runtime/gc/space/malloc_space.cc - platform/art - Git at Google

 /*
  * Copyright (C) 2013 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 "malloc_space.h"

 #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"
 #include "handle_scope-inl.h"
 #include "thread.h"
 #include "thread_list.h"
 #include "utils.h"

 namespace art {
 namespace gc {
 namespace space {

 size_t MallocSpace::bitmap_index_ = 0;

 MallocSpace::MallocSpace(const std::string& name, MemMap* mem_map,
                          uint8_t* begin, uint8_t* end, uint8_t* limit, size_t growth_limit,
                          bool create_bitmaps, bool can_move_objects, size_t starting_size,
                          size_t initial_size)
     : ContinuousMemMapAllocSpace(name, mem_map, begin, end, limit, kGcRetentionPolicyAlwaysCollect),
       recent_free_pos_(0), lock_("allocation space lock", kAllocSpaceLock),
       growth_limit_(growth_limit), can_move_objects_(can_move_objects),
       starting_size_(starting_size), initial_size_(initial_size) {
   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::ContinuousSpaceBitmap::Create(
         StringPrintf("allocspace %s live-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
         Begin(), NonGrowthLimitCapacity()));
     CHECK(live_bitmap_.get() != nullptr) << "could not create allocspace live bitmap #"
         << bitmap_index;
     mark_bitmap_.reset(accounting::ContinuousSpaceBitmap::Create(
         StringPrintf("allocspace %s mark-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
         Begin(), NonGrowthLimitCapacity()));
     CHECK(live_bitmap_.get() != nullptr) << "could not create allocspace mark bitmap #"
         << bitmap_index;
   }
   for (auto& freed : recent_freed_objects_) {
     freed.first = nullptr;
     freed.second = nullptr;
   }
 }

 MemMap* MallocSpace::CreateMemMap(const std::string& name, size_t starting_size, size_t* initial_size,
                                   size_t* growth_limit, size_t* capacity, uint8_t* requested_begin) {
   // Sanity check arguments
   if (starting_size > *initial_size) {
     *initial_size = starting_size;
   }
   if (*initial_size > *growth_limit) {
     LOG(ERROR) << "Failed to create alloc space (" << name << ") where the initial size ("
         << PrettySize(*initial_size) << ") is larger than its capacity ("
         << PrettySize(*growth_limit) << ")";
     return NULL;
   }
   if (*growth_limit > *capacity) {
     LOG(ERROR) << "Failed to create alloc space (" << name << ") where the growth limit capacity ("
         << PrettySize(*growth_limit) << ") is larger than the capacity ("
         << PrettySize(*capacity) << ")";
     return NULL;
   }

   // Page align growth limit and capacity which will be used to manage mmapped storage
   *growth_limit = RoundUp(*growth_limit, kPageSize);
   *capacity = RoundUp(*capacity, kPageSize);

   std::string error_msg;
   MemMap* mem_map = MemMap::MapAnonymous(name.c_str(), requested_begin, *capacity,
                                          PROT_READ | PROT_WRITE, true, false, &error_msg);
   if (mem_map == nullptr) {
     LOG(ERROR) << "Failed to allocate pages for alloc space (" << name << ") of size "
                << PrettySize(*capacity) << ": " << error_msg;
   }
   return mem_map;
 }

 mirror::Class* MallocSpace::FindRecentFreedObject(const mirror::Object* obj) {
   size_t pos = recent_free_pos_;
   // Start at the most recently freed object and work our way back since there may be duplicates
   // caused by dlmalloc reusing memory.
   if (kRecentFreeCount > 0) {
     for (size_t i = 0; i + 1 < kRecentFreeCount + 1; ++i) {
       pos = pos != 0 ? pos - 1 : kRecentFreeMask;
       if (recent_freed_objects_[pos].first == obj) {
         return recent_freed_objects_[pos].second;
       }
     }
   }
   return nullptr;
 }

 void MallocSpace::RegisterRecentFree(mirror::Object* ptr) {
   // No verification since the object is dead.
   recent_freed_objects_[recent_free_pos_] = std::make_pair(ptr, ptr->GetClass<kVerifyNone>());
   recent_free_pos_ = (recent_free_pos_ + 1) & kRecentFreeMask;
 }

 void MallocSpace::SetGrowthLimit(size_t growth_limit) {
   growth_limit = RoundUp(growth_limit, kPageSize);
   growth_limit_ = growth_limit;
   if (Size() > growth_limit_) {
     SetEnd(begin_ + growth_limit);
   }
 }

 void* MallocSpace::MoreCore(intptr_t increment) {
   CheckMoreCoreForPrecondition();
   uint8_t* original_end = End();
   if (increment != 0) {
     VLOG(heap) << "MallocSpace::MoreCore " << PrettySize(increment);
     uint8_t* new_end = original_end + increment;
     if (increment > 0) {
       // Should never be asked to increase the allocation beyond the capacity of the space. Enforced
       // by mspace_set_footprint_limit.
       CHECK_LE(new_end, Begin() + Capacity());
       CHECK_MEMORY_CALL(mprotect, (original_end, increment, PROT_READ | PROT_WRITE), GetName());
     } else {
       // Should never be asked for negative footprint (ie before begin). Zero footprint is ok.
       CHECK_GE(original_end + increment, Begin());
       // Advise we don't need the pages and protect them
       // TODO: by removing permissions to the pages we may be causing TLB shoot-down which can be
       // expensive (note the same isn't true for giving permissions to a page as the protected
       // page shouldn't be in a TLB). We should investigate performance impact of just
       // removing ignoring the memory protection change here and in Space::CreateAllocSpace. It's
       // likely just a useful debug feature.
       size_t size = -increment;
       CHECK_MEMORY_CALL(madvise, (new_end, size, MADV_DONTNEED), GetName());
       CHECK_MEMORY_CALL(mprotect, (new_end, size, PROT_NONE), GetName());
     }
     // Update end_.
     SetEnd(new_end);
   }
   return original_end;
 }

 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.
   RevokeAllThreadLocalBuffers();
   SetEnd(reinterpret_cast<uint8_t*>(RoundUp(reinterpret_cast<uintptr_t>(End()), kPageSize)));
   DCHECK(IsAligned<accounting::CardTable::kCardSize>(begin_));
   DCHECK(IsAligned<accounting::CardTable::kCardSize>(End()));
   DCHECK(IsAligned<kPageSize>(begin_));
   DCHECK(IsAligned<kPageSize>(End()));
   size_t size = RoundUp(Size(), kPageSize);
   // Trimming the heap should be done by the caller since we may have invalidated the accounting
   // stored in between objects.
   // Remaining size is for the new alloc space.
   const size_t growth_limit = growth_limit_ - size;
   // Use mem map limit in case error for clear growth limit.
   const size_t capacity = NonGrowthLimitCapacity() - size;
   VLOG(heap) << "Begin " << reinterpret_cast<const void*>(begin_) << "\n"
              << "End " << reinterpret_cast<const void*>(End()) << "\n"
              << "Size " << size << "\n"
              << "GrowthLimit " << growth_limit_ << "\n"
              << "Capacity " << Capacity();
   SetGrowthLimit(RoundUp(size, kPageSize));
   // FIXME: Do we need reference counted pointers here?
   // Make the two spaces share the same mark bitmaps since the bitmaps span both of the spaces.
   VLOG(heap) << "Creating new AllocSpace: ";
   VLOG(heap) << "Size " << GetMemMap()->Size();
   VLOG(heap) << "GrowthLimit " << PrettySize(growth_limit);
   VLOG(heap) << "Capacity " << PrettySize(capacity);
   // Remap the tail.
   std::string error_msg;
   std::unique_ptr<MemMap> mem_map(GetMemMap()->RemapAtEnd(End(), alloc_space_name,
                                                           PROT_READ | PROT_WRITE, &error_msg));
   CHECK(mem_map.get() != nullptr) << error_msg;
   void* allocator = CreateAllocator(End(), starting_size_, initial_size_, capacity,
                                     low_memory_mode);
   // Protect memory beyond the initial size.
   uint8_t* end = mem_map->Begin() + starting_size_;
   if (capacity > initial_size_) {
     CHECK_MEMORY_CALL(mprotect, (end, capacity - initial_size_, PROT_NONE), alloc_space_name);
   }
   *out_malloc_space = CreateInstance(mem_map.release(), alloc_space_name, allocator, End(), end,
                                      limit_, growth_limit, CanMoveObjects());
   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()));

   // 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 {
   os << GetType()
      << " begin=" << reinterpret_cast<void*>(Begin())
      << ",end=" << reinterpret_cast<void*>(End())
      << ",limit=" << reinterpret_cast<void*>(Limit())
      << ",size=" << PrettySize(Size()) << ",capacity=" << PrettySize(Capacity())
      << ",non_growth_limit_capacity=" << PrettySize(NonGrowthLimitCapacity())
      << ",name=\"" << GetName() << "\"]";
 }

 void MallocSpace::SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
   SweepCallbackContext* context = static_cast<SweepCallbackContext*>(arg);
   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::ContinuousSpaceBitmap* bitmap = space->GetLiveBitmap();
     for (size_t i = 0; i < num_ptrs; ++i) {
       bitmap->Clear(ptrs[i]);
     }
   }
   // Use a bulk free, that merges consecutive objects before freeing or free per object?
   // Documentation suggests better free performance with merging, but this may be at the expensive
   // of allocation.
   context->freed.objects += num_ptrs;
   context->freed.bytes += space->FreeList(self, num_ptrs, ptrs);
 }

 void MallocSpace::ClampGrowthLimit() {
   size_t new_capacity = Capacity();
   CHECK_LE(new_capacity, NonGrowthLimitCapacity());
   GetLiveBitmap()->SetHeapSize(new_capacity);
   GetMarkBitmap()->SetHeapSize(new_capacity);
   if (temp_bitmap_.get() != nullptr) {
     // If the bitmaps are clamped, then the temp bitmap is actually the mark bitmap.
     temp_bitmap_->SetHeapSize(new_capacity);
   }
   GetMemMap()->SetSize(new_capacity);
   limit_ = Begin() + new_capacity;
 }

 }  // namespace space
 }  // namespace gc
 }  // namespace art
	/*
	* Copyright (C) 2013 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 "malloc_space.h"

	#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"
	#include "handle_scope-inl.h"
	#include "thread.h"
	#include "thread_list.h"
	#include "utils.h"

	namespace art {
	namespace gc {
	namespace space {

	size_t MallocSpace::bitmap_index_ = 0;

	MallocSpace::MallocSpace(const std::string& name, MemMap* mem_map,
	uint8_t* begin, uint8_t* end, uint8_t* limit, size_t growth_limit,
	bool create_bitmaps, bool can_move_objects, size_t starting_size,
	size_t initial_size)
	: ContinuousMemMapAllocSpace(name, mem_map, begin, end, limit, kGcRetentionPolicyAlwaysCollect),
	recent_free_pos_(0), lock_("allocation space lock", kAllocSpaceLock),
	growth_limit_(growth_limit), can_move_objects_(can_move_objects),
	starting_size_(starting_size), initial_size_(initial_size) {
	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::ContinuousSpaceBitmap::Create(
	StringPrintf("allocspace %s live-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
	Begin(), NonGrowthLimitCapacity()));
	CHECK(live_bitmap_.get() != nullptr) << "could not create allocspace live bitmap #"
	<< bitmap_index;
	mark_bitmap_.reset(accounting::ContinuousSpaceBitmap::Create(
	StringPrintf("allocspace %s mark-bitmap %d", name.c_str(), static_cast<int>(bitmap_index)),
	Begin(), NonGrowthLimitCapacity()));
	CHECK(live_bitmap_.get() != nullptr) << "could not create allocspace mark bitmap #"
	<< bitmap_index;
	}
	for (auto& freed : recent_freed_objects_) {
	freed.first = nullptr;
	freed.second = nullptr;
	}
	}

	MemMap* MallocSpace::CreateMemMap(const std::string& name, size_t starting_size, size_t* initial_size,
	size_t* growth_limit, size_t* capacity, uint8_t* requested_begin) {
	// Sanity check arguments
	if (starting_size > *initial_size) {
	*initial_size = starting_size;
	}
	if (initial_size > growth_limit) {
	LOG(ERROR) << "Failed to create alloc space (" << name << ") where the initial size ("
	<< PrettySize(*initial_size) << ") is larger than its capacity ("
	<< PrettySize(*growth_limit) << ")";
	return NULL;
	}
	if (growth_limit > capacity) {
	LOG(ERROR) << "Failed to create alloc space (" << name << ") where the growth limit capacity ("
	<< PrettySize(*growth_limit) << ") is larger than the capacity ("
	<< PrettySize(*capacity) << ")";
	return NULL;
	}

	// Page align growth limit and capacity which will be used to manage mmapped storage
	growth_limit = RoundUp(growth_limit, kPageSize);
	capacity = RoundUp(capacity, kPageSize);

	std::string error_msg;
	MemMap* mem_map = MemMap::MapAnonymous(name.c_str(), requested_begin, *capacity,
	PROT_READ \| PROT_WRITE, true, false, &error_msg);
	if (mem_map == nullptr) {
	LOG(ERROR) << "Failed to allocate pages for alloc space (" << name << ") of size "
	<< PrettySize(*capacity) << ": " << error_msg;
	}
	return mem_map;
	}

	mirror::Class* MallocSpace::FindRecentFreedObject(const mirror::Object* obj) {
	size_t pos = recent_free_pos_;
	// Start at the most recently freed object and work our way back since there may be duplicates
	// caused by dlmalloc reusing memory.
	if (kRecentFreeCount > 0) {
	for (size_t i = 0; i + 1 < kRecentFreeCount + 1; ++i) {
	pos = pos != 0 ? pos - 1 : kRecentFreeMask;
	if (recent_freed_objects_[pos].first == obj) {
	return recent_freed_objects_[pos].second;
	}
	}
	}
	return nullptr;
	}

	void MallocSpace::RegisterRecentFree(mirror::Object* ptr) {
	// No verification since the object is dead.
	recent_freed_objects_[recent_free_pos_] = std::make_pair(ptr, ptr->GetClass<kVerifyNone>());
	recent_free_pos_ = (recent_free_pos_ + 1) & kRecentFreeMask;
	}

	void MallocSpace::SetGrowthLimit(size_t growth_limit) {
	growth_limit = RoundUp(growth_limit, kPageSize);
	growth_limit_ = growth_limit;
	if (Size() > growth_limit_) {
	SetEnd(begin_ + growth_limit);
	}
	}

	void* MallocSpace::MoreCore(intptr_t increment) {
	CheckMoreCoreForPrecondition();
	uint8_t* original_end = End();
	if (increment != 0) {
	VLOG(heap) << "MallocSpace::MoreCore " << PrettySize(increment);
	uint8_t* new_end = original_end + increment;
	if (increment > 0) {
	// Should never be asked to increase the allocation beyond the capacity of the space. Enforced
	// by mspace_set_footprint_limit.
	CHECK_LE(new_end, Begin() + Capacity());
	CHECK_MEMORY_CALL(mprotect, (original_end, increment, PROT_READ \| PROT_WRITE), GetName());
	} else {
	// Should never be asked for negative footprint (ie before begin). Zero footprint is ok.
	CHECK_GE(original_end + increment, Begin());
	// Advise we don't need the pages and protect them
	// TODO: by removing permissions to the pages we may be causing TLB shoot-down which can be
	// expensive (note the same isn't true for giving permissions to a page as the protected
	// page shouldn't be in a TLB). We should investigate performance impact of just
	// removing ignoring the memory protection change here and in Space::CreateAllocSpace. It's
	// likely just a useful debug feature.
	size_t size = -increment;
	CHECK_MEMORY_CALL(madvise, (new_end, size, MADV_DONTNEED), GetName());
	CHECK_MEMORY_CALL(mprotect, (new_end, size, PROT_NONE), GetName());
	}
	// Update end_.
	SetEnd(new_end);
	}
	return original_end;
	}

	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.
	RevokeAllThreadLocalBuffers();
	SetEnd(reinterpret_cast<uint8_t*>(RoundUp(reinterpret_cast<uintptr_t>(End()), kPageSize)));
	DCHECK(IsAligned<accounting::CardTable::kCardSize>(begin_));
	DCHECK(IsAligned<accounting::CardTable::kCardSize>(End()));
	DCHECK(IsAligned<kPageSize>(begin_));
	DCHECK(IsAligned<kPageSize>(End()));
	size_t size = RoundUp(Size(), kPageSize);
	// Trimming the heap should be done by the caller since we may have invalidated the accounting
	// stored in between objects.
	// Remaining size is for the new alloc space.
	const size_t growth_limit = growth_limit_ - size;
	// Use mem map limit in case error for clear growth limit.
	const size_t capacity = NonGrowthLimitCapacity() - size;
	VLOG(heap) << "Begin " << reinterpret_cast<const void*>(begin_) << "\n"
	<< "End " << reinterpret_cast<const void*>(End()) << "\n"
	<< "Size " << size << "\n"
	<< "GrowthLimit " << growth_limit_ << "\n"
	<< "Capacity " << Capacity();
	SetGrowthLimit(RoundUp(size, kPageSize));
	// FIXME: Do we need reference counted pointers here?
	// Make the two spaces share the same mark bitmaps since the bitmaps span both of the spaces.
	VLOG(heap) << "Creating new AllocSpace: ";
	VLOG(heap) << "Size " << GetMemMap()->Size();
	VLOG(heap) << "GrowthLimit " << PrettySize(growth_limit);
	VLOG(heap) << "Capacity " << PrettySize(capacity);
	// Remap the tail.
	std::string error_msg;
	std::unique_ptr<MemMap> mem_map(GetMemMap()->RemapAtEnd(End(), alloc_space_name,
	PROT_READ \| PROT_WRITE, &error_msg));
	CHECK(mem_map.get() != nullptr) << error_msg;
	void* allocator = CreateAllocator(End(), starting_size_, initial_size_, capacity,
	low_memory_mode);
	// Protect memory beyond the initial size.
	uint8_t* end = mem_map->Begin() + starting_size_;
	if (capacity > initial_size_) {
	CHECK_MEMORY_CALL(mprotect, (end, capacity - initial_size_, PROT_NONE), alloc_space_name);
	}
	*out_malloc_space = CreateInstance(mem_map.release(), alloc_space_name, allocator, End(), end,
	limit_, growth_limit, CanMoveObjects());
	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()));

	// 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 {
	os << GetType()
	<< " begin=" << reinterpret_cast<void*>(Begin())
	<< ",end=" << reinterpret_cast<void*>(End())
	<< ",limit=" << reinterpret_cast<void*>(Limit())
	<< ",size=" << PrettySize(Size()) << ",capacity=" << PrettySize(Capacity())
	<< ",non_growth_limit_capacity=" << PrettySize(NonGrowthLimitCapacity())
	<< ",name=\"" << GetName() << "\"]";
	}

	void MallocSpace::SweepCallback(size_t num_ptrs, mirror::Object** ptrs, void* arg) {
	SweepCallbackContext* context = static_cast<SweepCallbackContext*>(arg);
	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::ContinuousSpaceBitmap* bitmap = space->GetLiveBitmap();
	for (size_t i = 0; i < num_ptrs; ++i) {
	bitmap->Clear(ptrs[i]);
	}
	}
	// Use a bulk free, that merges consecutive objects before freeing or free per object?
	// Documentation suggests better free performance with merging, but this may be at the expensive
	// of allocation.
	context->freed.objects += num_ptrs;
	context->freed.bytes += space->FreeList(self, num_ptrs, ptrs);
	}

	void MallocSpace::ClampGrowthLimit() {
	size_t new_capacity = Capacity();
	CHECK_LE(new_capacity, NonGrowthLimitCapacity());
	GetLiveBitmap()->SetHeapSize(new_capacity);
	GetMarkBitmap()->SetHeapSize(new_capacity);
	if (temp_bitmap_.get() != nullptr) {
	// If the bitmaps are clamped, then the temp bitmap is actually the mark bitmap.
	temp_bitmap_->SetHeapSize(new_capacity);
	}
	GetMemMap()->SetSize(new_capacity);
	limit_ = Begin() + new_capacity;
	}

	} // namespace space
	} // namespace gc
	} // namespace art