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block: blk-rq-qos: guard rq-qos helpers by static key

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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 <kch@nvidia.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2025-04-15 08:49:35 -06:00
parent 9b79f86e06
commit 033b667a82
2 changed files with 16 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
block/blk-rq-qos.c
View File

@ -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);

21
block/blk-rq-qos.h
View File

@ -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);
}