Only return eventhandler tokens in stacks of 8, to avoid runtime calls.

runtime/bin/eventhandler_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/eventhandler.h"
 
 #include <errno.h>  // NOLINT
@@ skipping 191 matching lines @@
         ASSERT(msg[i].data == (1 << kCloseCommand));
         // Close the socket and free system resources and move on to
         // next message.
         RemoveFromEpollInstance(epoll_fd_, sd);
         intptr_t fd = sd->fd();
         sd->Close();
         socket_map_.Remove(GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd));
         delete sd;
         DartUtils::PostInt32(msg[i].dart_port, 1 << kDestroyedEvent);
       } else if ((msg[i].data & (1 << kReturnTokenCommand)) != 0) {
-        if (sd->ReturnToken()) {
-          AddToEpollInstance(epoll_fd_, sd);
+        int count = msg[i].data & ((1 << kReturnTokenCommand) - 1);
+        for (int i = 0; i < count; i++) {
+          if (sd->ReturnToken()) {
+            AddToEpollInstance(epoll_fd_, sd);
+          }
         }
       } else {
         // Setup events to wait for.
         sd->SetPortAndMask(msg[i].dart_port, msg[i].data);
         AddToEpollInstance(epoll_fd_, sd);
       }
     }
   }
 }
 
@@ skipping 44 matching lines @@
       int64_t val;
       VOID_TEMP_FAILURE_RETRY(read(timer_fd_, &val, sizeof(val)));
       if (timeout_queue_.HasTimeout()) {
         DartUtils::PostNull(timeout_queue_.CurrentPort());
         timeout_queue_.RemoveCurrent();
       }
     } else {
       SocketData* sd = reinterpret_cast<SocketData*>(events[i].data.ptr);
       intptr_t event_mask = GetPollEvents(events[i].events, sd);
       if (event_mask != 0) {
-        if (sd->TakeToken()) {
+        if (!sd->IsListeningSocket() && sd->TakeToken()) {
           // Took last token, remove from epoll.
           RemoveFromEpollInstance(epoll_fd_, sd);
         }
         Dart_Port port = sd->port();
         ASSERT(port != 0);
         DartUtils::PostInt32(port, event_mask);
       }
     }
   }
   if (interrupt_seen) {
@@ skipping 57 matching lines @@
 
 uint32_t EventHandlerImplementation::GetHashmapHashFromFd(intptr_t fd) {
   // The hashmap does not support keys with value 0.
   return dart::Utils::WordHash(fd + 1);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)