session: use vpp to switch io events for ct sessions

Instead of allocating pairs of message queues per cut-thru session and
having the applications map them, this uses vpp as an io event message
switch.

Change-Id: I51db1c7564df479a7d1a3288342394251fd188bb
Signed-off-by: Florin Coras <fcoras@cisco.com>

4 files changed, 82 insertions, 382 deletions

diff --git a/src/vcl/vcl_bapi.c b/src/vcl/vcl_bapi.c
index 6baa7c1f927..d86e7738bdd 100644
--- a/src/vcl/vcl_bapi.c
+++ b/src/vcl/vcl_bapi.c
@@ -294,41 +294,6 @@ vl_api_unmap_segment_t_handler (vl_api_unmap_segment_t * mp)
 }
 
 static void
-  vl_api_app_cut_through_registration_add_t_handler
-  (vl_api_app_cut_through_registration_add_t * mp)
-{
-  vcl_cut_through_registration_t *ctr;
-  u32 mqc_index = ~0;
-  vcl_worker_t *wrk;
-  int *fds = 0;
-
-  if (mp->n_fds)
-    {
-      ASSERT (mp->n_fds == 2);
-      vec_validate (fds, mp->n_fds);
-      vl_socket_client_recv_fd_msg (fds, mp->n_fds, 5);
-    }
-
-  wrk = vcl_worker_get (mp->wrk_index);
-  ctr = vcl_ct_registration_lock_and_alloc (wrk);
-  ctr->mq = uword_to_pointer (mp->evt_q_address, svm_msg_q_t *);
-  ctr->peer_mq = uword_to_pointer (mp->peer_evt_q_address, svm_msg_q_t *);
-  VDBG (0, "Adding ct registration %u", vcl_ct_registration_index (wrk, ctr));
-
-  if (mp->n_fds && (mp->fd_flags & SESSION_FD_F_MQ_EVENTFD))
-    {
-      svm_msg_q_set_consumer_eventfd (ctr->mq, fds[0]);
-      svm_msg_q_set_producer_eventfd (ctr->peer_mq, fds[1]);
-      mqc_index = vcl_mq_epoll_add_evfd (wrk, ctr->mq);
-      ctr->epoll_evt_conn_index = mqc_index;
-      vec_free (fds);
-    }
-  vcl_ct_registration_lookup_add (wrk, mp->evt_q_address,
-				  vcl_ct_registration_index (wrk, ctr));
-  vcl_ct_registration_unlock (wrk);
-}
-
-static void
 vl_api_bind_sock_reply_t_handler (vl_api_bind_sock_reply_t * mp)
 {
   /* Expecting a similar message on mq. So ignore this */
@@ -400,7 +365,6 @@ _(APPLICATION_TLS_CERT_ADD_REPLY, application_tls_cert_add_reply)  	\
 _(APPLICATION_TLS_KEY_ADD_REPLY, application_tls_key_add_reply)  	\
 _(MAP_ANOTHER_SEGMENT, map_another_segment)                     	\
 _(UNMAP_SEGMENT, unmap_segment)						\
-_(APP_CUT_THROUGH_REGISTRATION_ADD, app_cut_through_registration_add)	\
 _(APP_WORKER_ADD_DEL_REPLY, app_worker_add_del_reply)			\
 
 void
diff --git a/src/vcl/vcl_private.c b/src/vcl/vcl_private.c
index 6c364e376f7..e38b663507c 100644
--- a/src/vcl/vcl_private.c
+++ b/src/vcl/vcl_private.c
@@ -68,75 +68,6 @@ vcl_wait_for_app_state_change (app_state_t app_state)
   return VPPCOM_ETIMEDOUT;
 }
 
-vcl_cut_through_registration_t *
-vcl_ct_registration_lock_and_alloc (vcl_worker_t * wrk)
-{
-  vcl_cut_through_registration_t *cr;
-  clib_spinlock_lock (&wrk->ct_registration_lock);
-  pool_get (wrk->cut_through_registrations, cr);
-  memset (cr, 0, sizeof (*cr));
-  cr->epoll_evt_conn_index = -1;
-  return cr;
-}
-
-u32
-vcl_ct_registration_index (vcl_worker_t * wrk,
-			   vcl_cut_through_registration_t * ctr)
-{
-  return (ctr - wrk->cut_through_registrations);
-}
-
-void
-vcl_ct_registration_lock (vcl_worker_t * wrk)
-{
-  clib_spinlock_lock (&wrk->ct_registration_lock);
-}
-
-void
-vcl_ct_registration_unlock (vcl_worker_t * wrk)
-{
-  clib_spinlock_unlock (&wrk->ct_registration_lock);
-}
-
-vcl_cut_through_registration_t *
-vcl_ct_registration_get (vcl_worker_t * wrk, u32 ctr_index)
-{
-  if (pool_is_free_index (wrk->cut_through_registrations, ctr_index))
-    return 0;
-  return pool_elt_at_index (wrk->cut_through_registrations, ctr_index);
-}
-
-vcl_cut_through_registration_t *
-vcl_ct_registration_lock_and_lookup (vcl_worker_t * wrk, uword mq_addr)
-{
-  uword *p;
-  clib_spinlock_lock (&wrk->ct_registration_lock);
-  p = hash_get (wrk->ct_registration_by_mq, mq_addr);
-  if (!p)
-    return 0;
-  return vcl_ct_registration_get (wrk, p[0]);
-}
-
-void
-vcl_ct_registration_lookup_add (vcl_worker_t * wrk, uword mq_addr,
-				u32 ctr_index)
-{
-  hash_set (wrk->ct_registration_by_mq, mq_addr, ctr_index);
-}
-
-void
-vcl_ct_registration_lookup_del (vcl_worker_t * wrk, uword mq_addr)
-{
-  hash_unset (wrk->ct_registration_by_mq, mq_addr);
-}
-
-void
-vcl_ct_registration_del (vcl_worker_t * wrk,
-			 vcl_cut_through_registration_t * ctr)
-{
-  pool_put (wrk->cut_through_registrations, ctr);
-}
-
 vcl_mq_evt_conn_t *
 vcl_mq_evt_conn_alloc (vcl_worker_t * wrk)
 {
@@ -235,8 +166,6 @@ vcl_worker_cleanup (vcl_worker_t * wrk, u8 notify_vpp)
   if (wrk->mqs_epfd > 0)
     close (wrk->mqs_epfd);
   hash_free (wrk->session_index_by_vpp_handles);
-  hash_free (wrk->ct_registration_by_mq);
-  clib_spinlock_free (&wrk->ct_registration_lock);
   vec_free (wrk->mq_events);
   vec_free (wrk->mq_msg_vector);
   vcl_worker_free (wrk);
@@ -286,8 +215,6 @@ vcl_worker_alloc_and_init ()
     }
 
   wrk->session_index_by_vpp_handles = hash_create (0, sizeof (uword));
-  wrk->ct_registration_by_mq = hash_create (0, sizeof (uword));
-  clib_spinlock_init (&wrk->ct_registration_lock);
   clib_time_init (&wrk->clib_time);
   vec_validate (wrk->mq_events, 64);
   vec_validate (wrk->mq_msg_vector, 128);
@@ -418,6 +345,9 @@ vcl_session_read_ready (vcl_session_t * session)
   if (session->session_state & STATE_LISTEN)
     return clib_fifo_elts (session->accept_evts_fifo);
 
+  if (vcl_session_is_ct (session))
+    return svm_fifo_max_dequeue (session->ct_rx_fifo);
+
   return svm_fifo_max_dequeue (session->rx_fifo);
 }
 
@@ -452,6 +382,9 @@ vcl_session_write_ready (vcl_session_t * session)
       return rv;
     }
 
+  if (vcl_session_is_ct (session))
+    return svm_fifo_max_enqueue (session->ct_tx_fifo);
+
   return svm_fifo_max_enqueue (session->tx_fifo);
 }
 
diff --git a/src/vcl/vcl_private.h b/src/vcl/vcl_private.h
index 2187499282f..dfe8b160edc 100644
--- a/src/vcl/vcl_private.h
+++ b/src/vcl/vcl_private.h
@@ -162,6 +162,9 @@ typedef struct
   u64 vpp_handle;
   u32 vpp_thread_index;
 
+  svm_fifo_t *ct_rx_fifo;
+  svm_fifo_t *ct_tx_fifo;
+
   /* Socket configuration state */
   u8 is_vep;
   u8 is_vep_session;
@@ -270,15 +273,6 @@ typedef struct vcl_worker_
   /** For deadman timers */
   clib_time_t clib_time;
 
-  /** Pool of cut through registrations */
-  vcl_cut_through_registration_t *cut_through_registrations;
-
-  /** Lock for accessing ct registration pool */
-  clib_spinlock_t ct_registration_lock;
-
-  /** Cut-through registration by mq address hash table */
-  uword *ct_registration_by_mq;
-
   /** Vector acting as buffer for mq messages */
   svm_msg_q_msg_t *mq_msg_vector;
 
@@ -481,7 +475,7 @@ const char *vppcom_session_state_str (vcl_session_state_t state);
 static inline u8
 vcl_session_is_ct (vcl_session_t * s)
 {
-  return (s->our_evt_q != 0);
+  return (s->ct_tx_fifo != 0);
 }
 
 static inline u8
@@ -516,19 +510,6 @@ vcl_session_closed_error (vcl_session_t * s)
  * Helpers
  */
 int vcl_wait_for_app_state_change (app_state_t app_state);
-vcl_cut_through_registration_t
-  * vcl_ct_registration_lock_and_alloc (vcl_worker_t * wrk);
-void vcl_ct_registration_del (vcl_worker_t * wrk,
-			      vcl_cut_through_registration_t * ctr);
-u32 vcl_ct_registration_index (vcl_worker_t * wrk,
-			       vcl_cut_through_registration_t * ctr);
-void vcl_ct_registration_lock (vcl_worker_t * wrk);
-void vcl_ct_registration_unlock (vcl_worker_t * wrk);
-vcl_cut_through_registration_t
-  * vcl_ct_registration_lock_and_lookup (vcl_worker_t * wrk, uword mq_addr);
-void vcl_ct_registration_lookup_add (vcl_worker_t * wrk, uword mq_addr,
-				     u32 ctr_index);
-void vcl_ct_registration_lookup_del (vcl_worker_t * wrk, uword mq_addr);
 vcl_mq_evt_conn_t *vcl_mq_evt_conn_alloc (vcl_worker_t * wrk);
 u32 vcl_mq_evt_conn_index (vcl_worker_t * wrk, vcl_mq_evt_conn_t * mqc);
 vcl_mq_evt_conn_t *vcl_mq_evt_conn_get (vcl_worker_t * wrk, u32 mq_conn_idx);
@@ -581,10 +562,7 @@ vcl_n_workers (void)
 static inline svm_msg_q_t *
 vcl_session_vpp_evt_q (vcl_worker_t * wrk, vcl_session_t * s)
 {
-  if (vcl_session_is_ct (s))
-    return wrk->vpp_event_queues[0];
-  else
-    return wrk->vpp_event_queues[s->vpp_thread_index];
+  return wrk->vpp_event_queues[s->vpp_thread_index];
 }
 
 void vcl_send_session_worker_update (vcl_worker_t * wrk, vcl_session_t * s,
diff --git a/src/vcl/vppcom.c b/src/vcl/vppcom.c
index 7c076d3b315..3abde98288a 100644
--- a/src/vcl/vppcom.c
+++ b/src/vcl/vppcom.c
@@ -273,7 +273,6 @@ vcl_session_accepted_handler (vcl_worker_t * wrk, session_accepted_msg_t * mp)
 						      mp->listener_handle);
   if (!listen_session)
     {
-      svm_msg_q_t *evt_q;
       evt_q = uword_to_pointer (mp->vpp_event_queue_address, svm_msg_q_t *);
       clib_warning ("VCL<%d>: ERROR: couldn't find listen session: "
 		    "unknown vpp listener handle %llx",
@@ -287,39 +286,23 @@ vcl_session_accepted_handler (vcl_worker_t * wrk, session_accepted_msg_t * mp)
   rx_fifo = uword_to_pointer (mp->server_rx_fifo, svm_fifo_t *);
   tx_fifo = uword_to_pointer (mp->server_tx_fifo, svm_fifo_t *);
 
-  if (mp->server_event_queue_address)
-    {
-      session->vpp_evt_q = uword_to_pointer (mp->client_event_queue_address,
-					     svm_msg_q_t *);
-      session->our_evt_q = uword_to_pointer (mp->server_event_queue_address,
-					     svm_msg_q_t *);
-      if (vcl_wait_for_segment (mp->segment_handle))
-	{
-	  clib_warning ("segment for session %u couldn't be mounted!",
-			session->session_index);
-	  return VCL_INVALID_SESSION_INDEX;
-	}
-      rx_fifo->master_session_index = session->session_index;
-      tx_fifo->master_session_index = session->session_index;
-      rx_fifo->master_thread_index = vcl_get_worker_index ();
-      tx_fifo->master_thread_index = vcl_get_worker_index ();
-      vec_validate (wrk->vpp_event_queues, 0);
-      evt_q = uword_to_pointer (mp->vpp_event_queue_address, svm_msg_q_t *);
-      wrk->vpp_event_queues[0] = evt_q;
-    }
-  else
+  if (vcl_wait_for_segment (mp->segment_handle))
     {
-      session->vpp_evt_q = uword_to_pointer (mp->vpp_event_queue_address,
-					     svm_msg_q_t *);
-      rx_fifo->client_session_index = session->session_index;
-      tx_fifo->client_session_index = session->session_index;
-      rx_fifo->client_thread_index = vcl_get_worker_index ();
-      tx_fifo->client_thread_index = vcl_get_worker_index ();
-      vpp_wrk_index = tx_fifo->master_thread_index;
-      vec_validate (wrk->vpp_event_queues, vpp_wrk_index);
-      wrk->vpp_event_queues[vpp_wrk_index] = session->vpp_evt_q;
+      clib_warning ("segment for session %u couldn't be mounted!",
+		    session->session_index);
+      return VCL_INVALID_SESSION_INDEX;
     }
 
+  session->vpp_evt_q = uword_to_pointer (mp->vpp_event_queue_address,
+					 svm_msg_q_t *);
+  rx_fifo->client_session_index = session->session_index;
+  tx_fifo->client_session_index = session->session_index;
+  rx_fifo->client_thread_index = vcl_get_worker_index ();
+  tx_fifo->client_thread_index = vcl_get_worker_index ();
+  vpp_wrk_index = tx_fifo->master_thread_index;
+  vec_validate (wrk->vpp_event_queues, vpp_wrk_index);
+  wrk->vpp_event_queues[vpp_wrk_index] = session->vpp_evt_q;
+
   session->vpp_handle = mp->handle;
   session->vpp_thread_index = rx_fifo->master_thread_index;
   session->client_context = mp->context;
@@ -356,7 +339,6 @@ vcl_session_connected_handler (vcl_worker_t * wrk,
   u32 session_index, vpp_wrk_index;
   svm_fifo_t *rx_fifo, *tx_fifo;
   vcl_session_t *session = 0;
-  svm_msg_q_t *evt_q;
 
   session_index = mp->context;
   session = vcl_session_get (wrk, session_index);
@@ -380,8 +362,8 @@ vcl_session_connected_handler (vcl_worker_t * wrk,
   tx_fifo = uword_to_pointer (mp->server_tx_fifo, svm_fifo_t *);
   if (vcl_wait_for_segment (mp->segment_handle))
     {
-      clib_warning ("segment for session %u couldn't be mounted!",
-		    session->session_index);
+      VDBG (0, "segment for session %u couldn't be mounted!",
+	    session->session_index);
       return VCL_INVALID_SESSION_INDEX;
     }
 
@@ -390,24 +372,22 @@ vcl_session_connected_handler (vcl_worker_t * wrk,
   rx_fifo->client_thread_index = vcl_get_worker_index ();
   tx_fifo->client_thread_index = vcl_get_worker_index ();
 
-  if (mp->client_event_queue_address)
-    {
-      session->vpp_evt_q = uword_to_pointer (mp->server_event_queue_address,
-					     svm_msg_q_t *);
-      session->our_evt_q = uword_to_pointer (mp->client_event_queue_address,
-					     svm_msg_q_t *);
+  session->vpp_evt_q = uword_to_pointer (mp->vpp_event_queue_address,
+					 svm_msg_q_t *);
+  vpp_wrk_index = tx_fifo->master_thread_index;
+  vec_validate (wrk->vpp_event_queues, vpp_wrk_index);
+  wrk->vpp_event_queues[vpp_wrk_index] = session->vpp_evt_q;
 
-      vec_validate (wrk->vpp_event_queues, 0);
-      evt_q = uword_to_pointer (mp->vpp_event_queue_address, svm_msg_q_t *);
-      wrk->vpp_event_queues[0] = evt_q;
-    }
-  else
+  if (mp->ct_rx_fifo)
     {
-      session->vpp_evt_q = uword_to_pointer (mp->vpp_event_queue_address,
-					     svm_msg_q_t *);
-      vpp_wrk_index = tx_fifo->master_thread_index;
-      vec_validate (wrk->vpp_event_queues, vpp_wrk_index);
-      wrk->vpp_event_queues[vpp_wrk_index] = session->vpp_evt_q;
+      session->ct_rx_fifo = uword_to_pointer (mp->ct_rx_fifo, svm_fifo_t *);
+      session->ct_tx_fifo = uword_to_pointer (mp->ct_tx_fifo, svm_fifo_t *);
+      if (vcl_wait_for_segment (mp->ct_segment_handle))
+	{
+	  VDBG (0, "ct segment for session %u couldn't be mounted!",
+		session->session_index);
+	  return VCL_INVALID_SESSION_INDEX;
+	}
     }
 
   session->rx_fifo = rx_fifo;
@@ -667,10 +647,11 @@ vcl_handle_mq_event (vcl_worker_t * wrk, session_event_t * e)
 
   switch (e->event_type)
     {
-    case FIFO_EVENT_APP_RX:
-    case FIFO_EVENT_APP_TX:
-    case SESSION_IO_EVT_CT_RX:
-    case SESSION_IO_EVT_CT_TX:
+    case SESSION_IO_EVT_RX:
+    case SESSION_IO_EVT_TX:
+      session = vcl_session_get (wrk, e->fifo->client_session_index);
+      if (!session || !(session->session_state & STATE_OPEN))
+	break;
       vec_add1 (wrk->unhandled_evts_vector, *e);
       break;
     case SESSION_CTRL_EVT_ACCEPTED:
@@ -1123,23 +1104,6 @@ vcl_session_cleanup (vcl_worker_t * wrk, vcl_session_t * session,
 	}
     }
 
-  if (vcl_session_is_ct (session))
-    {
-      vcl_cut_through_registration_t *ctr;
-      uword mq_addr;
-
-      mq_addr = pointer_to_uword (session->our_evt_q);
-      ctr = vcl_ct_registration_lock_and_lookup (wrk, mq_addr);
-      ASSERT (ctr);
-      if (ctr->epoll_evt_conn_index != ~0)
-	vcl_mq_epoll_del_evfd (wrk, ctr->epoll_evt_conn_index);
-      VDBG (0, "Removing ct registration %u",
-	    vcl_ct_registration_index (wrk, ctr));
-      vcl_ct_registration_del (wrk, ctr);
-      vcl_ct_registration_lookup_del (wrk, mq_addr);
-      vcl_ct_registration_unlock (wrk);
-    }
-
   VDBG (0, "session %u [0x%llx] removed", session->session_index, vpp_handle);
 
 cleanup:
@@ -1336,7 +1300,6 @@ vppcom_session_accept (uint32_t listen_session_handle, vppcom_endpt_t * ep,
   session_accepted_msg_t accepted_msg;
   vcl_session_t *listen_session = 0;
   vcl_session_t *client_session = 0;
-  svm_msg_q_t *vpp_evt_q;
   vcl_session_msg_t *evt;
   u64 listen_vpp_handle;
   svm_msg_q_msg_t msg;
@@ -1411,13 +1374,8 @@ handle:
 			  sizeof (ip6_address_t));
     }
 
-  if (accepted_msg.server_event_queue_address)
-    vpp_evt_q = uword_to_pointer (accepted_msg.vpp_event_queue_address,
-				  svm_msg_q_t *);
-  else
-    vpp_evt_q = client_session->vpp_evt_q;
-
-  vcl_send_session_accepted_reply (vpp_evt_q, client_session->client_context,
+  vcl_send_session_accepted_reply (client_session->vpp_evt_q,
+				   client_session->client_context,
 				   client_session->vpp_handle, 0);
 
   VDBG (0, "listener %u [0x%llx] accepted %u [0x%llx] peer: %U:%u "
@@ -1533,11 +1491,8 @@ vppcom_session_connect (uint32_t session_handle, vppcom_endpt_t * server_ep)
 static u8
 vcl_is_rx_evt_for_session (session_event_t * e, u32 sid, u8 is_ct)
 {
-  if (!is_ct)
-    return (e->event_type == FIFO_EVENT_APP_RX
-	    && e->fifo->client_session_index == sid);
-  else
-    return (e->event_type == SESSION_IO_EVT_CT_TX);
+  return (e->event_type == SESSION_IO_EVT_RX
+	  && e->fifo->client_session_index == sid);
 }
 
 static inline int
@@ -1570,17 +1525,18 @@ vppcom_session_read_internal (uint32_t session_handle, void *buf, int n,
 
   is_nonblocking = VCL_SESS_ATTR_TEST (s->attr, VCL_SESS_ATTR_NONBLOCK);
   is_ct = vcl_session_is_ct (s);
-  mq = is_ct ? s->our_evt_q : wrk->app_event_queue;
-  rx_fifo = s->rx_fifo;
+  mq = wrk->app_event_queue;
+  rx_fifo = is_ct ? s->ct_rx_fifo : s->rx_fifo;
   s->has_rx_evt = 0;
 
+  if (is_ct)
+    svm_fifo_unset_event (s->rx_fifo);
+
   if (svm_fifo_is_empty (rx_fifo))
     {
+      svm_fifo_unset_event (rx_fifo);
       if (is_nonblocking)
-	{
-	  svm_fifo_unset_event (rx_fifo);
-	  return VPPCOM_EWOULDBLOCK;
-	}
+	return VPPCOM_EWOULDBLOCK;
       while (svm_fifo_is_empty (rx_fifo))
 	{
 	  if (vcl_session_is_closing (s))
@@ -1595,7 +1551,10 @@ vppcom_session_read_internal (uint32_t session_handle, void *buf, int n,
 	  e = svm_msg_q_msg_data (mq, &msg);
 	  svm_msg_q_unlock (mq);
 	  if (!vcl_is_rx_evt_for_session (e, s->session_index, is_ct))
-	    vcl_handle_mq_event (wrk, e);
+	    {
+	      clib_warning ("THIS ONE type %u", e->event_type);
+	      vcl_handle_mq_event (wrk, e);
+	    }
 	  svm_msg_q_free_msg (mq, &msg);
 	}
     }
@@ -1608,13 +1567,6 @@ vppcom_session_read_internal (uint32_t session_handle, void *buf, int n,
   if (svm_fifo_is_empty (rx_fifo))
     svm_fifo_unset_event (rx_fifo);
 
-  if (is_ct && svm_fifo_needs_tx_ntf (rx_fifo, n_read))
-    {
-      svm_fifo_clear_tx_ntf (s->rx_fifo);
-      app_send_io_evt_to_vpp (s->vpp_evt_q, s->rx_fifo, SESSION_IO_EVT_CT_RX,
-			      SVM_Q_WAIT);
-    }
-
   VDBG (2, "vpp handle 0x%llx, sid %u: read %d bytes from (%p)",
 	s->vpp_handle, session_handle, n_read, rx_fifo);
 
@@ -1659,6 +1611,9 @@ vppcom_session_read_segments (uint32_t session_handle,
   rx_fifo = s->rx_fifo;
   s->has_rx_evt = 0;
 
+  if (is_ct)
+    svm_fifo_unset_event (s->rx_fifo);
+
   if (svm_fifo_is_empty (rx_fifo))
     {
       if (is_nonblocking)
@@ -1688,14 +1643,6 @@ vppcom_session_read_segments (uint32_t session_handle,
   n_read = svm_fifo_segments (rx_fifo, (svm_fifo_segment_t *) ds);
   svm_fifo_unset_event (rx_fifo);
 
-  if (is_ct && n_read + svm_fifo_max_dequeue (rx_fifo) == rx_fifo->nitems)
-    {
-      /* If the peer is not polling send notification */
-      if (!svm_fifo_has_event (s->rx_fifo))
-	app_send_io_evt_to_vpp (s->vpp_evt_q, s->rx_fifo,
-				SESSION_IO_EVT_CT_RX, SVM_Q_WAIT);
-    }
-
   return n_read;
 }
 
@@ -1729,11 +1676,8 @@ vppcom_data_segment_copy (void *buf, vppcom_data_segments_t ds, u32 max_bytes)
 static u8
 vcl_is_tx_evt_for_session (session_event_t * e, u32 sid, u8 is_ct)
 {
-  if (!is_ct)
-    return (e->event_type == FIFO_EVENT_APP_TX
-	    && e->fifo->client_session_index == sid);
-  else
-    return (e->event_type == SESSION_IO_EVT_CT_RX);
+  return (e->event_type == SESSION_IO_EVT_TX
+	  && e->fifo->client_session_index == sid);
 }
 
 static inline int
@@ -1772,10 +1716,10 @@ vppcom_session_write_inline (uint32_t session_handle, void *buf, size_t n,
       return vcl_session_closed_error (s);;
     }
 
-  tx_fifo = s->tx_fifo;
   is_ct = vcl_session_is_ct (s);
+  tx_fifo = is_ct ? s->ct_tx_fifo : s->tx_fifo;
   is_nonblocking = VCL_SESS_ATTR_TEST (s->attr, VCL_SESS_ATTR_NONBLOCK);
-  mq = is_ct ? s->our_evt_q : wrk->app_event_queue;
+  mq = wrk->app_event_queue;
   if (svm_fifo_is_full (tx_fifo))
     {
       if (is_nonblocking)
@@ -1801,17 +1745,20 @@ vppcom_session_write_inline (uint32_t session_handle, void *buf, size_t n,
 	}
     }
 
-  ASSERT (FIFO_EVENT_APP_TX + 1 == SESSION_IO_EVT_CT_TX);
-  et = FIFO_EVENT_APP_TX + vcl_session_is_ct (s);
-  if (is_flush && !vcl_session_is_ct (s))
+  et = SESSION_IO_EVT_TX;
+  if (is_flush && !is_ct)
     et = SESSION_IO_EVT_TX_FLUSH;
 
   if (s->is_dgram)
     n_write = app_send_dgram_raw (tx_fifo, &s->transport,
-				  s->vpp_evt_q, buf, n, et, SVM_Q_WAIT);
+				  s->vpp_evt_q, buf, n, et,
+				  !is_ct /* do_evt */ , SVM_Q_WAIT);
   else
     n_write = app_send_stream_raw (tx_fifo, s->vpp_evt_q, buf, n, et,
-				   SVM_Q_WAIT);
+				   !is_ct /* do_evt */ , SVM_Q_WAIT);
+
+  if (is_ct && svm_fifo_set_event (s->tx_fifo))
+    app_send_io_evt_to_vpp (s->vpp_evt_q, s->tx_fifo, et, SVM_Q_WAIT);
 
   ASSERT (n_write > 0);
 
@@ -1835,32 +1782,6 @@ vppcom_session_write_msg (uint32_t session_handle, void *buf, size_t n)
 				      1 /* is_flush */ );
 }
 
-
-static vcl_session_t *
-vcl_ct_session_get_from_fifo (vcl_worker_t * wrk, svm_fifo_t * f, u8 type)
-{
-  vcl_session_t *s;
-  s = vcl_session_get (wrk, f->client_session_index);
-  if (s)
-    {
-      /* rx fifo */
-      if (type == 0 && s->rx_fifo == f)
-	return s;
-      /* tx fifo */
-      if (type == 1 && s->tx_fifo == f)
-	return s;
-    }
-  s = vcl_session_get (wrk, f->master_session_index);
-  if (s)
-    {
-      if (type == 0 && s->rx_fifo == f)
-	return s;
-      if (type == 1 && s->tx_fifo == f)
-	return s;
-    }
-  return 0;
-}
-
 #define vcl_fifo_rx_evt_valid_or_break(_fifo)			\
 if (PREDICT_FALSE (svm_fifo_is_empty (_fifo)))			\
   {								\
@@ -1905,29 +1826,6 @@ vcl_select_handle_mq_event (vcl_worker_t * wrk, session_event_t * e,
 	  *bits_set += 1;
 	}
       break;
-    case SESSION_IO_EVT_CT_TX:
-      vcl_fifo_rx_evt_valid_or_break (e->fifo);
-      session = vcl_ct_session_get_from_fifo (wrk, e->fifo, 0);
-      if (!session)
-	break;
-      sid = session->session_index;
-      if (sid < n_bits && read_map)
-	{
-	  clib_bitmap_set_no_check ((uword *) read_map, sid, 1);
-	  *bits_set += 1;
-	}
-      break;
-    case SESSION_IO_EVT_CT_RX:
-      session = vcl_ct_session_get_from_fifo (wrk, e->fifo, 1);
-      if (!session)
-	break;
-      sid = session->session_index;
-      if (sid < n_bits && write_map)
-	{
-	  clib_bitmap_set_no_check ((uword *) write_map, sid, 1);
-	  *bits_set += 1;
-	}
-      break;
     case SESSION_CTRL_EVT_ACCEPTED:
       session = vcl_session_accepted (wrk,
 				      (session_accepted_msg_t *) e->data);
@@ -2038,31 +1936,9 @@ vppcom_select_condvar (vcl_worker_t * wrk, int n_bits,
 		       vcl_si_set * except_map, double time_to_wait,
 		       u32 * bits_set)
 {
-  double total_wait = 0, wait_slice;
-  vcl_cut_through_registration_t *cr;
-
   time_to_wait = (time_to_wait == -1) ? 1e6 : time_to_wait;
-  wait_slice = wrk->cut_through_registrations ? 10e-6 : time_to_wait;
-  do
-    {
-      vcl_ct_registration_lock (wrk);
-      /* *INDENT-OFF* */
-      pool_foreach (cr, wrk->cut_through_registrations, ({
-	vcl_select_handle_mq (wrk, cr->mq, n_bits, read_map, write_map, except_map,
-	                      0, bits_set);
-      }));
-      /* *INDENT-ON* */
-      vcl_ct_registration_unlock (wrk);
-
-      vcl_select_handle_mq (wrk, wrk->app_event_queue, n_bits, read_map,
-			    write_map, except_map, wait_slice, bits_set);
-      total_wait += wait_slice;
-      if (*bits_set)
-	return *bits_set;
-    }
-  while (total_wait < time_to_wait);
-
-  return 0;
+  return vcl_select_handle_mq (wrk, wrk->app_event_queue, n_bits, read_map,
+			       write_map, except_map, time_to_wait, bits_set);
 }
 
 static int
@@ -2477,7 +2353,7 @@ vcl_epoll_wait_handle_mq_event (vcl_worker_t * wrk, session_event_t * e,
 
   switch (e->event_type)
     {
-    case FIFO_EVENT_APP_RX:
+    case SESSION_IO_EVT_RX:
       ASSERT (e->fifo->client_thread_index == vcl_get_worker_index ());
       vcl_fifo_rx_evt_valid_or_break (e->fifo);
       sid = e->fifo->client_session_index;
@@ -2491,7 +2367,7 @@ vcl_epoll_wait_handle_mq_event (vcl_worker_t * wrk, session_event_t * e,
       session_evt_data = session->vep.ev.data.u64;
       session->has_rx_evt = 1;
       break;
-    case FIFO_EVENT_APP_TX:
+    case SESSION_IO_EVT_TX:
       sid = e->fifo->client_session_index;
       if (!(session = vcl_session_get (wrk, sid)))
 	break;
@@ -2503,33 +2379,6 @@ vcl_epoll_wait_handle_mq_event (vcl_worker_t * wrk, session_event_t * e,
       session_evt_data = session->vep.ev.data.u64;
       svm_fifo_reset_tx_ntf (session->tx_fifo);
       break;
-    case SESSION_IO_EVT_CT_TX:
-      vcl_fifo_rx_evt_valid_or_break (e->fifo);
-      session = vcl_ct_session_get_from_fifo (wrk, e->fifo, 0);
-      if (PREDICT_FALSE (!session))
-	break;
-      sid = session->session_index;
-      session_events = session->vep.ev.events;
-      if (!(EPOLLIN & session->vep.ev.events) || session->has_rx_evt)
-	break;
-      add_event = 1;
-      events[*num_ev].events |= EPOLLIN;
-      session_evt_data = session->vep.ev.data.u64;
-      session->has_rx_evt = 1;
-      break;
-    case SESSION_IO_EVT_CT_RX:
-      session = vcl_ct_session_get_from_fifo (wrk, e->fifo, 1);
-      if (PREDICT_FALSE (!session))
-	break;
-      sid = session->session_index;
-      session_events = session->vep.ev.events;
-      if (!(EPOLLOUT & session_events))
-	break;
-      add_event = 1;
-      events[*num_ev].events |= EPOLLOUT;
-      session_evt_data = session->vep.ev.data.u64;
-      svm_fifo_reset_tx_ntf (session->tx_fifo);
-      break;
     case SESSION_CTRL_EVT_ACCEPTED:
       session = vcl_session_accepted (wrk,
 				      (session_accepted_msg_t *) e->data);
@@ -2663,33 +2512,9 @@ static int
 vppcom_epoll_wait_condvar (vcl_worker_t * wrk, struct epoll_event *events,
 			   int maxevents, u32 n_evts, double wait_for_time)
 {
-  vcl_cut_through_registration_t *cr;
-  double total_wait = 0, wait_slice;
-  int rv;
-
   wait_for_time = (wait_for_time == -1) ? (double) 1e6 : wait_for_time;
-  wait_slice = wrk->cut_through_registrations ? 10e-6 : wait_for_time;
-
-  do
-    {
-      vcl_ct_registration_lock (wrk);
-      /* *INDENT-OFF* */
-      pool_foreach (cr, wrk->cut_through_registrations, ({
-        vcl_epoll_wait_handle_mq (wrk, cr->mq, events, maxevents, 0, &n_evts);
-      }));
-      /* *INDENT-ON* */
-      vcl_ct_registration_unlock (wrk);
-
-      rv = vcl_epoll_wait_handle_mq (wrk, wrk->app_event_queue, events,
-				     maxevents, n_evts ? 0 : wait_slice,
-				     &n_evts);
-      if (rv)
-	total_wait += wait_slice;
-      if (n_evts)
-	return n_evts;
-    }
-  while (total_wait < wait_for_time);
-  return n_evts;
+  return vcl_epoll_wait_handle_mq (wrk, wrk->app_event_queue, events,
+				   maxevents, wait_for_time, &n_evts);
 }
 
 static int