path: root/block/bfq-iosched.c
diff options
authorAngelo Ruocco <>2017-12-20 12:38:32 +0100
committerJens Axboe <>2018-01-05 09:26:08 -0700
commit1be6e8a964ee9aa8d4daac523ce29e5f486dd756 (patch)
treea3178e2aae065ca5d434daf554c0f1d6d19e967b /block/bfq-iosched.c
parent05e90283561648301e30232fe0c91bd345ceba03 (diff)
block, bfq: check low_latency flag in bfq_bfqq_save_state()
A just-created bfq_queue will certainly be deemed as interactive on the arrival of its first I/O request, if the low_latency flag is set. Yet, if the queue is merged with another queue on the arrival of its first I/O request, it will not have the chance to be flagged as interactive. Nevertheless, if the queue is then split soon enough, it has to be flagged as interactive after the split. To handle this early-merge scenario correctly, BFQ saves the state of the queue, on the merge, as if the latter had already been deemed interactive. So, if the queue is split soon, it will get weight-raised, because the previous state of the queue is resumed on the split. Unfortunately, in the act of saving the state of the newly-created queue, BFQ doesn't check whether the low_latency flag is set, and this causes early-merged queues to be then weight-raised, on queue splits, even if low_latency is off. This commit addresses this problem by adding the missing check. Signed-off-by: Angelo Ruocco <> Signed-off-by: Paolo Valente <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/bfq-iosched.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index fa395a2..2cf395d 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -2064,7 +2064,8 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
if (unlikely(bfq_bfqq_just_created(bfqq) &&
- !bfq_bfqq_in_large_burst(bfqq))) {
+ !bfq_bfqq_in_large_burst(bfqq) &&
+ bfqq->bfqd->low_latency)) {
* bfqq being merged right after being created: bfqq
* would have deserved interactive weight raising, but