git.ozlabs.org Git - ccan/blob - 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 static const struct timer *find_first(const struct list_head *list,
 123                                       const struct timer *prev)
 124 {
 125         struct timer *t;
 126
 127         list_for_each(list, t, list) {
 128                 if (!prev || t->time < prev->time)
 129                         prev = t;
 130         }
 131         return prev;
 132 }
 133
 134 static const struct timer *get_first(const struct timers *timers)
 135 {
 136         unsigned int level, i, off;
 137         bool need_next;
 138         uint64_t base;
 139         const struct timer *found = NULL;
 140         struct list_head *h;
 141
 142         if (timers->first < timers->base) {
 143                 base = timers->base;
 144                 level = 0;
 145         } else {
 146                 /* May not be accurate, due to timer_del / expiry. */
 147                 level = level_of(timers, timers->first);
 148                 base = timers->first >> (TIMER_LEVEL_BITS * level);
 149         }
 150
 151 next:
 152         if (!timers->level[level])
 153                 return find_first(&timers->far, NULL);
 154
 155         need_next = false;
 156         off = base % PER_LEVEL;
 157         for (i = 0; i < PER_LEVEL; i++) {
 158                 h = &timers->level[level]->list[(i+off) % PER_LEVEL];
 159
 160                 if (!list_empty(h))
 161                         break;
 162
 163                 /* We haven't cascaded yet, so if we wrap, we'll need to
 164                  * check next level, too. */
 165                 if (i + off == PER_LEVEL)
 166                         need_next = true;
 167         }
 168         if (i == PER_LEVEL) {
 169                 level++;
 170                 base >>= TIMER_LEVEL_BITS;
 171                 goto next;
 172         }
 173
 174         /* Level 0 is exact, so they're all the same. */
 175         if (level == 0)
 176                 found = list_top(h, struct timer, list);
 177         else
 178                 found = find_first(h, NULL);
 179
 180         if (need_next) {
 181                 if (!timers->level[level+1]) {
 182                         found = find_first(&timers->far, found);
 183                 } else {
 184                         base >>= TIMER_LEVEL_BITS;
 185                         off = base % PER_LEVEL;
 186                         h = &timers->level[level+1]->list[off];
 187                         found = find_first(h, found);
 188                 }
 189         }
 190         return found;
 191 }
 192
 193 static bool update_first(struct timers *timers)
 194 {
 195         const struct timer *found = get_first(timers);
 196
 197         if (!found) {
 198                 timers->first = -1ULL;
 199                 return false;
 200         }
 201
 202         timers->first = found->time;
 203         return true;
 204 }
 205
 206 bool timer_earliest(struct timers *timers, struct timespec *first)
 207 {
 208         if (!update_first(timers))
 209                 return false;
 210
 211         *first = grains_to_time(timers->first);
 212         return true;
 213 }
 214
 215 /* Assume no timers before 'time', cascade down and update base time. */
 216 static void timer_fast_forward(struct timers *timers, uint64_t time)
 217 {
 218         unsigned int level, changed;
 219         int need_level = -1;
 220         struct list_head list;
 221         struct timer *i;
 222
 223         /* How many bits changed between base and time?
 224          * Each time we wrap, we need to empty buckets from above. */
 225         if (time == timers->base)
 226                 return;
 227
 228         changed = ilog64_nz(time ^ timers->base);
 229         level = (changed - 1) / TIMER_LEVEL_BITS;
 230
 231         /* Buckets always empty downwards, so we could cascade manually,
 232          * but it's rarely very many so we just remove and re-add */
 233         list_head_init(&list);
 234
 235         do {
 236                 if (!timers->level[level]) {
 237                         /* We need any which belong on this level. */
 238                         timers_far_get(timers, &list,
 239                                        timers->base
 240                                        + (1ULL << ((level+1)*TIMER_LEVEL_BITS))-1);
 241                         need_level = level;
 242                 } else {
 243                         unsigned src;
 244
 245                         /* Get all timers from this bucket. */
 246                         src = (time >> (level * TIMER_LEVEL_BITS)) % PER_LEVEL;
 247                         list_append_list(&list,
 248                                          &timers->level[level]->list[src]);
 249                 }
 250         } while (level--);
 251
 252         /* Did we hit the last level?  If so, add. */
 253         if (need_level != -1)
 254                 add_level(timers, need_level);
 255
 256         /* Fast-forward the time, and re-add everyone. */
 257         timers->base = time;
 258         while ((i = list_pop(&list, struct timer, list)) != NULL)
 259                 timer_add_raw(timers, i);
 260 }
 261
 262 /* Fills list of expired timers. */
 263 void timers_expire(struct timers *timers,
 264                    struct timespec expire,
 265                    struct list_head *list)
 266 {
 267         uint64_t now = time_to_grains(expire);
 268         unsigned int off;
 269
 270         assert(now >= timers->base);
 271
 272         list_head_init(list);
 273
 274         if (!timers->level[0]) {
 275                 if (list_empty(&timers->far))
 276                         return;
 277                 add_level(timers, 0);
 278         }
 279
 280         do {
 281                 if (timers->first > now) {
 282                         timer_fast_forward(timers, now);
 283                         break;
 284                 }
 285
 286                 timer_fast_forward(timers, timers->first);
 287                 off = timers->base % PER_LEVEL;
 288
 289                 list_append_list(list, &timers->level[0]->list[off]);
 290                 if (timers->base == now)
 291                         break;
 292         } while (update_first(timers));
 293 }
 294
 295 static bool timer_list_check(const struct list_head *l,
 296                              uint64_t min, uint64_t max, uint64_t first,
 297                              const char *abortstr)
 298 {
 299         const struct timer *t;
 300
 301         if (!list_check(l, abortstr))
 302                 return false;
 303
 304         list_for_each(l, t, list) {
 305                 if (t->time < min || t->time > max) {
 306                         if (abortstr) {
 307                                 fprintf(stderr,
 308                                         "%s: timer %p %llu not %llu-%llu\n",
 309                                         abortstr, t, t->time, min, max);
 310                                 abort();
 311                         }
 312                         return false;
 313                 }
 314                 if (t->time < first) {
 315                         if (abortstr) {
 316                                 fprintf(stderr,
 317                                         "%s: timer %p %llu < minimum %llu\n",
 318                                         abortstr, t, t->time, first);
 319                                 abort();
 320                         }
 321                         return false;
 322                 }
 323         }
 324         return true;
 325 }
 326
 327 struct timers *timers_check(const struct timers *timers, const char *abortstr)
 328 {
 329         unsigned int l, i, off;
 330         uint64_t base;
 331
 332         l = 0;
 333         if (!timers->level[0])
 334                 goto past_levels;
 335
 336         /* First level is simple. */
 337         off = timers->base % PER_LEVEL;
 338         for (i = 0; i < PER_LEVEL; i++) {
 339                 struct list_head *h;
 340
 341                 h = &timers->level[l]->list[(i+off) % PER_LEVEL];
 342                 if (!timer_list_check(h, timers->base + i, timers->base + i,
 343                                       timers->first, abortstr))
 344                         return NULL;
 345         }
 346
 347         /* For other levels, "current" bucket has been emptied, and may contain
 348          * entries for the current + level_size bucket. */
 349         for (l = 1; timers->level[l] && l < PER_LEVEL; l++) {
 350                 uint64_t per_bucket = 1ULL << (TIMER_LEVEL_BITS * l);
 351
 352                 off = ((timers->base >> (l*TIMER_LEVEL_BITS)) % PER_LEVEL);
 353                 /* We start at *next* bucket. */
 354                 base = (timers->base & ~(per_bucket - 1)) + per_bucket;
 355
 356                 for (i = 1; i <= PER_LEVEL; i++) {
 357                         struct list_head *h;
 358
 359                         h = &timers->level[l]->list[(i+off) % PER_LEVEL];
 360                         if (!timer_list_check(h, base, base + per_bucket - 1,
 361                                               timers->first, abortstr))
 362                                 return NULL;
 363                         base += per_bucket;
 364                 }
 365         }
 366
 367 past_levels:
 368         base = (timers->base & ~((1ULL << (TIMER_LEVEL_BITS * l)) - 1))
 369                 + (1ULL << (TIMER_LEVEL_BITS * l)) - 1;
 370         if (!timer_list_check(&timers->far, base, -1ULL, timers->first,
 371                               abortstr))
 372                 return NULL;
 373
 374         return (struct timers *)timers;
 375 }
 376
 377 #ifdef CCAN_TIMER_DEBUG
 378 void timers_dump(const struct timers *timers, FILE *fp)
 379 {
 380         unsigned int l, i;
 381         uint64_t min, max, num;
 382         struct timer *t;
 383
 384         if (!fp)
 385                 fp = stderr;
 386
 387         fprintf(fp, "Base: %llu\n", timers->base);
 388
 389         for (l = 0; timers->level[l] && l < ARRAY_SIZE(timers->level); l++) {
 390                 fprintf(fp, "Level %i (+%llu):\n",
 391                         l, (uint64_t)1 << (TIMER_LEVEL_BITS * l));
 392                 for (i = 0; i < (1 << TIMER_LEVEL_BITS); i++) {
 393
 394                         if (list_empty(&timers->level[l]->list[i]))
 395                                 continue;
 396                         min = -1ULL;
 397                         max = 0;
 398                         num = 0;
 399                         list_for_each(&timers->level[l]->list[i], t, list) {
 400                                 if (t->time < min)
 401                                         min = t->time;
 402                                 if (t->time > max)
 403                                         max = t->time;
 404                                 num++;
 405                         }
 406                         fprintf(stderr, "  %llu (+%llu-+%llu)\n",
 407                                 num, min - timers->base, max - timers->base);
 408                 }
 409         }
 410
 411         min = -1ULL;
 412         max = 0;
 413         num = 0;
 414         list_for_each(&timers->far, t, list) {
 415                 if (t->time < min)
 416                         min = t->time;
 417                 if (t->time > max)
 418                         max = t->time;
 419                 num++;
 420         }
 421         fprintf(stderr, "Far: %llu (%llu-%llu)\n", num, min, max);
 422 }
 423 #endif
 424
 425 void timers_cleanup(struct timers *timers)
 426 {
 427         unsigned int l;
 428
 429         for (l = 0; l < ARRAY_SIZE(timers->level); l++)
 430                 free(timers->level[l]);
 431 }