session: reschedule asap when snd space constrained

Type: feature

Improves fairness for sessions that are snd space or pacer constrained.

Change-Id: Ida5f523090f1dcbfb17bf5116bc7917747ac8593
Signed-off-by: Florin Coras <fcoras@cisco.com>

diff --git a/src/vnet/session/session.h b/src/vnet/session/session.h
index f738f39..9fe35b1 100644 (file)
--- a/src/vnet/session/session.h
+++ b/src/vnet/session/session.h
@@ -221,6 +221,14 @@ session_evt_add_old (session_worker_t * wrk, session_evt_elt_t * elt)
                       pool_elt_at_index (wrk->event_elts, wrk->old_head));
 }
 
+static inline void
+session_evt_add_head_old (session_worker_t * wrk, session_evt_elt_t * elt)
+{
+  clib_llist_add (wrk->event_elts, evt_list, elt,
+                 pool_elt_at_index (wrk->event_elts, wrk->old_head));
+}
+
+
 static inline u32
 session_evt_ctrl_data_alloc (session_worker_t * wrk)
 {

diff --git a/src/vnet/session/session_node.c b/src/vnet/session/session_node.c
index b4b384f..3bfc80e 100644 (file)
--- a/src/vnet/session/session_node.c
+++ b/src/vnet/session/session_node.c
@@ -865,14 +865,22 @@ session_tx_fifo_read_and_snd_i (session_worker_t * wrk,
     }
 
   ctx->snd_mss = ctx->transport_vft->send_mss (ctx->tc);
+  if (PREDICT_FALSE (ctx->snd_mss == 0))
+    {
+      session_evt_add_old (wrk, elt);
+      return SESSION_TX_NO_DATA;
+    }
+
   ctx->snd_space = transport_connection_snd_space (ctx->tc,
                                                   vm->clib_time.
                                                   last_cpu_time,
                                                   ctx->snd_mss);
 
-  if (ctx->snd_space == 0 || ctx->snd_mss == 0)
+  /* This flow queue is "empty" so it should be re-evaluated before
+   * the ones that have data to send. */
+  if (ctx->snd_space == 0)
     {
-      session_evt_add_old (wrk, elt);
+      session_evt_add_head_old (wrk, elt);
       return SESSION_TX_NO_DATA;
     }
 
@@ -898,7 +906,7 @@ session_tx_fifo_read_and_snd_i (session_worker_t * wrk,
     {
       if (n_bufs)
        vlib_buffer_free (vm, wrk->tx_buffers, n_bufs);
-      session_evt_add_old (wrk, elt);
+      session_evt_add_head_old (wrk, elt);
       vlib_node_increment_counter (wrk->vm, node->node_index,
                                   SESSION_QUEUE_ERROR_NO_BUFFER, 1);
       return SESSION_TX_NO_BUFFERS;
@@ -1321,19 +1329,24 @@ session_queue_node_fn (vlib_main_t * vm, vlib_node_runtime_t * node,
 
   if (old_ti != wrk->old_head)
     {
+      clib_llist_index_t ei, next_ei;
+
       old_he = pool_elt_at_index (wrk->event_elts, wrk->old_head);
+      ei = clib_llist_next_index (old_he, evt_list);
+
       while (n_tx_packets < VLIB_FRAME_SIZE)
        {
-         clib_llist_index_t ei;
+         elt = pool_elt_at_index (wrk->event_elts, ei);
+         next_ei = clib_llist_next_index (elt, evt_list);
+         clib_llist_remove (wrk->event_elts, evt_list, elt);
 
-         clib_llist_pop_first (wrk->event_elts, evt_list, elt, old_he);
-         ei = clib_llist_entry_index (wrk->event_elts, elt);
          session_event_dispatch_io (wrk, node, elt, thread_index,
                                     &n_tx_packets);
 
-         old_he = pool_elt_at_index (wrk->event_elts, wrk->old_head);
          if (ei == old_ti)
            break;
+
+         ei = next_ei;
        };
     }