[heap] Adjust MarkingBarrier for MinorMC

This CL adjusts MarkingBarrier for MinorMC incremental marking.
The MarkingBarrier will be activated in a follow-up CL that schedules
MinorMC on a soft limit.

Bug: v8:13012
Change-Id: I525f6f158c2d55074d66f51925a1d8220cd4e9b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3787874
Commit-Queue: Leon Bettscheider <bettscheider@google.com>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82655}

src/heap/incremental-marking.cc

@@ -278,7 +278,8 @@ void IncrementalMarking::StartMarking() {
   is_marking_ = true;
   heap_->SetIsMarkingFlag(true);
 
-  MarkingBarrier::ActivateAll(heap(), is_compacting_);
+  MarkingBarrier::ActivateAll(heap(), is_compacting_,
+                              MarkingBarrierType::kMajor);
   GlobalHandles::EnableMarkingBarrier(heap()->isolate());
 
   heap_->isolate()->compilation_cache()->MarkCompactPrologue();

src/heap/incremental-marking.h

@@ -156,6 +156,8 @@ class V8_EXPORT_PRIVATE IncrementalMarking final {
   // Performs incremental marking step for unit tests.
   void AdvanceForTesting(double max_step_size_in_ms);
 
+  bool is_minor() const { return false; }
+
  private:
   class IncrementalMarkingRootMarkingVisitor;
 

src/heap/local-heap.cc

@@ -63,8 +63,10 @@ LocalHeap::LocalHeap(Heap* heap, ThreadKind kind,
     if (!is_main_thread()) {
       WriteBarrier::SetForThread(marking_barrier_.get());
       if (heap_->incremental_marking()->IsMarking()) {
-        marking_barrier_->Activate(
-            heap_->incremental_marking()->IsCompacting());
+        marking_barrier_->Activate(heap_->incremental_marking()->IsCompacting(),
+                                   heap_->incremental_marking()->is_minor()
+                                       ? MarkingBarrierType::kMinor
+                                       : MarkingBarrierType::kMajor);
       }
     }
   });

src/heap/marking-barrier-inl.h

@@ -30,6 +30,15 @@ bool MarkingBarrier::MarkValue(HeapObject host, HeapObject value) {
   }
   BasicMemoryChunk* target_page = BasicMemoryChunk::FromHeapObject(value);
   if (is_shared_heap_ != target_page->InSharedHeap()) return false;
+
+  if (is_minor()) {
+    // We do not need to insert into RememberedSet<OLD_TO_NEW> here because the
+    // C++ marking barrier already does this for us.
+    if (Heap::InYoungGeneration(value)) {
+      WhiteToGreyAndPush(value);  // NEW->NEW
+    }
+    return false;
+  } else {
     if (WhiteToGreyAndPush(value)) {
       if (V8_UNLIKELY(FLAG_track_retaining_path)) {
         heap_->AddRetainingRoot(Root::kWriteBarrier, value);
@@ -37,6 +46,7 @@ bool MarkingBarrier::MarkValue(HeapObject host, HeapObject value) {
     }
     return true;
   }
+}
 
 template <typename TSlot>
 inline void MarkingBarrier::MarkRange(HeapObject host, TSlot start, TSlot end) {
@@ -47,7 +57,8 @@ inline void MarkingBarrier::MarkRange(HeapObject host, TSlot start, TSlot end) {
     // Mark both, weak and strong edges.
     if (object.GetHeapObject(isolate, &heap_object)) {
       if (MarkValue(host, heap_object) && is_compacting_) {
-        collector_->RecordSlot(host, HeapObjectSlot(slot), heap_object);
+        DCHECK(is_major());
+        major_collector_->RecordSlot(host, HeapObjectSlot(slot), heap_object);
       }
     }
   }
@@ -55,7 +66,7 @@ inline void MarkingBarrier::MarkRange(HeapObject host, TSlot start, TSlot end) {
 
 bool MarkingBarrier::WhiteToGreyAndPush(HeapObject obj) {
   if (marking_state_.WhiteToGrey(obj)) {
-    worklist_.Push(obj);
+    current_worklist_->Push(obj);
     return true;
   }
   return false;

src/heap/marking-barrier.cc

@@ -24,9 +24,11 @@ namespace internal {
 
 MarkingBarrier::MarkingBarrier(LocalHeap* local_heap)
     : heap_(local_heap->heap()),
-      collector_(heap_->mark_compact_collector()),
+      major_collector_(heap_->mark_compact_collector()),
+      minor_collector_(heap_->minor_mark_compact_collector()),
       incremental_marking_(heap_->incremental_marking()),
-      worklist_(*collector_->marking_worklists()->shared()),
+      major_worklist_(*major_collector_->marking_worklists()->shared()),
+      minor_worklist_(*minor_collector_->marking_worklists()->shared()),
       marking_state_(heap_->isolate()),
       is_main_thread_barrier_(local_heap->is_main_thread()),
       is_shared_heap_(heap_->IsShared()) {}
@@ -38,15 +40,18 @@ void MarkingBarrier::Write(HeapObject host, HeapObjectSlot slot,
   DCHECK(IsCurrentMarkingBarrier());
   if (MarkValue(host, value)) {
     if (is_compacting_ && slot.address()) {
-      collector_->RecordSlot(host, slot, value);
+      DCHECK(is_major());
+      major_collector_->RecordSlot(host, slot, value);
     }
   }
 }
 
 void MarkingBarrier::WriteWithoutHost(HeapObject value) {
   DCHECK(is_main_thread_barrier_);
+  if (is_minor() && !Heap::InYoungGeneration(value)) return;
+
   if (WhiteToGreyAndPush(value)) {
-    if (V8_UNLIKELY(FLAG_track_retaining_path)) {
+    if (V8_UNLIKELY(FLAG_track_retaining_path) && is_major()) {
       heap_->AddRetainingRoot(Root::kWriteBarrier, value);
     }
   }
@@ -56,10 +61,11 @@ void MarkingBarrier::Write(Code host, RelocInfo* reloc_info, HeapObject value) {
   DCHECK(IsCurrentMarkingBarrier());
   if (MarkValue(host, value)) {
     if (is_compacting_) {
+      DCHECK(is_major());
       if (is_main_thread_barrier_) {
         // An optimization to avoid allocating additional typed slots for the
         // main thread.
-        collector_->RecordRelocSlot(host, reloc_info, value);
+        major_collector_->RecordRelocSlot(host, reloc_info, value);
       } else {
         RecordRelocSlot(host, reloc_info, value);
       }
@@ -74,13 +80,22 @@ void MarkingBarrier::Write(JSArrayBuffer host,
     // The extension will be marked when the marker visits the host object.
     return;
   }
+  if (is_minor()) {
+    if (Heap::InYoungGeneration(host)) {
+      extension->YoungMark();
+    }
+  } else {
     extension->Mark();
   }
+}
 
 void MarkingBarrier::Write(DescriptorArray descriptor_array,
                            int number_of_own_descriptors) {
   DCHECK(IsCurrentMarkingBarrier());
   DCHECK(IsReadOnlyHeapObject(descriptor_array.map()));
+
+  if (is_minor() && !heap_->InYoungGeneration(descriptor_array)) return;
+
   // The DescriptorArray needs to be marked black here to ensure that slots are
   // recorded by the Scavenger in case the DescriptorArray is promoted while
   // incremental marking is running. This is needed as the regular marking
@@ -93,8 +108,14 @@ void MarkingBarrier::Write(DescriptorArray descriptor_array,
     MarkRange(descriptor_array, descriptor_array.GetFirstPointerSlot(),
               descriptor_array.GetDescriptorSlot(0));
   }
-  const int16_t old_marked = descriptor_array.UpdateNumberOfMarkedDescriptors(
-      collector_->epoch(), number_of_own_descriptors);
+
+  // Concurrent MinorMC always marks the full young generation DescriptorArray.
+  // We cannot use epoch like MajorMC does because only the lower 2 bits are
+  // used, and with many MinorMC cycles this could lead to correctness issues.
+  const int16_t old_marked =
+      is_minor() ? 0
+                 : descriptor_array.UpdateNumberOfMarkedDescriptors(
+                       major_collector_->epoch(), number_of_own_descriptors);
   if (old_marked < number_of_own_descriptors) {
     // This marks the range from [old_marked, number_of_own_descriptors) instead
     // of registering weak slots which may temporarily hold alive more objects
@@ -123,9 +144,12 @@ void MarkingBarrier::RecordRelocSlot(Code host, RelocInfo* rinfo,
 }
 
 // static
-void MarkingBarrier::ActivateAll(Heap* heap, bool is_compacting) {
-  heap->safepoint()->IterateLocalHeaps([is_compacting](LocalHeap* local_heap) {
-    local_heap->marking_barrier()->Activate(is_compacting);
+void MarkingBarrier::ActivateAll(Heap* heap, bool is_compacting,
+                                 MarkingBarrierType marking_barrier_type) {
+  heap->safepoint()->IterateLocalHeaps(
+      [is_compacting, marking_barrier_type](LocalHeap* local_heap) {
+        local_heap->marking_barrier()->Activate(is_compacting,
+                                                marking_barrier_type);
       });
 }
 
@@ -144,7 +168,7 @@ void MarkingBarrier::PublishAll(Heap* heap) {
 
 void MarkingBarrier::Publish() {
   if (is_activated_) {
-    worklist_.Publish();
+    current_worklist_->Publish();
     base::Optional<CodePageHeaderModificationScope> optional_rwx_write_scope;
     if (!typed_slots_map_.empty()) {
       optional_rwx_write_scope.emplace(
@@ -200,7 +224,7 @@ void MarkingBarrier::Deactivate() {
     }
   }
   DCHECK(typed_slots_map_.empty());
-  DCHECK(worklist_.IsLocalEmpty());
+  DCHECK(current_worklist_->IsLocalEmpty());
 }
 
 void MarkingBarrier::ActivateSpace(PagedSpace* space) {
@@ -217,10 +241,14 @@ void MarkingBarrier::ActivateSpace(NewSpace* space) {
   }
 }
 
-void MarkingBarrier::Activate(bool is_compacting) {
+void MarkingBarrier::Activate(bool is_compacting,
+                              MarkingBarrierType marking_barrier_type) {
   DCHECK(!is_activated_);
-  DCHECK(worklist_.IsLocalEmpty());
+  DCHECK(major_worklist_.IsLocalEmpty());
+  DCHECK(minor_worklist_.IsLocalEmpty());
   is_compacting_ = is_compacting;
+  marking_barrier_type_ = marking_barrier_type;
+  current_worklist_ = is_minor() ? &minor_worklist_ : &major_worklist_;
   is_activated_ = true;
   if (is_main_thread_barrier_) {
     ActivateSpace(heap_->old_space());

src/heap/marking-barrier.h

@@ -18,16 +18,19 @@ class LocalHeap;
 class PagedSpace;
 class NewSpace;
 
+enum class MarkingBarrierType { kMinor, kMajor };
+
 class MarkingBarrier {
  public:
   explicit MarkingBarrier(LocalHeap*);
   ~MarkingBarrier();
 
-  void Activate(bool is_compacting);
+  void Activate(bool is_compacting, MarkingBarrierType marking_barrier_type);
   void Deactivate();
   void Publish();
 
-  static void ActivateAll(Heap* heap, bool is_compacting);
+  static void ActivateAll(Heap* heap, bool is_compacting,
+                          MarkingBarrierType marking_barrier_type);
   static void DeactivateAll(Heap* heap);
   V8_EXPORT_PRIVATE static void PublishAll(Heap* heap);
 
@@ -58,10 +61,20 @@ class MarkingBarrier {
   template <typename TSlot>
   inline void MarkRange(HeapObject value, TSlot start, TSlot end);
 
+  bool is_minor() const {
+    return marking_barrier_type_ == MarkingBarrierType::kMinor;
+  }
+  bool is_major() const {
+    return marking_barrier_type_ == MarkingBarrierType::kMajor;
+  }
+
   Heap* heap_;
-  MarkCompactCollector* collector_;
+  MarkCompactCollector* major_collector_;
+  MinorMarkCompactCollector* minor_collector_;
   IncrementalMarking* incremental_marking_;
-  MarkingWorklist::Local worklist_;
+  MarkingWorklist::Local major_worklist_;
+  MarkingWorklist::Local minor_worklist_;
+  MarkingWorklist::Local* current_worklist_;
   MarkingState marking_state_;
   std::unordered_map<MemoryChunk*, std::unique_ptr<TypedSlots>,
                      MemoryChunk::Hasher>
@@ -70,6 +83,7 @@ class MarkingBarrier {
   bool is_activated_ = false;
   bool is_main_thread_barrier_;
   bool is_shared_heap_;
+  MarkingBarrierType marking_barrier_type_;
 };
 
 }  // namespace internal