| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * Hierarchical Budget Worst-case Fair Weighted Fair Queueing |
| * (B-WF2Q+): hierarchical scheduling algorithm by which the BFQ I/O |
| * scheduler schedules generic entities. The latter can represent |
| * either single bfq queues (associated with processes) or groups of |
| * bfq queues (associated with cgroups). |
| */ |
| #include "bfq-iosched.h" |
| |
| /** |
| * bfq_gt - compare two timestamps. |
| * @a: first ts. |
| * @b: second ts. |
| * |
| * Return @a > @b, dealing with wrapping correctly. |
| */ |
| static int bfq_gt(u64 a, u64 b) |
| { |
| return (s64)(a - b) > 0; |
| } |
| |
| static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree) |
| { |
| struct rb_node *node = tree->rb_node; |
| |
| return rb_entry(node, struct bfq_entity, rb_node); |
| } |
| |
| static unsigned int bfq_class_idx(struct bfq_entity *entity) |
| { |
| struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
| |
| return bfqq ? bfqq->ioprio_class - 1 : |
| BFQ_DEFAULT_GRP_CLASS - 1; |
| } |
| |
| unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd) |
| { |
| return bfqd->busy_queues[0] + bfqd->busy_queues[1] + |
| bfqd->busy_queues[2]; |
| } |
| |
| static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd, |
| bool expiration); |
| |
| static bool bfq_update_parent_budget(struct bfq_entity *next_in_service); |
| |
| /** |
| * bfq_update_next_in_service - update sd->next_in_service |
| * @sd: sched_data for which to perform the update. |
| * @new_entity: if not NULL, pointer to the entity whose activation, |
| * requeueing or repositioning triggered the invocation of |
| * this function. |
| * @expiration: id true, this function is being invoked after the |
| * expiration of the in-service entity |
| * |
| * This function is called to update sd->next_in_service, which, in |
| * its turn, may change as a consequence of the insertion or |
| * extraction of an entity into/from one of the active trees of |
| * sd. These insertions/extractions occur as a consequence of |
| * activations/deactivations of entities, with some activations being |
| * 'true' activations, and other activations being requeueings (i.e., |
| * implementing the second, requeueing phase of the mechanism used to |
| * reposition an entity in its active tree; see comments on |
| * __bfq_activate_entity and __bfq_requeue_entity for details). In |
| * both the last two activation sub-cases, new_entity points to the |
| * just activated or requeued entity. |
| * |
| * Returns true if sd->next_in_service changes in such a way that |
| * entity->parent may become the next_in_service for its parent |
| * entity. |
| */ |
| static bool bfq_update_next_in_service(struct bfq_sched_data *sd, |
| struct bfq_entity *new_entity, |
| bool expiration) |
| { |
| struct bfq_entity *next_in_service = sd->next_in_service; |
| bool parent_sched_may_change = false; |
| bool change_without_lookup = false; |
| |
| /* |
| * If this update is triggered by the activation, requeueing |
| * or repositioning of an entity that does not coincide with |
| * sd->next_in_service, then a full lookup in the active tree |
| * can be avoided. In fact, it is enough to check whether the |
| * just-modified entity has the same priority as |
| * sd->next_in_service, is eligible and has a lower virtual |
| * finish time than sd->next_in_service. If this compound |
| * condition holds, then the new entity becomes the new |
| * next_in_service. Otherwise no change is needed. |
| */ |
| if (new_entity && new_entity != sd->next_in_service) { |
| /* |
| * Flag used to decide whether to replace |
| * sd->next_in_service with new_entity. Tentatively |
| * set to true, and left as true if |
| * sd->next_in_service is NULL. |
| */ |
| change_without_lookup = true; |
| |
| /* |
| * If there is already a next_in_service candidate |
| * entity, then compare timestamps to decide whether |
| * to replace sd->service_tree with new_entity. |
| */ |
| if (next_in_service) { |
| unsigned int new_entity_class_idx = |
| bfq_class_idx(new_entity); |
| struct bfq_service_tree *st = |
| sd->service_tree + new_entity_class_idx; |
| |
| change_without_lookup = |
| (new_entity_class_idx == |
| bfq_class_idx(next_in_service) |
| && |
| !bfq_gt(new_entity->start, st->vtime) |
| && |
| bfq_gt(next_in_service->finish, |
| new_entity->finish)); |
| } |
| |
| if (change_without_lookup) |
| next_in_service = new_entity; |
| } |
| |
| if (!change_without_lookup) /* lookup needed */ |
| next_in_service = bfq_lookup_next_entity(sd, expiration); |
| |
| if (next_in_service) { |
| bool new_budget_triggers_change = |
| bfq_update_parent_budget(next_in_service); |
| |
| parent_sched_may_change = !sd->next_in_service || |
| new_budget_triggers_change; |
| } |
| |
| sd->next_in_service = next_in_service; |
| |
| return parent_sched_may_change; |
| } |
| |
| #ifdef CONFIG_BFQ_GROUP_IOSCHED |
| |
| struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) |
| { |
| struct bfq_entity *group_entity = bfqq->entity.parent; |
| |
| if (!group_entity) |
| group_entity = &bfqq->bfqd->root_group->entity; |
| |
| return container_of(group_entity, struct bfq_group, entity); |
| } |
| |
| /* |
| * Returns true if this budget changes may let next_in_service->parent |
| * become the next_in_service entity for its parent entity. |
| */ |
| static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) |
| { |
| struct bfq_entity *bfqg_entity; |
| struct bfq_group *bfqg; |
| struct bfq_sched_data *group_sd; |
| bool ret = false; |
| |
| group_sd = next_in_service->sched_data; |
| |
| bfqg = container_of(group_sd, struct bfq_group, sched_data); |
| /* |
| * bfq_group's my_entity field is not NULL only if the group |
| * is not the root group. We must not touch the root entity |
| * as it must never become an in-service entity. |
| */ |
| bfqg_entity = bfqg->my_entity; |
| if (bfqg_entity) { |
| if (bfqg_entity->budget > next_in_service->budget) |
| ret = true; |
| bfqg_entity->budget = next_in_service->budget; |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * This function tells whether entity stops being a candidate for next |
| * service, according to the restrictive definition of the field |
| * next_in_service. In particular, this function is invoked for an |
| * entity that is about to be set in service. |
| * |
| * If entity is a queue, then the entity is no longer a candidate for |
| * next service according to the that definition, because entity is |
| * about to become the in-service queue. This function then returns |
| * true if entity is a queue. |
| * |
| * In contrast, entity could still be a candidate for next service if |
| * it is not a queue, and has more than one active child. In fact, |
| * even if one of its children is about to be set in service, other |
| * active children may still be the next to serve, for the parent |
| * entity, even according to the above definition. As a consequence, a |
| * non-queue entity is not a candidate for next-service only if it has |
| * only one active child. And only if this condition holds, then this |
| * function returns true for a non-queue entity. |
| */ |
| static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) |
| { |
| struct bfq_group *bfqg; |
| |
| if (bfq_entity_to_bfqq(entity)) |
| return true; |
| |
| bfqg = container_of(entity, struct bfq_group, entity); |
| |
| /* |
| * The field active_entities does not always contain the |
| * actual number of active children entities: it happens to |
| * not account for the in-service entity in case the latter is |
| * removed from its active tree (which may get done after |
| * invoking the function bfq_no_longer_next_in_service in |
| * bfq_get_next_queue). Fortunately, here, i.e., while |
| * bfq_no_longer_next_in_service is not yet completed in |
| * bfq_get_next_queue, bfq_active_extract has not yet been |
| * invoked, and thus active_entities still coincides with the |
| * actual number of active entities. |
| */ |
| if (bfqg->active_entities == 1) |
| return true; |
| |
| return false; |
| } |
| |
| #else /* CONFIG_BFQ_GROUP_IOSCHED */ |
| |
| struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq) |
| { |
| return bfqq->bfqd->root_group; |
| } |
| |
| static bool bfq_update_parent_budget(struct bfq_entity *next_in_service) |
| { |
| return false; |
| } |
| |
| static bool bfq_no_longer_next_in_service(struct bfq_entity *entity) |
| { |
| return true; |
| } |
| |
| #endif /* CONFIG_BFQ_GROUP_IOSCHED */ |
| |
| /* |
| * Shift for timestamp calculations. This actually limits the maximum |
| * service allowed in one timestamp delta (small shift values increase it), |
| * the maximum total weight that can be used for the queues in the system |
| * (big shift values increase it), and the period of virtual time |
| * wraparounds. |
| */ |
| #define WFQ_SERVICE_SHIFT 22 |
| |
| struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity) |
| { |
| struct bfq_queue *bfqq = NULL; |
| |
| if (!entity->my_sched_data) |
| bfqq = container_of(entity, struct bfq_queue, entity); |
| |
| return bfqq; |
| } |
| |
| |
| /** |
| * bfq_delta - map service into the virtual time domain. |
| * @service: amount of service. |
| * @weight: scale factor (weight of an entity or weight sum). |
| */ |
| static u64 bfq_delta(unsigned long service, unsigned long weight) |
| { |
| return div64_ul((u64)service << WFQ_SERVICE_SHIFT, weight); |
| } |
| |
| /** |
| * bfq_calc_finish - assign the finish time to an entity. |
| * @entity: the entity to act upon. |
| * @service: the service to be charged to the entity. |
| */ |
| static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service) |
| { |
| struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
| |
| entity->finish = entity->start + |
| bfq_delta(service, entity->weight); |
| |
| if (bfqq) { |
| bfq_log_bfqq(bfqq->bfqd, bfqq, |
| "calc_finish: serv %lu, w %d", |
| service, entity->weight); |
| bfq_log_bfqq(bfqq->bfqd, bfqq, |
| "calc_finish: start %llu, finish %llu, delta %llu", |
| entity->start, entity->finish, |
| bfq_delta(service, entity->weight)); |
| } |
| } |
| |
| /** |
| * bfq_entity_of - get an entity from a node. |
| * @node: the node field of the entity. |
| * |
| * Convert a node pointer to the relative entity. This is used only |
| * to simplify the logic of some functions and not as the generic |
| * conversion mechanism because, e.g., in the tree walking functions, |
| * the check for a %NULL value would be redundant. |
| */ |
| struct bfq_entity *bfq_entity_of(struct rb_node *node) |
| { |
| struct bfq_entity *entity = NULL; |
| |
| if (node) |
| entity = rb_entry(node, struct bfq_entity, rb_node); |
| |
| return entity; |
| } |
| |
| /** |
| * bfq_extract - remove an entity from a tree. |
| * @root: the tree root. |
| * @entity: the entity to remove. |
| */ |
| static void bfq_extract(struct rb_root *root, struct bfq_entity *entity) |
| { |
| entity->tree = NULL; |
| rb_erase(&entity->rb_node, root); |
| } |
| |
| /** |
| * bfq_idle_extract - extract an entity from the idle tree. |
| * @st: the service tree of the owning @entity. |
| * @entity: the entity being removed. |
| */ |
| static void bfq_idle_extract(struct bfq_service_tree *st, |
| struct bfq_entity *entity) |
| { |
| struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
| struct rb_node *next; |
| |
| if (entity == st->first_idle) { |
| next = rb_next(&entity->rb_node); |
| st->first_idle = bfq_entity_of(next); |
| } |
| |
| if (entity == st->last_idle) { |
| next = rb_prev(&entity->rb_node); |
| st->last_idle = bfq_entity_of(next); |
| } |
| |
| bfq_extract(&st->idle, entity); |
| |
| if (bfqq) |
| list_del(&bfqq->bfqq_list); |
| } |
| |
| /** |
| * bfq_insert - generic tree insertion. |
| * @root: tree root. |
| * @entity: entity to insert. |
| * |
| * This is used for the idle and the active tree, since they are both |
| * ordered by finish time. |
| */ |
| static void bfq_insert(struct rb_root *root, struct bfq_entity *entity) |
| { |
| struct bfq_entity *entry; |
| struct rb_node **node = &root->rb_node; |
| struct rb_node *parent = NULL; |
| |
| while (*node) { |
| parent = *node; |
| entry = rb_entry(parent, struct bfq_entity, rb_node); |
| |
| if (bfq_gt(entry->finish, entity->finish)) |
| node = &parent->rb_left; |
| else |
| node = &parent->rb_right; |
| } |
| |
| rb_link_node(&entity->rb_node, parent, node); |
| rb_insert_color(&entity->rb_node, root); |
| |
| entity->tree = root; |
| } |
| |
| /** |
| * bfq_update_min - update the min_start field of a entity. |
| * @entity: the entity to update. |
| * @node: one of its children. |
| * |
| * This function is called when @entity may store an invalid value for |
| * min_start due to updates to the active tree. The function assumes |
| * that the subtree rooted at @node (which may be its left or its right |
| * child) has a valid min_start value. |
| */ |
| static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node) |
| { |
| struct bfq_entity *child; |
| |
| if (node) { |
| child = rb_entry(node, struct bfq_entity, rb_node); |
| if (bfq_gt(entity->min_start, child->min_start)) |
| entity->min_start = child->min_start; |
| } |
| } |
| |
| /** |
| * bfq_update_active_node - recalculate min_start. |
| * @node: the node to update. |
| * |
| * @node may have changed position or one of its children may have moved, |
| * this function updates its min_start value. The left and right subtrees |
| * are assumed to hold a correct min_start value. |
| */ |
| static void bfq_update_active_node(struct rb_node *node) |
| { |
| struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node); |
| |
| entity->min_start = entity->start; |
| bfq_update_min(entity, node->rb_right); |
| bfq_update_min(entity, node->rb_left); |
| } |
| |
| /** |
| * bfq_update_active_tree - update min_start for the whole active tree. |
| * @node: the starting node. |
| * |
| * @node must be the deepest modified node after an update. This function |
| * updates its min_start using the values held by its children, assuming |
| * that they did not change, and then updates all the nodes that may have |
| * changed in the path to the root. The only nodes that may have changed |
| * are the ones in the path or their siblings. |
| */ |
| static void bfq_update_active_tree(struct rb_node *node) |
| { |
| struct rb_node *parent; |
| |
| up: |
| bfq_update_active_node(node); |
| |
| parent = rb_parent(node); |
| if (!parent) |
| return; |
| |
| if (node == parent->rb_left && parent->rb_right) |
| bfq_update_active_node(parent->rb_right); |
| else if (parent->rb_left) |
| bfq_update_active_node(parent->rb_left); |
| |
| node = parent; |
| goto up; |
| } |
| |
| /** |
| * bfq_active_insert - insert an entity in the active tree of its |
| * group/device. |
| * @st: the service tree of the entity. |
| * @entity: the entity being inserted. |
| * |
| * The active tree is ordered by finish time, but an extra key is kept |
| * per each node, containing the minimum value for the start times of |
| * its children (and the node itself), so it's possible to search for |
| * the eligible node with the lowest finish time in logarithmic time. |
| */ |
| static void bfq_active_insert(struct bfq_service_tree *st, |
| struct bfq_entity *entity) |
| { |
| struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
| struct rb_node *node = &entity->rb_node; |
| #ifdef CONFIG_BFQ_GROUP_IOSCHED |
| struct bfq_sched_data *sd = NULL; |
| struct bfq_group *bfqg = NULL; |
| struct bfq_data *bfqd = NULL; |
| #endif |
| |
| bfq_insert(&st->active, entity); |
| |
| if (node->rb_left) |
| node = node->rb_left; |
| else if (node->rb_right) |
| node = node->rb_right; |
| |
| 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_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list); |
| #ifdef CONFIG_BFQ_GROUP_IOSCHED |
| if (bfqg != bfqd->root_group) |
| bfqg->active_entities++; |
| #endif |
| } |
| |
| /** |
| * bfq_ioprio_to_weight - calc a weight from an ioprio. |
| * @ioprio: the ioprio value to convert. |
| */ |
| unsigned short bfq_ioprio_to_weight(int ioprio) |
| { |
| return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF; |
| } |
| |
| /** |
| * bfq_weight_to_ioprio - calc an ioprio from a weight. |
| * @weight: the weight value to convert. |
| * |
| * To preserve as much as possible the old only-ioprio user interface, |
| * 0 is used as an escape ioprio value for weights (numerically) equal or |
| * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF. |
| */ |
| static unsigned short bfq_weight_to_ioprio(int weight) |
| { |
| return max_t(int, 0, |
| IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight); |
| } |
| |
| static void bfq_get_entity(struct bfq_entity *entity) |
| { |
| struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity); |
| |
| if (bfqq) { |
| bfqq->ref++; |
| bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d", |
| bfqq, bfqq->ref); |
| } |
| } |
| |
| /** |
| * 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 |
| * last node in the tree return %NULL. |
| */ |
| static struct rb_node *bfq_find_deepest(struct rb_node *node) |
| { |
| struct rb_node *deepest; |
| |
| if (!node->rb_right && !node->rb_left) |
| 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++; |
| } |