Limit the number of syscalls made by the Eventhandler.

runtime/bin/eventhandler_linux.cc

Index: runtime/bin/eventhandler_linux.cc
diff --git a/runtime/bin/eventhandler_linux.cc b/runtime/bin/eventhandler_linux.cc
index 11e11d3d6f28d74511a65ccb5ad5b1b3bec11a42..5b180fc5aa1b91ac63a6be1c596e20143e2e1641 100644
--- a/runtime/bin/eventhandler_linux.cc
+++ b/runtime/bin/eventhandler_linux.cc
@@ -74,6 +74,9 @@ static void UpdateEpollInstance(intptr_t epoll_fd_, SocketData* sd) {
   event.events = sd->GetPollEvents();
   event.data.ptr = sd;
   if (sd->port() != 0 && event.events != 0) {
+    // Only report events once and wait for them to be re-enabled after the
+    // event has been handled by the Dart code.
+    event.events |= EPOLLONESHOT;
     int status = 0;
     if (sd->tracked_by_epoll()) {
       status = TEMP_FAILURE_RETRY(epoll_ctl(epoll_fd_,
@@ -342,10 +345,6 @@ void EventHandlerImplementation::HandleEvents(struct epoll_event* events,
       SocketData* sd = reinterpret_cast<SocketData*>(events[i].data.ptr);
       intptr_t event_mask = GetPollEvents(events[i].events, sd);
       if (event_mask != 0) {
-        // Unregister events for the file descriptor. Events will be
-        // registered again when the current event has been handled in
-        // Dart code.
-        RemoveFromEpollInstance(epoll_fd_, sd);
         Dart_Port port = sd->port();
         ASSERT(port != 0);
         DartUtils::PostInt32(port, event_mask);
@@ -402,8 +401,9 @@ void EventHandlerImplementation::Poll(uword args) {
       if (errno != EWOULDBLOCK) {
         perror("Poll failed");
       }
-    } else {
+    } else if (result == 0) {
       handler_impl->HandleTimeout();
+    } else {
       handler_impl->HandleEvents(events, result);
     }
   }