aboutsummaryrefslogtreecommitdiffstats
path: root/src/vppinfra/tw_timer_template.c
blob: 436dd4e1f66a34980d3044a80987d8e596407002 (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
/*
 * Copyright (c) 2016 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.
 */

/** @file
 *  @brief TW timer implementation TEMPLATE ONLY, do not compile directly
 *
 *
 */

static inline u32
TW (make_internal_timer_handle) (u32 pool_index, u32 timer_id)
{
  u32 handle;

  ASSERT (timer_id < TW_TIMERS_PER_OBJECT);
  ASSERT (pool_index < (1 << (32 - LOG2_TW_TIMERS_PER_OBJECT)));

  handle = (timer_id << (32 - LOG2_TW_TIMERS_PER_OBJECT)) | (pool_index);
  return handle;
}

static inline void
timer_addhead (TWT (tw_timer) * pool, u32 head_index, u32 new_index)
{
  TWT (tw_timer) * head = pool_elt_at_index (pool, head_index);
  TWT (tw_timer) * old_first;
  u32 old_first_index;
  TWT (tw_timer) * new;

  new = pool_elt_at_index (pool, new_index);

  if (PREDICT_FALSE (head->next == head_index))
    {
      head->next = head->prev = new_index;
      new->next = new->prev = head_index;
      return;
    }

  old_first_index = head->next;
  old_first = pool_elt_at_index (pool, old_first_index);

  new->next = old_first_index;
  new->prev = old_first->prev;
  old_first->prev = new_index;
  head->next = new_index;
}

static inline void
timer_remove (TWT (tw_timer) * pool, u32 index)
{
  TWT (tw_timer) * elt = pool_elt_at_index (pool, index);
  TWT (tw_timer) * next_elt, *prev_elt;

  ASSERT (elt->user_handle != ~0);

  next_elt = pool_elt_at_index (pool, elt->next);
  prev_elt = pool_elt_at_index (pool, elt->prev);

  next_elt->prev = elt->prev;
  prev_elt->next = elt->next;

  elt->prev = elt->next = ~0;
}

/**
 * @brief Start a Tw Timer
 * @param tw_timer_wheel_t * tw timer wheel object pointer
 * @param u32 pool_index user pool index, presumably for a tw session
 * @param u32 timer_id app-specific timer ID. 4 bits.
 * @param u32 interval timer interval in ticks
 * @returns handle needed to cancel the timer
 */
u32
TW (tw_timer_start) (TWT (tw_timer_wheel) * tw, u32 pool_index, u32 timer_id,
		     u32 interval)
{
#if TW_TIMER_WHEELS > 1
  u16 slow_ring_offset;
  u32 carry;
#endif
  u16 fast_ring_offset;
  tw_timer_wheel_slot_t *ts;
  TWT (tw_timer) * t;

  ASSERT (interval);

  pool_get (tw->timers, t);
  t->next = t->prev = ~0;
#if TW_TIMER_WHEELS > 1
  t->fast_ring_offset = ~0;
#endif
  t->user_handle = TW (make_internal_timer_handle) (pool_index, timer_id);

  fast_ring_offset = interval & TW_RING_MASK;
  fast_ring_offset += tw->current_index[TW_TIMER_RING_FAST];
#if TW_TIMER_WHEELS > 1
  carry = fast_ring_offset >= TW_SLOTS_PER_RING ? 1 : 0;
  fast_ring_offset %= TW_SLOTS_PER_RING;
  slow_ring_offset = (interval >> TW_RING_SHIFT) + carry;

  /* Timer duration exceeds ~7 hrs? Oops */
  ASSERT (slow_ring_offset < TW_SLOTS_PER_RING);

  /* Timer expires more than 51.2 seconds from now? */
  if (slow_ring_offset)
    {
      slow_ring_offset += tw->current_index[TW_TIMER_RING_SLOW];
      slow_ring_offset %= TW_SLOTS_PER_RING;

      /* We'll want the fast ring offset later... */
      t->fast_ring_offset = fast_ring_offset;
      ASSERT (t->fast_ring_offset < TW_SLOTS_PER_RING);

      ts = &tw->w[TW_TIMER_RING_SLOW][slow_ring_offset];

      timer_addhead (tw->timers, ts->head_index, t - tw->timers);

      return t - tw->timers;
    }
#else
  fast_ring_offset %= TW_SLOTS_PER_RING;
  ASSERT (interval < TW_SLOTS_PER_RING);
#endif

  /* Timer expires less than one fast-ring revolution from now */
  ts = &tw->w[TW_TIMER_RING_FAST][fast_ring_offset];

  timer_addhead (tw->timers, ts->head_index, t - tw->timers);
  return t - tw->timers;
}

/**
 * @brief Stop a tw timer
 * @param tw_timer_wheel_t * tw timer wheel object pointer
 * @param u32 handle timer cancellation returned by tw_timer_start
 */
void TW (tw_timer_stop) (TWT (tw_timer_wheel) * tw, u32 handle)
{
  TWT (tw_timer) * t;

  t = pool_elt_at_index (tw->timers, handle);

  /* in case of idiotic handle (e.g. passing a listhead index) */
  ASSERT (t->user_handle != ~0);

  timer_remove (tw->timers, handle);

  pool_put_index (tw->timers, handle);
}

/**
 * @brief Initialize a tw timer wheel template instance
 * @param tw_timer_wheel_t * tw timer wheel object pointer
 * @param void * expired_timer_callback. Passed a u32 * vector of
 *   expired timer handles.
 * @param f64 timer_interval_in_seconds
 */
void
TW (tw_timer_wheel_init) (TWT (tw_timer_wheel) * tw,
			  void *expired_timer_callback,
			  f64 timer_interval_in_seconds, u32 max_expirations)
{
  int ring, slot;
  tw_timer_wheel_slot_t *ts;
  TWT (tw_timer) * t;
  memset (tw, 0, sizeof (*tw));
  tw->expired_timer_callback = expired_timer_callback;
  tw->max_expirations = max_expirations;
  if (timer_interval_in_seconds == 0.0)
    {
      clib_warning ("timer interval is zero");
      abort ();
    }
  tw->timer_interval = timer_interval_in_seconds;
  tw->ticks_per_second = 1.0 / timer_interval_in_seconds;

  for (ring = 0; ring < TW_TIMER_WHEELS; ring++)
    {
      for (slot = 0; slot < TW_SLOTS_PER_RING; slot++)
	{
	  ts = &tw->w[ring][slot];
	  pool_get (tw->timers, t);
	  memset (t, 0xff, sizeof (*t));
	  t->next = t->prev = t - tw->timers;
	  ts->head_index = t - tw->timers;
	}
    }
}

/**
 * @brief Free a tw timer wheel template instance
 * @param tw_timer_wheel_t * tw timer wheel object pointer
 */
void TW (tw_timer_wheel_free) (TWT (tw_timer_wheel) * tw)
{
  int i, j;
  tw_timer_wheel_slot_t *ts;
  TWT (tw_timer) * head, *t;
  u32 next_index;

  for (i = 0; i < TW_TIMER_WHEELS; i++)
    {
      for (j = 0; j < TW_SLOTS_PER_RING; j++)
	{
	  ts = &tw->w[i][j];
	  head = pool_elt_at_index (tw->timers, ts->head_index);
	  next_index = head->next;

	  while (next_index != ts->head_index)
	    {
	      t = pool_elt_at_index (tw->timers, next_index);
	      next_index = t->next;
	      pool_put (tw->timers, t);
	    }
	  pool_put (tw->timers, head);
	}
    }
  memset (tw, 0, sizeof (*tw));
}

/**
 * @brief Advance a tw timer wheel. Calls the expired timer callback
 * as needed. This routine should be called once every timer_interval seconds
 * @param tw_timer_wheel_t * tw timer wheel template instance pointer
 * @param f64 now the current time, e.g. from vlib_time_now(vm)
 */
u32 TW (tw_timer_expire_timers) (TWT (tw_timer_wheel) * tw, f64 now)
{
  u32 nticks, i;
  tw_timer_wheel_slot_t *ts;
  TWT (tw_timer) * t, *head;
  u32 fast_wheel_index;
  u32 next_index;
  u32 nexpirations, total_nexpirations;
#if TW_TIMER_WHEELS > 1
  u32 slow_wheel_index;
#endif

  /* Shouldn't happen */
  if (PREDICT_FALSE (now < tw->next_run_time))
    return 0;

  /* Number of ticks which have occurred */
  nticks = tw->ticks_per_second * (now - tw->last_run_time);
  if (nticks == 0)
    return 0;

  /* Remember when we ran, compute next runtime */
  tw->next_run_time = (now + tw->timer_interval);

  total_nexpirations = 0;
  for (i = 0; i < nticks; i++)
    {
      fast_wheel_index = tw->current_index[TW_TIMER_RING_FAST];

      /*
       * If we've been around the fast ring once,
       * process one slot in the slow ring before we handle
       * the fast ring.
       */
      if (PREDICT_FALSE (fast_wheel_index == TW_SLOTS_PER_RING))
	{
	  fast_wheel_index = tw->current_index[TW_TIMER_RING_FAST] = 0;

#if TW_TIMER_WHEELS > 1
	  tw->current_index[TW_TIMER_RING_SLOW]++;
	  tw->current_index[TW_TIMER_RING_SLOW] %= TW_SLOTS_PER_RING;
	  slow_wheel_index = tw->current_index[TW_TIMER_RING_SLOW];

	  ts = &tw->w[TW_TIMER_RING_SLOW][slow_wheel_index];

	  head = pool_elt_at_index (tw->timers, ts->head_index);
	  next_index = head->next;

	  /* Make slot empty */
	  head->next = head->prev = ts->head_index;

	  /* traverse slot, deal timers into fast ring */
	  while (next_index != head - tw->timers)
	    {
	      t = pool_elt_at_index (tw->timers, next_index);
	      next_index = t->next;

	      /* Remove from slow ring slot (hammer) */
	      t->next = t->prev = ~0;
	      ASSERT (t->fast_ring_offset < TW_SLOTS_PER_RING);
	      /* Add to fast ring */
	      ts = &tw->w[TW_TIMER_RING_FAST][t->fast_ring_offset];
	      timer_addhead (tw->timers, ts->head_index, t - tw->timers);
	    }
#endif
	}

      /* Handle the fast ring */
      vec_reset_length (tw->expired_timer_handles);

      ts = &tw->w[TW_TIMER_RING_FAST][fast_wheel_index];

      head = pool_elt_at_index (tw->timers, ts->head_index);
      next_index = head->next;

      /* Make slot empty */
      head->next = head->prev = ts->head_index;

      /* Construct vector of expired timer handles to give the user */
      while (next_index != ts->head_index)
	{
	  t = pool_elt_at_index (tw->timers, next_index);
	  next_index = t->next;
	  vec_add1 (tw->expired_timer_handles, t->user_handle);
	  pool_put (tw->timers, t);
	}

      /* If any timers expired, tell the user */
      nexpirations = vec_len (tw->expired_timer_handles);
      if (nexpirations)
	{
	  tw->expired_timer_callback (tw->expired_timer_handles);
	  total_nexpirations += nexpirations;
	}
      tw->current_index[TW_TIMER_RING_FAST]++;
      tw->current_tick++;

      if (total_nexpirations >= tw->max_expirations)
	break;
    }

  tw->last_run_time += i * tw->ticks_per_second;
  return total_nexpirations;
}

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