[heap] Keep array buffer bytes stable during sweeping

Introduce separate counters for young and old array buffer bytes. They
are used to keep the counter stable during sweeping when the array
buffer lists are moved to the concurrent thread for sweeping.

Bug: v8:10064
Change-Id: I0f11a634341873b4d21759c284c55beb26fe30a5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2045511
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66204}

src/heap/array-buffer-sweeper.cc

@@ -118,6 +118,10 @@ void ArrayBufferSweeper::RequestSweepFull() {
   RequestSweep(SweepingScope::Full);
 }
 
+size_t ArrayBufferSweeper::YoungBytes() { return young_bytes_; }
+
+size_t ArrayBufferSweeper::OldBytes() { return old_bytes_; }
+
 void ArrayBufferSweeper::RequestSweep(SweepingScope scope) {
   DCHECK(!sweeping_in_progress_);
 
@@ -166,6 +170,8 @@ void ArrayBufferSweeper::Merge() {
   CHECK_EQ(job_.state, SweepingState::Swept);
   young_.Append(&job_.young);
   old_.Append(&job_.old);
+  young_bytes_ = young_.Bytes();
+  old_bytes_ = old_.Bytes();
   job_.state = SweepingState::Uninitialized;
 }
 
@@ -173,6 +179,7 @@ void ArrayBufferSweeper::ReleaseAll() {
   EnsureFinished();
   ReleaseAll(&old_);
   ReleaseAll(&young_);
+  old_bytes_ = young_bytes_ = 0;
 }
 
 void ArrayBufferSweeper::ReleaseAll(ArrayBufferList* list) {
@@ -189,13 +196,16 @@ void ArrayBufferSweeper::ReleaseAll(ArrayBufferList* list) {
 
 void ArrayBufferSweeper::Append(JSArrayBuffer object,
                                 ArrayBufferExtension* extension) {
+  size_t bytes = extension->accounting_length();
+
   if (Heap::InYoungGeneration(object)) {
     young_.Append(extension);
+    young_bytes_ += bytes;
   } else {
     old_.Append(extension);
+    old_bytes_ += bytes;
   }
 
-  size_t bytes = extension->accounting_length();
   IncrementExternalMemoryCounters(bytes);
 }
 

src/heap/array-buffer-sweeper.h

@@ -48,7 +48,10 @@ struct ArrayBufferList {
 class ArrayBufferSweeper {
  public:
   explicit ArrayBufferSweeper(Heap* heap)
-      : heap_(heap), sweeping_in_progress_(false) {}
+      : heap_(heap),
+        sweeping_in_progress_(false),
+        young_bytes_(0),
+        old_bytes_(0) {}
   ~ArrayBufferSweeper() { ReleaseAll(); }
 
   void EnsureFinished();
@@ -60,6 +63,9 @@ class ArrayBufferSweeper {
   ArrayBufferList young() { return young_; }
   ArrayBufferList old() { return old_; }
 
+  size_t YoungBytes();
+  size_t OldBytes();
+
  private:
   enum class SweepingScope { Young, Full };
 
@@ -105,6 +111,9 @@ class ArrayBufferSweeper {
 
   ArrayBufferList young_;
   ArrayBufferList old_;
+
+  size_t young_bytes_;
+  size_t old_bytes_;
 };
 
 }  // namespace internal

src/heap/heap.cc

@@ -5999,12 +5999,12 @@ void Heap::RememberUnmappedPage(Address page, bool compacted) {
 
 size_t Heap::YoungArrayBufferBytes() {
   DCHECK(V8_ARRAY_BUFFER_EXTENSION_BOOL);
-  return array_buffer_sweeper()->young().Bytes();
+  return array_buffer_sweeper()->YoungBytes();
 }
 
 size_t Heap::OldArrayBufferBytes() {
   DCHECK(V8_ARRAY_BUFFER_EXTENSION_BOOL);
-  return array_buffer_sweeper()->old().Bytes();
+  return array_buffer_sweeper()->OldBytes();
 }
 
 void Heap::RegisterStrongRoots(FullObjectSlot start, FullObjectSlot end) {

test/cctest/heap/test-array-buffer-tracker.cc

@@ -509,6 +509,7 @@ TEST(ArrayBuffer_ExternalBackingStoreSizeIncreases) {
 }
 
 TEST(ArrayBuffer_ExternalBackingStoreSizeDecreases) {
+  FLAG_concurrent_array_buffer_sweeping = false;
   CcTest::InitializeVM();
   LocalContext env;
   v8::Isolate* isolate = env->GetIsolate();