Revert of Pool implementation for zone segments

src/zone/accounting-allocator.cc

 // Copyright 2016 the V8 project 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 "src/zone/accounting-allocator.h"
 
 #include <cstdlib>
 
 #if V8_LIBC_BIONIC
 #include <malloc.h>  // NOLINT
 #endif
 
 namespace v8 {
 namespace internal {
 
-AccountingAllocator::AccountingAllocator() : unused_segments_mutex_() {
-  memory_pressure_level_.SetValue(MemoryPressureLevel::kNone);
-  std::fill(unused_segments_heads_,
-            unused_segments_heads_ +
-                (1 + kMaxSegmentSizePower - kMinSegmentSizePower),
-            nullptr);
-  std::fill(
-      unused_segments_sizes,
-      unused_segments_sizes + (1 + kMaxSegmentSizePower - kMinSegmentSizePower),
-      0);
-}
-
-AccountingAllocator::~AccountingAllocator() { ClearPool(); }
-
-void AccountingAllocator::MemoryPressureNotification(
-    MemoryPressureLevel level) {
-  memory_pressure_level_.SetValue(level);
-
-  if (level != MemoryPressureLevel::kNone) {
-    ClearPool();
-  }
-}
-
-Segment* AccountingAllocator::GetSegment(size_t bytes) {
-  Segment* result = GetSegmentFromPool(bytes);
-  if (result == nullptr) {
-    result = AllocateSegment(bytes);
-  }
-
-  return result;
-}
-
 Segment* AccountingAllocator::AllocateSegment(size_t bytes) {
   void* memory = malloc(bytes);
   if (memory) {
     base::AtomicWord current =
         base::NoBarrier_AtomicIncrement(&current_memory_usage_, bytes);
     base::AtomicWord max = base::NoBarrier_Load(&max_memory_usage_);
     while (current > max) {
       max = base::NoBarrier_CompareAndSwap(&max_memory_usage_, max, current);
     }
   }
   return reinterpret_cast<Segment*>(memory);
 }
 
-void AccountingAllocator::ReturnSegment(Segment* segment) {
-  segment->ZapContents();
-  if (memory_pressure_level_.Value() != MemoryPressureLevel::kNone) {
-    FreeSegment(segment);
-  } else if (!AddSegmentToPool(segment)) {
-    FreeSegment(segment);
-  }
-}
-
 void AccountingAllocator::FreeSegment(Segment* memory) {
   base::NoBarrier_AtomicIncrement(
       &current_memory_usage_, -static_cast<base::AtomicWord>(memory->size()));
-  memory->ZapHeader();
   free(memory);
 }
 
 size_t AccountingAllocator::GetCurrentMemoryUsage() const {
   return base::NoBarrier_Load(&current_memory_usage_);
 }
 
 size_t AccountingAllocator::GetMaxMemoryUsage() const {
   return base::NoBarrier_Load(&max_memory_usage_);
 }
 
-Segment* AccountingAllocator::GetSegmentFromPool(size_t requested_size) {
-  if (requested_size > (1 << kMaxSegmentSizePower)) {
-    return nullptr;
-  }
-
-  uint8_t power = kMinSegmentSizePower;
-  while (requested_size > static_cast<size_t>(1 << power)) power++;
-
-  DCHECK_GE(power, kMinSegmentSizePower + 0);
-  power -= kMinSegmentSizePower;
-
-  Segment* segment;
-  {
-    base::LockGuard<base::Mutex> lock_guard(&unused_segments_mutex_);
-
-    segment = unused_segments_heads_[power];
-
-    if (segment != nullptr) {
-      unused_segments_heads_[power] = segment->next();
-      segment->set_next(nullptr);
-
-      unused_segments_sizes[power]--;
-      unused_segments_size_ -= segment->size();
-    }
-  }
-
-  if (segment) {
-    DCHECK_GE(segment->size(), requested_size);
-  }
-  return segment;
-}
-
-bool AccountingAllocator::AddSegmentToPool(Segment* segment) {
-  size_t size = segment->size();
-
-  if (size >= (1 << (kMaxSegmentSizePower + 1))) return false;
-
-  if (size < (1 << kMinSegmentSizePower)) return false;
-
-  uint8_t power = kMaxSegmentSizePower;
-
-  while (size < static_cast<size_t>(1 << power)) power--;
-
-  DCHECK_GE(power, kMinSegmentSizePower + 0);
-  power -= kMinSegmentSizePower;
-
-  {
-    base::LockGuard<base::Mutex> lock_guard(&unused_segments_mutex_);
-
-    if (unused_segments_sizes[power] >= kMaxSegmentsPerBucket) {
-      return false;
-    }
-
-    segment->set_next(unused_segments_heads_[power]);
-    unused_segments_heads_[power] = segment;
-    unused_segments_size_ += size;
-    unused_segments_sizes[power]++;
-  }
-
-  return true;
-}
-
-void AccountingAllocator::ClearPool() {
-  base::LockGuard<base::Mutex> lock_guard(&unused_segments_mutex_);
-
-  for (uint8_t power = 0; power <= kMaxSegmentSizePower - kMinSegmentSizePower;
-       power++) {
-    Segment* current = unused_segments_heads_[power];
-    while (current) {
-      Segment* next = current->next();
-      FreeSegment(current);
-      current = next;
-    }
-    unused_segments_heads_[power] = nullptr;
-  }
-}
-
 }  // namespace internal
 }  // namespace v8