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| author | Ming Lei <ming.lei@redhat.com> | 2017-10-14 17:22:29 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-11-01 08:20:02 -0600 |
| commit | de1482974080ec9ef414bf048b2646b246b63f6e (patch) | |
| tree | 3ecdc2b581a83848c43205c2fd9b6e97a6808f6a /block/blk-mq.h | |
| parent | 63ba8e31c3ac6393b07c6e18538814a730478766 (diff) | |
| download | lwn-de1482974080ec9ef414bf048b2646b246b63f6e.tar.gz lwn-de1482974080ec9ef414bf048b2646b246b63f6e.zip | |
blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
For SCSI devices, there is often a per-request-queue depth, which needs
to be respected before queuing one request.
Currently blk-mq always dequeues the request first, then calls
.queue_rq() to dispatch the request to lld. One obvious issue with this
approach is that I/O merging may not be successful, because when the
per-request-queue depth can't be respected, .queue_rq() has to return
BLK_STS_RESOURCE, and then this request has to stay in hctx->dispatch
list. This means it never gets a chance to be merged with other IO.
This patch introduces .get_budget and .put_budget callback in blk_mq_ops,
then we can try to get reserved budget first before dequeuing request.
If the budget for queueing I/O can't be satisfied, we don't need to
dequeue request at all. Hence the request can be left in the IO
scheduler queue, for more merging opportunities.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.h')
| -rw-r--r-- | block/blk-mq.h | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/block/blk-mq.h b/block/blk-mq.h index ef15b3414da5..e413b732374e 100644 --- a/block/blk-mq.h +++ b/block/blk-mq.h @@ -30,7 +30,7 @@ void blk_mq_freeze_queue(struct request_queue *q); void blk_mq_free_queue(struct request_queue *q); int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr); void blk_mq_wake_waiters(struct request_queue *q); -bool blk_mq_dispatch_rq_list(struct request_queue *, struct list_head *); +bool blk_mq_dispatch_rq_list(struct request_queue *, struct list_head *, bool); void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list); bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx); bool blk_mq_get_driver_tag(struct request *rq, struct blk_mq_hw_ctx **hctx, @@ -137,4 +137,22 @@ static inline bool blk_mq_hw_queue_mapped(struct blk_mq_hw_ctx *hctx) void blk_mq_in_flight(struct request_queue *q, struct hd_struct *part, unsigned int inflight[2]); +static inline void blk_mq_put_dispatch_budget(struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + + if (q->mq_ops->put_budget) + q->mq_ops->put_budget(hctx); +} + +static inline blk_status_t blk_mq_get_dispatch_budget( + struct blk_mq_hw_ctx *hctx) +{ + struct request_queue *q = hctx->queue; + + if (q->mq_ops->get_budget) + return q->mq_ops->get_budget(hctx); + return BLK_STS_OK; +} + #endif |