Simplify call to V8::IdleNotification

Run a max priority ev_timer every 2 seconds. If there aren't any pending
watchers then call V8::IdleNotification() once. This is slower at freeing
memory, but I think simpler and less aggressive.

src/node.cc

@@ -68,32 +68,17 @@ static ev_async eio_want_poll_notifier;
 static ev_async eio_done_poll_notifier;
 static ev_idle  eio_poller;
 
-static ev_idle  gc_idle_watcher;
 static ev_timer  gc_timer;
-#define GC_INTERVAL 1.0
+#define GC_INTERVAL 2.0
 
 
-// Node calls this every GC_INTERVAL seconds in order to try
-// and turn on the gc_idle_watcher, which will eventually (when the process
-// isn't busy) call the GC
+// Node calls this every GC_INTERVAL seconds in order to try and call the
+// GC. This watcher is run with maximum priority, so ev_pending_count() == 0
+// is an effective measure of idleness.
 static void GCTimeout(EV_P_ ev_timer *watcher, int revents) {
   assert(watcher == &gc_timer);
   assert(revents == EV_TIMER);
-
-  if (ev_pending_count() == 0 && !ev_is_active(&gc_idle_watcher)) {
-    ev_idle_start(EV_DEFAULT_UC_ &gc_idle_watcher);
-    ev_unref(EV_DEFAULT_UC);
-  }
-}
-
-
-static void DoGC(EV_P_ ev_idle *watcher, int revents) {
-  assert(watcher == &gc_idle_watcher);
-  assert(revents == EV_IDLE);
-  if (V8::IdleNotification()) {
-    ev_ref(EV_DEFAULT_UC);
-    ev_idle_stop(EV_DEFAULT_UC_ watcher);
-  }
+  if (ev_pending_count() == 0) V8::IdleNotification();
 }
 
 
@@ -1154,12 +1139,13 @@ int main(int argc, char *argv[]) {
   ev_default_loop(EVFLAG_AUTO);
 
 
-  // The idle watcher which will call GC
-  ev_idle_init(&node::gc_idle_watcher, node::DoGC);
-  ev_set_priority(&node::gc_idle_watcher, EV_MINPRI);
-  // The check for pending events (will start the idle watcher)
   ev_timer_init(&node::gc_timer, node::GCTimeout, GC_INTERVAL, GC_INTERVAL);
-  ev_set_priority(&node::gc_timer, EV_MINPRI);
+  // Set the gc_timer to max priority so that it runs before all other
+  // watchers. In this way it can check if the 'tick' has other pending
+  // watchers by using ev_pending_count() - if it ran with lower priority
+  // then the other watchers might run before it - not giving us good idea
+  // of loop idleness. 
+  ev_set_priority(&node::gc_timer, EV_MAXPRI);
   ev_timer_start(EV_DEFAULT_UC_ &node::gc_timer);
   ev_unref(EV_DEFAULT_UC);