Move description text
[fio.git] / engines / skeleton_external.c
CommitLineData
da51c050
JA
1/*
2 * Skeleton for a sample external io engine
3 *
4 * Should be compiled with:
5 *
6 * gcc -Wall -O2 -g -shared -rdynamic -fPIC -o engine.o engine.c
7 *
8 */
9#include <stdio.h>
10#include <stdlib.h>
11#include <unistd.h>
12#include <errno.h>
13#include <assert.h>
14
15#include "../fio.h"
16#include "../os.h"
17
18/*
19 * The core of the module is identical to the ones included with fio,
20 * read those. You cannot use register_ioengine() and unregister_ioengine()
21 * for external modules, they should be gotten through dlsym()
22 */
23
830a78b0
JA
24/*
25 * The ->event() hook is called to match an event number with an io_u.
26 * After the core has called ->getevents() and it has returned eg 3,
27 * the ->event() hook must return the 3 events that have completed for
28 * subsequent calls to ->event() with [0-2]. Required.
29 */
30static struct io_u *fio_skeleton_event(struct thread_data *td, int event)
31{
32 return NULL;
33}
34
35/*
36 * The ->getevents() hook is used to reap completion events from an async
37 * io engine. It returns the number of completed events since the last call,
38 * which may then be retrieved by calling the ->event() hook with the event
39 * numbers. Required.
40 */
41static int fio_skeleton_getevents(struct thread_data *td, int min, int max,
42 struct timespec *t)
43{
44 return 0;
45}
46
47/*
48 * The ->cancel() hook attempts to cancel the io_u. Only relevant for
49 * async io engines, and need not be supported.
50 */
51static int fio_skeleton_cancel(struct thread_data *td, struct io_u *io_u)
52{
53 return 0;
54}
55
56/*
57 * The ->queue() hook is responsible for initiating io on the io_u
58 * being passed in. If the io engine is a synchronous one, io may complete
59 * before ->queue() returns. Required.
e2a26d2c
JA
60 *
61 * The io engine must transfer in the direction noted by io_u->ddir
62 * to the buffer pointed to by io_u->xfer_buf for as many bytes as
63 * io_u->xfer_buflen. Residual data count may be set in io_u->residual
36167d82 64 * for a short read/write.
830a78b0
JA
65 */
66static int fio_skeleton_queue(struct thread_data *td, struct io_u *io_u)
67{
36167d82
JA
68 /*
69 * Could return FIO_Q_QUEUED for a queued request,
70 * FIO_Q_COMPLETED for a completed request, and FIO_Q_BUSY
71 * if we could queue no more at this point (you'd have to
72 * define ->commit() to handle that.
73 */
74 return FIO_Q_COMPLETED;
830a78b0
JA
75}
76
77/*
78 * The ->prep() function is called for each io_u prior to being submitted
79 * with ->queue(). This hook allows the io engine to perform any
34403fb1 80 * preparatory actions on the io_u, before being submitted. Not required.
830a78b0
JA
81 */
82static int fio_skeleton_prep(struct thread_data *td, struct io_u *io_u)
83{
84 return 0;
85}
86
87/*
88 * The init function is called once per thread/process, and should set up
89 * any structures that this io engine requires to keep track of io. Not
90 * required.
91 */
92static int fio_skeleton_init(struct thread_data *td)
93{
94 return 0;
95}
96
97/*
98 * This is paired with the ->init() funtion and is called when a thread is
99 * done doing io. Should tear down anything setup by the ->init() function.
100 * Not required.
101 */
102static void fio_skeleton_cleanup(struct thread_data *td)
103{
104}
105
da51c050
JA
106/*
107 * Note that the structure is exported, so that fio can get it via
108 * dlsym(..., "ioengine");
109 */
110struct ioengine_ops ioengine = {
111 .name = "engine_name",
112 .version = FIO_IOOPS_VERSION,
113 .init = fio_skeleton_init,
114 .prep = fio_skeleton_prep,
115 .queue = fio_skeleton_queue,
830a78b0 116 .cancel = fio_skeleton_cancel,
da51c050
JA
117 .getevents = fio_skeleton_getevents,
118 .event = fio_skeleton_event,
119 .cleanup = fio_skeleton_cleanup,
120};