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https://github.com/edk2-porting/linux-next.git
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431b17f9d5
On each deactivation or re-scheduling (after being served) of a bfq_queue, BFQ invokes the function __bfq_entity_update_weight_prio(), to perform pending updates of ioprio, weight and ioprio class for the bfq_queue. BFQ also invokes this function on I/O-request dispatches, to raise or lower weights more quickly when needed, thereby improving latency. However, the entity representing the bfq_queue may be on the active (sub)tree of a service tree when this happens, and, although with a very low probability, the bfq_queue may happen to also have a pending change of its ioprio class. If both conditions hold when __bfq_entity_update_weight_prio() is invoked, then the entity moves to a sort of hybrid state: the new service tree for the entity, as returned by bfq_entity_service_tree(), differs from service tree on which the entity still is. The functions that handle activations and deactivations of entities do not cope with such a hybrid state (and would need to become more complex to cope). This commit addresses this issue by just making __bfq_entity_update_weight_prio() not perform also a possible pending change of ioprio class, when invoked on an I/O-request dispatch for a bfq_queue. Such a change is thus postponed to when __bfq_entity_update_weight_prio() is invoked on deactivation or re-scheduling of the bfq_queue. Reported-by: Marco Piazza <mpiazza@gmail.com> Reported-by: Laurentiu Nicola <lnicola@dend.ro> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1655 lines
50 KiB
C
1655 lines
50 KiB
C
/*
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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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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include "bfq-iosched.h"
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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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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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return rb_entry(node, struct bfq_entity, rb_node);
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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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return bfqq ? bfqq->ioprio_class - 1 :
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BFQ_DEFAULT_GRP_CLASS - 1;
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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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static bool bfq_update_parent_budget(struct bfq_entity *next_in_service);
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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 repositionig triggered the invocation of
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* this function.
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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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{
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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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/*
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* If this update is triggered by the activation, requeueing
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* or repositiong 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 a higher priority than
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* sd->next_in_service, or, even if it has the same priority
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* as 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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bool replace_next = true;
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/*
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* If there is already a next_in_service candidate
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* entity, then compare class priorities or timestamps
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* to decide whether to replace sd->service_tree with
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* 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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* For efficiency, evaluate the most likely
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* sub-condition first.
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*/
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replace_next =
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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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new_entity_class_idx <
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bfq_class_idx(next_in_service);
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}
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if (replace_next)
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next_in_service = new_entity;
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} else /* invoked because of a deactivation: lookup needed */
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next_in_service = bfq_lookup_next_entity(sd);
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if (next_in_service) {
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parent_sched_may_change = !sd->next_in_service ||
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bfq_update_parent_budget(next_in_service);
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}
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sd->next_in_service = next_in_service;
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if (!next_in_service)
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return parent_sched_may_change;
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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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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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* 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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return ret;
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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 following logic.
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*
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* This function is invoked for an entity that is about to be set in
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* service. If such an entity is a queue, then the entity is no longer
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* a candidate for next service (i.e, a candidate entity to serve
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* after the in-service entity is expired). The function then returns
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* true.
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*
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* In contrast, the entity could stil be a candidate for next service
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* if it is not a queue, and has more than one child. In fact, even if
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* one of its children is about to be set in service, other children
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* may still be the next to serve. As a consequence, a non-queue
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* entity is not a candidate for next-service only if it has only one
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* child. And only if this condition holds, then the function returns
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* 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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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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if (bfqg->active_entities == 1)
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return true;
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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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* 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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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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u64 d = (u64)service << WFQ_SERVICE_SHIFT;
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do_div(d, weight);
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return d;
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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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* 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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* 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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* 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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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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* 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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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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entity->tree = root;
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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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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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* 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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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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* 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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up:
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bfq_update_active_node(node);
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parent = rb_parent(node);
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if (!parent)
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return;
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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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node = parent;
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goto up;
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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);
|
|
|
|
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
|
|
else /* bfq_group */
|
|
bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree);
|
|
|
|
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
|
|
else /* bfq_group */
|
|
bfq_weights_tree_remove(bfqd, entity,
|
|
&bfqd->group_weights_tree);
|
|
|
|
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 = 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 *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
|
|
|
|
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, remove the entity
|
|
* from its old weight counter (if there is a counter
|
|
* associated with the entity), and add it to the counter
|
|
* associated with its new weight.
|
|
*/
|
|
if (prev_weight != new_weight) {
|
|
root = bfqq ? &bfqd->queue_weights_tree :
|
|
&bfqd->group_weights_tree;
|
|
bfq_weights_tree_remove(bfqd, entity, root);
|
|
}
|
|
entity->weight = new_weight;
|
|
/*
|
|
* Add the entity to its weights tree only if it is
|
|
* not associated with a weight-raised queue.
|
|
*/
|
|
if (prev_weight != new_weight &&
|
|
(bfqq ? bfqq->wr_coeff == 1 : 1))
|
|
/* If we get here, root has been initialized. */
|
|
bfq_weights_tree_add(bfqd, entity, 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;
|
|
|
|
for_each_entity(entity) {
|
|
st = bfq_entity_service_tree(entity);
|
|
|
|
entity->service += served;
|
|
|
|
st->vtime += bfq_delta(served, st->wsum);
|
|
bfq_forget_idle(st);
|
|
}
|
|
bfqg_stats_set_start_empty_time(bfqq_group(bfqq));
|
|
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;
|
|
int tot_serv_to_charge = entity->service;
|
|
unsigned int timeout_ms = jiffies_to_msecs(bfq_timeout);
|
|
|
|
if (time_ms > 0 && time_ms < timeout_ms)
|
|
tot_serv_to_charge =
|
|
(bfqd->bfq_max_budget * time_ms) / timeout_ms;
|
|
|
|
if (tot_serv_to_charge < entity->service)
|
|
tot_serv_to_charge = 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, ater possible 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 = true;
|
|
}
|
|
|
|
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 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_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
|
|
*/
|
|
static void bfq_activate_requeue_entity(struct bfq_entity *entity,
|
|
bool non_blocking_wait_rq,
|
|
bool requeue)
|
|
{
|
|
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) && !requeue)
|
|
break;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __bfq_deactivate_entity - deactivate an entity from its service tree.
|
|
* @entity: the entity to deactivate.
|
|
* @ins_into_idle_tree: if false, the entity will not be put into the
|
|
* idle tree.
|
|
*
|
|
* Deactivates an entity, independently from its previous state. Must
|
|
* be invoked only if entity is on a service tree. Extracts the entity
|
|
* from that tree, and if necessary and allowed, puts it on the idle
|
|
* tree.
|
|
*/
|
|
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) /* 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;
|
|
|
|
if (is_in_service)
|
|
bfq_calc_finish(entity, entity->service);
|
|
|
|
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 on the idle tree
|
|
*/
|
|
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);
|
|
|
|
if (sd->next_in_service)
|
|
/*
|
|
* The parent entity is still backlogged,
|
|
* because next_in_service 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.
|
|
*/
|
|
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)
|
|
/*
|
|
* 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 constrast, 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.
|
|
*
|
|
* This function is invoked when there has been a change in the trees
|
|
* for sd, and we need know what is the new next entity after this
|
|
* change.
|
|
*/
|
|
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd)
|
|
{
|
|
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++) {
|
|
entity = __bfq_lookup_next_entity(st + class_idx,
|
|
sd->in_service_entity);
|
|
|
|
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 (bfqd->busy_queues == 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;
|
|
|
|
/*
|
|
* Reset the accumulator of the amount of service that
|
|
* the entity is about to receive.
|
|
*/
|
|
entity->service = 0;
|
|
|
|
/*
|
|
* If entity is no longer a candidate for next
|
|
* service, then we extract it from its active tree,
|
|
* for the following reason. To further boost the
|
|
* throughput in some special case, BFQ needs to know
|
|
* which is the next candidate entity to serve, while
|
|
* there is already an entity in service. In this
|
|
* respect, to make it easy to compute/update the next
|
|
* candidate entity to serve after the current
|
|
* candidate has been set in service, there is a case
|
|
* where it is necessary to extract the current
|
|
* candidate from its service tree. Such a case is
|
|
* when the entity just set in service cannot be also
|
|
* a candidate for next service. Details about when
|
|
* this conditions holds are reported in the comments
|
|
* on the function bfq_no_longer_next_in_service()
|
|
* invoked below.
|
|
*/
|
|
if (bfq_no_longer_next_in_service(entity))
|
|
bfq_active_extract(bfq_entity_service_tree(entity),
|
|
entity);
|
|
|
|
/*
|
|
* For the same reason why we may have just extracted
|
|
* entity from its active tree, we may need to update
|
|
* next_in_service for the sched_data of entity too,
|
|
* regardless of whether entity has been extracted.
|
|
* In fact, even if entity has not been extracted, a
|
|
* descendant entity may get extracted. Such an event
|
|
* would cause a change in next_in_service for the
|
|
* level of the descendant entity, and thus possibly
|
|
* back to upper levels.
|
|
*
|
|
* We cannot perform the resulting needed update
|
|
* before the end of this 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))
|
|
break;
|
|
}
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
void __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)
|
|
bfq_put_queue(in_serv_bfqq);
|
|
}
|
|
|
|
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);
|
|
bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
|
|
}
|
|
|
|
void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
bfq_activate_requeue_entity(entity, false,
|
|
bfqq == bfqd->in_service_queue);
|
|
}
|
|
|
|
/*
|
|
* 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--;
|
|
|
|
if (!bfqq->dispatched)
|
|
bfq_weights_tree_remove(bfqd, &bfqq->entity,
|
|
&bfqd->queue_weights_tree);
|
|
|
|
if (bfqq->wr_coeff > 1)
|
|
bfqd->wr_busy_queues--;
|
|
|
|
bfqg_stats_update_dequeue(bfqq_group(bfqq));
|
|
|
|
bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
|
|
}
|
|
|
|
/*
|
|
* 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++;
|
|
|
|
if (!bfqq->dispatched)
|
|
if (bfqq->wr_coeff == 1)
|
|
bfq_weights_tree_add(bfqd, &bfqq->entity,
|
|
&bfqd->queue_weights_tree);
|
|
|
|
if (bfqq->wr_coeff > 1)
|
|
bfqd->wr_busy_queues++;
|
|
}
|