Revert of [Tracing] Add allocation register for heap profiling

base/trace_event/memory_profiler_allocation_register.cc

Index: base/trace_event/memory_profiler_allocation_register.cc
diff --git a/base/trace_event/memory_profiler_allocation_register.cc b/base/trace_event/memory_profiler_allocation_register.cc
deleted file mode 100644
index 662e86fc0df7a6e2f09507b56ab6795b076d9332..0000000000000000000000000000000000000000
--- a/base/trace_event/memory_profiler_allocation_register.cc
+++ /dev/null
@@ -1,166 +0,0 @@
-// Copyright 2015 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.
-
-#include "base/trace_event/memory_profiler_allocation_register.h"
-
-namespace base {
-namespace trace_event {
-
-AllocationRegister::AllocationRegister()
-    // Reserve enough address space to store |kNumCells| entries if necessary,
-    // with a guard page after it to crash the program when attempting to store
-    // more entries.
-    : cells_(static_cast<Cell*>(AllocateVirtualMemory(kNumCells *
-                                                      sizeof(Cell)))),
-      buckets_(static_cast<CellIndex*>(
-          AllocateVirtualMemory(kNumBuckets * sizeof(CellIndex)))),
-
-      // The free list is empty. The first unused cell is cell 1, because index
-      // 0 is used as list terminator.
-      free_list_(0),
-      next_unused_cell_(1) {}
-
-AllocationRegister::~AllocationRegister() {
-  FreeVirtualMemory(buckets_, kNumBuckets * sizeof(CellIndex));
-  FreeVirtualMemory(cells_, kNumCells * sizeof(Cell));
-}
-
-void AllocationRegister::Insert(void* address,
-                                size_t size,
-                                AllocationContext context) {
-  DCHECK(address != nullptr);
-
-  CellIndex* idx_ptr = Lookup(address);
-
-  // If the index is 0, the address is not yet present, so insert it.
-  if (*idx_ptr == 0) {
-    *idx_ptr = GetFreeCell();
-
-    cells_[*idx_ptr].allocation.address = address;
-    cells_[*idx_ptr].next = 0;
-  }
-
-  cells_[*idx_ptr].allocation.size = size;
-  cells_[*idx_ptr].allocation.context = context;
-}
-
-void AllocationRegister::Remove(void* address) {
-  // Get a pointer to the index of the cell that stores |address|. The index can
-  // be an element of |buckets_| or the |next| member of a cell.
-  CellIndex* idx_ptr = Lookup(address);
-  CellIndex freed_idx = *idx_ptr;
-
-  // If the index is 0, the address was not there in the first place.
-  if (freed_idx == 0)
-    return;
-
-  // The cell at the index is now free, remove it from the linked list for
-  // |Hash(address)|.
-  Cell* freed_cell = &cells_[freed_idx];
-  *idx_ptr = freed_cell->next;
-
-  // Put the free cell at the front of the free list.
-  freed_cell->next = free_list_;
-  free_list_ = freed_idx;
-
-  // Reset the address, so that on iteration the free cell is ignored.
-  freed_cell->allocation.address = nullptr;
-}
-
-AllocationRegister::ConstIterator AllocationRegister::begin() const {
-  // Initialize the iterator's index to 0. Cell 0 never stores an entry.
-  ConstIterator iterator(*this, 0);
-  // Incrementing will advance the iterator to the first used cell.
-  ++iterator;
-  return iterator;
-}
-
-AllocationRegister::ConstIterator AllocationRegister::end() const {
-  // Cell |next_unused_cell_ - 1| is the last cell that could contain an entry,
-  // so index |next_unused_cell_| is an iterator past the last element, in line
-  // with the STL iterator conventions.
-  return ConstIterator(*this, next_unused_cell_);
-}
-
-AllocationRegister::ConstIterator::ConstIterator(
-    const AllocationRegister& alloc_register,
-    CellIndex index)
-    : register_(alloc_register), index_(index) {}
-
-void AllocationRegister::ConstIterator::operator++() {
-  // Find the next cell with a non-null address until all cells that could
-  // possibly be used have been iterated. A null address indicates a free cell.
-  do {
-    index_++;
-  } while (index_ < register_.next_unused_cell_ &&
-           register_.cells_[index_].allocation.address == nullptr);
-}
-
-bool AllocationRegister::ConstIterator::operator!=(
-    const ConstIterator& other) const {
-  return index_ != other.index_;
-}
-
-const AllocationRegister::Allocation& AllocationRegister::ConstIterator::
-operator*() const {
-  return register_.cells_[index_].allocation;
-}
-
-AllocationRegister::CellIndex* AllocationRegister::Lookup(void* address) {
-  // The list head is in |buckets_| at the hash offset.
-  CellIndex* idx_ptr = &buckets_[Hash(address)];
-
-  // Chase down the list until the cell that holds |key| is found,
-  // or until the list ends.
-  while (*idx_ptr != 0 && cells_[*idx_ptr].allocation.address != address)
-    idx_ptr = &cells_[*idx_ptr].next;
-
-  return idx_ptr;
-}
-
-AllocationRegister::CellIndex AllocationRegister::GetFreeCell() {
-  // First try to re-use a cell from the freelist.
-  if (free_list_) {
-    CellIndex idx = free_list_;
-    free_list_ = cells_[idx].next;
-    return idx;
-  }
-
-  // Otherwise pick the next cell that has not been touched before.
-  CellIndex idx = next_unused_cell_;
-  next_unused_cell_++;
-
-  // If the hash table has too little capacity (when too little address space
-  // was reserved for |cells_|), |next_unused_cell_| can be an index outside of
-  // the allocated storage. A guard page is allocated there to crash the
-  // program in that case. There are alternative solutions:
-  // - Deal with it, increase capacity by reallocating |cells_|.
-  // - Refuse to insert and let the caller deal with it.
-  // Because free cells are re-used before accessing fresh cells with a higher
-  // index, and because reserving address space without touching it is cheap,
-  // the simplest solution is to just allocate a humongous chunk of address
-  // space.
-
-  DCHECK_LT(next_unused_cell_, kNumCells + 1);
-
-  return idx;
-}
-
-// static
-uint32_t AllocationRegister::Hash(void* address) {
-  // The multiplicative hashing scheme from [Knuth 1998]. The value of |a| has
-  // been chosen carefully based on measurements with real-word data (addresses
-  // recorded from a Chrome trace run). It is the first prime after 2^17. For
-  // |shift|, 13, 14 and 15 yield good results. These values are tuned to 2^18
-  // buckets. Microbenchmarks show that this simple scheme outperforms fancy
-  // hashes like Murmur3 by 20 to 40 percent.
-  const uintptr_t key = reinterpret_cast<uintptr_t>(address);
-  const uintptr_t a = 131101;
-  const uintptr_t shift = 14;
-  const uintptr_t h = (key * a) >> shift;
-  return static_cast<uint32_t>(h) & kNumBucketsMask;
-}
-
-}  // namespace trace_event
-}  // namespace base