Merge "Add zygote space as its own space type."

22 files changed, 447 insertions, 299 deletions

diff --git a/runtime/Android.mk b/runtime/Android.mk
index c180b17..bab250c 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -66,6 +66,7 @@ LIBART_COMMON_SRC_FILES := \
 	gc/space/malloc_space.cc \
 	gc/space/rosalloc_space.cc \
 	gc/space/space.cc \
+	gc/space/zygote_space.cc \
 	hprof/hprof.cc \
 	image.cc \
 	indirect_reference_table.cc \
diff --git a/runtime/gc/accounting/space_bitmap.cc b/runtime/gc/accounting/space_bitmap.cc
index 99800fc..b831843 100644
--- a/runtime/gc/accounting/space_bitmap.cc
+++ b/runtime/gc/accounting/space_bitmap.cc
@@ -128,9 +128,9 @@ void SpaceBitmap::Walk(SpaceBitmap::Callback* callback, void* arg) {
 //
 // The callback is not permitted to increase the max of either bitmap.
 void SpaceBitmap::SweepWalk(const SpaceBitmap& live_bitmap,
-                           const SpaceBitmap& mark_bitmap,
-                           uintptr_t sweep_begin, uintptr_t sweep_end,
-                           SpaceBitmap::SweepCallback* callback, void* arg) {
+                            const SpaceBitmap& mark_bitmap,
+                            uintptr_t sweep_begin, uintptr_t sweep_end,
+                            SpaceBitmap::SweepCallback* callback, void* arg) {
   CHECK(live_bitmap.bitmap_begin_ != NULL);
   CHECK(mark_bitmap.bitmap_begin_ != NULL);
   CHECK_EQ(live_bitmap.heap_begin_, mark_bitmap.heap_begin_);
diff --git a/runtime/gc/collector/mark_sweep.cc b/runtime/gc/collector/mark_sweep.cc
index 5d450a7..862d06f 100644
--- a/runtime/gc/collector/mark_sweep.cc
+++ b/runtime/gc/collector/mark_sweep.cc
@@ -89,7 +89,8 @@ constexpr bool kCheckLocks = kDebugLocking;
 void MarkSweep::ImmuneSpace(space::ContinuousSpace* space) {
   // Bind live to mark bitmap if necessary.
   if (space->GetLiveBitmap() != space->GetMarkBitmap()) {
-    BindLiveToMarkBitmap(space);
+    CHECK(space->IsContinuousMemMapAllocSpace());
+    space->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap();
   }
 
   // Add the space to the immune region.
@@ -143,11 +144,6 @@ MarkSweep::MarkSweep(Heap* heap, bool is_concurrent, const std::string& name_pre
       mark_stack_(NULL),
       immune_begin_(NULL),
       immune_end_(NULL),
-      soft_reference_list_(NULL),
-      weak_reference_list_(NULL),
-      finalizer_reference_list_(NULL),
-      phantom_reference_list_(NULL),
-      cleared_reference_list_(NULL),
       live_stack_freeze_size_(0),
       gc_barrier_(new Barrier(0)),
       large_object_lock_("mark sweep large object lock", kMarkSweepLargeObjectLock),
@@ -161,11 +157,6 @@ void MarkSweep::InitializePhase() {
   mark_stack_ = heap_->mark_stack_.get();
   DCHECK(mark_stack_ != nullptr);
   SetImmuneRange(nullptr, nullptr);
-  soft_reference_list_ = nullptr;
-  weak_reference_list_ = nullptr;
-  finalizer_reference_list_ = nullptr;
-  phantom_reference_list_ = nullptr;
-  cleared_reference_list_ = nullptr;
   class_count_ = 0;
   array_count_ = 0;
   other_count_ = 0;
@@ -347,7 +338,8 @@ void MarkSweep::ReclaimPhase() {
     timings_.EndSplit();
 
     // Unbind the live and mark bitmaps.
-    UnBindBitmaps();
+    TimingLogger::ScopedSplit split("UnBindBitmaps", &timings_);
+    GetHeap()->UnBindBitmaps();
   }
 }
 
@@ -589,14 +581,6 @@ void MarkSweep::MarkConcurrentRoots() {
   timings_.EndSplit();
 }
 
-void MarkSweep::BindLiveToMarkBitmap(space::ContinuousSpace* space) {
-  CHECK(space->IsMallocSpace());
-  space::MallocSpace* alloc_space = space->AsMallocSpace();
-  accounting::SpaceBitmap* live_bitmap = space->GetLiveBitmap();
-  accounting::SpaceBitmap* mark_bitmap = alloc_space->BindLiveToMarkBitmap();
-  GetHeap()->GetMarkBitmap()->ReplaceBitmap(mark_bitmap, live_bitmap);
-}
-
 class ScanObjectVisitor {
  public:
   explicit ScanObjectVisitor(MarkSweep* const mark_sweep) ALWAYS_INLINE
@@ -893,14 +877,8 @@ class RecursiveMarkTask : public MarkStackTask<false> {
 // recursively marks until the mark stack is emptied.
 void MarkSweep::RecursiveMark() {
   TimingLogger::ScopedSplit split("RecursiveMark", &timings_);
-  // RecursiveMark will build the lists of known instances of the Reference classes.
-  // See DelayReferenceReferent for details.
-  CHECK(soft_reference_list_ == NULL);
-  CHECK(weak_reference_list_ == NULL);
-  CHECK(finalizer_reference_list_ == NULL);
-  CHECK(phantom_reference_list_ == NULL);
-  CHECK(cleared_reference_list_ == NULL);
-
+  // RecursiveMark will build the lists of known instances of the Reference classes. See
+  // DelayReferenceReferent for details.
   if (kUseRecursiveMark) {
     const bool partial = GetGcType() == kGcTypePartial;
     ScanObjectVisitor scan_visitor(this);
@@ -1146,13 +1124,13 @@ void MarkSweep::Sweep(bool swap_bitmaps) {
   DCHECK(mark_stack_->IsEmpty());
   TimingLogger::ScopedSplit("Sweep", &timings_);
   for (const auto& space : GetHeap()->GetContinuousSpaces()) {
-    if (space->IsMallocSpace()) {
-      space::MallocSpace* malloc_space = space->AsMallocSpace();
+    if (space->IsContinuousMemMapAllocSpace()) {
+      space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
       TimingLogger::ScopedSplit split(
-          malloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", &timings_);
+          alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepMallocSpace", &timings_);
       size_t freed_objects = 0;
       size_t freed_bytes = 0;
-      malloc_space->Sweep(swap_bitmaps, &freed_objects, &freed_bytes);
+      alloc_space->Sweep(swap_bitmaps, &freed_objects, &freed_bytes);
       heap_->RecordFree(freed_objects, freed_bytes);
       freed_objects_.FetchAndAdd(freed_objects);
       freed_bytes_.FetchAndAdd(freed_bytes);
@@ -1278,23 +1256,6 @@ inline bool MarkSweep::IsMarked(const Object* object) const
   return heap_->GetMarkBitmap()->Test(object);
 }
 
-void MarkSweep::UnBindBitmaps() {
-  TimingLogger::ScopedSplit split("UnBindBitmaps", &timings_);
-  for (const auto& space : GetHeap()->GetContinuousSpaces()) {
-    if (space->IsMallocSpace()) {
-      space::MallocSpace* alloc_space = space->AsMallocSpace();
-      if (alloc_space->temp_bitmap_.get() != NULL) {
-        // At this point, the temp_bitmap holds our old mark bitmap.
-        accounting::SpaceBitmap* new_bitmap = alloc_space->temp_bitmap_.release();
-        GetHeap()->GetMarkBitmap()->ReplaceBitmap(alloc_space->mark_bitmap_.get(), new_bitmap);
-        CHECK_EQ(alloc_space->mark_bitmap_.release(), alloc_space->live_bitmap_.get());
-        alloc_space->mark_bitmap_.reset(new_bitmap);
-        DCHECK(alloc_space->temp_bitmap_.get() == NULL);
-      }
-    }
-  }
-}
-
 void MarkSweep::FinishPhase() {
   TimingLogger::ScopedSplit split("FinishPhase", &timings_);
   // Can't enqueue references if we hold the mutator lock.
diff --git a/runtime/gc/collector/mark_sweep.h b/runtime/gc/collector/mark_sweep.h
index e2eafb5..0c27a3b 100644
--- a/runtime/gc/collector/mark_sweep.h
+++ b/runtime/gc/collector/mark_sweep.h
@@ -118,12 +118,6 @@ class MarkSweep : public GarbageCollector {
   // the image. Mark that portion of the heap as immune.
   virtual void BindBitmaps() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void BindLiveToMarkBitmap(space::ContinuousSpace* space)
-      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
-
-  void UnBindBitmaps()
-      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
-
   // Builds a mark stack with objects on dirty cards and recursively mark until it empties.
   void RecursiveMarkDirtyObjects(bool paused, byte minimum_age)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
@@ -151,10 +145,6 @@ class MarkSweep : public GarbageCollector {
   void SweepArray(accounting::ObjectStack* allocation_stack_, bool swap_bitmaps)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
-  mirror::Object* GetClearedReferences() {
-    return cleared_reference_list_;
-  }
-
   // Blackens an object.
   void ScanObject(mirror::Object* obj)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
@@ -346,12 +336,6 @@ class MarkSweep : public GarbageCollector {
   mirror::Object* immune_begin_;
   mirror::Object* immune_end_;
 
-  mirror::Object* soft_reference_list_;
-  mirror::Object* weak_reference_list_;
-  mirror::Object* finalizer_reference_list_;
-  mirror::Object* phantom_reference_list_;
-  mirror::Object* cleared_reference_list_;
-
   // Parallel finger.
   AtomicInteger atomic_finger_;
   // Number of classes scanned, if kCountScannedTypes.
diff --git a/runtime/gc/collector/semi_space.cc b/runtime/gc/collector/semi_space.cc
index a273e5a..625f869 100644
--- a/runtime/gc/collector/semi_space.cc
+++ b/runtime/gc/collector/semi_space.cc
@@ -67,7 +67,8 @@ static constexpr bool kResetFromSpace = true;
 void SemiSpace::ImmuneSpace(space::ContinuousSpace* space) {
   // Bind live to mark bitmap if necessary.
   if (space->GetLiveBitmap() != space->GetMarkBitmap()) {
-    BindLiveToMarkBitmap(space);
+    CHECK(space->IsContinuousMemMapAllocSpace());
+    space->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap();
   }
   // Add the space to the immune region.
   if (immune_begin_ == nullptr) {
@@ -98,12 +99,13 @@ void SemiSpace::ImmuneSpace(space::ContinuousSpace* space) {
 
 void SemiSpace::BindBitmaps() {
   timings_.StartSplit("BindBitmaps");
-  WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
+  WriterMutexLock mu(self_, *Locks::heap_bitmap_lock_);
   // Mark all of the spaces we never collect as immune.
   for (const auto& space : GetHeap()->GetContinuousSpaces()) {
     if (space->GetLiveBitmap() != nullptr) {
       if (space == to_space_) {
-        BindLiveToMarkBitmap(to_space_);
+        CHECK(to_space_->IsContinuousMemMapAllocSpace());
+        to_space_->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap();
       } else if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect
                  || space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect
                  // Add the main free list space and the non-moving
@@ -179,8 +181,7 @@ void SemiSpace::MarkingPhase() {
       VLOG(heap) << "Bump pointer space only collection";
     }
   }
-  Thread* self = Thread::Current();
-  Locks::mutator_lock_->AssertExclusiveHeld(self);
+  Locks::mutator_lock_->AssertExclusiveHeld(self_);
   TimingLogger::ScopedSplit split("MarkingPhase", &timings_);
   // Need to do this with mutators paused so that somebody doesn't accidentally allocate into the
   // wrong space.
@@ -208,7 +209,7 @@ void SemiSpace::MarkingPhase() {
   // the live stack during the recursive mark.
   timings_.NewSplit("SwapStacks");
   heap_->SwapStacks();
-  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
+  WriterMutexLock mu(self_, *Locks::heap_bitmap_lock_);
   MarkRoots();
   // Mark roots of immune spaces.
   UpdateAndMarkModUnion();
@@ -309,10 +310,9 @@ void SemiSpace::MarkReachableObjects() {
 
 void SemiSpace::ReclaimPhase() {
   TimingLogger::ScopedSplit split("ReclaimPhase", &timings_);
-  Thread* self = Thread::Current();
-  ProcessReferences(self);
+  ProcessReferences(self_);
   {
-    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
+    ReaderMutexLock mu(self_, *Locks::heap_bitmap_lock_);
     SweepSystemWeaks();
   }
   // Record freed memory.
@@ -333,7 +333,7 @@ void SemiSpace::ReclaimPhase() {
   timings_.EndSplit();
 
   {
-    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
+    WriterMutexLock mu(self_, *Locks::heap_bitmap_lock_);
     // Reclaim unmarked objects.
     Sweep(false);
     // Swap the live and mark bitmaps for each space which we modified space. This is an
@@ -343,7 +343,8 @@ void SemiSpace::ReclaimPhase() {
     SwapBitmaps();
     timings_.EndSplit();
     // Unbind the live and mark bitmaps.
-    UnBindBitmaps();
+    TimingLogger::ScopedSplit split("UnBindBitmaps", &timings_);
+    GetHeap()->UnBindBitmaps();
   }
   // Release the memory used by the from space.
   if (kResetFromSpace) {
@@ -534,14 +535,6 @@ void SemiSpace::MarkRoots() {
   timings_.EndSplit();
 }
 
-void SemiSpace::BindLiveToMarkBitmap(space::ContinuousSpace* space) {
-  CHECK(space->IsMallocSpace());
-  space::MallocSpace* alloc_space = space->AsMallocSpace();
-  accounting::SpaceBitmap* live_bitmap = space->GetLiveBitmap();
-  accounting::SpaceBitmap* mark_bitmap = alloc_space->BindLiveToMarkBitmap();
-  GetHeap()->GetMarkBitmap()->ReplaceBitmap(mark_bitmap, live_bitmap);
-}
-
 mirror::Object* SemiSpace::MarkedForwardingAddressCallback(Object* object, void* arg) {
   return reinterpret_cast<SemiSpace*>(arg)->GetMarkedForwardAddress(object);
 }
@@ -552,7 +545,7 @@ void SemiSpace::SweepSystemWeaks() {
   timings_.EndSplit();
 }
 
-bool SemiSpace::ShouldSweepSpace(space::MallocSpace* space) const {
+bool SemiSpace::ShouldSweepSpace(space::ContinuousSpace* space) const {
   return space != from_space_ && space != to_space_ && !IsImmuneSpace(space);
 }
 
@@ -560,16 +553,16 @@ void SemiSpace::Sweep(bool swap_bitmaps) {
   DCHECK(mark_stack_->IsEmpty());
   TimingLogger::ScopedSplit("Sweep", &timings_);
   for (const auto& space : GetHeap()->GetContinuousSpaces()) {
-    if (space->IsMallocSpace()) {
-      space::MallocSpace* malloc_space = space->AsMallocSpace();
-      if (!ShouldSweepSpace(malloc_space)) {
+    if (space->IsContinuousMemMapAllocSpace()) {
+      space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
+      if (!ShouldSweepSpace(alloc_space)) {
         continue;
       }
       TimingLogger::ScopedSplit split(
-          malloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", &timings_);
+          alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", &timings_);
       size_t freed_objects = 0;
       size_t freed_bytes = 0;
-      malloc_space->Sweep(swap_bitmaps, &freed_objects, &freed_bytes);
+      alloc_space->Sweep(swap_bitmaps, &freed_objects, &freed_bytes);
       heap_->RecordFree(freed_objects, freed_bytes);
       freed_objects_.FetchAndAdd(freed_objects);
       freed_bytes_.FetchAndAdd(freed_bytes);
@@ -664,20 +657,6 @@ inline Object* SemiSpace::GetMarkedForwardAddress(mirror::Object* obj) const
   return heap_->GetMarkBitmap()->Test(obj) ? obj : nullptr;
 }
 
-void SemiSpace::UnBindBitmaps() {
-  TimingLogger::ScopedSplit split("UnBindBitmaps", &timings_);
-  for (const auto& space : GetHeap()->GetContinuousSpaces()) {
-    if (space->IsMallocSpace()) {
-      space::MallocSpace* alloc_space = space->AsMallocSpace();
-      if (alloc_space->HasBoundBitmaps()) {
-        alloc_space->UnBindBitmaps();
-        heap_->GetMarkBitmap()->ReplaceBitmap(alloc_space->GetLiveBitmap(),
-                                              alloc_space->GetMarkBitmap());
-      }
-    }
-  }
-}
-
 void SemiSpace::SetToSpace(space::ContinuousMemMapAllocSpace* to_space) {
   DCHECK(to_space != nullptr);
   to_space_ = to_space;
@@ -690,7 +669,6 @@ void SemiSpace::SetFromSpace(space::ContinuousMemMapAllocSpace* from_space) {
 
 void SemiSpace::FinishPhase() {
   TimingLogger::ScopedSplit split("FinishPhase", &timings_);
-  // Can't enqueue references if we hold the mutator lock.
   Heap* heap = GetHeap();
   timings_.NewSplit("PostGcVerification");
   heap->PostGcVerification(this);
diff --git a/runtime/gc/collector/semi_space.h b/runtime/gc/collector/semi_space.h
index bf129a3..f81a7c2 100644
--- a/runtime/gc/collector/semi_space.h
+++ b/runtime/gc/collector/semi_space.h
@@ -114,9 +114,6 @@ class SemiSpace : public GarbageCollector {
   // the image. Mark that portion of the heap as immune.
   virtual void BindBitmaps() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void BindLiveToMarkBitmap(space::ContinuousSpace* space)
-      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
-
   void UnBindBitmaps()
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
@@ -171,7 +168,7 @@ class SemiSpace : public GarbageCollector {
   void ResizeMarkStack(size_t new_size);
 
   // Returns true if we should sweep the space.
-  virtual bool ShouldSweepSpace(space::MallocSpace* space) const;
+  virtual bool ShouldSweepSpace(space::ContinuousSpace* space) const;
 
   // Returns how many threads we should use for the current GC phase based on if we are paused,
   // whether or not we care about pauses.
diff --git a/runtime/gc/collector/sticky_mark_sweep.cc b/runtime/gc/collector/sticky_mark_sweep.cc
index c562e8c..30f3753 100644
--- a/runtime/gc/collector/sticky_mark_sweep.cc
+++ b/runtime/gc/collector/sticky_mark_sweep.cc
@@ -40,10 +40,10 @@ void StickyMarkSweep::BindBitmaps() {
   for (const auto& space : GetHeap()->GetContinuousSpaces()) {
     if (space->IsMallocSpace() &&
         space->GetGcRetentionPolicy() == space::kGcRetentionPolicyAlwaysCollect) {
-      BindLiveToMarkBitmap(space);
+      DCHECK(space->IsContinuousMemMapAllocSpace());
+      space->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap();
     }
   }
-
   GetHeap()->GetLargeObjectsSpace()->CopyLiveToMarked();
 }
 
diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 06793bf..fd98e29 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -44,6 +44,7 @@
 #include "gc/space/large_object_space.h"
 #include "gc/space/rosalloc_space-inl.h"
 #include "gc/space/space-inl.h"
+#include "gc/space/zygote_space.h"
 #include "heap-inl.h"
 #include "image.h"
 #include "invoke_arg_array_builder.h"
@@ -485,7 +486,6 @@ void Heap::RemoveSpace(space::Space* space) {
     DCHECK(it != alloc_spaces_.end());
     alloc_spaces_.erase(it);
   }
-  delete space;
 }
 
 void Heap::RegisterGCAllocation(size_t bytes) {
@@ -605,7 +605,7 @@ struct SoftReferenceArgs {
 };
 
 mirror::Object* Heap::PreserveSoftReferenceCallback(mirror::Object* obj, void* arg) {
-  SoftReferenceArgs* args  = reinterpret_cast<SoftReferenceArgs*>(arg);
+  SoftReferenceArgs* args = reinterpret_cast<SoftReferenceArgs*>(arg);
   // TODO: Not preserve all soft references.
   return args->recursive_mark_callback_(obj, args->arg_);
 }
@@ -749,7 +749,7 @@ void Heap::Trim() {
   uint64_t total_alloc_space_size = 0;
   uint64_t managed_reclaimed = 0;
   for (const auto& space : continuous_spaces_) {
-    if (space->IsMallocSpace() && !space->IsZygoteSpace()) {
+    if (space->IsMallocSpace()) {
       gc::space::MallocSpace* alloc_space = space->AsMallocSpace();
       total_alloc_space_size += alloc_space->Size();
       managed_reclaimed += alloc_space->Trim();
@@ -1198,8 +1198,10 @@ void Heap::TransitionCollector(CollectorType collector_type) {
       DCHECK(allocator_mem_map_.get() == nullptr);
       allocator_mem_map_.reset(main_space_->ReleaseMemMap());
       madvise(main_space_->Begin(), main_space_->Size(), MADV_DONTNEED);
-      // RemoveSpace deletes the removed space.
-      RemoveSpace(main_space_);
+      // RemoveSpace does not delete the removed space.
+      space::Space* old_space = main_space_;
+      RemoveSpace(old_space);
+      delete old_space;
       break;
     }
     case kCollectorTypeMS:
@@ -1349,7 +1351,7 @@ class ZygoteCompactingCollector : public collector::SemiSpace {
     }
   }
 
-  virtual bool ShouldSweepSpace(space::MallocSpace* space) const {
+  virtual bool ShouldSweepSpace(space::ContinuousSpace* space) const {
     // Don't sweep any spaces since we probably blasted the internal accounting of the free list
     // allocator.
     return false;
@@ -1389,6 +1391,17 @@ class ZygoteCompactingCollector : public collector::SemiSpace {
   }
 };
 
+void Heap::UnBindBitmaps() {
+  for (const auto& space : GetContinuousSpaces()) {
+    if (space->IsContinuousMemMapAllocSpace()) {
+      space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
+      if (alloc_space->HasBoundBitmaps()) {
+        alloc_space->UnBindBitmaps();
+      }
+    }
+  }
+}
+
 void Heap::PreZygoteFork() {
   static Mutex zygote_creation_lock_("zygote creation lock", kZygoteCreationLock);
   Thread* self = Thread::Current();
@@ -1424,30 +1437,28 @@ void Heap::PreZygoteFork() {
     non_moving_space_->SetLimit(target_space.Limit());
     VLOG(heap) << "Zygote size " << non_moving_space_->Size() << " bytes";
   }
+  // Save the old space so that we can remove it after we complete creating the zygote space.
+  space::MallocSpace* old_alloc_space = non_moving_space_;
   // Turn the current alloc space into a zygote space and obtain the new alloc space composed of
-  // the remaining available heap memory.
-  space::MallocSpace* zygote_space = non_moving_space_;
-  main_space_ = non_moving_space_->CreateZygoteSpace("alloc space", low_memory_mode_);
+  // the remaining available space.
+  // Remove the old space before creating the zygote space since creating the zygote space sets
+  // the old alloc space's bitmaps to nullptr.
+  RemoveSpace(old_alloc_space);
+  space::ZygoteSpace* zygote_space = old_alloc_space->CreateZygoteSpace("alloc space",
+                                                                        low_memory_mode_,
+                                                                        &main_space_);
+  delete old_alloc_space;
+  CHECK(zygote_space != nullptr) << "Failed creating zygote space";
+  AddSpace(zygote_space, false);
+  CHECK(main_space_ != nullptr);
   if (main_space_->IsRosAllocSpace()) {
     rosalloc_space_ = main_space_->AsRosAllocSpace();
   } else if (main_space_->IsDlMallocSpace()) {
     dlmalloc_space_ = main_space_->AsDlMallocSpace();
   }
   main_space_->SetFootprintLimit(main_space_->Capacity());
-  // Change the GC retention policy of the zygote space to only collect when full.
-  zygote_space->SetGcRetentionPolicy(space::kGcRetentionPolicyFullCollect);
   AddSpace(main_space_);
   have_zygote_space_ = true;
-  // Remove the zygote space from alloc_spaces_ array since not doing so causes crashes in
-  // GetObjectsAllocated. This happens because the bin packing blows away the internal accounting
-  // stored in between objects.
-  if (zygote_space->IsAllocSpace()) {
-    // TODO: Refactor zygote spaces to be a new space type to avoid more of these types of issues.
-    auto it = std::find(alloc_spaces_.begin(), alloc_spaces_.end(), zygote_space->AsAllocSpace());
-    CHECK(it != alloc_spaces_.end());
-    alloc_spaces_.erase(it);
-    zygote_space->InvalidateAllocator();
-  }
   // Create the zygote space mod union table.
   accounting::ModUnionTable* mod_union_table =
       new accounting::ModUnionTableCardCache("zygote space mod-union table", this, zygote_space);
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 52138d1..fd7a614 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -467,6 +467,9 @@ class Heap {
   void MarkAllocStackAsLive(accounting::ObjectStack* stack)
       EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
 
+  // Unbind any bound bitmaps.
+  void UnBindBitmaps() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
   // DEPRECATED: Should remove in "near" future when support for multiple image spaces is added.
   // Assumes there is only one image space.
   space::ImageSpace* GetImageSpace() const;
diff --git a/runtime/gc/space/dlmalloc_space.cc b/runtime/gc/space/dlmalloc_space.cc
index 981af53..9ae6a33 100644
--- a/runtime/gc/space/dlmalloc_space.cc
+++ b/runtime/gc/space/dlmalloc_space.cc
@@ -287,6 +287,7 @@ uint64_t DlMallocSpace::GetObjectsAllocated() {
 }
 
 void DlMallocSpace::Clear() {
+  // TODO: Delete and create new mspace here.
   madvise(GetMemMap()->Begin(), GetMemMap()->Size(), MADV_DONTNEED);
   GetLiveBitmap()->Clear();
   GetMarkBitmap()->Clear();
diff --git a/runtime/gc/space/dlmalloc_space.h b/runtime/gc/space/dlmalloc_space.h
index 671d2b2..24308f7 100644
--- a/runtime/gc/space/dlmalloc_space.h
+++ b/runtime/gc/space/dlmalloc_space.h
@@ -97,10 +97,6 @@ class DlMallocSpace : public MallocSpace {
 
   virtual void Clear();
 
-  virtual void InvalidateAllocator() {
-    mspace_for_alloc_ = nullptr;
-  }
-
   virtual bool IsDlMallocSpace() const {
     return true;
   }
diff --git a/runtime/gc/space/image_space.h b/runtime/gc/space/image_space.h
index 78a83c9..c3f0ae6 100644
--- a/runtime/gc/space/image_space.h
+++ b/runtime/gc/space/image_space.h
@@ -29,10 +29,6 @@ namespace space {
 // An image space is a space backed with a memory mapped image.
 class ImageSpace : public MemMapSpace {
  public:
-  bool CanAllocateInto() const {
-    return false;
-  }
-
   SpaceType GetType() const {
     return kSpaceTypeImageSpace;
   }
@@ -75,6 +71,10 @@ class ImageSpace : public MemMapSpace {
 
   void Dump(std::ostream& os) const;
 
+  // Sweeping image spaces is a NOP.
+  void Sweep(bool /* swap_bitmaps */, size_t* /* freed_objects */, size_t* /* freed_bytes */) {
+  }
+
  private:
   // Tries to initialize an ImageSpace from the given image path,
   // returning NULL on error.
diff --git a/runtime/gc/space/malloc_space.cc b/runtime/gc/space/malloc_space.cc
index 2b2b26e..9ca4eac 100644
--- a/runtime/gc/space/malloc_space.cc
+++ b/runtime/gc/space/malloc_space.cc
@@ -19,6 +19,8 @@
 #include "gc/accounting/card_table-inl.h"
 #include "gc/accounting/space_bitmap-inl.h"
 #include "gc/heap.h"
+#include "gc/space/space-inl.h"
+#include "gc/space/zygote_space.h"
 #include "mirror/class-inl.h"
 #include "mirror/object-inl.h"
 #include "runtime.h"
@@ -33,22 +35,27 @@ namespace space {
 size_t MallocSpace::bitmap_index_ = 0;
 
 MallocSpace::MallocSpace(const std::string& name, MemMap* mem_map,
-                         byte* begin, byte* end, byte* limit, size_t growth_limit)
+                         byte* begin, byte* end, byte* limit, size_t growth_limit,
+                         bool create_bitmaps)
     : ContinuousMemMapAllocSpace(name, mem_map, begin, end, limit, kGcRetentionPolicyAlwaysCollect),
       recent_free_pos_(0), lock_("allocation space lock", kAllocSpaceLock),
       growth_limit_(growth_limit) {
-  size_t bitmap_index = bitmap_index_++;
-  static const uintptr_t kGcCardSize = static_cast<uintptr_t>(accounting::CardTable::kCardSize);
-  CHECK(IsAligned<kGcCardSize>(reinterpret_cast<uintptr_t>(mem_map->Begin())));
-  CHECK(IsAligned<kGcCardSize>(reinterpret_cast<uintptr_t>(mem_map->End())));
-  live_bitmap_.reset(accounting::SpaceBitmap::Create(
-      StringPrintf("allocspace %s live-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
-      Begin(), Capacity()));
-  DCHECK(live_bitmap_.get() != NULL) << "could not create allocspace live bitmap #" << bitmap_index;
-  mark_bitmap_.reset(accounting::SpaceBitmap::Create(
-      StringPrintf("allocspace %s mark-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
-      Begin(), Capacity()));
-  DCHECK(live_bitmap_.get() != NULL) << "could not create allocspace mark bitmap #" << bitmap_index;
+  if (create_bitmaps) {
+    size_t bitmap_index = bitmap_index_++;
+    static const uintptr_t kGcCardSize = static_cast<uintptr_t>(accounting::CardTable::kCardSize);
+    CHECK(IsAligned<kGcCardSize>(reinterpret_cast<uintptr_t>(mem_map->Begin())));
+    CHECK(IsAligned<kGcCardSize>(reinterpret_cast<uintptr_t>(mem_map->End())));
+    live_bitmap_.reset(accounting::SpaceBitmap::Create(
+        StringPrintf("allocspace %s live-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
+        Begin(), Capacity()));
+    DCHECK(live_bitmap_.get() != NULL) << "could not create allocspace live bitmap #"
+        << bitmap_index;
+    mark_bitmap_.reset(accounting::SpaceBitmap::Create(
+        StringPrintf("allocspace %s mark-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
+        Begin(), Capacity()));
+    DCHECK(live_bitmap_.get() != NULL) << "could not create allocspace mark bitmap #"
+        << bitmap_index;
+  }
   for (auto& freed : recent_freed_objects_) {
     freed.first = nullptr;
     freed.second = nullptr;
@@ -154,29 +161,8 @@ void* MallocSpace::MoreCore(intptr_t increment) {
   return original_end;
 }
 
-// Returns the old mark bitmap.
-accounting::SpaceBitmap* MallocSpace::BindLiveToMarkBitmap() {
-  accounting::SpaceBitmap* live_bitmap = GetLiveBitmap();
-  accounting::SpaceBitmap* mark_bitmap = mark_bitmap_.release();
-  temp_bitmap_.reset(mark_bitmap);
-  mark_bitmap_.reset(live_bitmap);
-  return mark_bitmap;
-}
-
-bool MallocSpace::HasBoundBitmaps() const {
-  return temp_bitmap_.get() != nullptr;
-}
-
-void MallocSpace::UnBindBitmaps() {
-  CHECK(HasBoundBitmaps());
-  // At this point, the temp_bitmap holds our old mark bitmap.
-  accounting::SpaceBitmap* new_bitmap = temp_bitmap_.release();
-  CHECK_EQ(mark_bitmap_.release(), live_bitmap_.get());
-  mark_bitmap_.reset(new_bitmap);
-  DCHECK(temp_bitmap_.get() == NULL);
-}
-
-MallocSpace* MallocSpace::CreateZygoteSpace(const char* alloc_space_name, bool low_memory_mode) {
+ZygoteSpace* MallocSpace::CreateZygoteSpace(const char* alloc_space_name, bool low_memory_mode,
+                                            MallocSpace** out_malloc_space) {
   // For RosAlloc, revoke thread local runs before creating a new
   // alloc space so that we won't mix thread local runs from different
   // alloc spaces.
@@ -220,15 +206,23 @@ MallocSpace* MallocSpace::CreateZygoteSpace(const char* alloc_space_name, bool l
   if (capacity - initial_size > 0) {
     CHECK_MEMORY_CALL(mprotect, (end, capacity - initial_size, PROT_NONE), alloc_space_name);
   }
-  MallocSpace* alloc_space = CreateInstance(alloc_space_name, mem_map.release(), allocator,
-                                            end_, end, limit_, growth_limit);
+  *out_malloc_space = CreateInstance(alloc_space_name, mem_map.release(), allocator, end_, end,
+                                     limit_, growth_limit);
   SetLimit(End());
   live_bitmap_->SetHeapLimit(reinterpret_cast<uintptr_t>(End()));
   CHECK_EQ(live_bitmap_->HeapLimit(), reinterpret_cast<uintptr_t>(End()));
   mark_bitmap_->SetHeapLimit(reinterpret_cast<uintptr_t>(End()));
   CHECK_EQ(mark_bitmap_->HeapLimit(), reinterpret_cast<uintptr_t>(End()));
-  VLOG(heap) << "zygote space creation done";
-  return alloc_space;
+
+  // Create the actual zygote space.
+  ZygoteSpace* zygote_space = ZygoteSpace::Create("Zygote space", ReleaseMemMap(),
+                                                  live_bitmap_.release(), mark_bitmap_.release());
+  if (UNLIKELY(zygote_space == nullptr)) {
+    VLOG(heap) << "Failed creating zygote space from space " << GetName();
+  } else {
+    VLOG(heap) << "zygote space creation done";
+  }
+  return zygote_space;
 }
 
 void MallocSpace::Dump(std::ostream& os) const {
@@ -239,24 +233,16 @@ void MallocSpace::Dump(std::ostream& os) const {
       << ",name=\"" << GetName() << "\"]";
 }
 
-struct SweepCallbackContext {
-  bool swap_bitmaps;
-  Heap* heap;
-  space::MallocSpace* space;
-  Thread* self;
-  size_t freed_objects;
-  size_t freed_bytes;
-};
-
-static void SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
+void MallocSpace::SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
   SweepCallbackContext* context = static_cast<SweepCallbackContext*>(arg);
-  space::AllocSpace* space = context->space;
+  DCHECK(context->space->IsMallocSpace());
+  space::MallocSpace* space = context->space->AsMallocSpace();
   Thread* self = context->self;
   Locks::heap_bitmap_lock_->AssertExclusiveHeld(self);
   // If the bitmaps aren't swapped we need to clear the bits since the GC isn't going to re-swap
   // the bitmaps as an optimization.
   if (!context->swap_bitmaps) {
-    accounting::SpaceBitmap* bitmap = context->space->GetLiveBitmap();
+    accounting::SpaceBitmap* bitmap = space->GetLiveBitmap();
     for (size_t i = 0; i < num_ptrs; ++i) {
       bitmap->Clear(ptrs[i]);
     }
@@ -268,54 +254,6 @@ static void SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
   context->freed_bytes += space->FreeList(self, num_ptrs, ptrs);
 }
 
-static void ZygoteSweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
-  SweepCallbackContext* context = static_cast<SweepCallbackContext*>(arg);
-  Locks::heap_bitmap_lock_->AssertExclusiveHeld(context->self);
-  accounting::CardTable* card_table = context->heap->GetCardTable();
-  // If the bitmaps aren't swapped we need to clear the bits since the GC isn't going to re-swap
-  // the bitmaps as an optimization.
-  if (!context->swap_bitmaps) {
-    accounting::SpaceBitmap* bitmap = context->space->GetLiveBitmap();
-    for (size_t i = 0; i < num_ptrs; ++i) {
-      bitmap->Clear(ptrs[i]);
-    }
-  }
-  // We don't free any actual memory to avoid dirtying the shared zygote pages.
-  for (size_t i = 0; i < num_ptrs; ++i) {
-    // Need to mark the card since this will update the mod-union table next GC cycle.
-    card_table->MarkCard(ptrs[i]);
-  }
-}
-
-void MallocSpace::Sweep(bool swap_bitmaps, size_t* freed_objects, size_t* freed_bytes) {
-  DCHECK(freed_objects != nullptr);
-  DCHECK(freed_bytes != nullptr);
-  accounting::SpaceBitmap* live_bitmap = GetLiveBitmap();
-  accounting::SpaceBitmap* mark_bitmap = GetMarkBitmap();
-  // If the bitmaps are bound then sweeping this space clearly won't do anything.
-  if (live_bitmap == mark_bitmap) {
-    return;
-  }
-  SweepCallbackContext scc;
-  scc.swap_bitmaps = swap_bitmaps;
-  scc.heap = Runtime::Current()->GetHeap();
-  scc.self = Thread::Current();
-  scc.space = this;
-  scc.freed_objects = 0;
-  scc.freed_bytes = 0;
-  if (swap_bitmaps) {
-    std::swap(live_bitmap, mark_bitmap);
-  }
-  // Bitmaps are pre-swapped for optimization which enables sweeping with the heap unlocked.
-  accounting::SpaceBitmap::SweepWalk(*live_bitmap, *mark_bitmap,
-                                     reinterpret_cast<uintptr_t>(Begin()),
-                                     reinterpret_cast<uintptr_t>(End()),
-                                     IsZygoteSpace() ? &ZygoteSweepCallback : &SweepCallback,
-                                     reinterpret_cast<void*>(&scc));
-  *freed_objects += scc.freed_objects;
-  *freed_bytes += scc.freed_bytes;
-}
-
 }  // namespace space
 }  // namespace gc
 }  // namespace art
diff --git a/runtime/gc/space/malloc_space.h b/runtime/gc/space/malloc_space.h
index 7681b6d..58cfe8b 100644
--- a/runtime/gc/space/malloc_space.h
+++ b/runtime/gc/space/malloc_space.h
@@ -31,6 +31,8 @@ namespace collector {
 
 namespace space {
 
+class ZygoteSpace;
+
 // TODO: Remove define macro
 #define CHECK_MEMORY_CALL(call, args, what) \
   do { \
@@ -41,19 +43,13 @@ namespace space {
     } \
   } while (false)
 
-// const bool kUseRosAlloc = true;
-
 // A common parent of DlMallocSpace and RosAllocSpace.
 class MallocSpace : public ContinuousMemMapAllocSpace {
  public:
   typedef void(*WalkCallback)(void *start, void *end, size_t num_bytes, void* callback_arg);
 
   SpaceType GetType() const {
-    if (GetGcRetentionPolicy() == kGcRetentionPolicyFullCollect) {
-      return kSpaceTypeZygoteSpace;
-    } else {
-      return kSpaceTypeAllocSpace;
-    }
+    return kSpaceTypeMallocSpace;
   }
 
   // Allocate num_bytes without allowing the underlying space to grow.
@@ -109,14 +105,6 @@ class MallocSpace : public ContinuousMemMapAllocSpace {
     return GetMemMap()->Size();
   }
 
-  accounting::SpaceBitmap* GetLiveBitmap() const {
-    return live_bitmap_.get();
-  }
-
-  accounting::SpaceBitmap* GetMarkBitmap() const {
-    return mark_bitmap_.get();
-  }
-
   void Dump(std::ostream& os) const;
 
   void SetGrowthLimit(size_t growth_limit);
@@ -127,33 +115,20 @@ class MallocSpace : public ContinuousMemMapAllocSpace {
   virtual MallocSpace* CreateInstance(const std::string& name, MemMap* mem_map, void* allocator,
                                       byte* begin, byte* end, byte* limit, size_t growth_limit) = 0;
 
-  // Turn ourself into a zygote space and return a new alloc space
-  // which has our unused memory.  When true, the low memory mode
-  // argument specifies that the heap wishes the created space to be
-  // more aggressive in releasing unused pages.
-  MallocSpace* CreateZygoteSpace(const char* alloc_space_name, bool low_memory_mode);
-
+  // Splits ourself into a zygote space and new malloc space which has our unused memory. When true,
+  // the low memory mode argument specifies that the heap wishes the created space to be more
+  // aggressive in releasing unused pages. Invalidates the space its called on.
+  ZygoteSpace* CreateZygoteSpace(const char* alloc_space_name, bool low_memory_mode,
+                                 MallocSpace** out_malloc_space) NO_THREAD_SAFETY_ANALYSIS;
   virtual uint64_t GetBytesAllocated() = 0;
   virtual uint64_t GetObjectsAllocated() = 0;
 
-  // Returns the old mark bitmap.
-  accounting::SpaceBitmap* BindLiveToMarkBitmap();
-  bool HasBoundBitmaps() const;
-  void UnBindBitmaps();
-
   // Returns the class of a recently freed object.
   mirror::Class* FindRecentFreedObject(const mirror::Object* obj);
 
-  // Used to ensure that failure happens when you free / allocate into an invalidated space. If we
-  // don't do this we may get heap corruption instead of a segfault at null.
-  virtual void InvalidateAllocator() = 0;
-
-  // Sweep the references in the malloc space.
-  void Sweep(bool swap_bitmaps, size_t* freed_objects, size_t* freed_bytes);
-
  protected:
   MallocSpace(const std::string& name, MemMap* mem_map, byte* begin, byte* end,
-              byte* limit, size_t growth_limit);
+              byte* limit, size_t growth_limit, bool create_bitmaps = true);
 
   static MemMap* CreateMemMap(const std::string& name, size_t starting_size, size_t* initial_size,
                               size_t* growth_limit, size_t* capacity, byte* requested_begin);
@@ -166,9 +141,9 @@ class MallocSpace : public ContinuousMemMapAllocSpace {
 
   void RegisterRecentFree(mirror::Object* ptr) EXCLUSIVE_LOCKS_REQUIRED(lock_);
 
-  UniquePtr<accounting::SpaceBitmap> live_bitmap_;
-  UniquePtr<accounting::SpaceBitmap> mark_bitmap_;
-  UniquePtr<accounting::SpaceBitmap> temp_bitmap_;
+  virtual accounting::SpaceBitmap::SweepCallback* GetSweepCallback() {
+    return &SweepCallback;
+  }
 
   // Recent allocation buffer.
   static constexpr size_t kRecentFreeCount = kDebugSpaces ? (1 << 16) : 0;
@@ -190,9 +165,9 @@ class MallocSpace : public ContinuousMemMapAllocSpace {
   // one time by a call to ClearGrowthLimit.
   size_t growth_limit_;
 
-  friend class collector::MarkSweep;
-
  private:
+  static void SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg);
+
   DISALLOW_COPY_AND_ASSIGN(MallocSpace);
 };
 
diff --git a/runtime/gc/space/rosalloc_space.cc b/runtime/gc/space/rosalloc_space.cc
index e5993f6..177e38e 100644
--- a/runtime/gc/space/rosalloc_space.cc
+++ b/runtime/gc/space/rosalloc_space.cc
@@ -312,6 +312,7 @@ void RosAllocSpace::RevokeAllThreadLocalBuffers() {
 }
 
 void RosAllocSpace::Clear() {
+  // TODO: Delete and create new mspace here.
   madvise(GetMemMap()->Begin(), GetMemMap()->Size(), MADV_DONTNEED);
   GetLiveBitmap()->Clear();
   GetMarkBitmap()->Clear();
diff --git a/runtime/gc/space/rosalloc_space.h b/runtime/gc/space/rosalloc_space.h
index 6720976..555eb3c 100644
--- a/runtime/gc/space/rosalloc_space.h
+++ b/runtime/gc/space/rosalloc_space.h
@@ -95,10 +95,6 @@ class RosAllocSpace : public MallocSpace {
   // Returns the class of a recently freed object.
   mirror::Class* FindRecentFreedObject(const mirror::Object* obj);
 
-  virtual void InvalidateAllocator() {
-    rosalloc_for_alloc_ = NULL;
-  }
-
   virtual bool IsRosAllocSpace() const {
     return true;
   }
diff --git a/runtime/gc/space/space-inl.h b/runtime/gc/space/space-inl.h
index 0c1d7a2..e94c44e 100644
--- a/runtime/gc/space/space-inl.h
+++ b/runtime/gc/space/space-inl.h
@@ -32,7 +32,7 @@ inline ImageSpace* Space::AsImageSpace() {
 }
 
 inline MallocSpace* Space::AsMallocSpace() {
-  DCHECK(GetType() == kSpaceTypeAllocSpace || GetType() == kSpaceTypeZygoteSpace);
+  DCHECK(GetType() == kSpaceTypeMallocSpace);
   DCHECK(IsDlMallocSpace() || IsRosAllocSpace());
   return down_cast<MallocSpace*>(down_cast<MemMapSpace*>(this));
 }
diff --git a/runtime/gc/space/space.cc b/runtime/gc/space/space.cc
index f8ba6b3..5478d5b 100644
--- a/runtime/gc/space/space.cc
+++ b/runtime/gc/space/space.cc
@@ -17,6 +17,9 @@
 #include "space.h"
 
 #include "base/logging.h"
+#include "gc/accounting/heap_bitmap.h"
+#include "runtime.h"
+#include "thread-inl.h"
 
 namespace art {
 namespace gc {
@@ -41,6 +44,59 @@ DiscontinuousSpace::DiscontinuousSpace(const std::string& name,
     mark_objects_(new accounting::ObjectSet("large marked objects")) {
 }
 
+void ContinuousMemMapAllocSpace::Sweep(bool swap_bitmaps, size_t* freed_objects, size_t* freed_bytes) {
+  DCHECK(freed_objects != nullptr);
+  DCHECK(freed_bytes != nullptr);
+  accounting::SpaceBitmap* live_bitmap = GetLiveBitmap();
+  accounting::SpaceBitmap* mark_bitmap = GetMarkBitmap();
+  // If the bitmaps are bound then sweeping this space clearly won't do anything.
+  if (live_bitmap == mark_bitmap) {
+    return;
+  }
+  SweepCallbackContext scc;
+  scc.swap_bitmaps = swap_bitmaps;
+  scc.heap = Runtime::Current()->GetHeap();
+  scc.self = Thread::Current();
+  scc.space = this;
+  scc.freed_objects = 0;
+  scc.freed_bytes = 0;
+  if (swap_bitmaps) {
+    std::swap(live_bitmap, mark_bitmap);
+  }
+  // Bitmaps are pre-swapped for optimization which enables sweeping with the heap unlocked.
+  accounting::SpaceBitmap::SweepWalk(*live_bitmap, *mark_bitmap,
+                                     reinterpret_cast<uintptr_t>(Begin()),
+                                     reinterpret_cast<uintptr_t>(End()),
+                                     GetSweepCallback(),
+                                     reinterpret_cast<void*>(&scc));
+  *freed_objects += scc.freed_objects;
+  *freed_bytes += scc.freed_bytes;
+}
+
+// Returns the old mark bitmap.
+void ContinuousMemMapAllocSpace::BindLiveToMarkBitmap() {
+  CHECK(!HasBoundBitmaps());
+  accounting::SpaceBitmap* live_bitmap = GetLiveBitmap();
+  accounting::SpaceBitmap* mark_bitmap = mark_bitmap_.release();
+  Runtime::Current()->GetHeap()->GetMarkBitmap()->ReplaceBitmap(mark_bitmap, live_bitmap);
+  temp_bitmap_.reset(mark_bitmap);
+  mark_bitmap_.reset(live_bitmap);
+}
+
+bool ContinuousMemMapAllocSpace::HasBoundBitmaps() const {
+  return temp_bitmap_.get() != nullptr;
+}
+
+void ContinuousMemMapAllocSpace::UnBindBitmaps() {
+  CHECK(HasBoundBitmaps());
+  // At this point, the temp_bitmap holds our old mark bitmap.
+  accounting::SpaceBitmap* new_bitmap = temp_bitmap_.release();
+  Runtime::Current()->GetHeap()->GetMarkBitmap()->ReplaceBitmap(mark_bitmap_.get(), new_bitmap);
+  CHECK_EQ(mark_bitmap_.release(), live_bitmap_.get());
+  mark_bitmap_.reset(new_bitmap);
+  DCHECK(temp_bitmap_.get() == nullptr);
+}
+
 }  // namespace space
 }  // namespace gc
 }  // namespace art
diff --git a/runtime/gc/space/space.h b/runtime/gc/space/space.h
index 5292344..32230b3 100644
--- a/runtime/gc/space/space.h
+++ b/runtime/gc/space/space.h
@@ -44,6 +44,7 @@ namespace space {
 
 class AllocSpace;
 class BumpPointerSpace;
+class ContinuousMemMapAllocSpace;
 class ContinuousSpace;
 class DiscontinuousSpace;
 class MallocSpace;
@@ -51,6 +52,7 @@ class DlMallocSpace;
 class RosAllocSpace;
 class ImageSpace;
 class LargeObjectSpace;
+class ZygoteSpace;
 
 static constexpr bool kDebugSpaces = kIsDebugBuild;
 
@@ -68,7 +70,7 @@ std::ostream& operator<<(std::ostream& os, const GcRetentionPolicy& policy);
 
 enum SpaceType {
   kSpaceTypeImageSpace,
-  kSpaceTypeAllocSpace,
+  kSpaceTypeMallocSpace,
   kSpaceTypeZygoteSpace,
   kSpaceTypeBumpPointerSpace,
   kSpaceTypeLargeObjectSpace,
@@ -91,11 +93,6 @@ class Space {
     return gc_retention_policy_;
   }
 
-  // Does the space support allocation?
-  virtual bool CanAllocateInto() const {
-    return true;
-  }
-
   // Is the given object contained within this space?
   virtual bool Contains(const mirror::Object* obj) const = 0;
 
@@ -111,7 +108,7 @@ class Space {
   // Is this a dlmalloc backed allocation space?
   bool IsMallocSpace() const {
     SpaceType type = GetType();
-    return type == kSpaceTypeAllocSpace || type == kSpaceTypeZygoteSpace;
+    return type == kSpaceTypeMallocSpace;
   }
   MallocSpace* AsMallocSpace();
 
@@ -120,20 +117,24 @@ class Space {
   }
   virtual DlMallocSpace* AsDlMallocSpace() {
     LOG(FATAL) << "Unreachable";
-    return NULL;
+    return nullptr;
   }
   virtual bool IsRosAllocSpace() const {
     return false;
   }
   virtual RosAllocSpace* AsRosAllocSpace() {
     LOG(FATAL) << "Unreachable";
-    return NULL;
+    return nullptr;
   }
 
   // Is this the space allocated into by the Zygote and no-longer in use?
   bool IsZygoteSpace() const {
     return GetType() == kSpaceTypeZygoteSpace;
   }
+  virtual ZygoteSpace* AsZygoteSpace() {
+    LOG(FATAL) << "Unreachable";
+    return nullptr;
+  }
 
   // Is this space a bump pointer space?
   bool IsBumpPointerSpace() const {
@@ -141,7 +142,7 @@ class Space {
   }
   virtual BumpPointerSpace* AsBumpPointerSpace() {
     LOG(FATAL) << "Unreachable";
-    return NULL;
+    return nullptr;
   }
 
   // Does this space hold large objects and implement the large object space abstraction?
@@ -168,6 +169,14 @@ class Space {
     return nullptr;
   }
 
+  virtual bool IsContinuousMemMapAllocSpace() const {
+    return false;
+  }
+  virtual ContinuousMemMapAllocSpace* AsContinuousMemMapAllocSpace() {
+    LOG(FATAL) << "Unimplemented";
+    return nullptr;
+  }
+
   virtual ~Space() {}
 
  protected:
@@ -181,6 +190,15 @@ class Space {
   std::string name_;
 
  protected:
+  struct SweepCallbackContext {
+    bool swap_bitmaps;
+    Heap* heap;
+    space::Space* space;
+    Thread* self;
+    size_t freed_objects;
+    size_t freed_bytes;
+  };
+
   // When should objects within this space be reclaimed? Not constant as we vary it in the case
   // of Zygote forking.
   GcRetentionPolicy gc_retention_policy_;
@@ -378,22 +396,51 @@ class ContinuousMemMapAllocSpace : public MemMapSpace, public AllocSpace {
   virtual bool IsAllocSpace() const {
     return true;
   }
-
   virtual AllocSpace* AsAllocSpace() {
     return this;
   }
 
+  virtual bool IsContinuousMemMapAllocSpace() const {
+    return true;
+  }
+  virtual ContinuousMemMapAllocSpace* AsContinuousMemMapAllocSpace() {
+    return this;
+  }
+
+  bool HasBoundBitmaps() const EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+  void BindLiveToMarkBitmap()
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+  void UnBindBitmaps() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
+
   virtual void Clear() {
     LOG(FATAL) << "Unimplemented";
   }
 
+  virtual accounting::SpaceBitmap* GetLiveBitmap() const {
+    return live_bitmap_.get();
+  }
+  virtual accounting::SpaceBitmap* GetMarkBitmap() const {
+    return mark_bitmap_.get();
+  }
+
+  virtual void Sweep(bool swap_bitmaps, size_t* freed_objects, size_t* freed_bytes);
+  virtual accounting::SpaceBitmap::SweepCallback* GetSweepCallback() {
+    LOG(FATAL) << "Unimplemented";
+    return nullptr;
+  }
+
  protected:
+  UniquePtr<accounting::SpaceBitmap> live_bitmap_;
+  UniquePtr<accounting::SpaceBitmap> mark_bitmap_;
+  UniquePtr<accounting::SpaceBitmap> temp_bitmap_;
+
   ContinuousMemMapAllocSpace(const std::string& name, MemMap* mem_map, byte* begin,
                              byte* end, byte* limit, GcRetentionPolicy gc_retention_policy)
       : MemMapSpace(name, mem_map, begin, end, limit, gc_retention_policy) {
   }
 
  private:
+  friend class gc::Heap;
   DISALLOW_COPY_AND_ASSIGN(ContinuousMemMapAllocSpace);
 };
 
diff --git a/runtime/gc/space/space_test.cc b/runtime/gc/space/space_test.cc
index b1be9d8..427d547 100644
--- a/runtime/gc/space/space_test.cc
+++ b/runtime/gc/space/space_test.cc
@@ -16,6 +16,7 @@
 
 #include "dlmalloc_space.h"
 #include "large_object_space.h"
+#include "zygote_space.h"
 
 #include "common_test.h"
 #include "globals.h"
@@ -179,7 +180,16 @@ void SpaceTest::ZygoteSpaceTestBody(CreateSpaceFn create_space) {
 
   // Make sure that the zygote space isn't directly at the start of the space.
   space->Alloc(self, 1U * MB, &dummy);
-  space = space->CreateZygoteSpace("alloc space", Runtime::Current()->GetHeap()->IsLowMemoryMode());
+
+  gc::Heap* heap = Runtime::Current()->GetHeap();
+  space::Space* old_space = space;
+  heap->RemoveSpace(old_space);
+  space::ZygoteSpace* zygote_space = space->CreateZygoteSpace("alloc space",
+                                                              heap->IsLowMemoryMode(),
+                                                              &space);
+  delete old_space;
+  // Add the zygote space.
+  AddSpace(zygote_space);
 
   // Make space findable to the heap, will also delete space when runtime is cleaned up
   AddSpace(space);
diff --git a/runtime/gc/space/zygote_space.cc b/runtime/gc/space/zygote_space.cc
new file mode 100644
index 0000000..a303765
--- /dev/null
+++ b/runtime/gc/space/zygote_space.cc
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "zygote_space.h"
+
+#include "gc/accounting/card_table-inl.h"
+#include "gc/accounting/space_bitmap-inl.h"
+#include "gc/heap.h"
+#include "thread-inl.h"
+#include "utils.h"
+
+namespace art {
+namespace gc {
+namespace space {
+
+class CountObjectsAllocated {
+ public:
+  explicit CountObjectsAllocated(size_t* objects_allocated)
+      : objects_allocated_(objects_allocated) {}
+
+  void operator()(mirror::Object* obj) const {
+    ++*objects_allocated_;
+  }
+
+ private:
+  size_t* const objects_allocated_;
+};
+
+ZygoteSpace* ZygoteSpace::Create(const std::string& name, MemMap* mem_map,
+                                 accounting::SpaceBitmap* live_bitmap,
+                                 accounting::SpaceBitmap* mark_bitmap) {
+  DCHECK(live_bitmap != nullptr);
+  DCHECK(mark_bitmap != nullptr);
+  size_t objects_allocated = 0;
+  CountObjectsAllocated visitor(&objects_allocated);
+  ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
+  live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(mem_map->Begin()),
+                                reinterpret_cast<uintptr_t>(mem_map->End()), visitor);
+  ZygoteSpace* zygote_space = new ZygoteSpace(name, mem_map, objects_allocated);
+  CHECK(zygote_space->live_bitmap_.get() == nullptr);
+  CHECK(zygote_space->mark_bitmap_.get() == nullptr);
+  zygote_space->live_bitmap_.reset(live_bitmap);
+  zygote_space->mark_bitmap_.reset(mark_bitmap);
+  return zygote_space;
+}
+
+ZygoteSpace::ZygoteSpace(const std::string& name, MemMap* mem_map, size_t objects_allocated)
+    : ContinuousMemMapAllocSpace(name, mem_map, mem_map->Begin(), mem_map->End(), mem_map->End(),
+                                 kGcRetentionPolicyFullCollect),
+      objects_allocated_(objects_allocated) {
+}
+
+void ZygoteSpace::Dump(std::ostream& os) const {
+  os << GetType()
+      << " begin=" << reinterpret_cast<void*>(Begin())
+      << ",end=" << reinterpret_cast<void*>(End())
+      << ",size=" << PrettySize(Size())
+      << ",name=\"" << GetName() << "\"]";
+}
+
+void ZygoteSpace::SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
+  SweepCallbackContext* context = static_cast<SweepCallbackContext*>(arg);
+  DCHECK(context->space->IsZygoteSpace());
+  ZygoteSpace* zygote_space = context->space->AsZygoteSpace();
+  Locks::heap_bitmap_lock_->AssertExclusiveHeld(context->self);
+  accounting::CardTable* card_table = context->heap->GetCardTable();
+  // If the bitmaps aren't swapped we need to clear the bits since the GC isn't going to re-swap
+  // the bitmaps as an optimization.
+  if (!context->swap_bitmaps) {
+    accounting::SpaceBitmap* bitmap = zygote_space->GetLiveBitmap();
+    for (size_t i = 0; i < num_ptrs; ++i) {
+      bitmap->Clear(ptrs[i]);
+    }
+  }
+  // We don't free any actual memory to avoid dirtying the shared zygote pages.
+  for (size_t i = 0; i < num_ptrs; ++i) {
+    // Need to mark the card since this will update the mod-union table next GC cycle.
+    card_table->MarkCard(ptrs[i]);
+  }
+  zygote_space->objects_allocated_.FetchAndSub(num_ptrs);
+}
+
+}  // namespace space
+}  // namespace gc
+}  // namespace art
diff --git a/runtime/gc/space/zygote_space.h b/runtime/gc/space/zygote_space.h
new file mode 100644
index 0000000..10a5492
--- /dev/null
+++ b/runtime/gc/space/zygote_space.h
@@ -0,0 +1,95 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_GC_SPACE_ZYGOTE_SPACE_H_
+#define ART_RUNTIME_GC_SPACE_ZYGOTE_SPACE_H_
+
+#include "malloc_space.h"
+#include "mem_map.h"
+
+namespace art {
+namespace gc {
+
+namespace accounting {
+class SpaceBitmap;
+}
+
+namespace space {
+
+// An zygote space is a space which you cannot allocate into or free from.
+class ZygoteSpace : public ContinuousMemMapAllocSpace {
+ public:
+  // Returns the remaining storage in the out_map field.
+  static ZygoteSpace* Create(const std::string& name, MemMap* mem_map,
+                             accounting::SpaceBitmap* live_bitmap,
+                             accounting::SpaceBitmap* mark_bitmap)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
+  void Dump(std::ostream& os) const;
+  virtual SpaceType GetType() const {
+    return kSpaceTypeZygoteSpace;
+  }
+  virtual ZygoteSpace* AsZygoteSpace() {
+    return this;
+  }
+  virtual mirror::Object* AllocWithGrowth(Thread* /*self*/, size_t /*num_bytes*/,
+                                          size_t* /*bytes_allocated*/) {
+    LOG(FATAL) << "Unimplemented";
+    return nullptr;
+  }
+  virtual mirror::Object* Alloc(Thread* self, size_t num_bytes, size_t* bytes_allocated) {
+    LOG(FATAL) << "Unimplemented";
+    return nullptr;
+  }
+  virtual size_t AllocationSize(const mirror::Object* obj) {
+    LOG(FATAL) << "Unimplemented";
+    return 0;
+  }
+  virtual size_t Free(Thread* self, mirror::Object* ptr) {
+    LOG(FATAL) << "Unimplemented";
+    return 0;
+  }
+  virtual size_t FreeList(Thread* self, size_t num_ptrs, mirror::Object** ptrs) {
+    LOG(FATAL) << "Unimplemented";
+    return 0;
+  }
+  virtual uint64_t GetBytesAllocated() {
+    return Size();
+  }
+  virtual uint64_t GetObjectsAllocated() {
+    return objects_allocated_;
+  }
+
+ protected:
+  virtual accounting::SpaceBitmap::SweepCallback* GetSweepCallback() {
+    return &SweepCallback;
+  }
+
+ private:
+  ZygoteSpace(const std::string& name, MemMap* mem_map, size_t objects_allocated);
+  static void SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg);
+
+  AtomicInteger objects_allocated_;
+
+  friend class Space;
+  DISALLOW_COPY_AND_ASSIGN(ZygoteSpace);
+};
+
+}  // namespace space
+}  // namespace gc
+}  // namespace art
+
+#endif  // ART_RUNTIME_GC_SPACE_ZYGOTE_SPACE_H_