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1717 lines
53 KiB
1717 lines
53 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Hierarchical Budget Worst-case Fair Weighted Fair Queueing |
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* (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O |
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* scheduler schedules generic entities. The latter can represent |
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* either single bfq queues (associated with processes) or groups of |
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* bfq queues (associated with cgroups). |
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*/ |
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#include "bfq-iosched.h" |
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|
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/** |
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* bfq_gt - compare two timestamps. |
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* @a: first ts. |
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* @b: second ts. |
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* |
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* Return @a > @b, dealing with wrapping correctly. |
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*/ |
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static int bfq_gt(u64 a, u64 b) |
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{ |
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return (s64)(a - b) > 0; |
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} |
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|
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static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree) |
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{ |
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struct rb_node *node = tree->rb_node; |
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|
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return rb_entry(node, struct bfq_entity, rb_node); |
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} |
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|
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static unsigned int bfq_class_idx(struct bfq_entity *entity) |
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{ |
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struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
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|
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return bfqq ? bfqq->ioprio_class - 1 : |
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BFQ_DEFAULT_GRP_CLASS - 1; |
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} |
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|
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unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd) |
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{ |
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return bfqd->busy_queues[0] + bfqd->busy_queues[1] + |
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bfqd->busy_queues[2]; |
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} |
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|
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static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, |
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bool expiration); |
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static bool bfq_update_parent_budget(struct bfq_entity *next_in_service); |
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|
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/** |
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* bfq_update_next_in_service - update sd->next_in_service |
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* @sd: sched_data for which to perform the update. |
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* @new_entity: if not NULL, pointer to the entity whose activation, |
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* requeueing or repositioning triggered the invocation of |
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* this function. |
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* @expiration: id true, this function is being invoked after the |
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* expiration of the in-service entity |
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* |
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* This function is called to update sd->next_in_service, which, in |
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* its turn, may change as a consequence of the insertion or |
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* extraction of an entity into/from one of the active trees of |
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* sd. These insertions/extractions occur as a consequence of |
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* activations/deactivations of entities, with some activations being |
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* 'true' activations, and other activations being requeueings (i.e., |
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* implementing the second, requeueing phase of the mechanism used to |
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* reposition an entity in its active tree; see comments on |
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* __bfq_activate_entity and __bfq_requeue_entity for details). In |
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* both the last two activation sub-cases, new_entity points to the |
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* just activated or requeued entity. |
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* |
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* Returns true if sd->next_in_service changes in such a way that |
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* entity->parent may become the next_in_service for its parent |
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* entity. |
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*/ |
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static bool bfq_update_next_in_service(struct bfq_sched_data *sd, |
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struct bfq_entity *new_entity, |
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bool expiration) |
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{ |
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struct bfq_entity *next_in_service = sd->next_in_service; |
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bool parent_sched_may_change = false; |
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bool change_without_lookup = false; |
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|
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/* |
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* If this update is triggered by the activation, requeueing |
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* or repositioning of an entity that does not coincide with |
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* sd->next_in_service, then a full lookup in the active tree |
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* can be avoided. In fact, it is enough to check whether the |
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* just-modified entity has the same priority as |
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* sd->next_in_service, is eligible and has a lower virtual |
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* finish time than sd->next_in_service. If this compound |
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* condition holds, then the new entity becomes the new |
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* next_in_service. Otherwise no change is needed. |
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*/ |
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if (new_entity && new_entity != sd->next_in_service) { |
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/* |
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* Flag used to decide whether to replace |
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* sd->next_in_service with new_entity. Tentatively |
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* set to true, and left as true if |
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* sd->next_in_service is NULL. |
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*/ |
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change_without_lookup = true; |
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|
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/* |
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* If there is already a next_in_service candidate |
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* entity, then compare timestamps to decide whether |
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* to replace sd->service_tree with new_entity. |
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*/ |
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if (next_in_service) { |
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unsigned int new_entity_class_idx = |
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bfq_class_idx(new_entity); |
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struct bfq_service_tree *st = |
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sd->service_tree + new_entity_class_idx; |
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|
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change_without_lookup = |
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(new_entity_class_idx == |
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bfq_class_idx(next_in_service) |
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&& |
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!bfq_gt(new_entity->start, st->vtime) |
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&& |
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bfq_gt(next_in_service->finish, |
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new_entity->finish)); |
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} |
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if (change_without_lookup) |
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next_in_service = new_entity; |
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} |
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if (!change_without_lookup) /* lookup needed */ |
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next_in_service = bfq_lookup_next_entity(sd, expiration); |
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|
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if (next_in_service) { |
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bool new_budget_triggers_change = |
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bfq_update_parent_budget(next_in_service); |
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parent_sched_may_change = !sd->next_in_service || |
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new_budget_triggers_change; |
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} |
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sd->next_in_service = next_in_service; |
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return parent_sched_may_change; |
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} |
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#ifdef CONFIG_BFQ_GROUP_IOSCHED |
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struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) |
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{ |
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struct bfq_entity *group_entity = bfqq->entity.parent; |
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|
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if (!group_entity) |
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group_entity = &bfqq->bfqd->root_group->entity; |
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return container_of(group_entity, struct bfq_group, entity); |
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} |
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|
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/* |
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* Returns true if this budget changes may let next_in_service->parent |
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* become the next_in_service entity for its parent entity. |
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*/ |
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static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) |
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{ |
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struct bfq_entity *bfqg_entity; |
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struct bfq_group *bfqg; |
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struct bfq_sched_data *group_sd; |
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bool ret = false; |
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group_sd = next_in_service->sched_data; |
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bfqg = container_of(group_sd, struct bfq_group, sched_data); |
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/* |
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* bfq_group's my_entity field is not NULL only if the group |
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* is not the root group. We must not touch the root entity |
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* as it must never become an in-service entity. |
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*/ |
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bfqg_entity = bfqg->my_entity; |
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if (bfqg_entity) { |
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if (bfqg_entity->budget > next_in_service->budget) |
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ret = true; |
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bfqg_entity->budget = next_in_service->budget; |
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} |
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|
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return ret; |
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} |
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|
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/* |
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* This function tells whether entity stops being a candidate for next |
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* service, according to the restrictive definition of the field |
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* next_in_service. In particular, this function is invoked for an |
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* entity that is about to be set in service. |
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* |
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* If entity is a queue, then the entity is no longer a candidate for |
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* next service according to the that definition, because entity is |
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* about to become the in-service queue. This function then returns |
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* true if entity is a queue. |
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* |
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* In contrast, entity could still be a candidate for next service if |
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* it is not a queue, and has more than one active child. In fact, |
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* even if one of its children is about to be set in service, other |
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* active children may still be the next to serve, for the parent |
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* entity, even according to the above definition. As a consequence, a |
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* non-queue entity is not a candidate for next-service only if it has |
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* only one active child. And only if this condition holds, then this |
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* function returns true for a non-queue entity. |
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*/ |
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static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) |
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{ |
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struct bfq_group *bfqg; |
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|
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if (bfq_entity_to_bfqq(entity)) |
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return true; |
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bfqg = container_of(entity, struct bfq_group, entity); |
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|
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/* |
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* The field active_entities does not always contain the |
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* actual number of active children entities: it happens to |
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* not account for the in-service entity in case the latter is |
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* removed from its active tree (which may get done after |
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* invoking the function bfq_no_longer_next_in_service in |
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* bfq_get_next_queue). Fortunately, here, i.e., while |
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* bfq_no_longer_next_in_service is not yet completed in |
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* bfq_get_next_queue, bfq_active_extract has not yet been |
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* invoked, and thus active_entities still coincides with the |
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* actual number of active entities. |
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*/ |
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if (bfqg->active_entities == 1) |
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return true; |
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|
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return false; |
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} |
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#else /* CONFIG_BFQ_GROUP_IOSCHED */ |
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struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) |
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{ |
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return bfqq->bfqd->root_group; |
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} |
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static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) |
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{ |
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return false; |
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} |
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static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) |
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{ |
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return true; |
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} |
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#endif /* CONFIG_BFQ_GROUP_IOSCHED */ |
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|
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/* |
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* Shift for timestamp calculations. This actually limits the maximum |
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* service allowed in one timestamp delta (small shift values increase it), |
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* the maximum total weight that can be used for the queues in the system |
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* (big shift values increase it), and the period of virtual time |
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* wraparounds. |
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*/ |
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#define WFQ_SERVICE_SHIFT 22 |
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struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) |
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{ |
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struct bfq_queue *bfqq = NULL; |
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|
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if (!entity->my_sched_data) |
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bfqq = container_of(entity, struct bfq_queue, entity); |
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return bfqq; |
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} |
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/** |
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* bfq_delta - map service into the virtual time domain. |
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* @service: amount of service. |
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* @weight: scale factor (weight of an entity or weight sum). |
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*/ |
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static u64 bfq_delta(unsigned long service, unsigned long weight) |
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{ |
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return div64_ul((u64)service << WFQ_SERVICE_SHIFT, weight); |
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} |
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|
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/** |
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* bfq_calc_finish - assign the finish time to an entity. |
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* @entity: the entity to act upon. |
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* @service: the service to be charged to the entity. |
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*/ |
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static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) |
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{ |
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struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
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entity->finish = entity->start + |
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bfq_delta(service, entity->weight); |
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if (bfqq) { |
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bfq_log_bfqq(bfqq->bfqd, bfqq, |
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"calc_finish: serv %lu, w %d", |
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service, entity->weight); |
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bfq_log_bfqq(bfqq->bfqd, bfqq, |
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"calc_finish: start %llu, finish %llu, delta %llu", |
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entity->start, entity->finish, |
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bfq_delta(service, entity->weight)); |
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} |
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} |
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|
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/** |
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* bfq_entity_of - get an entity from a node. |
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* @node: the node field of the entity. |
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* |
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* Convert a node pointer to the relative entity. This is used only |
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* to simplify the logic of some functions and not as the generic |
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* conversion mechanism because, e.g., in the tree walking functions, |
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* the check for a %NULL value would be redundant. |
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*/ |
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struct bfq_entity *bfq_entity_of(struct rb_node *node) |
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{ |
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struct bfq_entity *entity = NULL; |
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if (node) |
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entity = rb_entry(node, struct bfq_entity, rb_node); |
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return entity; |
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} |
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|
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/** |
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* bfq_extract - remove an entity from a tree. |
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* @root: the tree root. |
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* @entity: the entity to remove. |
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*/ |
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static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) |
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{ |
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entity->tree = NULL; |
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rb_erase(&entity->rb_node, root); |
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} |
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|
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/** |
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* bfq_idle_extract - extract an entity from the idle tree. |
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* @st: the service tree of the owning @entity. |
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* @entity: the entity being removed. |
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*/ |
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static void bfq_idle_extract(struct bfq_service_tree *st, |
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struct bfq_entity *entity) |
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{ |
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struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
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struct rb_node *next; |
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|
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if (entity == st->first_idle) { |
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next = rb_next(&entity->rb_node); |
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st->first_idle = bfq_entity_of(next); |
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} |
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if (entity == st->last_idle) { |
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next = rb_prev(&entity->rb_node); |
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st->last_idle = bfq_entity_of(next); |
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} |
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bfq_extract(&st->idle, entity); |
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if (bfqq) |
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list_del(&bfqq->bfqq_list); |
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} |
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|
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/** |
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* bfq_insert - generic tree insertion. |
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* @root: tree root. |
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* @entity: entity to insert. |
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* |
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* This is used for the idle and the active tree, since they are both |
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* ordered by finish time. |
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*/ |
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static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) |
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{ |
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struct bfq_entity *entry; |
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struct rb_node **node = &root->rb_node; |
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struct rb_node *parent = NULL; |
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|
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while (*node) { |
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parent = *node; |
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entry = rb_entry(parent, struct bfq_entity, rb_node); |
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if (bfq_gt(entry->finish, entity->finish)) |
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node = &parent->rb_left; |
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else |
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node = &parent->rb_right; |
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} |
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rb_link_node(&entity->rb_node, parent, node); |
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rb_insert_color(&entity->rb_node, root); |
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|
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entity->tree = root; |
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} |
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|
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/** |
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* bfq_update_min - update the min_start field of a entity. |
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* @entity: the entity to update. |
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* @node: one of its children. |
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* |
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* This function is called when @entity may store an invalid value for |
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* min_start due to updates to the active tree. The function assumes |
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* that the subtree rooted at @node (which may be its left or its right |
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* child) has a valid min_start value. |
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*/ |
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static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) |
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{ |
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struct bfq_entity *child; |
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|
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if (node) { |
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child = rb_entry(node, struct bfq_entity, rb_node); |
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if (bfq_gt(entity->min_start, child->min_start)) |
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entity->min_start = child->min_start; |
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} |
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} |
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|
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/** |
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* bfq_update_active_node - recalculate min_start. |
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* @node: the node to update. |
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* |
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* @node may have changed position or one of its children may have moved, |
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* this function updates its min_start value. The left and right subtrees |
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* are assumed to hold a correct min_start value. |
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*/ |
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static void bfq_update_active_node(struct rb_node *node) |
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{ |
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struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); |
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|
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entity->min_start = entity->start; |
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bfq_update_min(entity, node->rb_right); |
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bfq_update_min(entity, node->rb_left); |
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} |
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|
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/** |
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* bfq_update_active_tree - update min_start for the whole active tree. |
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* @node: the starting node. |
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* |
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* @node must be the deepest modified node after an update. This function |
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* updates its min_start using the values held by its children, assuming |
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* that they did not change, and then updates all the nodes that may have |
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* changed in the path to the root. The only nodes that may have changed |
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* are the ones in the path or their siblings. |
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*/ |
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static void bfq_update_active_tree(struct rb_node *node) |
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{ |
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struct rb_node *parent; |
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|
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up: |
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bfq_update_active_node(node); |
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|
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parent = rb_parent(node); |
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if (!parent) |
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return; |
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|
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if (node == parent->rb_left && parent->rb_right) |
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bfq_update_active_node(parent->rb_right); |
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else if (parent->rb_left) |
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bfq_update_active_node(parent->rb_left); |
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|
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node = parent; |
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goto up; |
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} |
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|
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/** |
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* bfq_active_insert - insert an entity in the active tree of its |
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* group/device. |
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* @st: the service tree of the entity. |
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* @entity: the entity being inserted. |
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* |
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* The active tree is ordered by finish time, but an extra key is kept |
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* per each node, containing the minimum value for the start times of |
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* its children (and the node itself), so it's possible to search for |
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* the eligible node with the lowest finish time in logarithmic time. |
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*/ |
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static void bfq_active_insert(struct bfq_service_tree *st, |
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struct bfq_entity *entity) |
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{ |
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struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
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struct rb_node *node = &entity->rb_node; |
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#ifdef CONFIG_BFQ_GROUP_IOSCHED |
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struct bfq_sched_data *sd = NULL; |
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struct bfq_group *bfqg = NULL; |
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struct bfq_data *bfqd = NULL; |
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#endif |
|
|
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bfq_insert(&st->active, entity); |
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|
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if (node->rb_left) |
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node = node->rb_left; |
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else if (node->rb_right) |
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node = node->rb_right; |
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|
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bfq_update_active_tree(node); |
|
|
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#ifdef CONFIG_BFQ_GROUP_IOSCHED |
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sd = entity->sched_data; |
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bfqg = container_of(sd, struct bfq_group, sched_data); |
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bfqd = (struct bfq_data *)bfqg->bfqd; |
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#endif |
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if (bfqq) |
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list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); |
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#ifdef CONFIG_BFQ_GROUP_IOSCHED |
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if (bfqg != bfqd->root_group) |
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bfqg->active_entities++; |
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#endif |
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} |
|
|
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/** |
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* bfq_ioprio_to_weight - calc a weight from an ioprio. |
|
* @ioprio: the ioprio value to convert. |
|
*/ |
|
unsigned short bfq_ioprio_to_weight(int ioprio) |
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{ |
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return (IOPRIO_NR_LEVELS - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; |
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} |
|
|
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/** |
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* bfq_weight_to_ioprio - calc an ioprio from a weight. |
|
* @weight: the weight value to convert. |
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* |
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* To preserve as much as possible the old only-ioprio user interface, |
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* 0 is used as an escape ioprio value for weights (numerically) equal or |
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* larger than IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF. |
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*/ |
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static unsigned short bfq_weight_to_ioprio(int weight) |
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{ |
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return max_t(int, 0, |
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IOPRIO_NR_LEVELS * BFQ_WEIGHT_CONVERSION_COEFF - weight); |
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} |
|
|
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static void bfq_get_entity(struct bfq_entity *entity) |
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{ |
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struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
|
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if (bfqq) { |
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bfqq->ref++; |
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bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", |
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bfqq, bfqq->ref); |
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} |
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} |
|
|
|
/** |
|
* bfq_find_deepest - find the deepest node that an extraction can modify. |
|
* @node: the node being removed. |
|
* |
|
* Do the first step of an extraction in an rb tree, looking for the |
|
* node that will replace @node, and returning the deepest node that |
|
* the following modifications to the tree can touch. If @node is the |
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* last node in the tree return %NULL. |
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*/ |
|
static struct rb_node *bfq_find_deepest(struct rb_node *node) |
|
{ |
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struct rb_node *deepest; |
|
|
|
if (!node->rb_right && !node->rb_left) |
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deepest = rb_parent(node); |
|
else if (!node->rb_right) |
|
deepest = node->rb_left; |
|
else if (!node->rb_left) |
|
deepest = node->rb_right; |
|
else { |
|
deepest = rb_next(node); |
|
if (deepest->rb_right) |
|
deepest = deepest->rb_right; |
|
else if (rb_parent(deepest) != node) |
|
deepest = rb_parent(deepest); |
|
} |
|
|
|
return deepest; |
|
} |
|
|
|
/** |
|
* bfq_active_extract - remove an entity from the active tree. |
|
* @st: the service_tree containing the tree. |
|
* @entity: the entity being removed. |
|
*/ |
|
static void bfq_active_extract(struct bfq_service_tree *st, |
|
struct bfq_entity *entity) |
|
{ |
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
struct rb_node *node; |
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
struct bfq_sched_data *sd = NULL; |
|
struct bfq_group *bfqg = NULL; |
|
struct bfq_data *bfqd = NULL; |
|
#endif |
|
|
|
node = bfq_find_deepest(&entity->rb_node); |
|
bfq_extract(&st->active, entity); |
|
|
|
if (node) |
|
bfq_update_active_tree(node); |
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
sd = entity->sched_data; |
|
bfqg = container_of(sd, struct bfq_group, sched_data); |
|
bfqd = (struct bfq_data *)bfqg->bfqd; |
|
#endif |
|
if (bfqq) |
|
list_del(&bfqq->bfqq_list); |
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
if (bfqg != bfqd->root_group) |
|
bfqg->active_entities--; |
|
#endif |
|
} |
|
|
|
/** |
|
* bfq_idle_insert - insert an entity into the idle tree. |
|
* @st: the service tree containing the tree. |
|
* @entity: the entity to insert. |
|
*/ |
|
static void bfq_idle_insert(struct bfq_service_tree *st, |
|
struct bfq_entity *entity) |
|
{ |
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
struct bfq_entity *first_idle = st->first_idle; |
|
struct bfq_entity *last_idle = st->last_idle; |
|
|
|
if (!first_idle || bfq_gt(first_idle->finish, entity->finish)) |
|
st->first_idle = entity; |
|
if (!last_idle || bfq_gt(entity->finish, last_idle->finish)) |
|
st->last_idle = entity; |
|
|
|
bfq_insert(&st->idle, entity); |
|
|
|
if (bfqq) |
|
list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list); |
|
} |
|
|
|
/** |
|
* bfq_forget_entity - do not consider entity any longer for scheduling |
|
* @st: the service tree. |
|
* @entity: the entity being removed. |
|
* @is_in_service: true if entity is currently the in-service entity. |
|
* |
|
* Forget everything about @entity. In addition, if entity represents |
|
* a queue, and the latter is not in service, then release the service |
|
* reference to the queue (the one taken through bfq_get_entity). In |
|
* fact, in this case, there is really no more service reference to |
|
* the queue, as the latter is also outside any service tree. If, |
|
* instead, the queue is in service, then __bfq_bfqd_reset_in_service |
|
* will take care of putting the reference when the queue finally |
|
* stops being served. |
|
*/ |
|
static void bfq_forget_entity(struct bfq_service_tree *st, |
|
struct bfq_entity *entity, |
|
bool is_in_service) |
|
{ |
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
|
|
entity->on_st_or_in_serv = false; |
|
st->wsum -= entity->weight; |
|
if (bfqq && !is_in_service) |
|
bfq_put_queue(bfqq); |
|
} |
|
|
|
/** |
|
* bfq_put_idle_entity - release the idle tree ref of an entity. |
|
* @st: service tree for the entity. |
|
* @entity: the entity being released. |
|
*/ |
|
void bfq_put_idle_entity(struct bfq_service_tree *st, struct bfq_entity *entity) |
|
{ |
|
bfq_idle_extract(st, entity); |
|
bfq_forget_entity(st, entity, |
|
entity == entity->sched_data->in_service_entity); |
|
} |
|
|
|
/** |
|
* bfq_forget_idle - update the idle tree if necessary. |
|
* @st: the service tree to act upon. |
|
* |
|
* To preserve the global O(log N) complexity we only remove one entry here; |
|
* as the idle tree will not grow indefinitely this can be done safely. |
|
*/ |
|
static void bfq_forget_idle(struct bfq_service_tree *st) |
|
{ |
|
struct bfq_entity *first_idle = st->first_idle; |
|
struct bfq_entity *last_idle = st->last_idle; |
|
|
|
if (RB_EMPTY_ROOT(&st->active) && last_idle && |
|
!bfq_gt(last_idle->finish, st->vtime)) { |
|
/* |
|
* Forget the whole idle tree, increasing the vtime past |
|
* the last finish time of idle entities. |
|
*/ |
|
st->vtime = last_idle->finish; |
|
} |
|
|
|
if (first_idle && !bfq_gt(first_idle->finish, st->vtime)) |
|
bfq_put_idle_entity(st, first_idle); |
|
} |
|
|
|
struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity) |
|
{ |
|
struct bfq_sched_data *sched_data = entity->sched_data; |
|
unsigned int idx = bfq_class_idx(entity); |
|
|
|
return sched_data->service_tree + idx; |
|
} |
|
|
|
/* |
|
* Update weight and priority of entity. If update_class_too is true, |
|
* then update the ioprio_class of entity too. |
|
* |
|
* The reason why the update of ioprio_class is controlled through the |
|
* last parameter is as follows. Changing the ioprio class of an |
|
* entity implies changing the destination service trees for that |
|
* entity. If such a change occurred when the entity is already on one |
|
* of the service trees for its previous class, then the state of the |
|
* entity would become more complex: none of the new possible service |
|
* trees for the entity, according to bfq_entity_service_tree(), would |
|
* match any of the possible service trees on which the entity |
|
* is. Complex operations involving these trees, such as entity |
|
* activations and deactivations, should take into account this |
|
* additional complexity. To avoid this issue, this function is |
|
* invoked with update_class_too unset in the points in the code where |
|
* entity may happen to be on some tree. |
|
*/ |
|
struct bfq_service_tree * |
|
__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st, |
|
struct bfq_entity *entity, |
|
bool update_class_too) |
|
{ |
|
struct bfq_service_tree *new_st = old_st; |
|
|
|
if (entity->prio_changed) { |
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
unsigned int prev_weight, new_weight; |
|
struct bfq_data *bfqd = NULL; |
|
struct rb_root_cached *root; |
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
struct bfq_sched_data *sd; |
|
struct bfq_group *bfqg; |
|
#endif |
|
|
|
if (bfqq) |
|
bfqd = bfqq->bfqd; |
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
else { |
|
sd = entity->my_sched_data; |
|
bfqg = container_of(sd, struct bfq_group, sched_data); |
|
bfqd = (struct bfq_data *)bfqg->bfqd; |
|
} |
|
#endif |
|
|
|
/* Matches the smp_wmb() in bfq_group_set_weight. */ |
|
smp_rmb(); |
|
old_st->wsum -= entity->weight; |
|
|
|
if (entity->new_weight != entity->orig_weight) { |
|
if (entity->new_weight < BFQ_MIN_WEIGHT || |
|
entity->new_weight > BFQ_MAX_WEIGHT) { |
|
pr_crit("update_weight_prio: new_weight %d\n", |
|
entity->new_weight); |
|
if (entity->new_weight < BFQ_MIN_WEIGHT) |
|
entity->new_weight = BFQ_MIN_WEIGHT; |
|
else |
|
entity->new_weight = BFQ_MAX_WEIGHT; |
|
} |
|
entity->orig_weight = entity->new_weight; |
|
if (bfqq) |
|
bfqq->ioprio = |
|
bfq_weight_to_ioprio(entity->orig_weight); |
|
} |
|
|
|
if (bfqq && update_class_too) |
|
bfqq->ioprio_class = bfqq->new_ioprio_class; |
|
|
|
/* |
|
* Reset prio_changed only if the ioprio_class change |
|
* is not pending any longer. |
|
*/ |
|
if (!bfqq || bfqq->ioprio_class == bfqq->new_ioprio_class) |
|
entity->prio_changed = 0; |
|
|
|
/* |
|
* NOTE: here we may be changing the weight too early, |
|
* this will cause unfairness. The correct approach |
|
* would have required additional complexity to defer |
|
* weight changes to the proper time instants (i.e., |
|
* when entity->finish <= old_st->vtime). |
|
*/ |
|
new_st = bfq_entity_service_tree(entity); |
|
|
|
prev_weight = entity->weight; |
|
new_weight = entity->orig_weight * |
|
(bfqq ? bfqq->wr_coeff : 1); |
|
/* |
|
* If the weight of the entity changes, and the entity is a |
|
* queue, remove the entity from its old weight counter (if |
|
* there is a counter associated with the entity). |
|
*/ |
|
if (prev_weight != new_weight && bfqq) { |
|
root = &bfqd->queue_weights_tree; |
|
__bfq_weights_tree_remove(bfqd, bfqq, root); |
|
} |
|
entity->weight = new_weight; |
|
/* |
|
* Add the entity, if it is not a weight-raised queue, |
|
* to the counter associated with its new weight. |
|
*/ |
|
if (prev_weight != new_weight && bfqq && bfqq->wr_coeff == 1) { |
|
/* If we get here, root has been initialized. */ |
|
bfq_weights_tree_add(bfqd, bfqq, root); |
|
} |
|
|
|
new_st->wsum += entity->weight; |
|
|
|
if (new_st != old_st) |
|
entity->start = new_st->vtime; |
|
} |
|
|
|
return new_st; |
|
} |
|
|
|
/** |
|
* bfq_bfqq_served - update the scheduler status after selection for |
|
* service. |
|
* @bfqq: the queue being served. |
|
* @served: bytes to transfer. |
|
* |
|
* NOTE: this can be optimized, as the timestamps of upper level entities |
|
* are synchronized every time a new bfqq is selected for service. By now, |
|
* we keep it to better check consistency. |
|
*/ |
|
void bfq_bfqq_served(struct bfq_queue *bfqq, int served) |
|
{ |
|
struct bfq_entity *entity = &bfqq->entity; |
|
struct bfq_service_tree *st; |
|
|
|
if (!bfqq->service_from_backlogged) |
|
bfqq->first_IO_time = jiffies; |
|
|
|
if (bfqq->wr_coeff > 1) |
|
bfqq->service_from_wr += served; |
|
|
|
bfqq->service_from_backlogged += served; |
|
for_each_entity(entity) { |
|
st = bfq_entity_service_tree(entity); |
|
|
|
entity->service += served; |
|
|
|
st->vtime += bfq_delta(served, st->wsum); |
|
bfq_forget_idle(st); |
|
} |
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served); |
|
} |
|
|
|
/** |
|
* bfq_bfqq_charge_time - charge an amount of service equivalent to the length |
|
* of the time interval during which bfqq has been in |
|
* service. |
|
* @bfqd: the device |
|
* @bfqq: the queue that needs a service update. |
|
* @time_ms: the amount of time during which the queue has received service |
|
* |
|
* If a queue does not consume its budget fast enough, then providing |
|
* the queue with service fairness may impair throughput, more or less |
|
* severely. For this reason, queues that consume their budget slowly |
|
* are provided with time fairness instead of service fairness. This |
|
* goal is achieved through the BFQ scheduling engine, even if such an |
|
* engine works in the service, and not in the time domain. The trick |
|
* is charging these queues with an inflated amount of service, equal |
|
* to the amount of service that they would have received during their |
|
* service slot if they had been fast, i.e., if their requests had |
|
* been dispatched at a rate equal to the estimated peak rate. |
|
* |
|
* It is worth noting that time fairness can cause important |
|
* distortions in terms of bandwidth distribution, on devices with |
|
* internal queueing. The reason is that I/O requests dispatched |
|
* during the service slot of a queue may be served after that service |
|
* slot is finished, and may have a total processing time loosely |
|
* correlated with the duration of the service slot. This is |
|
* especially true for short service slots. |
|
*/ |
|
void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq, |
|
unsigned long time_ms) |
|
{ |
|
struct bfq_entity *entity = &bfqq->entity; |
|
unsigned long timeout_ms = jiffies_to_msecs(bfq_timeout); |
|
unsigned long bounded_time_ms = min(time_ms, timeout_ms); |
|
int serv_to_charge_for_time = |
|
(bfqd->bfq_max_budget * bounded_time_ms) / timeout_ms; |
|
int tot_serv_to_charge = max(serv_to_charge_for_time, entity->service); |
|
|
|
/* Increase budget to avoid inconsistencies */ |
|
if (tot_serv_to_charge > entity->budget) |
|
entity->budget = tot_serv_to_charge; |
|
|
|
bfq_bfqq_served(bfqq, |
|
max_t(int, 0, tot_serv_to_charge - entity->service)); |
|
} |
|
|
|
static void bfq_update_fin_time_enqueue(struct bfq_entity *entity, |
|
struct bfq_service_tree *st, |
|
bool backshifted) |
|
{ |
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
|
|
|
/* |
|
* When this function is invoked, entity is not in any service |
|
* tree, then it is safe to invoke next function with the last |
|
* parameter set (see the comments on the function). |
|
*/ |
|
st = __bfq_entity_update_weight_prio(st, entity, true); |
|
bfq_calc_finish(entity, entity->budget); |
|
|
|
/* |
|
* If some queues enjoy backshifting for a while, then their |
|
* (virtual) finish timestamps may happen to become lower and |
|
* lower than the system virtual time. In particular, if |
|
* these queues often happen to be idle for short time |
|
* periods, and during such time periods other queues with |
|
* higher timestamps happen to be busy, then the backshifted |
|
* timestamps of the former queues can become much lower than |
|
* the system virtual time. In fact, to serve the queues with |
|
* higher timestamps while the ones with lower timestamps are |
|
* idle, the system virtual time may be pushed-up to much |
|
* higher values than the finish timestamps of the idle |
|
* queues. As a consequence, the finish timestamps of all new |
|
* or newly activated queues may end up being much larger than |
|
* those of lucky queues with backshifted timestamps. The |
|
* latter queues may then monopolize the device for a lot of |
|
* time. This would simply break service guarantees. |
|
* |
|
* To reduce this problem, push up a little bit the |
|
* backshifted timestamps of the queue associated with this |
|
* entity (only a queue can happen to have the backshifted |
|
* flag set): just enough to let the finish timestamp of the |
|
* queue be equal to the current value of the system virtual |
|
* time. This may introduce a little unfairness among queues |
|
* with backshifted timestamps, but it does not break |
|
* worst-case fairness guarantees. |
|
* |
|
* As a special case, if bfqq is weight-raised, push up |
|
* timestamps much less, to keep very low the probability that |
|
* this push up causes the backshifted finish timestamps of |
|
* weight-raised queues to become higher than the backshifted |
|
* finish timestamps of non weight-raised queues. |
|
*/ |
|
if (backshifted && bfq_gt(st->vtime, entity->finish)) { |
|
unsigned long delta = st->vtime - entity->finish; |
|
|
|
if (bfqq) |
|
delta /= bfqq->wr_coeff; |
|
|
|
entity->start += delta; |
|
entity->finish += delta; |
|
} |
|
|
|
bfq_active_insert(st, entity); |
|
} |
|
|
|
/** |
|
* __bfq_activate_entity - handle activation of entity. |
|
* @entity: the entity being activated. |
|
* @non_blocking_wait_rq: true if entity was waiting for a request |
|
* |
|
* Called for a 'true' activation, i.e., if entity is not active and |
|
* one of its children receives a new request. |
|
* |
|
* Basically, this function updates the timestamps of entity and |
|
* inserts entity into its active tree, after possibly extracting it |
|
* from its idle tree. |
|
*/ |
|
static void __bfq_activate_entity(struct bfq_entity *entity, |
|
bool non_blocking_wait_rq) |
|
{ |
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity); |
|
bool backshifted = false; |
|
unsigned long long min_vstart; |
|
|
|
/* See comments on bfq_fqq_update_budg_for_activation */ |
|
if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) { |
|
backshifted = true; |
|
min_vstart = entity->finish; |
|
} else |
|
min_vstart = st->vtime; |
|
|
|
if (entity->tree == &st->idle) { |
|
/* |
|
* Must be on the idle tree, bfq_idle_extract() will |
|
* check for that. |
|
*/ |
|
bfq_idle_extract(st, entity); |
|
entity->start = bfq_gt(min_vstart, entity->finish) ? |
|
min_vstart : entity->finish; |
|
} else { |
|
/* |
|
* The finish time of the entity may be invalid, and |
|
* it is in the past for sure, otherwise the queue |
|
* would have been on the idle tree. |
|
*/ |
|
entity->start = min_vstart; |
|
st->wsum += entity->weight; |
|
/* |
|
* entity is about to be inserted into a service tree, |
|
* and then set in service: get a reference to make |
|
* sure entity does not disappear until it is no |
|
* longer in service or scheduled for service. |
|
*/ |
|
bfq_get_entity(entity); |
|
|
|
entity->on_st_or_in_serv = true; |
|
} |
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED |
|
if (!bfq_entity_to_bfqq(entity)) { /* bfq_group */ |
|
struct bfq_group *bfqg = |
|
container_of(entity, struct bfq_group, entity); |
|
struct bfq_data *bfqd = bfqg->bfqd; |
|
|
|
if (!entity->in_groups_with_pending_reqs) { |
|
entity->in_groups_with_pending_reqs = true; |
|
bfqd->num_groups_with_pending_reqs++; |
|
} |
|
} |
|
#endif |
|
|
|
bfq_update_fin_time_enqueue(entity, st, backshifted); |
|
} |
|
|
|
/** |
|
* __bfq_requeue_entity - handle requeueing or repositioning of an entity. |
|
* @entity: the entity being requeued or repositioned. |
|
* |
|
* Requeueing is needed if this entity stops being served, which |
|
* happens if a leaf descendant entity has expired. On the other hand, |
|
* repositioning is needed if the next_inservice_entity for the child |
|
* entity has changed. See the comments inside the function for |
|
* details. |
|
* |
|
* Basically, this function: 1) removes entity from its active tree if |
|
* present there, 2) updates the timestamps of entity and 3) inserts |
|
* entity back into its active tree (in the new, right position for |
|
* the new values of the timestamps). |
|
*/ |
|
static void __bfq_requeue_entity(struct bfq_entity *entity) |
|
{ |
|
struct bfq_sched_data *sd = entity->sched_data; |
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity); |
|
|
|
if (entity == sd->in_service_entity) { |
|
/* |
|
* We are requeueing the current in-service entity, |
|
* which may have to be done for one of the following |
|
* reasons: |
|
* - entity represents the in-service queue, and the |
|
* in-service queue is being requeued after an |
|
* expiration; |
|
* - entity represents a group, and its budget has |
|
* changed because one of its child entities has |
|
* just been either activated or requeued for some |
|
* reason; the timestamps of the entity need then to |
|
* be updated, and the entity needs to be enqueued |
|
* or repositioned accordingly. |
|
* |
|
* In particular, before requeueing, the start time of |
|
* the entity must be moved forward to account for the |
|
* service that the entity has received while in |
|
* service. This is done by the next instructions. The |
|
* finish time will then be updated according to this |
|
* new value of the start time, and to the budget of |
|
* the entity. |
|
*/ |
|
bfq_calc_finish(entity, entity->service); |
|
entity->start = entity->finish; |
|
/* |
|
* In addition, if the entity had more than one child |
|
* when set in service, then it was not extracted from |
|
* the active tree. This implies that the position of |
|
* the entity in the active tree may need to be |
|
* changed now, because we have just updated the start |
|
* time of the entity, and we will update its finish |
|
* time in a moment (the requeueing is then, more |
|
* precisely, a repositioning in this case). To |
|
* implement this repositioning, we: 1) dequeue the |
|
* entity here, 2) update the finish time and requeue |
|
* the entity according to the new timestamps below. |
|
*/ |
|
if (entity->tree) |
|
bfq_active_extract(st, entity); |
|
} else { /* The entity is already active, and not in service */ |
|
/* |
|
* In this case, this function gets called only if the |
|
* next_in_service entity below this entity has |
|
* changed, and this change has caused the budget of |
|
* this entity to change, which, finally implies that |
|
* the finish time of this entity must be |
|
* updated. Such an update may cause the scheduling, |
|
* i.e., the position in the active tree, of this |
|
* entity to change. We handle this change by: 1) |
|
* dequeueing the entity here, 2) updating the finish |
|
* time and requeueing the entity according to the new |
|
* timestamps below. This is the same approach as the |
|
* non-extracted-entity sub-case above. |
|
*/ |
|
bfq_active_extract(st, entity); |
|
} |
|
|
|
bfq_update_fin_time_enqueue(entity, st, false); |
|
} |
|
|
|
static void __bfq_activate_requeue_entity(struct bfq_entity *entity, |
|
struct bfq_sched_data *sd, |
|
bool non_blocking_wait_rq) |
|
{ |
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity); |
|
|
|
if (sd->in_service_entity == entity || entity->tree == &st->active) |
|
/* |
|
* in service or already queued on the active tree, |
|
* requeue or reposition |
|
*/ |
|
__bfq_requeue_entity(entity); |
|
else |
|
/* |
|
* Not in service and not queued on its active tree: |
|
* the activity is idle and this is a true activation. |
|
*/ |
|
__bfq_activate_entity(entity, non_blocking_wait_rq); |
|
} |
|
|
|
|
|
/** |
|
* bfq_activate_requeue_entity - activate or requeue an entity representing a |
|
* bfq_queue, and activate, requeue or reposition |
|
* all ancestors for which such an update becomes |
|
* necessary. |
|
* @entity: the entity to activate. |
|
* @non_blocking_wait_rq: true if this entity was waiting for a request |
|
* @requeue: true if this is a requeue, which implies that bfqq is |
|
* being expired; thus ALL its ancestors stop being served and must |
|
* therefore be requeued |
|
* @expiration: true if this function is being invoked in the expiration path |
|
* of the in-service queue |
|
*/ |
|
static void bfq_activate_requeue_entity(struct bfq_entity *entity, |
|
bool non_blocking_wait_rq, |
|
bool requeue, bool expiration) |
|
{ |
|
struct bfq_sched_data *sd; |
|
|
|
for_each_entity(entity) { |
|
sd = entity->sched_data; |
|
__bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq); |
|
|
|
if (!bfq_update_next_in_service(sd, entity, expiration) && |
|
!requeue) |
|
break; |
|
} |
|
} |
|
|
|
/** |
|
* __bfq_deactivate_entity - update sched_data and service trees for |
|
* entity, so as to represent entity as inactive |
|
* @entity: the entity being deactivated. |
|
* @ins_into_idle_tree: if false, the entity will not be put into the |
|
* idle tree. |
|
* |
|
* If necessary and allowed, puts entity into the idle tree. NOTE: |
|
* entity may be on no tree if in service. |
|
*/ |
|
bool __bfq_deactivate_entity(struct bfq_entity *entity, bool ins_into_idle_tree) |
|
{ |
|
struct bfq_sched_data *sd = entity->sched_data; |
|
struct bfq_service_tree *st; |
|
bool is_in_service; |
|
|
|
if (!entity->on_st_or_in_serv) /* |
|
* entity never activated, or |
|
* already inactive |
|
*/ |
|
return false; |
|
|
|
/* |
|
* If we get here, then entity is active, which implies that |
|
* bfq_group_set_parent has already been invoked for the group |
|
* represented by entity. Therefore, the field |
|
* entity->sched_data has been set, and we can safely use it. |
|
*/ |
|
st = bfq_entity_service_tree(entity); |
|
is_in_service = entity == sd->in_service_entity; |
|
|
|
bfq_calc_finish(entity, entity->service); |
|
|
|
if (is_in_service) |
|
sd->in_service_entity = NULL; |
|
else |
|
/* |
|
* Non in-service entity: nobody will take care of |
|
* resetting its service counter on expiration. Do it |
|
* now. |
|
*/ |
|
entity->service = 0; |
|
|
|
if (entity->tree == &st->active) |
|
bfq_active_extract(st, entity); |
|
else if (!is_in_service && entity->tree == &st->idle) |
|
bfq_idle_extract(st, entity); |
|
|
|
if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime)) |
|
bfq_forget_entity(st, entity, is_in_service); |
|
else |
|
bfq_idle_insert(st, entity); |
|
|
|
return true; |
|
} |
|
|
|
/** |
|
* bfq_deactivate_entity - deactivate an entity representing a bfq_queue. |
|
* @entity: the entity to deactivate. |
|
* @ins_into_idle_tree: true if the entity can be put into the idle tree |
|
* @expiration: true if this function is being invoked in the expiration path |
|
* of the in-service queue |
|
*/ |
|
static void bfq_deactivate_entity(struct bfq_entity *entity, |
|
bool ins_into_idle_tree, |
|
bool expiration) |
|
{ |
|
struct bfq_sched_data *sd; |
|
struct bfq_entity *parent = NULL; |
|
|
|
for_each_entity_safe(entity, parent) { |
|
sd = entity->sched_data; |
|
|
|
if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) { |
|
/* |
|
* entity is not in any tree any more, so |
|
* this deactivation is a no-op, and there is |
|
* nothing to change for upper-level entities |
|
* (in case of expiration, this can never |
|
* happen). |
|
*/ |
|
return; |
|
} |
|
|
|
if (sd->next_in_service == entity) |
|
/* |
|
* entity was the next_in_service entity, |
|
* then, since entity has just been |
|
* deactivated, a new one must be found. |
|
*/ |
|
bfq_update_next_in_service(sd, NULL, expiration); |
|
|
|
if (sd->next_in_service || sd->in_service_entity) { |
|
/* |
|
* The parent entity is still active, because |
|
* either next_in_service or in_service_entity |
|
* is not NULL. So, no further upwards |
|
* deactivation must be performed. Yet, |
|
* next_in_service has changed. Then the |
|
* schedule does need to be updated upwards. |
|
* |
|
* NOTE If in_service_entity is not NULL, then |
|
* next_in_service may happen to be NULL, |
|
* although the parent entity is evidently |
|
* active. This happens if 1) the entity |
|
* pointed by in_service_entity is the only |
|
* active entity in the parent entity, and 2) |
|
* according to the definition of |
|
* next_in_service, the in_service_entity |
|
* cannot be considered as |
|
* next_in_service. See the comments on the |
|
* definition of next_in_service for details. |
|
*/ |
|
break; |
|
} |
|
|
|
/* |
|
* If we get here, then the parent is no more |
|
* backlogged and we need to propagate the |
|
* deactivation upwards. Thus let the loop go on. |
|
*/ |
|
|
|
/* |
|
* Also let parent be queued into the idle tree on |
|
* deactivation, to preserve service guarantees, and |
|
* assuming that who invoked this function does not |
|
* need parent entities too to be removed completely. |
|
*/ |
|
ins_into_idle_tree = true; |
|
} |
|
|
|
/* |
|
* If the deactivation loop is fully executed, then there are |
|
* no more entities to touch and next loop is not executed at |
|
* all. Otherwise, requeue remaining entities if they are |
|
* about to stop receiving service, or reposition them if this |
|
* is not the case. |
|
*/ |
|
entity = parent; |
|
for_each_entity(entity) { |
|
/* |
|
* Invoke __bfq_requeue_entity on entity, even if |
|
* already active, to requeue/reposition it in the |
|
* active tree (because sd->next_in_service has |
|
* changed) |
|
*/ |
|
__bfq_requeue_entity(entity); |
|
|
|
sd = entity->sched_data; |
|
if (!bfq_update_next_in_service(sd, entity, expiration) && |
|
!expiration) |
|
/* |
|
* next_in_service unchanged or not causing |
|
* any change in entity->parent->sd, and no |
|
* requeueing needed for expiration: stop |
|
* here. |
|
*/ |
|
break; |
|
} |
|
} |
|
|
|
/** |
|
* bfq_calc_vtime_jump - compute the value to which the vtime should jump, |
|
* if needed, to have at least one entity eligible. |
|
* @st: the service tree to act upon. |
|
* |
|
* Assumes that st is not empty. |
|
*/ |
|
static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st) |
|
{ |
|
struct bfq_entity *root_entity = bfq_root_active_entity(&st->active); |
|
|
|
if (bfq_gt(root_entity->min_start, st->vtime)) |
|
return root_entity->min_start; |
|
|
|
return st->vtime; |
|
} |
|
|
|
static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value) |
|
{ |
|
if (new_value > st->vtime) { |
|
st->vtime = new_value; |
|
bfq_forget_idle(st); |
|
} |
|
} |
|
|
|
/** |
|
* bfq_first_active_entity - find the eligible entity with |
|
* the smallest finish time |
|
* @st: the service tree to select from. |
|
* @vtime: the system virtual to use as a reference for eligibility |
|
* |
|
* This function searches the first schedulable entity, starting from the |
|
* root of the tree and going on the left every time on this side there is |
|
* a subtree with at least one eligible (start <= vtime) entity. The path on |
|
* the right is followed only if a) the left subtree contains no eligible |
|
* entities and b) no eligible entity has been found yet. |
|
*/ |
|
static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st, |
|
u64 vtime) |
|
{ |
|
struct bfq_entity *entry, *first = NULL; |
|
struct rb_node *node = st->active.rb_node; |
|
|
|
while (node) { |
|
entry = rb_entry(node, struct bfq_entity, rb_node); |
|
left: |
|
if (!bfq_gt(entry->start, vtime)) |
|
first = entry; |
|
|
|
if (node->rb_left) { |
|
entry = rb_entry(node->rb_left, |
|
struct bfq_entity, rb_node); |
|
if (!bfq_gt(entry->min_start, vtime)) { |
|
node = node->rb_left; |
|
goto left; |
|
} |
|
} |
|
if (first) |
|
break; |
|
node = node->rb_right; |
|
} |
|
|
|
return first; |
|
} |
|
|
|
/** |
|
* __bfq_lookup_next_entity - return the first eligible entity in @st. |
|
* @st: the service tree. |
|
* |
|
* If there is no in-service entity for the sched_data st belongs to, |
|
* then return the entity that will be set in service if: |
|
* 1) the parent entity this st belongs to is set in service; |
|
* 2) no entity belonging to such parent entity undergoes a state change |
|
* that would influence the timestamps of the entity (e.g., becomes idle, |
|
* becomes backlogged, changes its budget, ...). |
|
* |
|
* In this first case, update the virtual time in @st too (see the |
|
* comments on this update inside the function). |
|
* |
|
* In contrast, if there is an in-service entity, then return the |
|
* entity that would be set in service if not only the above |
|
* conditions, but also the next one held true: the currently |
|
* in-service entity, on expiration, |
|
* 1) gets a finish time equal to the current one, or |
|
* 2) is not eligible any more, or |
|
* 3) is idle. |
|
*/ |
|
static struct bfq_entity * |
|
__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service) |
|
{ |
|
struct bfq_entity *entity; |
|
u64 new_vtime; |
|
|
|
if (RB_EMPTY_ROOT(&st->active)) |
|
return NULL; |
|
|
|
/* |
|
* Get the value of the system virtual time for which at |
|
* least one entity is eligible. |
|
*/ |
|
new_vtime = bfq_calc_vtime_jump(st); |
|
|
|
/* |
|
* If there is no in-service entity for the sched_data this |
|
* active tree belongs to, then push the system virtual time |
|
* up to the value that guarantees that at least one entity is |
|
* eligible. If, instead, there is an in-service entity, then |
|
* do not make any such update, because there is already an |
|
* eligible entity, namely the in-service one (even if the |
|
* entity is not on st, because it was extracted when set in |
|
* service). |
|
*/ |
|
if (!in_service) |
|
bfq_update_vtime(st, new_vtime); |
|
|
|
entity = bfq_first_active_entity(st, new_vtime); |
|
|
|
return entity; |
|
} |
|
|
|
/** |
|
* bfq_lookup_next_entity - return the first eligible entity in @sd. |
|
* @sd: the sched_data. |
|
* @expiration: true if we are on the expiration path of the in-service queue |
|
* |
|
* This function is invoked when there has been a change in the trees |
|
* for sd, and we need to know what is the new next entity to serve |
|
* after this change. |
|
*/ |
|
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, |
|
bool expiration) |
|
{ |
|
struct bfq_service_tree *st = sd->service_tree; |
|
struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1); |
|
struct bfq_entity *entity = NULL; |
|
int class_idx = 0; |
|
|
|
/* |
|
* Choose from idle class, if needed to guarantee a minimum |
|
* bandwidth to this class (and if there is some active entity |
|
* in idle class). This should also mitigate |
|
* priority-inversion problems in case a low priority task is |
|
* holding file system resources. |
|
*/ |
|
if (time_is_before_jiffies(sd->bfq_class_idle_last_service + |
|
BFQ_CL_IDLE_TIMEOUT)) { |
|
if (!RB_EMPTY_ROOT(&idle_class_st->active)) |
|
class_idx = BFQ_IOPRIO_CLASSES - 1; |
|
/* About to be served if backlogged, or not yet backlogged */ |
|
sd->bfq_class_idle_last_service = jiffies; |
|
} |
|
|
|
/* |
|
* Find the next entity to serve for the highest-priority |
|
* class, unless the idle class needs to be served. |
|
*/ |
|
for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) { |
|
/* |
|
* If expiration is true, then bfq_lookup_next_entity |
|
* is being invoked as a part of the expiration path |
|
* of the in-service queue. In this case, even if |
|
* sd->in_service_entity is not NULL, |
|
* sd->in_service_entity at this point is actually not |
|
* in service any more, and, if needed, has already |
|
* been properly queued or requeued into the right |
|
* tree. The reason why sd->in_service_entity is still |
|
* not NULL here, even if expiration is true, is that |
|
* sd->in_service_entity is reset as a last step in the |
|
* expiration path. So, if expiration is true, tell |
|
* __bfq_lookup_next_entity that there is no |
|
* sd->in_service_entity. |
|
*/ |
|
entity = __bfq_lookup_next_entity(st + class_idx, |
|
sd->in_service_entity && |
|
!expiration); |
|
|
|
if (entity) |
|
break; |
|
} |
|
|
|
if (!entity) |
|
return NULL; |
|
|
|
return entity; |
|
} |
|
|
|
bool next_queue_may_preempt(struct bfq_data *bfqd) |
|
{ |
|
struct bfq_sched_data *sd = &bfqd->root_group->sched_data; |
|
|
|
return sd->next_in_service != sd->in_service_entity; |
|
} |
|
|
|
/* |
|
* Get next queue for service. |
|
*/ |
|
struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd) |
|
{ |
|
struct bfq_entity *entity = NULL; |
|
struct bfq_sched_data *sd; |
|
struct bfq_queue *bfqq; |
|
|
|
if (bfq_tot_busy_queues(bfqd) == 0) |
|
return NULL; |
|
|
|
/* |
|
* Traverse the path from the root to the leaf entity to |
|
* serve. Set in service all the entities visited along the |
|
* way. |
|
*/ |
|
sd = &bfqd->root_group->sched_data; |
|
for (; sd ; sd = entity->my_sched_data) { |
|
/* |
|
* WARNING. We are about to set the in-service entity |
|
* to sd->next_in_service, i.e., to the (cached) value |
|
* returned by bfq_lookup_next_entity(sd) the last |
|
* time it was invoked, i.e., the last time when the |
|
* service order in sd changed as a consequence of the |
|
* activation or deactivation of an entity. In this |
|
* respect, if we execute bfq_lookup_next_entity(sd) |
|
* in this very moment, it may, although with low |
|
* probability, yield a different entity than that |
|
* pointed to by sd->next_in_service. This rare event |
|
* happens in case there was no CLASS_IDLE entity to |
|
* serve for sd when bfq_lookup_next_entity(sd) was |
|
* invoked for the last time, while there is now one |
|
* such entity. |
|
* |
|
* If the above event happens, then the scheduling of |
|
* such entity in CLASS_IDLE is postponed until the |
|
* service of the sd->next_in_service entity |
|
* finishes. In fact, when the latter is expired, |
|
* bfq_lookup_next_entity(sd) gets called again, |
|
* exactly to update sd->next_in_service. |
|
*/ |
|
|
|
/* Make next_in_service entity become in_service_entity */ |
|
entity = sd->next_in_service; |
|
sd->in_service_entity = entity; |
|
|
|
/* |
|
* If entity is no longer a candidate for next |
|
* service, then it must be extracted from its active |
|
* tree, so as to make sure that it won't be |
|
* considered when computing next_in_service. See the |
|
* comments on the function |
|
* bfq_no_longer_next_in_service() for details. |
|
*/ |
|
if (bfq_no_longer_next_in_service(entity)) |
|
bfq_active_extract(bfq_entity_service_tree(entity), |
|
entity); |
|
|
|
/* |
|
* Even if entity is not to be extracted according to |
|
* the above check, a descendant entity may get |
|
* extracted in one of the next iterations of this |
|
* loop. Such an event could cause a change in |
|
* next_in_service for the level of the descendant |
|
* entity, and thus possibly back to this level. |
|
* |
|
* However, we cannot perform the resulting needed |
|
* update of next_in_service for this level before the |
|
* end of the whole loop, because, to know which is |
|
* the correct next-to-serve candidate entity for each |
|
* level, we need first to find the leaf entity to set |
|
* in service. In fact, only after we know which is |
|
* the next-to-serve leaf entity, we can discover |
|
* whether the parent entity of the leaf entity |
|
* becomes the next-to-serve, and so on. |
|
*/ |
|
} |
|
|
|
bfqq = bfq_entity_to_bfqq(entity); |
|
|
|
/* |
|
* We can finally update all next-to-serve entities along the |
|
* path from the leaf entity just set in service to the root. |
|
*/ |
|
for_each_entity(entity) { |
|
struct bfq_sched_data *sd = entity->sched_data; |
|
|
|
if (!bfq_update_next_in_service(sd, NULL, false)) |
|
break; |
|
} |
|
|
|
return bfqq; |
|
} |
|
|
|
/* returns true if the in-service queue gets freed */ |
|
bool __bfq_bfqd_reset_in_service(struct bfq_data *bfqd) |
|
{ |
|
struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue; |
|
struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity; |
|
struct bfq_entity *entity = in_serv_entity; |
|
|
|
bfq_clear_bfqq_wait_request(in_serv_bfqq); |
|
hrtimer_try_to_cancel(&bfqd->idle_slice_timer); |
|
bfqd->in_service_queue = NULL; |
|
|
|
/* |
|
* When this function is called, all in-service entities have |
|
* been properly deactivated or requeued, so we can safely |
|
* execute the final step: reset in_service_entity along the |
|
* path from entity to the root. |
|
*/ |
|
for_each_entity(entity) |
|
entity->sched_data->in_service_entity = NULL; |
|
|
|
/* |
|
* in_serv_entity is no longer in service, so, if it is in no |
|
* service tree either, then release the service reference to |
|
* the queue it represents (taken with bfq_get_entity). |
|
*/ |
|
if (!in_serv_entity->on_st_or_in_serv) { |
|
/* |
|
* If no process is referencing in_serv_bfqq any |
|
* longer, then the service reference may be the only |
|
* reference to the queue. If this is the case, then |
|
* bfqq gets freed here. |
|
*/ |
|
int ref = in_serv_bfqq->ref; |
|
bfq_put_queue(in_serv_bfqq); |
|
if (ref == 1) |
|
return true; |
|
} |
|
|
|
return false; |
|
} |
|
|
|
void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, |
|
bool ins_into_idle_tree, bool expiration) |
|
{ |
|
struct bfq_entity *entity = &bfqq->entity; |
|
|
|
bfq_deactivate_entity(entity, ins_into_idle_tree, expiration); |
|
} |
|
|
|
void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq) |
|
{ |
|
struct bfq_entity *entity = &bfqq->entity; |
|
|
|
bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq), |
|
false, false); |
|
bfq_clear_bfqq_non_blocking_wait_rq(bfqq); |
|
} |
|
|
|
void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq, |
|
bool expiration) |
|
{ |
|
struct bfq_entity *entity = &bfqq->entity; |
|
|
|
bfq_activate_requeue_entity(entity, false, |
|
bfqq == bfqd->in_service_queue, expiration); |
|
} |
|
|
|
/* |
|
* Called when the bfqq no longer has requests pending, remove it from |
|
* the service tree. As a special case, it can be invoked during an |
|
* expiration. |
|
*/ |
|
void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq, |
|
bool expiration) |
|
{ |
|
bfq_log_bfqq(bfqd, bfqq, "del from busy"); |
|
|
|
bfq_clear_bfqq_busy(bfqq); |
|
|
|
bfqd->busy_queues[bfqq->ioprio_class - 1]--; |
|
|
|
if (bfqq->wr_coeff > 1) |
|
bfqd->wr_busy_queues--; |
|
|
|
bfqg_stats_update_dequeue(bfqq_group(bfqq)); |
|
|
|
bfq_deactivate_bfqq(bfqd, bfqq, true, expiration); |
|
|
|
if (!bfqq->dispatched) |
|
bfq_weights_tree_remove(bfqd, bfqq); |
|
} |
|
|
|
/* |
|
* Called when an inactive queue receives a new request. |
|
*/ |
|
void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq) |
|
{ |
|
bfq_log_bfqq(bfqd, bfqq, "add to busy"); |
|
|
|
bfq_activate_bfqq(bfqd, bfqq); |
|
|
|
bfq_mark_bfqq_busy(bfqq); |
|
bfqd->busy_queues[bfqq->ioprio_class - 1]++; |
|
|
|
if (!bfqq->dispatched) |
|
if (bfqq->wr_coeff == 1) |
|
bfq_weights_tree_add(bfqd, bfqq, |
|
&bfqd->queue_weights_tree); |
|
|
|
if (bfqq->wr_coeff > 1) |
|
bfqd->wr_busy_queues++; |
|
|
|
/* Move bfqq to the head of the woken list of its waker */ |
|
if (!hlist_unhashed(&bfqq->woken_list_node) && |
|
&bfqq->woken_list_node != bfqq->waker_bfqq->woken_list.first) { |
|
hlist_del_init(&bfqq->woken_list_node); |
|
hlist_add_head(&bfqq->woken_list_node, |
|
&bfqq->waker_bfqq->woken_list); |
|
} |
|
}
|
|
|