summaryrefslogtreecommitdiffstats
path: root/src/vppinfra/timing_wheel.c
blob: 830888a19c11862505e66d22f74868441c7534ff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
/*
 * Copyright (c) 2015 Cisco and/or its affiliates.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include <vppinfra/bitmap.h>
#include <vppinfra/hash.h>
#include <vppinfra/pool.h>
#include <vppinfra/timing_wheel.h>

void
timing_wheel_init (timing_wheel_t * w, u64 current_cpu_time,
		   f64 cpu_clocks_per_second)
{
  if (w->max_sched_time <= w->min_sched_time)
    {
      w->min_sched_time = 1e-6;
      w->max_sched_time = 1e-3;
    }

  w->cpu_clocks_per_second = cpu_clocks_per_second;
  w->log2_clocks_per_bin =
    max_log2 (w->cpu_clocks_per_second * w->min_sched_time);
  w->log2_bins_per_wheel =
    max_log2 (w->cpu_clocks_per_second * w->max_sched_time);
  w->log2_bins_per_wheel -= w->log2_clocks_per_bin;
  w->log2_clocks_per_wheel = w->log2_bins_per_wheel + w->log2_clocks_per_bin;
  w->bins_per_wheel = 1 << w->log2_bins_per_wheel;
  w->bins_per_wheel_mask = w->bins_per_wheel - 1;

  w->current_time_index = current_cpu_time >> w->log2_clocks_per_bin;

  if (w->n_wheel_elt_time_bits <= 0 ||
      w->n_wheel_elt_time_bits >= STRUCT_BITS_OF (timing_wheel_elt_t,
						  cpu_time_relative_to_base))
    w->n_wheel_elt_time_bits =
      STRUCT_BITS_OF (timing_wheel_elt_t, cpu_time_relative_to_base) - 1;

  w->cpu_time_base = current_cpu_time;
  w->time_index_next_cpu_time_base_update
    =
    w->current_time_index +
    ((u64) 1 << (w->n_wheel_elt_time_bits - w->log2_clocks_per_bin));
}

always_inline uword
get_level_and_relative_time (timing_wheel_t * w, u64 cpu_time,
			     uword * rtime_result)
{
  u64 dt, rtime;
  uword level_index;

  dt = (cpu_time >> w->log2_clocks_per_bin);

  /* Time should always move forward. */
  ASSERT (dt >= w->current_time_index);

  dt -= w->current_time_index;

  /* Find level and offset within level.  Level i has bins of size 2^((i+1)*M) */
  rtime = dt;
  for (level_index = 0; (rtime >> w->log2_bins_per_wheel) != 0; level_index++)
    rtime = (rtime >> w->log2_bins_per_wheel) - 1;

  /* Return offset within level and level index. */
  ASSERT (rtime < w->bins_per_wheel);
  *rtime_result = rtime;
  return level_index;
}

always_inline uword
time_index_to_wheel_index (timing_wheel_t * w, uword level_index, u64 ti)
{
  return (ti >> (level_index * w->log2_bins_per_wheel)) &
    w->bins_per_wheel_mask;
}

/* Find current time on this level. */
always_inline uword
current_time_wheel_index (timing_wheel_t * w, uword level_index)
{
  return time_index_to_wheel_index (w, level_index, w->current_time_index);
}

/* Circular wheel indexing. */
always_inline uword
wheel_add (timing_wheel_t * w, word x)
{
  return x & w->bins_per_wheel_mask;
}

always_inline uword
rtime_to_wheel_index (timing_wheel_t * w, uword level_index, uword rtime)
{
  uword t = current_time_wheel_index (w, level_index);
  return wheel_add (w, t + rtime);
}

static clib_error_t *
validate_level (timing_wheel_t * w, uword level_index, uword * n_elts)
{
  timing_wheel_level_t *level;
  timing_wheel_elt_t *e;
  uword wi;
  clib_error_t *error = 0;

#define _(x)					\
  do {						\
    error = CLIB_ERROR_ASSERT (x);		\
    ASSERT (! error);				\
    if (error) return error;			\
  } while (0)

  level = vec_elt_at_index (w->levels, level_index);
  for (wi = 0; wi < vec_len (level->elts); wi++)
    {
      /* Validate occupancy bitmap. */
      _(clib_bitmap_get_no_check (level->occupancy_bitmap, wi) ==
	(vec_len (level->elts[wi]) > 0));

      *n_elts += vec_len (level->elts[wi]);

      vec_foreach (e, level->elts[wi])
      {
	/* Validate time bin and level. */
	u64 e_time;
	uword e_ti, e_li, e_wi;

	e_time = e->cpu_time_relative_to_base + w->cpu_time_base;
	e_li = get_level_and_relative_time (w, e_time, &e_ti);
	e_wi = rtime_to_wheel_index (w, level_index, e_ti);

	if (e_li == level_index - 1)
	  /* If this element was scheduled on the previous level
	     it must be wrapped. */
	  _(e_ti + current_time_wheel_index (w, level_index - 1)
	    >= w->bins_per_wheel);
	else
	  {
	    _(e_li == level_index);
	    if (e_li == 0)
	      _(e_wi == wi);
	    else
	      _(e_wi == wi || e_wi + 1 == wi || e_wi - 1 == wi);
	  }
      }
    }

#undef _

  return error;
}

void
timing_wheel_validate (timing_wheel_t * w)
{
  uword l;
  clib_error_t *error = 0;
  uword n_elts;

  if (!w->validate)
    return;

  n_elts = pool_elts (w->overflow_pool);
  for (l = 0; l < vec_len (w->levels); l++)
    {
      error = validate_level (w, l, &n_elts);
      if (error)
	clib_error_report (error);
    }
}

always_inline void
free_elt_vector (timing_wheel_t * w, timing_wheel_elt_t * ev)
{
  /* Poison free elements so we never use them by mistake. */
  if (CLIB_DEBUG > 0)
    clib_memset (ev, ~0, vec_len (ev) * sizeof (ev[0]));
  vec_set_len (ev, 0);
  vec_add1 (w->free_elt_vectors, ev);
}

static timing_wheel_elt_t *
insert_helper (timing_wheel_t * w, uword level_index, uword rtime)
{
  timing_wheel_level_t *level;
  timing_wheel_elt_t *e;
  uword wheel_index;

  /* Circular buffer. */
  vec_validate (w->levels, level_index);
  level = vec_elt_at_index (w->levels, level_index);

  if (PREDICT_FALSE (!level->elts))
    {
      uword max = w->bins_per_wheel - 1;
      clib_bitmap_validate (level->occupancy_bitmap, max);
      vec_validate (level->elts, max);
    }

  wheel_index = rtime_to_wheel_index (w, level_index, rtime);

  level->occupancy_bitmap =
    clib_bitmap_ori (level->occupancy_bitmap, wheel_index);

  /* Allocate an elt vector from free list if there is one. */
  if (!level->elts[wheel_index] && vec_len (w->free_elt_vectors))
    level->elts[wheel_index] = vec_pop (w->free_elt_vectors);

  /* Add element to vector for this time bin. */
  vec_add2 (level->elts[wheel_index], e, 1);

  return e;
}

/* Insert user data on wheel at given CPU time stamp. */
static void
timing_wheel_insert_helper (timing_wheel_t * w, u64 insert_cpu_time,
			    u32 user_data)
{
  timing_wheel_elt_t *e;
  u64 dt;
  uword rtime, level_index;

  level_index = get_level_and_relative_time (w, insert_cpu_time, &rtime);

  dt = insert_cpu_time - w->cpu_time_base;
  if (PREDICT_TRUE (0 == (dt >> BITS (e->cpu_time_relative_to_base))))
    {
      e = insert_helper (w, level_index, rtime);
      e->user_data = user_data;
      e->cpu_time_relative_to_base = dt;
      if (insert_cpu_time < w->cached_min_cpu_time_on_wheel)
	w->cached_min_cpu_time_on_wheel = insert_cpu_time;
    }
  else
    {
      /* Time too far in the future: add to overflow vector. */
      timing_wheel_overflow_elt_t *oe;
      pool_get (w->overflow_pool, oe);
      oe->user_data = user_data;
      oe->cpu_time = insert_cpu_time;
    }
}

always_inline uword
elt_is_deleted (timing_wheel_t * w, u32 user_data)
{
  return (hash_elts (w->deleted_user_data_hash) > 0
	  && hash_get (w->deleted_user_data_hash, user_data));
}

static timing_wheel_elt_t *
delete_user_data (timing_wheel_elt_t * elts, u32 user_data)
{
  uword found_match;
  timing_wheel_elt_t *e, *new_elts;

  /* Quickly scan to see if there are any elements to delete
     in this bucket. */
  found_match = 0;
  vec_foreach (e, elts)
  {
    found_match = e->user_data == user_data;
    if (found_match)
      break;
  }
  if (!found_match)
    return elts;

  /* Re-scan to build vector of new elts with matching user_data deleted. */
  new_elts = 0;
  vec_foreach (e, elts)
  {
    if (e->user_data != user_data)
      vec_add1 (new_elts, e[0]);
  }

  vec_free (elts);
  return new_elts;
}

/* Insert user data on wheel at given CPU time stamp. */
void
timing_wheel_insert (timing_wheel_t * w, u64 insert_cpu_time, u32 user_data)
{
  /* Remove previously deleted elements. */
  if (elt_is_deleted (w, user_data))
    {
      timing_wheel_level_t *l;
      uword wi;

      /* Delete elts with given user data so that stale events don't expire. */
      vec_foreach (l, w->levels)
      {
	  clib_bitmap_foreach (wi, l->occupancy_bitmap)  {
	    l->elts[wi] = delete_user_data (l->elts[wi], user_data);
	    if (vec_len (l->elts[wi]) == 0)
	      l->occupancy_bitmap = clib_bitmap_andnoti (l->occupancy_bitmap, wi);
	  }
      }

      {
	timing_wheel_overflow_elt_t *oe;
	pool_foreach (oe, w->overflow_pool)  {
	  if (oe->user_data == user_data)
	    pool_put (w->overflow_pool, oe);
	}
      }

      hash_unset (w->deleted_user_data_hash, user_data);
    }

  timing_wheel_insert_helper (w, insert_cpu_time, user_data);
}

void
timing_wheel_delete (timing_wheel_t * w, u32 user_data)
{
  if (!w->deleted_user_data_hash)
    w->deleted_user_data_hash =
      hash_create ( /* capacity */ 0, /* value bytes */ 0);

  hash_set1 (w->deleted_user_data_hash, user_data);
}

/* Returns time of next expiring element. */
u64
timing_wheel_next_expiring_elt_time (timing_wheel_t * w)
{
  timing_wheel_level_t *l;
  timing_wheel_elt_t *e;
  uword li, wi, wi0;
  u32 min_dt;
  u64 min_t;
  uword wrapped = 0;

  min_dt = ~0;
  min_t = ~0ULL;
  vec_foreach (l, w->levels)
  {
    if (!l->occupancy_bitmap)
      continue;

    li = l - w->levels;
    wi0 = wi = current_time_wheel_index (w, li);
    wrapped = 0;
    while (1)
      {
	if (clib_bitmap_get_no_check (l->occupancy_bitmap, wi))
	  {
	    vec_foreach (e, l->elts[wi])
	      min_dt = clib_min (min_dt, e->cpu_time_relative_to_base);

	    if (wrapped && li + 1 < vec_len (w->levels))
	      {
		uword wi1 = current_time_wheel_index (w, li + 1);
		if (l[1].occupancy_bitmap
		    && clib_bitmap_get_no_check (l[1].occupancy_bitmap, wi1))
		  {
		    vec_foreach (e, l[1].elts[wi1])
		    {
		      min_dt =
			clib_min (min_dt, e->cpu_time_relative_to_base);
		    }
		  }
	      }

	    min_t = w->cpu_time_base + min_dt;
	    goto done;
	  }

	wi = wheel_add (w, wi + 1);
	if (wi == wi0)
	  break;

	wrapped = wi != wi + 1;
      }
  }

  {
    timing_wheel_overflow_elt_t *oe;

    if (min_dt != ~0)
      min_t = w->cpu_time_base + min_dt;

    pool_foreach (oe, w->overflow_pool)
		   { min_t = clib_min (min_t, oe->cpu_time); }

  done:
    return min_t;
  }
}

static inline void
insert_elt (timing_wheel_t * w, timing_wheel_elt_t * e)
{
  u64 t = w->cpu_time_base + e->cpu_time_relative_to_base;
  timing_wheel_insert_helper (w, t, e->user_data);
}

always_inline u64
elt_cpu_time (timing_wheel_t * w, timing_wheel_elt_t * e)
{
  return w->cpu_time_base + e->cpu_time_relative_to_base;
}

always_inline void
validate_expired_elt (timing_wheel_t * w, timing_wheel_elt_t * e,
		      u64 current_cpu_time)
{
  if (CLIB_DEBUG > 0)
    {
      u64 e_time = elt_cpu_time (w, e);

      /* Verify that element is actually expired. */
      ASSERT ((e_time >> w->log2_clocks_per_bin)
	      <= (current_cpu_time >> w->log2_clocks_per_bin));
    }
}

static u32 *
expire_bin (timing_wheel_t * w,
	    uword level_index,
	    uword wheel_index, u64 advance_cpu_time, u32 * expired_user_data)
{
  timing_wheel_level_t *level = vec_elt_at_index (w->levels, level_index);
  timing_wheel_elt_t *e;
  u32 *x;
  uword i, j, e_len;

  e = vec_elt (level->elts, wheel_index);
  e_len = vec_len (e);

  vec_add2 (expired_user_data, x, e_len);
  for (i = j = 0; i < e_len; i++)
    {
      validate_expired_elt (w, &e[i], advance_cpu_time);
      x[j] = e[i].user_data;

      /* Only advance if elt is not to be deleted. */
      j += !elt_is_deleted (w, e[i].user_data);
    }

  /* Adjust for deleted elts. */
  if (j < e_len)
    vec_dec_len (expired_user_data, e_len - j);

  free_elt_vector (w, e);

  level->elts[wheel_index] = 0;
  clib_bitmap_set_no_check (level->occupancy_bitmap, wheel_index, 0);

  return expired_user_data;
}

/* Called rarely. 32 bit times should only overflow every 4 seconds or so on a fast machine. */
static u32 *
advance_cpu_time_base (timing_wheel_t * w, u32 * expired_user_data)
{
  timing_wheel_level_t *l;
  timing_wheel_elt_t *e;
  u64 delta;

  w->stats.cpu_time_base_advances++;
  delta = ((u64) 1 << w->n_wheel_elt_time_bits);
  w->cpu_time_base += delta;
  w->time_index_next_cpu_time_base_update += delta >> w->log2_clocks_per_bin;

  vec_foreach (l, w->levels)
  {
    uword wi;
      clib_bitmap_foreach (wi, l->occupancy_bitmap)  {
	vec_foreach (e, l->elts[wi])
	  {
	    /* This should always be true since otherwise we would have already expired
	       this element. Note that in the second half of this function we need
               to take care not to place the expired elements ourselves. */
	    ASSERT (e->cpu_time_relative_to_base >= delta);
	    e->cpu_time_relative_to_base -= delta;
	  }
      }
  }

  /* See which overflow elements fit now. */
  {
    timing_wheel_overflow_elt_t *oe;
    pool_foreach (oe, w->overflow_pool)  {
      /* It fits now into 32 bits. */
      if (0 == ((oe->cpu_time - w->cpu_time_base) >> BITS (e->cpu_time_relative_to_base)))
	{
	  u64 ti = oe->cpu_time >> w->log2_clocks_per_bin;
	  if (ti <= w->current_time_index)
	    {
	      /* This can happen when timing wheel is not advanced for a long time
		 (for example when at a gdb breakpoint for a while). */
              /* Note: the ti == w->current_time_index means it is also an expired timer */
	      if (! elt_is_deleted (w, oe->user_data))
		vec_add1 (expired_user_data, oe->user_data);
	    }
	  else
	    timing_wheel_insert_helper (w, oe->cpu_time, oe->user_data);
	  pool_put (w->overflow_pool, oe);
	}
    }
  }
  return expired_user_data;
}

static u32 *
refill_level (timing_wheel_t * w,
	      uword level_index,
	      u64 advance_cpu_time,
	      uword from_wheel_index,
	      uword to_wheel_index, u32 * expired_user_data)
{
  timing_wheel_level_t *level;
  timing_wheel_elt_t *to_insert = w->unexpired_elts_pending_insert;
  u64 advance_time_index = advance_cpu_time >> w->log2_clocks_per_bin;

  vec_validate (w->stats.refills, level_index);
  w->stats.refills[level_index] += 1;

  if (level_index + 1 >= vec_len (w->levels))
    goto done;

  level = vec_elt_at_index (w->levels, level_index + 1);
  if (!level->occupancy_bitmap)
    goto done;

  while (1)
    {
      timing_wheel_elt_t *e, *es;

      if (clib_bitmap_get_no_check
	  (level->occupancy_bitmap, from_wheel_index))
	{
	  es = level->elts[from_wheel_index];
	  level->elts[from_wheel_index] = 0;
	  clib_bitmap_set_no_check (level->occupancy_bitmap, from_wheel_index,
				    0);

	  vec_foreach (e, es)
	  {
	    u64 e_time = elt_cpu_time (w, e);
	    u64 ti = e_time >> w->log2_clocks_per_bin;
	    if (ti <= advance_time_index)
	      {
		validate_expired_elt (w, e, advance_cpu_time);
		if (!elt_is_deleted (w, e->user_data))
		  vec_add1 (expired_user_data, e->user_data);
	      }
	    else
	      vec_add1 (to_insert, e[0]);
	  }
	  free_elt_vector (w, es);
	}

      if (from_wheel_index == to_wheel_index)
	break;

      from_wheel_index = wheel_add (w, from_wheel_index + 1);
    }

  timing_wheel_validate (w);
done:
  w->unexpired_elts_pending_insert = to_insert;
  return expired_user_data;
}

/* Advance wheel and return any expired user data in vector. */
u32 *
timing_wheel_advance (timing_wheel_t * w, u64 advance_cpu_time,
		      u32 * expired_user_data,
		      u64 * next_expiring_element_cpu_time)
{
  timing_wheel_level_t *level;
  uword level_index, advance_rtime, advance_level_index, advance_wheel_index;
  uword n_expired_user_data_before;
  u64 current_time_index, advance_time_index;

  n_expired_user_data_before = vec_len (expired_user_data);

  /* Re-fill lower levels when time wraps. */
  current_time_index = w->current_time_index;
  advance_time_index = advance_cpu_time >> w->log2_clocks_per_bin;

  {
    u64 current_ti, advance_ti;

    current_ti = current_time_index >> w->log2_bins_per_wheel;
    advance_ti = advance_time_index >> w->log2_bins_per_wheel;

    if (PREDICT_FALSE (current_ti != advance_ti))
      {
	if (w->unexpired_elts_pending_insert)
	  vec_set_len (w->unexpired_elts_pending_insert, 0);

	level_index = 0;
	while (current_ti != advance_ti)
	  {
	    uword c, a;
	    c = current_ti & (w->bins_per_wheel - 1);
	    a = advance_ti & (w->bins_per_wheel - 1);
	    if (c != a)
	      expired_user_data = refill_level (w,
						level_index,
						advance_cpu_time,
						c, a, expired_user_data);
	    current_ti >>= w->log2_bins_per_wheel;
	    advance_ti >>= w->log2_bins_per_wheel;
	    level_index++;
	  }
      }
  }

  advance_level_index =
    get_level_and_relative_time (w, advance_cpu_time, &advance_rtime);
  advance_wheel_index =
    rtime_to_wheel_index (w, advance_level_index, advance_rtime);

  /* Empty all occupied bins for entire levels that we advance past. */
  for (level_index = 0; level_index < advance_level_index; level_index++)
    {
      uword wi;

      if (level_index >= vec_len (w->levels))
	break;

      level = vec_elt_at_index (w->levels, level_index);
      clib_bitmap_foreach (wi, level->occupancy_bitmap)  {
        expired_user_data = expire_bin (w, level_index, wi, advance_cpu_time,
					expired_user_data);
      }
    }

  if (PREDICT_TRUE (level_index < vec_len (w->levels)))
    {
      uword wi;
      level = vec_elt_at_index (w->levels, level_index);
      wi = current_time_wheel_index (w, level_index);
      if (level->occupancy_bitmap)
	while (1)
	  {
	    if (clib_bitmap_get_no_check (level->occupancy_bitmap, wi))
	      expired_user_data =
		expire_bin (w, advance_level_index, wi, advance_cpu_time,
			    expired_user_data);

	    /* When we jump out, we have already just expired the bin,
	       corresponding to advance_wheel_index */
	    if (wi == advance_wheel_index)
	      break;

	    wi = wheel_add (w, wi + 1);
	  }
    }

  /* Advance current time index. */
  w->current_time_index = advance_time_index;

  if (vec_len (w->unexpired_elts_pending_insert) > 0)
    {
      timing_wheel_elt_t *e;
      vec_foreach (e, w->unexpired_elts_pending_insert) insert_elt (w, e);
      vec_set_len (w->unexpired_elts_pending_insert, 0);
    }

  /* Don't advance until necessary. */
  /* However, if the timing_wheel_advance() hasn't been called for some time,
     the while() loop will ensure multiple calls to advance_cpu_time_base()
     in a row until the w->cpu_time_base is fresh enough. */
  while (PREDICT_FALSE
	 (advance_time_index >= w->time_index_next_cpu_time_base_update))
    expired_user_data = advance_cpu_time_base (w, expired_user_data);

  if (next_expiring_element_cpu_time)
    {
      u64 min_t;

      /* Anything expired?  If so we need to recompute next expiring elt time. */
      if (vec_len (expired_user_data) == n_expired_user_data_before
	  && w->cached_min_cpu_time_on_wheel != 0ULL)
	min_t = w->cached_min_cpu_time_on_wheel;
      else
	{
	  min_t = timing_wheel_next_expiring_elt_time (w);
	  w->cached_min_cpu_time_on_wheel = min_t;
	}

      *next_expiring_element_cpu_time = min_t;
    }

  return expired_user_data;
}

u8 *
format_timing_wheel (u8 * s, va_list * va)
{
  timing_wheel_t *w = va_arg (*va, timing_wheel_t *);
  int verbose = va_arg (*va, int);
  u32 indent = format_get_indent (s);

  s = format (s, "level 0: %.4e - %.4e secs, 2^%d - 2^%d clocks",
	      (f64) (1 << w->log2_clocks_per_bin) / w->cpu_clocks_per_second,
	      (f64) (1 << w->log2_clocks_per_wheel) /
	      w->cpu_clocks_per_second, w->log2_clocks_per_bin,
	      w->log2_clocks_per_wheel);

  if (verbose)
    {
      int l;

      s = format (s, "\n%Utime base advances %Ld, every %.4e secs",
		  format_white_space, indent + 2,
		  w->stats.cpu_time_base_advances,
		  (f64) ((u64) 1 << w->n_wheel_elt_time_bits) /
		  w->cpu_clocks_per_second);

      for (l = 0; l < vec_len (w->levels); l++)
	s = format (s, "\n%Ulevel %d: refills %Ld",
		    format_white_space, indent + 2,
		    l,
		    l <
		    vec_len (w->stats.refills) ? w->stats.
		    refills[l] : (u64) 0);
    }

  return s;
}

/*
 * fd.io coding-style-patch-verification: ON
 *
 * Local Variables:
 * eval: (c-set-style "gnu")
 * End:
 */