Initial idle GC logic.

runtime/vm/scavenger.h

 // 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.
 
 #ifndef RUNTIME_VM_SCAVENGER_H_
 #define RUNTIME_VM_SCAVENGER_H_
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/dart.h"
@@ skipping 80 matching lines @@
 
   // Fraction of promotion candidates that survived and was thereby promoted.
   // Returns zero if there were no promotion candidates.
   double PromoCandidatesSuccessFraction() const {
     return promo_candidates_in_words_ > 0
                ? promoted_in_words_ /
                      static_cast<double>(promo_candidates_in_words_)
                : 0.0;
   }
 
+  intptr_t UsedBeforeInWords() const { return before_.used_in_words; }
+
   int64_t DurationMicros() const { return end_micros_ - start_micros_; }
 
  private:
   int64_t start_micros_;
   int64_t end_micros_;
   SpaceUsage before_;
   SpaceUsage after_;
   intptr_t promo_candidates_in_words_;
   intptr_t promoted_in_words_;
 };
@@ skipping 104 matching lines @@
     return usage;
   }
 
   void VisitObjects(ObjectVisitor* visitor) const;
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
   void AddRegionsToObjectSet(ObjectSet* set) const;
 
   void WriteProtect(bool read_only);
 
+  bool ShouldPerformIdleScavenge(int64_t deadline);
+
   void AddGCTime(int64_t micros) { gc_time_micros_ += micros; }
 
   int64_t gc_time_micros() const { return gc_time_micros_; }
 
   void IncrementCollections() { collections_++; }
 
   intptr_t collections() const { return collections_; }
 
 #ifndef PRODUCT
   void PrintToJSONObject(JSONObject* object) const;
@@ skipping 89 matching lines @@
   uword object_alignment_;
 
   // Keep track whether a scavenge is currently running.
   bool scavenging_;
 
   // Keep track of pending weak properties discovered while scagenging.
   RawWeakProperty* delayed_weak_properties_;
 
   int64_t gc_time_micros_;
   intptr_t collections_;
-  static const int kStatsHistoryCapacity = 2;
+  static const int kStatsHistoryCapacity = 4;
   RingBuffer<ScavengeStats, kStatsHistoryCapacity> stats_history_;
 
+  intptr_t scavenge_words_per_micro_;
+  intptr_t idle_scavenge_threshold_in_words_;
+
   // The total size of external data associated with objects in this scavenger.
   intptr_t external_size_;
 
   bool failed_to_promote_;
 
   // Protects new space during the allocation of new TLABs
   Mutex* space_lock_;
   friend class ScavengerVisitor;
   friend class ScavengerWeakVisitor;
 
   DISALLOW_COPY_AND_ASSIGN(Scavenger);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_SCAVENGER_H_