node.
417 * @node must be the deepest modified node after an update. This function
418 * updates its min_start using the values held by its children, assuming
419 * that they did not change, and then updates all the nodes that may have
420 * changed in the path to the root. The only nodes that may have changed
421 * are the ones in the path or their siblings.
423 static void bfq_update_active_tree(struct rb_node
*node
)
425 struct rb_node
*parent
;
428 bfq_update_active_node(node
);
430 parent
= rb_parent(node
);
434 if (node
== parent
->rb_left
&& parent
->rb_right
)
435 bfq_update_active_node(parent
->rb_right
);
436 else if (parent
->rb_left
)
437 bfq_update_active_node(parent
->rb_left
);
444 * bfq_active_insert - insert an entity in the active tree of its
446 * @st: the service tree of the entity.
447 * @entity: the entity being inserted.
449 * The active tree is ordered by finish time, but an extra key is kept
450 * per each node, containing the minimum value for the start times of
451 * its children (and the node itself), so it's possible to search for
452 * the eligible node with the lowest finish time in logarithmic time.
454 static void bfq_active_insert(struct bfq_service_tree
*st
,
455 struct bfq_entity
*entity
)
457 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
458 struct rb_node
*node
= &entity
->rb_node
;
459 #ifdef CONFIG_BFQ_GROUP_IOSCHED
460 struct bfq_sched_data
*sd
= NULL
;
461 struct bfq_group
*bfqg
= NULL
;
462 struct bfq_data
*bfqd
= NULL
;
465 bfq_insert(&st
->active
, entity
);
468 node
= node
->rb_left
;
469 else if (node
->rb_right
)
470 node
= node
->rb_right
;
472 bfq_update_active_tree(node
);
474 #ifdef CONFIG_BFQ_GROUP_IOSCHED
475 sd
= entity
->sched_data
;
476 bfqg
= container_of(sd
, struct bfq_group
, sched_data
);
477 bfqd
= (struct bfq_data
*)bfqg
->bfqd
;
480 list_add(&bfqq
->bfqq_list
, &bfqq
->bfqd
->active_list
);
481 #ifdef CONFIG_BFQ_GROUP_IOSCHED
482 if (bfqg
!= bfqd
->root_group
)
483 bfqg
->active_entities
++;
488 * bfq_ioprio_to_weight - calc a weight from an ioprio.
489 * @ioprio: the ioprio value to convert.
491 unsigned short bfq_ioprio_to_weight(int ioprio
)
493 return (IOPRIO_NR_LEVELS
- ioprio
) * BFQ_WEIGHT_CONVERSION_COEFF
;
497 * bfq_weight_to_ioprio - calc an ioprio from a weight.
498 * @weight: the weight value to convert.
500 * To preserve as much as possible the old only-ioprio user interface,
501 * 0 is used as an escape ioprio value for weights (numerically) equal or
502 * larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF.
504 static unsigned short bfq_weight_to_ioprio(int weight
)
507 IOPRIO_NR_LEVELS
- weight
/ BFQ_WEIGHT_CONVERSION_COEFF
);
510 static void bfq_get_entity(struct bfq_entity
*entity
)
512 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
516 bfq_log_bfqq(bfqq
->bfqd
, bfqq
, "get_entity: %p %d",
522 * bfq_find_deepest - find the deepest node that an extraction can modify.
523 * @node: the node being removed.
525 * Do the first step of an extraction in an rb tree, looking for the
526 * node that will replace @node, and returning the deepest node that
527 * the following modifications to the tree can touch. If @node is the
528 * last node in the tree return %NULL.
530 static struct rb_node
*bfq_find_deepest(struct rb_node
*node
)
532 struct rb_node
*deepest
;
534 if (!node
->rb_right
&& !node
->rb_left
)
535 deepest
= rb_parent(node
);
536 else if (!node
->rb_right
)
537 deepest
= node
->rb_left
;
538 else if (!node
->rb_left
)
539 deepest
= node
->rb_right
;
541 deepest
= rb_next(node
);
542 if (deepest
->rb_right
)
543 deepest
= deepest
->rb_right
;
544 else if (rb_parent(deepest
) != node
)
545 deepest
= rb_parent(deepest
);
552 * bfq_active_extract - remove an entity from the active tree.
553 * @st: the service_tree containing the tree.
554 * @entity: the entity being removed.
556 static void bfq_active_extract(struct bfq_service_tree
*st
,
557 struct bfq_entity
*entity
)
559 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
560 struct rb_node
*node
;
561 #ifdef CONFIG_BFQ_GROUP_IOSCHED
562 struct bfq_sched_data
*sd
= NULL
;
563 struct bfq_group
*bfqg
= NULL
;
564 struct bfq_data
*bfqd
= NULL
;
567 node
= bfq_find_deepest(&entity
->rb_node
);
568 bfq_extract(&st
->active
, entity
);
571 bfq_update_active_tree(node
);
573 #ifdef CONFIG_BFQ_GROUP_IOSCHED
574 sd
= entity
->sched_data
;
575 bfqg
= container_of(sd
, struct bfq_group
, sched_data
);
576 bfqd
= (struct bfq_data
*)bfqg
->bfqd
;
579 list_del(&bfqq
->bfqq_list
);
580 #ifdef CONFIG_BFQ_GROUP_IOSCHED
581 if (bfqg
!= bfqd
->root_group
)
582 bfqg
->active_entities
--;
587 * bfq_idle_insert - insert an entity into the idle tree.
588 * @st: the service tree containing the tree.
589 * @entity: the entity to insert.
591 static void bfq_idle_insert(struct bfq_service_tree
*st
,
592 struct bfq_entity
*entity
)
594 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
595 struct bfq_entity
*first_idle
= st
->first_idle
;
596 struct bfq_entity
*last_idle
= st
->last_idle
;
598 if (!first_idle
|| bfq_gt(first_idle
->finish
, entity
->finish
))
599 st
->first_idle
= entity
;
600 if (!last_idle
|| bfq_gt(entity
->finish
, last_idle
->finish
))
601 st
->last_idle
= entity
;
603 bfq_insert(&st
->idle
, entity
);
606 list_add(&bfqq
->bfqq_list
, &bfqq
->bfqd
->idle_list
);
610 * bfq_forget_entity - do not consider entity any longer for scheduling
611 * @st: the service tree.
612 * @entity: the entity being removed.
613 * @is_in_service: true if entity is currently the in-service entity.
615 * Forget everything about @entity. In addition, if entity represents
616 * a queue, and the latter is not in service, then release the service
617 * reference to the queue (the one taken through bfq_get_entity). In
618 * fact, in this case, there is really no more service reference to
619 * the queue, as the latter is also outside any service tree. If,
620 * instead, the queue is in service, then __bfq_bfqd_reset_in_service
621 * will take care of putting the reference when the queue finally
622 * stops being served.
624 static void bfq_forget_entity(struct bfq_service_tree
*st
,
625 struct bfq_entity
*entity
,
628 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
630 entity
->on_st_or_in_serv
= false;
631 st
->wsum
-= entity
->weight
;
632 if (bfqq
&& !is_in_service
)
637 * bfq_put_idle_entity - release the idle tree ref of an entity.
638 * @st: service tree for the entity.
639 * @entity: the entity being released.
641 void bfq_put_idle_entity(struct bfq_service_tree
*st
, struct bfq_entity
*entity
)
643 bfq_idle_extract(st
, entity
);
644 bfq_forget_entity(st
, entity
,
645 entity
== entity
->sched_data
->in_service_entity
);
649 * bfq_forget_idle - update the idle tree if necessary.
650 * @st: the service tree to act upon.
652 * To preserve the global O(log N) complexity we only remove one entry here;
653 * as the idle tree will not grow indefinitely this can be done safely.
655 static void bfq_forget_idle(struct bfq_service_tree
*st
)
657 struct bfq_entity
*first_idle
= st
->first_idle
;
658 struct bfq_entity
*last_idle
= st
->last_idle
;
660 if (RB_EMPTY_ROOT(&st
->active
) && last_idle
&&
661 !bfq_gt(last_idle
->finish
, st
->vtime
)) {
663 * Forget the whole idle tree, increasing the vtime past
664 * the last finish time of idle entities.
666 st
->vtime
= last_idle
->finish
;
669 if (first_idle
&& !bfq_gt(first_idle
->finish
, st
->vtime
))
670 bfq_put_idle_entity(st
, first_idle
);
673 struct bfq_service_tree
*bfq_entity_service_tree(struct bfq_entity
*entity
)
675 struct bfq_sched_data
*sched_data
= entity
->sched_data
;
676 unsigned int idx
= bfq_class_idx(entity
);
678 return sched_data
->service_tree
+ idx
;
682 * Update weight and priority of entity. If update_class_too is true,
683 * then update the ioprio_class of entity too.
685 * The reason why the update of ioprio_class is controlled through the
686 * last parameter is as follows. Changing the ioprio class of an
687 * entity implies changing the destination service trees for that
688 * entity. If such a change occurred when the entity is already on one
689 * of the service trees for its previous class, then the state of the
690 * entity would become more complex: none of the new possible service
691 * trees for the entity, according to bfq_entity_service_tree(), would
692 * match any of the possible service trees on which the entity
693 * is. Complex operations involving these trees, such as entity
694 * activations and deactivations, should take into account this
695 * additional complexity. To avoid this issue, this function is
696 * invoked with update_class_too unset in the points in the code where
697 * entity may happen to be on some tree.
699 struct bfq_service_tree
*
700 __bfq_entity_update_weight_prio(struct bfq_service_tree
*old_st
,
701 struct bfq_entity
*entity
,
702 bool update_class_too
)
704 struct bfq_service_tree
*new_st
= old_st
;
706 if (entity
->prio_changed
) {
707 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
708 unsigned int prev_weight
, new_weight
;
709 struct bfq_data
*bfqd
= NULL
;
710 struct rb_root_cached
*root
;
711 #ifdef CONFIG_BFQ_GROUP_IOSCHED
712 struct bfq_sched_data
*sd
;
713 struct bfq_group
*bfqg
;
718 #ifdef CONFIG_BFQ_GROUP_IOSCHED
720 sd
= entity
->my_sched_data
;
721 bfqg
= container_of(sd
, struct bfq_group
, sched_data
);
722 bfqd
= (struct bfq_data
*)bfqg
->bfqd
;
726 /* Matches the smp_wmb() in bfq_group_set_weight. */
728 old_st
->wsum
-= entity
->weight
;
730 if (entity
->new_weight
!= entity
->orig_weight
) {
731 if (entity
->new_weight
< BFQ_MIN_WEIGHT
||
732 entity
->new_weight
> BFQ_MAX_WEIGHT
) {
733 pr_crit("update_weight_prio: new_weight %d\n",
735 if (entity
->new_weight
< BFQ_MIN_WEIGHT
)
736 entity
->new_weight
= BFQ_MIN_WEIGHT
;
738 entity
->new_weight
= BFQ_MAX_WEIGHT
;
740 entity
->orig_weight
= entity
->new_weight
;
743 bfq_weight_to_ioprio(entity
->orig_weight
);
746 if (bfqq
&& update_class_too
)
747 bfqq
->ioprio_class
= bfqq
->new_ioprio_class
;
750 * Reset prio_changed only if the ioprio_class change
751 * is not pending any longer.
753 if (!bfqq
|| bfqq
->ioprio_class
== bfqq
->new_ioprio_class
)
754 entity
->prio_changed
= 0;
757 * NOTE: here we may be changing the weight too early,
758 * this will cause unfairness. The correct approach
759 * would have required additional complexity to defer
760 * weight changes to the proper time instants (i.e.,
761 * when entity->finish <= old_st->vtime).
763 new_st
= bfq_entity_service_tree(entity
);
765 prev_weight
= entity
->weight
;
766 new_weight
= entity
->orig_weight
*
767 (bfqq
? bfqq
->wr_coeff
: 1);
769 * If the weight of the entity changes, and the entity is a
770 * queue, remove the entity from its old weight counter (if
771 * there is a counter associated with the entity).
773 if (prev_weight
!= new_weight
&& bfqq
) {
774 root
= &bfqd
->queue_weights_tree
;
775 __bfq_weights_tree_remove(bfqd
, bfqq
, root
);
777 entity
->weight
= new_weight
;
779 * Add the entity, if it is not a weight-raised queue,
780 * to the counter associated with its new weight.
782 if (prev_weight
!= new_weight
&& bfqq
&& bfqq
->wr_coeff
== 1) {
783 /* If we get here, root has been initialized. */
784 bfq_weights_tree_add(bfqd
, bfqq
, root
);
787 new_st
->wsum
+= entity
->weight
;
789 if (new_st
!= old_st
)
790 entity
->start
= new_st
->vtime
;
797 * bfq_bfqq_served - update the scheduler status after selection for
799 * @bfqq: the queue being served.
800 * @served: bytes to transfer.
802 * NOTE: this can be optimized, as the timestamps of upper level entities
803 * are synchronized every time a new bfqq is selected for service. By now,
804 * we keep it to better check consistency.
806 void bfq_bfqq_served(struct bfq_queue
*bfqq
, int served
)
808 struct bfq_entity
*entity
= &bfqq
->entity
;
809 struct bfq_service_tree
*st
;
811 if (!bfqq
->service_from_backlogged
)
812 bfqq
->first_IO_time
= jiffies
;
814 if (bfqq
->wr_coeff
> 1)
815 bfqq
->service_from_wr
+= served
;
817 bfqq
->service_from_backlogged
+= served
;
818 for_each_entity(entity
) {
819 st
= bfq_entity_service_tree(entity
);
821 entity
->service
+= served
;
823 st
->vtime
+= bfq_delta(served
, st
->wsum
);
826 bfq_log_bfqq(bfqq
->bfqd
, bfqq
, "bfqq_served %d secs", served
);
830 * bfq_bfqq_charge_time - charge an amount of service equivalent to the length
831 * of the time interval during which bfqq has been in
834 * @bfqq: the queue that needs a service update.
835 * @time_ms: the amount of time during which the queue has received service
837 * If a queue does not consume its budget fast enough, then providing
838 * the queue with service fairness may impair throughput, more or less
839 * severely. For this reason, queues that consume their budget slowly
840 * are provided with time fairness instead of service fairness. This
841 * goal is achieved through the BFQ scheduling engine, even if such an
842 * engine works in the service, and not in the time domain. The trick
843 * is charging these queues with an inflated amount of service, equal
844 * to the amount of service that they would have received during their
845 * service slot if they had been fast, i.e., if their requests had
846 * been dispatched at a rate equal to the estimated peak rate.
848 * It is worth noting that time fairness can cause important
849 * distortions in terms of bandwidth distribution, on devices with
850 * internal queueing. The reason is that I/O requests dispatched
851 * during the service slot of a queue may be served after that service
852 * slot is finished, and may have a total processing time loosely
853 * correlated with the duration of the service slot. This is
854 * especially true for short service slots.
856 void bfq_bfqq_charge_time(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
857 unsigned long time_ms
)
859 struct bfq_entity
*entity
= &bfqq
->entity
;
860 unsigned long timeout_ms
= jiffies_to_msecs(bfq_timeout
);
861 unsigned long bounded_time_ms
= min(time_ms
, timeout_ms
);
862 int serv_to_charge_for_time
=
863 (bfqd
->bfq_max_budget
* bounded_time_ms
) / timeout_ms
;
864 int tot_serv_to_charge
= max(serv_to_charge_for_time
, entity
->service
);
866 /* Increase budget to avoid inconsistencies */
867 if (tot_serv_to_charge
> entity
->budget
)
868 entity
->budget
= tot_serv_to_charge
;
870 bfq_bfqq_served(bfqq
,
871 max_t(int, 0, tot_serv_to_charge
- entity
->service
));
874 static void bfq_update_fin_time_enqueue(struct bfq_entity
*entity
,
875 struct bfq_service_tree
*st
,
878 struct bfq_queue
*bfqq
= bfq_entity_to_bfqq(entity
);
881 * When this function is invoked, entity is not in any service
882 * tree, then it is safe to invoke next function with the last
883 * parameter set (see the comments on the function).
885 st
= __bfq_entity_update_weight_prio(st
, entity
, true);
886 bfq_calc_finish(entity
, entity
->budget
);
889 * If some queues enjoy backshifting for a while, then their
890 * (virtual) finish timestamps may happen to become lower and
891 * lower than the system virtual time. In particular, if
892 * these queues often happen to be idle for short time
893 * periods, and during such time periods other queues with
894 * higher timestamps happen to be busy, then the backshifted
895 * timestamps of the former queues can become much lower than
896 * the system virtual time. In fact, to serve the queues with
897 * higher timestamps while the ones with lower timestamps are
898 * idle, the system virtual time may be pushed-up to much
899 * higher values than the finish timestamps of the idle
900 * queues. As a consequence, the finish timestamps of all new
901 * or newly activated queues may end up being much larger than
902 * those of lucky queues with backshifted timestamps. The
903 * latter queues may then monopolize the device for a lot of
904 * time. This would simply break service guarantees.
906 * To reduce this problem, push up a little bit the
907 * backshifted timestamps of the queue associated with this
908 * entity (only a queue can happen to have the backshifted
909 * flag set): just enough to let the finish timestamp of the
910 * queue be equal to the current value of the system virtual
911 * time. This may introduce a little unfairness among queues
912 * with backshifted timestamps, but it does not break
913 * worst-case fairness guarantees.
915 * As a special case, if bfqq is weight-raised, push up
916 * timestamps much less, to keep very low the probability that
917 * this push up causes the backshifted finish timestamps of
918 * weight-raised queues to become higher than the backshifted
919 * finish timestamps of non weight-raised queues.
921 if (backshifted
&& bfq_gt(st
->vtime
, entity
->finish
)) {
922 unsigned long delta
= st
->vtime
- entity
->finish
;
925 delta
/= bfqq
->wr_coeff
;
927 entity
->start
+= delta
;
928 entity
->finish
+= delta
;
931 bfq_active_insert(st
, entity
);
935 * __bfq_activate_entity - handle activation of entity.
936 * @entity: the entity being activated.
937 * @non_blocking_wait_rq: true if entity was waiting for a request
939 * Called for a 'true' activation, i.e., if entity is not active and
940 * one of its children receives a new request.
942 * Basically, this function updates the timestamps of entity and
943 * inserts entity into its active tree, after possibly extracting it
944 * from its idle tree.
946 static void __bfq_activate_entity(struct bfq_entity
*entity
,
947 bool non_blocking_wait_rq
)
949 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
950 bool backshifted
= false;
951 unsigned long long min_vstart
;
953 /* See comments on bfq_fqq_update_budg_for_activation */
954 if (non_blocking_wait_rq
&& bfq_gt(st
->vtime
, entity
->finish
)) {
956 min_vstart
= entity
->finish
;
958 min_vstart
= st
->vtime
;
960 if (entity
->tree
== &st
->idle
) {
962 * Must be on the idle tree, bfq_idle_extract() will
965 bfq_idle_extract(st
, entity
);
966 entity
->start
= bfq_gt(min_vstart
, entity
->finish
) ?
967 min_vstart
: entity
->finish
;
970 * The finish time of the entity may be invalid, and
971 * it is in the past for sure, otherwise the queue
972 * would have been on the idle tree.
974 entity
->start
= min_vstart
;
975 st
->wsum
+= entity
->weight
;
977 * entity is about to be inserted into a service tree,
978 * and then set in service: get a reference to make
979 * sure entity does not disappear until it is no
980 * longer in service or scheduled for service.
982 bfq_get_entity(entity
);
984 entity
->on_st_or_in_serv
= true;
987 #ifdef CONFIG_BFQ_GROUP_IOSCHED
988 if (!bfq_entity_to_bfqq(entity
)) { /* bfq_group */
989 struct bfq_group
*bfqg
=
990 container_of(entity
, struct bfq_group
, entity
);
991 struct bfq_data
*bfqd
= bfqg
->bfqd
;
993 if (!entity
->in_groups_with_pending_reqs
) {
994 entity
->in_groups_with_pending_reqs
= true;
995 bfqd
->num_groups_with_pending_reqs
++;
1000 bfq_update_fin_time_enqueue(entity
, st
, backshifted
);
1004 * __bfq_requeue_entity - handle requeueing or repositioning of an entity.
1005 * @entity: the entity being requeued or repositioned.
1007 * Requeueing is needed if this entity stops being served, which
1008 * happens if a leaf descendant entity has expired. On the other hand,
1009 * repositioning is needed if the next_inservice_entity for the child
1010 * entity has changed. See the comments inside the function for
1013 * Basically, this function: 1) removes entity from its active tree if
1014 * present there, 2) updates the timestamps of entity and 3) inserts
1015 * entity back into its active tree (in the new, right position for
1016 * the new values of the timestamps).
1018 static void __bfq_requeue_entity(struct bfq_entity
*entity
)
1020 struct bfq_sched_data
*sd
= entity
->sched_data
;
1021 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
1023 if (entity
== sd
->in_service_entity
) {
1025 * We are requeueing the current in-service entity,
1026 * which may have to be done for one of the following
1028 * - entity represents the in-service queue, and the
1029 * in-service queue is being requeued after an
1031 * - entity represents a group, and its budget has
1032 * changed because one of its child entities has
1033 * just been either activated or requeued for some
1034 * reason; the timestamps of the entity need then to
1035 * be updated, and the entity needs to be enqueued
1036 * or repositioned accordingly.
1038 * In particular, before requeueing, the start time of
1039 * the entity must be moved forward to account for the
1040 * service that the entity has received while in
1041 * service. This is done by the next instructions. The
1042 * finish time will then be updated according to this
1043 * new value of the start time, and to the budget of
1046 bfq_calc_finish(entity
, entity
->service
);
1047 entity
->start
= entity
->finish
;
1049 * In addition, if the entity had more than one child
1050 * when set in service, then it was not extracted from
1051 * the active tree. This implies that the position of
1052 * the entity in the active tree may need to be
1053 * changed now, because we have just updated the start
1054 * time of the entity, and we will update its finish
1055 * time in a moment (the requeueing is then, more
1056 * precisely, a repositioning in this case). To
1057 * implement this repositioning, we: 1) dequeue the
1058 * entity here, 2) update the finish time and requeue
1059 * the entity according to the new timestamps below.
1062 bfq_active_extract(st
, entity
);
1063 } else { /* The entity is already active, and not in service */
1065 * In this case, this function gets called only if the
1066 * next_in_service entity below this entity has
1067 * changed, and this change has caused the budget of
1068 * this entity to change, which, finally implies that
1069 * the finish time of this entity must be
1070 * updated. Such an update may cause the scheduling,
1071 * i.e., the position in the active tree, of this
1072 * entity to change. We handle this change by: 1)
1073 * dequeueing the entity here, 2) updating the finish
1074 * time and requeueing the entity according to the new
1075 * timestamps below. This is the same approach as the
1076 * non-extracted-entity sub-case above.
1078 bfq_active_extract(st
, entity
);
1081 bfq_update_fin_time_enqueue(entity
, st
, false);
1084 static void __bfq_activate_requeue_entity(struct bfq_entity
*entity
,
1085 struct bfq_sched_data
*sd
,
1086 bool non_blocking_wait_rq
)
1088 struct bfq_service_tree
*st
= bfq_entity_service_tree(entity
);
1090 if (sd
->in_service_entity
== entity
|| entity
->tree
== &st
->active
)
1092 * in service or already queued on the active tree,
1093 * requeue or reposition
1095 __bfq_requeue_entity(entity
);
1098 * Not in service and not queued on its active tree:
1099 * the activity is idle and this is a true activation.
1101 __bfq_activate_entity(entity
, non_blocking_wait_rq
);
1106 * bfq_activate_requeue_entity - activate or requeue an entity representing a
1107 * bfq_queue, and activate, requeue or reposition
1108 * all ancestors for which such an update becomes
1110 * @entity: the entity to activate.
1111 * @non_blocking_wait_rq: true if this entity was waiting for a request
1112 * @requeue: true if this is a requeue, which implies that bfqq is
1113 * being expired; thus ALL its ancestors stop being served and must
1114 * therefore be requeued
1115 * @expiration: true if this function is being invoked in the expiration path
1116 * of the in-service queue
1118 static void bfq_activate_requeue_entity(struct bfq_entity
*entity
,
1119 bool non_blocking_wait_rq
,
1120 bool requeue
, bool expiration
)
1122 struct bfq_sched_data
*sd
;
1124 for_each_entity(entity
) {
1125 sd
= entity
->sched_data
;
1126 __bfq_activate_requeue_entity(entity
, sd
, non_blocking_wait_rq
);
1128 if (!bfq_update_next_in_service(sd
, entity
, expiration
) &&
1135 * __bfq_deactivate_entity - update sched_data and service trees for
1136 * entity, so as to represent entity as inactive
1137 * @entity: the entity being deactivated.
1138 * @ins_into_idle_tree: if false, the entity will not be put into the
1141 * If necessary and allowed, puts entity into the idle tree. NOTE:
1142 * entity may be on no tree if in service.
1144 bool __bfq_deactivate_entity(struct bfq_entity
*entity
, bool ins_into_idle_tree
)
1146 struct bfq_sched_data
*sd
= entity
->sched_data
;
1147 struct bfq_service_tree
*st
;
1150 if (!entity
->on_st_or_in_serv
) /*
1151 * entity never activated, or
1157 * If we get here, then entity is active, which implies that
1158 * bfq_group_set_parent has already been invoked for the group
1159 * represented by entity. Therefore, the field
1160 * entity->sched_data has been set, and we can safely use it.
1162 st
= bfq_entity_service_tree(entity
);
1163 is_in_service
= entity
== sd
->in_service_entity
;
1165 bfq_calc_finish(entity
, entity
->service
);
1168 sd
->in_service_entity
= NULL
;
1171 * Non in-service entity: nobody will take care of
1172 * resetting its service counter on expiration. Do it
1175 entity
->service
= 0;
1177 if (entity
->tree
== &st
->active
)
1178 bfq_active_extract(st
, entity
);
1179 else if (!is_in_service
&& entity
->tree
== &st
->idle
)
1180 bfq_idle_extract(st
, entity
);
1182 if (!ins_into_idle_tree
|| !bfq_gt(entity
->finish
, st
->vtime
))
1183 bfq_forget_entity(st
, entity
, is_in_service
);
1185 bfq_idle_insert(st
, entity
);
1191 * bfq_deactivate_entity - deactivate an entity representing a bfq_queue.
1192 * @entity: the entity to deactivate.
1193 * @ins_into_idle_tree: true if the entity can be put into the idle tree
1194 * @expiration: true if this function is being invoked in the expiration path
1195 * of the in-service queue
1197 static void bfq_deactivate_entity(struct bfq_entity
*entity
,
1198 bool ins_into_idle_tree
,
1201 struct bfq_sched_data
*sd
;
1202 struct bfq_entity
*parent
= NULL
;
1204 for_each_entity_safe(entity
, parent
) {
1205 sd
= entity
->sched_data
;
1207 if (!__bfq_deactivate_entity(entity
, ins_into_idle_tree
)) {
1209 * entity is not in any tree any more, so
1210 * this deactivation is a no-op, and there is
1211 * nothing to change for upper-level entities
1212 * (in case of expiration, this can never
1218 if (sd
->next_in_service
== entity
)
1220 * entity was the next_in_service entity,
1221 * then, since entity has just been
1222 * deactivated, a new one must be found.
1224 bfq_update_next_in_service(sd
, NULL
, expiration
);
1226 if (sd
->next_in_service
|| sd
->in_service_entity
) {
1228 * The parent entity is still active, because
1229 * either next_in_service or in_service_entity
1230 * is not NULL. So, no further upwards
1231 * deactivation must be performed. Yet,
1232 * next_in_service has changed. Then the
1233 * schedule does need to be updated upwards.
1235 * NOTE If in_service_entity is not NULL, then
1236 * next_in_service may happen to be NULL,
1237 * although the parent entity is evidently
1238 * active. This happens if 1) the entity
1239 * pointed by in_service_entity is the only
1240 * active entity in the parent entity, and 2)
1241 * according to the definition of
1242 * next_in_service, the in_service_entity
1243 * cannot be considered as
1244 * next_in_service. See the comments on the
1245 * definition of next_in_service for details.
1251 * If we get here, then the parent is no more
1252 * backlogged and we need to propagate the
1253 * deactivation upwards. Thus let the loop go on.
1257 * Also let parent be queued into the idle tree on
1258 * deactivation, to preserve service guarantees, and
1259 * assuming that who invoked this function does not
1260 * need parent entities too to be removed completely.
1262 ins_into_idle_tree
= true;
1266 * If the deactivation loop is fully executed, then there are
1267 * no more entities to touch and next loop is not executed at
1268 * all. Otherwise, requeue remaining entities if they are
1269 * about to stop receiving service, or reposition them if this
1273 for_each_entity(entity
) {
1275 * Invoke __bfq_requeue_entity on entity, even if
1276 * already active, to requeue/reposition it in the
1277 * active tree (because sd->next_in_service has
1280 __bfq_requeue_entity(entity
);
1282 sd
= entity
->sched_data
;
1283 if (!bfq_update_next_in_service(sd
, entity
, expiration
) &&
1286 * next_in_service unchanged or not causing
1287 * any change in entity->parent->sd, and no
1288 * requeueing needed for expiration: stop
1296 * bfq_calc_vtime_jump - compute the value to which the vtime should jump,
1297 * if needed, to have at least one entity eligible.
1298 * @st: the service tree to act upon.
1300 * Assumes that st is not empty.
1302 static u64
bfq_calc_vtime_jump(struct bfq_service_tree
*st
)
1304 struct bfq_entity
*root_entity
= bfq_root_active_entity(&st
->active
);
1306 if (bfq_gt(root_entity
->min_start
, st
->vtime
))
1307 return root_entity
->min_start
;
1312 static void bfq_update_vtime(struct bfq_service_tree
*st
, u64 new_value
)
1314 if (new_value
> st
->vtime
) {
1315 st
->vtime
= new_value
;
1316 bfq_forget_idle(st
);
1321 * bfq_first_active_entity - find the eligible entity with
1322 * the smallest finish time
1323 * @st: the service tree to select from.
1324 * @vtime: the system virtual to use as a reference for eligibility
1326 * This function searches the first schedulable entity, starting from the
1327 * root of the tree and going on the left every time on this side there is
1328 * a subtree with at least one eligible (start <= vtime) entity. The path on
1329 * the right is followed only if a) the left subtree contains no eligible
1330 * entities and b) no eligible entity has been found yet.
1332 static struct bfq_entity
*bfq_first_active_entity(struct bfq_service_tree
*st
,
1335 struct bfq_entity
*entry
, *first
= NULL
;
1336 struct rb_node
*node
= st
->active
.rb_node
;
1339 entry
= rb_entry(node
, struct bfq_entity
, rb_node
);
1341 if (!bfq_gt(entry
->start
, vtime
))
1344 if (node
->rb_left
) {
1345 entry
= rb_entry(node
->rb_left
,
1346 struct bfq_entity
, rb_node
);
1347 if (!bfq_gt(entry
->min_start
, vtime
)) {
1348 node
= node
->rb_left
;
1354 node
= node
->rb_right
;
1361 * __bfq_lookup_next_entity - return the first eligible entity in @st.
1362 * @st: the service tree.
1363 * @in_service: whether or not there is an in-service entity for the sched_data
1364 * this active tree belongs to.
1366 * If there is no in-service entity for the sched_data st belongs to,
1367 * then return the entity that will be set in service if:
1368 * 1) the parent entity this st belongs to is set in service;
1369 * 2) no entity belonging to such parent entity undergoes a state change
1370 * that would influence the timestamps of the entity (e.g., becomes idle,
1371 * becomes backlogged, changes its budget, ...).
1373 * In this first case, update the virtual time in @st too (see the
1374 * comments on this update inside the function).
1376 * In contrast, if there is an in-service entity, then return the
1377 * entity that would be set in service if not only the above
1378 * conditions, but also the next one held true: the currently
1379 * in-service entity, on expiration,
1380 * 1) gets a finish time equal to the current one, or
1381 * 2) is not eligible any more, or
1384 static struct bfq_entity
*
1385 __bfq_lookup_next_entity(struct bfq_service_tree
*st
, bool in_service
)
1387 struct bfq_entity
*entity
;
1390 if (RB_EMPTY_ROOT(&st
->active
))
1394 * Get the value of the system virtual time for which at
1395 * least one entity is eligible.
1397 new_vtime
= bfq_calc_vtime_jump(st
);
1400 * If there is no in-service entity for the sched_data this
1401 * active tree belongs to, then push the system virtual time
1402 * up to the value that guarantees that at least one entity is
1403 * eligible. If, instead, there is an in-service entity, then
1404 * do not make any such update, because there is already an
1405 * eligible entity, namely the in-service one (even if the
1406 * entity is not on st, because it was extracted when set in
1410 bfq_update_vtime(st
, new_vtime
);
1412 entity
= bfq_first_active_entity(st
, new_vtime
);
1418 * bfq_lookup_next_entity - return the first eligible entity in @sd.
1419 * @sd: the sched_data.
1420 * @expiration: true if we are on the expiration path of the in-service queue
1422 * This function is invoked when there has been a change in the trees
1423 * for sd, and we need to know what is the new next entity to serve
1424 * after this change.
1426 static struct bfq_entity
*bfq_lookup_next_entity(struct bfq_sched_data
*sd
,
1429 struct bfq_service_tree
*st
= sd
->service_tree
;
1430 struct bfq_service_tree
*idle_class_st
= st
+ (BFQ_IOPRIO_CLASSES
- 1);
1431 struct bfq_entity
*entity
= NULL
;
1435 * Choose from idle class, if needed to guarantee a minimum
1436 * bandwidth to this class (and if there is some active entity
1437 * in idle class). This should also mitigate
1438 * priority-inversion problems in case a low priority task is
1439 * holding file system resources.
1441 if (time_is_before_jiffies(sd
->bfq_class_idle_last_service
+
1442 BFQ_CL_IDLE_TIMEOUT
)) {
1443 if (!RB_EMPTY_ROOT(&idle_class_st
->active
))
1444 class_idx
= BFQ_IOPRIO_CLASSES
- 1;
1445 /* About to be served if backlogged, or not yet backlogged */
1446 sd
->bfq_class_idle_last_service
= jiffies
;
1450 * Find the next entity to serve for the highest-priority
1451 * class, unless the idle class needs to be served.
1453 for (; class_idx
< BFQ_IOPRIO_CLASSES
; class_idx
++) {
1455 * If expiration is true, then bfq_lookup_next_entity
1456 * is being invoked as a part of the expiration path
1457 * of the in-service queue. In this case, even if
1458 * sd->in_service_entity is not NULL,
1459 * sd->in_service_entity at this point is actually not
1460 * in service any more, and, if needed, has already
1461 * been properly queued or requeued into the right
1462 * tree. The reason why sd->in_service_entity is still
1463 * not NULL here, even if expiration is true, is that
1464 * sd->in_service_entity is reset as a last step in the
1465 * expiration path. So, if expiration is true, tell
1466 * __bfq_lookup_next_entity that there is no
1467 * sd->in_service_entity.
1469 entity
= __bfq_lookup_next_entity(st
+ class_idx
,
1470 sd
->in_service_entity
&&
1480 bool next_queue_may_preempt(struct bfq_data
*bfqd
)
1482 struct bfq_sched_data
*sd
= &bfqd
->root_group
->sched_data
;
1484 return sd
->next_in_service
!= sd
->in_service_entity
;
1488 * Get next queue for service.
1490 struct bfq_queue
*bfq_get_next_queue(struct bfq_data
*bfqd
)
1492 struct bfq_entity
*entity
= NULL
;
1493 struct bfq_sched_data
*sd
;
1494 struct bfq_queue
*bfqq
;
1496 if (bfq_tot_busy_queues(bfqd
) == 0)
1500 * Traverse the path from the root to the leaf entity to
1501 * serve. Set in service all the entities visited along the
1504 sd
= &bfqd
->root_group
->sched_data
;
1505 for (; sd
; sd
= entity
->my_sched_data
) {
1507 * WARNING. We are about to set the in-service entity
1508 * to sd->next_in_service, i.e., to the (cached) value
1509 * returned by bfq_lookup_next_entity(sd) the last
1510 * time it was invoked, i.e., the last time when the
1511 * service order in sd changed as a consequence of the
1512 * activation or deactivation of an entity. In this
1513 * respect, if we execute bfq_lookup_next_entity(sd)
1514 * in this very moment, it may, although with low
1515 * probability, yield a different entity than that
1516 * pointed to by sd->next_in_service. This rare event
1517 * happens in case there was no CLASS_IDLE entity to
1518 * serve for sd when bfq_lookup_next_entity(sd) was
1519 * invoked for the last time, while there is now one
1522 * If the above event happens, then the scheduling of
1523 * such entity in CLASS_IDLE is postponed until the
1524 * service of the sd->next_in_service entity
1525 * finishes. In fact, when the latter is expired,
1526 * bfq_lookup_next_entity(sd) gets called again,
1527 * exactly to update sd->next_in_service.
1530 /* Make next_in_service entity become in_service_entity */
1531 entity
= sd
->next_in_service
;
1532 sd
->in_service_entity
= entity
;
1535 * If entity is no longer a candidate for next
1536 * service, then it must be extracted from its active
1537 * tree, so as to make sure that it won't be
1538 * considered when computing next_in_service. See the
1539 * comments on the function
1540 * bfq_no_longer_next_in_service() for details.
1542 if (bfq_no_longer_next_in_service(entity
))
1543 bfq_active_extract(bfq_entity_service_tree(entity
),
1547 * Even if entity is not to be extracted according to
1548 * the above check, a descendant entity may get
1549 * extracted in one of the next iterations of this
1550 * loop. Such an event could cause a change in
1551 * next_in_service for the level of the descendant
1552 * entity, and thus possibly back to this level.
1554 * However, we cannot perform the resulting needed
1555 * update of next_in_service for this level before the
1556 * end of the whole loop, because, to know which is
1557 * the correct next-to-serve candidate entity for each
1558 * level, we need first to find the leaf entity to set
1559 * in service. In fact, only after we know which is
1560 * the next-to-serve leaf entity, we can discover
1561 * whether the parent entity of the leaf entity
1562 * becomes the next-to-serve, and so on.
1566 bfqq
= bfq_entity_to_bfqq(entity
);
1569 * We can finally update all next-to-serve entities along the
1570 * path from the leaf entity just set in service to the root.
1572 for_each_entity(entity
) {
1573 struct bfq_sched_data
*sd
= entity
->sched_data
;
1575 if (!bfq_update_next_in_service(sd
, NULL
, false))
1582 /* returns true if the in-service queue gets freed */
1583 bool __bfq_bfqd_reset_in_service(struct bfq_data
*bfqd
)
1585 struct bfq_queue
*in_serv_bfqq
= bfqd
->in_service_queue
;
1586 struct bfq_entity
*in_serv_entity
= &in_serv_bfqq
->entity
;
1587 struct bfq_entity
*entity
= in_serv_entity
;
1589 bfq_clear_bfqq_wait_request(in_serv_bfqq
);
1590 hrtimer_try_to_cancel(&bfqd
->idle_slice_timer
);
1591 bfqd
->in_service_queue
= NULL
;
1594 * When this function is called, all in-service entities have
1595 * been properly deactivated or requeued, so we can safely
1596 * execute the final step: reset in_service_entity along the
1597 * path from entity to the root.
1599 for_each_entity(entity
)
1600 entity
->sched_data
->in_service_entity
= NULL
;
1603 * in_serv_entity is no longer in service, so, if it is in no
1604 * service tree either, then release the service reference to
1605 * the queue it represents (taken with bfq_get_entity).
1607 if (!in_serv_entity
->on_st_or_in_serv
) {
1609 * If no process is referencing in_serv_bfqq any
1610 * longer, then the service reference may be the only
1611 * reference to the queue. If this is the case, then
1612 * bfqq gets freed here.
1614 int ref
= in_serv_bfqq
->ref
;
1615 bfq_put_queue(in_serv_bfqq
);
1623 void bfq_deactivate_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1624 bool ins_into_idle_tree
, bool expiration
)
1626 struct bfq_entity
*entity
= &bfqq
->entity
;
1628 bfq_deactivate_entity(entity
, ins_into_idle_tree
, expiration
);
1631 void bfq_activate_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
)
1633 struct bfq_entity
*entity
= &bfqq
->entity
;
1635 bfq_activate_requeue_entity(entity
, bfq_bfqq_non_blocking_wait_rq(bfqq
),
1637 bfq_clear_bfqq_non_blocking_wait_rq(bfqq
);
1640 void bfq_requeue_bfqq(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1643 struct bfq_entity
*entity
= &bfqq
->entity
;
1645 bfq_activate_requeue_entity(entity
, false,
1646 bfqq
== bfqd
->in_service_queue
, expiration
);
1650 * Called when the bfqq no longer has requests pending, remove it from
1651 * the service tree. As a special case, it can be invoked during an
1654 void bfq_del_bfqq_busy(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
,
1657 bfq_log_bfqq(bfqd
, bfqq
, "del from busy");
1659 bfq_clear_bfqq_busy(bfqq
);
1661 bfqd
->busy_queues
[bfqq
->ioprio_class
- 1]--;
1663 if (bfqq
->wr_coeff
> 1)
1664 bfqd
->wr_busy_queues
--;
1666 bfqg_stats_update_dequeue(bfqq_group(bfqq
));
1668 bfq_deactivate_bfqq(bfqd
, bfqq
, true, expiration
);
1670 if (!bfqq
->dispatched
)
1671 bfq_weights_tree_remove(bfqd
, bfqq
);
1675 * Called when an inactive queue receives a new request.
1677 void bfq_add_bfqq_busy(struct bfq_data
*bfqd
, struct bfq_queue
*bfqq
)
1679 bfq_log_bfqq(bfqd
, bfqq
, "add to busy");
1681 bfq_activate_bfqq(bfqd
, bfqq
);
1683 bfq_mark_bfqq_busy(bfqq
);
1684 bfqd
->busy_queues
[bfqq
->ioprio_class
- 1]++;
1686 if (!bfqq
->dispatched
)
1687 if (bfqq
->wr_coeff
== 1)
1688 bfq_weights_tree_add(bfqd
, bfqq
,
1689 &bfqd
->queue_weights_tree
);
1691 if (bfqq
->wr_coeff
> 1)
1692 bfqd
->wr_busy_queues
++;
1694 /* Move bfqq to the head of the woken list of its waker */
1695 if (!hlist_unhashed(&bfqq
->woken_list_node
) &&
1696 &bfqq
->woken_list_node
!= bfqq
->waker_bfqq
->woken_list
.first
) {
1697 hlist_del_init(&bfqq
->woken_list_node
);
1698 hlist_add_head(&bfqq
->woken_list_node
,
1699 &bfqq
->waker_bfqq
->woken_list
);