The original commit is commit
1a1238a7dd48 ("cfq-iosched: improve hw_tag
detection") and has the following commit message:
If active queue hasn't enough requests and idle window opens, cfq will
not dispatch sufficient requests to hardware. In such situation, current
code will zero hw_tag. But this is because cfq doesn't dispatch enough
requests instead of hardware queue doesn't work. Don't zero hw_tag in
such case.
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
static void bfq_update_hw_tag(struct bfq_data *bfqd)
{
+ struct bfq_queue *bfqq = bfqd->in_service_queue;
+
bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver,
bfqd->rq_in_driver);
if (bfqd->rq_in_driver + bfqd->queued <= BFQ_HW_QUEUE_THRESHOLD)
return;
+ /*
+ * If active queue hasn't enough requests and can idle, bfq might not
+ * dispatch sufficient requests to hardware. Don't zero hw_tag in this
+ * case
+ */
+ if (bfqq && bfq_bfqq_has_short_ttime(bfqq) &&
+ bfqq->dispatched + bfqq->queued[0] + bfqq->queued[1] <
+ BFQ_HW_QUEUE_THRESHOLD &&
+ bfqd->rq_in_driver < BFQ_HW_QUEUE_THRESHOLD)
+ return;
+
if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
return;