[heap] Minor MC: Add marking

src/heap/mark-compact.cc

 // Copyright 2012 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/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 304 matching lines @@
   }
 #endif
 
   StartSweepSpaces();
 
   EvacuateNewSpaceAndCandidates();
 
   Finish();
 }
 
-
 #ifdef VERIFY_HEAP
 void MarkCompactCollector::VerifyMarkbitsAreClean(PagedSpace* space) {
   for (Page* p : *space) {
     CHECK(p->markbits()->IsClean());
     CHECK_EQ(0, p->LiveBytes());
   }
 }
 
 
 void MarkCompactCollector::VerifyMarkbitsAreClean(NewSpace* space) {
@@ skipping 11 matching lines @@
   VerifyMarkbitsAreClean(heap_->new_space());
 
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(obj);
     CHECK(Marking::IsWhite(mark_bit));
     CHECK_EQ(0, Page::FromAddress(obj->address())->LiveBytes());
   }
 }
 
+MarkCompactCollector::YounGenerationMarkingVerificationState
+MarkCompactCollector::MarkYoungGenerationForVerification() {
+  YounGenerationMarkingVerificationState state;
+  state = GetObjectsInToSpace();
+  MarkLiveObjectsInYoungGeneration();
+  GlobalHandles::NewSpaceNodeStates new_space_node_states =
+      isolate()->global_handles()->GetNewSpaceNodeStates();
+  MarkLiveObjectsInYoungGeneration();
+  isolate()->global_handles()->RestoreNewSpaceNodeStates(new_space_node_states);
+  return state;
+}
+
+std::vector<HeapObject*> MarkCompactCollector::GetObjectsInToSpace() {
+  std::vector<HeapObject*> objects;
+  const Address top = heap()->new_space()->top();
+  const Address space_start = heap()->new_space()->bottom();
+  const Address space_end = heap()->new_space()->top();
+  for (Page* page : NewSpacePageRange(space_start, space_end)) {
+    HeapObject* object = HeapObject::FromAddress(page->area_start());
+    while (object->address() < page->area_end() &&
+           (!page->ContainsLimit(top) || (object->address() < top))) {
+      if (!object->IsFiller()) {
+        objects.push_back(object);
+      }
+      object = HeapObject::FromAddress(object->address() + object->Size());
+    }
+  }
+  return objects;
+}
+
+void MarkCompactCollector::VerifyYoungGenerationMarkbitsUsingForwardingPointers(
+    const YounGenerationMarkingVerificationState& state) {
+  for (HeapObject* object : state) {
+    const MapWord map_word = object->map_word();
+    const bool is_black = Marking::IsBlack(ObjectMarking::MarkBitFrom(object));
+    if (map_word.IsForwardingAddress()) {
+      CHECK(is_black);
+    } else {
+      CHECK(!is_black);
+    }
+  }
+
+  for (Page* p : NewSpacePageRange(heap()->new_space()->FromSpaceStart(),
+                                   heap()->new_space()->FromSpaceEnd())) {
+    p->ClearLiveness();
+  }
+}
 
 void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() {
   HeapObjectIterator code_iterator(heap()->code_space());
   for (HeapObject* obj = code_iterator.Next(); obj != NULL;
        obj = code_iterator.Next()) {
     Code* code = Code::cast(obj);
     if (!code->is_optimized_code()) continue;
     if (WillBeDeoptimized(code)) continue;
     code->VerifyEmbeddedObjectsDependency();
   }
@@ skipping 709 matching lines @@
   JSFunction* candidate = jsfunction_candidates_head_;
   while (candidate != NULL) {
     if (heap->InFromSpace(candidate)) {
       v->VisitPointer(reinterpret_cast<Object**>(slot));
     }
     candidate = GetNextCandidate(*slot);
     slot = GetNextCandidateSlot(*slot);
   }
 }
 
+class StaticYoungGenerationMarkingVisitor
+    : public StaticNewSpaceVisitor<StaticYoungGenerationMarkingVisitor> {
+ public:
+  static void Initialize(Heap* heap) {
+    StaticNewSpaceVisitor<StaticYoungGenerationMarkingVisitor>::Initialize();
+  }
+
+  inline static void VisitPointer(Heap* heap, HeapObject* object, Object** p) {
+    Object* target = *p;
+    if (heap->InNewSpace(target)) {
+      if (MarkRecursively(heap, HeapObject::cast(target))) return;
+      PushOnMarkingDeque(heap, target);
+    }
+  }
+
+ protected:
+  inline static void PushOnMarkingDeque(Heap* heap, Object* obj) {
+    HeapObject* object = HeapObject::cast(obj);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
+    heap->mark_compact_collector()->MarkObject(object, mark_bit);
+  }
+
+  inline static bool MarkRecursively(Heap* heap, HeapObject* object) {
+    StackLimitCheck check(heap->isolate());
+    if (check.HasOverflowed()) return false;
+
+    MarkBit mark = ObjectMarking::MarkBitFrom(object);
+    if (Marking::IsBlackOrGrey(mark)) return true;
+    heap->mark_compact_collector()->SetMark(object, mark);
+    IterateBody(object->map(), object);
+    return true;
+  }
+};
 
 class MarkCompactMarkingVisitor
     : public StaticMarkingVisitor<MarkCompactMarkingVisitor> {
  public:
   static void Initialize();
 
   INLINE(static void VisitPointer(Heap* heap, HeapObject* object, Object** p)) {
     MarkObjectByPointer(heap->mark_compact_collector(), object, p);
   }
 
@@ skipping 233 matching lines @@
   // Iterate the archived stacks in all threads to check if
   // the code is referenced.
   CodeMarkingVisitor code_marking_visitor(this);
   heap()->isolate()->thread_manager()->IterateArchivedThreads(
       &code_marking_visitor);
 
   SharedFunctionInfoMarkingVisitor visitor(this);
   heap()->isolate()->compilation_cache()->IterateFunctions(&visitor);
   heap()->isolate()->handle_scope_implementer()->Iterate(&visitor);
 
-  ProcessMarkingDeque();
+  ProcessMarkingDeque<MarkCompactMode::FULL>();
 }
 
 
 // Visitor class for marking heap roots.
+template <MarkCompactMode mode>
 class RootMarkingVisitor : public ObjectVisitor {
  public:
   explicit RootMarkingVisitor(Heap* heap)
       : collector_(heap->mark_compact_collector()) {}
 
   void VisitPointer(Object** p) override { MarkObjectByPointer(p); }
 
   void VisitPointers(Object** start, Object** end) override {
     for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
   }
 
   // Skip the weak next code link in a code object, which is visited in
   // ProcessTopOptimizedFrame.
   void VisitNextCodeLink(Object** p) override {}
 
  private:
   void MarkObjectByPointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     HeapObject* object = HeapObject::cast(*p);
 
+    if (mode == MarkCompactMode::YOUNG_GENERATION &&
+        !collector_->heap()->InNewSpace(object))
+      return;
+
     MarkBit mark_bit = ObjectMarking::MarkBitFrom(object);
     if (Marking::IsBlackOrGrey(mark_bit)) return;
 
     Map* map = object->map();
     // Mark the object.
     collector_->SetMark(object, mark_bit);
 
-    // Mark the map pointer and body, and push them on the marking stack.
-    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
-    collector_->MarkObject(map, map_mark);
-    MarkCompactMarkingVisitor::IterateBody(map, object);
+    switch (mode) {
+      case MarkCompactMode::FULL: {
+        // Mark the map pointer and body, and push them on the marking stack.
+        MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
+        collector_->MarkObject(map, map_mark);
+        MarkCompactMarkingVisitor::IterateBody(map, object);
+      } break;
+      case MarkCompactMode::YOUNG_GENERATION:
+        StaticYoungGenerationMarkingVisitor::IterateBody(map, object);
+        break;
+    }
 
     // Mark all the objects reachable from the map and body.  May leave
     // overflowed objects in the heap.
-    collector_->EmptyMarkingDeque();
+    collector_->EmptyMarkingDeque<mode>();
   }
 
   MarkCompactCollector* collector_;
 };
 
 
 // Helper class for pruning the string table.
 template <bool finalize_external_strings, bool record_slots>
 class StringTableCleaner : public ObjectVisitor {
  public:
@@ skipping 549 matching lines @@
 
 bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap,
                                                         Object** p) {
   Object* o = *p;
   DCHECK(o->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(o);
   MarkBit mark = ObjectMarking::MarkBitFrom(heap_object);
   return Marking::IsWhite(mark);
 }
 
-
-void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) {
+void MarkCompactCollector::MarkStringTable(
+    RootMarkingVisitor<MarkCompactMode::FULL>* visitor) {
   StringTable* string_table = heap()->string_table();
   // Mark the string table itself.
   MarkBit string_table_mark = ObjectMarking::MarkBitFrom(string_table);
   if (Marking::IsWhite(string_table_mark)) {
     // String table could have already been marked by visiting the handles list.
     SetMark(string_table, string_table_mark);
   }
   // Explicitly mark the prefix.
   string_table->IteratePrefix(visitor);
-  ProcessMarkingDeque();
+  ProcessMarkingDeque<MarkCompactMode::FULL>();
 }
 
 
 void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) {
   MarkBit mark_bit = ObjectMarking::MarkBitFrom(site);
   SetMark(site, mark_bit);
 }
 
-
-void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) {
+void MarkCompactCollector::MarkRoots(
+    RootMarkingVisitor<MarkCompactMode::FULL>* visitor) {
   // Mark the heap roots including global variables, stack variables,
   // etc., and all objects reachable from them.
   heap()->IterateStrongRoots(visitor, VISIT_ONLY_STRONG);
 
   // Handle the string table specially.
   MarkStringTable(visitor);
 
   // There may be overflowed objects in the heap.  Visit them now.
   while (marking_deque()->overflowed()) {
-    RefillMarkingDeque();
-    EmptyMarkingDeque();
+    RefillMarkingDeque<MarkCompactMode::FULL>();
+    EmptyMarkingDeque<MarkCompactMode::FULL>();
   }
 }
 
 
 void MarkCompactCollector::MarkImplicitRefGroups(
     MarkObjectFunction mark_object) {
   List<ImplicitRefGroup*>* ref_groups =
       isolate()->global_handles()->implicit_ref_groups();
 
   int last = 0;
@@ skipping 19 matching lines @@
     delete entry;
   }
   ref_groups->Rewind(last);
 }
 
 
 // Mark all objects reachable from the objects on the marking stack.
 // Before: the marking stack contains zero or more heap object pointers.
 // After: the marking stack is empty, and all objects reachable from the
 // marking stack have been marked, or are overflowed in the heap.
+template <MarkCompactMode mode>
 void MarkCompactCollector::EmptyMarkingDeque() {
   while (!marking_deque()->IsEmpty()) {
     HeapObject* object = marking_deque()->Pop();
 
     DCHECK(!object->IsFiller());
     DCHECK(object->IsHeapObject());
     DCHECK(heap()->Contains(object));
     DCHECK(!Marking::IsWhite(ObjectMarking::MarkBitFrom(object)));
 
     Map* map = object->map();
-    MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
-    MarkObject(map, map_mark);
-
-    MarkCompactMarkingVisitor::IterateBody(map, object);
+    switch (mode) {
+      case MarkCompactMode::FULL: {
+        MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
+        MarkObject(map, map_mark);
+        MarkCompactMarkingVisitor::IterateBody(map, object);
+      } break;
+      case MarkCompactMode::YOUNG_GENERATION: {
+        DCHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
+        StaticYoungGenerationMarkingVisitor::IterateBody(map, object);
+      } break;
+    }
   }
 }
 
 
 // Sweep the heap for overflowed objects, clear their overflow bits, and
 // push them on the marking stack.  Stop early if the marking stack fills
 // before sweeping completes.  If sweeping completes, there are no remaining
 // overflowed objects in the heap so the overflow flag on the markings stack
 // is cleared.
+template <MarkCompactMode mode>
 void MarkCompactCollector::RefillMarkingDeque() {
   isolate()->CountUsage(v8::Isolate::UseCounterFeature::kMarkDequeOverflow);
   DCHECK(marking_deque()->overflowed());
 
   DiscoverGreyObjectsInNewSpace();
   if (marking_deque()->IsFull()) return;
 
-  DiscoverGreyObjectsInSpace(heap()->old_space());
-  if (marking_deque()->IsFull()) return;
-
-  DiscoverGreyObjectsInSpace(heap()->code_space());
-  if (marking_deque()->IsFull()) return;
-
-  DiscoverGreyObjectsInSpace(heap()->map_space());
-  if (marking_deque()->IsFull()) return;
-
-  LargeObjectIterator lo_it(heap()->lo_space());
-  DiscoverGreyObjectsWithIterator(&lo_it);
-  if (marking_deque()->IsFull()) return;
+  if (mode == MarkCompactMode::FULL) {
+    DiscoverGreyObjectsInSpace(heap()->old_space());
+    if (marking_deque()->IsFull()) return;
+    DiscoverGreyObjectsInSpace(heap()->code_space());
+    if (marking_deque()->IsFull()) return;
+    DiscoverGreyObjectsInSpace(heap()->map_space());
+    if (marking_deque()->IsFull()) return;
+    LargeObjectIterator lo_it(heap()->lo_space());
+    DiscoverGreyObjectsWithIterator(&lo_it);
+    if (marking_deque()->IsFull()) return;
+  }
 
   marking_deque()->ClearOverflowed();
 }
 
 
 // Mark all objects reachable (transitively) from objects on the marking
 // stack.  Before: the marking stack contains zero or more heap object
 // pointers.  After: the marking stack is empty and there are no overflowed
 // objects in the heap.
+template <MarkCompactMode mode>
 void MarkCompactCollector::ProcessMarkingDeque() {
-  EmptyMarkingDeque();
+  EmptyMarkingDeque<mode>();
   while (marking_deque()->overflowed()) {
-    RefillMarkingDeque();
-    EmptyMarkingDeque();
+    RefillMarkingDeque<mode>();
+    EmptyMarkingDeque<mode>();
   }
+  DCHECK(marking_deque()->IsEmpty());
 }
 
 // Mark all objects reachable (transitively) from objects on the marking
 // stack including references only considered in the atomic marking pause.
 void MarkCompactCollector::ProcessEphemeralMarking(
     ObjectVisitor* visitor, bool only_process_harmony_weak_collections) {
   DCHECK(marking_deque()->IsEmpty() && !marking_deque()->overflowed());
   bool work_to_do = true;
   while (work_to_do) {
     if (heap_->UsingEmbedderHeapTracer()) {
       TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WRAPPER_TRACING);
       heap_->RegisterWrappersWithEmbedderHeapTracer();
       heap_->embedder_heap_tracer()->AdvanceTracing(
           0, EmbedderHeapTracer::AdvanceTracingActions(
                  EmbedderHeapTracer::ForceCompletionAction::FORCE_COMPLETION));
     }
     if (!only_process_harmony_weak_collections) {
       TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_OBJECT_GROUPING);
       isolate()->global_handles()->IterateObjectGroups(
           visitor, &IsUnmarkedHeapObjectWithHeap);
       MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject);
     }
     ProcessWeakCollections();
     work_to_do = !marking_deque()->IsEmpty();
-    ProcessMarkingDeque();
+    ProcessMarkingDeque<MarkCompactMode::FULL>();
   }
 }
 
 void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
   for (StackFrameIterator it(isolate(), isolate()->thread_local_top());
        !it.done(); it.Advance()) {
     if (it.frame()->type() == StackFrame::JAVA_SCRIPT) {
       return;
     }
     if (it.frame()->type() == StackFrame::OPTIMIZED) {
       Code* code = it.frame()->LookupCode();
       if (!code->CanDeoptAt(it.frame()->pc())) {
         Code::BodyDescriptor::IterateBody(code, visitor);
       }
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
       return;
     }
   }
 }
 
 void MarkingDeque::SetUp() {
   backing_store_ = new base::VirtualMemory(kMaxSize);
   backing_store_committed_size_ = 0;
   if (backing_store_ == nullptr) {
     V8::FatalProcessOutOfMemory("MarkingDeque::SetUp");
@@ skipping 17 matching lines @@
   size_t size = FLAG_force_marking_deque_overflows
                     ? 64 * kPointerSize
                     : backing_store_committed_size_;
   DCHECK(
       base::bits::IsPowerOfTwo32(static_cast<uint32_t>(size / kPointerSize)));
   mask_ = static_cast<int>((size / kPointerSize) - 1);
   top_ = bottom_ = 0;
   overflowed_ = false;
 }
 
-void MarkingDeque::StopUsing() {
+void MarkingDeque::StopUsing(UncommitMode mode) {

[Hannes Payer (out of office), 2016/11/18 07:33:02]

Based on the recent latency numbers of uncommit, we should always do that
concurrently.

[Michael Lippautz, 2016/11/18 09:46:19]

Yes, obviously. Let's leave this for later though as I don't want to add
concurrency optimizations while still trying to get correctness.

[Hannes Payer (out of office), 2016/11/18 10:07:11]

As discussed offline. I would trust the concurrent uncommit implementation and
would just use it for simplicity.

[Michael Lippautz, 2016/11/18 11:33:32]

Done.

   base::LockGuard<base::Mutex> guard(&mutex_);
+  if (!in_use_) return;
   DCHECK(IsEmpty());
   DCHECK(!overflowed_);
   top_ = bottom_ = mask_ = 0;
   in_use_ = false;
-  if (FLAG_concurrent_sweeping) {
+  if (FLAG_concurrent_sweeping && (mode == CONCURRENT)) {
     StartUncommitTask();
   } else {
     Uncommit();
   }
 }
 
 void MarkingDeque::Clear() {
   DCHECK(in_use_);
   top_ = bottom_ = 0;
   overflowed_ = false;
 }
 
 void MarkingDeque::Uncommit() {
   DCHECK(!in_use_);
+  // A call forcing immediate uncommitting could've already freed the backing
+  // store, indicated its size being zero.
+  if (backing_store_committed_size_ == 0) return;
   bool success = backing_store_->Uncommit(backing_store_->address(),
                                           backing_store_committed_size_);
   backing_store_committed_size_ = 0;
   CHECK(success);
 }
 
 void MarkingDeque::EnsureCommitted() {
   DCHECK(in_use_);
   if (backing_store_committed_size_ > 0) return;
 
@@ skipping 74 matching lines @@
     }
     if (FLAG_trace_gc_object_stats) {
       heap()->live_object_stats_->PrintJSON("live");
       heap()->dead_object_stats_->PrintJSON("dead");
     }
     heap()->live_object_stats_->CheckpointObjectStats();
     heap()->dead_object_stats_->ClearObjectStats();
   }
 }
 
+SlotCallbackResult MarkCompactCollector::CheckAndMarkObject(
+    Heap* heap, Address slot_address) {
+  Object* object = *reinterpret_cast<Object**>(slot_address);
+  if (heap->InNewSpace(object)) {
+    // Marking happens before flipping the young generation, so the object
+    // has to be in ToSpace.
+    DCHECK(heap->InToSpace(object));
+    HeapObject* heap_object = reinterpret_cast<HeapObject*>(object);
+    MarkBit mark_bit = ObjectMarking::MarkBitFrom(heap_object);
+    if (Marking::IsBlackOrGrey(mark_bit)) {
+      return KEEP_SLOT;
+    }
+    heap->mark_compact_collector()->SetMark(heap_object, mark_bit);
+    StaticYoungGenerationMarkingVisitor::IterateBody(heap_object->map(),
+                                                     heap_object);
+    return KEEP_SLOT;
+  }
+  return REMOVE_SLOT;
+}
+
+static bool IsUnmarkedObject(Heap* heap, Object** p) {
+  DCHECK_IMPLIES(heap->InNewSpace(*p), heap->InToSpace(*p));
+  return heap->InNewSpace(*p) &&
+         !Marking::IsBlack(ObjectMarking::MarkBitFrom(HeapObject::cast(*p)));
+}
+
+void MarkCompactCollector::MarkLiveObjectsInYoungGeneration() {
+  TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK);
+
+  PostponeInterruptsScope postpone(isolate());
+
+  StaticYoungGenerationMarkingVisitor::Initialize(heap());
+  RootMarkingVisitor<MarkCompactMode::YOUNG_GENERATION> root_visitor(heap());
+
+  marking_deque()->StartUsing();
+
+  isolate()->global_handles()->IdentifyWeakUnmodifiedObjects(
+      &Heap::IsUnmodifiedHeapObject);
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_ROOTS);
+    heap()->IterateRoots(&root_visitor, VISIT_ALL_IN_SCAVENGE);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(),
+             GCTracer::Scope::MINOR_MC_MARK_OLD_TO_NEW_POINTERS);
+    RememberedSet<OLD_TO_NEW>::Iterate(heap(), [this](Address addr) {
+      return CheckAndMarkObject(heap(), addr);
+    });
+    RememberedSet<OLD_TO_NEW>::IterateTyped(
+        heap(), [this](SlotType type, Address host_addr, Address addr) {
+          return UpdateTypedSlotHelper::UpdateTypedSlot(
+              isolate(), type, addr, [this](Object** addr) {
+                return CheckAndMarkObject(heap(),
+                                          reinterpret_cast<Address>(addr));
+              });
+        });
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_WEAK);
+    heap()->VisitEncounteredWeakCollections(&root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  if (is_code_flushing_enabled()) {
+    TRACE_GC(heap()->tracer(),
+             GCTracer::Scope::MINOR_MC_MARK_CODE_FLUSH_CANDIDATES);
+    code_flusher()->IteratePointersToFromSpace(&root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  {
+    TRACE_GC(heap()->tracer(), GCTracer::Scope::MINOR_MC_MARK_GLOBAL_HANDLES);
+    isolate()->global_handles()->MarkNewSpaceWeakUnmodifiedObjectsPending(
+        &IsUnmarkedObject);
+    isolate()
+        ->global_handles()
+        ->IterateNewSpaceWeakUnmodifiedRoots<
+            GlobalHandles::DONT_HANDLE_PHANTOM_NODES>(&root_visitor);
+    ProcessMarkingDeque<MarkCompactMode::YOUNG_GENERATION>();
+  }
+
+  marking_deque()->StopUsing(MarkingDeque::SEQUENTIAL);
+}
+
 void MarkCompactCollector::MarkLiveObjects() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK);
   // The recursive GC marker detects when it is nearing stack overflow,
   // and switches to a different marking system.  JS interrupts interfere
   // with the C stack limit check.
   PostponeInterruptsScope postpone(isolate());
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_FINISH_INCREMENTAL);
     IncrementalMarking* incremental_marking = heap_->incremental_marking();
     if (was_marked_incrementally_) {
       incremental_marking->Finalize();
     } else {
       CHECK(incremental_marking->IsStopped());
     }
   }
 
 #ifdef DEBUG
   DCHECK(state_ == PREPARE_GC);
   state_ = MARK_LIVE_OBJECTS;
 #endif
 
   marking_deque()->StartUsing();
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_PREPARE_CODE_FLUSH);
     PrepareForCodeFlushing();
   }
 
-  RootMarkingVisitor root_visitor(heap());
+  RootMarkingVisitor<MarkCompactMode::FULL> root_visitor(heap());
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_ROOTS);
     MarkRoots(&root_visitor);
     ProcessTopOptimizedFrame(&root_visitor);
   }
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WEAK_CLOSURE);
 
@@ skipping 11 matching lines @@
     // immediately reclaimed. Instead, we have to mark them as pending and mark
     // objects reachable from them.
     //
     // First we identify nonlive weak handles and mark them as pending
     // destruction.
     {
       TRACE_GC(heap()->tracer(),
                GCTracer::Scope::MC_MARK_WEAK_CLOSURE_WEAK_HANDLES);
       heap()->isolate()->global_handles()->IdentifyWeakHandles(
           &IsUnmarkedHeapObject);
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
     }
     // Then we mark the objects.
 
     {
       TRACE_GC(heap()->tracer(),
                GCTracer::Scope::MC_MARK_WEAK_CLOSURE_WEAK_ROOTS);
       heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor);
-      ProcessMarkingDeque();
+      ProcessMarkingDeque<MarkCompactMode::FULL>();
     }
 
     // Repeat Harmony weak maps marking to mark unmarked objects reachable from
     // the weak roots we just marked as pending destruction.
     //
     // We only process harmony collections, as all object groups have been fully
     // processed and no weakly reachable node can discover new objects groups.
     {
       TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_MARK_WEAK_CLOSURE_HARMONY);
       ProcessEphemeralMarking(&root_visitor, true);
@@ skipping 1585 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8