block: recursive merge requests
In a workload, thread 1 accesses a, a+2, ..., thread 2 accesses a+1, a+3,.... When the requests are flushed to queue, a and a+1 are merged to (a, a+1), a+2 and a+3 too to (a+2, a+3), but (a, a+1) and (a+2, a+3) aren't merged. If we do recursive merge for such interleave access, some workloads throughput get improvement. A recent worload I'm checking on is swap, below change boostes the throughput around 5% ~ 10%. Signed-off-by: Shaohua Li <shli@fusionio.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -458,6 +458,7 @@ static bool elv_attempt_insert_merge(struct request_queue *q,
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struct request *rq)
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{
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struct request *__rq;
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bool ret;
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if (blk_queue_nomerges(q))
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return false;
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@ -471,14 +472,21 @@ static bool elv_attempt_insert_merge(struct request_queue *q,
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if (blk_queue_noxmerges(q))
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return false;
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ret = false;
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/*
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* See if our hash lookup can find a potential backmerge.
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*/
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__rq = elv_rqhash_find(q, blk_rq_pos(rq));
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if (__rq && blk_attempt_req_merge(q, __rq, rq))
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return true;
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while (1) {
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__rq = elv_rqhash_find(q, blk_rq_pos(rq));
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if (!__rq || !blk_attempt_req_merge(q, __rq, rq))
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break;
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return false;
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/* The merged request could be merged with others, try again */
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ret = true;
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rq = __rq;
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}
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return ret;
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}
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void elv_merged_request(struct request_queue *q, struct request *rq, int type)
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