[Isolates] Merge from bleeding_edge, revisions 5934-6100.

src/heap.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3282 matching lines @@
 
   // Copy the characters into the new object.
   SeqAsciiString* string_result = SeqAsciiString::cast(result);
   for (int i = 0; i < string.length(); i++) {
     string_result->SeqAsciiStringSet(i, string[i]);
   }
   return result;
 }
 
 
-MaybeObject* Heap::AllocateStringFromUtf8(Vector<const char> string,
-                                          PretenureFlag pretenure) {
+MaybeObject* Heap::AllocateStringFromUtf8Slow(Vector<const char> string,
+                                              PretenureFlag pretenure) {
   // V8 only supports characters in the Basic Multilingual Plane.
   const uc32 kMaxSupportedChar = 0xFFFF;
   // Count the number of characters in the UTF-8 string and check if
   // it is an ASCII string.
   Access<ScannerConstants::Utf8Decoder>
       decoder(isolate_->scanner_constants()->utf8_decoder());
   decoder->Reset(string.start(), string.length());
   int chars = 0;
-  bool is_ascii = true;
   while (decoder->has_more()) {
-    uc32 r = decoder->GetNext();
-    if (r > String::kMaxAsciiCharCode) is_ascii = false;
+    decoder->GetNext();
     chars++;
   }
 
-  // If the string is ascii, we do not need to convert the characters
-  // since UTF8 is backwards compatible with ascii.
-  if (is_ascii) return AllocateStringFromAscii(string, pretenure);
-
   Object* result;
   { MaybeObject* maybe_result = AllocateRawTwoByteString(chars, pretenure);
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
 
   // Convert and copy the characters into the new object.
   String* string_result = String::cast(result);
   decoder->Reset(string.start(), string.length());
   for (int i = 0; i < chars; i++) {
     uc32 r = decoder->GetNext();
@@ skipping 429 matching lines @@
   }
   Struct::cast(result)->InitializeBody(size);
   return result;
 }
 
 
 bool Heap::IdleNotification() {
   static const int kIdlesBeforeScavenge = 4;
   static const int kIdlesBeforeMarkSweep = 7;
   static const int kIdlesBeforeMarkCompact = 8;
+  static const int kMaxIdleCount = kIdlesBeforeMarkCompact + 1;
+  static const int kGCsBetweenCleanup = 4;
+
   if (!last_idle_notification_gc_count_init_) {
     last_idle_notification_gc_count_ = gc_count_;
     last_idle_notification_gc_count_init_ = true;
   }
 
   bool uncommit = true;
   bool finished = false;
 
-  if (last_idle_notification_gc_count_ == gc_count_) {
-    number_idle_notifications_++;
+  // Reset the number of idle notifications received when a number of
+  // GCs have taken place. This allows another round of cleanup based
+  // on idle notifications if enough work has been carried out to
+  // provoke a number of garbage collections.
+  if (gc_count_ < last_idle_notification_gc_count_ + kGCsBetweenCleanup) {
+    number_idle_notifications_ =
+        Min(number_idle_notifications_ + 1, kMaxIdleCount);
   } else {
     number_idle_notifications_ = 0;
     last_idle_notification_gc_count_ = gc_count_;
   }
 
   if (number_idle_notifications_ == kIdlesBeforeScavenge) {
     if (contexts_disposed_ > 0) {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
       CollectAllGarbage(false);
     } else {
       CollectGarbage(NEW_SPACE);
     }
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
-
   } else if (number_idle_notifications_ == kIdlesBeforeMarkSweep) {
     // Before doing the mark-sweep collections we clear the
     // compilation cache to avoid hanging on to source code and
     // generated code for cached functions.
     isolate_->compilation_cache()->Clear();
 
     CollectAllGarbage(false);
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
 
   } else if (number_idle_notifications_ == kIdlesBeforeMarkCompact) {
     CollectAllGarbage(true);
     new_space_.Shrink();
     last_idle_notification_gc_count_ = gc_count_;
     number_idle_notifications_ = 0;
     finished = true;
-
   } else if (contexts_disposed_ > 0) {
     if (FLAG_expose_gc) {
       contexts_disposed_ = 0;
     } else {
       HistogramTimerScope scope(isolate_->counters()->gc_context());
       CollectAllGarbage(false);
       last_idle_notification_gc_count_ = gc_count_;
     }
     // If this is the first idle notification, we reset the
     // notification count to avoid letting idle notifications for
     // context disposal garbage collections start a potentially too
     // aggressive idle GC cycle.
     if (number_idle_notifications_ <= 1) {
       number_idle_notifications_ = 0;
       uncommit = false;
     }
+  } else if (number_idle_notifications_ > kIdlesBeforeMarkCompact) {
+    // If we have received more than kIdlesBeforeMarkCompact idle
+    // notifications we do not perform any cleanup because we don't
+    // expect to gain much by doing so.
+    finished = true;
   }
 
   // Make sure that we have no pending context disposals and
   // conditionally uncommit from space.
   ASSERT(contexts_disposed_ == 0);
   if (uncommit) UncommitFromSpace();
   return finished;
 }
 
 
@@ skipping 647 matching lines @@
   *stats->cell_space_capacity = cell_space_->Capacity();
   *stats->lo_space_size = lo_space_->Size();
   isolate_->global_handles()->RecordStats(stats);
   *stats->memory_allocator_size = isolate()->memory_allocator()->Size();
   *stats->memory_allocator_capacity =
       isolate()->memory_allocator()->Size() +
       isolate()->memory_allocator()->Available();
   *stats->os_error = OS::GetLastError();
       isolate()->memory_allocator()->Available();
   if (take_snapshot) {
-    HeapIterator iterator(HeapIterator::kPreciseFiltering);
+    HeapIterator iterator(HeapIterator::kFilterFreeListNodes);
     for (HeapObject* obj = iterator.next();
          obj != NULL;
          obj = iterator.next()) {
       InstanceType type = obj->map()->instance_type();
       ASSERT(0 <= type && type <= LAST_TYPE);
       stats->objects_per_type[type]++;
       stats->size_per_type[type] += obj->Size();
     }
   }
 }
@@ skipping 603 matching lines @@
       iterator_ = new LargeObjectIterator(HEAP->lo_space(), size_func_);
       break;
   }
 
   // Return the newly allocated iterator;
   ASSERT(iterator_ != NULL);
   return iterator_;
 }
 
 
-class FreeListNodesFilter {
+class HeapObjectsFilter {
+ public:
+  virtual ~HeapObjectsFilter() {}
+  virtual bool SkipObject(HeapObject* object) = 0;
+};
+
+
+class FreeListNodesFilter : public HeapObjectsFilter {
  public:
   FreeListNodesFilter() {
     MarkFreeListNodes();
   }
 
-  inline bool IsFreeListNode(HeapObject* object) {
+  bool SkipObject(HeapObject* object) {
     if (object->IsMarked()) {
       object->ClearMark();
       return true;
     } else {
       return false;
     }
   }
 
  private:
   void MarkFreeListNodes() {
@@ skipping 12 matching lines @@
          obj != NULL;
          obj = iter.next_object()) {
       if (FreeListNode::IsFreeListNode(obj)) obj->SetMark();
     }
   }
 
   AssertNoAllocation no_alloc;
 };
 
 
+class UnreachableObjectsFilter : public HeapObjectsFilter {
+ public:
+  UnreachableObjectsFilter() {
+    MarkUnreachableObjects();
+  }
+
+  bool SkipObject(HeapObject* object) {
+    if (object->IsMarked()) {
+      object->ClearMark();
+      return true;
+    } else {
+      return false;
+    }
+  }
+
+ private:
+  class UnmarkingVisitor : public ObjectVisitor {
+   public:
+    UnmarkingVisitor() : list_(10) {}
+
+    void VisitPointers(Object** start, Object** end) {
+      for (Object** p = start; p < end; p++) {
+        if (!(*p)->IsHeapObject()) continue;
+        HeapObject* obj = HeapObject::cast(*p);
+        if (obj->IsMarked()) {
+          obj->ClearMark();
+          list_.Add(obj);
+        }
+      }
+    }
+
+    bool can_process() { return !list_.is_empty(); }
+
+    void ProcessNext() {
+      HeapObject* obj = list_.RemoveLast();
+      obj->Iterate(this);
+    }
+
+   private:
+    List<HeapObject*> list_;
+  };
+
+  void MarkUnreachableObjects() {
+    HeapIterator iterator;
+    for (HeapObject* obj = iterator.next();
+         obj != NULL;
+         obj = iterator.next()) {
+      obj->SetMark();
+    }
+    UnmarkingVisitor visitor;
+    HEAP->IterateRoots(&visitor, VISIT_ONLY_STRONG);
+    while (visitor.can_process())
+      visitor.ProcessNext();
+  }
+
+  AssertNoAllocation no_alloc;
+};
+
+
 HeapIterator::HeapIterator()
     : filtering_(HeapIterator::kNoFiltering),
       filter_(NULL) {
   Init();
 }
 
 
-HeapIterator::HeapIterator(HeapIterator::FreeListNodesFiltering filtering)
+HeapIterator::HeapIterator(HeapIterator::HeapObjectsFiltering filtering)
     : filtering_(filtering),
       filter_(NULL) {
   Init();
 }
 
 
 HeapIterator::~HeapIterator() {
   Shutdown();
 }
 
 
 void HeapIterator::Init() {
   // Start the iteration.
-  if (filtering_ == kPreciseFiltering) {
-    filter_ = new FreeListNodesFilter;
-    space_iterator_ =
-        new SpaceIterator(MarkCompactCollector::SizeOfMarkedObject);
-  } else {
-    space_iterator_ = new SpaceIterator;
+  space_iterator_ = filtering_ == kNoFiltering ? new SpaceIterator :
+      new SpaceIterator(MarkCompactCollector::SizeOfMarkedObject);
+  switch (filtering_) {
+    case kFilterFreeListNodes:
+      filter_ = new FreeListNodesFilter;
+      break;
+    case kFilterUnreachable:
+      filter_ = new UnreachableObjectsFilter;
+      break;
+    default:
+      break;
   }
   object_iterator_ = space_iterator_->next();
 }
 
 
 void HeapIterator::Shutdown() {
 #ifdef DEBUG
-  // Assert that in precise mode we have iterated through all
+  // Assert that in filtering mode we have iterated through all
   // objects. Otherwise, heap will be left in an inconsistent state.
-  if (filtering_ == kPreciseFiltering) {
+  if (filtering_ != kNoFiltering) {
     ASSERT(object_iterator_ == NULL);
   }
 #endif
   // Make sure the last iterator is deallocated.
   delete space_iterator_;
   space_iterator_ = NULL;
   object_iterator_ = NULL;
   delete filter_;
   filter_ = NULL;
 }
 
 
 HeapObject* HeapIterator::next() {
   if (filter_ == NULL) return NextObject();
 
   HeapObject* obj = NextObject();
-  while (obj != NULL && filter_->IsFreeListNode(obj)) obj = NextObject();
+  while (obj != NULL && filter_->SkipObject(obj)) obj = NextObject();
   return obj;
 }
 
 
 HeapObject* HeapIterator::NextObject() {
   // No iterator means we are done.
   if (object_iterator_ == NULL) return NULL;
 
   if (HeapObject* obj = object_iterator_->next_object()) {
     // If the current iterator has more objects we are fine.
@@ skipping 274 matching lines @@
 }
 
 
 void ExternalStringTable::TearDown() {
   new_space_strings_.Free();
   old_space_strings_.Free();
 }
 
 
 } }  // namespace v8::internal