1 #ifndef _LINUX_ELEVATOR_H
2 #define _LINUX_ELEVATOR_H
6 typedef void (elevator_fn
) (struct request
*, elevator_t
*,
8 struct list_head
*, int);
10 typedef int (elevator_merge_fn
) (request_queue_t
*, struct request
**,
11 struct buffer_head
*, int, int *, int *);
13 typedef void (elevator_dequeue_fn
) (struct request
*);
21 int max_bomb_segments
;
23 unsigned int nr_segments
;
26 elevator_fn
* elevator_fn
;
27 elevator_merge_fn
*elevator_merge_fn
;
28 elevator_dequeue_fn
*dequeue_fn
;
30 unsigned int queue_ID
;
33 void elevator_noop(struct request
*, elevator_t
*, struct list_head
*, struct list_head
*, int);
34 int elevator_noop_merge(request_queue_t
*, struct request
**, struct buffer_head
*, int, int *, int *);
35 void elevator_noop_dequeue(struct request
*);
36 void elevator_linus(struct request
*, elevator_t
*, struct list_head
*, struct list_head
*, int);
37 int elevator_linus_merge(request_queue_t
*, struct request
**, struct buffer_head
*, int, int *, int *);
39 typedef struct blkelv_ioctl_arg_s
{
43 int max_bomb_segments
;
46 #define BLKELVGET _IOR(0x12,106,sizeof(blkelv_ioctl_arg_t))
47 #define BLKELVSET _IOW(0x12,107,sizeof(blkelv_ioctl_arg_t))
49 extern int blkelvget_ioctl(elevator_t
*, blkelv_ioctl_arg_t
*);
50 extern int blkelvset_ioctl(elevator_t
*, const blkelv_ioctl_arg_t
*);
52 extern void elevator_init(elevator_t
*, elevator_t
);
55 * Return values from elevator merger
57 #define ELEVATOR_NO_MERGE 0
58 #define ELEVATOR_FRONT_MERGE 1
59 #define ELEVATOR_BACK_MERGE 2
62 * This is used in the elevator algorithm. We don't prioritise reads
63 * over writes any more --- although reads are more time-critical than
64 * writes, by treating them equally we increase filesystem throughput.
65 * This turns out to give better overall performance. -- sct
67 #define IN_ORDER(s1,s2) \
68 ((((s1)->rq_dev == (s2)->rq_dev && \
69 (s1)->sector < (s2)->sector)) || \
70 (s1)->rq_dev < (s2)->rq_dev)
72 static inline int elevator_request_latency(elevator_t
* elevator
, int rw
)
76 latency
= elevator
->read_latency
;
78 latency
= elevator
->write_latency
;
83 #define ELEVATOR_NOOP \
87 0, /* read_latency */ \
88 0, /* write_latency */ \
89 0, /* max_bomb_segments */ \
91 0, /* nr_segments */ \
92 0, /* read_pendings */ \
94 elevator_noop, /* elevator_fn */ \
95 elevator_noop_merge, /* elevator_merge_fn */ \
96 elevator_noop_dequeue, /* dequeue_fn */ \
99 #define ELEVATOR_LINUS \
103 1000000, /* read passovers */ \
104 2000000, /* write passovers */ \
105 0, /* max_bomb_segments */ \
110 elevator_linus, /* elevator_fn */ \
111 elevator_linus_merge, /* elevator_merge_fn */ \
112 elevator_noop_dequeue, /* dequeue_fn */ \