From bee0393cc12b6d8f10e884e555a095e050e0b2b9 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Fri, 9 Nov 2012 08:44:27 +0100 Subject: 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 Signed-off-by: Jens Axboe --- block/elevator.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'block') diff --git a/block/elevator.c b/block/elevator.c index 9b1d42b62f20..9edba1b8323e 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -458,6 +458,7 @@ static bool elv_attempt_insert_merge(struct request_queue *q, struct request *rq) { struct request *__rq; + bool ret; if (blk_queue_nomerges(q)) return false; @@ -471,14 +472,21 @@ static bool elv_attempt_insert_merge(struct request_queue *q, if (blk_queue_noxmerges(q)) return false; + ret = false; /* * See if our hash lookup can find a potential backmerge. */ - __rq = elv_rqhash_find(q, blk_rq_pos(rq)); - if (__rq && blk_attempt_req_merge(q, __rq, rq)) - return true; + while (1) { + __rq = elv_rqhash_find(q, blk_rq_pos(rq)); + if (!__rq || !blk_attempt_req_merge(q, __rq, rq)) + break; - return false; + /* The merged request could be merged with others, try again */ + ret = true; + rq = __rq; + } + + return ret; } void elv_merged_request(struct request_queue *q, struct request *rq, int type) -- cgit v1.2.3