[heap] Add page evacuation mode for new->new

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 454 matching lines @@
               AllocationSpace space_to_start)
       : sweeper_(sweeper),
         pending_sweeper_tasks_(pending_sweeper_tasks),
         space_to_start_(space_to_start) {}
 
   virtual ~SweeperTask() {}
 
  private:
   // v8::Task overrides.
   void Run() override {
-    DCHECK_GE(space_to_start_, FIRST_PAGED_SPACE);
+    DCHECK_GE(space_to_start_, FIRST_SPACE);
     DCHECK_LE(space_to_start_, LAST_PAGED_SPACE);
-    const int offset = space_to_start_ - FIRST_PAGED_SPACE;
-    const int num_spaces = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1;
+    const int offset = space_to_start_ - FIRST_SPACE;
+    const int num_spaces = LAST_PAGED_SPACE - FIRST_SPACE + 1;
     for (int i = 0; i < num_spaces; i++) {
-      const int space_id = FIRST_PAGED_SPACE + ((i + offset) % num_spaces);
-      DCHECK_GE(space_id, FIRST_PAGED_SPACE);
+      const int space_id = FIRST_SPACE + ((i + offset) % num_spaces);
+      DCHECK_GE(space_id, FIRST_SPACE);
       DCHECK_LE(space_id, LAST_PAGED_SPACE);
       sweeper_->ParallelSweepSpace(static_cast<AllocationSpace>(space_id), 0);
     }
     pending_sweeper_tasks_->Signal();
   }
 
   Sweeper* sweeper_;
   base::Semaphore* pending_sweeper_tasks_;
   AllocationSpace space_to_start_;
 
@@ skipping 17 matching lines @@
 void MarkCompactCollector::Sweeper::StartSweepingHelper(
     AllocationSpace space_to_start) {
   num_sweeping_tasks_.Increment(1);
   V8::GetCurrentPlatform()->CallOnBackgroundThread(
       new SweeperTask(this, &pending_sweeper_tasks_semaphore_, space_to_start),
       v8::Platform::kShortRunningTask);
 }
 
 void MarkCompactCollector::Sweeper::SweepOrWaitUntilSweepingCompleted(
     Page* page) {
-  PagedSpace* owner = reinterpret_cast<PagedSpace*>(page->owner());
   if (!page->SweepingDone()) {
-    ParallelSweepPage(page, owner);
+    PagedSpace* owner = reinterpret_cast<PagedSpace*>(page->owner());
+    ParallelSweepPage(page, owner->identity());
     if (!page->SweepingDone()) {
       // We were not able to sweep that page, i.e., a concurrent
       // sweeper thread currently owns this page. Wait for the sweeper
       // thread to be done with this page.
       page->WaitUntilSweepingCompleted();
     }
   }
 }
 
 void MarkCompactCollector::SweepAndRefill(CompactionSpace* space) {
@@ skipping 22 matching lines @@
         [this](AllocationSpace space) { ParallelSweepSpace(space, 0); });
   }
 
   if (FLAG_concurrent_sweeping) {
     while (num_sweeping_tasks_.Value() > 0) {
       pending_sweeper_tasks_semaphore_.Wait();
       num_sweeping_tasks_.Increment(-1);
     }
   }
 
-  ForAllSweepingSpaces(
-      [this](AllocationSpace space) { DCHECK(sweeping_list_[space].empty()); });
+  ForAllSweepingSpaces([this](AllocationSpace space) {
+    if (space == NEW_SPACE) {
+      swept_list_[NEW_SPACE].Clear();
+    }
+    DCHECK(sweeping_list_[space].empty());
+  });
   late_pages_ = false;
   sweeping_in_progress_ = false;
 }
 
+void MarkCompactCollector::Sweeper::EnsureNewSpaceCompleted() {
+  if (!sweeping_in_progress_) return;
+  if (!FLAG_concurrent_sweeping || !IsSweepingCompleted()) {
+    NewSpacePageIterator pit(heap_->new_space());
+    while (pit.has_next()) {
+      Page* page = pit.next();
+      SweepOrWaitUntilSweepingCompleted(page);
+    }
+  }
+}
+
 void MarkCompactCollector::EnsureSweepingCompleted() {
   if (!sweeper().sweeping_in_progress()) return;
 
   sweeper().EnsureCompleted();
   heap()->old_space()->RefillFreeList();
   heap()->code_space()->RefillFreeList();
   heap()->map_space()->RefillFreeList();
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap && !evacuation()) {
@@ skipping 1284 matching lines @@
   AllocationSpace space_to_allocate_;
   intptr_t promoted_size_;
   intptr_t semispace_copied_size_;
   HashMap* local_pretenuring_feedback_;
 };
 
 class MarkCompactCollector::EvacuateNewSpacePageVisitor final
     : public MarkCompactCollector::HeapObjectVisitor {
  public:
   explicit EvacuateNewSpacePageVisitor(Heap* heap)
-      : heap_(heap), promoted_size_(0) {}
+      : heap_(heap), promoted_size_(0), semispace_copied_size_(0) {}
 
   static void TryMoveToOldSpace(Page* page, PagedSpace* owner) {
     if (page->heap()->new_space()->ReplaceWithEmptyPage(page)) {
       Page* new_page = Page::ConvertNewToOld(page, owner);
       new_page->SetFlag(Page::PAGE_NEW_OLD_PROMOTION);
     }
   }
 
+  static void MoveToToSpace(Page* page, Space* owner) {

[ulan, 2016/06/10 12:58:54]

Nit: the name seems a bit misleading since it hides the fact that we add a
replacement page to the from space.

[Michael Lippautz, 2016/06/10 15:18:15]

Done.

+    page->heap()->new_space()->AddPageToToSpace(page);
+    page->SetFlag(Page::PAGE_NEW_NEW_PROMOTION);
+  }
+
   inline bool Visit(HeapObject* object) {
     RecordMigratedSlotVisitor visitor(heap_->mark_compact_collector());
     object->IterateBodyFast(&visitor);
     promoted_size_ += object->Size();
     return true;
   }
 
   intptr_t promoted_size() { return promoted_size_; }
+  intptr_t semispace_copied_size() { return semispace_copied_size_; }
+
+  void account_semispace_copied(intptr_t copied) {
+    semispace_copied_size_ += copied;
+  }
 
  private:
   Heap* heap_;
   intptr_t promoted_size_;
+  intptr_t semispace_copied_size_;
 };
 
 class MarkCompactCollector::EvacuateOldSpaceVisitor final
     : public MarkCompactCollector::EvacuateVisitorBase {
  public:
   EvacuateOldSpaceVisitor(Heap* heap,
                           CompactionSpaceCollection* compaction_spaces)
       : EvacuateVisitorBase(heap, compaction_spaces) {}
 
   inline bool Visit(HeapObject* object) override {
@@ skipping 1123 matching lines @@
   NewSpace* new_space = heap()->new_space();
   NewSpacePageIterator it(new_space->bottom(), new_space->top());
   // Append the list of new space pages to be processed.
   while (it.has_next()) {
     newspace_evacuation_candidates_.Add(it.next());
   }
   new_space->Flip();
   new_space->ResetAllocationInfo();
 }
 
-void MarkCompactCollector::EvacuateNewSpaceEpilogue() {
-  newspace_evacuation_candidates_.Rewind(0);
-}
-
 class MarkCompactCollector::Evacuator : public Malloced {
  public:
+  enum EvacuationMode {
+    kObjectsNewToOld,
+    kPageNewToOld,
+    kObjectsOldToOld,
+    kPageNewToNew,
+  };
+
+  static inline EvacuationMode ComputeEvacuationMode(MemoryChunk* chunk) {
+    // Note: The order of checks is important in this function.
+    if (chunk->IsFlagSet(MemoryChunk::PAGE_NEW_OLD_PROMOTION))
+      return kPageNewToOld;
+    if (chunk->IsFlagSet(MemoryChunk::PAGE_NEW_NEW_PROMOTION))
+      return kPageNewToNew;
+    if (chunk->InNewSpace()) return kObjectsNewToOld;
+    DCHECK(chunk->IsEvacuationCandidate());
+    return kObjectsOldToOld;
+  }
+
   // NewSpacePages with more live bytes than this threshold qualify for fast
   // evacuation.
   static int PageEvacuationThreshold() {
     if (FLAG_page_promotion)
       return FLAG_page_promotion_threshold * Page::kAllocatableMemory / 100;
     return Page::kAllocatableMemory + kPointerSize;
   }
 
   explicit Evacuator(MarkCompactCollector* collector)
       : collector_(collector),
         compaction_spaces_(collector->heap()),
         local_pretenuring_feedback_(HashMap::PointersMatch,
                                     kInitialLocalPretenuringFeedbackCapacity),
         new_space_visitor_(collector->heap(), &compaction_spaces_,
                            &local_pretenuring_feedback_),
         new_space_page_visitor(collector->heap()),
         old_space_visitor_(collector->heap(), &compaction_spaces_),
         duration_(0.0),
         bytes_compacted_(0) {}
 
   inline bool EvacuatePage(Page* chunk);
 
   // Merge back locally cached info sequentially. Note that this method needs
   // to be called from the main thread.
   inline void Finalize();
 
   CompactionSpaceCollection* compaction_spaces() { return &compaction_spaces_; }
 
  private:
-  enum EvacuationMode {
-    kObjectsNewToOld,
-    kPageNewToOld,
-    kObjectsOldToOld,
-  };
-
   static const int kInitialLocalPretenuringFeedbackCapacity = 256;
 
   inline Heap* heap() { return collector_->heap(); }
 
-  inline EvacuationMode ComputeEvacuationMode(MemoryChunk* chunk) {
-    // Note: The order of checks is important in this function.
-    if (chunk->InNewSpace()) return kObjectsNewToOld;
-    if (chunk->IsFlagSet(MemoryChunk::PAGE_NEW_OLD_PROMOTION))
-      return kPageNewToOld;
-    DCHECK(chunk->IsEvacuationCandidate());
-    return kObjectsOldToOld;
-  }
-
   void ReportCompactionProgress(double duration, intptr_t bytes_compacted) {
     duration_ += duration;
     bytes_compacted_ += bytes_compacted;
   }
 
-  template <IterationMode mode, class Visitor>
-  inline bool EvacuateSinglePage(Page* p, Visitor* visitor);
-
   MarkCompactCollector* collector_;
 
   // Locally cached collector data.
   CompactionSpaceCollection compaction_spaces_;
   HashMap local_pretenuring_feedback_;
 
   // Visitors for the corresponding spaces.
   EvacuateNewSpaceVisitor new_space_visitor_;
   EvacuateNewSpacePageVisitor new_space_page_visitor;
   EvacuateOldSpaceVisitor old_space_visitor_;
 
   // Book keeping info.
   double duration_;
   intptr_t bytes_compacted_;
 };
 
-template <MarkCompactCollector::IterationMode mode, class Visitor>
-bool MarkCompactCollector::Evacuator::EvacuateSinglePage(Page* p,
-                                                         Visitor* visitor) {
+bool MarkCompactCollector::Evacuator::EvacuatePage(Page* page) {
   bool success = false;
-  DCHECK(p->IsEvacuationCandidate() || p->InNewSpace() ||
-         p->IsFlagSet(Page::PAGE_NEW_OLD_PROMOTION));
-  int saved_live_bytes = p->LiveBytes();
-  double evacuation_time;
+  DCHECK(page->SweepingDone());
+  int saved_live_bytes = page->LiveBytes();
+  double evacuation_time = 0.0;
+  Heap* heap = page->heap();
   {
-    AlwaysAllocateScope always_allocate(heap()->isolate());
+    AlwaysAllocateScope always_allocate(heap->isolate());
     TimedScope timed_scope(&evacuation_time);
-    success = collector_->VisitLiveObjects<Visitor>(p, visitor, mode);
+    switch (ComputeEvacuationMode(page)) {
+      case kObjectsNewToOld:
+        success = collector_->VisitLiveObjects(page, &new_space_visitor_,
+                                               kClearMarkbits);
+        ArrayBufferTracker::ProcessBuffers(
+            page, ArrayBufferTracker::kUpdateForwardedRemoveOthers);
+        DCHECK(success);
+        break;
+      case kPageNewToOld:
+        success = collector_->VisitLiveObjects(page, &new_space_page_visitor,
+                                               kKeepMarking);
+        // ArrayBufferTracker will be updated during sweeping.
+        DCHECK(success);
+        break;
+      case kPageNewToNew:
+        new_space_page_visitor.account_semispace_copied(page->LiveBytes());
+        // ArrayBufferTracker will be updated during sweeping.
+        success = true;
+        break;
+      case kObjectsOldToOld:
+        success = collector_->VisitLiveObjects(page, &old_space_visitor_,
+                                               kClearMarkbits);
+        if (!success) {
+          // Aborted compaction page. We have to record slots here, since we
+          // might not have recorded them in first place.
+          // Note: We mark the page as aborted here to be able to record slots
+          // for code objects in |RecordMigratedSlotVisitor|.
+          page->SetFlag(Page::COMPACTION_WAS_ABORTED);
+          EvacuateRecordOnlyVisitor record_visitor(collector_->heap());
+          success =
+              collector_->VisitLiveObjects(page, &record_visitor, kKeepMarking);
+          ArrayBufferTracker::ProcessBuffers(
+              page, ArrayBufferTracker::kUpdateForwardedKeepOthers);
+          DCHECK(success);
+          // We need to return failure here to indicate that we want this page
+          // added to the sweeper.
+          success = false;
+        } else {
+          ArrayBufferTracker::ProcessBuffers(
+              page, ArrayBufferTracker::kUpdateForwardedRemoveOthers);
+        }
+        break;
+      default:
+        UNREACHABLE();
+    }
   }
+  ReportCompactionProgress(evacuation_time, saved_live_bytes);
   if (FLAG_trace_evacuation) {
-    const char age_mark_tag =
-        !p->InNewSpace()
-            ? 'x'
-            : !p->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK)
-                  ? '>'
-                  : !p->ContainsLimit(heap()->new_space()->age_mark()) ? '<'
-                                                                       : '#';
-    PrintIsolate(heap()->isolate(),
-                 "evacuation[%p]: page=%p new_space=%d age_mark_tag=%c "
-                 "page_evacuation=%d executable=%d live_bytes=%d time=%f\n",
-                 static_cast<void*>(this), static_cast<void*>(p),
-                 p->InNewSpace(), age_mark_tag,
-                 p->IsFlagSet(MemoryChunk::PAGE_NEW_OLD_PROMOTION),
-                 p->IsFlagSet(MemoryChunk::IS_EXECUTABLE), saved_live_bytes,
-                 evacuation_time);
-  }
-  if (success) {
-    ReportCompactionProgress(evacuation_time, saved_live_bytes);
+    PrintIsolate(heap->isolate(),
+                 "evacuation[%p]: page=%p new_space=%d "
+                 "page_evacuation=%d executable=%d contains_age_mark=%d "
+                 "live_bytes=%d time=%f\n",
+                 static_cast<void*>(this), static_cast<void*>(page),
+                 page->InNewSpace(),
+                 page->IsFlagSet(Page::PAGE_NEW_OLD_PROMOTION) ||
+                     page->IsFlagSet(Page::PAGE_NEW_NEW_PROMOTION),
+                 page->IsFlagSet(MemoryChunk::IS_EXECUTABLE),
+                 page->Contains(heap->new_space()->age_mark()),
+                 saved_live_bytes, evacuation_time);
   }
   return success;
 }
 
-bool MarkCompactCollector::Evacuator::EvacuatePage(Page* page) {
-  bool result = false;
-  DCHECK(page->SweepingDone());
-  switch (ComputeEvacuationMode(page)) {
-    case kObjectsNewToOld:
-      result = EvacuateSinglePage<kClearMarkbits>(page, &new_space_visitor_);
-      ArrayBufferTracker::ProcessBuffers(
-          page, ArrayBufferTracker::kUpdateForwardedRemoveOthers);
-      DCHECK(result);
-      USE(result);
-      break;
-    case kPageNewToOld:
-      result = EvacuateSinglePage<kKeepMarking>(page, &new_space_page_visitor);
-      // ArrayBufferTracker will be updated during sweeping.
-      DCHECK(result);
-      USE(result);
-      break;
-    case kObjectsOldToOld:
-      result = EvacuateSinglePage<kClearMarkbits>(page, &old_space_visitor_);
-      if (!result) {
-        // Aborted compaction page. We have to record slots here, since we might
-        // not have recorded them in first place.
-        // Note: We mark the page as aborted here to be able to record slots
-        // for code objects in |RecordMigratedSlotVisitor|.
-        page->SetFlag(Page::COMPACTION_WAS_ABORTED);
-        EvacuateRecordOnlyVisitor record_visitor(collector_->heap());
-        result = EvacuateSinglePage<kKeepMarking>(page, &record_visitor);
-        ArrayBufferTracker::ProcessBuffers(
-            page, ArrayBufferTracker::kUpdateForwardedKeepOthers);
-        DCHECK(result);
-        USE(result);
-        // We need to return failure here to indicate that we want this page
-        // added to the sweeper.
-        return false;
-      }
-      ArrayBufferTracker::ProcessBuffers(
-          page, ArrayBufferTracker::kUpdateForwardedRemoveOthers);
-
-      break;
-    default:
-      UNREACHABLE();
-  }
-  return result;
-}
-
 void MarkCompactCollector::Evacuator::Finalize() {
   heap()->old_space()->MergeCompactionSpace(compaction_spaces_.Get(OLD_SPACE));
   heap()->code_space()->MergeCompactionSpace(
       compaction_spaces_.Get(CODE_SPACE));
   heap()->tracer()->AddCompactionEvent(duration_, bytes_compacted_);
   heap()->IncrementPromotedObjectsSize(new_space_visitor_.promoted_size() +
                                        new_space_page_visitor.promoted_size());
   heap()->IncrementSemiSpaceCopiedObjectSize(
-      new_space_visitor_.semispace_copied_size());
+      new_space_visitor_.semispace_copied_size() +
+      new_space_page_visitor.semispace_copied_size());
   heap()->IncrementYoungSurvivorsCounter(
       new_space_visitor_.promoted_size() +
       new_space_visitor_.semispace_copied_size() +
-      new_space_page_visitor.promoted_size());
+      new_space_page_visitor.promoted_size() +
+      new_space_page_visitor.semispace_copied_size());
   heap()->MergeAllocationSitePretenuringFeedback(local_pretenuring_feedback_);
 }
 
 int MarkCompactCollector::NumberOfParallelCompactionTasks(int pages,
                                                           intptr_t live_bytes) {
   if (!FLAG_parallel_compaction) return 1;
   // Compute the number of needed tasks based on a target compaction time, the
   // profiled compaction speed and marked live memory.
   //
   // The number of parallel compaction tasks is limited by:
@@ skipping 27 matching lines @@
 
   static const bool NeedSequentialFinalization = true;
 
   static bool ProcessPageInParallel(Heap* heap, PerTaskData evacuator,
                                     MemoryChunk* chunk, PerPageData) {
     return evacuator->EvacuatePage(reinterpret_cast<Page*>(chunk));
   }
 
   static void FinalizePageSequentially(Heap* heap, MemoryChunk* chunk,
                                        bool success, PerPageData data) {
-    if (chunk->InNewSpace()) {
-      DCHECK(success);
-    } else if (chunk->IsFlagSet(Page::PAGE_NEW_OLD_PROMOTION)) {
-      DCHECK(success);
-      Page* p = static_cast<Page*>(chunk);
-      p->ClearFlag(Page::PAGE_NEW_OLD_PROMOTION);
-      p->ForAllFreeListCategories(
-          [](FreeListCategory* category) { DCHECK(!category->is_linked()); });
-      heap->mark_compact_collector()->sweeper().AddLatePage(
-          p->owner()->identity(), p);
-    } else {
-      Page* p = static_cast<Page*>(chunk);
-      if (success) {
-        DCHECK(p->IsEvacuationCandidate());
-        DCHECK(p->SweepingDone());
-        p->Unlink();
-      } else {
-        // We have partially compacted the page, i.e., some objects may have
-        // moved, others are still in place.
-        p->ClearEvacuationCandidate();
-        // Slots have already been recorded so we just need to add it to the
-        // sweeper.
-        *data += 1;
-      }
+    using Evacuator = MarkCompactCollector::Evacuator;
+    Page* p = static_cast<Page*>(chunk);
+    switch (Evacuator::ComputeEvacuationMode(p)) {
+      case Evacuator::kPageNewToOld:
+        break;
+      case Evacuator::kPageNewToNew:
+        DCHECK(success);
+        break;
+      case Evacuator::kObjectsNewToOld:
+        DCHECK(success);
+        break;
+      case Evacuator::kObjectsOldToOld:
+        if (success) {
+          DCHECK(p->IsEvacuationCandidate());
+          DCHECK(p->SweepingDone());
+          p->Unlink();
+        } else {
+          // We have partially compacted the page, i.e., some objects may have
+          // moved, others are still in place.
+          p->ClearEvacuationCandidate();
+          // Slots have already been recorded so we just need to add it to the
+          // sweeper, which will happen after updating pointers.
+          *data += 1;
+        }
+        break;
+      default:
+        UNREACHABLE();
     }
   }
 };
 
 void MarkCompactCollector::EvacuatePagesInParallel() {
   PageParallelJob<EvacuationJobTraits> job(
       heap_, heap_->isolate()->cancelable_task_manager(),
       &page_parallel_job_semaphore_);
 
   int abandoned_pages = 0;
   intptr_t live_bytes = 0;
   for (Page* page : evacuation_candidates_) {
     live_bytes += page->LiveBytes();
     job.AddPage(page, &abandoned_pages);
   }
 
   const Address age_mark = heap()->new_space()->age_mark();
   for (Page* page : newspace_evacuation_candidates_) {
     live_bytes += page->LiveBytes();
     if (!page->NeverEvacuate() &&
         (page->LiveBytes() > Evacuator::PageEvacuationThreshold()) &&
-        page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK) &&
         !page->Contains(age_mark)) {
-      EvacuateNewSpacePageVisitor::TryMoveToOldSpace(page, heap()->old_space());
+      if (page->IsFlagSet(MemoryChunk::NEW_SPACE_BELOW_AGE_MARK)) {
+        EvacuateNewSpacePageVisitor::TryMoveToOldSpace(page,
+                                                       heap()->old_space());
+      } else {
+        EvacuateNewSpacePageVisitor::MoveToToSpace(page, heap()->new_space());
+      }
     }
+
     job.AddPage(page, &abandoned_pages);
   }
   DCHECK_GE(job.NumberOfPages(), 1);
 
   // Used for trace summary.
   double compaction_speed = 0;
   if (FLAG_trace_evacuation) {
     compaction_speed = heap()->tracer()->CompactionSpeedInBytesPerMillisecond();
   }
 
@@ skipping 33 matching lines @@
         return map_word.ToForwardingAddress();
       }
     }
     return object;
   }
 };
 
 template <MarkCompactCollector::Sweeper::SweepingMode sweeping_mode,
           MarkCompactCollector::Sweeper::SweepingParallelism parallelism,
           MarkCompactCollector::Sweeper::SkipListRebuildingMode skip_list_mode,
+          MarkCompactCollector::Sweeper::FreeListRebuildingMode free_list_mode,
           MarkCompactCollector::Sweeper::FreeSpaceTreatmentMode free_space_mode>
 int MarkCompactCollector::Sweeper::RawSweep(PagedSpace* space, Page* p,
                                             ObjectVisitor* v) {
   DCHECK(!p->IsEvacuationCandidate() && !p->SweepingDone());
   DCHECK(!p->IsFlagSet(Page::BLACK_PAGE));
-  DCHECK_EQ(skip_list_mode == REBUILD_SKIP_LIST,
-            space->identity() == CODE_SPACE);
+  DCHECK((space == nullptr) || (space->identity() != CODE_SPACE) ||
+         (skip_list_mode == REBUILD_SKIP_LIST));
   DCHECK((p->skip_list() == NULL) || (skip_list_mode == REBUILD_SKIP_LIST));
   DCHECK(parallelism == SWEEP_ON_MAIN_THREAD || sweeping_mode == SWEEP_ONLY);
 
   // Before we sweep objects on the page, we free dead array buffers which
   // requires valid mark bits.
   ArrayBufferTracker::FreeDead(p);
 
   Address free_start = p->area_start();
   DCHECK(reinterpret_cast<intptr_t>(free_start) % (32 * kPointerSize) == 0);
 
@@ skipping 12 matching lines @@
   LiveObjectIterator<kBlackObjects> it(p);
   HeapObject* object = NULL;
   while ((object = it.Next()) != NULL) {
     DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object)));
     Address free_end = object->address();
     if (free_end != free_start) {
       int size = static_cast<int>(free_end - free_start);
       if (free_space_mode == ZAP_FREE_SPACE) {
         memset(free_start, 0xcc, size);
       }
-      freed_bytes = space->UnaccountedFree(free_start, size);
-      max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+      if (free_list_mode == REBUILD_FREE_LIST) {
+        freed_bytes = space->UnaccountedFree(free_start, size);
+        max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+      } else {
+        p->heap()->CreateFillerObjectAt(free_start, size,
+                                        ClearRecordedSlots::kNo);
+      }
     }
     Map* map = object->synchronized_map();
     int size = object->SizeFromMap(map);
     if (sweeping_mode == SWEEP_AND_VISIT_LIVE_OBJECTS) {
       object->IterateBody(map->instance_type(), size, v);
     }
     if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list != NULL) {
       int new_region_start = SkipList::RegionNumber(free_end);
       int new_region_end =
           SkipList::RegionNumber(free_end + size - kPointerSize);
       if (new_region_start != curr_region || new_region_end != curr_region) {
         skip_list->AddObject(free_end, size);
         curr_region = new_region_end;
       }
     }
     free_start = free_end + size;
   }
 
   // Clear the mark bits of that page and reset live bytes count.
   Bitmap::Clear(p);
 
   if (free_start != p->area_end()) {
     int size = static_cast<int>(p->area_end() - free_start);
     if (free_space_mode == ZAP_FREE_SPACE) {
       memset(free_start, 0xcc, size);
     }
-    freed_bytes = space->UnaccountedFree(free_start, size);
-    max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+    if (free_list_mode == REBUILD_FREE_LIST) {
+      freed_bytes = space->UnaccountedFree(free_start, size);
+      max_freed_bytes = Max(freed_bytes, max_freed_bytes);
+    } else {
+      p->heap()->CreateFillerObjectAt(free_start, size,
+                                      ClearRecordedSlots::kNo);
+    }
   }
   p->concurrent_sweeping_state().SetValue(Page::kSweepingDone);
+  if (free_list_mode == IGNORE_FREE_LIST) return 0;
   return FreeList::GuaranteedAllocatable(static_cast<int>(max_freed_bytes));
 }
 
 void MarkCompactCollector::InvalidateCode(Code* code) {
   if (heap_->incremental_marking()->IsCompacting() &&
       !ShouldSkipEvacuationSlotRecording(code)) {
     DCHECK(compacting_);
 
     // If the object is white than no slots were recorded on it yet.
     MarkBit mark_bit = Marking::MarkBitFrom(code);
@@ skipping 95 matching lines @@
 void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
   TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_EVACUATE);
   Heap::RelocationLock relocation_lock(heap());
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_EVACUATE_COPY);
     EvacuationScope evacuation_scope(this);
 
     EvacuateNewSpacePrologue();
     EvacuatePagesInParallel();
-    EvacuateNewSpaceEpilogue();
     heap()->new_space()->set_age_mark(heap()->new_space()->top());
   }
 
   UpdatePointersAfterEvacuation();
 
   // Give pages that are queued to be freed back to the OS. Note that filtering
   // slots only handles old space (for unboxed doubles), and thus map space can
   // still contain stale pointers. We only free the chunks after pointer updates
   // to still have access to page headers.
   heap()->memory_allocator()->unmapper()->FreeQueuedChunks();
 
   {
     TRACE_GC(heap()->tracer(), GCTracer::Scope::MC_EVACUATE_CLEAN_UP);
 
+    for (Page* p : newspace_evacuation_candidates_) {
+      if (p->IsFlagSet(Page::PAGE_NEW_NEW_PROMOTION)) {
+        p->ClearFlag(Page::PAGE_NEW_NEW_PROMOTION);
+        sweeper().AddLatePage(p->owner()->identity(), p);
+      } else if (p->IsFlagSet(Page::PAGE_NEW_OLD_PROMOTION)) {
+        p->ClearFlag(Page::PAGE_NEW_OLD_PROMOTION);
+        p->ForAllFreeListCategories(
+            [](FreeListCategory* category) { DCHECK(!category->is_linked()); });
+        sweeper().AddLatePage(p->owner()->identity(), p);
+      }
+    }
+    newspace_evacuation_candidates_.Rewind(0);
+
     for (Page* p : evacuation_candidates_) {
       // Important: skip list should be cleared only after roots were updated
       // because root iteration traverses the stack and might have to find
       // code objects from non-updated pc pointing into evacuation candidate.
       SkipList* list = p->skip_list();
       if (list != NULL) list->Clear();
       if (p->IsFlagSet(Page::COMPACTION_WAS_ABORTED)) {
         sweeper().AddLatePage(p->owner()->identity(), p);
         p->ClearFlag(Page::COMPACTION_WAS_ABORTED);
       }
@@ skipping 74 matching lines @@
         // Update the corresponding slot.
         *slot = map_word.ToForwardingAddress();
       }
       // If the object was in from space before and is after executing the
       // callback in to space, the object is still live.
       // Unfortunately, we do not know about the slot. It could be in a
       // just freed free space object.
       if (heap->InToSpace(*slot)) {
         return KEEP_SLOT;
       }
+    } else if (heap->InToSpace(*slot)) {
+      // Slots can be in "to" space after a page has been moved. Since there is

[ulan, 2016/06/10 12:58:54]

DCHECK that the page has new_to_new promotion flag?

[Michael Lippautz, 2016/06/10 15:18:15]

Done.

+      // no forwarding information present we need to check the markbits to
+      // determine liveness.
+      if (Marking::IsBlack(
+              Marking::MarkBitFrom(reinterpret_cast<HeapObject*>(*slot))))
+        return KEEP_SLOT;
     } else {
       DCHECK(!heap->InNewSpace(*slot));
     }
     return REMOVE_SLOT;
   }
 };
 
 int NumberOfPointerUpdateTasks(int pages) {
   if (!FLAG_parallel_pointer_update) return 1;
   const int kMaxTasks = 4;
@@ skipping 12 matching lines @@
   job.Run(num_tasks, [](int i) { return 0; });
 }
 
 class ToSpacePointerUpdateJobTraits {
  public:
   typedef std::pair<Address, Address> PerPageData;
   typedef PointersUpdatingVisitor* PerTaskData;
 
   static bool ProcessPageInParallel(Heap* heap, PerTaskData visitor,
                                     MemoryChunk* chunk, PerPageData limits) {
+    if (chunk->IsFlagSet(Page::PAGE_NEW_NEW_PROMOTION)) {
+      // New->new promoted pages contain garbage so they require iteration
+      // using markbits.
+      ProcessPageInParallelVisitLive(heap, visitor, chunk, limits);
+    } else {
+      ProcessPageInParallelVisitAll(heap, visitor, chunk, limits);
+    }
+    return true;
+  }
+
+  static const bool NeedSequentialFinalization = false;
+  static void FinalizePageSequentially(Heap*, MemoryChunk*, bool, PerPageData) {
+  }
+
+ private:
+  static void ProcessPageInParallelVisitAll(Heap* heap, PerTaskData visitor,
+                                            MemoryChunk* chunk,
+                                            PerPageData limits) {
     for (Address cur = limits.first; cur < limits.second;) {
       HeapObject* object = HeapObject::FromAddress(cur);
       Map* map = object->map();
       int size = object->SizeFromMap(map);
       object->IterateBody(map->instance_type(), size, visitor);
       cur += size;
     }
-    return true;
   }
-  static const bool NeedSequentialFinalization = false;
-  static void FinalizePageSequentially(Heap*, MemoryChunk*, bool, PerPageData) {
+
+  static void ProcessPageInParallelVisitLive(Heap* heap, PerTaskData visitor,
+                                             MemoryChunk* chunk,
+                                             PerPageData limits) {
+    LiveObjectIterator<kBlackObjects> it(chunk);
+    HeapObject* object = NULL;
+    while ((object = it.Next()) != NULL) {
+      Map* map = object->map();
+      int size = object->SizeFromMap(map);
+      object->IterateBody(map->instance_type(), size, visitor);
+    }
   }
 };
 
 void UpdateToSpacePointersInParallel(Heap* heap, base::Semaphore* semaphore) {
   PageParallelJob<ToSpacePointerUpdateJobTraits> job(
       heap, heap->isolate()->cancelable_task_manager(), semaphore);
   Address space_start = heap->new_space()->bottom();
   Address space_end = heap->new_space()->top();
   NewSpacePageIterator it(space_start, space_end);
   while (it.has_next()) {
@@ skipping 55 matching lines @@
   heap()->memory_allocator()->unmapper()->FreeQueuedChunks();
 }
 
 int MarkCompactCollector::Sweeper::ParallelSweepSpace(AllocationSpace identity,
                                                       int required_freed_bytes,
                                                       int max_pages) {
   int max_freed = 0;
   int pages_freed = 0;
   Page* page = nullptr;
   while ((page = GetSweepingPageSafe(identity)) != nullptr) {
-    int freed = ParallelSweepPage(page, heap_->paged_space(identity));
+    int freed = ParallelSweepPage(page, identity);
     pages_freed += 1;
     DCHECK_GE(freed, 0);
     max_freed = Max(max_freed, freed);
     if ((required_freed_bytes) > 0 && (max_freed >= required_freed_bytes))
       return max_freed;
     if ((max_pages > 0) && (pages_freed >= max_pages)) return max_freed;
   }
   return max_freed;
 }
 
 int MarkCompactCollector::Sweeper::ParallelSweepPage(Page* page,
-                                                     PagedSpace* space) {
+                                                     AllocationSpace identity) {
   int max_freed = 0;
   if (page->mutex()->TryLock()) {
     // If this page was already swept in the meantime, we can return here.
     if (page->concurrent_sweeping_state().Value() != Page::kSweepingPending) {
       page->mutex()->Unlock();
       return 0;
     }
     page->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress);
-    if (space->identity() == OLD_SPACE) {
+    if (identity == NEW_SPACE) {
+      RawSweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST,
+               IGNORE_FREE_LIST, IGNORE_FREE_SPACE>(nullptr, page, nullptr);
+    } else if (identity == OLD_SPACE) {
       max_freed = RawSweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST,
-                           IGNORE_FREE_SPACE>(space, page, NULL);
-    } else if (space->identity() == CODE_SPACE) {
+                           REBUILD_FREE_LIST, IGNORE_FREE_SPACE>(
+          heap_->paged_space(identity), page, nullptr);
+    } else if (identity == CODE_SPACE) {
       max_freed = RawSweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, REBUILD_SKIP_LIST,
-                           IGNORE_FREE_SPACE>(space, page, NULL);
+                           REBUILD_FREE_LIST, IGNORE_FREE_SPACE>(
+          heap_->paged_space(identity), page, nullptr);
     } else {
       max_freed = RawSweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST,
-                           IGNORE_FREE_SPACE>(space, page, NULL);
+                           REBUILD_FREE_LIST, IGNORE_FREE_SPACE>(
+          heap_->paged_space(identity), page, nullptr);
     }
     {
       base::LockGuard<base::Mutex> guard(&mutex_);
-      swept_list_[space->identity()].Add(page);
+      swept_list_[identity].Add(page);
     }
     page->concurrent_sweeping_state().SetValue(Page::kSweepingDone);
     page->mutex()->Unlock();
   }
   return max_freed;
 }
 
 void MarkCompactCollector::Sweeper::AddPage(AllocationSpace space, Page* page) {
   DCHECK(!sweeping_in_progress_);
   PrepareToBeSweptPage(space, page);
   sweeping_list_[space].push_back(page);
 }
 
 void MarkCompactCollector::Sweeper::AddLatePage(AllocationSpace space,
                                                 Page* page) {
   DCHECK(sweeping_in_progress_);
   PrepareToBeSweptPage(space, page);
   late_pages_ = true;
   AddSweepingPageSafe(space, page);
 }
 
 void MarkCompactCollector::Sweeper::PrepareToBeSweptPage(AllocationSpace space,
                                                          Page* page) {
   page->concurrent_sweeping_state().SetValue(Page::kSweepingPending);
   int to_sweep = page->area_size() - page->LiveBytes();
-  heap_->paged_space(space)->accounting_stats_.ShrinkSpace(to_sweep);
+  if (space != NEW_SPACE)

[ulan, 2016/06/10 12:58:54]

So we are accounting the free space in new->new pages as live objects?

This might lead to corner case GCs where SizeOfObjects() before GC is smaller
than that after GC.

[Michael Lippautz, 2016/06/10 15:18:15]

Should not be the case, because SizeOfObjects in NewSpace is always computed
using allocatable area and number of pages. As far as I see it, in the worst
case SizeOfObjects would stay constant although before a GC "live bytes <
SizeOfObjects()" did hold. 

Is this a problem?

+    heap_->paged_space(space)->accounting_stats_.ShrinkSpace(to_sweep);
 }
 
 Page* MarkCompactCollector::Sweeper::GetSweepingPageSafe(
     AllocationSpace space) {
   base::LockGuard<base::Mutex> guard(&mutex_);
   Page* page = nullptr;
   if (!sweeping_list_[space].empty()) {
     page = sweeping_list_[space].front();
     sweeping_list_[space].pop_front();
   }
@@ skipping 43 matching lines @@
       continue;
     }
 
     if (p->IsFlagSet(Page::NEVER_ALLOCATE_ON_PAGE)) {
       // We need to sweep the page to get it into an iterable state again. Note
       // that this adds unusable memory into the free list that is later on
       // (in the free list) dropped again. Since we only use the flag for
       // testing this is fine.
       p->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress);
       Sweeper::RawSweep<Sweeper::SWEEP_ONLY, Sweeper::SWEEP_ON_MAIN_THREAD,
-                        Sweeper::IGNORE_SKIP_LIST, Sweeper::IGNORE_FREE_SPACE>(
-          space, p, nullptr);
+                        Sweeper::IGNORE_SKIP_LIST, Sweeper::IGNORE_FREE_LIST,
+                        Sweeper::IGNORE_FREE_SPACE>(space, p, nullptr);
       continue;
     }
 
     // One unused page is kept, all further are released before sweeping them.
     if (p->LiveBytes() == 0) {
       if (unused_page_present) {
         if (FLAG_gc_verbose) {
           PrintIsolate(isolate(), "sweeping: released page: %p",
                        static_cast<void*>(p));
         }
@@ skipping 85 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8