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// 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
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.