[PATCH v3 11/14] bfq: disable idle for prio_expire under better_fairness

[brookxu]

From: Chunguang Xu <broo...@tencent.com>

Under better_fairness, if higher priority queue is waiting
for service，disable queue idle, so that a schedule can be
invoked in time. In addition to CLASS_IDLE, other queues
allow idle, so that we can better control buffer IO too.

Signed-off-by: Chunguang Xu <broo...@tencent.com>
---
 block/bfq-iosched.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index be5b1e3..5aa9c2c 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4307,6 +4307,14 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq)
                return true;
 
        /*
+        * In better_fairness mode, we also put emphasis on Qos. The main
+        * purpose of allowing idle here is to ensure better isolation
+        * of Buffer IO.
+        */
+       if (unlikely(bfqd->better_fairness))
+               return !(bfqd->bfq_slice_idle == 0 || bfq_class_idle(bfqq));
+
+       /*
         * Idling is performed only if slice_idle > 0. In addition, we
         * do not idle if
         * (a) bfqq is async
@@ -4318,6 +4326,9 @@ static bool bfq_better_to_idle(struct bfq_queue *bfqq)
           bfq_class_idle(bfqq))
                return false;
 
+       if (bfq_may_expire_in_serv_for_prio(&bfqq->entity))
+               return false;
+
        idling_boosts_thr_with_no_issue =
                idling_boosts_thr_without_issues(bfqd, bfqq);
 
-- 
1.8.3.1