timer: cache the minimal value.
[ccan] / ccan / timer / timer.c
1 /* LGPL (v2.1 or any later version) - see LICENSE file for details */
2 #include <ccan/timer/timer.h>
3 #include <ccan/array_size/array_size.h>
4 #include <ccan/ilog/ilog.h>
5 #include <ccan/likely/likely.h>
6 #include <stdlib.h>
7 #include <stdio.h>
8
9 #define PER_LEVEL (1ULL << TIMER_LEVEL_BITS)
10
11 struct timer_level {
12         struct list_head list[PER_LEVEL];
13 };
14
15 static uint64_t time_to_grains(struct timespec ts)
16 {
17         return ts.tv_sec * ((uint64_t)1000000000 / TIMER_GRANULARITY)
18                 + (ts.tv_nsec / TIMER_GRANULARITY);
19 }
20
21 static struct timespec grains_to_time(uint64_t grains)
22 {
23         struct timespec ts;
24
25         ts.tv_sec = grains / (1000000000 / TIMER_GRANULARITY);
26         ts.tv_nsec = (grains % (1000000000 / TIMER_GRANULARITY))
27                 * TIMER_GRANULARITY;
28         return ts;
29 }
30
31 void timers_init(struct timers *timers, struct timespec start)
32 {
33         unsigned int i;
34
35         list_head_init(&timers->far);
36         timers->base = time_to_grains(start);
37         timers->first = -1ULL;
38         for (i = 0; i < ARRAY_SIZE(timers->level); i++)
39                 timers->level[i] = NULL;
40 }
41
42 static unsigned int level_of(const struct timers *timers, uint64_t time)
43 {
44         uint64_t diff;
45
46         /* Level depends how far away it is. */
47         diff = time - timers->base;
48         return ilog64(diff / 2) / TIMER_LEVEL_BITS;
49 }
50
51 static void timer_add_raw(struct timers *timers, struct timer *t)
52 {
53         struct list_head *l;
54         unsigned int level = level_of(timers, t->time);
55
56         if (!timers->level[level])
57                 l = &timers->far;
58         else {
59                 int off = (t->time >> (level*TIMER_LEVEL_BITS)) & (PER_LEVEL-1);
60                 l = &timers->level[level]->list[off];
61         }
62
63         list_add_tail(l, &t->list);
64 }
65
66 void timer_add(struct timers *timers, struct timer *t, struct timespec when)
67 {
68         t->time = time_to_grains(when);
69
70         /* Added in the past?  Treat it as imminent. */
71         if (t->time < timers->base)
72                 t->time = timers->base;
73         if (t->time < timers->first)
74                 timers->first = t->time;
75
76         timer_add_raw(timers, t);
77 }
78
79 /* FIXME: inline */
80 void timer_del(struct timers *timers, struct timer *t)
81 {
82         list_del(&t->list);
83 }
84
85 static void timers_far_get(struct timers *timers,
86                            struct list_head *list,
87                            uint64_t when)
88 {
89         struct timer *i, *next;
90
91         list_for_each_safe(&timers->far, i, next, list) {
92                 if (i->time <= when) {
93                         list_del_from(&timers->far, &i->list);
94                         list_add_tail(list, &i->list);
95                 }
96         }
97 }
98
99 static void add_level(struct timers *timers, unsigned int level)
100 {
101         struct timer_level *l;
102         struct timer *t;
103         unsigned int i;
104         struct list_head from_far;
105
106         l = malloc(sizeof(*l));
107         if (!l)
108                 return;
109
110         for (i = 0; i < ARRAY_SIZE(l->list); i++)
111                 list_head_init(&l->list[i]);
112         timers->level[level] = l;
113
114         list_head_init(&from_far);
115         timers_far_get(timers, &from_far,
116                        timers->base + (1ULL << ((level+1)*TIMER_LEVEL_BITS)) - 1);
117
118         while ((t = list_pop(&from_far, struct timer, list)) != NULL)
119                 timer_add_raw(timers, t);
120 }
121
122 /* Take timers from level and distribute them down one. */
123 static void cascade(struct timers *timers, unsigned int level)
124 {
125         struct timer *i;
126         struct list_head from_far, *list;
127
128         if (level == ARRAY_SIZE(timers->level) || !timers->level[level]) {
129                 list_head_init(&from_far);
130                 timers_far_get(timers, &from_far,
131                                timers->base
132                                + (1ULL << (level*TIMER_LEVEL_BITS))-1);
133                 list = &from_far;
134                 if (level != ARRAY_SIZE(timers->level))
135                         add_level(timers, level);
136         } else {
137                 unsigned src;
138
139                 src = (timers->base >> (level * TIMER_LEVEL_BITS)) % PER_LEVEL;
140                 if (src == 0)
141                         cascade(timers, level + 1);
142                 list = &timers->level[level]->list[src];
143         }
144
145         while ((i = list_pop(list, struct timer, list)) != NULL) {
146                 unsigned dst;
147
148                 assert(i->time >= timers->base);
149                 assert(i->time < (timers->base
150                                   + (1ULL << ((level+1)*TIMER_LEVEL_BITS))));
151
152                 dst = (i->time >> ((level-1)*TIMER_LEVEL_BITS)) % PER_LEVEL;
153                 list_add_tail(&timers->level[level-1]->list[dst], &i->list);
154         }
155 }
156
157 static const struct timer *find_first(const struct list_head *list,
158                                       const struct timer *prev)
159 {
160         struct timer *t;
161
162         list_for_each(list, t, list) {
163                 if (!prev || t->time < prev->time)
164                         prev = t;
165         }
166         return prev;
167 }
168
169 static const struct timer *get_first(const struct timers *timers)
170 {
171         unsigned int level, i, off;
172         bool need_next;
173         uint64_t base;
174         const struct timer *found = NULL;
175         struct list_head *h;
176
177         if (timers->first < timers->base) {
178                 base = timers->base;
179                 level = 0;
180         } else {
181                 /* May not be accurate, due to timer_del / expiry. */
182                 level = level_of(timers, timers->first);
183                 base = timers->first >> (TIMER_LEVEL_BITS * level);
184         }
185
186 next:
187         if (!timers->level[level])
188                 return find_first(&timers->far, NULL);
189
190         need_next = false;
191         off = base % PER_LEVEL;
192         for (i = 0; i < PER_LEVEL; i++) {
193                 h = &timers->level[level]->list[(i+off) % PER_LEVEL];
194
195                 if (!list_empty(h))
196                         break;
197
198                 /* We haven't cascaded yet, so if we wrap, we'll need to
199                  * check next level, too. */
200                 if (i + off == PER_LEVEL)
201                         need_next = true;
202         }
203         if (i == PER_LEVEL) {
204                 level++;
205                 base >>= TIMER_LEVEL_BITS;
206                 goto next;
207         }
208
209         /* Level 0 is exact, so they're all the same. */
210         if (level == 0)
211                 found = list_top(h, struct timer, list);
212         else
213                 found = find_first(h, NULL);
214
215         if (need_next) {
216                 if (!timers->level[level+1]) {
217                         found = find_first(&timers->far, found);
218                 } else {
219                         base >>= TIMER_LEVEL_BITS;
220                         off = base % PER_LEVEL;
221                         h = &timers->level[level+1]->list[off];
222                         found = find_first(h, found);
223                 }
224         }
225         return found;
226 }
227
228 static bool update_first(struct timers *timers)
229 {
230         const struct timer *found = get_first(timers);
231
232         if (!found) {
233                 timers->first = -1ULL;
234                 return false;
235         }
236
237         timers->first = found->time;
238         return true;
239 }
240
241 bool timer_earliest(struct timers *timers, struct timespec *first)
242 {
243         if (!update_first(timers))
244                 return false;
245
246         *first = grains_to_time(timers->first);
247         return true;
248 }
249
250 /* Assume no timers before 'time', cascade down and update base time. */
251 static void timer_fast_forward(struct timers *timers, uint64_t time)
252 {
253         unsigned int level, changed;
254         int need_level = -1;
255         struct list_head list;
256         struct timer *i;
257
258         /* How many bits changed between base and time?
259          * Each time we wrap, we need to empty buckets from above. */
260         if (time == timers->base)
261                 return;
262
263         changed = ilog64_nz(time ^ timers->base);
264         level = (changed - 1) / TIMER_LEVEL_BITS;
265
266         /* Buckets always empty downwards, so we could cascade manually,
267          * but it's rarely very many so we just remove and re-add */
268         list_head_init(&list);
269
270         do {
271                 if (!timers->level[level]) {
272                         /* We need any which belong on this level. */
273                         timers_far_get(timers, &list,
274                                        timers->base
275                                        + (1ULL << ((level+1)*TIMER_LEVEL_BITS))-1);
276                         need_level = level;
277                 } else {
278                         unsigned src;
279
280                         /* Get all timers from this bucket. */
281                         src = (time >> (level * TIMER_LEVEL_BITS)) % PER_LEVEL;
282                         list_append_list(&list,
283                                          &timers->level[level]->list[src]);
284                 }
285         } while (level--);
286
287         /* Did we hit the last level?  If so, add. */
288         if (need_level != -1)
289                 add_level(timers, need_level);
290
291         /* Fast-forward the time, and re-add everyone. */
292         timers->base = time;
293         while ((i = list_pop(&list, struct timer, list)) != NULL)
294                 timer_add_raw(timers, i);
295 }
296
297 /* Fills list of expired timers. */
298 void timers_expire(struct timers *timers,
299                    struct timespec expire,
300                    struct list_head *list)
301 {
302         uint64_t now = time_to_grains(expire);
303         unsigned int off;
304
305         assert(now >= timers->base);
306
307         list_head_init(list);
308
309         if (!timers->level[0]) {
310                 if (list_empty(&timers->far))
311                         return;
312                 add_level(timers, 0);
313         }
314
315         do {
316                 if (timers->first > now) {
317                         timer_fast_forward(timers, now);
318                         break;
319                 }
320
321                 timer_fast_forward(timers, timers->first);
322                 off = timers->base % PER_LEVEL;
323
324                 list_append_list(list, &timers->level[0]->list[off]);
325                 if (timers->base == now)
326                         break;
327         } while (update_first(timers));
328 }
329
330 static bool timer_list_check(const struct list_head *l,
331                              uint64_t min, uint64_t max, uint64_t first,
332                              const char *abortstr)
333 {
334         const struct timer *t;
335
336         if (!list_check(l, abortstr))
337                 return false;
338
339         list_for_each(l, t, list) {
340                 if (t->time < min || t->time > max) {
341                         if (abortstr) {
342                                 fprintf(stderr,
343                                         "%s: timer %p %llu not %llu-%llu\n",
344                                         abortstr, t, t->time, min, max);
345                                 abort();
346                         }
347                         return false;
348                 }
349                 if (t->time < first) {
350                         if (abortstr) {
351                                 fprintf(stderr,
352                                         "%s: timer %p %llu < minimum %llu\n",
353                                         abortstr, t, t->time, first);
354                                 abort();
355                         }
356                         return false;
357                 }
358         }
359         return true;
360 }
361
362 struct timers *timers_check(const struct timers *timers, const char *abortstr)
363 {
364         unsigned int l, i, off;
365         uint64_t base;
366
367         l = 0;
368         if (!timers->level[0])
369                 goto past_levels;
370
371         /* First level is simple. */
372         off = timers->base % PER_LEVEL;
373         for (i = 0; i < PER_LEVEL; i++) {
374                 struct list_head *h;
375
376                 h = &timers->level[l]->list[(i+off) % PER_LEVEL];
377                 if (!timer_list_check(h, timers->base + i, timers->base + i,
378                                       timers->first, abortstr))
379                         return NULL;
380         }
381
382         /* For other levels, "current" bucket has been emptied, and may contain
383          * entries for the current + level_size bucket. */
384         for (l = 1; timers->level[l] && l < PER_LEVEL; l++) {
385                 uint64_t per_bucket = 1ULL << (TIMER_LEVEL_BITS * l);
386
387                 off = ((timers->base >> (l*TIMER_LEVEL_BITS)) % PER_LEVEL);
388                 /* We start at *next* bucket. */
389                 base = (timers->base & ~(per_bucket - 1)) + per_bucket;
390
391                 for (i = 1; i <= PER_LEVEL; i++) {
392                         struct list_head *h;
393
394                         h = &timers->level[l]->list[(i+off) % PER_LEVEL];
395                         if (!timer_list_check(h, base, base + per_bucket - 1,
396                                               timers->first, abortstr))
397                                 return NULL;
398                         base += per_bucket;
399                 }
400         }
401
402 past_levels:
403         base = (timers->base & ~((1ULL << (TIMER_LEVEL_BITS * l)) - 1))
404                 + (1ULL << (TIMER_LEVEL_BITS * l)) - 1;
405         if (!timer_list_check(&timers->far, base, -1ULL, timers->first,
406                               abortstr))
407                 return NULL;
408
409         return (struct timers *)timers;
410 }
411
412 //#ifdef CCAN_TIMER_DEBUG
413 void timers_dump(const struct timers *timers, FILE *fp)
414 {
415         unsigned int l, i;
416         uint64_t min, max, num;
417         struct timer *t;
418
419         if (!fp)
420                 fp = stderr;
421
422         fprintf(fp, "Base: %llu\n", timers->base);
423
424         for (l = 0; timers->level[l] && l < ARRAY_SIZE(timers->level); l++) {
425                 fprintf(fp, "Level %i (+%llu):\n",
426                         l, (uint64_t)1 << (TIMER_LEVEL_BITS * l));
427                 for (i = 0; i < (1 << TIMER_LEVEL_BITS); i++) {
428
429                         if (list_empty(&timers->level[l]->list[i]))
430                                 continue;
431                         min = -1ULL;
432                         max = 0;
433                         num = 0;
434                         list_for_each(&timers->level[l]->list[i], t, list) {
435                                 if (t->time < min)
436                                         min = t->time;
437                                 if (t->time > max)
438                                         max = t->time;
439                                 num++;
440                         }
441                         fprintf(stderr, "  %llu (+%llu-+%llu)\n",
442                                 num, min - timers->base, max - timers->base);
443                 }
444         }
445
446         min = -1ULL;
447         max = 0;
448         num = 0;
449         list_for_each(&timers->far, t, list) {
450                 if (t->time < min)
451                         min = t->time;
452                 if (t->time > max)
453                         max = t->time;
454                 num++;
455         }
456         fprintf(stderr, "Far: %llu (%llu-%llu)\n", num, min, max);
457 }
458 //#endif
459
460 void timers_cleanup(struct timers *timers)
461 {
462         unsigned int l;
463
464         for (l = 0; l < ARRAY_SIZE(timers->level); l++)
465                 free(timers->level[l]);
466 }