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

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file defines structs to accumulate memory allocation and deallocation
   6 // counts.  These structs are commonly used for malloc (in HeapProfileTable)
   7 // and mmap (in MemoryRegionMap).
   8
   9 // A bucket is data structure for heap profiling to store a pair of a stack
  10 // trace and counts of (de)allocation.  Buckets are stored in a hash table
  11 // which is declared as "HeapProfileBucket**".
  12 //
  13 // A hash value is computed from a stack trace.  Collision in the hash table
  14 // is resolved by separate chaining with linked lists.  The links in the list
  15 // are implemented with the member "HeapProfileBucket* next".
  16 //
  17 // A structure of a hash table HeapProfileBucket** bucket_table would be like:
  18 // bucket_table[0] => NULL
  19 // bucket_table[1] => HeapProfileBucket() => HeapProfileBucket() => NULL
  20 // ...
  21 // bucket_table[i] => HeapProfileBucket() => NULL
  22 // ...
  23 // bucket_table[n] => HeapProfileBucket() => NULL
  24
  25 #ifndef HEAP_PROFILE_STATS_H_
  26 #define HEAP_PROFILE_STATS_H_
  27
  28 struct HeapProfileStats {
  29   // Returns true if the two HeapProfileStats are semantically equal.
  30   bool Equivalent(const HeapProfileStats& other) const {
  31     return allocs - frees == other.allocs - other.frees &&
  32         alloc_size - free_size == other.alloc_size - other.free_size;
  33   }
  34
  35   int32 allocs;      // Number of allocation calls.
  36   int32 frees;       // Number of free calls.
  37   int64 alloc_size;  // Total size of all allocated objects so far.
  38   int64 free_size;   // Total size of all freed objects so far.
  39 };
  40
  41 // Allocation and deallocation statistics per each stack trace.
  42 struct HeapProfileBucket : public HeapProfileStats {
  43   // Longest stack trace we record.
  44   static const int kMaxStackDepth = 32;
  45
  46   uintptr_t hash;           // Hash value of the stack trace.
  47   int depth;                // Depth of stack trace.
  48   const void** stack;       // Stack trace.
  49   HeapProfileBucket* next;  // Next entry in hash-table.
  50 };
  51
  52 #endif  // HEAP_PROFILE_STATS_H_