Allow IdleNotification to trigger Scavenges.

src/heap/gc-idle-time-handler.cc

Index: src/heap/gc-idle-time-handler.cc
diff --git a/src/heap/gc-idle-time-handler.cc b/src/heap/gc-idle-time-handler.cc
index 8def9005e647b344685050b96c19bac4fa1e3e98..03232fa2cfb24d7d14ef4ef59369a36d41172aa8 100644
--- a/src/heap/gc-idle-time-handler.cc
+++ b/src/heap/gc-idle-time-handler.cc
@@ -68,9 +68,40 @@ size_t GCIdleTimeHandler::EstimateMarkCompactTime(
 }
 
 
+size_t GCIdleTimeHandler::EstimateScavengeTime(
+    size_t new_space_size, size_t scavenge_speed_in_bytes_per_ms) {
+  if (scavenge_speed_in_bytes_per_ms == 0) {
+    scavenge_speed_in_bytes_per_ms = kInitialConservativeScavengeSpeed;
+  }
+  return new_space_size / scavenge_speed_in_bytes_per_ms;
+}
+
+
+// The following logic is implemented by the controller:
+// (1) If the new space is almost full and we can effort a Scavenge, then a
+// Scavenge is performed.
+// (2) If there is currently no MarkCompact idle round going on, we start a
+// new idle round if enough garbage was created or we received a context
+// disposal event. Otherwise we do not perform garbage collection to keep
+// system utilization low.
+// (3) If incremental marking is done, we perform a full garbage collection
+// if context was disposed or if we are allowed to still do full garbage
+// collections during this idle round or if we are not allowed to start
+// incremental marking. Otherwise we do not perform garbage collection to
+// keep system utilization low.
+// (4) If sweeping is in progress and we received a large enough idle time
+// request, we finalize sweeping here.
+// (5) If incremental marking is in progress, we perform a marking step. Note,
+// that this currently may trigger a full garbage collection.
 GCIdleTimeAction GCIdleTimeHandler::Compute(size_t idle_time_in_ms,
                                             HeapState heap_state) {
-  if (IsIdleRoundFinished()) {
+  if (heap_state.available_new_space_memory < kNewSpaceAlmostFullTreshold &&
+      idle_time_in_ms >=
+          EstimateScavengeTime(heap_state.new_space_capacity,
+                               heap_state.scavenge_speed_in_bytes_per_ms)) {
+    return GCIdleTimeAction::Scavenge();
+  }
+  if (IsMarkCompactIdleRoundFinished()) {
     if (EnoughGarbageSinceLastIdleRound() || heap_state.contexts_disposed > 0) {
       StartIdleRound();
     } else {