- Free completely empty pages as part of sweep.

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/freelist.h"
 #include "vm/globals.h"
 #include "vm/virtual_memory.h"
@@ skipping 94 matching lines @@
 
   static HeapPage* PageFor(RawObject* raw_obj) {
     return reinterpret_cast<HeapPage*>(
         RawObject::ToAddr(raw_obj) & ~(kPageSize -1));
   }
 
  private:
   static const intptr_t kAllocatablePageSize = kPageSize - sizeof(HeapPage);
 
   void AllocatePage();
+  void FreePage(HeapPage* page, HeapPage* previous_page);
   HeapPage* AllocateLargePage(intptr_t size);
   void FreeLargePage(HeapPage* page, HeapPage* previous_page);
   void FreePages(HeapPage* pages);
 
   static intptr_t LargePageSizeFor(intptr_t size);
   bool CanIncreaseCapacity(intptr_t increase) {
     ASSERT(capacity_ <= max_capacity_);
     return increase <= (max_capacity_ - capacity_);
   }
 
   uword TryBumpAllocate(intptr_t size);
 
   FreeList freelist_;
 
   Heap* heap_;
 
   HeapPage* pages_;
-  HeapPage* pages_tail_;
   HeapPage* large_pages_;
 
   // Page being used for bump allocation.
   // The value has different meanings:
   // NULL: Still bump allocating from last allocated fresh page.
   // !NULL: Last page that had enough room to bump allocate, when we reach the
   // tail page, we give up bump allocating.
   HeapPage* bump_page_;
 
   // 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_