(十一) ConcurrentCopying

void ConcurrentCopying::RunPhases() {
  is_active_ = true;
  Thread* self = Thread::Current();
  thread_running_gc_ = self;
  Locks::mutator_lock_->AssertNotHeld(self);
  {
    ReaderMutexLock mu(self, *Locks::mutator_lock_);
    InitializePhase();
    // In case of forced evacuation, all regions are evacuated and hence no
    // need to compute live_bytes.
    if (use_generational_cc_ && !young_gen_ && !force_evacuate_all_) {
      MarkingPhase();
    }
  }
  if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) {
    // Switch to read barrier mark entrypoints before we gray the objects. This is required in case
    // a mutator sees a gray bit and dispatches on the entrypoint. (b/37876887).
    ActivateReadBarrierEntrypoints();
    // Gray dirty immune objects concurrently to reduce GC pause times. We re-process gray cards in
    // the pause.
    ReaderMutexLock mu(self, *Locks::mutator_lock_);
    GrayAllDirtyImmuneObjects();
  }
  FlipThreadRoots();
  {
    ReaderMutexLock mu(self, *Locks::mutator_lock_);
    CopyingPhase();
  }
  {
    ReaderMutexLock mu(self, *Locks::mutator_lock_);
    ReclaimPhase();
  }
  FinishPhase();
  is_active_ = false;
  thread_running_gc_ = nullptr;
}

void ConcurrentCopying::BindBitmaps() {
  Thread* self = Thread::Current();
  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
  // Mark all of the spaces we never collect as immune.
  for (const auto& space : heap_->GetContinuousSpaces()) {
    if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect ||
        space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect) {
      CHECK(space->IsZygoteSpace() || space->IsImageSpace());
      immune_spaces_.AddSpace(space);
    } else {
      CHECK(space == region_space_ || space == heap_->non_moving_space_);
      if (use_generational_cc_) {
        if (space == region_space_) {
          region_space_bitmap_ = region_space_->GetMarkBitmap();
        } else if (young_gen_ && space->IsContinuousMemMapAllocSpace()) {
          DCHECK_EQ(space->GetGcRetentionPolicy(), space::kGcRetentionPolicyAlwaysCollect);
          space->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap();
        }
        if (young_gen_) {
          // Age all of the cards for the region space so that we know which evac regions to scan.
          heap_->GetCardTable()->ModifyCardsAtomic(space->Begin(),
                                                   space->End(),
                                                   AgeCardVisitor(),
                                                   VoidFunctor());
        } else {
          // In a full-heap GC cycle, the card-table corresponding to region-space and
          // non-moving space can be cleared, because this cycle only needs to
          // capture writes during the marking phase of this cycle to catch
          // objects that skipped marking due to heap mutation. Furthermore,
          // if the next GC is a young-gen cycle, then it only needs writes to
          // be captured after the thread-flip of this GC cycle, as that is when
          // the young-gen for the next GC cycle starts getting populated.
          heap_->GetCardTable()->ClearCardRange(space->Begin(), space->Limit());
        }
      } else {
        if (space == region_space_) {
          // It is OK to clear the bitmap with mutators running since the only place it is read is
          // VisitObjects which has exclusion with CC.
          region_space_bitmap_ = region_space_->GetMarkBitmap();
          region_space_bitmap_->Clear();
        }
      }
    }
  }
  if (use_generational_cc_ && young_gen_) {
    for (const auto& space : GetHeap()->GetDiscontinuousSpaces()) {
      CHECK(space->IsLargeObjectSpace());
      space->AsLargeObjectSpace()->CopyLiveToMarked();
    }
  }
}