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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 /kernel/trace/blktrace.c
parent621c1f42945e76015c3a585e7a9fe6e71665eba0 (diff)
downloadlinux-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>
Diffstat (limited to 'kernel/trace/blktrace.c')
-rw-r--r--kernel/trace/blktrace.c10
1 files changed, 10 insertions, 0 deletions
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);