@@ -844,7 +844,7 @@ static bool bfq_asymmetric_scenario(struct bfq_data *bfqd,
return varied_queue_weights || multiple_classes_busy
#ifdef CONFIG_BFQ_GROUP_IOSCHED
- || bfqd->num_groups_with_pending_reqs > 0
+ || bfqd->num_groups_with_busy_queues > 0
#endif
;
}
@@ -962,48 +962,6 @@ void __bfq_weights_tree_remove(struct bfq_data *bfqd,
void bfq_weights_tree_remove(struct bfq_data *bfqd,
struct bfq_queue *bfqq)
{
- struct bfq_entity *entity = bfqq->entity.parent;
-
- for_each_entity(entity) {
- struct bfq_sched_data *sd = entity->my_sched_data;
-
- if (sd->next_in_service || sd->in_service_entity) {
- /*
- * entity is still active, because either
- * next_in_service or in_service_entity is not
- * NULL (see the comments on the definition of
- * next_in_service for details on why
- * in_service_entity must be checked too).
- *
- * As a consequence, its parent entities are
- * active as well, and thus this loop must
- * stop here.
- */
- break;
- }
-
- /*
- * The decrement of num_groups_with_pending_reqs is
- * not performed immediately upon the deactivation of
- * entity, but it is delayed to when it also happens
- * that the first leaf descendant bfqq of entity gets
- * all its pending requests completed. The following
- * instructions perform this delayed decrement, if
- * needed. See the comments on
- * num_groups_with_pending_reqs for details.
- */
- if (entity->in_groups_with_pending_reqs) {
- entity->in_groups_with_pending_reqs = false;
- bfqd->num_groups_with_pending_reqs--;
- }
- }
-
- /*
- * Next function is invoked last, because it causes bfqq to be
- * freed if the following holds: bfqq is not in service and
- * has no dispatched request. DO NOT use bfqq after the next
- * function invocation.
- */
__bfq_weights_tree_remove(bfqd, bfqq,
&bfqd->queue_weights_tree);
}
@@ -7107,7 +7065,7 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
bfqd->queue_weights_tree = RB_ROOT_CACHED;
- bfqd->num_groups_with_pending_reqs = 0;
+ bfqd->num_groups_with_busy_queues = 0;
INIT_LIST_HEAD(&bfqd->active_list);
INIT_LIST_HEAD(&bfqd->idle_list);
@@ -197,9 +197,6 @@ struct bfq_entity {
/* flag, set to request a weight, ioprio or ioprio_class change */
int prio_changed;
- /* flag, set if the entity is counted in groups_with_pending_reqs */
- bool in_groups_with_pending_reqs;
-
/* last child queue of entity created (for non-leaf entities) */
struct bfq_queue *last_bfqq_created;
};
@@ -495,52 +492,14 @@ struct bfq_data {
struct rb_root_cached queue_weights_tree;
/*
- * Number of groups with at least one descendant process that
- * has at least one request waiting for completion. Note that
- * this accounts for also requests already dispatched, but not
- * yet completed. Therefore this number of groups may differ
- * (be larger) than the number of active groups, as a group is
- * considered active only if its corresponding entity has
- * descendant queues with at least one request queued. This
- * number is used to decide whether a scenario is symmetric.
- * For a detailed explanation see comments on the computation
- * of the variable asymmetric_scenario in the function
- * bfq_better_to_idle().
- *
- * However, it is hard to compute this number exactly, for
- * groups with multiple descendant processes. Consider a group
- * that is inactive, i.e., that has no descendant process with
- * pending I/O inside BFQ queues. Then suppose that
- * num_groups_with_pending_reqs is still accounting for this
- * group, because the group has descendant processes with some
- * I/O request still in flight. num_groups_with_pending_reqs
- * should be decremented when the in-flight request of the
- * last descendant process is finally completed (assuming that
- * nothing else has changed for the group in the meantime, in
- * terms of composition of the group and active/inactive state of child
- * groups and processes). To accomplish this, an additional
- * pending-request counter must be added to entities, and must
- * be updated correctly. To avoid this additional field and operations,
- * we resort to the following tradeoff between simplicity and
- * accuracy: for an inactive group that is still counted in
- * num_groups_with_pending_reqs, we decrement
- * num_groups_with_pending_reqs when the first descendant
- * process of the group remains with no request waiting for
- * completion.
- *
- * Even this simpler decrement strategy requires a little
- * carefulness: to avoid multiple decrements, we flag a group,
- * more precisely an entity representing a group, as still
- * counted in num_groups_with_pending_reqs when it becomes
- * inactive. Then, when the first descendant queue of the
- * entity remains with no request waiting for completion,
- * num_groups_with_pending_reqs is decremented, and this flag
- * is reset. After this flag is reset for the entity,
- * num_groups_with_pending_reqs won't be decremented any
- * longer in case a new descendant queue of the entity remains
- * with no request waiting for completion.
+ * Number of groups with at least one bfqq that is marked busy,
+ * and this number is used to decide whether a scenario is symmetric.
+ * Note that bfqq is busy doesn't mean that the bfqq contains requests.
+ * If idling is needed for service guarantees, bfqq will stay busy
+ * after dispatching the last request, see details in
+ * __bfq_bfqq_expire().
*/
- unsigned int num_groups_with_pending_reqs;
+ unsigned int num_groups_with_busy_queues;
/*
* Per-class (RT, BE, IDLE) number of bfq_queues containing
@@ -220,12 +220,14 @@ static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
static void bfq_inc_busy_queues(struct bfq_queue *bfqq)
{
- bfqq_group(bfqq)->busy_queues++;
+ if (!(bfqq_group(bfqq)->busy_queues++))
+ bfqq->bfqd->num_groups_with_busy_queues++;
}
static void bfq_dec_busy_queues(struct bfq_queue *bfqq)
{
- bfqq_group(bfqq)->busy_queues--;
+ if (!(--bfqq_group(bfqq)->busy_queues))
+ bfqq->bfqd->num_groups_with_busy_queues--;
}
#else /* CONFIG_BFQ_GROUP_IOSCHED */
@@ -1002,19 +1004,6 @@ static void __bfq_activate_entity(struct bfq_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);
}