commit 470d72f54abbd3e34053cc4f4e281593faf0fb77
author Florin Coras <fcoras@cisco.com> Thu Jun 01 21:50:03 2023 -0700
committer Dave Barach <vpp@barachs.net> Tue Jun 06 18:39:14 2023 +0000
tree 4cd639ffad77d46a67cfda3ce71ff85bea1ffa1a
parent e3d058fc751f8c105f2a91da764e23b701d8a94a

vcl: fix epoll ctl frequent deq ntf requests

SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL should be treated as a
config option that is not frequently changed. Or alternatively, it
should be set together with SVM_FIFO_WANT_DEQ_NOTIF to elicit a one time
tx notification.

Type: fix

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: Ie4132c7789ee87227a875ff981eb98f9f4d898a9

src/vcl/vppcom.c

diff --git a/src/vcl/vppcom.c b/src/vcl/vppcom.c
index 474670e..f2166f8 100644
--- a/src/vcl/vppcom.c
+++ b/src/vcl/vppcom.c
@@ -2868,15 +2868,22 @@
       s->flags |= VCL_SESSION_F_IS_VEP_SESSION;
       vep_session->vep.next_sh = session_handle;
 
-      if (event->events & EPOLLOUT)
-	vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
-
-      /* Generate EPOLLOUT if tx fifo not full */
-      if ((event->events & EPOLLOUT) && (vcl_session_write_ready (s) > 0))
+      if ((event->events & EPOLLOUT))
 	{
-	  vcl_epoll_ctl_add_unhandled_event (wrk, s, event->events & EPOLLET,
-					     SESSION_IO_EVT_TX);
-	  add_evt = 1;
+	  int write_ready = vcl_session_write_ready (s);
+
+	  vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
+	  if (write_ready > 0)
+	    {
+	      /* Generate EPOLLOUT if tx fifo not full */
+	      vcl_epoll_ctl_add_unhandled_event (
+		wrk, s, event->events & EPOLLET, SESSION_IO_EVT_TX);
+	      add_evt = 1;
+	    }
+	  else
+	    {
+	      vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF);
+	    }
 	}
       /* Generate EPOLLIN if rx fifo has data */
       if ((event->events & EPOLLIN) && (vcl_session_read_ready (s) > 0))
@@ -2922,18 +2929,23 @@
 	  goto done;
 	}
 
-      if (event->events & EPOLLOUT)
-	vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
-      else
+      /* Generate EPOLLOUT if session write ready and event was not on */
+      if ((event->events & EPOLLOUT) && !(s->vep.ev.events & EPOLLOUT))
+	{
+	  /* Fifo size load acq synchronized with update store rel */
+	  int write_ready = vcl_session_write_ready (s);
+
+	  vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
+	  if (write_ready > 0)
+	    vcl_epoll_ctl_add_unhandled_event (wrk, s, event->events & EPOLLET,
+					       SESSION_IO_EVT_TX);
+	  else
+	    /* Request deq ntf in case dequeue happened while updating flag */
+	    vcl_session_add_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF);
+	}
+      else if (!(event->events & EPOLLOUT))
 	vcl_session_del_want_deq_ntf (s, SVM_FIFO_WANT_DEQ_NOTIF_IF_FULL);
 
-      /* Generate EPOLLOUT if session write ready nd event was not on */
-      if ((event->events & EPOLLOUT) && !(s->vep.ev.events & EPOLLOUT) &&
-	  (vcl_session_write_ready (s) > 0))
-	{
-	  vcl_epoll_ctl_add_unhandled_event (wrk, s, event->events & EPOLLET,
-					     SESSION_IO_EVT_TX);
-	}
       /* Generate EPOLLIN if session read ready and event was not on */
       if ((event->events & EPOLLIN) && !(s->vep.ev.events & EPOLLIN) &&
 	  (vcl_session_read_ready (s) > 0))