[heap] Improve size profiling for ArrayBuffer tracking

src/heap/array-buffer-tracker.h

 // 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.
 
 #ifndef V8_HEAP_ARRAY_BUFFER_TRACKER_H_
 #define V8_HEAP_ARRAY_BUFFER_TRACKER_H_
 
 #include <unordered_map>
 
 #include "src/allocation.h"
+#include "src/base/atomic-utils.h"
 #include "src/base/platform/mutex.h"
 #include "src/globals.h"
 
 namespace v8 {
 namespace internal {
 
 class Heap;
 class JSArrayBuffer;
 class Page;
 
-class ArrayBufferTracker : public AllStatic {
+class ArrayBufferTracker {
  public:
   enum ProcessingMode {
     kUpdateForwardedRemoveOthers,
     kUpdateForwardedKeepOthers,
   };
 
+  // Returns whether a buffer is currently tracked.
+  static bool IsTracked(JSArrayBuffer* buffer);
+
+  explicit ArrayBufferTracker(Heap* heap)
+      : heap_(heap),
+        concurrently_freed_(0),
+        retained_from_new_space_(0),
+        retained_from_old_space_(0) {}
+
   // The following methods are used to track raw C++ pointers to externally
   // allocated memory used as backing store in live array buffers.
 
   // Register/unregister a new JSArrayBuffer |buffer| for tracking. Guards all
   // access to the tracker by taking the page lock for the corresponding page.
-  inline static void RegisterNew(Heap* heap, JSArrayBuffer* buffer);
-  inline static void Unregister(Heap* heap, JSArrayBuffer* buffer);
+  inline void RegisterNew(Heap* heap, JSArrayBuffer* buffer);
+  inline void Unregister(Heap* heap, JSArrayBuffer* buffer);
 
   // Frees all backing store pointers for dead JSArrayBuffers in new space.
   // Does not take any locks and can only be called during Scavenge.
-  static void FreeDeadInNewSpace(Heap* heap);
+  void FreeDeadInNewSpace(Heap* heap);
 
   // Frees all backing store pointers for dead JSArrayBuffer on a given page.
   // Requires marking information to be present. Requires the page lock to be
   // taken by the caller.
-  static void FreeDead(Page* page);
+  void FreeDead(Page* page);
 
   // Frees all remaining, live or dead, array buffers on a page. Only useful
   // during tear down.
-  static void FreeAll(Page* page);
+  void FreeAll(Page* page);
 
   // Processes all array buffers on a given page. |mode| specifies the action
   // to perform on the buffers. Returns whether the tracker is empty or not.
-  static bool ProcessBuffers(Page* page, ProcessingMode mode);
+  bool ProcessBuffers(Page* page, ProcessingMode mode);
 
-  // Returns whether a buffer is currently tracked.
-  static bool IsTracked(JSArrayBuffer* buffer);
+  void AccountForConcurrentlyFreedMemory();
+
+  size_t retained_from_new_space() {
+    return static_cast<size_t>(retained_from_new_space_.Value());
+  }
+
+  size_t retained_from_old_space() {
+    return static_cast<size_t>(retained_from_old_space_.Value());
+  }
+
+ private:
+  Heap* heap_;
+
+  base::AtomicNumber<intptr_t> concurrently_freed_;
+
+  // Number of bytes retained from new space.
+  base::AtomicNumber<intptr_t> retained_from_new_space_;
+  // Number of bytes retained from old space.
+  base::AtomicNumber<intptr_t> retained_from_old_space_;
 };
 
 // LocalArrayBufferTracker tracks internalized array buffers.
 //
 // Never use directly but instead always call through |ArrayBufferTracker|.
 class LocalArrayBufferTracker {
  public:
   typedef JSArrayBuffer* Key;
   typedef size_t Value;
 
   enum CallbackResult { kKeepEntry, kUpdateEntry, kRemoveEntry };
   enum FreeMode { kFreeDead, kFreeAll };
 
+  struct ProcessResult {
+    ProcessResult(size_t freed, size_t live, size_t promoted)
+        : freed(freed), live(live), promoted(promoted) {}
+
+    size_t freed;
+    size_t live;
+    size_t promoted;
+  };
+
   explicit LocalArrayBufferTracker(Heap* heap) : heap_(heap) {}
   ~LocalArrayBufferTracker();
 
   inline void Add(Key key, const Value& value);
   inline Value Remove(Key key);
 
-  // Frees up array buffers determined by |free_mode|.
+  // Frees up array buffers determined by |free_mode|. Returns statistics in
+  // ProcessResult.
   template <FreeMode free_mode>
-  void Free();
+  ProcessResult Free();
 
   // Processes buffers one by one. The CallbackResult of the callback decides
-  // what action to take on the buffer.
+  // what action to take on the buffer. Returns statistics in ProcessResult.
   //
   // Callback should be of type:
   //   CallbackResult fn(JSArrayBuffer* buffer, JSArrayBuffer** new_buffer);
   template <typename Callback>
-  void Process(Callback callback);
+  ProcessResult Process(Callback callback);
 
   bool IsEmpty() { return array_buffers_.empty(); }
 
   bool IsTracked(Key key) {
     return array_buffers_.find(key) != array_buffers_.end();
   }
 
  private:
   typedef std::unordered_map<Key, Value> TrackingData;
 
   Heap* heap_;
   TrackingData array_buffers_;
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_HEAP_ARRAY_BUFFER_TRACKER_H_