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| author | Jan Kara <jack@suse.cz> | 2020-06-17 15:58:23 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-06-25 21:06:11 -0600 |
| commit | f3bdc62fd82ed93dbe4d049eacba310de7eb2a6a (patch) | |
| tree | eefbacc996ba10e58a127a7a2df8924e4bbb0179 /block | |
| parent | 621c1f42945e76015c3a585e7a9fe6e71665eba0 (diff) | |
| download | lwn-f3bdc62fd82ed93dbe4d049eacba310de7eb2a6a.tar.gz lwn-f3bdc62fd82ed93dbe4d049eacba310de7eb2a6a.zip | |
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.c | 2 |
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 |