session: optimize ct fifo segment allocations
[vpp.git] / src / vnet / session / segment_manager.c
index 83b8388..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>
 
-/**
- * Counter used to build segment names
- */
-u32 segment_name_counter = 0;
-
-/**
- * Pool of segment managers
- */
-segment_manager_t *segment_managers = 0;
-
-/*
- * Pool of segment manager properties
- */
-static segment_manager_properties_t *segment_manager_properties_pool;
-
-/**
- * Process private segment index
- */
-u32 *private_segment_indices;
-
-/**
- * Default fifo and segment size. TODO config.
- */
-u32 default_fifo_size = 1 << 16;
-u32 default_segment_size = 1 << 20;
-
-segment_manager_properties_t *
-segment_manager_properties_alloc (void)
-{
-  segment_manager_properties_t *props;
-  pool_get (segment_manager_properties_pool, props);
-  memset (props, 0, sizeof (*props));
-  props->add_segment_size = default_segment_size;
-  props->rx_fifo_size = default_fifo_size;
-  props->tx_fifo_size = default_fifo_size;
-  return props;
-}
+typedef struct segment_manager_main_
+{
+  segment_manager_t *segment_managers; /**< Pool of segment managers */
+  u32 seg_name_counter;                        /**< Counter for segment names */
 
-void
-segment_manager_properties_free (segment_manager_properties_t * props)
+  /*
+   * 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)
 {
-  pool_put (segment_manager_properties_pool, props);
-  memset (props, 0xFB, sizeof (*props));
+  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_get (u32 smp_index)
+segment_manager_props_t *
+segment_manager_props_init (segment_manager_props_t * props)
 {
-  if (pool_is_free_index (segment_manager_properties_pool, smp_index))
-    return 0;
-  return pool_elt_at_index (segment_manager_properties_pool, smp_index);
+  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;
 }
 
-u32
-segment_manager_properties_index (segment_manager_properties_t * p)
+u8
+segment_manager_app_detached (segment_manager_t * sm)
 {
-  return p - segment_manager_properties_pool;
+  return (sm->flags & SEG_MANAGER_F_DETACHED);
 }
 
-svm_fifo_segment_private_t *
-segment_manager_get_segment (u32 segment_index)
+void
+segment_manager_app_detach (segment_manager_t * sm)
 {
-  return svm_fifo_segment_get_segment (segment_index);
+  sm->flags |= SEG_MANAGER_F_DETACHED;
 }
 
-void
-segment_manager_get_segment_info (u32 index, u8 ** name, u32 * size)
+always_inline u32
+segment_manager_segment_index (segment_manager_t * sm, fifo_segment_t * seg)
 {
-  svm_fifo_segment_private_t *s;
-  s = svm_fifo_segment_get_segment (index);
-  *name = s->ssvm.name;
-  *size = s->ssvm.ssvm_size;
+  return (seg - sm->segments);
 }
 
-always_inline int
-segment_manager_add_segment_i (segment_manager_t * sm, u32 segment_size,
-                              u32 protected_space)
+/**
+ * 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)
 {
-  svm_fifo_segment_create_args_t _ca = { 0 }, *ca = &_ca;
-  segment_manager_properties_t *props;
+  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->properties_index);
+  props = segment_manager_properties_get (sm);
 
   /* Not configured for addition of new segments and not first */
   if (!props->add_segment && !segment_size)
@@ -107,387 +107,724 @@ segment_manager_add_segment_i (segment_manager_t * sm, u32 segment_size,
       return VNET_API_ERROR_INVALID_VALUE;
     }
 
-  ca->segment_size = segment_size ? segment_size : props->add_segment_size;
-  ca->rx_fifo_size = props->rx_fifo_size;
-  ca->tx_fifo_size = props->tx_fifo_size;
-  ca->preallocated_fifo_pairs = props->preallocated_fifo_pairs;
-  ca->seg_protected_space = protected_space ? protected_space : 0;
+  /*
+   * 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_N_SEGMENT_TYPES)
+  if (props->segment_type != SSVM_SEGMENT_PRIVATE)
     {
-      ca->segment_name = (char *) format (0, "%d-%d%c", getpid (),
-                                         segment_name_counter++, 0);
-      ca->segment_type = props->segment_type;
-      if (svm_fifo_segment_create (ca))
-       {
-         clib_warning ("svm_fifo_segment_create ('%s', %d) failed",
-                       ca->segment_name, ca->segment_size);
-         return VNET_API_ERROR_SVM_SEGMENT_CREATE_FAIL;
-       }
-      vec_free (ca->segment_name);
+      seg_name = format (0, "%d-%d%c", getpid (), smm->seg_name_counter++, 0);
     }
   else
     {
-      u32 rx_fifo_size, tx_fifo_size;
-      u32 rx_rounded_data_size, tx_rounded_data_size;
-      u32 approx_segment_count;
-      u64 approx_total_size;
+      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);
+    }
 
-      ca->segment_name = "process-private-segment";
-      ca->private_segment_count = props->private_segment_count;
+  fs->ssvm.ssvm_size = segment_size;
+  fs->ssvm.name = seg_name;
+  fs->ssvm.requested_va = 0;
 
-      /* Calculate space requirements */
-      rx_rounded_data_size = (1 << (max_log2 (ca->rx_fifo_size)));
-      tx_rounded_data_size = (1 << (max_log2 (ca->tx_fifo_size)));
+  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;
+    }
 
-      rx_fifo_size = sizeof (svm_fifo_t) + rx_rounded_data_size;
-      tx_fifo_size = sizeof (svm_fifo_t) + tx_rounded_data_size;
+  /*
+   * Initialize fifo segment
+   */
+  fs->n_slices = props->n_slices;
+  fifo_segment_init (fs);
 
-      approx_total_size = (u64) ca->preallocated_fifo_pairs
-       * (rx_fifo_size + tx_fifo_size);
-      approx_segment_count = (approx_total_size + protected_space
-                             + (ca->segment_size -
-                                1)) / (u64) ca->segment_size;
+  /*
+   * Save segment index before dropping lock, if any held
+   */
+  fs_index = fs - sm->segments;
 
-      /* The user asked us to figure it out... */
-      if (ca->private_segment_count == 0
-         || approx_segment_count < ca->private_segment_count)
-       {
-         ca->private_segment_count = approx_segment_count;
-       }
-      /* Follow directions, but issue a warning */
-      else if (approx_segment_count < ca->private_segment_count)
-       {
-         clib_warning ("Honoring segment count %u, calculated count was %u",
-                       ca->private_segment_count, approx_segment_count);
-       }
-      else if (approx_segment_count > ca->private_segment_count)
+  /*
+   * 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, fifo_segment_t * fs)
+{
+  if (ssvm_type (&fs->ssvm) != SSVM_SEGMENT_PRIVATE)
+    {
+      if (!segment_manager_app_detached (sm))
        {
-         clib_warning ("Segment count too low %u, calculated %u.",
-                       ca->private_segment_count, approx_segment_count);
-         return VNET_API_ERROR_INVALID_VALUE;
+         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);
        }
+    }
 
-      if (svm_fifo_segment_create_process_private (ca))
-       clib_warning ("Failed to create process private segment");
+  fifo_segment_cleanup (fs);
+  ssvm_delete (&fs->ssvm);
 
-      ASSERT (vec_len (ca->new_segment_indices));
-    }
+  if (CLIB_DEBUG)
+    clib_memset (fs, 0xfb, sizeof (*fs));
+  pool_put (sm->segments, fs);
+}
 
-  vec_append (sm->segment_indices, ca->new_segment_indices);
-  vec_free (ca->new_segment_indices);
-  return 0;
+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);
 }
 
-int
-segment_manager_add_segment (segment_manager_t * sm)
+/**
+ * Removes segment after acquiring writer lock
+ */
+static inline void
+sm_lock_and_del_segment_inline (segment_manager_t * sm, u32 fs_index)
 {
-  return segment_manager_add_segment_i (sm, 0, 0);
+  fifo_segment_t *fs;
+  u8 is_prealloc;
+
+  clib_rwlock_writer_lock (&sm->segments_rwlock);
+
+  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))
+    goto done;
+
+  segment_manager_del_segment (sm, fs);
+
+done:
+  clib_rwlock_writer_unlock (&sm->segments_rwlock);
 }
 
-segment_manager_t *
-segment_manager_new ()
+void
+segment_manager_lock_and_del_segment (segment_manager_t * sm, u32 fs_index)
 {
-  segment_manager_t *sm;
-  pool_get (segment_managers, sm);
-  memset (sm, 0, sizeof (*sm));
-  return sm;
+  sm_lock_and_del_segment_inline (sm, fs_index);
 }
 
 /**
- * Initializes segment manager based on options provided.
- * Returns error if svm segment allocation fails.
+ * Reads a segment from the segment manager's pool without lock
  */
-int
-segment_manager_init (segment_manager_t * sm, u32 props_index,
-                     u32 first_seg_size, u32 evt_q_size)
+fifo_segment_t *
+segment_manager_get_segment (segment_manager_t * sm, u32 segment_index)
 {
-  u32 protected_space;
-  int rv;
+  return pool_elt_at_index (sm->segments, segment_index);
+}
 
-  sm->properties_index = props_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);
+}
 
-  protected_space = max_pow2 (sizeof (svm_queue_t)
-                             + evt_q_size * sizeof (session_fifo_event_t));
-  protected_space = round_pow2_u64 (protected_space, CLIB_CACHE_LINE_BYTES);
-  first_seg_size = first_seg_size > 0 ? first_seg_size : default_segment_size;
-  rv = segment_manager_add_segment_i (sm, first_seg_size, protected_space);
-  if (rv)
-    {
-      clib_warning ("Failed to allocate segment");
-      return rv;
-    }
+u64
+segment_manager_make_segment_handle (u32 segment_manager_index,
+                                    u32 segment_index)
+{
+  return (((u64) segment_manager_index << 32) | segment_index);
+}
 
-  clib_spinlock_init (&sm->lockp);
-  return 0;
+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);
 }
 
-u8
-segment_manager_has_fifos (segment_manager_t * sm)
+/**
+ * Reads a segment from the segment manager's pool and acquires reader lock
+ *
+ * Caller must drop the reader's lock by calling
+ * @ref segment_manager_segment_reader_unlock once it finishes working with
+ * the segment.
+ */
+fifo_segment_t *
+segment_manager_get_segment_w_lock (segment_manager_t * sm, u32 segment_index)
 {
-  svm_fifo_segment_private_t *segment;
-  int i;
+  clib_rwlock_reader_lock (&sm->segments_rwlock);
+  return pool_elt_at_index (sm->segments, segment_index);
+}
 
-  for (i = 0; i < vec_len (sm->segment_indices); i++)
-    {
-      segment = svm_fifo_segment_get_segment (sm->segment_indices[i]);
-      if (CLIB_DEBUG && i && !svm_fifo_segment_has_fifos (segment)
-         && !(segment->h->flags & FIFO_SEGMENT_F_IS_PREALLOCATED))
-       clib_warning ("segment %d has no fifos!", sm->segment_indices[i]);
-      if (svm_fifo_segment_has_fifos (segment))
-       return 1;
-    }
-  return 0;
+void
+segment_manager_segment_reader_lock (segment_manager_t * sm)
+{
+  clib_rwlock_reader_lock (&sm->segments_rwlock);
 }
 
-static u8
-segment_manager_app_detached (segment_manager_t * sm)
+void
+segment_manager_segment_reader_unlock (segment_manager_t * sm)
 {
-  return (sm->app_index == SEGMENT_MANAGER_INVALID_APP_INDEX);
+  clib_rwlock_reader_unlock (&sm->segments_rwlock);
 }
 
 void
-segment_manager_app_detach (segment_manager_t * sm)
+segment_manager_segment_writer_unlock (segment_manager_t * sm)
 {
-  sm->app_index = SEGMENT_MANAGER_INVALID_APP_INDEX;
+  clib_rwlock_writer_unlock (&sm->segments_rwlock);
 }
 
-static void
-segment_manager_del_segment (segment_manager_t * sm, u32 segment_index)
-{
-  svm_fifo_segment_private_t *fifo_segment;
-  u32 svm_segment_index;
-  clib_spinlock_lock (&sm->lockp);
-  svm_segment_index = vec_elt (sm->segment_indices, segment_index);
-  fifo_segment = svm_fifo_segment_get_segment (svm_segment_index);
-  if (!fifo_segment
-      || ((fifo_segment->h->flags & FIFO_SEGMENT_F_IS_PREALLOCATED)
-         && !segment_manager_app_detached (sm)))
-    {
-      clib_spinlock_unlock (&sm->lockp);
-      return;
-    }
-  svm_fifo_segment_delete (fifo_segment);
-  vec_del1 (sm->segment_indices, segment_index);
-  clib_spinlock_unlock (&sm->lockp);
+segment_manager_t *
+segment_manager_alloc (void)
+{
+  segment_manager_main_t *smm = &sm_main;
+  segment_manager_t *sm;
+
+  pool_get_zero (smm->segment_managers, sm);
+  clib_rwlock_init (&sm->segments_rwlock);
+  return sm;
+}
+
+int
+segment_manager_init (segment_manager_t * sm)
+{
+  segment_manager_props_t *props;
+
+  props = segment_manager_properties_get (sm);
+
+  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_set_watermarks (sm,
+                                 props->high_watermark,
+                                 props->low_watermark);
+  return 0;
 }
 
 /**
- * Initiate disconnects for all sessions 'owned' by a segment manager
+ * Initializes segment manager based on options provided.
+ * Returns error if ssvm segment(s) allocation fails.
  */
-void
-segment_manager_del_sessions (segment_manager_t * sm)
+int
+segment_manager_init_first (segment_manager_t * sm)
 {
-  int j;
-  svm_fifo_segment_private_t *fifo_segment;
-  svm_fifo_t *fifo;
+  segment_manager_props_t *props;
+  uword first_seg_size;
+  fifo_segment_t *fs;
+  int fs_index, i;
 
-  ASSERT (vec_len (sm->segment_indices));
+  segment_manager_init (sm);
+  props = segment_manager_properties_get (sm);
+  first_seg_size = clib_max (props->segment_size,
+                            sm_main.default_segment_size);
 
-  /* Across all fifo segments used by the server */
-  for (j = 0; j < vec_len (sm->segment_indices); j++)
+  if (props->prealloc_fifos)
     {
-      fifo_segment = svm_fifo_segment_get_segment (sm->segment_indices[j]);
-      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)
-       {
-         u32 session_index, thread_index;
-         stream_session_t *session;
+      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;
 
-         session_index = fifo->master_session_index;
-         thread_index = fifo->master_thread_index;
-         session = session_get (session_index, thread_index);
+      /* 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)));
 
-         /* Instead of directly removing the session call disconnect */
-         if (session->session_state != SESSION_STATE_CLOSED)
-           stream_session_disconnect (session);
-         fifo = fifo->next;
+      rx_fifo_size = sizeof (svm_fifo_t) + rx_rounded_data_size;
+      tx_fifo_size = sizeof (svm_fifo_t) + tx_rounded_data_size;
+      pair_size = rx_fifo_size + tx_fifo_size;
+
+      approx_total_size = (u64) prealloc_fifo_pairs *pair_size;
+      if (first_seg_size > approx_total_size)
+       max_seg_size = first_seg_size;
+      approx_segment_count = (approx_total_size + (max_seg_size - 1))
+       / max_seg_size;
+
+      /* Allocate the segments */
+      for (i = 0; i < approx_segment_count + 1; i++)
+       {
+         fs_index = segment_manager_add_segment (sm, max_seg_size, 0);
+         if (fs_index < 0)
+           {
+             clib_warning ("Failed to preallocate segment %d", i);
+             return fs_index;
+           }
+
+         fs = segment_manager_get_segment (sm, fs_index);
+         if (i == 0)
+           sm->event_queue = segment_manager_alloc_queue (fs, props);
+
+         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;
+    }
 
-      /* Instead of removing the segment, test when cleaning up disconnected
-       * sessions if the segment can be removed.
-       */
+  fs_index = segment_manager_add_segment (sm, first_seg_size, 0);
+  if (fs_index < 0)
+    {
+      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++)
+       {
+         if (fifo_segment_prealloc_fifo_hdrs (fs, i, hdrs_per_slice))
+           return VNET_API_ERROR_SVM_SEGMENT_CREATE_FAIL;
+       }
+    }
+
+  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));
 }
 
 /**
- * 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.
+ * Cleanup segment manager.
  */
 void
-segment_manager_del (segment_manager_t * sm)
+segment_manager_free (segment_manager_t * sm)
 {
-  int i;
+  segment_manager_main_t *smm = &sm_main;
+  fifo_segment_t *fifo_segment;
 
-  ASSERT (!segment_manager_has_fifos (sm)
+  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. */
-  for (i = vec_len (sm->segment_indices) - 1; i >= 0; i--)
+  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 ())
     {
-      if (CLIB_DEBUG)
-       {
-         svm_fifo_segment_private_t *segment;
-         segment = svm_fifo_segment_get_segment (sm->segment_indices[i]);
-         ASSERT (!svm_fifo_segment_has_fifos (segment));
-       }
-      segment_manager_del_segment (sm, i);
+      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);
     }
-  clib_spinlock_free (&sm->lockp);
-  if (CLIB_DEBUG)
-    memset (sm, 0xfe, sizeof (*sm));
-  pool_put (segment_managers, sm);
 }
 
 void
-segment_manager_init_del (segment_manager_t * sm)
+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_del (sm);
+      segment_manager_free (sm);
     }
 }
 
-int
-segment_manager_alloc_session_fifos (segment_manager_t * sm,
-                                    svm_fifo_t ** rx_fifo,
-                                    svm_fifo_t ** tx_fifo,
-                                    u32 * fifo_segment_index)
+segment_manager_t *
+segment_manager_get (u32 index)
 {
-  svm_fifo_segment_private_t *fifo_segment;
-  segment_manager_properties_t *props;
-  u32 fifo_size, sm_index;
-  u8 added_a_segment = 0;
-  int i;
+  return pool_elt_at_index (sm_main.segment_managers, index);
+}
 
-  ASSERT (vec_len (sm->segment_indices));
+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);
+}
 
-  /* Make sure we don't have multiple threads trying to allocate segments
-   * at the same time. */
-  clib_spinlock_lock (&sm->lockp);
+u32
+segment_manager_index (segment_manager_t * sm)
+{
+  return sm - sm_main.segment_managers;
+}
 
-  /* Allocate svm fifos */
-  props = segment_manager_properties_get (sm->properties_index);
-again:
-  for (i = 0; i < vec_len (sm->segment_indices); i++)
-    {
-      *fifo_segment_index = vec_elt (sm->segment_indices, i);
-      fifo_segment = svm_fifo_segment_get_segment (*fifo_segment_index);
+u8
+segment_manager_has_fifos (segment_manager_t * sm)
+{
+  fifo_segment_t *seg;
+  u8 first = 1;
+
+  /* *INDENT-OFF* */
+  segment_manager_foreach_segment_w_lock (seg, sm, ({
+    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 (fifo_segment_has_fifos (seg))
+      {
+       segment_manager_segment_reader_unlock (sm);
+       return 1;
+      }
+  }));
+  /* *INDENT-ON* */
 
-      fifo_size = props->rx_fifo_size;
-      fifo_size = (fifo_size == 0) ? default_fifo_size : fifo_size;
-      *rx_fifo = svm_fifo_segment_alloc_fifo (fifo_segment, fifo_size,
-                                             FIFO_SEGMENT_RX_FREELIST);
+  return 0;
+}
 
-      fifo_size = props->tx_fifo_size;
-      fifo_size = (fifo_size == 0) ? default_fifo_size : fifo_size;
-      *tx_fifo = svm_fifo_segment_alloc_fifo (fifo_segment, fifo_size,
-                                             FIFO_SEGMENT_TX_FREELIST);
+/**
+ * Initiate disconnects for all sessions 'owned' by a segment manager
+ */
+void
+segment_manager_del_sessions (segment_manager_t * sm)
+{
+  session_handle_t *handles = 0, *handle;
+  fifo_segment_t *fs;
+  session_t *session;
+  int slice_index;
+  svm_fifo_t *f;
 
-      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);
-             *tx_fifo = 0;
-           }
-         continue;
-       }
-      if (*tx_fifo == 0)
+  ASSERT (pool_elts (sm->segments) != 0);
+
+  /* Across all fifo segments used by the server */
+  /* *INDENT-OFF* */
+  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);
+
+        /*
+         * 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;
+         }
+      }
+
+    /* Instead of removing the segment, test when cleaning up disconnected
+     * sessions if the segment can be removed.
+     */
+  }));
+  /* *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);
+}
+
+/**
+ * Initiate disconnects for sessions in specified state 'owned' by a segment
+ * manager
+ */
+void
+segment_manager_del_sessions_filter (segment_manager_t *sm,
+                                    session_state_t *states)
+{
+  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 */
+  segment_manager_foreach_segment_w_lock (
+    fs, sm, ({
+      for (slice_index = 0; slice_index < fs->n_slices; slice_index++)
        {
-         if (*rx_fifo != 0)
+         f = fifo_segment_get_slice_fifo_list (fs, slice_index);
+         while (f)
            {
-             svm_fifo_segment_free_fifo (fifo_segment, *rx_fifo,
-                                         FIFO_SEGMENT_RX_FREELIST);
-             *rx_fifo = 0;
+             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;
            }
-         continue;
        }
-      break;
+    }));
+
+  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);
+}
+
+int
+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, 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, sm_main.default_fifo_size);
+  *tx_fifo = fifo_segment_alloc_fifo_w_slice (fifo_segment, thread_index,
+                                             tx_fifo_size,
+                                             FIFO_SEGMENT_TX_FIFO);
 
-  /* See if we're supposed to create another segment */
   if (*rx_fifo == 0)
     {
-      if (props->add_segment && !props->segment_type)
+      /* This would be very odd, but handle it... */
+      if (*tx_fifo != 0)
        {
-         if (added_a_segment)
-           {
-             clib_warning ("added a segment, still can't allocate a fifo");
-             clib_spinlock_unlock (&sm->lockp);
-             return SESSION_ERROR_NEW_SEG_NO_SPACE;
-           }
+         fifo_segment_free_fifo (fifo_segment, *tx_fifo);
+         *tx_fifo = 0;
+       }
+      return -1;
+    }
+  if (*tx_fifo == 0)
+    {
+      if (*rx_fifo != 0)
+       {
+         fifo_segment_free_fifo (fifo_segment, *rx_fifo);
+         *rx_fifo = 0;
+       }
+      return -1;
+    }
 
-         if (segment_manager_add_segment (sm))
-           {
-             clib_spinlock_unlock (&sm->lockp);
-             return VNET_API_ERROR_URI_FIFO_CREATE_FAILED;
-           }
+  return 0;
+}
 
-         added_a_segment = 1;
-         goto again;
+int
+segment_manager_alloc_session_fifos (segment_manager_t * sm,
+                                    u32 thread_index,
+                                    svm_fifo_t ** rx_fifo,
+                                    svm_fifo_t ** tx_fifo)
+{
+  int alloc_fail = 1, rv = 0, new_fs_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);
+
+  /*
+   * Find the first free segment to allocate the fifos in
+   */
+
+  segment_manager_segment_reader_lock (sm);
+
+  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;
        }
-      else
+  }
+
+  if (fs)
+    {
+      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 ((new_fs_index = segment_manager_add_segment (sm, 0, 1)) < 0)
        {
-         clib_warning ("No space to allocate fifos!");
-         clib_spinlock_unlock (&sm->lockp);
-         return SESSION_ERROR_NO_SPACE;
+         clib_warning ("Failed to add new segment");
+         return SESSION_E_SEG_CREATE;
        }
+      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);
+      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
+    {
+      SESSION_DBG ("Can't add new seg and no space to allocate fifos!");
+      return SESSION_E_SEG_NO_SPACE;
     }
 
-  /* Backpointers to segment manager */
+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;
 
-  clib_spinlock_unlock (&sm->lockp);
-
-  if (added_a_segment)
-    return application_add_segment_notify (sm->app_index,
-                                          *fifo_segment_index);
+  /* Drop the lock after app is notified */
+  segment_manager_segment_reader_unlock (sm);
 
-  return 0;
+  return rv;
 }
 
 void
-segment_manager_dealloc_fifos (u32 svm_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)
 {
   segment_manager_t *sm;
-  svm_fifo_segment_private_t *fifo_segment;
-  u32 i, segment_index = ~0;
-  u8 is_first;
+  fifo_segment_t *fs;
+  u32 segment_index;
 
-  sm = segment_manager_get_if_valid (rx_fifo->segment_manager);
+  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)
+  if (!(sm = segment_manager_get_if_valid (rx_fifo->segment_manager)))
     return;
 
-  fifo_segment = svm_fifo_segment_get_segment (svm_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
@@ -495,86 +832,155 @@ segment_manager_dealloc_fifos (u32 svm_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))
     {
-      is_first = sm->segment_indices[0] == svm_segment_index;
+      segment_manager_segment_reader_unlock (sm);
 
       /* Remove segment if it holds no fifos or first but not protected */
-      if (!is_first || !sm->first_is_protected)
-       {
-         /* Find the segment manager segment index */
-         for (i = 0; i < vec_len (sm->segment_indices); i++)
-           if (sm->segment_indices[i] == svm_segment_index)
-             {
-               segment_index = i;
-               break;
-             }
-         ASSERT (segment_index != (u32) ~ 0);
-         segment_manager_del_segment (sm, segment_index);
-       }
+      if (segment_index != 0 || !sm->first_is_protected)
+       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);
 }
 
-/**
- * Allocates shm queue in the first segment
- */
-svm_queue_t *
-segment_manager_alloc_queue (segment_manager_t * sm, u32 queue_size)
+void
+segment_manager_detach_fifo (segment_manager_t *sm, svm_fifo_t **f)
 {
-  ssvm_shared_header_t *sh;
-  svm_fifo_segment_private_t *segment;
-  svm_queue_t *q;
-  void *oldheap;
+  fifo_segment_t *fs;
 
-  ASSERT (sm->segment_indices != 0);
+  fs = segment_manager_get_segment_w_lock (sm, (*f)->segment_index);
+  fifo_segment_detach_fifo (fs, f);
+  segment_manager_segment_reader_unlock (sm);
+}
 
-  segment = svm_fifo_segment_get_segment (sm->segment_indices[0]);
-  sh = segment->ssvm.sh;
+void
+segment_manager_attach_fifo (segment_manager_t *sm, svm_fifo_t **f,
+                            session_t *s)
+{
+  fifo_segment_t *fs;
 
-  oldheap = ssvm_push_heap (sh);
-  q = svm_queue_init (queue_size,
-                     sizeof (session_fifo_event_t), 0 /* consumer pid */ ,
-                     0 /* signal when queue non-empty */ );
-  ssvm_pop_heap (oldheap);
+  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)
+{
+  u32 fifo_evt_size, notif_q_size, q_hdrs;
+  u32 msg_q_sz, fifo_evt_ring_sz, session_ntf_ring_sz;
+
+  fifo_evt_size = 1 << max_log2 (sizeof (session_event_t));
+  notif_q_size = clib_max (16, q_len >> 4);
+
+  msg_q_sz = q_len * sizeof (svm_msg_q_msg_t);
+  fifo_evt_ring_sz = q_len * fifo_evt_size;
+  session_ntf_ring_sz = notif_q_size * 256;
+  q_hdrs = sizeof (svm_queue_t) + sizeof (svm_msg_q_t);
+
+  return (msg_q_sz + fifo_evt_ring_sz + session_ntf_ring_sz + q_hdrs);
+}
+
+/**
+ * Allocates shm queue in the first segment
+ *
+ * Must be called with lock held
+ */
+svm_msg_q_t *
+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;
+
+  fifo_evt_size = sizeof (session_event_t);
+  notif_q_size = clib_max (16, props->evt_q_size >> 4);
+  /* *INDENT-OFF* */
+  svm_msg_q_ring_cfg_t rc[SESSION_MQ_N_RINGS] = {
+    {props->evt_q_size, fifo_evt_size, 0},
+    {notif_q_size, session_evt_size, 0}
+  };
+  /* *INDENT-ON* */
+  cfg->consumer_pid = 0;
+  cfg->n_rings = 2;
+  cfg->q_nitems = props->evt_q_size;
+  cfg->ring_cfgs = rc;
+
+  q = fifo_segment_msg_q_alloc (segment, 0, cfg);
+
+  if (props->use_mq_eventfd)
+    {
+      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)
 {
+  fifo_segment_t *segment;
   ssvm_shared_header_t *sh;
-  svm_fifo_segment_private_t *segment;
   void *oldheap;
 
-  ASSERT (sm->segment_indices != 0);
+  ASSERT (!pool_is_free_index (sm->segments, 0));
 
-  segment = svm_fifo_segment_get_segment (sm->segment_indices[0]);
+  segment = segment_manager_get_segment_w_lock (sm, 0);
   sh = segment->ssvm.sh;
 
   oldheap = ssvm_push_heap (sh);
   svm_queue_free (q);
   ssvm_pop_heap (oldheap);
+  segment_manager_segment_reader_unlock (sm);
+}
+
+/*
+ * Init segment vm address allocator
+ */
+void
+segment_manager_main_init (void)
+{
+  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)
 {
-  svm_fifo_segment_private_t *segments, *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)
     {
@@ -587,40 +993,41 @@ segment_manager_show_fn (vlib_main_t * vm, unformat_input_t * input,
                                  format_unformat_error, input);
     }
   vlib_cli_output (vm, "%d segment managers allocated",
-                  pool_elts (segment_managers));
-  if (verbose && pool_elts (segment_managers))
+                  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, segment_managers, ({
-       vlib_cli_output (vm, "%-10d%=15d%=12d", segment_manager_index(sm),
-                          sm->app_index, vec_len (sm->segment_indices));
-      }));
+      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)
     {
-      segments = svm_fifo_segment_segments_pool ();
-      vlib_cli_output (vm, "%d svm fifo segments allocated",
-                      pool_elts (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 (seg, segments, ({
-       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);
-      }));
+      pool_foreach (sm, smm->segment_managers)  {
+         segment_manager_foreach_segment_w_lock (seg, sm, ({
+           vlib_cli_output (vm, "%U", format_fifo_segment, seg, verbose);
+         }));
+      }
       /* *INDENT-ON* */
 
     }
@@ -636,6 +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
  *