X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fsvm%2Fsvm_fifo.c;h=81750b6539155c5b4eb8e94c9653ec9800ae9d4a;hb=9e61d9a1aafbaecbc7b316fd94122b80c3f99905;hp=c8fd263c09485cb26199ba3ac8e0a5423262e254;hpb=b095a3cd221a142f7d2b4897b812b2781de05d29;p=vpp.git

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index c8fd263c094..81750b65391 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -18,6 +18,7 @@
  */
 
 #include <svm/svm_fifo.h>
+#include <svm/fifo_segment.h>
 #include <vppinfra/cpu.h>
 
 CLIB_MARCH_FN (svm_fifo_copy_to_chunk, void, svm_fifo_t * f,
@@ -26,7 +27,8 @@ CLIB_MARCH_FN (svm_fifo_copy_to_chunk, void, svm_fifo_t * f,
 {
   u32 n_chunk;
 
-  ASSERT (tail_idx >= c->start_byte && tail_idx < c->start_byte + c->length);
+  ASSERT (f_pos_geq (tail_idx, c->start_byte)
+	  && f_pos_lt (tail_idx, c->start_byte + c->length));
 
   tail_idx -= c->start_byte;
   n_chunk = c->length - tail_idx;
@@ -56,7 +58,8 @@ CLIB_MARCH_FN (svm_fifo_copy_from_chunk, void, svm_fifo_t * f,
 {
   u32 n_chunk;
 
-  ASSERT (head_idx >= c->start_byte && head_idx < c->start_byte + c->length);
+  ASSERT (f_pos_geq (head_idx, c->start_byte)
+	  && f_pos_lt (head_idx, c->start_byte + c->length));
 
   head_idx -= c->start_byte;
   n_chunk = c->length - head_idx;
@@ -98,224 +101,350 @@ svm_fifo_copy_from_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c, u32 head_idx,
 						   last);
 }
 
-static inline u8
-position_lt (svm_fifo_t * f, u32 a, u32 b, u32 tail)
+static inline u32
+ooo_segment_end_pos (ooo_segment_t * s)
 {
-  return (ooo_segment_distance_from_tail (f, a, tail)
-	  < ooo_segment_distance_from_tail (f, b, tail));
+  return (s->start + s->length);
 }
 
-static inline u8
-position_leq (svm_fifo_t * f, u32 a, u32 b, u32 tail)
+void
+svm_fifo_free_ooo_data (svm_fifo_t * f)
 {
-  return (ooo_segment_distance_from_tail (f, a, tail)
-	  <= ooo_segment_distance_from_tail (f, b, tail));
+  pool_free (f->ooo_segments);
 }
 
-static inline u8
-position_gt (svm_fifo_t * f, u32 a, u32 b, u32 tail)
+static inline ooo_segment_t *
+ooo_segment_prev (svm_fifo_t * f, ooo_segment_t * s)
 {
-  return (ooo_segment_distance_from_tail (f, a, tail)
-	  > ooo_segment_distance_from_tail (f, b, tail));
+  if (s->prev == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+  return pool_elt_at_index (f->ooo_segments, s->prev);
 }
 
-static inline u32
-position_diff (svm_fifo_t * f, u32 posa, u32 posb, u32 tail)
+static inline ooo_segment_t *
+ooo_segment_next (svm_fifo_t * f, ooo_segment_t * s)
 {
-  return ooo_segment_distance_from_tail (f, posa, tail)
-    - ooo_segment_distance_from_tail (f, posb, tail);
+  if (s->next == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+  return pool_elt_at_index (f->ooo_segments, s->next);
 }
 
-static inline u32
-ooo_segment_end_pos (svm_fifo_t * f, ooo_segment_t * s)
+static inline ooo_segment_t *
+ooo_segment_alloc (svm_fifo_t * f, u32 start, u32 length)
 {
-  return s->start + s->length;
-}
+  ooo_segment_t *s;
+
+  pool_get (f->ooo_segments, s);
+
+  s->start = start;
+  s->length = length;
+  s->prev = s->next = OOO_SEGMENT_INVALID_INDEX;
 
-u8 *
-format_ooo_segment (u8 * s, va_list * args)
-{
-  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
-  ooo_segment_t *seg = va_arg (*args, ooo_segment_t *);
-  u32 normalized_start = (seg->start + f->nitems - f->tail) % f->size;
-  s = format (s, "[%u, %u], len %u, next %d, prev %d", normalized_start,
-	      (normalized_start + seg->length) % f->size, seg->length,
-	      seg->next, seg->prev);
   return s;
 }
 
-u8 *
-svm_fifo_dump_trace (u8 * s, svm_fifo_t * f)
+static inline void
+ooo_segment_free (svm_fifo_t * f, u32 index)
 {
-#if SVM_FIFO_TRACE
-  svm_fifo_trace_elem_t *seg = 0;
-  int i = 0;
+  ooo_segment_t *cur, *prev = 0, *next = 0;
+  cur = pool_elt_at_index (f->ooo_segments, index);
 
-  if (f->trace)
+  if (cur->next != OOO_SEGMENT_INVALID_INDEX)
     {
-      vec_foreach (seg, f->trace)
-      {
-	s = format (s, "{%u, %u, %u}, ", seg->offset, seg->len, seg->action);
-	i++;
-	if (i % 5 == 0)
-	  s = format (s, "\n");
-      }
-      s = format (s, "\n");
+      next = pool_elt_at_index (f->ooo_segments, cur->next);
+      next->prev = cur->prev;
     }
-  return s;
-#else
-  return 0;
-#endif
+
+  if (cur->prev != OOO_SEGMENT_INVALID_INDEX)
+    {
+      prev = pool_elt_at_index (f->ooo_segments, cur->prev);
+      prev->next = cur->next;
+    }
+  else
+    {
+      f->ooos_list_head = cur->next;
+    }
+
+  pool_put (f->ooo_segments, cur);
 }
 
-u8 *
-svm_fifo_replay (u8 * s, svm_fifo_t * f, u8 no_read, u8 verbose)
+/**
+ * Add segment to fifo's out-of-order segment list. Takes care of merging
+ * adjacent segments and removing overlapping ones.
+ */
+static void
+ooo_segment_add (svm_fifo_t * f, u32 offset, u32 head, u32 tail, u32 length)
 {
-  int i, trace_len;
-  u8 *data = 0;
-  svm_fifo_trace_elem_t *trace;
-  u32 offset;
-  svm_fifo_t *dummy_fifo;
+  ooo_segment_t *s, *new_s, *prev, *next, *it;
+  u32 new_index, s_end_pos, s_index;
+  u32 offset_pos, offset_end_pos;
 
-  if (!f)
-    return s;
+  ASSERT (offset + length <= f_free_count (f, head, tail));
 
-#if SVM_FIFO_TRACE
-  trace = f->trace;
-  trace_len = vec_len (trace);
-#else
-  trace = 0;
-  trace_len = 0;
-#endif
+  offset_pos = tail + offset;
+  offset_end_pos = tail + offset + length;
 
-  dummy_fifo = svm_fifo_create (f->size);
-  clib_memset (f->head_chunk->data, 0xFF, f->nitems);
-  vec_validate (data, f->nitems);
-  for (i = 0; i < vec_len (data); i++)
-    data[i] = i;
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 
-  for (i = 0; i < trace_len; i++)
+  if (f->ooos_list_head == OOO_SEGMENT_INVALID_INDEX)
     {
-      offset = trace[i].offset;
-      if (trace[i].action == 1)
-	{
-	  if (verbose)
-	    s = format (s, "adding [%u, %u]:", trace[i].offset,
-			(trace[i].offset + trace[i].len) % dummy_fifo->size);
-	  svm_fifo_enqueue_with_offset (dummy_fifo, trace[i].offset,
-					trace[i].len, &data[offset]);
-	}
-      else if (trace[i].action == 2)
+      s = ooo_segment_alloc (f, offset_pos, length);
+      f->ooos_list_head = s - f->ooo_segments;
+      f->ooos_newest = f->ooos_list_head;
+      return;
+    }
+
+  /* Find first segment that starts after new segment */
+  s = pool_elt_at_index (f->ooo_segments, f->ooos_list_head);
+  while (s->next != OOO_SEGMENT_INVALID_INDEX
+	 && f_pos_lt (s->start, offset_pos))
+    s = pool_elt_at_index (f->ooo_segments, s->next);
+
+  /* If we have a previous and we overlap it, use it as starting point */
+  prev = ooo_segment_prev (f, s);
+  if (prev && f_pos_leq (offset_pos, ooo_segment_end_pos (prev)))
+    {
+      s = prev;
+      s_end_pos = ooo_segment_end_pos (s);
+
+      /* Since we have previous, offset start position cannot be smaller
+       * than prev->start. Check tail */
+      ASSERT (f_pos_lt (s->start, offset_pos));
+      goto check_tail;
+    }
+
+  s_index = s - f->ooo_segments;
+  s_end_pos = ooo_segment_end_pos (s);
+
+  /* No overlap, add before current segment */
+  if (f_pos_lt (offset_end_pos, s->start))
+    {
+      new_s = ooo_segment_alloc (f, offset_pos, length);
+      new_index = new_s - f->ooo_segments;
+
+      /* Pool might've moved, get segment again */
+      s = pool_elt_at_index (f->ooo_segments, s_index);
+      if (s->prev != OOO_SEGMENT_INVALID_INDEX)
 	{
-	  if (verbose)
-	    s = format (s, "adding [%u, %u]:", 0, trace[i].len);
-	  svm_fifo_enqueue_nowait (dummy_fifo, trace[i].len, &data[offset]);
+	  new_s->prev = s->prev;
+	  prev = pool_elt_at_index (f->ooo_segments, new_s->prev);
+	  prev->next = new_index;
 	}
-      else if (!no_read)
+      else
 	{
-	  if (verbose)
-	    s = format (s, "read: %u", trace[i].len);
-	  svm_fifo_dequeue_drop (dummy_fifo, trace[i].len);
+	  /* New head */
+	  f->ooos_list_head = new_index;
 	}
-      if (verbose)
-	s = format (s, "%U", format_svm_fifo, dummy_fifo, 1);
+
+      new_s->next = s_index;
+      s->prev = new_index;
+      f->ooos_newest = new_index;
+      return;
     }
+  /* No overlap, add after current segment */
+  else if (f_pos_gt (offset_pos, s_end_pos))
+    {
+      new_s = ooo_segment_alloc (f, offset_pos, length);
+      new_index = new_s - f->ooo_segments;
 
-  s = format (s, "result: %U", format_svm_fifo, dummy_fifo, 1);
+      /* Pool might've moved, get segment again */
+      s = pool_elt_at_index (f->ooo_segments, s_index);
 
-  return s;
-}
+      /* Needs to be last */
+      ASSERT (s->next == OOO_SEGMENT_INVALID_INDEX);
 
-u8 *
-format_ooo_list (u8 * s, va_list * args)
-{
-  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
-  u32 indent = va_arg (*args, u32);
-  u32 ooo_segment_index = f->ooos_list_head;
-  ooo_segment_t *seg;
+      new_s->prev = s_index;
+      s->next = new_index;
+      f->ooos_newest = new_index;
 
-  while (ooo_segment_index != OOO_SEGMENT_INVALID_INDEX)
+      return;
+    }
+
+  /*
+   * Merge needed
+   */
+
+  /* Merge at head */
+  if (f_pos_lt (offset_pos, s->start))
     {
-      seg = pool_elt_at_index (f->ooo_segments, ooo_segment_index);
-      s = format (s, "%U%U\n", format_white_space, indent, format_ooo_segment,
-		  f, seg);
-      ooo_segment_index = seg->next;
+      s->start = offset_pos;
+      s->length = s_end_pos - s->start;
+      f->ooos_newest = s - f->ooo_segments;
     }
 
-  return s;
+check_tail:
+
+  /* Overlapping tail */
+  if (f_pos_gt (offset_end_pos, s_end_pos))
+    {
+      s->length = offset_end_pos - s->start;
+
+      /* Remove the completely overlapped segments in the tail */
+      it = ooo_segment_next (f, s);
+      while (it && f_pos_leq (ooo_segment_end_pos (it), offset_end_pos))
+	{
+	  next = ooo_segment_next (f, it);
+	  ooo_segment_free (f, it - f->ooo_segments);
+	  it = next;
+	}
+
+      /* If partial overlap with last, merge */
+      if (it && f_pos_leq (it->start, offset_end_pos))
+	{
+	  s->length = ooo_segment_end_pos (it) - s->start;
+	  ooo_segment_free (f, it - f->ooo_segments);
+	}
+      f->ooos_newest = s - f->ooo_segments;
+    }
 }
 
-u8 *
-format_svm_fifo (u8 * s, va_list * args)
+/**
+ * Removes segments that can now be enqueued because the fifo's tail has
+ * advanced. Returns the number of bytes added to tail.
+ */
+static int
+ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued, u32 * tail)
 {
-  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
-  int verbose = va_arg (*args, int);
-  u32 indent;
+  u32 s_index, bytes = 0;
+  ooo_segment_t *s;
+  i32 diff;
 
-  if (!s)
-    return s;
+  s = pool_elt_at_index (f->ooo_segments, f->ooos_list_head);
+  diff = *tail - s->start;
 
-  indent = format_get_indent (s);
-  s = format (s, "cursize %u nitems %u has_event %d\n",
-	      svm_fifo_max_dequeue (f), f->nitems, f->has_event);
-  s = format (s, "%Uhead %u tail %u segment manager %u\n", format_white_space,
-	      indent, (f->head % f->size), (f->tail % f->size),
-	      f->segment_manager);
+  ASSERT (diff != n_bytes_enqueued);
 
-  if (verbose > 1)
-    s = format (s, "%Uvpp session %d thread %d app session %d thread %d\n",
-		format_white_space, indent, f->master_session_index,
-		f->master_thread_index, f->client_session_index,
-		f->client_thread_index);
+  if (diff > n_bytes_enqueued)
+    return 0;
 
-  if (verbose)
+  /* If last tail update overlaps one/multiple ooo segments, remove them */
+  while (0 <= diff && diff < n_bytes_enqueued)
     {
-      s = format (s, "%Uooo pool %d active elts newest %u\n",
-		  format_white_space, indent, pool_elts (f->ooo_segments),
-		  f->ooos_newest);
-      if (svm_fifo_has_ooo_data (f))
-	s = format (s, " %U", format_ooo_list, f, indent, verbose);
+      s_index = s - f->ooo_segments;
+
+      /* Segment end is beyond the tail. Advance tail and remove segment */
+      if (s->length > diff)
+	{
+	  bytes = s->length - diff;
+	  *tail = *tail + bytes;
+	  ooo_segment_free (f, s_index);
+	  break;
+	}
+
+      /* If we have next go on */
+      if (s->next != OOO_SEGMENT_INVALID_INDEX)
+	{
+	  s = pool_elt_at_index (f->ooo_segments, s->next);
+	  diff = *tail - s->start;
+	  ooo_segment_free (f, s_index);
+	}
+      /* End of search */
+      else
+	{
+	  ooo_segment_free (f, s_index);
+	  break;
+	}
     }
+
+  ASSERT (bytes <= f->size);
+  return bytes;
+}
+
+__clib_unused static ooo_segment_t *
+ooo_segment_last (svm_fifo_t * f)
+{
+  ooo_segment_t *s;
+
+  if (f->ooos_list_head == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+
+  s = svm_fifo_first_ooo_segment (f);
+  while (s->next != OOO_SEGMENT_INVALID_INDEX)
+    s = pool_elt_at_index (f->ooo_segments, s->next);
   return s;
 }
 
 void
 svm_fifo_init (svm_fifo_t * f, u32 size)
 {
+  svm_fifo_chunk_t *c, *prev;
+  u32 min_alloc;
+
   f->size = size;
-  /*
-   * usable size of the fifo set to rounded_data_size - 1
-   * to differentiate between free fifo and empty fifo.
-   */
-  f->nitems = f->size - 1;
   f->ooos_list_head = OOO_SEGMENT_INVALID_INDEX;
-  f->ct_session_index = SVM_FIFO_INVALID_SESSION_INDEX;
   f->segment_index = SVM_FIFO_INVALID_INDEX;
   f->refcnt = 1;
-  f->default_chunk.start_byte = 0;
-  f->default_chunk.length = f->size;
-  f->default_chunk.next = f->start_chunk = f->end_chunk = &f->default_chunk;
-  f->head_chunk = f->tail_chunk = f->ooo_enq = f->ooo_deq = f->start_chunk;
+  f->head = f->tail = f->flags = 0;
+  f->head_chunk = f->tail_chunk = f->start_chunk;
+  f->ooo_deq = f->ooo_enq = 0;
+
+  min_alloc = size > 32 << 10 ? size >> 3 : 4096;
+  min_alloc = clib_min (min_alloc, 64 << 10);
+  f->min_alloc = min_alloc;
+
+  /*
+   * Initialize chunks
+   */
+  f->start_chunk->start_byte = 0;
+  prev = f->start_chunk;
+  c = prev->next;
+
+  while (c)
+    {
+      c->start_byte = prev->start_byte + prev->length;
+      prev = c;
+      c = c->next;
+    }
+}
+
+void
+svm_fifo_init_ooo_lookup (svm_fifo_t * f, u8 ooo_type)
+{
+  if (ooo_type == 0)
+    {
+      ASSERT (!rb_tree_is_init (&f->ooo_enq_lookup));
+      rb_tree_init (&f->ooo_enq_lookup);
+    }
+  else
+    {
+      ASSERT (!rb_tree_is_init (&f->ooo_deq_lookup));
+      rb_tree_init (&f->ooo_deq_lookup);
+    }
 }
 
 /**
  * Creates a fifo in the current heap. Fails vs blow up the process
  */
 svm_fifo_t *
-svm_fifo_create (u32 data_size_in_bytes)
+svm_fifo_alloc (u32 data_size_in_bytes)
 {
-  svm_fifo_t *f;
   u32 rounded_data_size;
+  svm_fifo_chunk_t *c;
+  svm_fifo_t *f;
 
-  /* always round fifo data size to the next highest power-of-two */
-  rounded_data_size = (1 << (max_log2 (data_size_in_bytes)));
-  f = clib_mem_alloc_aligned_or_null (sizeof (*f) + rounded_data_size,
-				      CLIB_CACHE_LINE_BYTES);
+  f = clib_mem_alloc_aligned_or_null (sizeof (*f), CLIB_CACHE_LINE_BYTES);
   if (f == 0)
     return 0;
 
   clib_memset (f, 0, sizeof (*f));
-  svm_fifo_init (f, data_size_in_bytes);
+
+  /* always round fifo data size to the next highest power-of-two */
+  rounded_data_size = (1 << (max_log2 (data_size_in_bytes)));
+  c = clib_mem_alloc_aligned_or_null (sizeof (*c) + rounded_data_size,
+				      CLIB_CACHE_LINE_BYTES);
+  if (!c)
+    {
+      clib_mem_free (f);
+      return 0;
+    }
+
+  clib_memset (c, 0, sizeof (*c));
+  c->start_byte = 0;
+  c->length = data_size_in_bytes;
+  c->enq_rb_index = RBTREE_TNIL_INDEX;
+  c->deq_rb_index = RBTREE_TNIL_INDEX;
+  f->start_chunk = f->end_chunk = c;
+
   return f;
 }
 
@@ -340,160 +469,289 @@ svm_fifo_chunk_alloc (u32 size)
   return c;
 }
 
-static inline void
-svm_fifo_size_update (svm_fifo_t * f, svm_fifo_chunk_t * c)
+/**
+ * Find chunk for given byte position
+ *
+ * @param f	fifo
+ * @param pos	normalized position in fifo
+ *
+ * @return chunk that includes given position or 0
+ */
+static svm_fifo_chunk_t *
+svm_fifo_find_chunk (svm_fifo_t * f, u32 pos)
 {
-  svm_fifo_chunk_t *prev;
-  u32 add_bytes = 0;
+  svm_fifo_chunk_t *c;
 
-  if (!c)
-    return;
+  c = f->start_chunk;
+  while (c && !f_chunk_includes_pos (c, pos))
+    c = c->next;
 
-  f->end_chunk->next = c;
-  while (c)
+  return c;
+}
+
+static svm_fifo_chunk_t *
+svm_fifo_find_next_chunk (svm_fifo_t * f, svm_fifo_chunk_t * start, u32 pos)
+{
+  svm_fifo_chunk_t *c;
+
+  ASSERT (start != 0);
+
+  c = start;
+  while (c && !f_chunk_includes_pos (c, pos))
+    c = c->next;
+
+  return c;
+}
+
+u32
+svm_fifo_max_read_chunk (svm_fifo_t * f)
+{
+  u32 head, tail, end_chunk;
+
+  f_load_head_tail_cons (f, &head, &tail);
+  ASSERT (!f->head_chunk || f_chunk_includes_pos (f->head_chunk, head));
+
+  if (!f->head_chunk)
     {
-      add_bytes += c->length;
-      prev = c;
-      c = c->next;
+      f->head_chunk = svm_fifo_find_chunk (f, head);
+      if (PREDICT_FALSE (!f->head_chunk))
+	return 0;
     }
-  f->end_chunk = prev;
-  prev->next = f->start_chunk;
-  f->size += add_bytes;
-  f->nitems = f->size - 1;
-  f->new_chunks = 0;
+
+  end_chunk = f_chunk_end (f->head_chunk);
+
+  return f_pos_lt (end_chunk, tail) ? end_chunk - head : tail - head;
 }
 
-static void
-svm_fifo_try_size_update (svm_fifo_t * f, u32 new_head)
+u32
+svm_fifo_max_write_chunk (svm_fifo_t * f)
 {
-  if (new_head % f->size > f->tail % f->size)
-    return;
+  u32 head, tail;
 
-  svm_fifo_size_update (f, f->new_chunks);
-  f->flags &= ~SVM_FIFO_F_SIZE_UPDATE;
+  f_load_head_tail_prod (f, &head, &tail);
+  ASSERT (!f->tail_chunk || f_chunk_includes_pos (f->tail_chunk, tail));
+
+  return f->tail_chunk ? f_chunk_end (f->tail_chunk) - tail : 0;
 }
 
-void
-svm_fifo_add_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c)
+static rb_node_t *
+f_find_node_rbtree (rb_tree_t * rt, u32 pos)
 {
-  svm_fifo_chunk_t *cur, *prev;
+  rb_node_t *cur, *prev;
+
+  cur = rb_node (rt, rt->root);
+  if (PREDICT_FALSE (rb_node_is_tnil (rt, cur)))
+    return 0;
 
-  /* Initialize rbtree if needed and add default chunk to it */
-  if (!(f->flags & SVM_FIFO_F_MULTI_CHUNK))
+  while (pos != cur->key)
     {
-      rb_tree_init (&f->chunk_lookup);
-      rb_tree_add2 (&f->chunk_lookup, 0, pointer_to_uword (f->start_chunk));
-      f->flags |= SVM_FIFO_F_MULTI_CHUNK;
+      prev = cur;
+      if (f_pos_lt (pos, cur->key))
+	{
+	  cur = rb_node_left (rt, cur);
+	  if (rb_node_is_tnil (rt, cur))
+	    {
+	      cur = rb_tree_predecessor (rt, prev);
+	      break;
+	    }
+	}
+      else
+	{
+	  cur = rb_node_right (rt, cur);
+	  if (rb_node_is_tnil (rt, cur))
+	    {
+	      cur = prev;
+	      break;
+	    }
+	}
     }
 
-  /* Initialize chunks and add to lookup rbtree. Expectation is that this is
-   * called with the heap where the rbtree's pool is pushed. */
-  cur = c;
-  if (f->new_chunks)
+  if (rb_node_is_tnil (rt, cur))
+    return 0;
+
+  return cur;
+}
+
+static svm_fifo_chunk_t *
+f_find_chunk_rbtree (rb_tree_t * rt, u32 pos)
+{
+  svm_fifo_chunk_t *c;
+  rb_node_t *n;
+
+  if (!rb_tree_is_init (rt))
+    return 0;
+
+  n = f_find_node_rbtree (rt, pos);
+  if (!n)
+    return 0;
+  c = uword_to_pointer (n->opaque, svm_fifo_chunk_t *);
+  if (f_chunk_includes_pos (c, pos))
+    return c;
+
+  return 0;
+}
+
+static void
+f_update_ooo_enq (svm_fifo_t * f, u32 start_pos, u32 end_pos)
+{
+  rb_tree_t *rt = &f->ooo_enq_lookup;
+  svm_fifo_chunk_t *c;
+  rb_node_t *cur;
+
+  /* Use linear search if rbtree is not initialized */
+  if (PREDICT_FALSE (!rb_tree_is_init (rt)))
+    {
+      f->ooo_enq = svm_fifo_find_next_chunk (f, f->tail_chunk, start_pos);
+      return;
+    }
+
+  if (rt->root == RBTREE_TNIL_INDEX)
     {
-      prev = f->new_chunks;
-      while (prev->next)
-	prev = prev->next;
-      prev->next = c;
+      c = f->tail_chunk;
+      ASSERT (c->enq_rb_index == RBTREE_TNIL_INDEX);
+      c->enq_rb_index = rb_tree_add_custom (rt, c->start_byte,
+					    pointer_to_uword (c), f_pos_lt);
     }
   else
-    prev = f->end_chunk;
+    {
+      cur = f_find_node_rbtree (rt, start_pos);
+      c = uword_to_pointer (cur->opaque, svm_fifo_chunk_t *);
+      ASSERT (f_pos_leq (c->start_byte, start_pos));
+    }
 
-  while (cur)
+  if (f_chunk_includes_pos (c, start_pos))
+    f->ooo_enq = c;
+
+  if (f_chunk_includes_pos (c, end_pos))
+    return;
+
+  do
     {
-      cur->start_byte = prev->start_byte + prev->length;
-      rb_tree_add2 (&f->chunk_lookup, cur->start_byte,
-		    pointer_to_uword (cur));
-      prev = cur;
-      cur = cur->next;
+      c = c->next;
+      if (!c || c->enq_rb_index != RBTREE_TNIL_INDEX)
+	break;
+
+      c->enq_rb_index = rb_tree_add_custom (rt, c->start_byte,
+					    pointer_to_uword (c), f_pos_lt);
+
+      if (f_chunk_includes_pos (c, start_pos))
+	f->ooo_enq = c;
     }
+  while (!f_chunk_includes_pos (c, end_pos));
+}
 
-  /* If fifo is not wrapped, update the size now */
-  if (!svm_fifo_is_wrapped (f))
+static void
+f_update_ooo_deq (svm_fifo_t * f, u32 start_pos, u32 end_pos)
+{
+  rb_tree_t *rt = &f->ooo_deq_lookup;
+  rb_node_t *cur;
+  svm_fifo_chunk_t *c;
+
+  /* Use linear search if rbtree is not initialized  */
+  if (PREDICT_FALSE (!rb_tree_is_init (rt)))
     {
-      ASSERT (!f->new_chunks);
-      svm_fifo_size_update (f, c);
+      f->ooo_deq = svm_fifo_find_chunk (f, start_pos);
       return;
     }
 
-  /* Postpone size update */
-  if (!f->new_chunks)
+  if (rt->root == RBTREE_TNIL_INDEX)
+    {
+      c = f->start_chunk;
+      ASSERT (c->deq_rb_index == RBTREE_TNIL_INDEX);
+      c->deq_rb_index = rb_tree_add_custom (rt, c->start_byte,
+					    pointer_to_uword (c), f_pos_lt);
+    }
+  else
+    {
+      cur = f_find_node_rbtree (rt, start_pos);
+      c = uword_to_pointer (cur->opaque, svm_fifo_chunk_t *);
+      ASSERT (f_pos_leq (c->start_byte, start_pos));
+    }
+
+  if (f_chunk_includes_pos (c, start_pos))
+    f->ooo_deq = c;
+
+  if (f_chunk_includes_pos (c, end_pos))
+    return;
+
+  do
     {
-      f->new_chunks = c;
-      f->flags |= SVM_FIFO_F_SIZE_UPDATE;
+      c = c->next;
+      if (!c || c->deq_rb_index != RBTREE_TNIL_INDEX)
+	break;
+
+      c->deq_rb_index = rb_tree_add_custom (rt, c->start_byte,
+					    pointer_to_uword (c), f_pos_lt);
+
+      if (f_chunk_includes_pos (c, start_pos))
+	f->ooo_deq = c;
     }
+  while (!f_chunk_includes_pos (c, end_pos));
 }
 
-static inline u8
-svm_fifo_chunk_includes_pos (svm_fifo_chunk_t * c, u32 pos)
+static svm_fifo_chunk_t *
+f_lookup_clear_enq_chunks (svm_fifo_t * f, svm_fifo_chunk_t * start,
+			   u32 end_pos)
 {
-  return (pos >= c->start_byte && pos < c->start_byte + c->length);
-}
+  rb_tree_t *rt = &f->ooo_enq_lookup;
+  svm_fifo_chunk_t *c;
+  rb_node_t *n;
+
+  c = start;
+  while (c && !f_chunk_includes_pos (c, end_pos))
+    {
+      if (c->enq_rb_index != RBTREE_TNIL_INDEX)
+	{
+	  n = rb_node (rt, c->enq_rb_index);
+	  rb_tree_del_node (rt, n);
+	  c->enq_rb_index = RBTREE_TNIL_INDEX;
+	}
+
+      c = c->next;
+    }
+
+  /* No ooo segments left, so make sure the current chunk
+   * is not tracked in the enq rbtree */
+  if (f->ooos_list_head == OOO_SEGMENT_INVALID_INDEX
+      && c && c->enq_rb_index != RBTREE_TNIL_INDEX)
+    {
+      n = rb_node (rt, c->enq_rb_index);
+      rb_tree_del_node (rt, n);
+      c->enq_rb_index = RBTREE_TNIL_INDEX;
+    }
+
+  return c;
+}
 
-/**
- * Find chunk for given byte position
- *
- * @param f	fifo
- * @param pos	normalized position in fifo
- *
- * @return chunk that includes given position or 0
- */
 static svm_fifo_chunk_t *
-svm_fifo_find_chunk (svm_fifo_t * f, u32 pos)
+f_lookup_clear_deq_chunks (svm_fifo_t * f, svm_fifo_chunk_t * start,
+			   u32 end_pos)
 {
-  rb_tree_t *rt = &f->chunk_lookup;
-  rb_node_t *cur, *prev;
+  rb_tree_t *rt = &f->ooo_deq_lookup;
   svm_fifo_chunk_t *c;
+  rb_node_t *n;
 
-  cur = rb_node (rt, rt->root);
-  while (pos != cur->key)
+  c = start;
+  while (c && !f_chunk_includes_pos (c, end_pos))
     {
-      prev = cur;
-      if (pos < cur->key)
-	cur = rb_node_left (rt, cur);
-      else
-	cur = rb_node_right (rt, cur);
-
-      if (rb_node_is_tnil (rt, cur))
+      if (c->deq_rb_index != RBTREE_TNIL_INDEX)
 	{
-	  /* Hit tnil as a left child. Find predecessor */
-	  if (pos < prev->key)
-	    {
-	      cur = rb_tree_predecessor (rt, prev);
-	      c = uword_to_pointer (cur->opaque, svm_fifo_chunk_t *);
-	      if (svm_fifo_chunk_includes_pos (c, pos))
-		return c;
-	      return 0;
-	    }
-	  /* Hit tnil as a right child. Check if this is the one, otherwise
-	   * search for successor */
-	  c = uword_to_pointer (prev->opaque, svm_fifo_chunk_t *);
-	  if (svm_fifo_chunk_includes_pos (c, pos))
-	    return c;
-
-	  cur = rb_tree_successor (rt, prev);
-	  c = uword_to_pointer (cur->opaque, svm_fifo_chunk_t *);
-	  if (svm_fifo_chunk_includes_pos (c, pos))
-	    return c;
-	  return 0;
+	  n = rb_node (rt, c->deq_rb_index);
+	  rb_tree_del_node (rt, n);
+	  c->deq_rb_index = RBTREE_TNIL_INDEX;
 	}
+
+      c = c->next;
     }
 
-  if (!rb_node_is_tnil (rt, cur))
-    return uword_to_pointer (cur->opaque, svm_fifo_chunk_t *);
-  return 0;
+  return c;
 }
 
 void
 svm_fifo_free_chunk_lookup (svm_fifo_t * f)
 {
-  rb_tree_free_nodes (&f->chunk_lookup);
-}
-
-void
-svm_fifo_free_ooo_data (svm_fifo_t * f)
-{
-  pool_free (f->ooo_segments);
+  rb_tree_free_nodes (&f->ooo_enq_lookup);
+  rb_tree_free_nodes (&f->ooo_deq_lookup);
 }
 
 void
@@ -509,328 +767,245 @@ svm_fifo_free (svm_fifo_t * f)
     }
 }
 
-always_inline ooo_segment_t *
-ooo_segment_new (svm_fifo_t * f, u32 start, u32 length)
+void
+svm_fifo_overwrite_head (svm_fifo_t * f, u8 * src, u32 len)
 {
-  ooo_segment_t *s;
-
-  pool_get (f->ooo_segments, s);
-
-  s->start = start;
-  s->length = length;
-
-  s->prev = s->next = OOO_SEGMENT_INVALID_INDEX;
+  u32 n_chunk;
+  u32 head, tail, head_idx;
+  svm_fifo_chunk_t *c;
 
-  return s;
-}
+  ASSERT (len <= f->size);
 
-always_inline void
-ooo_segment_del (svm_fifo_t * f, u32 index)
-{
-  ooo_segment_t *cur, *prev = 0, *next = 0;
-  cur = pool_elt_at_index (f->ooo_segments, index);
+  f_load_head_tail_cons (f, &head, &tail);
 
-  if (cur->next != OOO_SEGMENT_INVALID_INDEX)
-    {
-      next = pool_elt_at_index (f->ooo_segments, cur->next);
-      next->prev = cur->prev;
-    }
+  if (!f->head_chunk)
+    f->head_chunk = svm_fifo_find_chunk (f, head);
 
-  if (cur->prev != OOO_SEGMENT_INVALID_INDEX)
-    {
-      prev = pool_elt_at_index (f->ooo_segments, cur->prev);
-      prev->next = cur->next;
-    }
+  c = f->head_chunk;
+  head_idx = head - c->start_byte;
+  n_chunk = c->length - head_idx;
+  if (len <= n_chunk)
+    clib_memcpy_fast (&c->data[head_idx], src, len);
   else
     {
-      f->ooos_list_head = cur->next;
+      ASSERT (len - n_chunk <= c->next->length);
+      clib_memcpy_fast (&c->data[head_idx], src, n_chunk);
+      clib_memcpy_fast (&c->next->data[0], src + n_chunk, len - n_chunk);
     }
-
-  pool_put (f->ooo_segments, cur);
 }
 
-/**
- * Add segment to fifo's out-of-order segment list. Takes care of merging
- * adjacent segments and removing overlapping ones.
- */
-static void
-ooo_segment_add (svm_fifo_t * f, u32 offset, u32 head, u32 tail, u32 length)
+static int
+f_try_chunk_alloc (svm_fifo_t * f, u32 head, u32 tail, u32 len)
 {
-  ooo_segment_t *s, *new_s, *prev, *next, *it;
-  u32 new_index, s_end_pos, s_index;
-  u32 offset_pos, offset_end_pos;
+  svm_fifo_chunk_t *c, *cur, *prev;
+  u32 alloc_size, free_alloced;
 
-  ASSERT (offset + length <= ooo_segment_distance_from_tail (f, head, tail)
-	  || head == tail);
-
-  offset_pos = tail + offset;
-  offset_end_pos = tail + offset + length;
+  free_alloced = f_chunk_end (f->end_chunk) - tail;
+  ASSERT (free_alloced < len);
 
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+  alloc_size = clib_min (f->min_alloc, f->size - (tail - head));
+  alloc_size = clib_max (alloc_size, len - free_alloced);
 
-  if (f->ooos_list_head == OOO_SEGMENT_INVALID_INDEX)
-    {
-      s = ooo_segment_new (f, offset_pos, length);
-      f->ooos_list_head = s - f->ooo_segments;
-      f->ooos_newest = f->ooos_list_head;
-      return;
-    }
+  c = fsh_alloc_chunk (f->fs_hdr, f->slice_index, alloc_size);
+  if (PREDICT_FALSE (!c))
+    return -1;
 
-  /* Find first segment that starts after new segment */
-  s = pool_elt_at_index (f->ooo_segments, f->ooos_list_head);
-  while (s->next != OOO_SEGMENT_INVALID_INDEX
-	 && position_lt (f, s->start, offset_pos, tail))
-    s = pool_elt_at_index (f->ooo_segments, s->next);
+  cur = c;
+  prev = f->end_chunk;
 
-  /* If we have a previous and we overlap it, use it as starting point */
-  prev = ooo_segment_get_prev (f, s);
-  if (prev
-      && position_leq (f, offset_pos, ooo_segment_end_pos (f, prev), tail))
+  while (cur)
     {
-      s = prev;
-      s_end_pos = ooo_segment_end_pos (f, s);
+      cur->start_byte = prev->start_byte + prev->length;
+      cur->enq_rb_index = RBTREE_TNIL_INDEX;
+      cur->deq_rb_index = RBTREE_TNIL_INDEX;
 
-      /* Since we have previous, offset start position cannot be smaller
-       * than prev->start. Check tail */
-      ASSERT (position_lt (f, s->start, offset_pos, tail));
-      goto check_tail;
+      prev = cur;
+      cur = cur->next;
     }
 
-  s_index = s - f->ooo_segments;
-  s_end_pos = ooo_segment_end_pos (f, s);
+  prev->next = 0;
+  f->end_chunk->next = c;
+  f->end_chunk = prev;
 
-  /* No overlap, add before current segment */
-  if (position_lt (f, offset_end_pos, s->start, tail))
-    {
-      new_s = ooo_segment_new (f, offset_pos, length);
-      new_index = new_s - f->ooo_segments;
+  if (!f->tail_chunk)
+    f->tail_chunk = c;
 
-      /* Pool might've moved, get segment again */
-      s = pool_elt_at_index (f->ooo_segments, s_index);
-      if (s->prev != OOO_SEGMENT_INVALID_INDEX)
-	{
-	  new_s->prev = s->prev;
-	  prev = pool_elt_at_index (f->ooo_segments, new_s->prev);
-	  prev->next = new_index;
-	}
-      else
-	{
-	  /* New head */
-	  f->ooos_list_head = new_index;
-	}
+  return 0;
+}
 
-      new_s->next = s_index;
-      s->prev = new_index;
-      f->ooos_newest = new_index;
-      return;
-    }
-  /* No overlap, add after current segment */
-  else if (position_gt (f, offset_pos, s_end_pos, tail))
-    {
-      new_s = ooo_segment_new (f, offset_pos, length);
-      new_index = new_s - f->ooo_segments;
+int
+svm_fifo_enqueue (svm_fifo_t * f, u32 len, const u8 * src)
+{
+  u32 tail, head, free_count;
+  svm_fifo_chunk_t *old_tail_c;
 
-      /* Pool might've moved, get segment again */
-      s = pool_elt_at_index (f->ooo_segments, s_index);
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 
-      /* Needs to be last */
-      ASSERT (s->next == OOO_SEGMENT_INVALID_INDEX);
+  f_load_head_tail_prod (f, &head, &tail);
 
-      new_s->prev = s_index;
-      s->next = new_index;
-      f->ooos_newest = new_index;
+  /* free space in fifo can only increase during enqueue: SPSC */
+  free_count = f_free_count (f, head, tail);
 
-      return;
-    }
+  if (PREDICT_FALSE (free_count == 0))
+    return SVM_FIFO_EFULL;
 
-  /*
-   * Merge needed
-   */
+  /* number of bytes we're going to copy */
+  len = clib_min (free_count, len);
 
-  /* Merge at head */
-  if (position_lt (f, offset_pos, s->start, tail))
+  if (f_pos_gt (tail + len, f_chunk_end (f->end_chunk)))
     {
-      s->start = offset_pos;
-      s->length = position_diff (f, s_end_pos, s->start, tail);
-      f->ooos_newest = s - f->ooo_segments;
+      if (PREDICT_FALSE (f_try_chunk_alloc (f, head, tail, len)))
+	{
+	  len = f_chunk_end (f->end_chunk) - tail;
+	  if (!len)
+	    return SVM_FIFO_EGROW;
+	}
     }
 
-check_tail:
+  old_tail_c = f->tail_chunk;
 
-  /* Overlapping tail */
-  if (position_gt (f, offset_end_pos, s_end_pos, tail))
-    {
-      s->length = position_diff (f, offset_end_pos, s->start, tail);
+  svm_fifo_copy_to_chunk (f, f->tail_chunk, tail, src, len, &f->tail_chunk);
+  tail = tail + len;
 
-      /* Remove the completely overlapped segments in the tail */
-      it = ooo_segment_next (f, s);
-      while (it && position_leq (f, ooo_segment_end_pos (f, it),
-				 offset_end_pos, tail))
-	{
-	  next = ooo_segment_next (f, it);
-	  ooo_segment_del (f, it - f->ooo_segments);
-	  it = next;
-	}
+  svm_fifo_trace_add (f, head, len, 2);
 
-      /* If partial overlap with last, merge */
-      if (it && position_leq (f, it->start, offset_end_pos, tail))
-	{
-	  s->length = position_diff (f, ooo_segment_end_pos (f, it),
-				     s->start, tail);
-	  ooo_segment_del (f, it - f->ooo_segments);
-	}
-      f->ooos_newest = s - f->ooo_segments;
+  /* collect out-of-order segments */
+  if (PREDICT_FALSE (f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX))
+    {
+      len += ooo_segment_try_collect (f, len, &tail);
+      /* Tail chunk might've changed even if nothing was collected */
+      f->tail_chunk = f_lookup_clear_enq_chunks (f, old_tail_c, tail);
+      f->ooo_enq = 0;
     }
+
+  /* store-rel: producer owned index (paired with load-acq in consumer) */
+  clib_atomic_store_rel_n (&f->tail, tail);
+
+  return len;
 }
 
 /**
- * Removes segments that can now be enqueued because the fifo's tail has
- * advanced. Returns the number of bytes added to tail.
+ * Enqueue a future segment.
+ *
+ * Two choices: either copies the entire segment, or copies nothing
+ * Returns 0 of the entire segment was copied
+ * Returns -1 if none of the segment was copied due to lack of space
  */
-static int
-ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued, u32 * tail)
+int
+svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset, u32 len, u8 * src)
 {
-  ooo_segment_t *s;
-  u32 index, bytes = 0;
-  i32 diff;
+  u32 tail, head, free_count, enq_pos;
 
-  s = pool_elt_at_index (f->ooo_segments, f->ooos_list_head);
-  diff = ooo_segment_distance_to_tail (f, s->start, *tail);
+  f_load_head_tail_prod (f, &head, &tail);
 
-  ASSERT (diff != n_bytes_enqueued);
+  /* free space in fifo can only increase during enqueue: SPSC */
+  free_count = f_free_count (f, head, tail);
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 
-  if (diff > n_bytes_enqueued)
-    return 0;
+  /* will this request fit? */
+  if ((len + offset) > free_count)
+    return SVM_FIFO_EFULL;
 
-  /* If last tail update overlaps one/multiple ooo segments, remove them */
-  while (0 <= diff && diff < n_bytes_enqueued)
+  enq_pos = tail + offset;
+
+  if (f_pos_gt (enq_pos + len, f_chunk_end (f->end_chunk)))
     {
-      index = s - f->ooo_segments;
+      if (PREDICT_FALSE (f_try_chunk_alloc (f, head, tail, offset + len)))
+	return SVM_FIFO_EGROW;
+    }
 
-      /* Segment end is beyond the tail. Advance tail and remove segment */
-      if (s->length > diff)
-	{
-	  bytes = s->length - diff;
-	  *tail = *tail + bytes;
-	  ooo_segment_del (f, index);
-	  break;
-	}
+  svm_fifo_trace_add (f, offset, len, 1);
+  ooo_segment_add (f, offset, head, tail, len);
 
-      /* If we have next go on */
-      if (s->next != OOO_SEGMENT_INVALID_INDEX)
-	{
-	  s = pool_elt_at_index (f->ooo_segments, s->next);
-	  diff = ooo_segment_distance_to_tail (f, s->start, *tail);
-	  ooo_segment_del (f, index);
-	}
-      /* End of search */
-      else
-	{
-	  ooo_segment_del (f, index);
-	  break;
-	}
-    }
+  if (!f->ooo_enq || !f_chunk_includes_pos (f->ooo_enq, enq_pos))
+    f_update_ooo_enq (f, enq_pos, enq_pos + len);
 
-  ASSERT (bytes <= f->nitems);
-  return bytes;
+  svm_fifo_copy_to_chunk (f, f->ooo_enq, enq_pos, src, len, &f->ooo_enq);
+
+  return 0;
 }
 
+/**
+ * Advance tail
+ */
 void
-svm_fifo_overwrite_head (svm_fifo_t * f, u8 * data, u32 len)
+svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 len)
 {
-  u32 n_chunk;
-  u32 head, tail, head_idx;
-  svm_fifo_chunk_t *c;
+  u32 tail;
 
-  ASSERT (len <= f->nitems);
+  ASSERT (len <= svm_fifo_max_enqueue_prod (f));
+  /* load-relaxed: producer owned index */
+  tail = f->tail;
+  tail = tail + len;
 
-  f_load_head_tail_cons (f, &head, &tail);
-  c = f->head_chunk;
-  head_idx = head % f->size;
-  head_idx -= c->start_byte;
-  n_chunk = c->length - head_idx;
-  if (len <= n_chunk)
-    clib_memcpy_fast (&c->data[head_idx], data, len);
+  if (rb_tree_is_init (&f->ooo_enq_lookup))
+    {
+      f->tail_chunk = f_lookup_clear_enq_chunks (f, f->tail_chunk, tail);
+      f->ooo_enq = 0;
+    }
   else
     {
-      clib_memcpy_fast (&c->data[head_idx], data, n_chunk);
-      clib_memcpy_fast (&c->next->data[0], data + n_chunk, len - n_chunk);
+      f->tail_chunk = svm_fifo_find_next_chunk (f, f->tail_chunk, tail);
     }
-}
-
-int
-svm_fifo_enqueue_nowait (svm_fifo_t * f, u32 len, const u8 * src)
-{
-  u32 tail, head, free_count;
-
-  f_load_head_tail_prod (f, &head, &tail);
-
-  /* free space in fifo can only increase during enqueue: SPSC */
-  free_count = f_free_count (f, head, tail);
-
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
-
-  if (PREDICT_FALSE (free_count == 0))
-    return SVM_FIFO_FULL;
-
-  /* number of bytes we're going to copy */
-  len = clib_min (free_count, len);
-
-  svm_fifo_copy_to_chunk (f, f->tail_chunk, tail % f->size, src, len,
-			  &f->tail_chunk);
-  tail += len;
-
-  svm_fifo_trace_add (f, head, n_total, 2);
-
-  /* collect out-of-order segments */
-  if (PREDICT_FALSE (f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX))
-    len += ooo_segment_try_collect (f, len, &tail);
 
   /* store-rel: producer owned index (paired with load-acq in consumer) */
   clib_atomic_store_rel_n (&f->tail, tail);
-
-  return len;
 }
 
-/**
- * Enqueue a future segment.
- *
- * Two choices: either copies the entire segment, or copies nothing
- * Returns 0 of the entire segment was copied
- * Returns -1 if none of the segment was copied due to lack of space
- */
-int
-svm_fifo_enqueue_with_offset (svm_fifo_t * f, u32 offset, u32 len, u8 * src)
+always_inline svm_fifo_chunk_t *
+f_unlink_chunks (svm_fifo_t * f, u32 end_pos, u8 maybe_ooo)
 {
-  u32 tail, head, free_count, tail_idx;
-
-  f_load_head_tail_prod (f, &head, &tail);
-
-  /* free space in fifo can only increase during enqueue: SPSC */
-  free_count = f_free_count (f, head, tail);
+  svm_fifo_chunk_t *start, *prev = 0, *c;
+  rb_tree_t *rt;
+  rb_node_t *n;
 
-  /* will this request fit? */
-  if ((len + offset) > free_count)
-    return -1;
+  ASSERT (!f_chunk_includes_pos (f->start_chunk, end_pos));
 
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+  if (maybe_ooo)
+    rt = &f->ooo_deq_lookup;
 
-  svm_fifo_trace_add (f, offset, len, 1);
+  c = f->start_chunk;
 
-  ooo_segment_add (f, offset, head, tail, len);
+  do
+    {
+      if (maybe_ooo && c->deq_rb_index != RBTREE_TNIL_INDEX)
+	{
+	  n = rb_node (rt, c->deq_rb_index);
+	  ASSERT (n == f_find_node_rbtree (rt, c->start_byte));
+	  rb_tree_del_node (rt, n);
+	  c->deq_rb_index = RBTREE_TNIL_INDEX;
+	}
+      if (!c->next)
+	break;
+      prev = c;
+      c = c->next;
+    }
+  while (!f_chunk_includes_pos (c, end_pos));
 
-  tail_idx = (tail + offset) % f->size;
+  if (maybe_ooo)
+    {
+      if (f->ooo_deq && f_pos_lt (f->ooo_deq->start_byte, f_chunk_end (c)))
+	f->ooo_deq = 0;
+    }
+  else
+    {
+      if (PREDICT_FALSE (f->ooo_deq != 0))
+	f->ooo_deq = 0;
+    }
 
-  if (!svm_fifo_chunk_includes_pos (f->ooo_enq, tail_idx))
-    f->ooo_enq = svm_fifo_find_chunk (f, tail_idx);
+  /* Avoid unlinking the last chunk */
+  if (!prev)
+    return 0;
 
-  svm_fifo_copy_to_chunk (f, f->ooo_enq, tail_idx, src, len, &f->ooo_enq);
+  prev->next = 0;
+  start = f->start_chunk;
+  f->start_chunk = c;
 
-  return 0;
+  return start;
 }
 
 int
-svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 len, u8 * dst)
+svm_fifo_dequeue (svm_fifo_t * f, u32 len, u8 * dst)
 {
   u32 tail, head, cursize;
 
@@ -840,16 +1015,19 @@ svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 len, u8 * dst)
   cursize = f_cursize (f, head, tail);
 
   if (PREDICT_FALSE (cursize == 0))
-    return -2;			/* nothing in the fifo */
+    return SVM_FIFO_EEMPTY;
 
   len = clib_min (cursize, len);
 
-  svm_fifo_copy_from_chunk (f, f->head_chunk, head % f->size, dst, len,
-			    &f->head_chunk);
-  head += len;
+  if (!f->head_chunk)
+    f->head_chunk = svm_fifo_find_chunk (f, head);
+
+  svm_fifo_copy_from_chunk (f, f->head_chunk, head, dst, len, &f->head_chunk);
+  head = head + len;
 
-  if (PREDICT_FALSE (f->flags & SVM_FIFO_F_SIZE_UPDATE))
-    svm_fifo_try_size_update (f, head);
+  if (f_pos_geq (head, f_chunk_end (f->start_chunk)))
+    fsh_collect_chunks (f->fs_hdr, f->slice_index,
+			f_unlink_chunks (f, head, 0));
 
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, head);
@@ -868,55 +1046,92 @@ svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 len, u8 * dst)
   cursize = f_cursize (f, head, tail);
 
   if (PREDICT_FALSE (cursize < offset))
-    return -2;			/* nothing in the fifo */
+    return SVM_FIFO_EEMPTY;
 
   len = clib_min (cursize - offset, len);
-  head_idx = (head + offset) % f->size;
-  if (!svm_fifo_chunk_includes_pos (f->ooo_deq, head_idx))
-    f->ooo_deq = svm_fifo_find_chunk (f, head_idx);
+  head_idx = head + offset;
+
+  if (!f->ooo_deq || !f_chunk_includes_pos (f->ooo_deq, head_idx))
+    f_update_ooo_deq (f, head_idx, head_idx + len);
 
   svm_fifo_copy_from_chunk (f, f->ooo_deq, head_idx, dst, len, &f->ooo_deq);
   return len;
 }
 
 int
-svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes)
+svm_fifo_dequeue_drop (svm_fifo_t * f, u32 len)
 {
-  u32 total_drop_bytes;
-  u32 tail, head, cursize;
+  u32 total_drop_bytes, tail, head, cursize;
 
   f_load_head_tail_cons (f, &head, &tail);
 
-  /* number of bytes we're going to drop */
+  /* number of bytes available */
   cursize = f_cursize (f, head, tail);
-
   if (PREDICT_FALSE (cursize == 0))
-    return -2;			/* nothing in the fifo */
-
-  svm_fifo_trace_add (f, tail, total_drop_bytes, 3);
+    return SVM_FIFO_EEMPTY;
 
   /* number of bytes we're going to drop */
-  total_drop_bytes = (cursize < max_bytes) ? cursize : max_bytes;
+  total_drop_bytes = clib_min (cursize, len);
+
+  svm_fifo_trace_add (f, tail, total_drop_bytes, 3);
 
   /* move head */
-  head += total_drop_bytes;
+  head = head + total_drop_bytes;
+
+  if (f_pos_geq (head, f_chunk_end (f->start_chunk)))
+    {
+      fsh_collect_chunks (f->fs_hdr, f->slice_index,
+			  f_unlink_chunks (f, head, 1));
+      f->head_chunk =
+	f_chunk_includes_pos (f->start_chunk, head) ? f->start_chunk : 0;
+    }
 
-  ASSERT (cursize >= total_drop_bytes);
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, head);
 
   return total_drop_bytes;
 }
 
+/**
+ * Drop all data from fifo
+ *
+ */
 void
 svm_fifo_dequeue_drop_all (svm_fifo_t * f)
 {
-  /* consumer foreign index */
-  u32 tail = clib_atomic_load_acq_n (&f->tail);
+  u32 head, tail;
+
+  f_load_head_tail_all_acq (f, &head, &tail);
+
+  if (!f->head_chunk || !f_chunk_includes_pos (f->head_chunk, head))
+    f->head_chunk = svm_fifo_find_chunk (f, head);
+
+  f->head_chunk = f_lookup_clear_deq_chunks (f, f->head_chunk, tail);
+
+  if (f_pos_geq (tail, f_chunk_end (f->start_chunk)))
+    fsh_collect_chunks (f->fs_hdr, f->slice_index,
+			f_unlink_chunks (f, tail, 0));
+
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, tail);
 }
 
+int
+svm_fifo_fill_chunk_list (svm_fifo_t * f)
+{
+  u32 head, tail;
+
+  f_load_head_tail_prod (f, &head, &tail);
+
+  if (f_chunk_end (f->end_chunk) - head >= f->size)
+    return 0;
+
+  if (f_try_chunk_alloc (f, head, tail, f->size - (tail - head)))
+    return SVM_FIFO_EGROW;
+
+  return 0;
+}
+
 int
 svm_fifo_segments (svm_fifo_t * f, svm_fifo_seg_t * fs)
 {
@@ -928,9 +1143,9 @@ svm_fifo_segments (svm_fifo_t * f, svm_fifo_seg_t * fs)
   cursize = f_cursize (f, head, tail);
 
   if (PREDICT_FALSE (cursize == 0))
-    return -2;			/* nothing in the fifo */
+    return SVM_FIFO_EEMPTY;
 
-  head_idx = head % f->size;
+  head_idx = head;
 
   if (tail < head)
     {
@@ -952,23 +1167,32 @@ svm_fifo_segments (svm_fifo_t * f, svm_fifo_seg_t * fs)
 void
 svm_fifo_segments_free (svm_fifo_t * f, svm_fifo_seg_t * fs)
 {
-  u32 head, head_idx;
+  u32 head;
 
   /* consumer owned index */
   head = f->head;
-  head_idx = head % f->size;
 
-  ASSERT (fs[0].data == f->head_chunk->data + head_idx);
-  head += fs[0].len + fs[1].len;
+  ASSERT (fs[0].data == f->head_chunk->data + head);
+  head = (head + fs[0].len + fs[1].len);
   /* store-rel: consumer owned index (paired with load-acq in producer) */
   clib_atomic_store_rel_n (&f->head, head);
 }
 
-/* Assumption: no prod and cons are accessing either dest or src fifo */
+/**
+ * Clones fifo
+ *
+ * Assumptions:
+ * - no prod and cons are accessing either dest or src fifo
+ * - fifo is not multi chunk
+ */
 void
 svm_fifo_clone (svm_fifo_t * df, svm_fifo_t * sf)
 {
   u32 head, tail;
+
+  /* Support only single chunk clones for now */
+  ASSERT (svm_fifo_n_chunks (sf) == 1);
+
   clib_memcpy_fast (df->head_chunk->data, sf->head_chunk->data, sf->size);
 
   f_load_head_tail_all_acq (sf, &head, &tail);
@@ -977,7 +1201,7 @@ svm_fifo_clone (svm_fifo_t * df, svm_fifo_t * sf)
 }
 
 u32
-svm_fifo_number_ooo_segments (svm_fifo_t * f)
+svm_fifo_n_ooo_segments (svm_fifo_t * f)
 {
   return pool_elts (f->ooo_segments);
 }
@@ -994,18 +1218,17 @@ svm_fifo_first_ooo_segment (svm_fifo_t * f)
 void
 svm_fifo_init_pointers (svm_fifo_t * f, u32 head, u32 tail)
 {
+  svm_fifo_chunk_t *c;
+
   clib_atomic_store_rel_n (&f->head, head);
   clib_atomic_store_rel_n (&f->tail, tail);
-  if (f->flags & SVM_FIFO_F_MULTI_CHUNK)
-    {
-      svm_fifo_chunk_t *c;
-      c = svm_fifo_find_chunk (f, head % f->size);
-      ASSERT (c != 0);
-      f->head_chunk = f->ooo_deq = c;
-      c = svm_fifo_find_chunk (f, tail % f->size);
-      ASSERT (c != 0);
-      f->tail_chunk = f->ooo_enq = c;
-    }
+
+  c = svm_fifo_find_chunk (f, head);
+  ASSERT (c != 0);
+  f->head_chunk = f->ooo_deq = c;
+  c = svm_fifo_find_chunk (f, tail);
+  ASSERT (c != 0);
+  f->tail_chunk = f->ooo_enq = c;
 }
 
 void
@@ -1031,6 +1254,260 @@ svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber)
     }
 }
 
+u8
+svm_fifo_is_sane (svm_fifo_t * f)
+{
+  svm_fifo_chunk_t *tmp;
+
+  if (f->head_chunk && !f_chunk_includes_pos (f->head_chunk, f->head))
+    return 0;
+  if (f->tail_chunk && !f_chunk_includes_pos (f->tail_chunk, f->tail))
+    return 0;
+  if (f->ooo_deq)
+    {
+      if (rb_tree_is_init (&f->ooo_deq_lookup))
+	{
+	  if (f_pos_lt (f->ooo_deq->start_byte, f->start_chunk->start_byte)
+	      || f_pos_gt (f->ooo_deq->start_byte,
+			   f_chunk_end (f->end_chunk)))
+	    return 0;
+
+	  tmp = f_find_chunk_rbtree (&f->ooo_deq_lookup,
+				     f->ooo_deq->start_byte);
+	}
+      else
+	tmp = svm_fifo_find_chunk (f, f->ooo_deq->start_byte);
+      if (tmp != f->ooo_deq)
+	return 0;
+    }
+  if (f->ooo_enq)
+    {
+      if (rb_tree_is_init (&f->ooo_enq_lookup))
+	{
+	  if (f_pos_lt (f->ooo_enq->start_byte, f->start_chunk->start_byte)
+	      || f_pos_gt (f->ooo_enq->start_byte,
+			   f_chunk_end (f->end_chunk)))
+	    return 0;
+
+	  tmp = f_find_chunk_rbtree (&f->ooo_enq_lookup,
+				     f->ooo_enq->start_byte);
+	}
+      else
+	{
+	  tmp = svm_fifo_find_next_chunk (f, f->tail_chunk,
+					  f->ooo_enq->start_byte);
+	}
+      if (tmp != f->ooo_enq)
+	return 0;
+    }
+
+  if (f->start_chunk->next)
+    {
+      svm_fifo_chunk_t *c, *prev = 0, *tmp;
+      u32 chunks_bytes = 0;
+
+      c = f->start_chunk;
+      do
+	{
+	  tmp = svm_fifo_find_chunk (f, c->start_byte);
+	  if (tmp != c)
+	    return 0;
+	  if (prev && (prev->start_byte + prev->length != c->start_byte))
+	    return 0;
+
+	  if (c->enq_rb_index != RBTREE_TNIL_INDEX)
+	    {
+	      tmp = f_find_chunk_rbtree (&f->ooo_enq_lookup, c->start_byte);
+	      if (tmp)
+		{
+		  if (tmp != c)
+		    return 0;
+		}
+	    }
+	  if (c->deq_rb_index != RBTREE_TNIL_INDEX)
+	    {
+	      tmp = f_find_chunk_rbtree (&f->ooo_deq_lookup, c->start_byte);
+	      if (tmp)
+		{
+		  if (tmp != c)
+		    return 0;
+		}
+	    }
+
+	  chunks_bytes += c->length;
+	  prev = c;
+	  c = c->next;
+	}
+      while (c);
+
+      if (chunks_bytes < f->tail - f->head)
+	return 0;
+    }
+
+  return 1;
+}
+
+u32
+svm_fifo_n_chunks (svm_fifo_t * f)
+{
+  svm_fifo_chunk_t *c;
+  int n_chunks = 0;
+
+  c = f->start_chunk;
+  while (c)
+    {
+      n_chunks++;
+      c = c->next;
+    }
+
+  return n_chunks;
+}
+
+u8 *
+format_ooo_segment (u8 * s, va_list * args)
+{
+  svm_fifo_t __clib_unused *f = va_arg (*args, svm_fifo_t *);
+  ooo_segment_t *seg = va_arg (*args, ooo_segment_t *);
+  s = format (s, "[%u, %u], len %u, next %d, prev %d", seg->start,
+	      seg->start + seg->length, seg->length, seg->next, seg->prev);
+  return s;
+}
+
+u8 *
+svm_fifo_dump_trace (u8 * s, svm_fifo_t * f)
+{
+#if SVM_FIFO_TRACE
+  svm_fifo_trace_elem_t *seg = 0;
+  int i = 0;
+
+  if (f->trace)
+    {
+      vec_foreach (seg, f->trace)
+      {
+	s = format (s, "{%u, %u, %u}, ", seg->offset, seg->len, seg->action);
+	i++;
+	if (i % 5 == 0)
+	  s = format (s, "\n");
+      }
+      s = format (s, "\n");
+    }
+  return s;
+#else
+  return 0;
+#endif
+}
+
+u8 *
+svm_fifo_replay (u8 * s, svm_fifo_t * f, u8 no_read, u8 verbose)
+{
+  int i, trace_len;
+  u8 *data = 0;
+  svm_fifo_trace_elem_t *trace;
+  u32 offset;
+  svm_fifo_t *dummy_fifo;
+
+  if (!f)
+    return s;
+
+#if SVM_FIFO_TRACE
+  trace = f->trace;
+  trace_len = vec_len (trace);
+#else
+  trace = 0;
+  trace_len = 0;
+#endif
+
+  dummy_fifo = svm_fifo_alloc (f->size);
+  svm_fifo_init (f, f->size);
+  clib_memset (f->head_chunk->data, 0xFF, f->size);
+  vec_validate (data, f->size);
+  for (i = 0; i < vec_len (data); i++)
+    data[i] = i;
+
+  for (i = 0; i < trace_len; i++)
+    {
+      offset = trace[i].offset;
+      if (trace[i].action == 1)
+	{
+	  if (verbose)
+	    s = format (s, "adding [%u, %u]:", trace[i].offset,
+			(trace[i].offset + trace[i].len));
+	  svm_fifo_enqueue_with_offset (dummy_fifo, trace[i].offset,
+					trace[i].len, &data[offset]);
+	}
+      else if (trace[i].action == 2)
+	{
+	  if (verbose)
+	    s = format (s, "adding [%u, %u]:", 0, trace[i].len);
+	  svm_fifo_enqueue (dummy_fifo, trace[i].len, &data[offset]);
+	}
+      else if (!no_read)
+	{
+	  if (verbose)
+	    s = format (s, "read: %u", trace[i].len);
+	  svm_fifo_dequeue_drop (dummy_fifo, trace[i].len);
+	}
+      if (verbose)
+	s = format (s, "%U", format_svm_fifo, dummy_fifo, 1);
+    }
+
+  s = format (s, "result: %U", format_svm_fifo, dummy_fifo, 1);
+
+  return s;
+}
+
+u8 *
+format_ooo_list (u8 * s, va_list * args)
+{
+  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
+  u32 indent = va_arg (*args, u32);
+  u32 ooo_segment_index = f->ooos_list_head;
+  ooo_segment_t *seg;
+
+  while (ooo_segment_index != OOO_SEGMENT_INVALID_INDEX)
+    {
+      seg = pool_elt_at_index (f->ooo_segments, ooo_segment_index);
+      s = format (s, "%U%U\n", format_white_space, indent, format_ooo_segment,
+		  f, seg);
+      ooo_segment_index = seg->next;
+    }
+
+  return s;
+}
+
+u8 *
+format_svm_fifo (u8 * s, va_list * args)
+{
+  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
+  int verbose = va_arg (*args, int);
+  u32 indent;
+
+  if (!s)
+    return s;
+
+  indent = format_get_indent (s);
+  s = format (s, "cursize %u nitems %u has_event %d min_alloc %u\n",
+	      svm_fifo_max_dequeue (f), f->size, f->has_event, f->min_alloc);
+  s = format (s, "%Uhead %u tail %u segment manager %u\n", format_white_space,
+	      indent, f->head, f->tail, f->segment_manager);
+
+  if (verbose > 1)
+    s = format (s, "%Uvpp session %d thread %d app session %d thread %d\n",
+		format_white_space, indent, f->master_session_index,
+		f->master_thread_index, f->client_session_index,
+		f->client_thread_index);
+
+  if (verbose)
+    {
+      s = format (s, "%Uooo pool %d active elts newest %u\n",
+		  format_white_space, indent, pool_elts (f->ooo_segments),
+		  f->ooos_newest);
+      if (svm_fifo_has_ooo_data (f))
+	s = format (s, " %U", format_ooo_list, f, indent, verbose);
+    }
+  return s;
+}
+
 #endif
 /*
  * fd.io coding-style-patch-verification: ON