Reland "[heap] Optimize ArrayBuffer 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/array-buffer-tracker-inl.h"
 #include "src/heap/heap.h"
 
 namespace v8 {
 namespace internal {
 
 LocalArrayBufferTracker::~LocalArrayBufferTracker() {
   CHECK(array_buffers_.empty());
 }
 
 template <LocalArrayBufferTracker::FreeMode free_mode>
 void LocalArrayBufferTracker::Free() {
   size_t freed_memory = 0;
-  for (TrackingMap::iterator it = array_buffers_.begin();
+  for (TrackingData::iterator it = array_buffers_.begin();
        it != array_buffers_.end();) {
+    JSArrayBuffer* buffer = reinterpret_cast<JSArrayBuffer*>(*it);
     if ((free_mode == kFreeAll) ||
-        Marking::IsWhite(Marking::MarkBitFrom(it->first))) {
-      heap_->isolate()->array_buffer_allocator()->Free(it->second.first,
-                                                       it->second.second);
-      freed_memory += it->second.second;
+        Marking::IsWhite(Marking::MarkBitFrom(buffer))) {
+      const size_t len = NumberToSize(heap_->isolate(), buffer->byte_length());
+      heap_->isolate()->array_buffer_allocator()->Free(buffer->backing_store(),
+                                                       len);
+      freed_memory += len;
       it = array_buffers_.erase(it);
     } else {
-      it++;
+      ++it;
     }
   }
   if (freed_memory > 0) {
     heap_->update_external_memory_concurrently_freed(
         static_cast<intptr_t>(freed_memory));
   }
 }
 
 template <typename Callback>
 void LocalArrayBufferTracker::Process(Callback callback) {
   JSArrayBuffer* new_buffer = nullptr;
   size_t freed_memory = 0;
-  for (TrackingMap::iterator it = array_buffers_.begin();
+  for (TrackingData::iterator it = array_buffers_.begin();
        it != array_buffers_.end();) {
-    const CallbackResult result = callback(it->first, &new_buffer);
+    const CallbackResult result = callback(*it, &new_buffer);
     if (result == kKeepEntry) {
-      it++;
+      ++it;
     } else if (result == kUpdateEntry) {
       DCHECK_NOT_NULL(new_buffer);
       Page* target_page = Page::FromAddress(new_buffer->address());
       // We need to lock the target page because we cannot guarantee
       // exclusive access to new space pages.
       if (target_page->InNewSpace()) target_page->mutex()->Lock();
       LocalArrayBufferTracker* tracker = target_page->local_tracker();
       if (tracker == nullptr) {
         target_page->AllocateLocalTracker();
         tracker = target_page->local_tracker();
       }
       DCHECK_NOT_NULL(tracker);
-      tracker->Add(new_buffer, it->second);
+      tracker->Add(new_buffer);
       if (target_page->InNewSpace()) target_page->mutex()->Unlock();
       it = array_buffers_.erase(it);
     } else if (result == kRemoveEntry) {
-      heap_->isolate()->array_buffer_allocator()->Free(it->second.first,
-                                                       it->second.second);
-      freed_memory += it->second.second;
+      const size_t len = NumberToSize(heap_->isolate(), (*it)->byte_length());
+      heap_->isolate()->array_buffer_allocator()->Free((*it)->backing_store(),
+                                                       len);
+      freed_memory += len;
       it = array_buffers_.erase(it);
     } else {
       UNREACHABLE();
     }
   }
   if (freed_memory > 0) {
     heap_->update_external_memory_concurrently_freed(
         static_cast<intptr_t>(freed_memory));
   }
 }
@@ skipping 52 matching lines @@
   {
     base::LockGuard<base::Mutex> guard(page->mutex());
     LocalArrayBufferTracker* tracker = page->local_tracker();
     if (tracker == nullptr) return false;
     return tracker->IsTracked(buffer);
   }
 }
 
 }  // namespace internal
 }  // namespace v8