From 033b667a823ee403509e7156bc7fa335bd566bff Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 15 Apr 2025 08:49:35 -0600 Subject: [PATCH] block: blk-rq-qos: guard rq-qos helpers by static key Even if blk-rq-qos isn't used or configured, dipping into the queue to fetch ->rq_qos is a noticeable slowdown and visible in profiles. Add an unlikely static key around blk-rq-qos, to avoid fetching this cacheline if blk-iolatency or blk-wbt isn't configured or used. Reviewed-by: Chaitanya Kulkarni Signed-off-by: Jens Axboe --- block/blk-rq-qos.c | 4 ++++ block/blk-rq-qos.h | 21 ++++++++++++--------- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c index 95982bc46ba1..848591fb3c57 100644 --- a/block/blk-rq-qos.c +++ b/block/blk-rq-qos.c @@ -2,6 +2,8 @@ #include "blk-rq-qos.h" +__read_mostly DEFINE_STATIC_KEY_FALSE(block_rq_qos); + /* * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded, * false if 'v' + 1 would be bigger than 'below'. @@ -317,6 +319,7 @@ void rq_qos_exit(struct request_queue *q) struct rq_qos *rqos = q->rq_qos; q->rq_qos = rqos->next; rqos->ops->exit(rqos); + static_branch_dec(&block_rq_qos); } mutex_unlock(&q->rq_qos_mutex); } @@ -343,6 +346,7 @@ int rq_qos_add(struct rq_qos *rqos, struct gendisk *disk, enum rq_qos_id id, goto ebusy; rqos->next = q->rq_qos; q->rq_qos = rqos; + static_branch_inc(&block_rq_qos); blk_mq_unfreeze_queue(q, memflags); diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h index 37245c97ee61..39749f4066fb 100644 --- a/block/blk-rq-qos.h +++ b/block/blk-rq-qos.h @@ -12,6 +12,7 @@ #include "blk-mq-debugfs.h" struct blk_mq_debugfs_attr; +extern struct static_key_false block_rq_qos; enum rq_qos_id { RQ_QOS_WBT, @@ -112,31 +113,33 @@ void __rq_qos_queue_depth_changed(struct rq_qos *rqos); static inline void rq_qos_cleanup(struct request_queue *q, struct bio *bio) { - if (q->rq_qos) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) __rq_qos_cleanup(q->rq_qos, bio); } static inline void rq_qos_done(struct request_queue *q, struct request *rq) { - if (q->rq_qos && !blk_rq_is_passthrough(rq)) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos && + !blk_rq_is_passthrough(rq)) __rq_qos_done(q->rq_qos, rq); } static inline void rq_qos_issue(struct request_queue *q, struct request *rq) { - if (q->rq_qos) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) __rq_qos_issue(q->rq_qos, rq); } static inline void rq_qos_requeue(struct request_queue *q, struct request *rq) { - if (q->rq_qos) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) __rq_qos_requeue(q->rq_qos, rq); } static inline void rq_qos_done_bio(struct bio *bio) { - if (bio->bi_bdev && (bio_flagged(bio, BIO_QOS_THROTTLED) || + if (static_branch_unlikely(&block_rq_qos) && + bio->bi_bdev && (bio_flagged(bio, BIO_QOS_THROTTLED) || bio_flagged(bio, BIO_QOS_MERGED))) { struct request_queue *q = bdev_get_queue(bio->bi_bdev); if (q->rq_qos) @@ -146,7 +149,7 @@ static inline void rq_qos_done_bio(struct bio *bio) static inline void rq_qos_throttle(struct request_queue *q, struct bio *bio) { - if (q->rq_qos) { + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) { bio_set_flag(bio, BIO_QOS_THROTTLED); __rq_qos_throttle(q->rq_qos, bio); } @@ -155,14 +158,14 @@ static inline void rq_qos_throttle(struct request_queue *q, struct bio *bio) static inline void rq_qos_track(struct request_queue *q, struct request *rq, struct bio *bio) { - if (q->rq_qos) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) __rq_qos_track(q->rq_qos, rq, bio); } static inline void rq_qos_merge(struct request_queue *q, struct request *rq, struct bio *bio) { - if (q->rq_qos) { + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) { bio_set_flag(bio, BIO_QOS_MERGED); __rq_qos_merge(q->rq_qos, rq, bio); } @@ -170,7 +173,7 @@ static inline void rq_qos_merge(struct request_queue *q, struct request *rq, static inline void rq_qos_queue_depth_changed(struct request_queue *q) { - if (q->rq_qos) + if (static_branch_unlikely(&block_rq_qos) && q->rq_qos) __rq_qos_queue_depth_changed(q->rq_qos); } -- 2.49.0