RAID arrays check/repair operations benefit a lot from merging requests.
If we only check the previous entry for merge attempt, many merge will be
missed. As a result, significant regression is observed for RAID check
and repair.
Fix this by checking more than just the previous entry when
plug->multiple_queues == true.
This improves the check/repair speed of a 20-HDD raid6 from 19 MB/s to
103 MB/s.
Fixes: d38a9c04c0d5 ("block: only check previous entry for plug merge attempt")
Cc: stable@xxxxxxxxxxxxxxx # v5.16
Reported-by: Larkin Lowrey <llowrey@xxxxxxxxxxxxxxxxx>
Reported-by: Wilson Jonathan <i400sjon@xxxxxxxxx>
Reported-by: Roger Heflin <rogerheflin@xxxxxxxxx>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
---
block/blk-merge.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 4de34a332c9f..57e2075fb2f4 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -1089,12 +1089,14 @@ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
if (!plug || rq_list_empty(plug->mq_list))
return false;
- /* check the previously added entry for a quick merge attempt */
- rq = rq_list_peek(&plug->mq_list);
- if (rq->q == q) {
- if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
- BIO_MERGE_OK)
- return true;
+ rq_list_for_each(&plug->mq_list, rq) {
+ if (rq->q == q) {
+ if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
+ BIO_MERGE_OK)
+ return true;
+ }
+ if (!plug->multiple_queues)
+ break;
}
return false;
}
--
2.30.2
