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authorMing Lei <ming.lei@redhat.com>2017-10-14 17:22:29 +0800
committerJens Axboe <axboe@kernel.dk>2017-11-01 08:20:02 -0600
commitde1482974080ec9ef414bf048b2646b246b63f6e (patch)
tree3ecdc2b581a83848c43205c2fd9b6e97a6808f6a /block/blk-mq.h
parent63ba8e31c3ac6393b07c6e18538814a730478766 (diff)
downloadlwn-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.h20
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