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| author | Steven Feng <steven@joint-cloud.com> | 2026-06-06 10:42:18 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-06-08 07:46:58 -0600 |
| commit | 7ed4aab1381f3439f45032eb860f89d9da5e45c2 (patch) | |
| tree | b17f538f43cbde894c5c8dc0b79a4b7be7bbd1c1 /block | |
| parent | 5ef1b0194b382fafe5023b5b014e4db3b948ee15 (diff) | |
| download | linux-7ed4aab1381f3439f45032eb860f89d9da5e45c2.tar.gz linux-7ed4aab1381f3439f45032eb860f89d9da5e45c2.zip | |
block: optimize I/O merge hot path with unlikely() hints
Remove redundant '== false' comparisons and add unlikely() branch
prediction hints in block I/O merge path functions.
These functions (ll_new_hw_segment, ll_merge_requests_fn, and
blk_rq_merge_ok) are executed on every I/O request merge attempt,
making them critical hot paths. Data integrity check failures are
rare events, so marking these conditions as unlikely() helps the
CPU optimize the common case by improving branch prediction.
Changes:
- Replace 'func() == false' with 'unlikely(!func())' for better
code style and branch prediction
This micro-optimization reduces branch misprediction penalties in
high-frequency I/O merge paths.
Signed-off-by: Steven Feng <steven@joint-cloud.com>
Link: https://patch.msgid.link/tencent_79B652BD0CC23E093F27914380F161E7E505@qq.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-merge.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c index 7cc82a7a6f4e..ee1d9213f43e 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -545,7 +545,7 @@ static inline int ll_new_hw_segment(struct request *req, struct bio *bio, if (!blk_cgroup_mergeable(req, bio)) goto no_merge; - if (blk_integrity_merge_bio(req->q, req, bio) == false) + if (unlikely(!blk_integrity_merge_bio(req->q, req, bio))) goto no_merge; /* discard request merge won't add new segment */ @@ -647,7 +647,7 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req, if (!blk_cgroup_mergeable(req, next->bio)) return 0; - if (blk_integrity_merge_rq(q, req, next) == false) + if (unlikely(!blk_integrity_merge_rq(q, req, next))) return 0; if (!bio_crypt_ctx_merge_rq(req, next)) @@ -903,7 +903,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) if (!blk_cgroup_mergeable(rq, bio)) return false; - if (blk_integrity_merge_bio(rq->q, rq, bio) == false) + if (unlikely(!blk_integrity_merge_bio(rq->q, rq, bio))) return false; if (!bio_crypt_rq_ctx_compatible(rq, bio)) return false; @@ -913,7 +913,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) return false; if (rq->bio->bi_ioprio != bio->bi_ioprio) return false; - if (blk_atomic_write_mergeable_rq_bio(rq, bio) == false) + if (unlikely(!blk_atomic_write_mergeable_rq_bio(rq, bio))) return false; return true; |