blk-mq: Micro-optimize blk_queue_nomerges() check
In blk_mq_make_request(), do the blk_queue_nomerges() check outside the call to blk_attempt_plug_merge() to eliminate function call overhead when nomerges=2 (disabled) Signed-off-by: Robert Elliott <elliott@hp.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -1471,6 +1471,8 @@ bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
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* added on the elevator at this point. In addition, we don't have
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* reliable access to the elevator outside queue lock. Only check basic
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* merging parameters without querying the elevator.
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*
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* Caller must ensure !blk_queue_nomerges(q) beforehand.
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*/
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bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
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unsigned int *request_count)
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@ -1480,9 +1482,6 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
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bool ret = false;
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struct list_head *plug_list;
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if (blk_queue_nomerges(q))
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goto out;
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plug = current->plug;
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if (!plug)
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goto out;
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@ -1561,7 +1560,8 @@ void blk_queue_bio(struct request_queue *q, struct bio *bio)
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* Check if we can merge with the plugged list before grabbing
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* any locks.
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*/
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if (blk_attempt_plug_merge(q, bio, &request_count))
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if (!blk_queue_nomerges(q) &&
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blk_attempt_plug_merge(q, bio, &request_count))
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return;
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spin_lock_irq(q->queue_lock);
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@ -1087,7 +1087,8 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
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return;
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}
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if (use_plug && blk_attempt_plug_merge(q, bio, &request_count))
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if (use_plug && !blk_queue_nomerges(q) &&
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blk_attempt_plug_merge(q, bio, &request_count))
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return;
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if (blk_mq_queue_enter(q)) {
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