Fuchsia: Throttle epoll to prevent message queues from being overwhelmed with level-triggered event…

runtime/bin/eventhandler_fuchsia.cc

 // Copyright (c) 2016, 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.
 
 #if !defined(DART_IO_DISABLED)
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_FUCHSIA)
 
 #include "bin/eventhandler.h"
@@ skipping 431 matching lines @@
 void EventHandlerImplementation::Poll(uword args) {
   static const intptr_t kMaxEvents = 16;
   struct epoll_event events[kMaxEvents];
   EventHandler* handler = reinterpret_cast<EventHandler*>(args);
   EventHandlerImplementation* handler_impl = &handler->delegate_;
   ASSERT(handler_impl != NULL);
 
   while (!handler_impl->shutdown_) {
     int64_t millis = handler_impl->GetTimeout();
     ASSERT((millis == kInfinityTimeout) || (millis >= 0));
+    // TODO(US-109): When the epoll implementation is properly edge-triggered,
+    // remove this sleep, which prevents the message queue from being
+    // overwhelmed and leading to memory exhaustion.
+    usleep(5000);
     LOG_INFO("epoll_wait(millis = %ld)\n", millis);
     intptr_t result = NO_RETRY_EXPECTED(
         epoll_wait(handler_impl->epoll_fd_, events, kMaxEvents, millis));
     ASSERT(EAGAIN == EWOULDBLOCK);
     LOG_INFO("epoll_wait(millis = %ld) -> %ld\n", millis, result);
     if (result < 0) {
       if (errno != EWOULDBLOCK) {
         perror("Poll failed");
       }
     } else {
@@ skipping 35 matching lines @@
   // The hashmap does not support keys with value 0.
   return dart::Utils::WordHash(fd + 1);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_FUCHSIA)
 
 #endif  // !defined(DART_IO_DISABLED)