X-Git-Url: https://gerrit.fd.io/r/gitweb?a=blobdiff_plain;f=src%2Fsvm%2Fsvm_fifo.c;h=f1ac8d49b9201198b493ff492fbb7baef1b500b5;hb=c95cfa218;hp=fc2189c51764a306c02f9665990e5860d2e38912;hpb=3eb5062b40feb3002de09a3caff86232d6e1adea;p=vpp.git

diff --git a/src/svm/svm_fifo.c b/src/svm/svm_fifo.c
index fc2189c5176..f1ac8d49b92 100644
--- a/src/svm/svm_fifo.c
+++ b/src/svm/svm_fifo.c
@@ -1,5 +1,9 @@
 /*
- * Copyright (c) 2016 Cisco and/or its affiliates.
+ * Copyright (c) 2016-2019 Cisco and/or its affiliates.
+ * Copyright (c) 2019 Arm Limited
+ * Copyright (c) 2010-2017 Intel Corporation and/or its affiliates.
+ * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
+ * Inspired from DPDK rte_ring.h (SPSC only) (derived from freebsd bufring.h).
  * 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:
@@ -14,205 +18,121 @@
  */
 
 #include <svm/svm_fifo.h>
+#include <svm/fifo_segment.h>
 #include <vppinfra/cpu.h>
 
-static inline u8
-position_lt (svm_fifo_t * f, u32 a, u32 b)
+CLIB_MARCH_FN (svm_fifo_copy_to_chunk, void, svm_fifo_t * f,
+	       svm_fifo_chunk_t * c, u32 tail_idx, const u8 * src, u32 len,
+	       svm_fifo_chunk_t ** last)
 {
-  return (ooo_segment_distance_from_tail (f, a)
-	  < ooo_segment_distance_from_tail (f, b));
-}
-
-static inline u8
-position_leq (svm_fifo_t * f, u32 a, u32 b)
-{
-  return (ooo_segment_distance_from_tail (f, a)
-	  <= ooo_segment_distance_from_tail (f, b));
-}
-
-static inline u8
-position_gt (svm_fifo_t * f, u32 a, u32 b)
-{
-  return (ooo_segment_distance_from_tail (f, a)
-	  > ooo_segment_distance_from_tail (f, b));
-}
-
-static inline u32
-position_diff (svm_fifo_t * f, u32 posa, u32 posb)
-{
-  return ooo_segment_distance_from_tail (f, posa)
-    - ooo_segment_distance_from_tail (f, posb);
-}
-
-static inline u32
-ooo_segment_end_pos (svm_fifo_t * f, ooo_segment_t * s)
-{
-  return (s->start + s->length) % f->nitems;
-}
-
-u8 *
-format_ooo_segment (u8 * s, va_list * args)
-{
-  ooo_segment_t *seg = va_arg (*args, ooo_segment_t *);
+  u32 n_chunk;
 
-  s = format (s, "pos %u, len %u, next %d, prev %d",
-	      seg->start, 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;
+  ASSERT (f_pos_geq (tail_idx, c->start_byte)
+	  && f_pos_lt (tail_idx, c->start_byte + c->length));
 
-  if (f->trace)
+  tail_idx -= c->start_byte;
+  n_chunk = c->length - tail_idx;
+  if (n_chunk <= len)
     {
-      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");
+      u32 to_copy = len;
+      clib_memcpy_fast (&c->data[tail_idx], src, n_chunk);
+      c = c->next;
+      while ((to_copy -= n_chunk))
+	{
+	  n_chunk = clib_min (c->length, to_copy);
+	  clib_memcpy_fast (&c->data[0], src + (len - to_copy), n_chunk);
+	  c = c->length <= to_copy ? c->next : c;
+	}
+      if (*last)
+	*last = c;
+    }
+  else
+    {
+      clib_memcpy_fast (&c->data[tail_idx], src, len);
     }
-  return s;
-#else
-  return 0;
-#endif
 }
 
-u8 *
-svm_fifo_replay (u8 * s, svm_fifo_t * f, u8 no_read, u8 verbose)
+CLIB_MARCH_FN (svm_fifo_copy_from_chunk, void, svm_fifo_t * f,
+	       svm_fifo_chunk_t * c, u32 head_idx, u8 * dst, u32 len,
+	       svm_fifo_chunk_t ** last)
 {
-  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
+  u32 n_chunk;
 
-  dummy_fifo = svm_fifo_create (f->nitems);
-  memset (f->data, 0xFF, f->nitems);
+  ASSERT (f_pos_geq (head_idx, c->start_byte)
+	  && f_pos_lt (head_idx, c->start_byte + c->length));
 
-  vec_validate (data, f->nitems);
-  for (i = 0; i < vec_len (data); i++)
-    data[i] = i;
-
-  for (i = 0; i < trace_len; i++)
+  head_idx -= c->start_byte;
+  n_chunk = c->length - head_idx;
+  if (n_chunk <= len)
     {
-      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->nitems);
-	  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_nowait (dummy_fifo, trace[i].len, &data[offset]);
-	}
-      else if (!no_read)
+      u32 to_copy = len;
+      clib_memcpy_fast (dst, &c->data[head_idx], n_chunk);
+      c = c->next;
+      while ((to_copy -= n_chunk))
 	{
-	  if (verbose)
-	    s = format (s, "read: %u", trace[i].len);
-	  svm_fifo_dequeue_drop (dummy_fifo, trace[i].len);
+	  CLIB_MEM_UNPOISON (c, sizeof (*c));
+	  CLIB_MEM_UNPOISON (c->data, c->length);
+	  n_chunk = clib_min (c->length, to_copy);
+	  clib_memcpy_fast (dst + (len - to_copy), &c->data[0], n_chunk);
+	  c = c->length <= to_copy ? c->next : c;
 	}
-      if (verbose)
-	s = format (s, "%U", format_svm_fifo, dummy_fifo, 1);
+      if (*last)
+	*last = c;
     }
+  else
+    {
+      clib_memcpy_fast (dst, &c->data[head_idx], len);
+    }
+}
 
-  s = format (s, "result: %U", format_svm_fifo, dummy_fifo, 1);
+#ifndef CLIB_MARCH_VARIANT
 
-  return s;
+static inline void
+svm_fifo_copy_to_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c, u32 tail_idx,
+			const u8 * src, u32 len, svm_fifo_chunk_t ** last)
+{
+  CLIB_MARCH_FN_SELECT (svm_fifo_copy_to_chunk) (f, c, tail_idx, src, len,
+						 last);
 }
 
-u8 *
-format_ooo_list (u8 * s, va_list * args)
+static inline void
+svm_fifo_copy_from_chunk (svm_fifo_t * f, svm_fifo_chunk_t * c, u32 head_idx,
+			  u8 * dst, u32 len, svm_fifo_chunk_t ** last)
 {
-  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
-  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\n", format_ooo_segment, seg);
-      ooo_segment_index = seg->next;
-    }
-
-  return s;
+  CLIB_MARCH_FN_SELECT (svm_fifo_copy_from_chunk) (f, c, head_idx, dst, len,
+						   last);
 }
 
-u8 *
-format_svm_fifo (u8 * s, va_list * args)
+static inline u32
+ooo_segment_end_pos (ooo_segment_t * s)
 {
-  svm_fifo_t *f = va_arg (*args, svm_fifo_t *);
-  int verbose = va_arg (*args, int);
-
-  s = format (s, "cursize %u nitems %u has_event %d\n",
-	      f->cursize, f->nitems, f->has_event);
-  s = format (s, " head %d tail %d\n", f->head, f->tail);
-
-  if (verbose > 1)
-    s = format
-      (s, " server session %d thread %d client session %d thread %d\n",
-       f->master_session_index, f->master_thread_index,
-       f->client_session_index, f->client_thread_index);
-
-  if (verbose)
-    {
-      s = format (s, " ooo pool %d active elts newest %u\n",
-		  pool_elts (f->ooo_segments), f->ooos_newest);
-      if (svm_fifo_has_ooo_data (f))
-	s = format (s, " %U", format_ooo_list, f, verbose);
-    }
-  return s;
+  return (s->start + s->length);
 }
 
-/** create an svm fifo, in the current heap. Fails vs blow up the process */
-svm_fifo_t *
-svm_fifo_create (u32 data_size_in_bytes)
+void
+svm_fifo_free_ooo_data (svm_fifo_t * f)
 {
-  svm_fifo_t *f;
+  pool_free (f->ooo_segments);
+}
 
-  f = clib_mem_alloc_aligned_or_null (sizeof (*f) + data_size_in_bytes,
-				      CLIB_CACHE_LINE_BYTES);
-  if (f == 0)
+static inline ooo_segment_t *
+ooo_segment_prev (svm_fifo_t * f, ooo_segment_t * s)
+{
+  if (s->prev == OOO_SEGMENT_INVALID_INDEX)
     return 0;
-
-  memset (f, 0, sizeof (*f));
-  f->nitems = data_size_in_bytes;
-  f->ooos_list_head = OOO_SEGMENT_INVALID_INDEX;
-  return (f);
+  return pool_elt_at_index (f->ooo_segments, s->prev);
 }
 
-void
-svm_fifo_free (svm_fifo_t * f)
+static inline ooo_segment_t *
+ooo_segment_next (svm_fifo_t * f, ooo_segment_t * s)
 {
-  pool_free (f->ooo_segments);
-  clib_mem_free (f);
+  if (s->next == OOO_SEGMENT_INVALID_INDEX)
+    return 0;
+  return pool_elt_at_index (f->ooo_segments, s->next);
 }
 
-always_inline ooo_segment_t *
-ooo_segment_new (svm_fifo_t * f, u32 start, u32 length)
+static inline ooo_segment_t *
+ooo_segment_alloc (svm_fifo_t * f, u32 start, u32 length)
 {
   ooo_segment_t *s;
 
@@ -220,14 +140,13 @@ ooo_segment_new (svm_fifo_t * f, u32 start, u32 length)
 
   s->start = start;
   s->length = length;
-
   s->prev = s->next = OOO_SEGMENT_INVALID_INDEX;
 
   return s;
 }
 
-always_inline void
-ooo_segment_del (svm_fifo_t * f, u32 index)
+static inline void
+ooo_segment_free (svm_fifo_t * f, u32 index)
 {
   ooo_segment_t *cur, *prev = 0, *next = 0;
   cur = pool_elt_at_index (f->ooo_segments, index);
@@ -256,21 +175,22 @@ ooo_segment_del (svm_fifo_t * f, u32 index)
  * adjacent segments and removing overlapping ones.
  */
 static void
-ooo_segment_add (svm_fifo_t * f, u32 offset, u32 length)
+ooo_segment_add (svm_fifo_t * f, u32 offset, u32 head, u32 tail, u32 length)
 {
   ooo_segment_t *s, *new_s, *prev, *next, *it;
   u32 new_index, s_end_pos, s_index;
-  u32 normalized_position, normalized_end_position;
+  u32 offset_pos, offset_end_pos;
 
-  ASSERT (offset + length <= ooo_segment_distance_from_tail (f, f->head));
-  normalized_position = (f->tail + offset) % f->nitems;
-  normalized_end_position = (f->tail + offset + length) % f->nitems;
+  ASSERT (offset + length <= f_free_count (f, head, tail));
+
+  offset_pos = tail + offset;
+  offset_end_pos = tail + offset + length;
 
   f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
 
   if (f->ooos_list_head == OOO_SEGMENT_INVALID_INDEX)
     {
-      s = ooo_segment_new (f, normalized_position, length);
+      s = ooo_segment_alloc (f, offset_pos, length);
       f->ooos_list_head = s - f->ooo_segments;
       f->ooos_newest = f->ooos_list_head;
       return;
@@ -279,30 +199,29 @@ ooo_segment_add (svm_fifo_t * f, u32 offset, u32 length)
   /* 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, normalized_position))
+	 && 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_get_prev (f, s);
-  if (prev
-      && position_leq (f, normalized_position, ooo_segment_end_pos (f, prev)))
+  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 (f, s);
+      s_end_pos = ooo_segment_end_pos (s);
 
-      /* Since we have previous, normalized start position cannot be smaller
+      /* Since we have previous, offset start position cannot be smaller
        * than prev->start. Check tail */
-      ASSERT (position_lt (f, s->start, normalized_position));
+      ASSERT (f_pos_lt (s->start, offset_pos));
       goto check_tail;
     }
 
   s_index = s - f->ooo_segments;
-  s_end_pos = ooo_segment_end_pos (f, s);
+  s_end_pos = ooo_segment_end_pos (s);
 
   /* No overlap, add before current segment */
-  if (position_lt (f, normalized_end_position, s->start))
+  if (f_pos_lt (offset_end_pos, s->start))
     {
-      new_s = ooo_segment_new (f, normalized_position, length);
+      new_s = ooo_segment_alloc (f, offset_pos, length);
       new_index = new_s - f->ooo_segments;
 
       /* Pool might've moved, get segment again */
@@ -325,9 +244,9 @@ ooo_segment_add (svm_fifo_t * f, u32 offset, u32 length)
       return;
     }
   /* No overlap, add after current segment */
-  else if (position_gt (f, normalized_position, s_end_pos))
+  else if (f_pos_gt (offset_pos, s_end_pos))
     {
-      new_s = ooo_segment_new (f, normalized_position, length);
+      new_s = ooo_segment_alloc (f, offset_pos, length);
       new_index = new_s - f->ooo_segments;
 
       /* Pool might've moved, get segment again */
@@ -348,36 +267,34 @@ ooo_segment_add (svm_fifo_t * f, u32 offset, u32 length)
    */
 
   /* Merge at head */
-  if (position_lt (f, normalized_position, s->start))
+  if (f_pos_lt (offset_pos, s->start))
     {
-      s->start = normalized_position;
-      s->length = position_diff (f, s_end_pos, s->start);
+      s->start = offset_pos;
+      s->length = s_end_pos - s->start;
       f->ooos_newest = s - f->ooo_segments;
     }
 
 check_tail:
 
   /* Overlapping tail */
-  if (position_gt (f, normalized_end_position, s_end_pos))
+  if (f_pos_gt (offset_end_pos, s_end_pos))
     {
-      s->length = position_diff (f, normalized_end_position, s->start);
+      s->length = offset_end_pos - s->start;
 
       /* 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),
-				 normalized_end_position))
+      while (it && f_pos_leq (ooo_segment_end_pos (it), offset_end_pos))
 	{
 	  next = ooo_segment_next (f, it);
-	  ooo_segment_del (f, it - f->ooo_segments);
+	  ooo_segment_free (f, it - f->ooo_segments);
 	  it = next;
 	}
 
       /* If partial overlap with last, merge */
-      if (it && position_leq (f, it->start, normalized_end_position))
+      if (it && f_pos_leq (it->start, offset_end_pos))
 	{
-	  s->length = position_diff (f, ooo_segment_end_pos (f, it),
-				     s->start);
-	  ooo_segment_del (f, it - f->ooo_segments);
+	  s->length = ooo_segment_end_pos (it) - s->start;
+	  ooo_segment_free (f, it - f->ooo_segments);
 	}
       f->ooos_newest = s - f->ooo_segments;
     }
@@ -388,14 +305,14 @@ check_tail:
  * advanced. Returns the number of bytes added to tail.
  */
 static int
-ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued)
+ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued, u32 * tail)
 {
+  u32 s_index, bytes = 0;
   ooo_segment_t *s;
-  u32 index, bytes = 0;
   i32 diff;
 
   s = pool_elt_at_index (f->ooo_segments, f->ooos_list_head);
-  diff = ooo_segment_distance_to_tail (f, s->start);
+  diff = *tail - s->start;
 
   ASSERT (diff != n_bytes_enqueued);
 
@@ -405,15 +322,14 @@ ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued)
   /* If last tail update overlaps one/multiple ooo segments, remove them */
   while (0 <= diff && diff < n_bytes_enqueued)
     {
-      index = s - f->ooo_segments;
+      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;
-	  f->tail += bytes;
-	  f->tail %= f->nitems;
-	  ooo_segment_del (f, index);
+	  *tail = *tail + bytes;
+	  ooo_segment_free (f, s_index);
 	  break;
 	}
 
@@ -421,386 +337,962 @@ ooo_segment_try_collect (svm_fifo_t * f, u32 n_bytes_enqueued)
       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);
-	  ooo_segment_del (f, index);
+	  diff = *tail - s->start;
+	  ooo_segment_free (f, s_index);
 	}
       /* End of search */
       else
 	{
-	  ooo_segment_del (f, index);
+	  ooo_segment_free (f, s_index);
 	  break;
 	}
     }
 
-  ASSERT (bytes >= 0 && bytes <= f->nitems);
+  ASSERT (bytes <= f->size);
   return bytes;
 }
 
-static int
-svm_fifo_enqueue_internal (svm_fifo_t * f, u32 max_bytes, u8 * copy_from_here)
+__clib_unused static ooo_segment_t *
+ooo_segment_last (svm_fifo_t * f)
 {
-  u32 total_copy_bytes, first_copy_bytes, second_copy_bytes;
-  u32 cursize, nitems;
+  ooo_segment_t *s;
 
-  /* read cursize, which can only increase while we're working */
-  cursize = svm_fifo_max_dequeue (f);
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+  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;
 
-  if (PREDICT_FALSE (cursize == f->nitems))
-    return -2;			/* fifo stuffed */
+  f->size = size;
+  f->ooos_list_head = OOO_SEGMENT_INVALID_INDEX;
+  f->segment_index = SVM_FIFO_INVALID_INDEX;
+  f->refcnt = 1;
+  f->head = f->tail = f->flags = 0;
+  f->head_chunk = f->tail_chunk = f->start_chunk;
+  f->ooo_deq = f->ooo_enq = 0;
 
-  nitems = f->nitems;
+  min_alloc = size > 32 << 10 ? size >> 3 : 4096;
+  min_alloc = clib_min (min_alloc, 64 << 10);
+  f->min_alloc = min_alloc;
 
-  /* Number of bytes we're going to copy */
-  total_copy_bytes = (nitems - cursize) < max_bytes ?
-    (nitems - cursize) : max_bytes;
+  /*
+   * Initialize chunks
+   */
+  f->start_chunk->start_byte = 0;
+  prev = f->start_chunk;
+  prev->enq_rb_index = prev->deq_rb_index = RBTREE_TNIL_INDEX;
+  c = prev->next;
 
-  if (PREDICT_TRUE (copy_from_here != 0))
+  while (c)
     {
-      /* Number of bytes in first copy segment */
-      first_copy_bytes = ((nitems - f->tail) < total_copy_bytes)
-	? (nitems - f->tail) : total_copy_bytes;
-
-      clib_memcpy (&f->data[f->tail], copy_from_here, first_copy_bytes);
-      f->tail += first_copy_bytes;
-      f->tail = (f->tail == nitems) ? 0 : f->tail;
+      c->start_byte = prev->start_byte + prev->length;
+      c->enq_rb_index = c->deq_rb_index = RBTREE_TNIL_INDEX;
+      prev = c;
+      c = c->next;
+    }
+}
 
-      /* Number of bytes in second copy segment, if any */
-      second_copy_bytes = total_copy_bytes - first_copy_bytes;
-      if (second_copy_bytes)
-	{
-	  clib_memcpy (&f->data[f->tail], copy_from_here + first_copy_bytes,
-		       second_copy_bytes);
-	  f->tail += second_copy_bytes;
-	  f->tail = (f->tail == nitems) ? 0 : f->tail;
-	}
+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 (0);
-
-      /* Account for a zero-copy enqueue done elsewhere */
-      ASSERT (max_bytes <= (nitems - cursize));
-      f->tail += max_bytes;
-      f->tail = f->tail % nitems;
-      total_copy_bytes = max_bytes;
+      ASSERT (!rb_tree_is_init (&f->ooo_deq_lookup));
+      rb_tree_init (&f->ooo_deq_lookup);
     }
+}
 
-  svm_fifo_trace_add (f, f->head, total_copy_bytes, 2);
+/**
+ * Creates a fifo in the current heap. Fails vs blow up the process
+ */
+svm_fifo_t *
+svm_fifo_alloc (u32 data_size_in_bytes)
+{
+  u32 rounded_data_size;
+  svm_fifo_chunk_t *c;
+  svm_fifo_t *f;
 
-  /* Any out-of-order segments to collect? */
-  if (PREDICT_FALSE (f->ooos_list_head != OOO_SEGMENT_INVALID_INDEX))
-    total_copy_bytes += ooo_segment_try_collect (f, total_copy_bytes);
+  f = clib_mem_alloc_aligned_or_null (sizeof (*f), CLIB_CACHE_LINE_BYTES);
+  if (f == 0)
+    return 0;
 
-  /* Atomically increase the queue length */
-  ASSERT (cursize + total_copy_bytes <= nitems);
-  __sync_fetch_and_add (&f->cursize, total_copy_bytes);
+  clib_memset (f, 0, sizeof (*f));
 
-  return (total_copy_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;
+    }
 
-#define SVM_ENQUEUE_CLONE_TEMPLATE(arch, fn, tgt)                       \
-  uword                                                                 \
-  __attribute__ ((flatten))                                             \
-  __attribute__ ((target (tgt)))                                        \
-  CLIB_CPU_OPTIMIZED                                                    \
-  fn ## _ ## arch ( svm_fifo_t * f, u32 max_bytes, u8 * copy_from_here) \
-  { return fn (f, max_bytes, copy_from_here);}
+  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;
 
-static int
-svm_fifo_enqueue_nowait_ma (svm_fifo_t * f, u32 max_bytes,
-			    u8 * copy_from_here)
-{
-  return svm_fifo_enqueue_internal (f, max_bytes, copy_from_here);
+  return f;
 }
 
-foreach_march_variant (SVM_ENQUEUE_CLONE_TEMPLATE,
-		       svm_fifo_enqueue_nowait_ma);
-CLIB_MULTIARCH_SELECT_FN (svm_fifo_enqueue_nowait_ma);
-
-int
-svm_fifo_enqueue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_from_here)
+/**
+ * Creates a fifo chunk in the current heap
+ */
+svm_fifo_chunk_t *
+svm_fifo_chunk_alloc (u32 size)
 {
-#if CLIB_DEBUG > 0
-  return svm_fifo_enqueue_nowait_ma (f, max_bytes, copy_from_here);
-#else
-  static int (*fp) (svm_fifo_t *, u32, u8 *);
+  svm_fifo_chunk_t *c;
+  u32 rounded_size;
 
-  if (PREDICT_FALSE (fp == 0))
-    fp = (void *) svm_fifo_enqueue_nowait_ma_multiarch_select ();
+  /* round chunk size to the next highest power-of-two */
+  rounded_size = (1 << (max_log2 (size)));
+  c = clib_mem_alloc_aligned_or_null (sizeof (*c) + rounded_size,
+				      CLIB_CACHE_LINE_BYTES);
+  if (c == 0)
+    return 0;
 
-  return (*fp) (f, max_bytes, copy_from_here);
-#endif
+  clib_memset (c, 0, sizeof (*c));
+  c->length = rounded_size;
+  return c;
 }
 
 /**
- * Enqueue a future segment.
+ * Find chunk for given byte position
  *
- * 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
+ * @param f	fifo
+ * @param pos	normalized position in fifo
+ *
+ * @return chunk that includes given position or 0
  */
-static int
-svm_fifo_enqueue_with_offset_internal (svm_fifo_t * f,
-				       u32 offset,
-				       u32 required_bytes,
-				       u8 * copy_from_here)
+static svm_fifo_chunk_t *
+svm_fifo_find_chunk (svm_fifo_t * f, u32 pos)
 {
-  u32 total_copy_bytes, first_copy_bytes, second_copy_bytes;
-  u32 cursize, nitems, normalized_offset;
-  u32 offset_from_tail;
-
-  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+  svm_fifo_chunk_t *c;
 
-  /* read cursize, which can only increase while we're working */
-  cursize = svm_fifo_max_dequeue (f);
-  nitems = f->nitems;
+  c = f->start_chunk;
+  while (c && !f_chunk_includes_pos (c, pos))
+    c = c->next;
 
-  ASSERT (required_bytes < nitems);
-
-  normalized_offset = (f->tail + offset) % nitems;
+  return c;
+}
 
-  /* Will this request fit? */
-  offset_from_tail = (nitems + normalized_offset - f->tail) % nitems;
-  if ((required_bytes + offset_from_tail) > (nitems - cursize))
-    return -1;
+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;
 
-  svm_fifo_trace_add (f, offset, required_bytes, 1);
+  ASSERT (start != 0);
 
-  ooo_segment_add (f, offset, required_bytes);
+  c = start;
+  while (c && !f_chunk_includes_pos (c, pos))
+    c = c->next;
 
-  /* Number of bytes we're going to copy */
-  total_copy_bytes = required_bytes;
+  return c;
+}
 
-  /* Number of bytes in first copy segment */
-  first_copy_bytes = ((nitems - normalized_offset) < total_copy_bytes)
-    ? (nitems - normalized_offset) : total_copy_bytes;
+u32
+svm_fifo_max_read_chunk (svm_fifo_t * f)
+{
+  u32 head, tail, end_chunk;
 
-  clib_memcpy (&f->data[normalized_offset], copy_from_here, first_copy_bytes);
+  f_load_head_tail_cons (f, &head, &tail);
+  ASSERT (!f->head_chunk || f_chunk_includes_pos (f->head_chunk, head));
 
-  /* Number of bytes in second copy segment, if any */
-  second_copy_bytes = total_copy_bytes - first_copy_bytes;
-  if (second_copy_bytes)
+  if (!f->head_chunk)
     {
-      normalized_offset += first_copy_bytes;
-      normalized_offset %= nitems;
-
-      ASSERT (normalized_offset == 0);
-
-      clib_memcpy (&f->data[normalized_offset],
-		   copy_from_here + first_copy_bytes, second_copy_bytes);
+      f->head_chunk = svm_fifo_find_chunk (f, head);
+      if (PREDICT_FALSE (!f->head_chunk))
+	return 0;
     }
 
-  return (0);
-}
-
+  end_chunk = f_chunk_end (f->head_chunk);
 
-int
-svm_fifo_enqueue_with_offset (svm_fifo_t * f,
-			      u32 offset,
-			      u32 required_bytes, u8 * copy_from_here)
-{
-  return svm_fifo_enqueue_with_offset_internal (f, offset, required_bytes,
-						copy_from_here);
+  return f_pos_lt (end_chunk, tail) ? end_chunk - head : tail - head;
 }
 
-
-static int
-svm_fifo_dequeue_internal (svm_fifo_t * f, u32 max_bytes, u8 * copy_here)
+u32
+svm_fifo_max_write_chunk (svm_fifo_t * f)
 {
-  u32 total_copy_bytes, first_copy_bytes, second_copy_bytes;
-  u32 cursize, nitems;
+  u32 head, tail;
 
-  /* read cursize, which can only increase while we're working */
-  cursize = svm_fifo_max_dequeue (f);
-  if (PREDICT_FALSE (cursize == 0))
-    return -2;			/* nothing in the fifo */
+  f_load_head_tail_prod (f, &head, &tail);
+  ASSERT (!f->tail_chunk || f_chunk_includes_pos (f->tail_chunk, tail));
 
-  nitems = f->nitems;
+  return f->tail_chunk ? f_chunk_end (f->tail_chunk) - tail : 0;
+}
 
-  /* Number of bytes we're going to copy */
-  total_copy_bytes = (cursize < max_bytes) ? cursize : max_bytes;
+static rb_node_t *
+f_find_node_rbtree (rb_tree_t * rt, u32 pos)
+{
+  rb_node_t *cur, *prev;
 
-  if (PREDICT_TRUE (copy_here != 0))
-    {
-      /* Number of bytes in first copy segment */
-      first_copy_bytes = ((nitems - f->head) < total_copy_bytes)
-	? (nitems - f->head) : total_copy_bytes;
-      clib_memcpy (copy_here, &f->data[f->head], first_copy_bytes);
-      f->head += first_copy_bytes;
-      f->head = (f->head == nitems) ? 0 : f->head;
+  cur = rb_node (rt, rt->root);
+  if (PREDICT_FALSE (rb_node_is_tnil (rt, cur)))
+    return 0;
 
-      /* Number of bytes in second copy segment, if any */
-      second_copy_bytes = total_copy_bytes - first_copy_bytes;
-      if (second_copy_bytes)
+  while (pos != cur->key)
+    {
+      prev = cur;
+      if (f_pos_lt (pos, cur->key))
 	{
-	  clib_memcpy (copy_here + first_copy_bytes,
-		       &f->data[f->head], second_copy_bytes);
-	  f->head += second_copy_bytes;
-	  f->head = (f->head == nitems) ? 0 : f->head;
+	  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;
+	    }
 	}
-    }
-  else
-    {
-      ASSERT (0);
-      /* Account for a zero-copy dequeue done elsewhere */
-      ASSERT (max_bytes <= cursize);
-      f->head += max_bytes;
-      f->head = f->head % nitems;
-      cursize -= max_bytes;
-      total_copy_bytes = max_bytes;
     }
 
-  ASSERT (f->head <= nitems);
-  ASSERT (cursize >= total_copy_bytes);
-  __sync_fetch_and_sub (&f->cursize, total_copy_bytes);
+  if (rb_node_is_tnil (rt, cur))
+    return 0;
 
-  return (total_copy_bytes);
+  return cur;
 }
 
-static int
-svm_fifo_dequeue_nowait_ma (svm_fifo_t * f, u32 max_bytes, u8 * copy_here)
+static svm_fifo_chunk_t *
+f_find_chunk_rbtree (rb_tree_t * rt, u32 pos)
 {
-  return svm_fifo_dequeue_internal (f, max_bytes, copy_here);
-}
-
-#define SVM_FIFO_DEQUEUE_CLONE_TEMPLATE(arch, fn, tgt)          \
-  uword                                                         \
-  __attribute__ ((flatten))                                     \
-  __attribute__ ((target (tgt)))                                \
-  CLIB_CPU_OPTIMIZED                                            \
-  fn ## _ ## arch ( svm_fifo_t * f, u32 max_bytes,              \
-                    u8 * copy_here)                             \
-  { return fn (f, max_bytes, copy_here);}
+  svm_fifo_chunk_t *c;
+  rb_node_t *n;
 
-foreach_march_variant (SVM_FIFO_DEQUEUE_CLONE_TEMPLATE,
-		       svm_fifo_dequeue_nowait_ma);
-CLIB_MULTIARCH_SELECT_FN (svm_fifo_dequeue_nowait_ma);
-
-int
-svm_fifo_dequeue_nowait (svm_fifo_t * f, u32 max_bytes, u8 * copy_here)
-{
-#if CLIB_DEBUG > 0
-  return svm_fifo_dequeue_nowait_ma (f, max_bytes, copy_here);
-#else
-  static int (*fp) (svm_fifo_t *, u32, u8 *);
+  if (!rb_tree_is_init (rt))
+    return 0;
 
-  if (PREDICT_FALSE (fp == 0))
-    fp = (void *) svm_fifo_dequeue_nowait_ma_multiarch_select ();
+  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 (*fp) (f, max_bytes, copy_here);
-#endif
+  return 0;
 }
 
-static int
-svm_fifo_peek_ma (svm_fifo_t * f, u32 relative_offset, u32 max_bytes,
-		  u8 * copy_here)
+static void
+f_update_ooo_enq (svm_fifo_t * f, u32 start_pos, u32 end_pos)
 {
-  u32 total_copy_bytes, first_copy_bytes, second_copy_bytes;
-  u32 cursize, nitems, real_head;
-
-  /* read cursize, which can only increase while we're working */
-  cursize = svm_fifo_max_dequeue (f);
-  if (PREDICT_FALSE (cursize < relative_offset))
-    return -2;			/* nothing in the fifo */
-
-  nitems = f->nitems;
-  real_head = f->head + relative_offset;
-  real_head = real_head >= nitems ? real_head - nitems : real_head;
+  rb_tree_t *rt = &f->ooo_enq_lookup;
+  svm_fifo_chunk_t *c;
+  rb_node_t *cur;
 
-  /* Number of bytes we're going to copy */
-  total_copy_bytes = (cursize - relative_offset < max_bytes) ?
-    cursize - relative_offset : max_bytes;
-
-  if (PREDICT_TRUE (copy_here != 0))
+  /* Use linear search if rbtree is not initialized */
+  if (PREDICT_FALSE (!rb_tree_is_init (rt)))
     {
-      /* Number of bytes in first copy segment */
-      first_copy_bytes =
-	((nitems - real_head) < total_copy_bytes) ?
-	(nitems - real_head) : total_copy_bytes;
-      clib_memcpy (copy_here, &f->data[real_head], first_copy_bytes);
+      f->ooo_enq = svm_fifo_find_next_chunk (f, f->tail_chunk, start_pos);
+      return;
+    }
 
-      /* Number of bytes in second copy segment, if any */
-      second_copy_bytes = total_copy_bytes - first_copy_bytes;
-      if (second_copy_bytes)
-	{
-	  clib_memcpy (copy_here + first_copy_bytes, &f->data[0],
-		       second_copy_bytes);
-	}
+  if (rt->root == RBTREE_TNIL_INDEX)
+    {
+      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
+    {
+      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));
     }
-  return total_copy_bytes;
-}
 
-#define SVM_FIFO_PEEK_CLONE_TEMPLATE(arch, fn, tgt)                     \
-  uword                                                                 \
-  __attribute__ ((flatten))                                             \
-  __attribute__ ((target (tgt)))                                        \
-  CLIB_CPU_OPTIMIZED                                                    \
-  fn ## _ ## arch ( svm_fifo_t * f, u32 relative_offset, u32 max_bytes, \
-                    u8 * copy_here)                                     \
-  { return fn (f, relative_offset, max_bytes, copy_here);}
+  if (f_chunk_includes_pos (c, start_pos))
+    f->ooo_enq = c;
 
-foreach_march_variant (SVM_FIFO_PEEK_CLONE_TEMPLATE, svm_fifo_peek_ma);
-CLIB_MULTIARCH_SELECT_FN (svm_fifo_peek_ma);
+  if (f_chunk_includes_pos (c, end_pos))
+    return;
 
-int
-svm_fifo_peek (svm_fifo_t * f, u32 relative_offset, u32 max_bytes,
-	       u8 * copy_here)
-{
-#if CLIB_DEBUG > 0
-  return svm_fifo_peek_ma (f, relative_offset, max_bytes, copy_here);
-#else
-  static int (*fp) (svm_fifo_t *, u32, u32, u8 *);
+  do
+    {
+      c = c->next;
+      if (!c || c->enq_rb_index != RBTREE_TNIL_INDEX)
+	break;
 
-  if (PREDICT_FALSE (fp == 0))
-    fp = (void *) svm_fifo_peek_ma_multiarch_select ();
+      c->enq_rb_index = rb_tree_add_custom (rt, c->start_byte,
+					    pointer_to_uword (c), f_pos_lt);
 
-  return (*fp) (f, relative_offset, max_bytes, copy_here);
-#endif
+      if (f_chunk_includes_pos (c, start_pos))
+	f->ooo_enq = c;
+    }
+  while (!f_chunk_includes_pos (c, end_pos));
 }
 
-int
-svm_fifo_dequeue_drop (svm_fifo_t * f, u32 max_bytes)
+static void
+f_update_ooo_deq (svm_fifo_t * f, u32 start_pos, u32 end_pos)
 {
-  u32 total_drop_bytes, first_drop_bytes, second_drop_bytes;
-  u32 cursize, nitems;
-
-  /* read cursize, which can only increase while we're working */
-  cursize = svm_fifo_max_dequeue (f);
-  if (PREDICT_FALSE (cursize == 0))
-    return -2;			/* nothing in the fifo */
-
-  nitems = f->nitems;
-
-  /* Number of bytes we're going to drop */
-  total_drop_bytes = (cursize < max_bytes) ? cursize : max_bytes;
-
-  svm_fifo_trace_add (f, f->tail, total_drop_bytes, 3);
-
-  /* Number of bytes in first copy segment */
-  first_drop_bytes =
-    ((nitems - f->head) < total_drop_bytes) ?
-    (nitems - f->head) : total_drop_bytes;
-  f->head += first_drop_bytes;
-  f->head = (f->head == nitems) ? 0 : f->head;
+  rb_tree_t *rt = &f->ooo_deq_lookup;
+  rb_node_t *cur;
+  svm_fifo_chunk_t *c;
 
-  /* Number of bytes in second drop segment, if any */
-  second_drop_bytes = total_drop_bytes - first_drop_bytes;
-  if (second_drop_bytes)
+  /* Use linear search if rbtree is not initialized  */
+  if (PREDICT_FALSE (!rb_tree_is_init (rt)))
     {
-      f->head += second_drop_bytes;
-      f->head = (f->head == nitems) ? 0 : f->head;
+      f->ooo_deq = svm_fifo_find_chunk (f, start_pos);
+      return;
+    }
+
+  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
+    {
+      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 svm_fifo_chunk_t *
+f_lookup_clear_enq_chunks (svm_fifo_t * f, svm_fifo_chunk_t * start,
+			   u32 end_pos)
+{
+  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;
+}
+
+static svm_fifo_chunk_t *
+f_lookup_clear_deq_chunks (svm_fifo_t * f, svm_fifo_chunk_t * start,
+			   u32 end_pos)
+{
+  rb_tree_t *rt = &f->ooo_deq_lookup;
+  svm_fifo_chunk_t *c;
+  rb_node_t *n;
+
+  c = start;
+  while (c && !f_chunk_includes_pos (c, end_pos))
+    {
+      if (c->deq_rb_index != RBTREE_TNIL_INDEX)
+	{
+	  n = rb_node (rt, c->deq_rb_index);
+	  rb_tree_del_node (rt, n);
+	  c->deq_rb_index = RBTREE_TNIL_INDEX;
+	}
+
+      c = c->next;
+    }
+
+  return c;
+}
+
+void
+svm_fifo_free_chunk_lookup (svm_fifo_t * f)
+{
+  rb_tree_free_nodes (&f->ooo_enq_lookup);
+  rb_tree_free_nodes (&f->ooo_deq_lookup);
+}
+
+void
+svm_fifo_free (svm_fifo_t * f)
+{
+  ASSERT (f->refcnt > 0);
+
+  if (--f->refcnt == 0)
+    {
+      /* ooo data is not allocated on segment heap */
+      svm_fifo_free_chunk_lookup (f);
+      clib_mem_free (f);
+    }
+}
+
+void
+svm_fifo_overwrite_head (svm_fifo_t * f, u8 * src, u32 len)
+{
+  u32 n_chunk;
+  u32 head, tail, head_idx;
+  svm_fifo_chunk_t *c;
+
+  ASSERT (len <= f->size);
+
+  f_load_head_tail_cons (f, &head, &tail);
+
+  if (!f->head_chunk)
+    f->head_chunk = svm_fifo_find_chunk (f, head);
+
+  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
+    {
+      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);
+    }
+}
+
+static int
+f_try_chunk_alloc (svm_fifo_t * f, u32 head, u32 tail, u32 len)
+{
+  svm_fifo_chunk_t *c, *cur, *prev;
+  u32 alloc_size, free_alloced;
+
+  free_alloced = f_chunk_end (f->end_chunk) - tail;
+
+  alloc_size = clib_min (f->min_alloc, f->size - (tail - head));
+  alloc_size = clib_max (alloc_size, len - free_alloced);
+
+  c = fsh_alloc_chunk (f->fs_hdr, f->slice_index, alloc_size);
+  if (PREDICT_FALSE (!c))
+    return -1;
+
+  cur = c;
+  prev = f->end_chunk;
+
+  while (cur)
+    {
+      cur->start_byte = prev->start_byte + prev->length;
+      cur->enq_rb_index = RBTREE_TNIL_INDEX;
+      cur->deq_rb_index = RBTREE_TNIL_INDEX;
+
+      prev = cur;
+      cur = cur->next;
+    }
+
+  prev->next = 0;
+  f->end_chunk->next = c;
+  f->end_chunk = prev;
+
+  if (!f->tail_chunk)
+    f->tail_chunk = c;
+
+  return 0;
+}
+
+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;
+
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+
+  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);
+
+  if (PREDICT_FALSE (free_count == 0))
+    return SVM_FIFO_EFULL;
+
+  /* number of bytes we're going to copy */
+  len = clib_min (free_count, len);
+
+  if (f_pos_gt (tail + len, f_chunk_end (f->end_chunk)))
+    {
+      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;
+	}
+    }
+
+  old_tail_c = f->tail_chunk;
+
+  svm_fifo_copy_to_chunk (f, f->tail_chunk, tail, src, len, &f->tail_chunk);
+  tail = tail + len;
+
+  svm_fifo_trace_add (f, head, len, 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);
+      /* 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;
+}
+
+/**
+ * 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)
+{
+  u32 tail, head, free_count, enq_pos;
+
+  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;
+
+  /* will this request fit? */
+  if ((len + offset) > free_count)
+    return SVM_FIFO_EFULL;
+
+  enq_pos = tail + offset;
+
+  if (f_pos_gt (enq_pos + len, f_chunk_end (f->end_chunk)))
+    {
+      if (PREDICT_FALSE (f_try_chunk_alloc (f, head, tail, offset + len)))
+	return SVM_FIFO_EGROW;
+    }
+
+  svm_fifo_trace_add (f, offset, len, 1);
+  ooo_segment_add (f, offset, head, tail, len);
+
+  if (!f->ooo_enq || !f_chunk_includes_pos (f->ooo_enq, enq_pos))
+    f_update_ooo_enq (f, enq_pos, enq_pos + len);
+
+  svm_fifo_copy_to_chunk (f, f->ooo_enq, enq_pos, src, len, &f->ooo_enq);
+
+  return 0;
+}
+
+/**
+ * Advance tail
+ */
+void
+svm_fifo_enqueue_nocopy (svm_fifo_t * f, u32 len)
+{
+  u32 tail;
+
+  ASSERT (len <= svm_fifo_max_enqueue_prod (f));
+  /* load-relaxed: producer owned index */
+  tail = f->tail;
+  tail = tail + 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
+    {
+      f->tail_chunk = svm_fifo_find_next_chunk (f, f->tail_chunk, tail);
+    }
+
+  /* store-rel: producer owned index (paired with load-acq in consumer) */
+  clib_atomic_store_rel_n (&f->tail, tail);
+}
+
+int
+svm_fifo_enqueue_segments (svm_fifo_t * f, const svm_fifo_seg_t segs[],
+			   u32 n_segs, u8 allow_partial)
+{
+  u32 tail, head, free_count, len = 0, i;
+  svm_fifo_chunk_t *old_tail_c;
+
+  f->ooos_newest = OOO_SEGMENT_INVALID_INDEX;
+
+  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);
+
+  if (PREDICT_FALSE (free_count == 0))
+    return SVM_FIFO_EFULL;
+
+  for (i = 0; i < n_segs; i++)
+    len += segs[i].len;
+
+  old_tail_c = f->tail_chunk;
+
+  if (!allow_partial)
+    {
+      if (PREDICT_FALSE (free_count < len))
+	return SVM_FIFO_EFULL;
+
+      if (f_pos_gt (tail + len, f_chunk_end (f->end_chunk)))
+	{
+	  if (PREDICT_FALSE (f_try_chunk_alloc (f, head, tail, len)))
+	    return SVM_FIFO_EGROW;
+	}
+
+      for (i = 0; i < n_segs; i++)
+	{
+	  svm_fifo_copy_to_chunk (f, f->tail_chunk, tail, segs[i].data,
+				  segs[i].len, &f->tail_chunk);
+	  tail += segs[i].len;
+	}
+    }
+  else
+    {
+      len = clib_min (free_count, len);
+
+      if (f_pos_gt (tail + len, f_chunk_end (f->end_chunk)))
+	{
+	  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;
+	    }
+	}
+
+      i = 0;
+      while (len)
+	{
+	  u32 to_copy = clib_min (segs[i].len, len);
+	  svm_fifo_copy_to_chunk (f, f->tail_chunk, tail, segs[i].data,
+				  to_copy, &f->tail_chunk);
+	  len -= to_copy;
+	  tail += to_copy;
+	  i++;
+	}
+    }
+
+  /* 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;
+}
+
+always_inline svm_fifo_chunk_t *
+f_unlink_chunks (svm_fifo_t * f, u32 end_pos, u8 maybe_ooo)
+{
+  svm_fifo_chunk_t *start, *prev = 0, *c;
+  rb_tree_t *rt;
+  rb_node_t *n;
+
+  ASSERT (!f_chunk_includes_pos (f->start_chunk, end_pos));
+
+  if (maybe_ooo)
+    rt = &f->ooo_deq_lookup;
+
+  c = f->start_chunk;
+
+  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));
+
+  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;
+    }
+
+  /* Avoid unlinking the last chunk */
+  if (!prev)
+    return 0;
+
+  prev->next = 0;
+  start = f->start_chunk;
+  f->start_chunk = c;
+
+  return start;
+}
+
+int
+svm_fifo_dequeue (svm_fifo_t * f, u32 len, u8 * dst)
+{
+  u32 tail, head, cursize;
+
+  f_load_head_tail_cons (f, &head, &tail);
+
+  /* current size of fifo can only increase during dequeue: SPSC */
+  cursize = f_cursize (f, head, tail);
+
+  if (PREDICT_FALSE (cursize == 0))
+    return SVM_FIFO_EEMPTY;
+
+  len = clib_min (cursize, 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;
+
+  /* In order dequeues are not supported in combination with ooo peeking.
+   * Use svm_fifo_dequeue_drop instead. */
+  ASSERT (rb_tree_n_nodes (&f->ooo_deq_lookup) <= 1);
+
+  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);
+
+  return len;
+}
+
+int
+svm_fifo_peek (svm_fifo_t * f, u32 offset, u32 len, u8 * dst)
+{
+  u32 tail, head, cursize, head_idx;
+
+  f_load_head_tail_cons (f, &head, &tail);
+
+  /* current size of fifo can only increase during peek: SPSC */
+  cursize = f_cursize (f, head, tail);
+
+  if (PREDICT_FALSE (cursize < offset))
+    return SVM_FIFO_EEMPTY;
+
+  len = clib_min (cursize - offset, len);
+  head_idx = head + offset;
+
+  CLIB_MEM_UNPOISON (f->ooo_deq, sizeof (*f->ooo_deq));
+  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 len)
+{
+  u32 total_drop_bytes, tail, head, cursize;
+
+  f_load_head_tail_cons (f, &head, &tail);
+
+  /* number of bytes available */
+  cursize = f_cursize (f, head, tail);
+  if (PREDICT_FALSE (cursize == 0))
+    return SVM_FIFO_EEMPTY;
+
+  /* number of bytes we're going to drop */
+  total_drop_bytes = clib_min (cursize, len);
+
+  svm_fifo_trace_add (f, tail, total_drop_bytes, 3);
+
+  /* move head */
+  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 (f->head <= nitems);
-  ASSERT (cursize >= total_drop_bytes);
-  __sync_fetch_and_sub (&f->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)
+{
+  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, u32 offset, svm_fifo_seg_t * fs,
+		   u32 n_segs, u32 max_bytes)
+{
+  u32 cursize, to_read, head, tail, fs_index = 1;
+  u32 n_bytes, head_pos, len, start;
+  svm_fifo_chunk_t *c;
+
+  f_load_head_tail_cons (f, &head, &tail);
+
+  /* consumer function, cursize can only increase while we're working */
+  cursize = f_cursize (f, head, tail);
+
+  if (PREDICT_FALSE (cursize == 0))
+    return SVM_FIFO_EEMPTY;
+
+  if (offset >= cursize)
+    return SVM_FIFO_EEMPTY;
+
+  to_read = clib_min (cursize - offset, max_bytes);
+  start = head + offset;
+
+  if (!f->head_chunk)
+    f->head_chunk = svm_fifo_find_chunk (f, head);
+
+  c = f->head_chunk;
+
+  while (!f_chunk_includes_pos (c, start))
+    c = c->next;
+
+  head_pos = start - c->start_byte;
+  fs[0].data = c->data + head_pos;
+  fs[0].len = clib_min (c->length - head_pos, cursize - offset);
+  n_bytes = fs[0].len;
+
+  while (n_bytes < to_read && fs_index < n_segs)
+    {
+      c = c->next;
+      len = clib_min (c->length, to_read - n_bytes);
+      fs[fs_index].data = c->data;
+      fs[fs_index].len = len;
+      n_bytes += len;
+      fs_index += 1;
+    }
+
+  return n_bytes;
+}
+
+/**
+ * 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);
+  clib_atomic_store_rel_n (&df->head, head);
+  clib_atomic_store_rel_n (&df->tail, tail);
+}
+
 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);
 }
@@ -815,11 +1307,299 @@ svm_fifo_first_ooo_segment (svm_fifo_t * f)
  * Set fifo pointers to requested offset
  */
 void
-svm_fifo_init_pointers (svm_fifo_t * f, u32 pointer)
+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);
+
+  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
+svm_fifo_add_subscriber (svm_fifo_t * f, u8 subscriber)
+{
+  if (f->n_subscribers >= SVM_FIFO_MAX_EVT_SUBSCRIBERS)
+    return;
+  f->subscribers[f->n_subscribers++] = subscriber;
+}
+
+void
+svm_fifo_del_subscriber (svm_fifo_t * f, u8 subscriber)
+{
+  int i;
+
+  for (i = 0; i < f->n_subscribers; i++)
+    {
+      if (f->subscribers[i] != subscriber)
+	continue;
+      f->subscribers[i] = f->subscribers[f->n_subscribers - 1];
+      f->n_subscribers--;
+      break;
+    }
+}
+
+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)
 {
-  f->head = f->tail = pointer % f->nitems;
+  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 *placeholder_fifo;
+
+  if (!f)
+    return s;
+
+#if SVM_FIFO_TRACE
+  trace = f->trace;
+  trace_len = vec_len (trace);
+#else
+  trace = 0;
+  trace_len = 0;
+#endif
+
+  placeholder_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 (placeholder_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 (placeholder_fifo, trace[i].len, &data[offset]);
+	}
+      else if (!no_read)
+	{
+	  if (verbose)
+	    s = format (s, "read: %u", trace[i].len);
+	  svm_fifo_dequeue_drop (placeholder_fifo, trace[i].len);
+	}
+      if (verbose)
+	s = format (s, "%U", format_svm_fifo, placeholder_fifo, 1);
+    }
+
+  s = format (s, "result: %U", format_svm_fifo, placeholder_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
  *