[heap] Fine-grained JSArrayBuffer tracking

src/heap/array-buffer-tracker.cc

 // Copyright 2015 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/heap/array-buffer-tracker.h"
 #include "src/heap/heap.h"
 #include "src/isolate.h"
 #include "src/objects.h"
 #include "src/objects-inl.h"
 #include "src/v8.h"
 
 namespace v8 {
 namespace internal {
 
 ArrayBufferTracker::~ArrayBufferTracker() {
   Isolate* isolate = heap()->isolate();
   size_t freed_memory = 0;
-  for (auto& buffer : live_array_buffers_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
+  for (auto& buffer : live_old_gen_) {
+    isolate->array_buffer_allocator()->Free(buffer.second.first,
+                                            buffer.second.second);
+    freed_memory += buffer.second.second;
   }
-  for (auto& buffer : live_array_buffers_for_scavenge_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
+  for (auto& buffer : live_young_gen_) {
+    isolate->array_buffer_allocator()->Free(buffer.second.first,
+                                            buffer.second.second);
+    freed_memory += buffer.second.second;
   }
-  live_array_buffers_.clear();
-  live_array_buffers_for_scavenge_.clear();
-  not_yet_discovered_array_buffers_.clear();
-  not_yet_discovered_array_buffers_for_scavenge_.clear();
+  live_old_gen_.clear();
+  live_young_gen_.clear();
+  not_yet_discovered_old_gen_.clear();
+  not_yet_discovered_young_gen_.clear();
 
   if (freed_memory > 0) {
     heap()->update_amount_of_external_allocated_memory(
         -static_cast<int64_t>(freed_memory));
   }
 }
 
 
 void ArrayBufferTracker::RegisterNew(JSArrayBuffer* buffer) {
   void* data = buffer->backing_store();
   if (!data) return;
 
   bool in_new_space = heap()->InNewSpace(buffer);
   size_t length = NumberToSize(heap()->isolate(), buffer->byte_length());
   if (in_new_space) {
-    live_array_buffers_for_scavenge_[data] = length;
+    live_young_gen_[buffer->address()] = std::make_pair(data, length);
+    not_yet_discovered_young_gen_[buffer->address()] =
+        std::make_pair(data, length);
   } else {
-    live_array_buffers_[data] = length;
+    live_old_gen_[buffer->address()] = std::make_pair(data, length);
+    not_yet_discovered_old_gen_[buffer->address()] =
+        std::make_pair(data, length);
   }
 
   // We may go over the limit of externally allocated memory here. We call the
   // api function to trigger a GC in this case.
   reinterpret_cast<v8::Isolate*>(heap()->isolate())
       ->AdjustAmountOfExternalAllocatedMemory(length);
 }
 
 
 void ArrayBufferTracker::Unregister(JSArrayBuffer* buffer) {
   void* data = buffer->backing_store();
   if (!data) return;
 
   bool in_new_space = heap()->InNewSpace(buffer);
-  std::map<void*, size_t>* live_buffers =
-      in_new_space ? &live_array_buffers_for_scavenge_ : &live_array_buffers_;
-  std::map<void*, size_t>* not_yet_discovered_buffers =
-      in_new_space ? &not_yet_discovered_array_buffers_for_scavenge_
-                   : &not_yet_discovered_array_buffers_;
+  Key key = buffer->address();
+  TrackingMap* live_buffers = in_new_space ? &live_young_gen_ : &live_old_gen_;
+  TrackingMap* not_yet_discovered_buffers = in_new_space
+                                                ? &not_yet_discovered_young_gen_
+                                                : &not_yet_discovered_old_gen_;
 
-  DCHECK(live_buffers->count(data) > 0);
+  DCHECK(live_buffers->count(key) > 0);
 
-  size_t length = (*live_buffers)[data];
-  live_buffers->erase(data);
-  not_yet_discovered_buffers->erase(data);
+  size_t length = (*live_buffers)[key].second;
+  live_buffers->erase(key);
+  not_yet_discovered_buffers->erase(key);
 
   heap()->update_amount_of_external_allocated_memory(
       -static_cast<int64_t>(length));
 }
 
-
-void ArrayBufferTracker::MarkLive(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
-  void* data = buffer->backing_store();
-
-  // ArrayBuffer might be in the middle of being constructed.
-  if (data == heap()->undefined_value()) return;
-  if (heap()->InNewSpace(buffer)) {
-    not_yet_discovered_array_buffers_for_scavenge_.erase(data);
-  } else {
-    not_yet_discovered_array_buffers_.erase(data);
-  }
-}
-
-
 void ArrayBufferTracker::FreeDead(bool from_scavenge) {
   size_t freed_memory = 0;
   Isolate* isolate = heap()->isolate();
-  for (auto& buffer : not_yet_discovered_array_buffers_for_scavenge_) {
-    isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-    freed_memory += buffer.second;
-    live_array_buffers_for_scavenge_.erase(buffer.first);
+  for (auto& buffer : not_yet_discovered_young_gen_) {
+    isolate->array_buffer_allocator()->Free(buffer.second.first,
+                                            buffer.second.second);
+    freed_memory += buffer.second.second;
+    live_young_gen_.erase(buffer.first);
   }
 
   if (!from_scavenge) {
-    for (auto& buffer : not_yet_discovered_array_buffers_) {
-      isolate->array_buffer_allocator()->Free(buffer.first, buffer.second);
-      freed_memory += buffer.second;
-      live_array_buffers_.erase(buffer.first);
+    for (auto& buffer : not_yet_discovered_old_gen_) {
+      isolate->array_buffer_allocator()->Free(buffer.second.first,
+                                              buffer.second.second);
+      freed_memory += buffer.second.second;
+      live_old_gen_.erase(buffer.first);
     }
   }
 
-  not_yet_discovered_array_buffers_for_scavenge_ =
-      live_array_buffers_for_scavenge_;
-  if (!from_scavenge) not_yet_discovered_array_buffers_ = live_array_buffers_;
+  not_yet_discovered_young_gen_ = live_young_gen_;
+  if (!from_scavenge) not_yet_discovered_old_gen_ = live_old_gen_;
 
   // Do not call through the api as this code is triggered while doing a GC.
   heap()->update_amount_of_external_allocated_memory(
       -static_cast<int64_t>(freed_memory));
 }
 
+#define UPDATE_GUARD(buffer, data)               \
+  if (buffer->is_external()) return;             \
+  data = buffer->backing_store();                \
+  if (data == nullptr) return;                   \
+  if (data == heap()->undefined_value()) return; \
+  base::LockGuard<base::Mutex> guard(&mutex_);
 
-void ArrayBufferTracker::PrepareDiscoveryInNewSpace() {
-  not_yet_discovered_array_buffers_for_scavenge_ =
-      live_array_buffers_for_scavenge_;
+void ArrayBufferTracker::MarkLive(JSArrayBuffer* buffer) {
+  void* data = nullptr;
+  UPDATE_GUARD(buffer, data);
+
+  if (heap()->InNewSpace(buffer)) {
+    not_yet_discovered_young_gen_.erase(buffer->address());
+  } else {
+    not_yet_discovered_old_gen_.erase(buffer->address());
+  }
 }
 
+void ArrayBufferTracker::Promote(JSArrayBuffer* new_buffer,
+                                 JSArrayBuffer* old_buffer) {
+  void* data = nullptr;
+  UPDATE_GUARD(new_buffer, data);
 
-void ArrayBufferTracker::Promote(JSArrayBuffer* buffer) {
-  base::LockGuard<base::Mutex> guard(&mutex_);
+  Key new_key = new_buffer->address();
+  Key old_key = old_buffer->address();
+  DCHECK(live_young_gen_.count(old_key) > 0);
+  live_old_gen_[new_key] = live_young_gen_[old_key];
+  live_young_gen_.erase(old_key);
+  not_yet_discovered_young_gen_.erase(old_key);
+}
 
-  if (buffer->is_external()) return;
-  void* data = buffer->backing_store();
-  if (!data) return;
-  // ArrayBuffer might be in the middle of being constructed.
-  if (data == heap()->undefined_value()) return;
-  DCHECK(live_array_buffers_for_scavenge_.count(data) > 0);
-  live_array_buffers_[data] = live_array_buffers_for_scavenge_[data];
-  live_array_buffers_for_scavenge_.erase(data);
-  not_yet_discovered_array_buffers_for_scavenge_.erase(data);
+void ArrayBufferTracker::Compact(JSArrayBuffer* new_buffer,
+                                 JSArrayBuffer* old_buffer) {
+  void* data = nullptr;
+  UPDATE_GUARD(new_buffer, data);
+
+  Key new_key = new_buffer->address();
+  Key old_key = old_buffer->address();
+  DCHECK_NE(new_key, old_key);
+  DCHECK(live_old_gen_.count(old_key) > 0);
+  live_old_gen_[new_key] = live_old_gen_[old_key];
+  live_old_gen_.erase(old_key);
+  not_yet_discovered_old_gen_.erase(old_key);
+}
+
+void ArrayBufferTracker::SemiSpaceCopy(JSArrayBuffer* new_buffer,
+                                       JSArrayBuffer* old_buffer) {
+  void* data = nullptr;
+  UPDATE_GUARD(new_buffer, data);
+
+  Key new_key = new_buffer->address();
+  Key old_key = old_buffer->address();
+  DCHECK(live_young_gen_.count(old_key) > 0);
+  live_young_gen_[new_key] = live_young_gen_[old_key];
+  live_young_gen_.erase(old_key);
+  not_yet_discovered_young_gen_.erase(old_key);
+}
+
+#undef UPDATE_GUARD
+
+bool ArrayBufferTracker::IsTrackedInOldGenForTesting(JSArrayBuffer* buffer) {
+  return live_old_gen_.find(buffer->address()) != live_old_gen_.end();
+}
+
+bool ArrayBufferTracker::IsTrackedInYoungGenForTesting(JSArrayBuffer* buffer) {
+  return live_young_gen_.find(buffer->address()) != live_young_gen_.end();
 }
 
 }  // namespace internal
 }  // namespace v8