session: optimize ct fifo segment allocations
[vpp.git] / src / vnet / session / segment_manager.c
index 8dd7292..a7ce989 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 Cisco and/or its affiliates.
+ * Copyright (c) 2017-2019 Cisco and/or its affiliates.
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at:
 #include <vnet/session/session.h>
 #include <vnet/session/application.h>
 
-segment_manager_main_t segment_manager_main;
-
-/**
- * Counter used to build segment names
- */
-static u32 segment_name_counter = 0;
-
-/**
- * Default fifo and segment size. TODO config.
- */
-static u32 default_fifo_size = 1 << 12;
-static u32 default_segment_size = 1 << 20;
-static u32 default_app_evt_queue_size = 128;
+typedef struct segment_manager_main_
+{
+  segment_manager_t *segment_managers; /**< Pool of segment managers */
+  u32 seg_name_counter;                        /**< Counter for segment names */
 
-segment_manager_properties_t *
+  /*
+   * Configuration
+   */
+  u32 default_fifo_size;       /**< default rx/tx fifo size */
+  u32 default_segment_size;    /**< default fifo segment size */
+  u32 default_app_mq_size;     /**< default app msg q size */
+  u32 default_max_fifo_size;   /**< default max fifo size */
+  u8 default_high_watermark;   /**< default high watermark % */
+  u8 default_low_watermark;    /**< default low watermark % */
+} segment_manager_main_t;
+
+static segment_manager_main_t sm_main;
+
+#define segment_manager_foreach_segment_w_lock(VAR, SM, BODY)          \
+do {                                                                   \
+    clib_rwlock_reader_lock (&(SM)->segments_rwlock);                  \
+    pool_foreach((VAR), ((SM)->segments)) (BODY);                      \
+    clib_rwlock_reader_unlock (&(SM)->segments_rwlock);                        \
+} while (0)
+
+static segment_manager_props_t *
 segment_manager_properties_get (segment_manager_t * sm)
 {
   app_worker_t *app_wrk = app_worker_get (sm->app_wrk_index);
   return application_get_segment_manager_properties (app_wrk->app_index);
 }
 
-segment_manager_properties_t *
-segment_manager_properties_init (segment_manager_properties_t * props)
+segment_manager_props_t *
+segment_manager_props_init (segment_manager_props_t * props)
 {
-  props->add_segment_size = default_segment_size;
-  props->rx_fifo_size = default_fifo_size;
-  props->tx_fifo_size = default_fifo_size;
-  props->evt_q_size = default_app_evt_queue_size;
+  props->add_segment_size = sm_main.default_segment_size;
+  props->rx_fifo_size = sm_main.default_fifo_size;
+  props->tx_fifo_size = sm_main.default_fifo_size;
+  props->evt_q_size = sm_main.default_app_mq_size;
+  props->max_fifo_size = sm_main.default_max_fifo_size;
+  props->high_watermark = sm_main.default_high_watermark;
+  props->low_watermark = sm_main.default_low_watermark;
+  props->n_slices = vlib_num_workers () + 1;
   return props;
 }
 
-static u8
+u8
 segment_manager_app_detached (segment_manager_t * sm)
 {
-  return (sm->app_wrk_index == SEGMENT_MANAGER_INVALID_APP_INDEX);
+  return (sm->flags & SEG_MANAGER_F_DETACHED);
 }
 
 void
 segment_manager_app_detach (segment_manager_t * sm)
 {
-  sm->app_wrk_index = SEGMENT_MANAGER_INVALID_APP_INDEX;
+  sm->flags |= SEG_MANAGER_F_DETACHED;
 }
 
 always_inline u32
-segment_manager_segment_index (segment_manager_t * sm,
-                              svm_fifo_segment_private_t * seg)
+segment_manager_segment_index (segment_manager_t * sm, fifo_segment_t * seg)
 {
   return (seg - sm->segments);
 }
 
+/**
+ * Adds segment to segment manager's pool
+ *
+ * If needed a writer's lock is acquired before allocating a new segment
+ * to avoid affecting any of the segments pool readers.
+ */
+int
+segment_manager_add_segment (segment_manager_t *sm, uword segment_size,
+                            u8 notify_app)
+{
+  segment_manager_main_t *smm = &sm_main;
+  segment_manager_props_t *props;
+  fifo_segment_t *fs;
+  u32 fs_index = ~0;
+  u8 *seg_name;
+  int rv;
+
+  props = segment_manager_properties_get (sm);
+
+  /* Not configured for addition of new segments and not first */
+  if (!props->add_segment && !segment_size)
+    {
+      clib_warning ("cannot allocate new segment");
+      return VNET_API_ERROR_INVALID_VALUE;
+    }
+
+  /*
+   * Allocate fifo segment and grab lock if needed
+   */
+  if (vlib_num_workers ())
+    clib_rwlock_writer_lock (&sm->segments_rwlock);
+
+  pool_get_zero (sm->segments, fs);
+
+  /*
+   * Allocate ssvm segment
+   */
+  segment_size = segment_size ? segment_size : props->add_segment_size;
+  segment_size = round_pow2 (segment_size, clib_mem_get_page_size ());
+
+  if (props->segment_type != SSVM_SEGMENT_PRIVATE)
+    {
+      seg_name = format (0, "%d-%d%c", getpid (), smm->seg_name_counter++, 0);
+    }
+  else
+    {
+      app_worker_t *app_wrk = app_worker_get (sm->app_wrk_index);
+      application_t *app = application_get (app_wrk->app_index);
+      seg_name = format (0, "%v segment%c", app->name, 0);
+    }
+
+  fs->ssvm.ssvm_size = segment_size;
+  fs->ssvm.name = seg_name;
+  fs->ssvm.requested_va = 0;
+
+  if ((rv = ssvm_server_init (&fs->ssvm, props->segment_type)))
+    {
+      clib_warning ("svm_master_init ('%v', %u) failed", seg_name,
+                   segment_size);
+      pool_put (sm->segments, fs);
+      goto done;
+    }
+
+  /*
+   * Initialize fifo segment
+   */
+  fs->n_slices = props->n_slices;
+  fifo_segment_init (fs);
+
+  /*
+   * Save segment index before dropping lock, if any held
+   */
+  fs_index = fs - sm->segments;
+
+  /*
+   * Set watermarks in segment
+   */
+  fs->h->high_watermark = sm->high_watermark;
+  fs->h->low_watermark = sm->low_watermark;
+  fs->h->pct_first_alloc = props->pct_first_alloc;
+  fs->h->flags &= ~FIFO_SEGMENT_F_MEM_LIMIT;
+
+  if (notify_app)
+    {
+      app_worker_t *app_wrk;
+      u64 fs_handle;
+      fs_handle = segment_manager_segment_handle (sm, fs);
+      app_wrk = app_worker_get (sm->app_wrk_index);
+      rv = app_worker_add_segment_notify (app_wrk, fs_handle);
+      if (rv)
+       return rv;
+    }
+done:
+
+  if (vlib_num_workers ())
+    clib_rwlock_writer_unlock (&sm->segments_rwlock);
+
+  return fs_index;
+}
+
 /**
  * Remove segment without lock
  */
 void
-segment_manager_del_segment (segment_manager_t * sm,
-                            svm_fifo_segment_private_t * fs)
+segment_manager_del_segment (segment_manager_t * sm, fifo_segment_t * fs)
 {
-  segment_manager_main_t *smm = &segment_manager_main;
-
   if (ssvm_type (&fs->ssvm) != SSVM_SEGMENT_PRIVATE)
-    clib_valloc_free (&smm->va_allocator, fs->ssvm.requested_va);
+    {
+      if (!segment_manager_app_detached (sm))
+       {
+         app_worker_t *app_wrk;
+         u64 segment_handle;
+         app_wrk = app_worker_get (sm->app_wrk_index);
+         segment_handle = segment_manager_segment_handle (sm, fs);
+         app_worker_del_segment_notify (app_wrk, segment_handle);
+       }
+    }
 
+  fifo_segment_cleanup (fs);
   ssvm_delete (&fs->ssvm);
 
   if (CLIB_DEBUG)
-    memset (fs, 0xfb, sizeof (*fs));
+    clib_memset (fs, 0xfb, sizeof (*fs));
   pool_put (sm->segments, fs);
 }
 
+static fifo_segment_t *
+segment_manager_get_segment_if_valid (segment_manager_t * sm,
+                                     u32 segment_index)
+{
+  if (pool_is_free_index (sm->segments, segment_index))
+    return 0;
+  return pool_elt_at_index (sm->segments, segment_index);
+}
+
 /**
  * Removes segment after acquiring writer lock
  */
 static inline void
-segment_manager_lock_and_del_segment (segment_manager_t * sm, u32 fs_index)
+sm_lock_and_del_segment_inline (segment_manager_t * sm, u32 fs_index)
 {
-  svm_fifo_segment_private_t *fs;
+  fifo_segment_t *fs;
   u8 is_prealloc;
 
   clib_rwlock_writer_lock (&sm->segments_rwlock);
-  fs = segment_manager_get_segment (sm, fs_index);
-  is_prealloc = svm_fifo_segment_flags (fs) & FIFO_SEGMENT_F_IS_PREALLOCATED;
+
+  fs = segment_manager_get_segment_if_valid (sm, fs_index);
+  if (!fs)
+    goto done;
+
+  is_prealloc = fifo_segment_flags (fs) & FIFO_SEGMENT_F_IS_PREALLOCATED;
   if (is_prealloc && !segment_manager_app_detached (sm))
-    {
-      clib_rwlock_writer_unlock (&sm->segments_rwlock);
-      return;
-    }
+    goto done;
 
   segment_manager_del_segment (sm, fs);
+
+done:
   clib_rwlock_writer_unlock (&sm->segments_rwlock);
 }
 
+void
+segment_manager_lock_and_del_segment (segment_manager_t * sm, u32 fs_index)
+{
+  sm_lock_and_del_segment_inline (sm, fs_index);
+}
+
 /**
  * Reads a segment from the segment manager's pool without lock
  */
-svm_fifo_segment_private_t *
+fifo_segment_t *
 segment_manager_get_segment (segment_manager_t * sm, u32 segment_index)
 {
   return pool_elt_at_index (sm->segments, segment_index);
 }
 
+u64
+segment_manager_segment_handle (segment_manager_t * sm,
+                               fifo_segment_t * segment)
+{
+  u32 segment_index = segment_manager_segment_index (sm, segment);
+  return (((u64) segment_manager_index (sm) << 32) | segment_index);
+}
+
+u64
+segment_manager_make_segment_handle (u32 segment_manager_index,
+                                    u32 segment_index)
+{
+  return (((u64) segment_manager_index << 32) | segment_index);
+}
+
+fifo_segment_t *
+segment_manager_get_segment_w_handle (u64 segment_handle)
+{
+  u32 sm_index, segment_index;
+  segment_manager_t *sm;
+
+  segment_manager_parse_segment_handle (segment_handle, &sm_index,
+                                       &segment_index);
+  sm = segment_manager_get (sm_index);
+  if (!sm || pool_is_free_index (sm->segments, segment_index))
+    return 0;
+  return pool_elt_at_index (sm->segments, segment_index);
+}
+
 /**
  * Reads a segment from the segment manager's pool and acquires reader lock
  *
@@ -124,17 +292,22 @@ segment_manager_get_segment (segment_manager_t * sm, u32 segment_index)
  * @ref segment_manager_segment_reader_unlock once it finishes working with
  * the segment.
  */
-svm_fifo_segment_private_t *
+fifo_segment_t *
 segment_manager_get_segment_w_lock (segment_manager_t * sm, u32 segment_index)
 {
   clib_rwlock_reader_lock (&sm->segments_rwlock);
   return pool_elt_at_index (sm->segments, segment_index);
 }
 
+void
+segment_manager_segment_reader_lock (segment_manager_t * sm)
+{
+  clib_rwlock_reader_lock (&sm->segments_rwlock);
+}
+
 void
 segment_manager_segment_reader_unlock (segment_manager_t * sm)
 {
-  ASSERT (sm->segments_rwlock->n_readers > 0);
   clib_rwlock_reader_unlock (&sm->segments_rwlock);
 }
 
@@ -144,103 +317,32 @@ segment_manager_segment_writer_unlock (segment_manager_t * sm)
   clib_rwlock_writer_unlock (&sm->segments_rwlock);
 }
 
-/**
- * Adds segment to segment manager's pool
- *
- * If needed a writer's lock is acquired before allocating a new segment
- * to avoid affecting any of the segments pool readers.
- */
-int
-segment_manager_add_segment (segment_manager_t * sm, u32 segment_size)
+segment_manager_t *
+segment_manager_alloc (void)
 {
-  segment_manager_main_t *smm = &segment_manager_main;
-  u32 rnd_margin = 128 << 10, seg_index, page_size;
-  segment_manager_properties_t *props;
-  uword baseva = (u64) ~ 0, alloc_size;
-  svm_fifo_segment_private_t *seg;
-  u8 *seg_name;
-  int rv;
-
-  props = segment_manager_properties_get (sm);
-
-  /* Not configured for addition of new segments and not first */
-  if (!props->add_segment && !segment_size)
-    {
-      clib_warning ("cannot allocate new segment");
-      return VNET_API_ERROR_INVALID_VALUE;
-    }
-
-  /*
-   * Allocate fifo segment and lock if needed
-   */
-  if (vlib_num_workers ())
-    {
-      clib_rwlock_writer_lock (&sm->segments_rwlock);
-      pool_get (sm->segments, seg);
-    }
-  else
-    {
-      pool_get (sm->segments, seg);
-    }
-  memset (seg, 0, sizeof (*seg));
-
-  /*
-   * Initialize ssvm segment and svm fifo private header
-   */
-  segment_size = segment_size ? segment_size : props->add_segment_size;
-  page_size = clib_mem_get_page_size ();
-  segment_size = (segment_size + page_size - 1) & ~(page_size - 1);
-  if (props->segment_type != SSVM_SEGMENT_PRIVATE)
-    {
-      seg_name = format (0, "%d-%d%c", getpid (), segment_name_counter++, 0);
-      alloc_size = (uword) segment_size + rnd_margin;
-      baseva = clib_valloc_alloc (&smm->va_allocator, alloc_size, 0);
-      if (!baseva)
-       {
-         clib_warning ("out of space for segments");
-         return -1;
-       }
-    }
-  else
-    seg_name = format (0, "%s%c", "process-private-segment", 0);
-
-  seg->ssvm.ssvm_size = segment_size;
-  seg->ssvm.name = seg_name;
-  seg->ssvm.requested_va = baseva;
-
-  if ((rv = ssvm_master_init (&seg->ssvm, props->segment_type)))
-    {
-      clib_warning ("svm_master_init ('%v', %u) failed", seg_name,
-                   segment_size);
-
-      if (props->segment_type != SSVM_SEGMENT_PRIVATE)
-       clib_valloc_free (&smm->va_allocator, baseva);
-      pool_put (sm->segments, seg);
-      return (rv);
-    }
+  segment_manager_main_t *smm = &sm_main;
+  segment_manager_t *sm;
 
-  svm_fifo_segment_init (seg);
+  pool_get_zero (smm->segment_managers, sm);
+  clib_rwlock_init (&sm->segments_rwlock);
+  return sm;
+}
 
-  /*
-   * Save segment index before dropping lock, if any held
-   */
-  seg_index = seg - sm->segments;
+int
+segment_manager_init (segment_manager_t * sm)
+{
+  segment_manager_props_t *props;
 
-  if (vlib_num_workers ())
-    clib_rwlock_writer_unlock (&sm->segments_rwlock);
+  props = segment_manager_properties_get (sm);
 
-  return seg_index;
-}
+  sm->max_fifo_size = props->max_fifo_size ?
+    props->max_fifo_size : sm_main.default_max_fifo_size;
+  sm->max_fifo_size = clib_max (sm->max_fifo_size, 4096);
 
-segment_manager_t *
-segment_manager_new ()
-{
-  segment_manager_main_t *smm = &segment_manager_main;
-  segment_manager_t *sm;
-  pool_get (smm->segment_managers, sm);
-  memset (sm, 0, sizeof (*sm));
-  clib_rwlock_init (&sm->segments_rwlock);
-  return sm;
+  segment_manager_set_watermarks (sm,
+                                 props->high_watermark,
+                                 props->low_watermark);
+  return 0;
 }
 
 /**
@@ -248,22 +350,26 @@ segment_manager_new ()
  * Returns error if ssvm segment(s) allocation fails.
  */
 int
-segment_manager_init (segment_manager_t * sm, u32 first_seg_size,
-                     u32 prealloc_fifo_pairs)
+segment_manager_init_first (segment_manager_t * sm)
 {
-  u32 rx_fifo_size, tx_fifo_size, pair_size;
-  u32 rx_rounded_data_size, tx_rounded_data_size;
-  u64 approx_total_size, max_seg_size = ((u64) 1 << 32) - (128 << 10);
-  segment_manager_properties_t *props;
-  svm_fifo_segment_private_t *segment;
-  u32 approx_segment_count;
-  int seg_index, i;
+  segment_manager_props_t *props;
+  uword first_seg_size;
+  fifo_segment_t *fs;
+  int fs_index, i;
 
+  segment_manager_init (sm);
   props = segment_manager_properties_get (sm);
-  first_seg_size = clib_max (first_seg_size, default_segment_size);
+  first_seg_size = clib_max (props->segment_size,
+                            sm_main.default_segment_size);
 
-  if (prealloc_fifo_pairs)
+  if (props->prealloc_fifos)
     {
+      u64 approx_total_size, max_seg_size = ((u64) 1 << 32) - (128 << 10);
+      u32 rx_rounded_data_size, tx_rounded_data_size;
+      u32 prealloc_fifo_pairs = props->prealloc_fifos;
+      u32 rx_fifo_size, tx_fifo_size, pair_size;
+      u32 approx_segment_count;
+
       /* Figure out how many segments should be preallocated */
       rx_rounded_data_size = (1 << (max_log2 (props->rx_fifo_size)));
       tx_rounded_data_size = (1 << (max_log2 (props->tx_fifo_size)));
@@ -281,57 +387,183 @@ segment_manager_init (segment_manager_t * sm, u32 first_seg_size,
       /* Allocate the segments */
       for (i = 0; i < approx_segment_count + 1; i++)
        {
-         seg_index = segment_manager_add_segment (sm, max_seg_size);
-         if (seg_index < 0)
+         fs_index = segment_manager_add_segment (sm, max_seg_size, 0);
+         if (fs_index < 0)
            {
              clib_warning ("Failed to preallocate segment %d", i);
-             return seg_index;
+             return fs_index;
            }
 
-         segment = segment_manager_get_segment (sm, seg_index);
+         fs = segment_manager_get_segment (sm, fs_index);
          if (i == 0)
-           sm->event_queue = segment_manager_alloc_queue (segment, props);
+           sm->event_queue = segment_manager_alloc_queue (fs, props);
 
-         svm_fifo_segment_preallocate_fifo_pairs (segment,
-                                                  props->rx_fifo_size,
-                                                  props->tx_fifo_size,
-                                                  &prealloc_fifo_pairs);
-         svm_fifo_segment_flags (segment) = FIFO_SEGMENT_F_IS_PREALLOCATED;
+         fifo_segment_preallocate_fifo_pairs (fs,
+                                              props->rx_fifo_size,
+                                              props->tx_fifo_size,
+                                              &prealloc_fifo_pairs);
+         fifo_segment_flags (fs) = FIFO_SEGMENT_F_IS_PREALLOCATED;
          if (prealloc_fifo_pairs == 0)
            break;
        }
+      return 0;
     }
-  else
+
+  fs_index = segment_manager_add_segment (sm, first_seg_size, 0);
+  if (fs_index < 0)
     {
-      seg_index = segment_manager_add_segment (sm, first_seg_size);
-      if (seg_index)
+      clib_warning ("Failed to allocate segment");
+      return fs_index;
+    }
+
+  fs = segment_manager_get_segment (sm, fs_index);
+  sm->event_queue = segment_manager_alloc_queue (fs, props);
+
+  if (props->prealloc_fifo_hdrs)
+    {
+      u32 hdrs_per_slice;
+
+      /* Do not preallocate on slice associated to main thread */
+      i = (vlib_num_workers ()? 1 : 0);
+      hdrs_per_slice = props->prealloc_fifo_hdrs / (fs->n_slices - i);
+
+      for (; i < fs->n_slices; i++)
        {
-         clib_warning ("Failed to allocate segment");
-         return seg_index;
+         if (fifo_segment_prealloc_fifo_hdrs (fs, i, hdrs_per_slice))
+           return VNET_API_ERROR_SVM_SEGMENT_CREATE_FAIL;
        }
-      segment = segment_manager_get_segment (sm, seg_index);
-      sm->event_queue = segment_manager_alloc_queue (segment, props);
     }
 
   return 0;
 }
 
+void
+segment_manager_cleanup_detached_listener (segment_manager_t * sm)
+{
+  app_worker_t *app_wrk;
+
+  app_wrk = app_worker_get_if_valid (sm->app_wrk_index);
+  if (!app_wrk)
+    return;
+
+  app_worker_del_detached_sm (app_wrk, segment_manager_index (sm));
+}
+
+/**
+ * Cleanup segment manager.
+ */
+void
+segment_manager_free (segment_manager_t * sm)
+{
+  segment_manager_main_t *smm = &sm_main;
+  fifo_segment_t *fifo_segment;
+
+  ASSERT (vlib_get_thread_index () == 0
+         && !segment_manager_has_fifos (sm)
+         && segment_manager_app_detached (sm));
+
+  if (sm->flags & SEG_MANAGER_F_DETACHED_LISTENER)
+    segment_manager_cleanup_detached_listener (sm);
+
+  /* If we have empty preallocated segments that haven't been removed, remove
+   * them now. Apart from that, the first segment in the first segment manager
+   * is not removed when all fifos are removed. It can only be removed when
+   * the manager is explicitly deleted/detached by the app. */
+  clib_rwlock_writer_lock (&sm->segments_rwlock);
+
+  /* *INDENT-OFF* */
+  pool_foreach (fifo_segment, sm->segments)  {
+    segment_manager_del_segment (sm, fifo_segment);
+  }
+  /* *INDENT-ON* */
+
+  pool_free (sm->segments);
+  clib_rwlock_writer_unlock (&sm->segments_rwlock);
+
+  clib_rwlock_free (&sm->segments_rwlock);
+  if (CLIB_DEBUG)
+    clib_memset (sm, 0xfe, sizeof (*sm));
+  pool_put (smm->segment_managers, sm);
+}
+
+static void
+sm_free_w_index_helper (void *arg)
+{
+  u32 sm_index = *(u32 *) arg;
+  segment_manager_t *sm;
+
+  ASSERT (vlib_get_thread_index () == 0);
+
+  if ((sm = segment_manager_get_if_valid (sm_index)))
+    segment_manager_free (sm);
+}
+
+void
+segment_manager_free_safe (segment_manager_t *sm)
+{
+  if (!vlib_thread_is_main_w_barrier ())
+    {
+      u32 sm_index = segment_manager_index (sm);
+      vlib_rpc_call_main_thread (sm_free_w_index_helper, (u8 *) & sm_index,
+                                sizeof (sm_index));
+    }
+  else
+    {
+      segment_manager_free (sm);
+    }
+}
+
+void
+segment_manager_init_free (segment_manager_t * sm)
+{
+  ASSERT (vlib_get_thread_index () == 0);
+
+  segment_manager_app_detach (sm);
+  if (segment_manager_has_fifos (sm))
+    segment_manager_del_sessions (sm);
+  else
+    {
+      ASSERT (!sm->first_is_protected || segment_manager_app_detached (sm));
+      segment_manager_free (sm);
+    }
+}
+
+segment_manager_t *
+segment_manager_get (u32 index)
+{
+  return pool_elt_at_index (sm_main.segment_managers, index);
+}
+
+segment_manager_t *
+segment_manager_get_if_valid (u32 index)
+{
+  if (pool_is_free_index (sm_main.segment_managers, index))
+    return 0;
+  return pool_elt_at_index (sm_main.segment_managers, index);
+}
+
+u32
+segment_manager_index (segment_manager_t * sm)
+{
+  return sm - sm_main.segment_managers;
+}
+
 u8
 segment_manager_has_fifos (segment_manager_t * sm)
 {
-  svm_fifo_segment_private_t *seg;
+  fifo_segment_t *seg;
   u8 first = 1;
 
   /* *INDENT-OFF* */
   segment_manager_foreach_segment_w_lock (seg, sm, ({
-    if (CLIB_DEBUG && !first && !svm_fifo_segment_has_fifos (seg)
-       && !(svm_fifo_segment_flags (seg) & FIFO_SEGMENT_F_IS_PREALLOCATED))
+    if (CLIB_DEBUG && !first && !fifo_segment_has_fifos (seg)
+       && !(fifo_segment_flags (seg) & FIFO_SEGMENT_F_IS_PREALLOCATED))
       {
        clib_warning ("segment %d has no fifos!",
                      segment_manager_segment_index (sm, seg));
        first = 0;
       }
-    if (svm_fifo_segment_has_fifos (seg))
+    if (fifo_segment_has_fifos (seg))
       {
        segment_manager_segment_reader_unlock (sm);
        return 1;
@@ -348,36 +580,34 @@ segment_manager_has_fifos (segment_manager_t * sm)
 void
 segment_manager_del_sessions (segment_manager_t * sm)
 {
-  svm_fifo_segment_private_t *fifo_segment;
-  stream_session_t *session;
-  svm_fifo_t *fifo;
+  session_handle_t *handles = 0, *handle;
+  fifo_segment_t *fs;
+  session_t *session;
+  int slice_index;
+  svm_fifo_t *f;
 
   ASSERT (pool_elts (sm->segments) != 0);
 
   /* Across all fifo segments used by the server */
   /* *INDENT-OFF* */
-  segment_manager_foreach_segment_w_lock (fifo_segment, sm, ({
-    fifo = svm_fifo_segment_get_fifo_list (fifo_segment);
-
-    /*
-     * Remove any residual sessions from the session lookup table
-     * Don't bother deleting the individual fifos, we're going to
-     * throw away the fifo segment in a minute.
-     */
-    while (fifo)
+  segment_manager_foreach_segment_w_lock (fs, sm, ({
+    for (slice_index = 0; slice_index < fs->n_slices; slice_index++)
       {
-       if (fifo->ct_session_index != SVM_FIFO_INVALID_SESSION_INDEX)
-         {
-           svm_fifo_t *next = fifo->next;
-           application_local_session_disconnect_w_index (sm->app_wrk_index,
-                                                         fifo->ct_session_index);
-           fifo = next;
-           continue;
+        f = fifo_segment_get_slice_fifo_list (fs, slice_index);
+
+        /*
+         * Remove any residual sessions from the session lookup table
+         * Don't bother deleting the individual fifos, we're going to
+         * throw away the fifo segment in a minute.
+         */
+        while (f)
+          {
+           session = session_get_if_valid (f->shr->master_session_index,
+                                           f->master_thread_index);
+           if (session)
+             vec_add1 (handles, session_handle (session));
+           f = f->next;
          }
-       session = session_get (fifo->master_session_index,
-                              fifo->master_thread_index);
-       stream_session_disconnect (session);
-       fifo = fifo->next;
       }
 
     /* Instead of removing the segment, test when cleaning up disconnected
@@ -385,77 +615,92 @@ segment_manager_del_sessions (segment_manager_t * sm)
      */
   }));
   /* *INDENT-ON* */
+
+  vec_foreach (handle, handles)
+  {
+    session = session_get_from_handle (*handle);
+    session_close (session);
+    /* Avoid propagating notifications back to the app */
+    session->app_wrk_index = APP_INVALID_INDEX;
+  }
+  vec_free (handles);
 }
 
 /**
- * Removes segment manager.
- *
- * Since the fifos allocated in the segment keep backpointers to the sessions
- * prior to removing the segment, we call session disconnect. This
- * subsequently propagates into transport.
+ * Initiate disconnects for sessions in specified state 'owned' by a segment
+ * manager
  */
 void
-segment_manager_del (segment_manager_t * sm)
+segment_manager_del_sessions_filter (segment_manager_t *sm,
+                                    session_state_t *states)
 {
-  segment_manager_main_t *smm = &segment_manager_main;
-  svm_fifo_segment_private_t *fifo_segment;
+  session_handle_t *handles = 0, *handle;
+  fifo_segment_t *fs;
+  session_t *session;
+  int slice_index;
+  svm_fifo_t *f;
 
-  ASSERT (!segment_manager_has_fifos (sm)
-         && segment_manager_app_detached (sm));
-
-  /* If we have empty preallocated segments that haven't been removed, remove
-   * them now. Apart from that, the first segment in the first segment manager
-   * is not removed when all fifos are removed. It can only be removed when
-   * the manager is explicitly deleted/detached by the app. */
-  clib_rwlock_writer_lock (&sm->segments_rwlock);
-
-  /* *INDENT-OFF* */
-  pool_foreach (fifo_segment, sm->segments, ({
-    segment_manager_del_segment (sm, fifo_segment);
-  }));
-  /* *INDENT-ON* */
-
-  clib_rwlock_writer_unlock (&sm->segments_rwlock);
+  ASSERT (pool_elts (sm->segments) != 0);
 
-  clib_rwlock_free (&sm->segments_rwlock);
-  if (CLIB_DEBUG)
-    memset (sm, 0xfe, sizeof (*sm));
-  pool_put (smm->segment_managers, sm);
-}
+  /* Across all fifo segments used by the server */
+  segment_manager_foreach_segment_w_lock (
+    fs, sm, ({
+      for (slice_index = 0; slice_index < fs->n_slices; slice_index++)
+       {
+         f = fifo_segment_get_slice_fifo_list (fs, slice_index);
+         while (f)
+           {
+             session = session_get_if_valid (f->shr->master_session_index,
+                                             f->master_thread_index);
+             if (session)
+               {
+                 session_state_t *state;
+                 vec_foreach (state, states)
+                   {
+                     if (session->session_state == *state)
+                       {
+                         vec_add1 (handles, session_handle (session));
+                         break;
+                       }
+                   }
+               }
+             f = f->next;
+           }
+       }
+    }));
 
-void
-segment_manager_init_del (segment_manager_t * sm)
-{
-  segment_manager_app_detach (sm);
-  if (segment_manager_has_fifos (sm))
-    segment_manager_del_sessions (sm);
-  else
+  vec_foreach (handle, handles)
     {
-      ASSERT (!sm->first_is_protected || segment_manager_app_detached (sm));
-      segment_manager_del (sm);
+      session = session_get_from_handle (*handle);
+      session_close (session);
+      /* Avoid propagating notifications back to the app */
+      session->app_wrk_index = APP_INVALID_INDEX;
     }
+  vec_free (handles);
 }
 
 int
-segment_manager_try_alloc_fifos (svm_fifo_segment_private_t * fifo_segment,
+segment_manager_try_alloc_fifos (fifo_segment_t * fifo_segment,
+                                u32 thread_index,
                                 u32 rx_fifo_size, u32 tx_fifo_size,
                                 svm_fifo_t ** rx_fifo, svm_fifo_t ** tx_fifo)
 {
-  rx_fifo_size = clib_max (rx_fifo_size, default_fifo_size);
-  *rx_fifo = svm_fifo_segment_alloc_fifo (fifo_segment, rx_fifo_size,
-                                         FIFO_SEGMENT_RX_FREELIST);
+  rx_fifo_size = clib_max (rx_fifo_size, sm_main.default_fifo_size);
+  *rx_fifo = fifo_segment_alloc_fifo_w_slice (fifo_segment, thread_index,
+                                             rx_fifo_size,
+                                             FIFO_SEGMENT_RX_FIFO);
 
-  tx_fifo_size = clib_max (tx_fifo_size, default_fifo_size);
-  *tx_fifo = svm_fifo_segment_alloc_fifo (fifo_segment, tx_fifo_size,
-                                         FIFO_SEGMENT_TX_FREELIST);
+  tx_fifo_size = clib_max (tx_fifo_size, sm_main.default_fifo_size);
+  *tx_fifo = fifo_segment_alloc_fifo_w_slice (fifo_segment, thread_index,
+                                             tx_fifo_size,
+                                             FIFO_SEGMENT_TX_FIFO);
 
   if (*rx_fifo == 0)
     {
       /* This would be very odd, but handle it... */
       if (*tx_fifo != 0)
        {
-         svm_fifo_segment_free_fifo (fifo_segment, *tx_fifo,
-                                     FIFO_SEGMENT_TX_FREELIST);
+         fifo_segment_free_fifo (fifo_segment, *tx_fifo);
          *tx_fifo = 0;
        }
       return -1;
@@ -464,8 +709,7 @@ segment_manager_try_alloc_fifos (svm_fifo_segment_private_t * fifo_segment,
     {
       if (*rx_fifo != 0)
        {
-         svm_fifo_segment_free_fifo (fifo_segment, *rx_fifo,
-                                     FIFO_SEGMENT_RX_FREELIST);
+         fifo_segment_free_fifo (fifo_segment, *rx_fifo);
          *rx_fifo = 0;
        }
       return -1;
@@ -476,15 +720,15 @@ segment_manager_try_alloc_fifos (svm_fifo_segment_private_t * fifo_segment,
 
 int
 segment_manager_alloc_session_fifos (segment_manager_t * sm,
+                                    u32 thread_index,
                                     svm_fifo_t ** rx_fifo,
-                                    svm_fifo_t ** tx_fifo,
-                                    u32 * fifo_segment_index)
+                                    svm_fifo_t ** tx_fifo)
 {
-  svm_fifo_segment_private_t *fifo_segment = 0;
   int alloc_fail = 1, rv = 0, new_fs_index;
-  segment_manager_properties_t *props;
-  u8 added_a_segment = 0;
-  u32 sm_index;
+  uword free_bytes, max_free_bytes = 0;
+  segment_manager_props_t *props;
+  fifo_segment_t *fs = 0, *cur;
+  u32 sm_index, fs_index;
 
   props = segment_manager_properties_get (sm);
 
@@ -492,87 +736,95 @@ segment_manager_alloc_session_fifos (segment_manager_t * sm,
    * Find the first free segment to allocate the fifos in
    */
 
-  /* *INDENT-OFF* */
-  segment_manager_foreach_segment_w_lock (fifo_segment, sm, ({
-    alloc_fail = segment_manager_try_alloc_fifos (fifo_segment,
-                                                  props->rx_fifo_size,
-                                                  props->tx_fifo_size,
-                                                  rx_fifo, tx_fifo);
-    /* Exit with lock held, drop it after notifying app */
-    if (!alloc_fail)
-      goto alloc_success;
-  }));
-  /* *INDENT-ON* */
+  segment_manager_segment_reader_lock (sm);
 
-alloc_check:
+  pool_foreach (cur, sm->segments)  {
+      if (fifo_segment_flags (cur) & FIFO_SEGMENT_F_CUSTOM_USE)
+       continue;
+      free_bytes = fifo_segment_available_bytes (cur);
+      if (free_bytes > max_free_bytes)
+       {
+         max_free_bytes = free_bytes;
+         fs = cur;
+       }
+  }
 
-  if (!alloc_fail)
+  if (fs)
     {
-
-    alloc_success:
-
-      ASSERT (rx_fifo && tx_fifo);
-      sm_index = segment_manager_index (sm);
-      (*tx_fifo)->segment_manager = sm_index;
-      (*rx_fifo)->segment_manager = sm_index;
-      *fifo_segment_index = segment_manager_segment_index (sm, fifo_segment);
-
-      if (added_a_segment)
-       rv = app_worker_add_segment_notify (sm->app_wrk_index,
-                                           &fifo_segment->ssvm);
-      /* Drop the lock after app is notified */
-      segment_manager_segment_reader_unlock (sm);
-      return rv;
+      alloc_fail = segment_manager_try_alloc_fifos (fs, thread_index,
+                                                   props->rx_fifo_size,
+                                                   props->tx_fifo_size,
+                                                   rx_fifo, tx_fifo);
+      /* On success, keep lock until fifos are initialized */
+      if (!alloc_fail)
+       goto alloc_success;
     }
 
+  segment_manager_segment_reader_unlock (sm);
+
   /*
    * Allocation failed, see if we can add a new segment
    */
   if (props->add_segment)
     {
-      if (added_a_segment)
-       {
-         clib_warning ("Added a segment, still can't allocate a fifo");
-         segment_manager_segment_reader_unlock (sm);
-         return SESSION_ERROR_NEW_SEG_NO_SPACE;
-       }
-      if ((new_fs_index = segment_manager_add_segment (sm, 0)) < 0)
+      if ((new_fs_index = segment_manager_add_segment (sm, 0, 1)) < 0)
        {
          clib_warning ("Failed to add new segment");
-         return SESSION_ERROR_SEG_CREATE;
+         return SESSION_E_SEG_CREATE;
        }
-      fifo_segment = segment_manager_get_segment_w_lock (sm, new_fs_index);
-      alloc_fail = segment_manager_try_alloc_fifos (fifo_segment,
+      fs = segment_manager_get_segment_w_lock (sm, new_fs_index);
+      alloc_fail = segment_manager_try_alloc_fifos (fs, thread_index,
                                                    props->rx_fifo_size,
                                                    props->tx_fifo_size,
                                                    rx_fifo, tx_fifo);
-      added_a_segment = 1;
-      goto alloc_check;
+      if (alloc_fail)
+       {
+         clib_warning ("Added a segment, still can't allocate a fifo");
+         segment_manager_segment_reader_unlock (sm);
+         return SESSION_E_SEG_NO_SPACE2;
+       }
     }
   else
     {
-      clib_warning ("Can't add new seg and no space to allocate fifos!");
-      return SESSION_ERROR_NO_SPACE;
+      SESSION_DBG ("Can't add new seg and no space to allocate fifos!");
+      return SESSION_E_SEG_NO_SPACE;
     }
+
+alloc_success:
+  ASSERT (rx_fifo && tx_fifo);
+
+  sm_index = segment_manager_index (sm);
+  fs_index = segment_manager_segment_index (sm, fs);
+  (*tx_fifo)->segment_manager = sm_index;
+  (*rx_fifo)->segment_manager = sm_index;
+  (*tx_fifo)->segment_index = fs_index;
+  (*rx_fifo)->segment_index = fs_index;
+
+  /* Drop the lock after app is notified */
+  segment_manager_segment_reader_unlock (sm);
+
+  return rv;
 }
 
 void
-segment_manager_dealloc_fifos (u32 segment_index, svm_fifo_t * rx_fifo,
-                              svm_fifo_t * tx_fifo)
+segment_manager_dealloc_fifos (svm_fifo_t * rx_fifo, svm_fifo_t * tx_fifo)
 {
-  svm_fifo_segment_private_t *fifo_segment;
   segment_manager_t *sm;
+  fifo_segment_t *fs;
+  u32 segment_index;
+
+  if (!rx_fifo || !tx_fifo)
+    return;
 
   /* It's possible to have no segment manager if the session was removed
    * as result of a detach. */
   if (!(sm = segment_manager_get_if_valid (rx_fifo->segment_manager)))
     return;
 
-  fifo_segment = segment_manager_get_segment_w_lock (sm, segment_index);
-  svm_fifo_segment_free_fifo (fifo_segment, rx_fifo,
-                             FIFO_SEGMENT_RX_FREELIST);
-  svm_fifo_segment_free_fifo (fifo_segment, tx_fifo,
-                             FIFO_SEGMENT_TX_FREELIST);
+  segment_index = rx_fifo->segment_index;
+  fs = segment_manager_get_segment_w_lock (sm, segment_index);
+  fifo_segment_free_fifo (fs, rx_fifo);
+  fifo_segment_free_fifo (fs, tx_fifo);
 
   /*
    * Try to remove svm segment if it has no fifos. This can be done only if
@@ -580,25 +832,47 @@ segment_manager_dealloc_fifos (u32 segment_index, svm_fifo_t * rx_fifo,
    * and it is not protected. Moreover, if the segment is first and the app
    * has detached from the segment manager, remove the segment manager.
    */
-  if (!svm_fifo_segment_has_fifos (fifo_segment))
+  if (!fifo_segment_has_fifos (fs))
     {
       segment_manager_segment_reader_unlock (sm);
 
       /* Remove segment if it holds no fifos or first but not protected */
       if (segment_index != 0 || !sm->first_is_protected)
-       segment_manager_lock_and_del_segment (sm, segment_index);
+       sm_lock_and_del_segment_inline (sm, segment_index);
 
       /* Remove segment manager if no sessions and detached from app */
       if (segment_manager_app_detached (sm)
          && !segment_manager_has_fifos (sm))
-       {
-         segment_manager_del (sm);
-       }
+       segment_manager_free_safe (sm);
     }
   else
     segment_manager_segment_reader_unlock (sm);
 }
 
+void
+segment_manager_detach_fifo (segment_manager_t *sm, svm_fifo_t **f)
+{
+  fifo_segment_t *fs;
+
+  fs = segment_manager_get_segment_w_lock (sm, (*f)->segment_index);
+  fifo_segment_detach_fifo (fs, f);
+  segment_manager_segment_reader_unlock (sm);
+}
+
+void
+segment_manager_attach_fifo (segment_manager_t *sm, svm_fifo_t **f,
+                            session_t *s)
+{
+  fifo_segment_t *fs;
+
+  fs = segment_manager_get_segment_w_lock (sm, (*f)->segment_index);
+  fifo_segment_attach_fifo (fs, f, s->thread_index);
+  segment_manager_segment_reader_unlock (sm);
+
+  (*f)->shr->master_session_index = s->session_index;
+  (*f)->master_thread_index = s->thread_index;
+}
+
 u32
 segment_manager_evt_q_expected_size (u32 q_len)
 {
@@ -622,13 +896,12 @@ segment_manager_evt_q_expected_size (u32 q_len)
  * Must be called with lock held
  */
 svm_msg_q_t *
-segment_manager_alloc_queue (svm_fifo_segment_private_t * segment,
-                            segment_manager_properties_t * props)
+segment_manager_alloc_queue (fifo_segment_t * segment,
+                            segment_manager_props_t * props)
 {
   u32 fifo_evt_size, session_evt_size = 256, notif_q_size;
   svm_msg_q_cfg_t _cfg, *cfg = &_cfg;
   svm_msg_q_t *q;
-  void *oldheap;
 
   fifo_evt_size = sizeof (session_event_t);
   notif_q_size = clib_max (16, props->evt_q_size >> 4);
@@ -643,25 +916,29 @@ segment_manager_alloc_queue (svm_fifo_segment_private_t * segment,
   cfg->q_nitems = props->evt_q_size;
   cfg->ring_cfgs = rc;
 
-  oldheap = ssvm_push_heap (segment->ssvm.sh);
-  q = svm_msg_q_alloc (cfg);
-  ssvm_pop_heap (oldheap);
+  q = fifo_segment_msg_q_alloc (segment, 0, cfg);
 
   if (props->use_mq_eventfd)
     {
-      if (svm_msg_q_alloc_producer_eventfd (q))
+      if (svm_msg_q_alloc_eventfd (q))
        clib_warning ("failed to alloc eventfd");
     }
   return q;
 }
 
+svm_msg_q_t *
+segment_manager_event_queue (segment_manager_t * sm)
+{
+  return sm->event_queue;
+}
+
 /**
  * Frees shm queue allocated in the first segment
  */
 void
 segment_manager_dealloc_queue (segment_manager_t * sm, svm_queue_t * q)
 {
-  svm_fifo_segment_private_t *segment;
+  fifo_segment_t *segment;
   ssvm_shared_header_t *sh;
   void *oldheap;
 
@@ -680,29 +957,30 @@ segment_manager_dealloc_queue (segment_manager_t * sm, svm_queue_t * q)
  * Init segment vm address allocator
  */
 void
-segment_manager_main_init (segment_manager_main_init_args_t * a)
+segment_manager_main_init (void)
 {
-  segment_manager_main_t *sm = &segment_manager_main;
-  clib_valloc_chunk_t _ip, *ip = &_ip;
-
-  ip->baseva = a->baseva;
-  ip->size = a->size;
-
-  clib_valloc_init (&sm->va_allocator, ip, 1 /* lock */ );
+  segment_manager_main_t *sm = &sm_main;
+
+  sm->default_fifo_size = 1 << 12;
+  sm->default_segment_size = 1 << 20;
+  sm->default_app_mq_size = 128;
+  sm->default_max_fifo_size = 4 << 20;
+  sm->default_high_watermark = 80;
+  sm->default_low_watermark = 50;
 }
 
 static clib_error_t *
 segment_manager_show_fn (vlib_main_t * vm, unformat_input_t * input,
                         vlib_cli_command_t * cmd)
 {
-  segment_manager_main_t *smm = &segment_manager_main;
-  svm_fifo_segment_private_t *seg;
-  segment_manager_t *sm;
+  segment_manager_main_t *smm = &sm_main;
   u8 show_segments = 0, verbose = 0;
-  uword address;
-  u64 size;
-  u32 active_fifos;
-  u32 free_fifos;
+  uword max_fifo_size;
+  segment_manager_t *sm;
+  fifo_segment_t *seg;
+  app_worker_t *app_wrk;
+  application_t *app;
+  u8 custom_logic;
 
   while (unformat_check_input (input) != UNFORMAT_END_OF_INPUT)
     {
@@ -718,36 +996,38 @@ segment_manager_show_fn (vlib_main_t * vm, unformat_input_t * input,
                   pool_elts (smm->segment_managers));
   if (verbose && pool_elts (smm->segment_managers))
     {
-      vlib_cli_output (vm, "%-10s%=15s%=12s", "Index", "App Index",
-                      "Segments");
+      vlib_cli_output (vm, "%-6s%=10s%=10s%=13s%=11s%=11s%=12s",
+                      "Index", "AppIndex", "Segments", "MaxFifoSize",
+                      "HighWater", "LowWater", "FifoTuning");
 
       /* *INDENT-OFF* */
-      pool_foreach (sm, smm->segment_managers, ({
-       vlib_cli_output (vm, "%-10d%=15d%=12d", segment_manager_index (sm),
-                          sm->app_wrk_index, pool_elts (sm->segments));
-      }));
+      pool_foreach (sm, smm->segment_managers)  {
+        app_wrk = app_worker_get_if_valid (sm->app_wrk_index);
+        app = app_wrk ? application_get (app_wrk->app_index) : 0;
+        custom_logic = (app && (app->cb_fns.fifo_tuning_callback)) ? 1 : 0;
+        max_fifo_size = sm->max_fifo_size;
+
+       vlib_cli_output (vm, "%-6d%=10d%=10d%=13U%=11d%=11d%=12s",
+                         segment_manager_index (sm),
+                        sm->app_wrk_index, pool_elts (sm->segments),
+                         format_memory_size, max_fifo_size,
+                         sm->high_watermark, sm->low_watermark,
+                         custom_logic ? "custom" : "none");
+      }
       /* *INDENT-ON* */
 
+      vlib_cli_output (vm, "\n");
     }
   if (show_segments)
     {
-      vlib_cli_output (vm, "%-15s%15s%15s%15s%15s%15s", "Name", "Type",
-                      "HeapSize (M)", "ActiveFifos", "FreeFifos", "Address");
+      vlib_cli_output (vm, "%U", format_fifo_segment, 0, verbose);
 
       /* *INDENT-OFF* */
-      pool_foreach (sm, smm->segment_managers, ({
+      pool_foreach (sm, smm->segment_managers)  {
          segment_manager_foreach_segment_w_lock (seg, sm, ({
-           svm_fifo_segment_info (seg, &address, &size);
-           active_fifos = svm_fifo_segment_num_fifos (seg);
-           free_fifos = svm_fifo_segment_num_free_fifos (seg, ~0 /* size */);
-           vlib_cli_output (vm, "%-15v%15U%15llu%15u%15u%15llx",
-                            ssvm_name (&seg->ssvm), format_svm_fifo_segment_type,
-                            seg, size >> 20ULL, active_fifos, free_fifos,
-                            address);
-           if (verbose)
-             vlib_cli_output (vm, "%U", format_svm_fifo_segment, seg, verbose);
+           vlib_cli_output (vm, "%U", format_fifo_segment, seg, verbose);
          }));
-      }));
+      }
       /* *INDENT-ON* */
 
     }
@@ -763,6 +1043,80 @@ VLIB_CLI_COMMAND (segment_manager_show_command, static) =
 };
 /* *INDENT-ON* */
 
+void
+segment_manager_format_sessions (segment_manager_t * sm, int verbose)
+{
+  vlib_main_t *vm = vlib_get_main ();
+  app_worker_t *app_wrk;
+  fifo_segment_t *fs;
+  const u8 *app_name;
+  int slice_index;
+  u8 *s = 0, *str;
+  svm_fifo_t *f;
+
+  if (!sm)
+    {
+      if (verbose)
+       vlib_cli_output (vm, "%-40s%-20s%-15s%-10s", "Connection", "App",
+                        "API Client", "SegManager");
+      else
+       vlib_cli_output (vm, "%-40s%-20s", "Connection", "App");
+      return;
+    }
+
+  app_wrk = app_worker_get (sm->app_wrk_index);
+  app_name = application_name_from_index (app_wrk->app_index);
+
+  clib_rwlock_reader_lock (&sm->segments_rwlock);
+
+  /* *INDENT-OFF* */
+  pool_foreach (fs, sm->segments)  {
+    for (slice_index = 0; slice_index < fs->n_slices; slice_index++)
+      {
+        f = fifo_segment_get_slice_fifo_list (fs, slice_index);
+        while (f)
+          {
+            u32 session_index, thread_index;
+            session_t *session;
+
+           session_index = f->shr->master_session_index;
+           thread_index = f->master_thread_index;
+
+           session = session_get (session_index, thread_index);
+           str = format (0, "%U", format_session, session, verbose);
+
+           if (verbose)
+             s = format (s, "%-40v%-20v%-15u%-10u", str, app_name,
+                         app_wrk->api_client_index,
+                         app_wrk->connects_seg_manager);
+           else
+             s = format (s, "%-40v%-20v", str, app_name);
+
+           vlib_cli_output (vm, "%v", s);
+           vec_reset_length (s);
+           vec_free (str);
+
+           f = f->next;
+         }
+       vec_free (s);
+      }
+  }
+  /* *INDENT-ON* */
+
+  clib_rwlock_reader_unlock (&sm->segments_rwlock);
+}
+
+void
+segment_manager_set_watermarks (segment_manager_t * sm,
+                               u8 high_watermark, u8 low_watermark)
+{
+  ASSERT (high_watermark <= 100 && low_watermark <= 100 &&
+         low_watermark <= high_watermark);
+
+  sm->high_watermark = high_watermark;
+  sm->low_watermark = low_watermark;
+}
+
 /*
  * fd.io coding-style-patch-verification: ON
  *