diff options
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 | |
parent | 621c1f42945e76015c3a585e7a9fe6e71665eba0 (diff) | |
download | linux-f3bdc62fd82ed93dbe4d049eacba310de7eb2a6a.tar.bz2 |
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>
-rw-r--r-- | block/blk-merge.c | 2 | ||||
-rw-r--r-- | include/trace/events/block.h | 15 | ||||
-rw-r--r-- | kernel/trace/blktrace.c | 10 |
3 files changed, 27 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 diff --git a/include/trace/events/block.h b/include/trace/events/block.h index 93b114226af8..34d64ca306b1 100644 --- a/include/trace/events/block.h +++ b/include/trace/events/block.h @@ -212,6 +212,21 @@ DEFINE_EVENT(block_rq, block_rq_issue, ); /** + * block_rq_merge - merge request with another one in the elevator + * @q: queue holding operation + * @rq: block IO operation operation request + * + * Called when block operation request @rq from queue @q is merged to another + * request queued in the elevator. + */ +DEFINE_EVENT(block_rq, block_rq_merge, + + TP_PROTO(struct request_queue *q, struct request *rq), + + TP_ARGS(q, rq) +); + +/** * block_bio_bounce - used bounce buffer when processing block operation * @q: queue holding the block operation * @bio: block operation diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index c086c38f4954..7ba62d68885a 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -860,6 +860,13 @@ static void blk_add_trace_rq_issue(void *ignore, blk_trace_request_get_cgid(q, rq)); } +static void blk_add_trace_rq_merge(void *ignore, + struct request_queue *q, struct request *rq) +{ + blk_add_trace_rq(rq, 0, blk_rq_bytes(rq), BLK_TA_BACKMERGE, + blk_trace_request_get_cgid(q, rq)); +} + static void blk_add_trace_rq_requeue(void *ignore, struct request_queue *q, struct request *rq) @@ -1144,6 +1151,8 @@ static void blk_register_tracepoints(void) WARN_ON(ret); ret = register_trace_block_rq_issue(blk_add_trace_rq_issue, NULL); WARN_ON(ret); + ret = register_trace_block_rq_merge(blk_add_trace_rq_merge, NULL); + WARN_ON(ret); ret = register_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL); WARN_ON(ret); ret = register_trace_block_rq_complete(blk_add_trace_rq_complete, NULL); @@ -1190,6 +1199,7 @@ static void blk_unregister_tracepoints(void) unregister_trace_block_bio_bounce(blk_add_trace_bio_bounce, NULL); unregister_trace_block_rq_complete(blk_add_trace_rq_complete, NULL); unregister_trace_block_rq_requeue(blk_add_trace_rq_requeue, NULL); + unregister_trace_block_rq_merge(blk_add_trace_rq_merge, NULL); unregister_trace_block_rq_issue(blk_add_trace_rq_issue, NULL); unregister_trace_block_rq_insert(blk_add_trace_rq_insert, NULL); |