I/O Request Scheduling

include/block/sched.h

struct bio_rqueue

Member Type	Member Name
struct list_head	list
uint64_t	request_count
bool	dirty

struct bio_scheduler

Member Type	Member Name
struct generic_disk	*disk
struct spinlock	lock
uint64_t	total_requests
struct bio_rqueue	queues[BIO_SCHED_LEVELS]
bool	defer_pending

struct bio_scheduler_ops

Member Type	Member Name
bool	(*should_coalesce)(struct generic_disk *dev, const struct bio_request *a, const struct bio_request *b)
void	(*do_coalesce)(struct generic_disk *dev, struct bio_request *into, struct bio_request *from)
void	(*reorder)(struct generic_disk *dev)
uint32_t	max_wait_time[BIO_SCHED_LEVELS]
uint32_t	dispatch_threshold
uint64_t	boost_occupance_limit[BIO_SCHED_LEVELS]
uint64_t	tick_ms
uint64_t	min_wait_ms

• bool noop_should_coalesce(struct generic_disk *disk,struct bio_request *a,struct bio_request *b)
• void noop_do_coalesce(struct generic_disk *disk,struct bio_request *into,struct bio_request *from)
• void noop_reorder(struct generic_disk *disk)
• void bio_sched_enqueue(struct generic_disk *disk,struct bio_request *req)
• void bio_sched_dequeue(struct generic_disk *disk,struct bio_request *req,bool already_locked)
• void bio_sched_enqueue_internal(struct bio_scheduler *sched,struct bio_request *req)
• void bio_sched_dequeue_internal(struct bio_scheduler *sched,struct bio_request *req)
• void bio_sched_dispatch_partial(struct generic_disk *disk,enum bio_request_priority prio)
• void bio_sched_dispatch_all(struct generic_disk *disk)
• void bio_sched_try_early_dispatch(struct bio_scheduler *sched)
• bool bio_sched_try_coalesce(struct bio_scheduler *sched)
• bool bio_sched_boost_starved(struct bio_scheduler *sched)
• struct bio_scheduler *bio_sched_create(struct generic_disk *disk,struct bio_scheduler_ops *ops)
• static inline void update_request_timestamp(struct bio_request *req)
• static inline bool submit_if_urgent(struct bio_scheduler *sched,struct bio_request *req)
• static inline bool sched_is_empty(struct bio_scheduler *sched)
• static inline bool submit_if_skip_sched(struct bio_scheduler *sched,struct bio_request *req)

Defines

• BIO_SCHED_LEVELS: 5
• BIO_SCHED_MAX: (BIO_SCHED_LEVELS - 1)
• BIO_SCHED_STARVATION_BOOST: 1
• BIO_SCHED_BOOST_SHIFT_LIMIT: 4
• BIO_SCHED_COALESCE_SCAN_LIMIT: 8
• BIO_SCHED_MAX_BOOST_SCAN: 32
• BIO_SCHED_MAX_COALESCES: 4

---