block, bfq: consider also ioprio classes in symmetry detection

In asymmetric scenarios, i.e., when some bfq_queue or bfq_group needs to
be guaranteed a different bandwidth than other bfq_queues or bfq_groups,
these service guaranteed can be provided only by plugging I/O dispatch,
completely or partially, when the queue in service remains temporarily
empty. A case where asymmetry is particularly strong is when some active
bfq_queues belong to a higher-priority class than some other active
bfq_queues. Unfortunately, this important case is not considered at all
in the code for detecting asymmetric scenarios. This commit adds the
missing logic.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 5 insertions, 3 deletions

diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 0b02bf302de0..30be669be465 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -501,10 +501,11 @@ struct bfq_data {
 	unsigned int num_groups_with_pending_reqs;
 
 	/*
-	 * Number of bfq_queues containing requests (including the
-	 * queue in service, even if it is idling).
+	 * Per-class (RT, BE, IDLE) number of bfq_queues containing
+	 * requests (including the queue in service, even if it is
+	 * idling).
 	 */
-	int busy_queues;
+	unsigned int busy_queues[3];
 	/* number of weight-raised busy @bfq_queues */
 	int wr_busy_queues;
 	/* number of queued requests */
@@ -974,6 +975,7 @@ extern struct blkcg_policy blkcg_policy_bfq;
 
 struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq);
 struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
+unsigned int bfq_tot_busy_queues(struct bfq_data *bfqd);
 struct bfq_service_tree *bfq_entity_service_tree(struct bfq_entity *entity);
 struct bfq_entity *bfq_entity_of(struct rb_node *node);
 unsigned short bfq_ioprio_to_weight(int ioprio);