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11#include "dm.h"
12#include "dm-path-selector.h"
13
14#include <linux/slab.h>
15#include <linux/module.h>
16
17#define DM_MSG_PREFIX "multipath service-time"
18#define ST_MIN_IO 1
19#define ST_MAX_RELATIVE_THROUGHPUT 100
20#define ST_MAX_RELATIVE_THROUGHPUT_SHIFT 7
21#define ST_MAX_INFLIGHT_SIZE ((size_t)-1 >> ST_MAX_RELATIVE_THROUGHPUT_SHIFT)
22#define ST_VERSION "0.2.0"
23
24struct selector {
25 struct list_head valid_paths;
26 struct list_head failed_paths;
27};
28
29struct path_info {
30 struct list_head list;
31 struct dm_path *path;
32 unsigned repeat_count;
33 unsigned relative_throughput;
34 atomic_t in_flight_size;
35};
36
37static struct selector *alloc_selector(void)
38{
39 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
40
41 if (s) {
42 INIT_LIST_HEAD(&s->valid_paths);
43 INIT_LIST_HEAD(&s->failed_paths);
44 }
45
46 return s;
47}
48
49static int st_create(struct path_selector *ps, unsigned argc, char **argv)
50{
51 struct selector *s = alloc_selector();
52
53 if (!s)
54 return -ENOMEM;
55
56 ps->context = s;
57 return 0;
58}
59
60static void free_paths(struct list_head *paths)
61{
62 struct path_info *pi, *next;
63
64 list_for_each_entry_safe(pi, next, paths, list) {
65 list_del(&pi->list);
66 kfree(pi);
67 }
68}
69
70static void st_destroy(struct path_selector *ps)
71{
72 struct selector *s = ps->context;
73
74 free_paths(&s->valid_paths);
75 free_paths(&s->failed_paths);
76 kfree(s);
77 ps->context = NULL;
78}
79
80static int st_status(struct path_selector *ps, struct dm_path *path,
81 status_type_t type, char *result, unsigned maxlen)
82{
83 unsigned sz = 0;
84 struct path_info *pi;
85
86 if (!path)
87 DMEMIT("0 ");
88 else {
89 pi = path->pscontext;
90
91 switch (type) {
92 case STATUSTYPE_INFO:
93 DMEMIT("%d %u ", atomic_read(&pi->in_flight_size),
94 pi->relative_throughput);
95 break;
96 case STATUSTYPE_TABLE:
97 DMEMIT("%u %u ", pi->repeat_count,
98 pi->relative_throughput);
99 break;
100 }
101 }
102
103 return sz;
104}
105
106static int st_add_path(struct path_selector *ps, struct dm_path *path,
107 int argc, char **argv, char **error)
108{
109 struct selector *s = ps->context;
110 struct path_info *pi;
111 unsigned repeat_count = ST_MIN_IO;
112 unsigned relative_throughput = 1;
113 char dummy;
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127 if (argc > 2) {
128 *error = "service-time ps: incorrect number of arguments";
129 return -EINVAL;
130 }
131
132 if (argc && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
133 *error = "service-time ps: invalid repeat count";
134 return -EINVAL;
135 }
136
137 if ((argc == 2) &&
138 (sscanf(argv[1], "%u%c", &relative_throughput, &dummy) != 1 ||
139 relative_throughput > ST_MAX_RELATIVE_THROUGHPUT)) {
140 *error = "service-time ps: invalid relative_throughput value";
141 return -EINVAL;
142 }
143
144
145 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
146 if (!pi) {
147 *error = "service-time ps: Error allocating path context";
148 return -ENOMEM;
149 }
150
151 pi->path = path;
152 pi->repeat_count = repeat_count;
153 pi->relative_throughput = relative_throughput;
154 atomic_set(&pi->in_flight_size, 0);
155
156 path->pscontext = pi;
157
158 list_add_tail(&pi->list, &s->valid_paths);
159
160 return 0;
161}
162
163static void st_fail_path(struct path_selector *ps, struct dm_path *path)
164{
165 struct selector *s = ps->context;
166 struct path_info *pi = path->pscontext;
167
168 list_move(&pi->list, &s->failed_paths);
169}
170
171static int st_reinstate_path(struct path_selector *ps, struct dm_path *path)
172{
173 struct selector *s = ps->context;
174 struct path_info *pi = path->pscontext;
175
176 list_move_tail(&pi->list, &s->valid_paths);
177
178 return 0;
179}
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196static int st_compare_load(struct path_info *pi1, struct path_info *pi2,
197 size_t incoming)
198{
199 size_t sz1, sz2, st1, st2;
200
201 sz1 = atomic_read(&pi1->in_flight_size);
202 sz2 = atomic_read(&pi2->in_flight_size);
203
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207 if (pi1->relative_throughput == pi2->relative_throughput)
208 return sz1 - sz2;
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213
214 if (sz1 == sz2 ||
215 !pi1->relative_throughput || !pi2->relative_throughput)
216 return pi2->relative_throughput - pi1->relative_throughput;
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235 sz1 += incoming;
236 sz2 += incoming;
237 if (unlikely(sz1 >= ST_MAX_INFLIGHT_SIZE ||
238 sz2 >= ST_MAX_INFLIGHT_SIZE)) {
239
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244 sz1 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
245 sz2 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
246 }
247 st1 = sz1 * pi2->relative_throughput;
248 st2 = sz2 * pi1->relative_throughput;
249 if (st1 != st2)
250 return st1 - st2;
251
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255 return pi2->relative_throughput - pi1->relative_throughput;
256}
257
258static struct dm_path *st_select_path(struct path_selector *ps,
259 unsigned *repeat_count, size_t nr_bytes)
260{
261 struct selector *s = ps->context;
262 struct path_info *pi = NULL, *best = NULL;
263
264 if (list_empty(&s->valid_paths))
265 return NULL;
266
267
268 list_move_tail(s->valid_paths.next, &s->valid_paths);
269
270 list_for_each_entry(pi, &s->valid_paths, list)
271 if (!best || (st_compare_load(pi, best, nr_bytes) < 0))
272 best = pi;
273
274 if (!best)
275 return NULL;
276
277 *repeat_count = best->repeat_count;
278
279 return best->path;
280}
281
282static int st_start_io(struct path_selector *ps, struct dm_path *path,
283 size_t nr_bytes)
284{
285 struct path_info *pi = path->pscontext;
286
287 atomic_add(nr_bytes, &pi->in_flight_size);
288
289 return 0;
290}
291
292static int st_end_io(struct path_selector *ps, struct dm_path *path,
293 size_t nr_bytes)
294{
295 struct path_info *pi = path->pscontext;
296
297 atomic_sub(nr_bytes, &pi->in_flight_size);
298
299 return 0;
300}
301
302static struct path_selector_type st_ps = {
303 .name = "service-time",
304 .module = THIS_MODULE,
305 .table_args = 2,
306 .info_args = 2,
307 .create = st_create,
308 .destroy = st_destroy,
309 .status = st_status,
310 .add_path = st_add_path,
311 .fail_path = st_fail_path,
312 .reinstate_path = st_reinstate_path,
313 .select_path = st_select_path,
314 .start_io = st_start_io,
315 .end_io = st_end_io,
316};
317
318static int __init dm_st_init(void)
319{
320 int r = dm_register_path_selector(&st_ps);
321
322 if (r < 0)
323 DMERR("register failed %d", r);
324
325 DMINFO("version " ST_VERSION " loaded");
326
327 return r;
328}
329
330static void __exit dm_st_exit(void)
331{
332 int r = dm_unregister_path_selector(&st_ps);
333
334 if (r < 0)
335 DMERR("unregister failed %d", r);
336}
337
338module_init(dm_st_init);
339module_exit(dm_st_exit);
340
341MODULE_DESCRIPTION(DM_NAME " throughput oriented path selector");
342MODULE_AUTHOR("Kiyoshi Ueda <k-ueda@ct.jp.nec.com>");
343MODULE_LICENSE("GPL");
344