WIP: idle scavenge

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 @@
   // 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;
   }
 
   int64_t DurationMicros() const { return end_micros_ - start_micros_; }
 
+  intptr_t UsedBefore() const { return before_.used_in_words * kWordSize; }
+
  private:
   int64_t start_micros_;
   int64_t end_micros_;
   SpaceUsage before_;
   SpaceUsage after_;
   intptr_t promo_candidates_in_words_;
   intptr_t promoted_in_words_;
 };
 
 class Scavenger {
@@ skipping 96 matching lines @@
   int64_t CapacityInWords() const { return to_->size_in_words(); }
   int64_t ExternalInWords() const { return external_size_ >> kWordSizeLog2; }
   SpaceUsage GetCurrentUsage() const {
     SpaceUsage usage;
     usage.used_in_words = UsedInWords();
     usage.capacity_in_words = CapacityInWords();
     usage.external_in_words = ExternalInWords();
     return usage;
   }
 
+  intptr_t ScavengeRateInBytesPerMicro() const {
+    intptr_t total_used = 0;
+    intptr_t total_micros = 0;
+    for (intptr_t i = 0; i < stats_history_.Size(); i++) {
+      total_used += stats_history_.Get(i).UsedBefore();
+      total_micros += stats_history_.Get(i).DurationMicros();
+    }
+    intptr_t scavenge_rate;
+    if (total_micros != 0) {
+      scavenge_rate = total_used / total_micros;
+    } else {
+      scavenge_rate = 400;  // Conservative initial guess.
+    }
+    if (scavenge_rate == 0) {
+      scavenge_rate = 1;
+    }
+    return scavenge_rate;
+  }
+
+  intptr_t EstimatedScavengeTime() const {
+    return UsedInWords() * kWordSize / ScavengeRateInBytesPerMicro();
+  }
+
   void VisitObjects(ObjectVisitor* visitor) const;
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
   void AddRegionsToObjectSet(ObjectSet* set) const;
 
   void WriteProtect(bool read_only);
 
   void AddGCTime(int64_t micros) { gc_time_micros_ += micros; }
 
   int64_t gc_time_micros() const { return gc_time_micros_; }
@@ skipping 96 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 = 8;
   RingBuffer<ScavengeStats, kStatsHistoryCapacity> stats_history_;
 
   // 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_