- Implement a simple old-generation marker.

vm/pages.h

 // Copyright (c) 2011, 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 VM_PAGES_H_
 #define VM_PAGES_H_
 
 #include "vm/globals.h"
 #include "vm/virtual_memory.h"
 
@@ skipping 67 matching lines @@
   bool Contains(uword addr) const;
   bool IsValidAddress(uword addr) const {
     return Contains(addr);
   }
   static intptr_t IsPageAllocatableSize(intptr_t size) {
     return size <= kAllocatablePageSize;
   }
 
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
+  // Collect the garbage in the page space using mark-sweep.
+  void MarkSweep();
+
  private:
   static const intptr_t kAllocatablePageSize = kPageSize - sizeof(HeapPage);
 
   void AllocatePage();
   HeapPage* AllocateLargePage(intptr_t size);
   void FreePages(HeapPage* pages);
 
   uword TryBumpAllocate(intptr_t size);
 
   Heap* heap_;
 
   HeapPage* pages_;
   HeapPage* pages_tail_;
   HeapPage* large_pages_;
 
   // Various sizes being tracked for this generation.
   intptr_t max_capacity_;
   intptr_t capacity_;
   intptr_t in_use_;
 
+  // Old-gen GC cycle count.
+  int count_;
+
   bool is_executable_;
 
+  // Keep track whether a MarkSweep is currently running.
+  bool sweeping_;
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_