Count m(un)map for each stacktrace in MemoryRegionMap instead of HeapProfileTable.

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

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file defines structs to accumulate memory allocation and deallocation
+// counts.  These structs are commonly used for malloc (in HeapProfileTable)
+// and mmap (in MemoryRegionMap).
+
+// A bucket is data structure for heap profiling to store a pair of a stack
+// trace and counts of (de)allocation.  Buckets are stored in a hash table
+// which is declared as "HeapProfileBucket**".
+//
+// A hash value is computed from a stack trace.  Collision in the hash table
+// is resolved by separate chaining with linked lists.  The links in the list
+// are implemented with the member "HeapProfileBucket* next".
+//
+// A structure of a hash table HeapProfileBucket** bucket_table would be like:
+// bucket_table[0] => NULL
+// bucket_table[1] => HeapProfileBucket() => HeapProfileBucket() => NULL
+// ...
+// bucket_table[i] => HeapProfileBucket() => NULL
+// ...
+// bucket_table[n] => HeapProfileBucket() => NULL
+
+#ifndef HEAP_PROFILE_STATS_H_
+#define HEAP_PROFILE_STATS_H_
+
+struct HeapProfileStats {
+  // Returns true if the two HeapProfileStats are semantically equal.
+  bool Equivalent(const HeapProfileStats& other) const {
+    return allocs - frees == other.allocs - other.frees &&
+        alloc_size - free_size == other.alloc_size - other.free_size;
+  }
+
+  int32 allocs;      // Number of allocation calls.
+  int32 frees;       // Number of free calls.
+  int64 alloc_size;  // Total size of all allocated objects so far.
+  int64 free_size;   // Total size of all freed objects so far.
+};
+
+// Allocation and deallocation statistics per each stack trace.
+struct HeapProfileBucket : public HeapProfileStats {
+  // Longest stack trace we record.
+  static const int kMaxStackDepth = 32;
+
+  uintptr_t hash;           // Hash value of the stack trace.
+  int depth;                // Depth of stack trace.
+  const void** stack;       // Stack trace.
+  HeapProfileBucket* next;  // Next entry in hash-table.
+};
+
+#endif  // HEAP_PROFILE_STATS_H_