Reserve a dedicated arena for every construction of mmap_address_map.

third_party/tcmalloc/chromium/src/heap-profile-table.h

 // Copyright (c) 2006, Google Inc.
 // 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
@@ skipping 172 matching lines @@
 
   // Return a snapshot of every non-live, non-ignored object in *this.
   // If "base" is non-NULL, skip any objects present in "base".
   // As a side-effect, clears the "live" bit on every live object in *this.
   // Caller must call ReleaseSnapshot() on result when no longer needed.
   Snapshot* NonLiveSnapshot(Snapshot* base);
 
   // Refresh the internal mmap information from MemoryRegionMap.  Results of
   // FillOrderedProfile and IterateOrderedAllocContexts will contain mmap'ed
   // memory regions as at calling RefreshMMapData.
-  void RefreshMMapData();
+  // 'mmap_alloc' is an allocator for an address map.  A function which calls
+  // LowLevelAlloc::AllocWithArena is expected like the constractor.
+  // 'mmap_dealloc' is a corresponding deallocator to 'mmap_alloc'.
+  // They are introduced to avoid expected memory fragmentation and bloat in
+  // an arena.  A dedicated arena for this function allows disposing whole the
+  // arena after ClearMMapData.
+  void RefreshMMapData(Allocator mmap_alloc, DeAllocator mmap_dealloc);
 
   // Clear the internal mmap information.  Results of FillOrderedProfile and
   // IterateOrderedAllocContexts won't contain mmap'ed memory regions after
   // calling ClearMMapData.
   void ClearMMapData();
 
  private:
   friend class DeepHeapProfile;
 
   // data types ----------------------------
@@ skipping 210 matching lines @@
   // Helpers for sorting and generating leak reports
   struct Entry;
   struct ReportState;
   static void ReportCallback(const void* ptr, AllocValue* v, ReportState*);
   static void ReportObject(const void* ptr, AllocValue* v, char*);
 
   DISALLOW_COPY_AND_ASSIGN(Snapshot);
 };
 
 #endif  // BASE_HEAP_PROFILE_TABLE_H_