Experimental parser: merge to r19637

src/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 38 matching lines @@
 
 const char* Marking::kWhiteBitPattern = "00";
 const char* Marking::kBlackBitPattern = "10";
 const char* Marking::kGreyBitPattern = "11";
 const char* Marking::kImpossibleBitPattern = "01";
 
 
 // -------------------------------------------------------------------------
 // MarkCompactCollector
 
-MarkCompactCollector::MarkCompactCollector() :  // NOLINT
+MarkCompactCollector::MarkCompactCollector(Heap* heap) :  // NOLINT
 #ifdef DEBUG
       state_(IDLE),
 #endif
       sweep_precisely_(false),
       reduce_memory_footprint_(false),
       abort_incremental_marking_(false),
       marking_parity_(ODD_MARKING_PARITY),
       compacting_(false),
       was_marked_incrementally_(false),
       sweeping_pending_(false),
+      pending_sweeper_jobs_semaphore_(0),
       sequential_sweeping_(false),
       tracer_(NULL),
       migration_slots_buffer_(NULL),
-      heap_(NULL),
+      heap_(heap),
       code_flusher_(NULL),
       encountered_weak_collections_(NULL),
       have_code_to_deoptimize_(false) { }
 
 #ifdef VERIFY_HEAP
 class VerifyMarkingVisitor: public ObjectVisitor {
  public:
   explicit VerifyMarkingVisitor(Heap* heap) : heap_(heap) {}
 
   void VisitPointers(Object** start, Object** end) {
     for (Object** current = start; current < end; current++) {
       if ((*current)->IsHeapObject()) {
         HeapObject* object = HeapObject::cast(*current);
         CHECK(heap_->mark_compact_collector()->IsMarked(object));
       }
     }
   }
 
   void VisitEmbeddedPointer(RelocInfo* rinfo) {
     ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
-    if (!Code::IsWeakEmbeddedObject(rinfo->host()->kind(),
-                                    rinfo->target_object())) {
+    if (!rinfo->host()->IsWeakObject(rinfo->target_object())) {
       Object* p = rinfo->target_object();
       VisitPointer(&p);
     }
   }
 
   void VisitCell(RelocInfo* rinfo) {
     Code* code = rinfo->host();
     ASSERT(rinfo->rmode() == RelocInfo::CELL);
-    if (!Code::IsWeakEmbeddedObject(code->kind(), rinfo->target_cell())) {
+    if (!code->IsWeakObject(rinfo->target_cell())) {
       ObjectVisitor::VisitCell(rinfo);
     }
   }
 
  private:
   Heap* heap_;
 };
 
 
 static void VerifyMarking(Heap* heap, Address bottom, Address top) {
@@ skipping 226 matching lines @@
   HeapObjectIterator it(heap->code_space());
 
   for (Object* object = it.Next(); object != NULL; object = it.Next()) {
     VerifyNativeContextSeparationVisitor visitor;
     Code::cast(object)->CodeIterateBody(&visitor);
   }
 }
 #endif
 
 
+void MarkCompactCollector::SetUp() {
+  free_list_old_data_space_.Reset(new FreeList(heap_->old_data_space()));
+  free_list_old_pointer_space_.Reset(new FreeList(heap_->old_pointer_space()));
+}
+
+
 void MarkCompactCollector::TearDown() {
   AbortCompaction();
 }
 
 
 void MarkCompactCollector::AddEvacuationCandidate(Page* p) {
   p->MarkEvacuationCandidate();
   evacuation_candidates_.Add(p);
 }
 
@@ skipping 195 matching lines @@
   for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
     MarkBit mark_bit = Marking::MarkBitFrom(obj);
     mark_bit.Clear();
     mark_bit.Next().Clear();
     Page::FromAddress(obj->address())->ResetProgressBar();
     Page::FromAddress(obj->address())->ResetLiveBytes();
   }
 }
 
 
+class MarkCompactCollector::SweeperTask : public v8::Task {
+ public:
+  SweeperTask(Heap* heap, PagedSpace* space)
+    : heap_(heap), space_(space) {}
+
+  virtual ~SweeperTask() {}
+
+ private:
+  // v8::Task overrides.
+  virtual void Run() V8_OVERRIDE {
+    heap_->mark_compact_collector()->SweepInParallel(space_);
+    heap_->mark_compact_collector()->pending_sweeper_jobs_semaphore_.Signal();
+  }
+
+  Heap* heap_;
+  PagedSpace* space_;
+
+  DISALLOW_COPY_AND_ASSIGN(SweeperTask);
+};
+
+
 void MarkCompactCollector::StartSweeperThreads() {
+  // TODO(hpayer): This check is just used for debugging purpose and
+  // should be removed or turned into an assert after investigating the
+  // crash in concurrent sweeping.
+  CHECK(free_list_old_pointer_space_.get()->IsEmpty());
+  CHECK(free_list_old_data_space_.get()->IsEmpty());
   sweeping_pending_ = true;
   for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
     isolate()->sweeper_threads()[i]->StartSweeping();
   }
+  if (FLAG_job_based_sweeping) {
+    V8::GetCurrentPlatform()->CallOnBackgroundThread(
+        new SweeperTask(heap(), heap()->old_data_space()),
+        v8::Platform::kShortRunningTask);
+    V8::GetCurrentPlatform()->CallOnBackgroundThread(
+        new SweeperTask(heap(), heap()->old_pointer_space()),
+        v8::Platform::kShortRunningTask);
+  }
 }
 
 
 void MarkCompactCollector::WaitUntilSweepingCompleted() {
   ASSERT(sweeping_pending_ == true);
   for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
     isolate()->sweeper_threads()[i]->WaitForSweeperThread();
   }
+  if (FLAG_job_based_sweeping) {
+    // Wait twice for both jobs.
+    pending_sweeper_jobs_semaphore_.Wait();
+    pending_sweeper_jobs_semaphore_.Wait();
+  }
+  ParallelSweepSpacesComplete();
   sweeping_pending_ = false;
-  StealMemoryFromSweeperThreads(heap()->paged_space(OLD_DATA_SPACE));
-  StealMemoryFromSweeperThreads(heap()->paged_space(OLD_POINTER_SPACE));
+  RefillFreeLists(heap()->paged_space(OLD_DATA_SPACE));
+  RefillFreeLists(heap()->paged_space(OLD_POINTER_SPACE));
   heap()->paged_space(OLD_DATA_SPACE)->ResetUnsweptFreeBytes();
   heap()->paged_space(OLD_POINTER_SPACE)->ResetUnsweptFreeBytes();
 }
 
 
-intptr_t MarkCompactCollector::
-             StealMemoryFromSweeperThreads(PagedSpace* space) {
-  intptr_t freed_bytes = 0;
-  for (int i = 0; i < isolate()->num_sweeper_threads(); i++) {
-    freed_bytes += isolate()->sweeper_threads()[i]->StealMemory(space);
+intptr_t MarkCompactCollector::RefillFreeLists(PagedSpace* space) {
+  FreeList* free_list;
+
+  if (space == heap()->old_pointer_space()) {
+    free_list = free_list_old_pointer_space_.get();
+  } else if (space == heap()->old_data_space()) {
+    free_list = free_list_old_data_space_.get();
+  } else {
+    // Any PagedSpace might invoke RefillFreeLists, so we need to make sure
+    // to only refill them for old data and pointer spaces.
+    return 0;
   }
+
+  intptr_t freed_bytes = space->free_list()->Concatenate(free_list);
   space->AddToAccountingStats(freed_bytes);
   space->DecrementUnsweptFreeBytes(freed_bytes);
   return freed_bytes;
 }
 
 
 bool MarkCompactCollector::AreSweeperThreadsActivated() {
-  return isolate()->sweeper_threads() != NULL;
+  return isolate()->sweeper_threads() != NULL || FLAG_job_based_sweeping;
 }
 
 
 bool MarkCompactCollector::IsConcurrentSweepingInProgress() {
   return sweeping_pending_;
 }
 
 
 bool Marking::TransferMark(Address old_start, Address new_start) {
   // This is only used when resizing an object.
@@ skipping 1981 matching lines @@
 
   int new_number_of_transitions = 0;
   const int header = Map::kProtoTransitionHeaderSize;
   const int proto_offset = header + Map::kProtoTransitionPrototypeOffset;
   const int map_offset = header + Map::kProtoTransitionMapOffset;
   const int step = Map::kProtoTransitionElementsPerEntry;
   for (int i = 0; i < number_of_transitions; i++) {
     Object* prototype = prototype_transitions->get(proto_offset + i * step);
     Object* cached_map = prototype_transitions->get(map_offset + i * step);
     if (IsMarked(prototype) && IsMarked(cached_map)) {
+      ASSERT(!prototype->IsUndefined());
       int proto_index = proto_offset + new_number_of_transitions * step;
       int map_index = map_offset + new_number_of_transitions * step;
       if (new_number_of_transitions != i) {
         prototype_transitions->set(
             proto_index,
             prototype,
             UPDATE_WRITE_BARRIER);
         prototype_transitions->set(
             map_index,
             cached_map,
@@ skipping 154 matching lines @@
 // pointers to new space.
 void MarkCompactCollector::MigrateObject(Address dst,
                                          Address src,
                                          int size,
                                          AllocationSpace dest) {
   HeapProfiler* heap_profiler = heap()->isolate()->heap_profiler();
   if (heap_profiler->is_tracking_object_moves()) {
     heap_profiler->ObjectMoveEvent(src, dst, size);
   }
   ASSERT(heap()->AllowedToBeMigrated(HeapObject::FromAddress(src), dest));
-  ASSERT(dest != LO_SPACE && size <= Page::kMaxNonCodeHeapObjectSize);
+  ASSERT(dest != LO_SPACE && size <= Page::kMaxRegularHeapObjectSize);
   if (dest == OLD_POINTER_SPACE) {
     Address src_slot = src;
     Address dst_slot = dst;
     ASSERT(IsAligned(size, kPointerSize));
 
     for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
       Object* value = Memory::Object_at(src_slot);
 
       Memory::Object_at(dst_slot) = value;
 
@@ skipping 153 matching lines @@
     return String::cast(map_word.ToForwardingAddress());
   }
 
   return String::cast(*p);
 }
 
 
 bool MarkCompactCollector::TryPromoteObject(HeapObject* object,
                                             int object_size) {
   // TODO(hpayer): Replace that check with an assert.
-  CHECK(object_size <= Page::kMaxNonCodeHeapObjectSize);
+  CHECK(object_size <= Page::kMaxRegularHeapObjectSize);
 
   OldSpace* target_space = heap()->TargetSpace(object);
 
   ASSERT(target_space == heap()->old_pointer_space() ||
          target_space == heap()->old_data_space());
   Object* result;
   MaybeObject* maybe_result = target_space->AllocateRaw(object_size);
   if (maybe_result->ToObject(&result)) {
     HeapObject* target = HeapObject::cast(result);
     MigrateObject(target->address(),
@@ skipping 86 matching lines @@
     *cell = 0;
   }
   p->ResetLiveBytes();
 }
 
 
 void MarkCompactCollector::EvacuatePages() {
   int npages = evacuation_candidates_.length();
   for (int i = 0; i < npages; i++) {
     Page* p = evacuation_candidates_[i];
-    ASSERT(p->IsEvacuationCandidate() ||
-           p->IsFlagSet(Page::RESCAN_ON_EVACUATION));
+    // TODO(hpayer): This check is just used for debugging purpose and
+    // should be removed or turned into an assert after investigating the
+    // crash in concurrent sweeping.
+    CHECK(p->IsEvacuationCandidate() ||
+          p->IsFlagSet(Page::RESCAN_ON_EVACUATION));
+    CHECK_EQ(static_cast<int>(p->parallel_sweeping()), 0);
     if (p->IsEvacuationCandidate()) {
       // During compaction we might have to request a new page.
       // Check that space still have room for that.
       if (static_cast<PagedSpace*>(p->owner())->CanExpand()) {
         EvacuateLiveObjectsFromPage(p);
       } else {
         // Without room for expansion evacuation is not guaranteed to succeed.
         // Pessimistically abandon unevacuated pages.
         for (int j = i; j < npages; j++) {
           Page* page = evacuation_candidates_[j];
@@ skipping 70 matching lines @@
   SWEEP_AND_VISIT_LIVE_OBJECTS
 };
 
 
 enum SkipListRebuildingMode {
   REBUILD_SKIP_LIST,
   IGNORE_SKIP_LIST
 };
 
 
+enum FreeSpaceTreatmentMode {
+  IGNORE_FREE_SPACE,
+  ZAP_FREE_SPACE
+};
+
+
 // Sweep a space precisely.  After this has been done the space can
 // be iterated precisely, hitting only the live objects.  Code space
 // is always swept precisely because we want to be able to iterate
 // over it.  Map space is swept precisely, because it is not compacted.
 // Slots in live objects pointing into evacuation candidates are updated
 // if requested.
-template<SweepingMode sweeping_mode, SkipListRebuildingMode skip_list_mode>
+template<SweepingMode sweeping_mode,
+         SkipListRebuildingMode skip_list_mode,
+         FreeSpaceTreatmentMode free_space_mode>
 static void SweepPrecisely(PagedSpace* space,
                            Page* p,
                            ObjectVisitor* v) {
   ASSERT(!p->IsEvacuationCandidate() && !p->WasSwept());
   ASSERT_EQ(skip_list_mode == REBUILD_SKIP_LIST,
             space->identity() == CODE_SPACE);
   ASSERT((p->skip_list() == NULL) || (skip_list_mode == REBUILD_SKIP_LIST));
 
   double start_time = 0.0;
   if (FLAG_print_cumulative_gc_stat) {
@@ skipping 13 matching lines @@
   }
 
   for (MarkBitCellIterator it(p); !it.Done(); it.Advance()) {
     Address cell_base = it.CurrentCellBase();
     MarkBit::CellType* cell = it.CurrentCell();
     int live_objects = MarkWordToObjectStarts(*cell, offsets);
     int live_index = 0;
     for ( ; live_objects != 0; live_objects--) {
       Address free_end = cell_base + offsets[live_index++] * kPointerSize;
       if (free_end != free_start) {
+        if (free_space_mode == ZAP_FREE_SPACE) {
+          memset(free_start, 0xcc, static_cast<int>(free_end - free_start));
+        }
         space->Free(free_start, static_cast<int>(free_end - free_start));
 #ifdef ENABLE_GDB_JIT_INTERFACE
         if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
           GDBJITInterface::RemoveCodeRange(free_start, free_end);
         }
 #endif
       }
       HeapObject* live_object = HeapObject::FromAddress(free_end);
       ASSERT(Marking::IsBlack(Marking::MarkBitFrom(live_object)));
       Map* map = live_object->map();
@@ skipping 11 matching lines @@
           skip_list->AddObject(free_end, size);
           curr_region = new_region_end;
         }
       }
       free_start = free_end + size;
     }
     // Clear marking bits for current cell.
     *cell = 0;
   }
   if (free_start != p->area_end()) {
+    if (free_space_mode == ZAP_FREE_SPACE) {
+      memset(free_start, 0xcc, static_cast<int>(p->area_end() - free_start));
+    }
     space->Free(free_start, static_cast<int>(p->area_end() - free_start));
 #ifdef ENABLE_GDB_JIT_INTERFACE
     if (FLAG_gdbjit && space->identity() == CODE_SPACE) {
       GDBJITInterface::RemoveCodeRange(free_start, p->area_end());
     }
 #endif
   }
   p->ResetLiveBytes();
   if (FLAG_print_cumulative_gc_stat) {
     space->heap()->AddSweepingTime(OS::TimeCurrentMillis() - start_time);
@@ skipping 125 matching lines @@
 
 void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
   Heap::RelocationLock relocation_lock(heap());
 
   bool code_slots_filtering_required;
   { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP_NEWSPACE);
     code_slots_filtering_required = MarkInvalidatedCode();
     EvacuateNewSpace();
   }
 
-  // We have to travers our allocation sites scratchpad which contains raw
-  // pointers before we move objects. During new space evacauation we
-  // gathered pretenuring statistics. The found allocation sites may not be
-  // valid after compacting old space.
-  heap()->ProcessPretenuringFeedback();
-
-
   { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_EVACUATE_PAGES);
     EvacuatePages();
   }
 
   // Second pass: find pointers to new space and update them.
   PointersUpdatingVisitor updating_visitor(heap());
 
   { GCTracer::Scope gc_scope(tracer_,
                              GCTracer::Scope::MC_UPDATE_NEW_TO_NEW_POINTERS);
     // Update pointers in to space.
@@ skipping 80 matching lines @@
                  reinterpret_cast<intptr_t>(p));
         }
         PagedSpace* space = static_cast<PagedSpace*>(p->owner());
         p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION);
 
         switch (space->identity()) {
           case OLD_DATA_SPACE:
             SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
             break;
           case OLD_POINTER_SPACE:
-            SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS, IGNORE_SKIP_LIST>(
+            SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+                           IGNORE_SKIP_LIST,
+                           IGNORE_FREE_SPACE>(
                 space, p, &updating_visitor);
             break;
           case CODE_SPACE:
-            SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS, REBUILD_SKIP_LIST>(
-                space, p, &updating_visitor);
+            if (FLAG_zap_code_space) {
+              SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+                             REBUILD_SKIP_LIST,
+                             ZAP_FREE_SPACE>(
+                  space, p, &updating_visitor);
+            } else {
+              SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS,
+                             REBUILD_SKIP_LIST,
+                             IGNORE_FREE_SPACE>(
+                  space, p, &updating_visitor);
+            }
             break;
           default:
             UNREACHABLE();
             break;
         }
       }
     }
   }
 
   GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_UPDATE_MISC_POINTERS);
@@ skipping 391 matching lines @@
 // spaces have been put on the free list and the smaller ones have been
 // ignored and left untouched.  A free space is always either ignored or put
 // on the free list, never split up into two parts.  This is important
 // because it means that any FreeSpace maps left actually describe a region of
 // memory that can be ignored when scanning.  Dead objects other than free
 // spaces will not contain the free space map.
 template<MarkCompactCollector::SweepingParallelism mode>
 intptr_t MarkCompactCollector::SweepConservatively(PagedSpace* space,
                                                    FreeList* free_list,
                                                    Page* p) {
-  ASSERT(!p->IsEvacuationCandidate() && !p->WasSwept());
+  // TODO(hpayer): This check is just used for debugging purpose and
+  // should be removed or turned into an assert after investigating the
+  // crash in concurrent sweeping.
+  CHECK(!p->IsEvacuationCandidate() && !p->WasSwept());
   ASSERT((mode == MarkCompactCollector::SWEEP_IN_PARALLEL &&
          free_list != NULL) ||
          (mode == MarkCompactCollector::SWEEP_SEQUENTIALLY &&
          free_list == NULL));
 
-  p->MarkSweptConservatively();
+  // When parallel sweeping is active, the page will be marked after
+  // sweeping by the main thread.
+  if (mode != MarkCompactCollector::SWEEP_IN_PARALLEL) {
+    p->MarkSweptConservatively();
+  }
 
   intptr_t freed_bytes = 0;
   size_t size = 0;
 
   // Skip over all the dead objects at the start of the page and mark them free.
   Address cell_base = 0;
   MarkBit::CellType* cell = NULL;
   MarkBitCellIterator it(p);
   for (; !it.Done(); it.Advance()) {
     cell_base = it.CurrentCellBase();
@@ skipping 57 matching lines @@
     free_start = DigestFreeStart(free_start, free_start_cell);
     freed_bytes += Free<mode>(space, free_list, free_start,
                               static_cast<int>(p->area_end() - free_start));
   }
 
   p->ResetLiveBytes();
   return freed_bytes;
 }
 
 
-void MarkCompactCollector::SweepInParallel(PagedSpace* space,
-                                           FreeList* private_free_list,
-                                           FreeList* free_list) {
+void MarkCompactCollector::SweepInParallel(PagedSpace* space) {
   PageIterator it(space);
+  FreeList* free_list = space == heap()->old_pointer_space()
+                            ? free_list_old_pointer_space_.get()
+                            : free_list_old_data_space_.get();
+  FreeList private_free_list(space);
   while (it.has_next()) {
     Page* p = it.next();
 
     if (p->TryParallelSweeping()) {
-      SweepConservatively<SWEEP_IN_PARALLEL>(space, private_free_list, p);
-      free_list->Concatenate(private_free_list);
+      SweepConservatively<SWEEP_IN_PARALLEL>(space, &private_free_list, p);
+      free_list->Concatenate(&private_free_list);
     }
   }
 }
 
 
 void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
   space->set_was_swept_conservatively(sweeper == CONSERVATIVE ||
                                       sweeper == LAZY_CONSERVATIVE ||
                                       sweeper == PARALLEL_CONSERVATIVE ||
                                       sweeper == CONCURRENT_CONSERVATIVE);
   space->ClearStats();
 
   PageIterator it(space);
 
   int pages_swept = 0;
   bool lazy_sweeping_active = false;
   bool unused_page_present = false;
   bool parallel_sweeping_active = false;
 
   while (it.has_next()) {
     Page* p = it.next();
 
-    ASSERT(p->parallel_sweeping() == 0);
+    ASSERT(p->parallel_sweeping() == MemoryChunk::PARALLEL_SWEEPING_DONE);
     ASSERT(!p->IsEvacuationCandidate());
 
     // Clear sweeping flags indicating that marking bits are still intact.
     p->ClearSweptPrecisely();
     p->ClearSweptConservatively();
 
     if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
       // Will be processed in EvacuateNewSpaceAndCandidates.
       ASSERT(evacuation_candidates_.length() > 0);
       continue;
@@ skipping 52 matching lines @@
                    reinterpret_cast<intptr_t>(p));
           }
           SweepConservatively<SWEEP_SEQUENTIALLY>(space, NULL, p);
           pages_swept++;
           parallel_sweeping_active = true;
         } else {
           if (FLAG_gc_verbose) {
             PrintF("Sweeping 0x%" V8PRIxPTR " conservatively in parallel.\n",
                    reinterpret_cast<intptr_t>(p));
           }
-          p->set_parallel_sweeping(1);
+          p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_PENDING);
           space->IncreaseUnsweptFreeBytes(p);
         }
         break;
       }
       case PRECISE: {
         if (FLAG_gc_verbose) {
           PrintF("Sweeping 0x%" V8PRIxPTR " precisely.\n",
                  reinterpret_cast<intptr_t>(p));
         }
-        if (space->identity() == CODE_SPACE) {
-          SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST>(space, p, NULL);
+        if (space->identity() == CODE_SPACE && FLAG_zap_code_space) {
+          SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST, ZAP_FREE_SPACE>(
+              space, p, NULL);
+        } else if (space->identity() == CODE_SPACE) {
+          SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST, IGNORE_FREE_SPACE>(
+              space, p, NULL);
         } else {
-          SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST>(space, p, NULL);
+          SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(
+              space, p, NULL);
         }
         pages_swept++;
         break;
       }
       default: {
         UNREACHABLE();
       }
     }
   }
 
   if (FLAG_gc_verbose) {
     PrintF("SweepSpace: %s (%d pages swept)\n",
            AllocationSpaceName(space->identity()),
            pages_swept);
   }
 
   // Give pages that are queued to be freed back to the OS.
   heap()->FreeQueuedChunks();
 }
 
 
 void MarkCompactCollector::SweepSpaces() {
   GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP);
 #ifdef DEBUG
   state_ = SWEEP_SPACES;
 #endif
   SweeperType how_to_sweep =
       FLAG_lazy_sweeping ? LAZY_CONSERVATIVE : CONSERVATIVE;
-  if (isolate()->num_sweeper_threads() > 0) {
+  if (AreSweeperThreadsActivated()) {
     if (FLAG_parallel_sweeping) how_to_sweep = PARALLEL_CONSERVATIVE;
     if (FLAG_concurrent_sweeping) how_to_sweep = CONCURRENT_CONSERVATIVE;
   }
-  if (FLAG_expose_gc) how_to_sweep = CONSERVATIVE;
   if (sweep_precisely_) how_to_sweep = PRECISE;
 
   // Unlink evacuation candidates before sweeper threads access the list of
   // pages to avoid race condition.
   UnlinkEvacuationCandidates();
 
   // Noncompacting collections simply sweep the spaces to clear the mark
   // bits and free the nonlive blocks (for old and map spaces).  We sweep
   // the map space last because freeing non-live maps overwrites them and
   // the other spaces rely on possibly non-live maps to get the sizes for
@@ skipping 26 matching lines @@
   SweepSpace(heap()->map_space(), PRECISE);
 
   // Deallocate unmarked objects and clear marked bits for marked objects.
   heap_->lo_space()->FreeUnmarkedObjects();
 
   // Deallocate evacuated candidate pages.
   ReleaseEvacuationCandidates();
 }
 
 
+void MarkCompactCollector::ParallelSweepSpaceComplete(PagedSpace* space) {
+  PageIterator it(space);
+  while (it.has_next()) {
+    Page* p = it.next();
+    if (p->parallel_sweeping() == MemoryChunk::PARALLEL_SWEEPING_IN_PROGRESS) {
+      p->set_parallel_sweeping(MemoryChunk::PARALLEL_SWEEPING_DONE);
+      p->MarkSweptConservatively();
+    }
+  }
+}
+
+
+void MarkCompactCollector::ParallelSweepSpacesComplete() {
+  ParallelSweepSpaceComplete(heap()->old_pointer_space());
+  ParallelSweepSpaceComplete(heap()->old_data_space());
+}
+
+
 void MarkCompactCollector::EnableCodeFlushing(bool enable) {
 #ifdef ENABLE_DEBUGGER_SUPPORT
   if (isolate()->debug()->IsLoaded() ||
       isolate()->debug()->has_break_points()) {
     enable = false;
   }
 #endif
 
   if (enable) {
     if (code_flusher_ != NULL) return;
@@ skipping 188 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal