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authorJan Kara <jack@suse.cz>2020-06-17 15:58:23 +0200
committerJens Axboe <axboe@kernel.dk>2020-06-25 21:06:11 -0600
commitf3bdc62fd82ed93dbe4d049eacba310de7eb2a6a (patch)
treeeefbacc996ba10e58a127a7a2df8924e4bbb0179 /block
parent621c1f42945e76015c3a585e7a9fe6e71665eba0 (diff)
blktrace: Provide event for request merging
Currently blk-mq does not report any event when two requests get merged in the elevator. This then results in difficult to understand sequence of events like: ... 8,0 34 1579 0.608765271 2718 I WS 215023504 + 40 [dbench] 8,0 34 1584 0.609184613 2719 A WS 215023544 + 56 <- (8,4) 2160568 8,0 34 1585 0.609184850 2719 Q WS 215023544 + 56 [dbench] 8,0 34 1586 0.609188524 2719 G WS 215023544 + 56 [dbench] 8,0 3 602 0.609684162 773 D WS 215023504 + 96 [kworker/3:1H] 8,0 34 1591 0.609843593 0 C WS 215023504 + 96 [0] and you can only guess (after quite some headscratching since the above excerpt is intermixed with a lot of other IO) that request 215023544+56 got merged to request 215023504+40. Provide proper event for request merging like we used to do in the legacy block layer. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-merge.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index f0b0bae075a0..9c9fb21584b6 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -793,6 +793,8 @@ static struct request *attempt_merge(struct request_queue *q,
*/
blk_account_io_merge_request(next);
+ trace_block_rq_merge(q, next);
+
/*
* ownership of bio passed from next to req, return 'next' for
* the caller to free