[heap] Concurrently free empty slot set buckets.

src/heap/remembered-set.cc

 // Copyright 2016 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/remembered-set.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/heap.h"
 #include "src/heap/mark-compact.h"
 #include "src/heap/slot-set.h"
 #include "src/heap/spaces.h"
 #include "src/heap/store-buffer.h"
 #include "src/macro-assembler.h"
 
 namespace v8 {
 namespace internal {
 
 template <PointerDirection direction>
 void RememberedSet<direction>::ClearInvalidSlots(Heap* heap) {
   STATIC_ASSERT(direction == OLD_TO_NEW);
   for (MemoryChunk* chunk : *heap->old_space()) {
     SlotSet* slots = GetSlotSet(chunk);
     if (slots != nullptr) {
-      slots->Iterate([heap, chunk](Address addr) {
-        Object** slot = reinterpret_cast<Object**>(addr);
-        return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
-      });
+      slots->Iterate(
+          [heap, chunk](Address addr) {
+            Object** slot = reinterpret_cast<Object**>(addr);
+            return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
+          },
+          SlotSet::PREFREE_EMPTY_BUCKETS);
     }
   }
   for (MemoryChunk* chunk : *heap->code_space()) {
     TypedSlotSet* slots = GetTypedSlotSet(chunk);
     if (slots != nullptr) {
       slots->Iterate(
           [heap, chunk](SlotType type, Address host_addr, Address addr) {
             if (Marking::IsBlack(ObjectMarking::MarkBitFrom(host_addr))) {
               return KEEP_SLOT;
             } else {
               return REMOVE_SLOT;
             }
           },
           TypedSlotSet::PREFREE_EMPTY_CHUNKS);
     }
   }
   for (MemoryChunk* chunk : *heap->map_space()) {
     SlotSet* slots = GetSlotSet(chunk);
     if (slots != nullptr) {
-      slots->Iterate([heap, chunk](Address addr) {
-        Object** slot = reinterpret_cast<Object**>(addr);
-        // TODO(mlippautz): In map space all allocations would ideally be map
-        // aligned. After establishing this invariant IsValidSlot could just
-        // refer to the containing object using alignment and check the mark
-        // bits.
-        return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
-      });
+      slots->Iterate(
+          [heap, chunk](Address addr) {
+            Object** slot = reinterpret_cast<Object**>(addr);
+            // TODO(mlippautz): In map space all allocations would ideally be
+            // map
+            // aligned. After establishing this invariant IsValidSlot could just
+            // refer to the containing object using alignment and check the mark
+            // bits.
+            return IsValidSlot(heap, chunk, slot) ? KEEP_SLOT : REMOVE_SLOT;
+          },
+          SlotSet::PREFREE_EMPTY_BUCKETS);
     }
   }
 }
 
 template <PointerDirection direction>
 void RememberedSet<direction>::VerifyValidSlots(Heap* heap) {
   Iterate(heap, [heap](Address addr) {
     HeapObject* obj =
         heap->mark_compact_collector()->FindBlackObjectBySlotSlow(addr);
     if (obj == nullptr) {
@@ skipping 29 matching lines @@
          heap->mark_compact_collector()->IsSlotInBlackObject(
              chunk, reinterpret_cast<Address>(slot));
 }
 
 template void RememberedSet<OLD_TO_NEW>::ClearInvalidSlots(Heap* heap);
 template void RememberedSet<OLD_TO_NEW>::VerifyValidSlots(Heap* heap);
 template void RememberedSet<OLD_TO_OLD>::VerifyValidSlots(Heap* heap);
 
 }  // namespace internal
 }  // namespace v8