session: basic support for interrupt mode

Experimental support for session layer interrupt mode.  When enabled
(use-private-rx-mqs must be set) session queue node switches to
interrupt state when lightly loaded, i.e., no events and less than 1
vector/dispatch.

Because transport protocols require a periodic time update, when in
interrupt state the session queue node workers register a timerfd with
the unix-epoll-input node that when triggered signals, i.e., wakes up,
the queue node. Under light load, the timer is set to trigger every 1ms
whereas if no session is allocated, the worker moves to idle state and
the timeout is set to 100ms.

Type: feature

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I905b00777fbc025faf9c4074fce4c516cd139387

1 files changed, 26 insertions, 4 deletions

diff --git a/src/vnet/session/session.c b/src/vnet/session/session.c
index c24a95fd9a6..7513aa32ed8 100644
--- a/src/vnet/session/session.c
+++ b/src/vnet/session/session.c
@@ -28,11 +28,12 @@ static inline int
 session_send_evt_to_thread (void *data, void *args, u32 thread_index,
 			    session_evt_type_t evt_type)
 {
+  session_worker_t *wrk = session_main_get_worker (thread_index);
   session_event_t *evt;
   svm_msg_q_msg_t msg;
   svm_msg_q_t *mq;
 
-  mq = session_main_get_vpp_event_queue (thread_index);
+  mq = wrk->vpp_event_queue;
   if (PREDICT_FALSE (svm_msg_q_lock (mq)))
     return -1;
   if (PREDICT_FALSE (svm_msg_q_is_full (mq)
@@ -72,6 +73,10 @@ session_send_evt_to_thread (void *data, void *args, u32 thread_index,
   evt->event_type = evt_type;
 
   svm_msg_q_add_and_unlock (mq, &msg);
+
+  if (PREDICT_FALSE (wrk->state == SESSION_WRK_INTERRUPT))
+    vlib_node_set_interrupt_pending (wrk->vm, session_queue_node.index);
+
   return 0;
 }
 
@@ -121,19 +126,20 @@ session_send_rpc_evt_to_thread (u32 thread_index, void *fp, void *rpc_args)
 void
 session_add_self_custom_tx_evt (transport_connection_t * tc, u8 has_prio)
 {
-  session_t *s;
+  session_t *s = session_get (tc->s_index, tc->thread_index);
 
-  s = session_get (tc->s_index, tc->thread_index);
   ASSERT (s->thread_index == vlib_get_thread_index ());
   ASSERT (s->session_state != SESSION_STATE_TRANSPORT_DELETED);
+
   if (!(s->flags & SESSION_F_CUSTOM_TX))
     {
       s->flags |= SESSION_F_CUSTOM_TX;
       if (svm_fifo_set_event (s->tx_fifo)
 	  || transport_connection_is_descheduled (tc))
 	{
-	  session_worker_t *wrk;
 	  session_evt_elt_t *elt;
+	  session_worker_t *wrk;
+
 	  wrk = session_main_get_worker (tc->thread_index);
 	  if (has_prio)
 	    elt = session_evt_alloc_new (wrk);
@@ -142,6 +148,10 @@ session_add_self_custom_tx_evt (transport_connection_t * tc, u8 has_prio)
 	  elt->evt.session_index = tc->s_index;
 	  elt->evt.event_type = SESSION_IO_EVT_TX;
 	  tc->flags &= ~TRANSPORT_CONNECTION_F_DESCHED;
+
+	  if (PREDICT_FALSE (wrk->state == SESSION_WRK_INTERRUPT))
+	    vlib_node_set_interrupt_pending (wrk->vm,
+					     session_queue_node.index);
 	}
     }
 }
@@ -157,6 +167,9 @@ sesssion_reschedule_tx (transport_connection_t * tc)
   elt = session_evt_alloc_new (wrk);
   elt->evt.session_index = tc->s_index;
   elt->evt.event_type = SESSION_IO_EVT_TX;
+
+  if (PREDICT_FALSE (wrk->state == SESSION_WRK_INTERRUPT))
+    vlib_node_set_interrupt_pending (wrk->vm, session_queue_node.index);
 }
 
 static void
@@ -175,6 +188,9 @@ session_program_transport_ctrl_evt (session_t * s, session_evt_type_t evt)
       clib_memset (&elt->evt, 0, sizeof (session_event_t));
       elt->evt.session_handle = session_handle (s);
       elt->evt.event_type = evt;
+
+      if (PREDICT_FALSE (wrk->state == SESSION_WRK_INTERRUPT))
+	vlib_node_set_interrupt_pending (wrk->vm, session_queue_node.index);
     }
   else
     session_send_ctrl_evt_to_thread (s, evt);
@@ -1693,6 +1709,9 @@ session_manager_main_enable (vlib_main_t * vm)
 
       if (num_threads > 1)
 	clib_rwlock_init (&smm->wrk[i].peekers_rw_locks);
+
+      if (!smm->no_adaptive && smm->use_private_rx_mqs)
+	session_wrk_enable_adaptive_mode (wrk);
     }
 
   /* Allocate vpp event queues segment and queue */
@@ -1817,6 +1836,7 @@ session_main_init (vlib_main_t * vm)
   smm->session_enable_asap = 0;
   smm->poll_main = 0;
   smm->use_private_rx_mqs = 0;
+  smm->no_adaptive = 0;
   smm->session_baseva = HIGH_SEGMENT_BASEVA;
 
 #if (HIGH_SEGMENT_BASEVA > (4ULL << 30))
@@ -1938,6 +1958,8 @@ session_config_fn (vlib_main_t * vm, unformat_input_t * input)
 	smm->poll_main = 1;
       else if (unformat (input, "use-private-rx-mqs"))
 	smm->use_private_rx_mqs = 1;
+      else if (unformat (input, "no-adaptive"))
+	smm->no_adaptive = 1;
       else
 	return clib_error_return (0, "unknown input `%U'",
 				  format_unformat_error, input);