[PATCH v3 09/14] bfq: expire in_serv_queue for prio_expire under better_fairness

brookxu
2021-03-25T06:59:21Z

Traverse all schedule domains upward, if there are higher
priority tasks waiting for service, mark in_service_queue
prio_expire and then expire it, so the So RT tasks can be
scheduled in time.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
---
block/bfq-iosched.c | 7 +++----
block/bfq-iosched.h | 1 +
block/bfq-wf2q.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 6e19b5a..51192bd 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4736,10 +4736,9 @@ static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd,
* belongs to CLASS_IDLE and other queues are waiting for
* service.
*/
- if (!(bfq_tot_busy_queues(bfqd) > 1 && bfq_class_idle(bfqq)))
- goto return_rq;
-
- bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED);
+ if ((bfq_tot_busy_queues(bfqd) > 1 && bfq_class_idle(bfqq)) ||
+ bfq_bfqq_prio_expire(bfqq))
+ bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED);

return_rq:
return rq;
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 8af5ac0..1406398 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -989,6 +989,7 @@ void bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq,
void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq);
void bfq_schedule_dispatch(struct bfq_data *bfqd);
void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
+bool bfq_may_expire_in_serv_for_prio(struct bfq_entity *entity);

/* ------------ end of main algorithm interface -------------- */

diff --git a/block/bfq-wf2q.c b/block/bfq-wf2q.c
index 1f8f3c5..b477a9b 100644
--- a/block/bfq-wf2q.c
+++ b/block/bfq-wf2q.c
@@ -161,6 +161,51 @@ struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
return bfq_entity_to_bfqg(group_entity);
}

+bool bfq_may_expire_in_serv_for_prio(struct bfq_entity *entity)
+{
+ struct bfq_sched_data *sd;
+ struct bfq_queue *bfqq;
+ struct bfq_group *bfqg;
+ bool ret = false;
+
+ sd = entity->sched_data;
+ bfqg = container_of(sd, struct bfq_group, sched_data);
+
+ if (likely(!bfqg->bfqd->better_fairness))
+ return false;
+
+ bfqq = bfqg->bfqd->in_service_queue;
+ if (bfqq) {
+ struct bfq_entity *next_in_serv;
+
+ /*
+ * Traverse the upper-level scheduling domain for
+ * prio preemption, and expire in_service_queue
+ * if necessary.
+ */
+ entity = &bfqq->entity;
+ for_each_entity(entity) {
+ sd = entity->sched_data;
+ next_in_serv = sd->next_in_service;
+
+ if (!next_in_serv)
+ continue;
+
+ /*
+ * Expire bfqq, if next_in_serv belongs to
+ * a higher class.
+ */
+ if (bfq_class_idx(next_in_serv) <
+ bfq_class_idx(entity)) {
+ bfq_mark_bfqq_prio_expire(bfqq);
+ ret = true;
+ break;
+ }
+ }
+ }
+ return ret;
+}
+
/*
* Returns true if this budget changes may let next_in_service->parent
* become the next_in_service entity for its parent entity.
@@ -244,6 +289,11 @@ struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
return bfqq->bfqd->root_group;
}

+bool bfq_may_expire_in_serv_for_prio(struct bfq_entity *entity)
+{
+ return false;
+}
+
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
{
return false;
@@ -1162,6 +1212,7 @@ static void bfq_activate_requeue_entity(struct bfq_entity *entity,
bool non_blocking_wait_rq,
bool requeue, bool expiration)
{
+ struct bfq_entity *old_entity = entity;
struct bfq_sched_data *sd;

for_each_entity(entity) {
@@ -1172,6 +1223,15 @@ static void bfq_activate_requeue_entity(struct bfq_entity *entity,
!requeue)
break;
}
+
+ /*
+ * Expire in_service_queue, if a task belongs to higher class
+ * is added to the upper-level scheduling domain, we should
+ * initiate a new schedule. But here is just to mark bfqq
+ * prio_expire, the real schedule occurs in
+ * bfq_dispatch_rq_from_bfqq().
+ */
+ bfq_may_expire_in_serv_for_prio(old_entity);
}

/**
--
1.8.3.1