diff options
Diffstat (limited to 'block')
| -rw-r--r-- | block/bfq-iosched.c | 24 |
1 files changed, 19 insertions, 5 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 375e35c3d2fb..44c6433b5b25 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1649,6 +1649,8 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq, return bfqq_weight > in_serv_weight; } +static bool bfq_better_to_idle(struct bfq_queue *bfqq); + static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, struct bfq_queue *bfqq, int old_wr_coeff, @@ -1750,10 +1752,10 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, bfq_add_bfqq_busy(bfqd, bfqq); /* - * Expire in-service queue only if preemption may be needed - * for guarantees. In particular, we care only about two - * cases. The first is that bfqq has to recover a service - * hole, as explained in the comments on + * Expire in-service queue if preemption may be needed for + * guarantees or throughput. As for guarantees, we care + * explicitly about two cases. The first is that bfqq has to + * recover a service hole, as explained in the comments on * bfq_bfqq_update_budg_for_activation(), i.e., that * bfqq_wants_to_preempt is true. However, if bfqq does not * carry time-critical I/O, then bfqq's bandwidth is less @@ -1780,11 +1782,23 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd, * timestamps of the in-service queue would need to be * updated, and this operation is quite costly (see the * comments on bfq_bfqq_update_budg_for_activation()). + * + * As for throughput, we ask bfq_better_to_idle() whether we + * still need to plug I/O dispatching. If bfq_better_to_idle() + * says no, then plugging is not needed any longer, either to + * boost throughput or to perserve service guarantees. Then + * the best option is to stop plugging I/O, as not doing so + * would certainly lower throughput. We may end up in this + * case if: (1) upon a dispatch attempt, we detected that it + * was better to plug I/O dispatch, and to wait for a new + * request to arrive for the currently in-service queue, but + * (2) this switch of bfqq to busy changes the scenario. */ if (bfqd->in_service_queue && ((bfqq_wants_to_preempt && bfqq->wr_coeff >= bfqd->in_service_queue->wr_coeff) || - bfq_bfqq_higher_class_or_weight(bfqq, bfqd->in_service_queue)) && + bfq_bfqq_higher_class_or_weight(bfqq, bfqd->in_service_queue) || + !bfq_better_to_idle(bfqd->in_service_queue)) && next_queue_may_preempt(bfqd)) bfq_bfqq_expire(bfqd, bfqd->in_service_queue, false, BFQQE_PREEMPTED); |