diff options
| author | Jens Axboe <axboe@kernel.dk> | 2022-03-11 10:21:43 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-03-11 11:08:21 -0700 |
| commit | 5b2050718d095cd3242d1f42aaaea3a2fec8e6f0 (patch) | |
| tree | 43433e92bb2218962ec85c17df2c2ba8b093aebf /block/blk-merge.c | |
| parent | 5ca7546fe317bd181ad55f623f6e522069c2e426 (diff) | |
block: ensure plug merging checks the correct queue at least once
Song reports that a RAID rebuild workload runs much slower recently,
and it is seeing a lot less merging than it did previously. The reason
is that a previous commit reduced the amount of work we do for plug
merging. RAID rebuild interleaves requests between disks, so a last-entry
check in plug merging always misses a merge opportunity since we always
find a different disk than what we are looking for.
Modify the logic such that it's still a one-hit cache, but ensure that
we check enough to find the right target before giving up.
Fixes: d38a9c04c0d5 ("block: only check previous entry for plug merge attempt")
Reported-and-tested-by: Song Liu <song@kernel.org>
Reviewed-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-merge.c')
| -rw-r--r-- | block/blk-merge.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c index f5255991b773..8d8177f71ebd 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -1087,12 +1087,20 @@ 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; + break; + } + + /* + * Only keep iterating plug list for merges if we have multiple + * queues + */ + if (!plug->multiple_queues) + break; } return false; } |