Wheel-timer infra

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

7 files changed, 1276 insertions, 0 deletions

diff --git a/src/vppinfra/test_tw_timer.c b/src/vppinfra/test_tw_timer.c
new file mode 100644
index 00000000..a0287b89
--- /dev/null
+++ b/src/vppinfra/test_tw_timer.c
@@ -0,0 +1,592 @@
+#include <vppinfra/time.h>
+#include <vppinfra/cache.h>
+#include <vppinfra/error.h>
+#include <vppinfra/tw_timer_2t_1w_2048sl.h>
+#include <vppinfra/tw_timer_16t_2w_512sl.h>
+
+typedef struct
+{
+  /** Handle returned from tw_start_timer */
+  u32 stop_timer_handle;
+
+  /** Test item should expire at this clock tick */
+  u32 expected_to_expire;
+} tw_timer_test_elt_t;
+
+typedef struct
+{
+  /** Pool of test objects */
+  tw_timer_test_elt_t *test_elts;
+
+  /** The single-wheel */
+  tw_timer_wheel_2t_1w_2048sl_t single_wheel;
+
+  /** The double-wheel */
+  tw_timer_wheel_16t_2w_512sl_t double_wheel;
+
+  /** random number seed */
+  u32 seed;
+
+  /** number of timers */
+  u32 ntimers;
+
+  /** number of "churn" iterations */
+  u32 niter;
+
+  /** number of clock ticks per churn iteration */
+  u32 ticks_per_iter;
+
+  /** cpu timer */
+  clib_time_t clib_time;
+} tw_timer_test_main_t;
+
+tw_timer_test_main_t tw_timer_test_main;
+
+static void
+run_single_wheel (tw_timer_wheel_2t_1w_2048sl_t * tw, u32 n_ticks)
+{
+  u32 i;
+  f64 now = tw->last_run_time + 1.01;
+
+  for (i = 0; i < n_ticks; i++)
+    {
+      tw_timer_expire_timers_2t_1w_2048sl (tw, now);
+      now += 1.01;
+    }
+}
+
+static void
+run_double_wheel (tw_timer_wheel_16t_2w_512sl_t * tw, u32 n_ticks)
+{
+  u32 i;
+  f64 now = tw->last_run_time + 1.01;
+
+  for (i = 0; i < n_ticks; i++)
+    {
+      tw_timer_expire_timers_16t_2w_512sl (tw, now);
+      now += 1.01;
+    }
+}
+
+static void
+expired_timer_single_callback (u32 * expired_timers)
+{
+  int i;
+  u32 pool_index, timer_id;
+  tw_timer_test_elt_t *e;
+  tw_timer_test_main_t *tm = &tw_timer_test_main;
+
+  for (i = 0; i < vec_len (expired_timers); i++)
+    {
+      pool_index = expired_timers[i] & 0x7FFFFFFF;
+      timer_id = expired_timers[i] >> 31;
+
+      ASSERT (timer_id == 1);
+
+      e = pool_elt_at_index (tm->test_elts, pool_index);
+
+      if (e->expected_to_expire != tm->single_wheel.current_tick)
+	{
+	  fformat (stdout, "[%d] expired at %d not %d\n",
+		   e - tm->test_elts, tm->single_wheel.current_tick,
+		   e->expected_to_expire);
+	}
+      pool_put (tm->test_elts, e);
+    }
+}
+
+static void
+expired_timer_double_callback (u32 * expired_timers)
+{
+  int i;
+  u32 pool_index, timer_id;
+  tw_timer_test_elt_t *e;
+  tw_timer_test_main_t *tm = &tw_timer_test_main;
+
+  for (i = 0; i < vec_len (expired_timers); i++)
+    {
+      pool_index = expired_timers[i] & 0x0FFFFFFF;
+      timer_id = expired_timers[i] >> 28;
+
+      ASSERT (timer_id == 14);
+
+      e = pool_elt_at_index (tm->test_elts, pool_index);
+
+      if (e->expected_to_expire != tm->double_wheel.current_tick)
+	{
+	  fformat (stdout, "[%d] expired at %d not %d\n",
+		   e - tm->test_elts, tm->double_wheel.current_tick,
+		   e->expected_to_expire);
+	}
+      pool_put (tm->test_elts, e);
+    }
+}
+
+static clib_error_t *
+test2_single (tw_timer_test_main_t * tm)
+{
+  u32 i, j;
+  tw_timer_test_elt_t *e;
+  u32 initial_wheel_offset;
+  u32 expiration_time;
+  u32 max_expiration_time = 0;
+  u32 *deleted_indices = 0;
+  u32 adds = 0, deletes = 0;
+  f64 before, after;
+
+  clib_time_init (&tm->clib_time);
+
+  tw_timer_wheel_init_2t_1w_2048sl (&tm->single_wheel,
+				    expired_timer_single_callback,
+				    1.0 /* timer interval */ );
+
+  /* Prime offset */
+  initial_wheel_offset = 757;
+
+  run_single_wheel (&tm->single_wheel, initial_wheel_offset);
+
+  fformat (stdout, "test %d timers, %d iter, %d ticks per iter, 0x%x seed\n",
+	   tm->ntimers, tm->niter, tm->ticks_per_iter, tm->seed);
+
+  before = clib_time_now (&tm->clib_time);
+
+  /* Prime the pump */
+  for (i = 0; i < tm->ntimers; i++)
+    {
+      pool_get (tm->test_elts, e);
+      memset (e, 0, sizeof (*e));
+
+      do
+	{
+	  expiration_time = random_u32 (&tm->seed) & (2047);
+	}
+      while (expiration_time == 0);
+
+      if (expiration_time > max_expiration_time)
+	max_expiration_time = expiration_time;
+
+      e->expected_to_expire = expiration_time + initial_wheel_offset;
+      e->stop_timer_handle =
+	tw_timer_start_2t_1w_2048sl (&tm->single_wheel, e - tm->test_elts,
+				     1 /* timer id */ ,
+				     expiration_time);
+    }
+
+  adds += i;
+
+  for (i = 0; i < tm->niter; i++)
+    {
+      run_single_wheel (&tm->single_wheel, tm->ticks_per_iter);
+
+      j = 0;
+      vec_reset_length (deleted_indices);
+      /* *INDENT-OFF* */
+      pool_foreach (e, tm->test_elts,
+      ({
+        tw_timer_stop_2t_1w_2048sl (&tm->single_wheel, e->stop_timer_handle);
+        vec_add1 (deleted_indices, e - tm->test_elts);
+        if (++j >= tm->ntimers / 4)
+          goto del_and_re_add;
+      }));
+      /* *INDENT-ON* */
+
+    del_and_re_add:
+      for (j = 0; j < vec_len (deleted_indices); j++)
+	pool_put_index (tm->test_elts, deleted_indices[j]);
+
+      deletes += j;
+
+      for (j = 0; j < tm->ntimers / 4; j++)
+	{
+	  pool_get (tm->test_elts, e);
+	  memset (e, 0, sizeof (*e));
+
+	  do
+	    {
+	      expiration_time = random_u32 (&tm->seed) & (2047);
+	    }
+	  while (expiration_time == 0);
+
+	  if (expiration_time > max_expiration_time)
+	    max_expiration_time = expiration_time;
+
+	  e->expected_to_expire =
+	    expiration_time + tm->single_wheel.current_tick;
+	  e->stop_timer_handle = tw_timer_start_2t_1w_2048sl
+	    (&tm->single_wheel, e - tm->test_elts, 1 /* timer id */ ,
+	     expiration_time);
+	}
+      adds += j;
+    }
+
+  vec_free (deleted_indices);
+
+  run_single_wheel (&tm->single_wheel, max_expiration_time + 1);
+
+  after = clib_time_now (&tm->clib_time);
+
+  fformat (stdout, "%d adds, %d deletes, %d ticks\n", adds, deletes,
+	   tm->single_wheel.current_tick);
+  fformat (stdout, "test ran %.2f seconds, %.2f ops/second\n",
+	   (after - before),
+	   ((f64) adds + (f64) deletes +
+	    (f64) tm->single_wheel.current_tick) / (after - before));
+
+  if (pool_elts (tm->test_elts))
+    fformat (stdout, "Note: %d elements remain in pool\n",
+	     pool_elts (tm->test_elts));
+
+  /* *INDENT-OFF* */
+  pool_foreach (e, tm->test_elts,
+  ({
+    fformat (stdout, "[%d] expected to expire %d\n",
+             e - tm->test_elts,
+             e->expected_to_expire);
+  }));
+  /* *INDENT-ON* */
+
+  pool_free (tm->test_elts);
+  tw_timer_wheel_free_2t_1w_2048sl (&tm->single_wheel);
+  return 0;
+}
+
+static clib_error_t *
+test2_double (tw_timer_test_main_t * tm)
+{
+  u32 i, j;
+  tw_timer_test_elt_t *e;
+  u32 initial_wheel_offset;
+  u32 expiration_time;
+  u32 max_expiration_time = 0;
+  u32 *deleted_indices = 0;
+  u32 adds = 0, deletes = 0;
+  f64 before, after;
+
+  clib_time_init (&tm->clib_time);
+
+  tw_timer_wheel_init_16t_2w_512sl (&tm->double_wheel,
+				    expired_timer_double_callback,
+				    1.0 /* timer interval */ );
+
+  /* Prime offset */
+  initial_wheel_offset = 757;
+
+  run_double_wheel (&tm->double_wheel, initial_wheel_offset);
+
+  fformat (stdout, "test %d timers, %d iter, %d ticks per iter, 0x%x seed\n",
+	   tm->ntimers, tm->niter, tm->ticks_per_iter, tm->seed);
+
+  before = clib_time_now (&tm->clib_time);
+
+  /* Prime the pump */
+  for (i = 0; i < tm->ntimers; i++)
+    {
+      pool_get (tm->test_elts, e);
+      memset (e, 0, sizeof (*e));
+
+      do
+	{
+	  expiration_time = random_u32 (&tm->seed) & ((1 << 17) - 1);
+	}
+      while (expiration_time == 0);
+
+      if (expiration_time > max_expiration_time)
+	max_expiration_time = expiration_time;
+
+      e->expected_to_expire = expiration_time + initial_wheel_offset;
+      e->stop_timer_handle =
+	tw_timer_start_16t_2w_512sl (&tm->double_wheel, e - tm->test_elts,
+				     14 /* timer id */ ,
+				     expiration_time);
+    }
+
+  adds += i;
+
+  for (i = 0; i < tm->niter; i++)
+    {
+      run_double_wheel (&tm->double_wheel, tm->ticks_per_iter);
+
+      j = 0;
+      vec_reset_length (deleted_indices);
+      /* *INDENT-OFF* */
+      pool_foreach (e, tm->test_elts,
+      ({
+        tw_timer_stop_16t_2w_512sl (&tm->double_wheel, e->stop_timer_handle);
+        vec_add1 (deleted_indices, e - tm->test_elts);
+        if (++j >= tm->ntimers / 4)
+          goto del_and_re_add;
+      }));
+      /* *INDENT-ON* */
+
+    del_and_re_add:
+      for (j = 0; j < vec_len (deleted_indices); j++)
+	pool_put_index (tm->test_elts, deleted_indices[j]);
+
+      deletes += j;
+
+      for (j = 0; j < tm->ntimers / 4; j++)
+	{
+	  pool_get (tm->test_elts, e);
+	  memset (e, 0, sizeof (*e));
+
+	  do
+	    {
+	      expiration_time = random_u32 (&tm->seed) & ((1 << 17) - 1);
+	    }
+	  while (expiration_time == 0);
+
+	  if (expiration_time > max_expiration_time)
+	    max_expiration_time = expiration_time;
+
+	  e->expected_to_expire = expiration_time +
+	    tm->double_wheel.current_tick;
+	  e->stop_timer_handle = tw_timer_start_16t_2w_512sl
+	    (&tm->double_wheel, e - tm->test_elts, 14 /* timer id */ ,
+	     expiration_time);
+	}
+      adds += j;
+    }
+
+  vec_free (deleted_indices);
+
+  run_double_wheel (&tm->double_wheel, max_expiration_time + 1);
+
+  after = clib_time_now (&tm->clib_time);
+
+  fformat (stdout, "%d adds, %d deletes, %d ticks\n", adds, deletes,
+	   tm->double_wheel.current_tick);
+  fformat (stdout, "test ran %.2f seconds, %.2f ops/second\n",
+	   (after - before),
+	   ((f64) adds + (f64) deletes +
+	    (f64) tm->double_wheel.current_tick) / (after - before));
+
+  if (pool_elts (tm->test_elts))
+    fformat (stdout, "Note: %d elements remain in pool\n",
+	     pool_elts (tm->test_elts));
+
+  /* *INDENT-OFF* */
+  pool_foreach (e, tm->test_elts,
+  ({
+    fformat (stdout, "[%d] expected to expire %d\n",
+             e - tm->test_elts,
+             e->expected_to_expire);
+  }));
+  /* *INDENT-ON* */
+
+  pool_free (tm->test_elts);
+  tw_timer_wheel_free_16t_2w_512sl (&tm->double_wheel);
+  return 0;
+}
+
+static clib_error_t *
+test1_single (tw_timer_test_main_t * tm)
+{
+  u32 i;
+  tw_timer_test_elt_t *e;
+  u32 offset;
+
+  tw_timer_wheel_init_2t_1w_2048sl (&tm->single_wheel,
+				    expired_timer_single_callback,
+				    1.0 /* timer interval */ );
+
+  /*
+   * Prime offset, to make sure that the wheel starts in a
+   * non-trivial position
+   */
+  offset = 123;
+
+  run_single_wheel (&tm->single_wheel, offset);
+
+  fformat (stdout, "initial wheel time %d, fast index %d\n",
+	   tm->single_wheel.current_tick,
+	   tm->single_wheel.current_index[TW_TIMER_RING_FAST]);
+
+  for (i = 0; i < tm->ntimers; i++)
+    {
+      u32 expected_to_expire;
+      u32 timer_arg;
+
+      timer_arg = 1 + i;
+      timer_arg &= 2047;
+      if (timer_arg == 0)
+	timer_arg = 1;
+
+      expected_to_expire = timer_arg + offset;
+
+      pool_get (tm->test_elts, e);
+      memset (e, 0, sizeof (*e));
+      e->expected_to_expire = expected_to_expire;
+      e->stop_timer_handle = tw_timer_start_2t_1w_2048sl
+	(&tm->single_wheel, e - tm->test_elts, 1 /* timer id */ ,
+	 timer_arg);
+    }
+  run_single_wheel (&tm->single_wheel, tm->ntimers + 3);
+
+  if (pool_elts (tm->test_elts))
+    fformat (stdout, "Note: %d elements remain in pool\n",
+	     pool_elts (tm->test_elts));
+
+  /* *INDENT-OFF* */
+  pool_foreach (e, tm->test_elts,
+  ({
+    fformat(stdout, "[%d] expected to expire %d\n",
+                     e - tm->test_elts,
+                     e->expected_to_expire);
+  }));
+  /* *INDENT-ON* */
+
+  fformat (stdout,
+	   "final wheel time %d, fast index %d\n",
+	   tm->single_wheel.current_tick,
+	   tm->single_wheel.current_index[TW_TIMER_RING_FAST]);
+
+  pool_free (tm->test_elts);
+  tw_timer_wheel_free_2t_1w_2048sl (&tm->single_wheel);
+  return 0;
+}
+
+static clib_error_t *
+test1_double (tw_timer_test_main_t * tm)
+{
+  u32 i;
+  tw_timer_test_elt_t *e;
+  u32 offset;
+
+  tw_timer_wheel_init_16t_2w_512sl (&tm->double_wheel,
+				    expired_timer_double_callback,
+				    1.0 /* timer interval */ );
+
+  /*
+   * Prime offset, to make sure that the wheel starts in a
+   * non-trivial position
+   */
+  offset = 227989;
+
+  run_double_wheel (&tm->double_wheel, offset);
+
+  fformat (stdout, "initial wheel time %d, fast index %d\n",
+	   tm->double_wheel.current_tick,
+	   tm->double_wheel.current_index[TW_TIMER_RING_FAST]);
+
+  for (i = 0; i < tm->ntimers; i++)
+    {
+      pool_get (tm->test_elts, e);
+      memset (e, 0, sizeof (*e));
+
+      e->expected_to_expire = i + offset + 1;
+      e->stop_timer_handle = tw_timer_start_16t_2w_512sl
+	(&tm->double_wheel, e - tm->test_elts, 14 /* timer id */ ,
+	 i + 1);
+    }
+  run_double_wheel (&tm->double_wheel, tm->ntimers + 3);
+
+  if (pool_elts (tm->test_elts))
+    fformat (stdout, "Note: %d elements remain in pool\n",
+	     pool_elts (tm->test_elts));
+
+  /* *INDENT-OFF* */
+  pool_foreach (e, tm->test_elts,
+  ({
+    fformat(stdout, "[%d] expected to expire %d\n",
+                     e - tm->test_elts,
+                     e->expected_to_expire);
+  }));
+  /* *INDENT-ON* */
+
+  fformat (stdout,
+	   "final wheel time %d, fast index %d\n",
+	   tm->double_wheel.current_tick,
+	   tm->double_wheel.current_index[TW_TIMER_RING_FAST]);
+
+  pool_free (tm->test_elts);
+  tw_timer_wheel_free_16t_2w_512sl (&tm->double_wheel);
+  return 0;
+}
+
+static clib_error_t *
+timer_test_command_fn (tw_timer_test_main_t * tm, unformat_input_t * input)
+{
+
+  int is_test1 = 0;
+  int num_wheels = 1;
+  int is_test2 = 0;
+
+  memset (tm, 0, sizeof (*tm));
+  /* Default values */
+  tm->ntimers = 100000;
+  tm->seed = 0xDEADDABE;
+  tm->niter = 1000;
+  tm->ticks_per_iter = 727;
+
+  while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
+    {
+      if (unformat (input, "seed %d", &tm->seed))
+	;
+      else if (unformat (input, "test1"))
+	is_test1 = 1;
+      else if (unformat (input, "test2"))
+	is_test2 = 1;
+      else if (unformat (input, "wheels %d", &num_wheels))
+	;
+      else if (unformat (input, "ntimers %d", &tm->ntimers))
+	;
+      else if (unformat (input, "niter %d", &tm->niter))
+	;
+      else if (unformat (input, "ticks_per_iter %d", &tm->ticks_per_iter))
+	;
+    }
+
+  if (is_test1 + is_test2 == 0)
+    return clib_error_return (0, "No test specified [test1..n]");
+
+  if (num_wheels < 1 || num_wheels > 2)
+    return clib_error_return (0, "unsupported... 1 or 2 wheels only");
+
+  if (is_test1)
+    {
+      if (num_wheels == 1)
+	return test1_single (tm);
+      else
+	return test1_double (tm);
+    }
+  if (is_test2)
+    {
+      if (num_wheels == 1)
+	return test2_single (tm);
+      else
+	return test2_double (tm);
+    }
+  /* NOTREACHED */
+  return 0;
+}
+
+#ifdef CLIB_UNIX
+int
+main (int argc, char *argv[])
+{
+  unformat_input_t i;
+  clib_error_t *error;
+  tw_timer_test_main_t *tm = &tw_timer_test_main;
+
+  clib_mem_init (0, 3ULL << 30);
+
+  unformat_init_command_line (&i, argv);
+  error = timer_test_command_fn (tm, &i);
+  unformat_free (&i);
+
+  if (error)
+    {
+      clib_error_report (error);
+      return 1;
+    }
+  return 0;
+}
+#endif /* CLIB_UNIX */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vppinfra/tw_timer_16t_2w_512sl.c b/src/vppinfra/tw_timer_16t_2w_512sl.c
new file mode 100644
index 00000000..ad1b9a4a
--- /dev/null
+++ b/src/vppinfra/tw_timer_16t_2w_512sl.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2017 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/error.h>
+#include "tw_timer_16t_2w_512sl.h"
+#include "tw_timer_template.c"
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vppinfra/tw_timer_16t_2w_512sl.h b/src/vppinfra/tw_timer_16t_2w_512sl.h
new file mode 100644
index 00000000..93b26d29
--- /dev/null
+++ b/src/vppinfra/tw_timer_16t_2w_512sl.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2017 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.
+ */
+
+#ifndef __included_tw_timer_16t_2w_512sl_h__
+#define __included_tw_timer_16t_2w_512sl_h__
+
+/* ... So that a client app can create multiple wheel geometries */
+#undef TW_TIMER_WHEELS
+#undef TW_SLOTS_PER_RING
+#undef TW_RING_SHIFT
+#undef TW_RING_MASK
+#undef TW_TIMERS_PER_OBJECT
+#undef LOG2_TW_TIMERS_PER_OBJECT
+#undef TW_SUFFIX
+
+#define TW_TIMER_WHEELS 2
+#define TW_SLOTS_PER_RING 512
+#define TW_RING_SHIFT 9
+#define TW_RING_MASK (TW_SLOTS_PER_RING -1)
+#define TW_TIMERS_PER_OBJECT 16
+#define LOG2_TW_TIMERS_PER_OBJECT 4
+#define TW_SUFFIX _16t_2w_512sl
+
+#include <vppinfra/tw_timer_template.h>
+
+#endif /* __included_tw_timer_16t_2w_512sl_h__ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vppinfra/tw_timer_2t_1w_2048sl.c b/src/vppinfra/tw_timer_2t_1w_2048sl.c
new file mode 100644
index 00000000..79d293e1
--- /dev/null
+++ b/src/vppinfra/tw_timer_2t_1w_2048sl.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2017 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/error.h>
+#include "tw_timer_2t_1w_2048sl.h"
+#include "tw_timer_template.c"
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vppinfra/tw_timer_2t_1w_2048sl.h b/src/vppinfra/tw_timer_2t_1w_2048sl.h
new file mode 100644
index 00000000..d1cf6d07
--- /dev/null
+++ b/src/vppinfra/tw_timer_2t_1w_2048sl.h
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2017 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.
+ */
+
+#ifndef __included_tw_timer_2t_1w_2048sl_h__
+#define __included_tw_timer_2t_1w_2048sl_h__
+
+/* ... So that a client app can create multiple wheel geometries */
+#undef TW_TIMER_WHEELS
+#undef TW_SLOTS_PER_RING
+#undef TW_RING_SHIFT
+#undef TW_RING_MASK
+#undef TW_TIMERS_PER_OBJECT
+#undef LOG2_TW_TIMERS_PER_OBJECT
+#undef TW_SUFFIX
+
+#define TW_TIMER_WHEELS 1
+#define TW_SLOTS_PER_RING 2048
+#define TW_RING_SHIFT 11
+#define TW_RING_MASK (TW_SLOTS_PER_RING -1)
+#define TW_TIMERS_PER_OBJECT 2
+#define LOG2_TW_TIMERS_PER_OBJECT 1
+#define TW_SUFFIX _2t_1w_2048sl
+
+#include <vppinfra/tw_timer_template.h>
+
+#endif /* __included_tw_timer_2t_1w_2048sl_h__ */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
diff --git a/src/vppinfra/tw_timer_template.c b/src/vppinfra/tw_timer_template.c
new file mode 100644
index 00000000..9aa5624f
--- /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:
+ */
diff --git a/src/vppinfra/tw_timer_template.h b/src/vppinfra/tw_timer_template.h
new file mode 100644
index 00000000..cf15ab8a
--- /dev/null
+++ b/src/vppinfra/tw_timer_template.h
@@ -0,0 +1,199 @@
+/*
+ * 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.
+ */
+
+#ifndef TW_SUFFIX
+#error do not include tw_timer_template.h directly
+#endif
+
+#include <vppinfra/clib.h>
+#include <vppinfra/pool.h>
+
+#ifndef _twt
+#define _twt(a,b) a##b##_t
+#define __twt(a,b) _twt(a,b)
+#define TWT(a) __twt(a,TW_SUFFIX)
+
+#define _tw(a,b) a##b
+#define __tw(a,b) _tw(a,b)
+#define TW(a) __tw(a,TW_SUFFIX)
+#endif
+
+/** @file
+    @brief TW timer template header file, do not compile directly
+
+Instantiation of tw_timer_template.h generates named structures to
+implement specific timer wheel geometries. Choices include: number of
+timer wheels (currently, 1 or 2), number of slots per ring (a power of
+two), and the number of timers per "object handle".
+
+Internally, user object/timer handles are 32-bit integers, so if one
+selects 16 timers/object (4 bits), the resulting timer wheel handle is
+limited to 2**28 objects.
+
+Here are the specific settings required to generate a single 2048 slot
+wheel which supports 2 timers per object:
+
+    #define TW_TIMER_WHEELS 1
+    #define TW_SLOTS_PER_RING 2048
+    #define TW_RING_SHIFT 11
+    #define TW_RING_MASK (TW_SLOTS_PER_RING -1)
+    #define TW_TIMERS_PER_OBJECT 2
+    #define LOG2_TW_TIMERS_PER_OBJECT 1
+    #define TW_SUFFIX _2t_1w_2048sl
+
+See tw_timer_2t_1w_2048sl.h for a complete
+example.
+
+tw_timer_template.h is not intended to be #included directly. Client
+codes can include multiple timer geometry header files, although
+extreme caution would required to use the TW and TWT macros in such a
+case.
+
+API usage example:
+
+Initialize a two-timer, single 2048-slot wheel w/ a 1-second
+timer granularity:
+
+    tw_timer_wheel_init_2t_1w_2048sl (&tm->single_wheel,
+                                     expired_timer_single_callback,
+				      1.0 / * timer interval * / );
+
+Start a timer:
+
+    handle = tw_timer_start_2t_1w_2048sl (&tm->single_wheel, elt_index,
+                                          [0 | 1] / * timer id * / ,
+                                          expiration_time_in_u32_ticks);
+
+Stop a timer:
+
+    tw_timer_stop_2t_1w_2048sl (&tm->single_wheel, handle);
+
+Expired timer callback:
+
+    static void
+    expired_timer_single_callback (u32 * expired_timers)
+    {
+    	int i;
+        u32 pool_index, timer_id;
+        tw_timer_test_elt_t *e;
+        tw_timer_test_main_t *tm = &tw_timer_test_main;
+
+        for (i = 0; i < vec_len (expired_timers);
+            {
+            pool_index = expired_timers[i] & 0x7FFFFFFF;
+            timer_id = expired_timers[i] >> 31;
+
+            ASSERT (timer_id == 1);
+
+            e = pool_elt_at_index (tm->test_elts, pool_index);
+
+            if (e->expected_to_expire != tm->single_wheel.current_tick)
+              {
+              	fformat (stdout, "[%d] expired at %d not %d\n",
+                         e - tm->test_elts, tm->single_wheel.current_tick,
+                         e->expected_to_expire);
+              }
+         pool_put (tm->test_elts, e);
+         }
+     }
+ */
+
+typedef struct
+{
+  /** next, previous pool indices */
+  u32 next;
+  u32 prev;
+#if TW_TIMER_WHEELS > 0
+  /** fast ring offset, only valid in the slow ring */
+  u16 fast_ring_offset;
+  u16 pad;
+#endif
+  /** user timer handle */
+  u32 user_handle;
+} TWT (tw_timer);
+
+/*
+ * These structures ar used by all geometries,
+ * so they need a private #include block...
+ */
+#ifndef __defined_tw_timer_wheel_slot__
+#define __defined_tw_timer_wheel_slot__
+typedef struct
+{
+  /** Listhead of timers which expire in this interval */
+  u32 head_index;
+} tw_timer_wheel_slot_t;
+typedef enum
+{
+  /** Fast timer ring ID */
+  TW_TIMER_RING_FAST,
+  /** Slow timer ring ID */
+  TW_TIMER_RING_SLOW,
+} tw_ring_index_t;
+#endif /* __defined_tw_timer_wheel_slot__ */
+
+typedef struct
+{
+  /** Timer pool */
+  TWT (tw_timer) * timers;
+
+  /** Next time the wheel should run */
+  f64 next_run_time;
+
+  /** Last time the wheel ran */
+  f64 last_run_time;
+
+  /** Timer ticks per second */
+  f64 ticks_per_second;
+
+  /** Timer interval, also needed to avoid fp divide in speed path */
+  f64 timer_interval;
+
+  /** current tick */
+  u32 current_tick;
+
+  /** current wheel indices */
+  u32 current_index[TW_TIMER_WHEELS];
+
+  /** wheel arrays */
+  tw_timer_wheel_slot_t w[TW_TIMER_WHEELS][TW_SLOTS_PER_RING];
+
+  /** expired timer callback, receives a vector of handles */
+  void (*expired_timer_callback) (u32 * expired_timer_handles);
+
+  /** vector of expired timers */
+  u32 *expired_timer_handles;
+} TWT (tw_timer_wheel);
+
+u32 TW (tw_timer_start) (TWT (tw_timer_wheel) * tw,
+			 u32 pool_index, u32 timer_id, u32 interval);
+
+void TW (tw_timer_stop) (TWT (tw_timer_wheel) * tw, u32 handle);
+
+void TW (tw_timer_wheel_init) (TWT (tw_timer_wheel) * tw,
+			       void *expired_timer_callback,
+			       f64 timer_interval);
+
+void TW (tw_timer_wheel_free) (TWT (tw_timer_wheel) * tw);
+
+void TW (tw_timer_expire_timers) (TWT (tw_timer_wheel) * tw, f64 now);
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */