Wheel-timer infra

Change-Id: I5499dd6b768425a56936afae50bd578620c83d30
Signed-off-by: Dave Barach <dave@barachs.net>

1 files changed, 341 insertions, 0 deletions

diff --git a/src/vppinfra/tw_timer_template.c b/src/vppinfra/tw_timer_template.c
new file mode 100644
index 00000000000..9aa5624f91f
--- /dev/null
+++ b/src/vppinfra/tw_timer_template.c
@@ -0,0 +1,341 @@
+/*
+ * 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 pool_index user pool index, passed for consistency checking only
+ * @param u32 timer_id 4 bit timer ID, passed for consistency checking only
+ * @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)
+{
+  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;
+  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)
+ */
+void 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;
+#if TW_TIMER_WHEELS > 1
+  u32 slow_wheel_index;
+#endif
+
+  /* Shouldn't happen */
+  if (PREDICT_FALSE (now < tw->next_run_time))
+    return;
+
+  /* Number of ticks which have occurred */
+  nticks = tw->ticks_per_second * (now - tw->last_run_time);
+  if (nticks == 0)
+    return;
+
+  /* Remember when we ran, compute next runtime */
+  tw->next_run_time = (now + tw->timer_interval);
+  tw->last_run_time = now;
+
+  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 */
+      if (vec_len (tw->expired_timer_handles))
+	tw->expired_timer_callback (tw->expired_timer_handles);
+      tw->current_index[TW_TIMER_RING_FAST]++;
+      tw->current_tick++;
+    }
+}
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */