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* Copyright (C) 2011 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <memory>
#include <string>
#include "atomic.h"
#include "base/macros.h"
#include "base/mutex.h"
#include "gc/accounting/space_bitmap.h"
#include "gc/collector/garbage_collector.h"
#include "globals.h"
#include "image.h"
#include "mem_map.h"
namespace art {
namespace mirror {
class Object;
} // namespace mirror
namespace gc {
class Heap;
namespace space {
class AllocSpace;
class BumpPointerSpace;
class ContinuousMemMapAllocSpace;
class ContinuousSpace;
class DiscontinuousSpace;
class MallocSpace;
class DlMallocSpace;
class RosAllocSpace;
class ImageSpace;
class LargeObjectSpace;
class RegionSpace;
class ZygoteSpace;
static constexpr bool kDebugSpaces = kIsDebugBuild;
// See Space::GetGcRetentionPolicy.
enum GcRetentionPolicy {
// Objects are retained forever with this policy for a space.
// Every GC cycle will attempt to collect objects in this space.
// Objects will be considered for collection only in "full" GC cycles, ie faster partial
// collections won't scan these areas such as the Zygote.
std::ostream& operator<<(std::ostream& os, const GcRetentionPolicy& policy);
enum SpaceType {
std::ostream& operator<<(std::ostream& os, const SpaceType& space_type);
// A space contains memory allocated for managed objects.
class Space {
// Dump space. Also key method for C++ vtables.
virtual void Dump(std::ostream& os) const;
// Name of the space. May vary, for example before/after the Zygote fork.
const char* GetName() const {
return name_.c_str();
// The policy of when objects are collected associated with this space.
GcRetentionPolicy GetGcRetentionPolicy() const {
return gc_retention_policy_;
// Is the given object contained within this space?
virtual bool Contains(const mirror::Object* obj) const = 0;
// The kind of space this: image, alloc, zygote, large object.
virtual SpaceType GetType() const = 0;
// Is this an image space, ie one backed by a memory mapped image file.
bool IsImageSpace() const {
return GetType() == kSpaceTypeImageSpace;
ImageSpace* AsImageSpace();
// Is this a dlmalloc backed allocation space?
bool IsMallocSpace() const {
SpaceType type = GetType();
return type == kSpaceTypeMallocSpace;
MallocSpace* AsMallocSpace();
virtual bool IsDlMallocSpace() const {
return false;
virtual DlMallocSpace* AsDlMallocSpace();
virtual bool IsRosAllocSpace() const {
return false;
virtual RosAllocSpace* AsRosAllocSpace();
// Is this the space allocated into by the Zygote and no-longer in use for allocation?
bool IsZygoteSpace() const {
return GetType() == kSpaceTypeZygoteSpace;
virtual ZygoteSpace* AsZygoteSpace();
// Is this space a bump pointer space?
bool IsBumpPointerSpace() const {
return GetType() == kSpaceTypeBumpPointerSpace;
virtual BumpPointerSpace* AsBumpPointerSpace();
bool IsRegionSpace() const {
return GetType() == kSpaceTypeRegionSpace;
virtual RegionSpace* AsRegionSpace();
// Does this space hold large objects and implement the large object space abstraction?
bool IsLargeObjectSpace() const {
return GetType() == kSpaceTypeLargeObjectSpace;
LargeObjectSpace* AsLargeObjectSpace();
virtual bool IsContinuousSpace() const {
return false;
ContinuousSpace* AsContinuousSpace();
virtual bool IsDiscontinuousSpace() const {
return false;
DiscontinuousSpace* AsDiscontinuousSpace();
virtual bool IsAllocSpace() const {
return false;
virtual AllocSpace* AsAllocSpace();
virtual bool IsContinuousMemMapAllocSpace() const {
return false;
virtual ContinuousMemMapAllocSpace* AsContinuousMemMapAllocSpace();
// Returns true if objects in the space are movable.
virtual bool CanMoveObjects() const = 0;
virtual ~Space() {}
Space(const std::string& name, GcRetentionPolicy gc_retention_policy);
void SetGcRetentionPolicy(GcRetentionPolicy gc_retention_policy) {
gc_retention_policy_ = gc_retention_policy;
// Name of the space that may vary due to the Zygote fork.
std::string name_;
// When should objects within this space be reclaimed? Not constant as we vary it in the case
// of Zygote forking.
GcRetentionPolicy gc_retention_policy_;
friend class art::gc::Heap;
std::ostream& operator<<(std::ostream& os, const Space& space);
// AllocSpace interface.
class AllocSpace {
// Number of bytes currently allocated.
virtual uint64_t GetBytesAllocated() = 0;
// Number of objects currently allocated.
virtual uint64_t GetObjectsAllocated() = 0;
// Allocate num_bytes without allowing growth. If the allocation
// succeeds, the output parameter bytes_allocated will be set to the
// actually allocated bytes which is >= num_bytes.
// Alloc can be called from multiple threads at the same time and must be thread-safe.
// bytes_tl_bulk_allocated - bytes allocated in bulk ahead of time for a thread local allocation,
// if applicable. It can be
// 1) equal to bytes_allocated if it's not a thread local allocation,
// 2) greater than bytes_allocated if it's a thread local
// allocation that required a new buffer, or
// 3) zero if it's a thread local allocation in an existing
// buffer.
// This is what is to be added to Heap::num_bytes_allocated_.
virtual mirror::Object* Alloc(Thread* self, size_t num_bytes, size_t* bytes_allocated,
size_t* usable_size, size_t* bytes_tl_bulk_allocated) = 0;
// Thread-unsafe allocation for when mutators are suspended, used by the semispace collector.
virtual mirror::Object* AllocThreadUnsafe(Thread* self, size_t num_bytes, size_t* bytes_allocated,
size_t* usable_size,
size_t* bytes_tl_bulk_allocated)
EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_) {
return Alloc(self, num_bytes, bytes_allocated, usable_size, bytes_tl_bulk_allocated);
// Return the storage space required by obj.
virtual size_t AllocationSize(mirror::Object* obj, size_t* usable_size) = 0;
// Returns how many bytes were freed.
virtual size_t Free(Thread* self, mirror::Object* ptr) = 0;
// Returns how many bytes were freed.
virtual size_t FreeList(Thread* self, size_t num_ptrs, mirror::Object** ptrs) = 0;
// Revoke any sort of thread-local buffers that are used to speed up allocations for the given
// thread, if the alloc space implementation uses any.
// Returns the total free bytes in the revoked thread local runs that's to be subtracted
// from Heap::num_bytes_allocated_ or zero if unnecessary.
virtual size_t RevokeThreadLocalBuffers(Thread* thread) = 0;
// Revoke any sort of thread-local buffers that are used to speed up allocations for all the
// threads, if the alloc space implementation uses any.
// Returns the total free bytes in the revoked thread local runs that's to be subtracted
// from Heap::num_bytes_allocated_ or zero if unnecessary.
virtual size_t RevokeAllThreadLocalBuffers() = 0;
virtual void LogFragmentationAllocFailure(std::ostream& os, size_t failed_alloc_bytes) = 0;
struct SweepCallbackContext {
SweepCallbackContext(bool swap_bitmaps, space::Space* space);
const bool swap_bitmaps;
space::Space* const space;
Thread* const self;
collector::ObjectBytePair freed;
AllocSpace() {}
virtual ~AllocSpace() {}
// Continuous spaces have bitmaps, and an address range. Although not required, objects within
// continuous spaces can be marked in the card table.
class ContinuousSpace : public Space {
// Address at which the space begins.
uint8_t* Begin() const {
return begin_;
// Current address at which the space ends, which may vary as the space is filled.
uint8_t* End() const {
return end_.LoadRelaxed();
// The end of the address range covered by the space.
uint8_t* Limit() const {
return limit_;
// Change the end of the space. Be careful with use since changing the end of a space to an
// invalid value may break the GC.
void SetEnd(uint8_t* end) {
void SetLimit(uint8_t* limit) {
limit_ = limit;
// Current size of space
size_t Size() const {
return End() - Begin();
virtual accounting::ContinuousSpaceBitmap* GetLiveBitmap() const = 0;
virtual accounting::ContinuousSpaceBitmap* GetMarkBitmap() const = 0;
// Maximum which the mapped space can grow to.
virtual size_t Capacity() const {
return Limit() - Begin();
// Is object within this space? We check to see if the pointer is beyond the end first as
// continuous spaces are iterated over from low to high.
bool HasAddress(const mirror::Object* obj) const {
const uint8_t* byte_ptr = reinterpret_cast<const uint8_t*>(obj);
return byte_ptr >= Begin() && byte_ptr < Limit();
bool Contains(const mirror::Object* obj) const {
return HasAddress(obj);
virtual bool IsContinuousSpace() const {
return true;
virtual ~ContinuousSpace() {}
ContinuousSpace(const std::string& name, GcRetentionPolicy gc_retention_policy,
uint8_t* begin, uint8_t* end, uint8_t* limit) :
Space(name, gc_retention_policy), begin_(begin), end_(end), limit_(limit) {
// The beginning of the storage for fast access.
uint8_t* begin_;
// Current end of the space.
Atomic<uint8_t*> end_;
// Limit of the space.
uint8_t* limit_;
// A space where objects may be allocated higgledy-piggledy throughout virtual memory. Currently
// the card table can't cover these objects and so the write barrier shouldn't be triggered. This
// is suitable for use for large primitive arrays.
class DiscontinuousSpace : public Space {
accounting::LargeObjectBitmap* GetLiveBitmap() const {
return live_bitmap_.get();
accounting::LargeObjectBitmap* GetMarkBitmap() const {
return mark_bitmap_.get();
virtual bool IsDiscontinuousSpace() const OVERRIDE {
return true;
virtual ~DiscontinuousSpace() {}
DiscontinuousSpace(const std::string& name, GcRetentionPolicy gc_retention_policy);
std::unique_ptr<accounting::LargeObjectBitmap> live_bitmap_;
std::unique_ptr<accounting::LargeObjectBitmap> mark_bitmap_;
class MemMapSpace : public ContinuousSpace {
// Size of the space without a limit on its growth. By default this is just the Capacity, but
// for the allocation space we support starting with a small heap and then extending it.
virtual size_t NonGrowthLimitCapacity() const {
return Capacity();
MemMap* GetMemMap() {
return mem_map_.get();
const MemMap* GetMemMap() const {
return mem_map_.get();
MemMap* ReleaseMemMap() {
return mem_map_.release();
MemMapSpace(const std::string& name, MemMap* mem_map, uint8_t* begin, uint8_t* end, uint8_t* limit,
GcRetentionPolicy gc_retention_policy)
: ContinuousSpace(name, gc_retention_policy, begin, end, limit),
mem_map_(mem_map) {
// Underlying storage of the space
std::unique_ptr<MemMap> mem_map_;
// Used by the heap compaction interface to enable copying from one type of alloc space to another.
class ContinuousMemMapAllocSpace : public MemMapSpace, public AllocSpace {
bool IsAllocSpace() const OVERRIDE {
return true;
AllocSpace* AsAllocSpace() OVERRIDE {
return this;
bool IsContinuousMemMapAllocSpace() const OVERRIDE {
return true;
ContinuousMemMapAllocSpace* AsContinuousMemMapAllocSpace() {
return this;
bool HasBoundBitmaps() const EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
void BindLiveToMarkBitmap()
void UnBindBitmaps() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
// Swap the live and mark bitmaps of this space. This is used by the GC for concurrent sweeping.
void SwapBitmaps();
// Clear the space back to an empty space.
virtual void Clear() = 0;
accounting::ContinuousSpaceBitmap* GetLiveBitmap() const OVERRIDE {
return live_bitmap_.get();
accounting::ContinuousSpaceBitmap* GetMarkBitmap() const OVERRIDE {
return mark_bitmap_.get();
collector::ObjectBytePair Sweep(bool swap_bitmaps);
virtual accounting::ContinuousSpaceBitmap::SweepCallback* GetSweepCallback() = 0;
std::unique_ptr<accounting::ContinuousSpaceBitmap> live_bitmap_;
std::unique_ptr<accounting::ContinuousSpaceBitmap> mark_bitmap_;
std::unique_ptr<accounting::ContinuousSpaceBitmap> temp_bitmap_;
ContinuousMemMapAllocSpace(const std::string& name, MemMap* mem_map, uint8_t* begin,
uint8_t* end, uint8_t* limit, GcRetentionPolicy gc_retention_policy)
: MemMapSpace(name, mem_map, begin, end, limit, gc_retention_policy) {
friend class gc::Heap;
} // namespace space
} // namespace gc
} // namespace art