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* Copyright (C) 2008 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 <iosfwd>
#include <string>
#include <vector>
#include "allocator_type.h"
#include "arch/instruction_set.h"
#include "atomic.h"
#include "base/timing_logger.h"
#include "gc/accounting/atomic_stack.h"
#include "gc/accounting/card_table.h"
#include "gc/accounting/read_barrier_table.h"
#include "gc/gc_cause.h"
#include "gc/collector/garbage_collector.h"
#include "gc/collector/gc_type.h"
#include "gc/collector_type.h"
#include "gc/space/large_object_space.h"
#include "globals.h"
#include "jni.h"
#include "object_callbacks.h"
#include "offsets.h"
#include "reference_processor.h"
#include "safe_map.h"
#include "thread_pool.h"
#include "verify_object.h"
namespace art {
class ConditionVariable;
class Mutex;
class StackVisitor;
class Thread;
class TimingLogger;
namespace mirror {
class Class;
class Object;
} // namespace mirror
namespace gc {
class ReferenceProcessor;
class TaskProcessor;
namespace accounting {
class HeapBitmap;
class ModUnionTable;
class RememberedSet;
} // namespace accounting
namespace collector {
class ConcurrentCopying;
class GarbageCollector;
class MarkCompact;
class MarkSweep;
class SemiSpace;
} // namespace collector
namespace allocator {
class RosAlloc;
} // namespace allocator
namespace space {
class AllocSpace;
class BumpPointerSpace;
class ContinuousMemMapAllocSpace;
class DiscontinuousSpace;
class DlMallocSpace;
class ImageSpace;
class LargeObjectSpace;
class MallocSpace;
class RegionSpace;
class RosAllocSpace;
class Space;
class SpaceTest;
class ZygoteSpace;
} // namespace space
class AgeCardVisitor {
uint8_t operator()(uint8_t card) const {
if (card == accounting::CardTable::kCardDirty) {
return card - 1;
} else {
return 0;
enum HomogeneousSpaceCompactResult {
// Success.
// Reject due to disabled moving GC.
// System is shutting down.
// If true, use rosalloc/RosAllocSpace instead of dlmalloc/DlMallocSpace
static constexpr bool kUseRosAlloc = true;
// If true, use thread-local allocation stack.
static constexpr bool kUseThreadLocalAllocationStack = true;
// The process state passed in from the activity manager, used to determine when to do trimming
// and compaction.
enum ProcessState {
kProcessStateJankPerceptible = 0,
kProcessStateJankImperceptible = 1,
std::ostream& operator<<(std::ostream& os, const ProcessState& process_state);
class Heap {
// If true, measure the total allocation time.
static constexpr bool kMeasureAllocationTime = false;
static constexpr size_t kDefaultStartingSize = kPageSize;
static constexpr size_t kDefaultInitialSize = 2 * MB;
static constexpr size_t kDefaultMaximumSize = 256 * MB;
static constexpr size_t kDefaultNonMovingSpaceCapacity = 64 * MB;
static constexpr size_t kDefaultMaxFree = 2 * MB;
static constexpr size_t kDefaultMinFree = kDefaultMaxFree / 4;
static constexpr size_t kDefaultLongPauseLogThreshold = MsToNs(5);
static constexpr size_t kDefaultLongGCLogThreshold = MsToNs(100);
static constexpr size_t kDefaultTLABSize = 256 * KB;
static constexpr double kDefaultTargetUtilization = 0.5;
static constexpr double kDefaultHeapGrowthMultiplier = 2.0;
// Primitive arrays larger than this size are put in the large object space.
static constexpr size_t kDefaultLargeObjectThreshold = 3 * kPageSize;
// Whether or not parallel GC is enabled. If not, then we never create the thread pool.
static constexpr bool kDefaultEnableParallelGC = false;
// Whether or not we use the free list large object space. Only use it if USE_ART_LOW_4G_ALLOCATOR
// since this means that we have to use the slow msync loop in MemMap::MapAnonymous.
static constexpr space::LargeObjectSpaceType kDefaultLargeObjectSpaceType =
: space::LargeObjectSpaceType::kMap;
// Used so that we don't overflow the allocation time atomic integer.
static constexpr size_t kTimeAdjust = 1024;
// How often we allow heap trimming to happen (nanoseconds).
static constexpr uint64_t kHeapTrimWait = MsToNs(5000);
// How long we wait after a transition request to perform a collector transition (nanoseconds).
static constexpr uint64_t kCollectorTransitionWait = MsToNs(5000);
// Create a heap with the requested sizes. The possible empty
// image_file_names names specify Spaces to load based on
// ImageWriter output.
explicit Heap(size_t initial_size, size_t growth_limit, size_t min_free,
size_t max_free, double target_utilization,
double foreground_heap_growth_multiplier, size_t capacity,
size_t non_moving_space_capacity,
const std::string& original_image_file_name,
InstructionSet image_instruction_set,
CollectorType foreground_collector_type, CollectorType background_collector_type,
space::LargeObjectSpaceType large_object_space_type, size_t large_object_threshold,
size_t parallel_gc_threads, size_t conc_gc_threads, bool low_memory_mode,
size_t long_pause_threshold, size_t long_gc_threshold,
bool ignore_max_footprint, bool use_tlab,
bool verify_pre_gc_heap, bool verify_pre_sweeping_heap, bool verify_post_gc_heap,
bool verify_pre_gc_rosalloc, bool verify_pre_sweeping_rosalloc,
bool verify_post_gc_rosalloc, bool use_homogeneous_space_compaction,
uint64_t min_interval_homogeneous_space_compaction_by_oom);
// Allocates and initializes storage for an object instance.
template <bool kInstrumented, typename PreFenceVisitor>
mirror::Object* AllocObject(Thread* self, mirror::Class* klass, size_t num_bytes,
const PreFenceVisitor& pre_fence_visitor)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return AllocObjectWithAllocator<kInstrumented, true>(self, klass, num_bytes,
template <bool kInstrumented, typename PreFenceVisitor>
mirror::Object* AllocNonMovableObject(Thread* self, mirror::Class* klass, size_t num_bytes,
const PreFenceVisitor& pre_fence_visitor)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return AllocObjectWithAllocator<kInstrumented, true>(self, klass, num_bytes,
template <bool kInstrumented, bool kCheckLargeObject, typename PreFenceVisitor>
ALWAYS_INLINE mirror::Object* AllocObjectWithAllocator(
Thread* self, mirror::Class* klass, size_t byte_count, AllocatorType allocator,
const PreFenceVisitor& pre_fence_visitor)
AllocatorType GetCurrentAllocator() const {
return current_allocator_;
AllocatorType GetCurrentNonMovingAllocator() const {
return current_non_moving_allocator_;
// Visit all of the live objects in the heap.
void VisitObjects(ObjectCallback callback, void* arg)
void VisitObjectsPaused(ObjectCallback callback, void* arg)
void CheckPreconditionsForAllocObject(mirror::Class* c, size_t byte_count)
void RegisterNativeAllocation(JNIEnv* env, size_t bytes);
void RegisterNativeFree(JNIEnv* env, size_t bytes);
// Change the allocator, updates entrypoints.
void ChangeAllocator(AllocatorType allocator)
// Transition the garbage collector during runtime, may copy objects from one space to another.
void TransitionCollector(CollectorType collector_type);
// Change the collector to be one of the possible options (MS, CMS, SS).
void ChangeCollector(CollectorType collector_type)
// The given reference is believed to be to an object in the Java heap, check the soundness of it.
// TODO: NO_THREAD_SAFETY_ANALYSIS since we call this everywhere and it is impossible to find a
// proper lock ordering for it.
void VerifyObjectBody(mirror::Object* o) NO_THREAD_SAFETY_ANALYSIS;
// Check sanity of all live references.
void VerifyHeap() LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// Returns how many failures occured.
size_t VerifyHeapReferences(bool verify_referents = true)
bool VerifyMissingCardMarks()
EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// A weaker test than IsLiveObject or VerifyObject that doesn't require the heap lock,
// and doesn't abort on error, allowing the caller to report more
// meaningful diagnostics.
bool IsValidObjectAddress(const mirror::Object* obj) const
// Faster alternative to IsHeapAddress since finding if an object is in the large object space is
// very slow.
bool IsNonDiscontinuousSpaceHeapAddress(const mirror::Object* obj) const
// Returns true if 'obj' is a live heap object, false otherwise (including for invalid addresses).
// Requires the heap lock to be held.
bool IsLiveObjectLocked(mirror::Object* obj, bool search_allocation_stack = true,
bool search_live_stack = true, bool sorted = false)
SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_, Locks::mutator_lock_);
// Returns true if there is any chance that the object (obj) will move.
bool IsMovableObject(const mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Enables us to compacting GC until objects are released.
void IncrementDisableMovingGC(Thread* self);
void DecrementDisableMovingGC(Thread* self);
// Clear all of the mark bits, doesn't clear bitmaps which have the same live bits as mark bits.
void ClearMarkedObjects() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
// Initiates an explicit garbage collection.
void CollectGarbage(bool clear_soft_references);
// Does a concurrent GC, should only be called by the GC daemon thread
// through runtime.
void ConcurrentGC(Thread* self) LOCKS_EXCLUDED(Locks::runtime_shutdown_lock_);
// Implements VMDebug.countInstancesOfClass and JDWP VM_InstanceCount.
// The boolean decides whether to use IsAssignableFrom or == when comparing classes.
void CountInstances(const std::vector<mirror::Class*>& classes, bool use_is_assignable_from,
uint64_t* counts)
// Implements JDWP RT_Instances.
void GetInstances(mirror::Class* c, int32_t max_count, std::vector<mirror::Object*>& instances)
// Implements JDWP OR_ReferringObjects.
void GetReferringObjects(mirror::Object* o, int32_t max_count, std::vector<mirror::Object*>& referring_objects)
// Removes the growth limit on the alloc space so it may grow to its maximum capacity. Used to
// implement dalvik.system.VMRuntime.clearGrowthLimit.
void ClearGrowthLimit();
// Make the current growth limit the new maximum capacity, unmaps pages at the end of spaces
// which will never be used. Used to implement dalvik.system.VMRuntime.clampGrowthLimit.
void ClampGrowthLimit() LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// Target ideal heap utilization ratio, implements
// dalvik.system.VMRuntime.getTargetHeapUtilization.
double GetTargetHeapUtilization() const {
return target_utilization_;
// Data structure memory usage tracking.
void RegisterGCAllocation(size_t bytes);
void RegisterGCDeAllocation(size_t bytes);
// Set the heap's private space pointers to be the same as the space based on it's type. Public
// due to usage by tests.
void SetSpaceAsDefault(space::ContinuousSpace* continuous_space)
void AddSpace(space::Space* space) LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
void RemoveSpace(space::Space* space) LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// Set target ideal heap utilization ratio, implements
// dalvik.system.VMRuntime.setTargetHeapUtilization.
void SetTargetHeapUtilization(float target);
// For the alloc space, sets the maximum number of bytes that the heap is allowed to allocate
// from the system. Doesn't allow the space to exceed its growth limit.
void SetIdealFootprint(size_t max_allowed_footprint);
// Blocks the caller until the garbage collector becomes idle and returns the type of GC we
// waited for.
collector::GcType WaitForGcToComplete(GcCause cause, Thread* self)
// Update the heap's process state to a new value, may cause compaction to occur.
void UpdateProcessState(ProcessState process_state);
const std::vector<space::ContinuousSpace*>& GetContinuousSpaces() const {
return continuous_spaces_;
const std::vector<space::DiscontinuousSpace*>& GetDiscontinuousSpaces() const {
return discontinuous_spaces_;
const collector::Iteration* GetCurrentGcIteration() const {
return &current_gc_iteration_;
collector::Iteration* GetCurrentGcIteration() {
return &current_gc_iteration_;
// Enable verification of object references when the runtime is sufficiently initialized.
void EnableObjectValidation() {
verify_object_mode_ = kVerifyObjectSupport;
if (verify_object_mode_ > kVerifyObjectModeDisabled) {
// Disable object reference verification for image writing.
void DisableObjectValidation() {
verify_object_mode_ = kVerifyObjectModeDisabled;
// Other checks may be performed if we know the heap should be in a sane state.
bool IsObjectValidationEnabled() const {
return verify_object_mode_ > kVerifyObjectModeDisabled;
// Returns true if low memory mode is enabled.
bool IsLowMemoryMode() const {
return low_memory_mode_;
// Returns the heap growth multiplier, this affects how much we grow the heap after a GC.
// Scales heap growth, min free, and max free.
double HeapGrowthMultiplier() const;
// Freed bytes can be negative in cases where we copy objects from a compacted space to a
// free-list backed space.
void RecordFree(uint64_t freed_objects, int64_t freed_bytes);
// Record the bytes freed by thread-local buffer revoke.
void RecordFreeRevoke();
// Must be called if a field of an Object in the heap changes, and before any GC safe-point.
// The call is not needed if null is stored in the field.
ALWAYS_INLINE void WriteBarrierField(const mirror::Object* dst, MemberOffset /*offset*/,
const mirror::Object* /*new_value*/) {
// Write barrier for array operations that update many field positions
ALWAYS_INLINE void WriteBarrierArray(const mirror::Object* dst, int /*start_offset*/,
size_t /*length TODO: element_count or byte_count?*/) {
ALWAYS_INLINE void WriteBarrierEveryFieldOf(const mirror::Object* obj) {
accounting::CardTable* GetCardTable() const {
return card_table_.get();
accounting::ReadBarrierTable* GetReadBarrierTable() const {
return rb_table_.get();
void AddFinalizerReference(Thread* self, mirror::Object** object);
// Returns the number of bytes currently allocated.
size_t GetBytesAllocated() const {
return num_bytes_allocated_.LoadSequentiallyConsistent();
// Returns the number of objects currently allocated.
size_t GetObjectsAllocated() const LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// Returns the total number of objects allocated since the heap was created.
uint64_t GetObjectsAllocatedEver() const;
// Returns the total number of bytes allocated since the heap was created.
uint64_t GetBytesAllocatedEver() const;
// Returns the total number of objects freed since the heap was created.
uint64_t GetObjectsFreedEver() const {
return total_objects_freed_ever_;
// Returns the total number of bytes freed since the heap was created.
uint64_t GetBytesFreedEver() const {
return total_bytes_freed_ever_;
// Implements java.lang.Runtime.maxMemory, returning the maximum amount of memory a program can
// consume. For a regular VM this would relate to the -Xmx option and would return -1 if no Xmx
// were specified. Android apps start with a growth limit (small heap size) which is
// cleared/extended for large apps.
size_t GetMaxMemory() const {
// There is some race conditions in the allocation code that can cause bytes allocated to
// become larger than growth_limit_ in rare cases.
return std::max(GetBytesAllocated(), growth_limit_);
// Implements java.lang.Runtime.totalMemory, returning approximate amount of memory currently
// consumed by an application.
size_t GetTotalMemory() const;
// Returns approximately how much free memory we have until the next GC happens.
size_t GetFreeMemoryUntilGC() const {
return max_allowed_footprint_ - GetBytesAllocated();
// Returns approximately how much free memory we have until the next OOME happens.
size_t GetFreeMemoryUntilOOME() const {
return growth_limit_ - GetBytesAllocated();
// Returns how much free memory we have until we need to grow the heap to perform an allocation.
// Similar to GetFreeMemoryUntilGC. Implements java.lang.Runtime.freeMemory.
size_t GetFreeMemory() const {
size_t byte_allocated = num_bytes_allocated_.LoadSequentiallyConsistent();
size_t total_memory = GetTotalMemory();
// Make sure we don't get a negative number.
return total_memory - std::min(total_memory, byte_allocated);
// get the space that corresponds to an object's address. Current implementation searches all
// spaces in turn. If fail_ok is false then failing to find a space will cause an abort.
// TODO: consider using faster data structure like binary tree.
space::ContinuousSpace* FindContinuousSpaceFromObject(const mirror::Object*, bool fail_ok) const;
space::DiscontinuousSpace* FindDiscontinuousSpaceFromObject(const mirror::Object*,
bool fail_ok) const;
space::Space* FindSpaceFromObject(const mirror::Object*, bool fail_ok) const;
void DumpForSigQuit(std::ostream& os);
// Do a pending collector transition.
void DoPendingCollectorTransition();
// Deflate monitors, ... and trim the spaces.
void Trim(Thread* self) LOCKS_EXCLUDED(gc_complete_lock_);
void RevokeThreadLocalBuffers(Thread* thread);
void RevokeRosAllocThreadLocalBuffers(Thread* thread);
void RevokeAllThreadLocalBuffers();
void AssertThreadLocalBuffersAreRevoked(Thread* thread);
void AssertAllBumpPointerSpaceThreadLocalBuffersAreRevoked();
void RosAllocVerification(TimingLogger* timings, const char* name)
accounting::HeapBitmap* GetLiveBitmap() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
return live_bitmap_.get();
accounting::HeapBitmap* GetMarkBitmap() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
return mark_bitmap_.get();
accounting::ObjectStack* GetLiveStack() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
return live_stack_.get();
// Mark and empty stack.
void FlushAllocStack()
// Revoke all the thread-local allocation stacks.
void RevokeAllThreadLocalAllocationStacks(Thread* self)
LOCKS_EXCLUDED(Locks::runtime_shutdown_lock_, Locks::thread_list_lock_);
// Mark all the objects in the allocation stack in the specified bitmap.
// TODO: Refactor?
void MarkAllocStack(accounting::SpaceBitmap<kObjectAlignment>* bitmap1,
accounting::SpaceBitmap<kObjectAlignment>* bitmap2,
accounting::SpaceBitmap<kLargeObjectAlignment>* large_objects,
accounting::ObjectStack* stack)
// Mark the specified allocation stack as live.
void MarkAllocStackAsLive(accounting::ObjectStack* stack)
// 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;
// Permenantly disable moving garbage collection.
void DisableMovingGc();
space::DlMallocSpace* GetDlMallocSpace() const {
return dlmalloc_space_;
space::RosAllocSpace* GetRosAllocSpace() const {
return rosalloc_space_;
// Return the corresponding rosalloc space.
space::RosAllocSpace* GetRosAllocSpace(gc::allocator::RosAlloc* rosalloc) const;
space::MallocSpace* GetNonMovingSpace() const {
return non_moving_space_;
space::LargeObjectSpace* GetLargeObjectsSpace() const {
return large_object_space_;
// Returns the free list space that may contain movable objects (the
// one that's not the non-moving space), either rosalloc_space_ or
// dlmalloc_space_.
space::MallocSpace* GetPrimaryFreeListSpace() {
if (kUseRosAlloc) {
DCHECK(rosalloc_space_ != nullptr);
// reinterpret_cast is necessary as the space class hierarchy
// isn't known (#included) yet here.
return reinterpret_cast<space::MallocSpace*>(rosalloc_space_);
} else {
DCHECK(dlmalloc_space_ != nullptr);
return reinterpret_cast<space::MallocSpace*>(dlmalloc_space_);
std::string DumpSpaces() const WARN_UNUSED;
void DumpSpaces(std::ostream& stream) const;
// Dump object should only be used by the signal handler.
void DumpObject(std::ostream& stream, mirror::Object* obj) NO_THREAD_SAFETY_ANALYSIS;
// Safe version of pretty type of which check to make sure objects are heap addresses.
std::string SafeGetClassDescriptor(mirror::Class* klass) NO_THREAD_SAFETY_ANALYSIS;
std::string SafePrettyTypeOf(mirror::Object* obj) NO_THREAD_SAFETY_ANALYSIS;
// GC performance measuring
void DumpGcPerformanceInfo(std::ostream& os);
// Returns true if we currently care about pause times.
bool CareAboutPauseTimes() const {
return process_state_ == kProcessStateJankPerceptible;
// Thread pool.
void CreateThreadPool();
void DeleteThreadPool();
ThreadPool* GetThreadPool() {
return thread_pool_.get();
size_t GetParallelGCThreadCount() const {
return parallel_gc_threads_;
size_t GetConcGCThreadCount() const {
return conc_gc_threads_;
accounting::ModUnionTable* FindModUnionTableFromSpace(space::Space* space);
void AddModUnionTable(accounting::ModUnionTable* mod_union_table);
accounting::RememberedSet* FindRememberedSetFromSpace(space::Space* space);
void AddRememberedSet(accounting::RememberedSet* remembered_set);
// Also deletes the remebered set.
void RemoveRememberedSet(space::Space* space);
bool IsCompilingBoot() const;
bool HasImageSpace() const;
ReferenceProcessor* GetReferenceProcessor() {
return &reference_processor_;
TaskProcessor* GetTaskProcessor() {
return task_processor_.get();
bool HasZygoteSpace() const {
return zygote_space_ != nullptr;
collector::ConcurrentCopying* ConcurrentCopyingCollector() {
return concurrent_copying_collector_;
CollectorType CurrentCollectorType() {
return collector_type_;
bool IsGcConcurrentAndMoving() const {
if (IsGcConcurrent() && IsMovingGc(collector_type_)) {
// Assume no transition when a concurrent moving collector is used.
DCHECK_EQ(collector_type_, foreground_collector_type_);
DCHECK_EQ(foreground_collector_type_, background_collector_type_)
<< "Assume no transition such that collector_type_ won't change";
return true;
return false;
bool IsMovingGCDisabled(Thread* self) {
MutexLock mu(self, *gc_complete_lock_);
return disable_moving_gc_count_ > 0;
// Request an asynchronous trim.
void RequestTrim(Thread* self) LOCKS_EXCLUDED(pending_task_lock_);
// Request asynchronous GC.
void RequestConcurrentGC(Thread* self) LOCKS_EXCLUDED(pending_task_lock_);
// Whether or not we may use a garbage collector, used so that we only create collectors we need.
bool MayUseCollector(CollectorType type) const;
// Used by tests to reduce timinig-dependent flakiness in OOME behavior.
void SetMinIntervalHomogeneousSpaceCompactionByOom(uint64_t interval) {
min_interval_homogeneous_space_compaction_by_oom_ = interval;
// Helpers for android.os.Debug.getRuntimeStat().
uint64_t GetGcCount() const;
uint64_t GetGcTime() const;
uint64_t GetBlockingGcCount() const;
uint64_t GetBlockingGcTime() const;
void DumpGcCountRateHistogram(std::ostream& os) const;
void DumpBlockingGcCountRateHistogram(std::ostream& os) const;
class ConcurrentGCTask;
class CollectorTransitionTask;
class HeapTrimTask;
// Compact source space to target space. Returns the collector used.
collector::GarbageCollector* Compact(space::ContinuousMemMapAllocSpace* target_space,
space::ContinuousMemMapAllocSpace* source_space,
GcCause gc_cause)
void LogGC(GcCause gc_cause, collector::GarbageCollector* collector);
void FinishGC(Thread* self, collector::GcType gc_type) LOCKS_EXCLUDED(gc_complete_lock_);
// Create a mem map with a preferred base address.
static MemMap* MapAnonymousPreferredAddress(const char* name, uint8_t* request_begin,
size_t capacity, std::string* out_error_str);
bool SupportHSpaceCompaction() const {
// Returns true if we can do hspace compaction
return main_space_backup_ != nullptr;
static ALWAYS_INLINE bool AllocatorHasAllocationStack(AllocatorType allocator_type) {
allocator_type != kAllocatorTypeBumpPointer &&
allocator_type != kAllocatorTypeTLAB &&
allocator_type != kAllocatorTypeRegion &&
allocator_type != kAllocatorTypeRegionTLAB;
static ALWAYS_INLINE bool AllocatorMayHaveConcurrentGC(AllocatorType allocator_type) {
allocator_type != kAllocatorTypeBumpPointer &&
allocator_type != kAllocatorTypeTLAB;
static bool IsMovingGc(CollectorType collector_type) {
return collector_type == kCollectorTypeSS || collector_type == kCollectorTypeGSS ||
collector_type == kCollectorTypeCC || collector_type == kCollectorTypeMC ||
collector_type == kCollectorTypeHomogeneousSpaceCompact;
bool ShouldAllocLargeObject(mirror::Class* c, size_t byte_count) const
ALWAYS_INLINE void CheckConcurrentGC(Thread* self, size_t new_num_bytes_allocated,
mirror::Object** obj)
accounting::ObjectStack* GetMarkStack() {
return mark_stack_.get();
// We don't force this to be inlined since it is a slow path.
template <bool kInstrumented, typename PreFenceVisitor>
mirror::Object* AllocLargeObject(Thread* self, mirror::Class** klass, size_t byte_count,
const PreFenceVisitor& pre_fence_visitor)
// Handles Allocate()'s slow allocation path with GC involved after
// an initial allocation attempt failed.
mirror::Object* AllocateInternalWithGc(Thread* self, AllocatorType allocator, size_t num_bytes,
size_t* bytes_allocated, size_t* usable_size,
size_t* bytes_tl_bulk_allocated,
mirror::Class** klass)
// Allocate into a specific space.
mirror::Object* AllocateInto(Thread* self, space::AllocSpace* space, mirror::Class* c,
size_t bytes)
// Need to do this with mutators paused so that somebody doesn't accidentally allocate into the
// wrong space.
void SwapSemiSpaces() EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_);
// Try to allocate a number of bytes, this function never does any GCs. Needs to be inlined so
// that the switch statement is constant optimized in the entrypoints.
template <const bool kInstrumented, const bool kGrow>
ALWAYS_INLINE mirror::Object* TryToAllocate(Thread* self, AllocatorType allocator_type,
size_t alloc_size, size_t* bytes_allocated,
size_t* usable_size,
size_t* bytes_tl_bulk_allocated)
void ThrowOutOfMemoryError(Thread* self, size_t byte_count, AllocatorType allocator_type)
template <bool kGrow>
ALWAYS_INLINE bool IsOutOfMemoryOnAllocation(AllocatorType allocator_type, size_t alloc_size);
// Returns true if the address passed in is within the address range of a continuous space.
bool IsValidContinuousSpaceObjectAddress(const mirror::Object* obj) const
// Run the finalizers.
void RunFinalization(JNIEnv* env);
// Blocks the caller until the garbage collector becomes idle and returns the type of GC we
// waited for.
collector::GcType WaitForGcToCompleteLocked(GcCause cause, Thread* self)
void RequestCollectorTransition(CollectorType desired_collector_type, uint64_t delta_time)
void RequestConcurrentGCAndSaveObject(Thread* self, mirror::Object** obj)
bool IsGCRequestPending() const;
// Sometimes CollectGarbageInternal decides to run a different Gc than you requested. Returns
// which type of Gc was actually ran.
collector::GcType CollectGarbageInternal(collector::GcType gc_plan, GcCause gc_cause,
bool clear_soft_references)
void PreGcVerification(collector::GarbageCollector* gc)
void PreGcVerificationPaused(collector::GarbageCollector* gc)
void PrePauseRosAllocVerification(collector::GarbageCollector* gc)
void PreSweepingGcVerification(collector::GarbageCollector* gc)
void PostGcVerification(collector::GarbageCollector* gc)
void PostGcVerificationPaused(collector::GarbageCollector* gc)
// Update the watermark for the native allocated bytes based on the current number of native
// bytes allocated and the target utilization ratio.
void UpdateMaxNativeFootprint();
// Find a collector based on GC type.
collector::GarbageCollector* FindCollectorByGcType(collector::GcType gc_type);
// Create a new alloc space and compact default alloc space to it.
HomogeneousSpaceCompactResult PerformHomogeneousSpaceCompact();
// Create the main free list malloc space, either a RosAlloc space or DlMalloc space.
void CreateMainMallocSpace(MemMap* mem_map, size_t initial_size, size_t growth_limit,
size_t capacity);
// Create a malloc space based on a mem map. Does not set the space as default.
space::MallocSpace* CreateMallocSpaceFromMemMap(MemMap* mem_map, size_t initial_size,
size_t growth_limit, size_t capacity,
const char* name, bool can_move_objects);
// Given the current contents of the alloc space, increase the allowed heap footprint to match
// the target utilization ratio. This should only be called immediately after a full garbage
// collection. bytes_allocated_before_gc is used to measure bytes / second for the period which
// the GC was run.
void GrowForUtilization(collector::GarbageCollector* collector_ran,
uint64_t bytes_allocated_before_gc = 0);
size_t GetPercentFree();
static void VerificationCallback(mirror::Object* obj, void* arg)
// Swap the allocation stack with the live stack.
void SwapStacks(Thread* self) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Clear cards and update the mod union table. When process_alloc_space_cards is true,
// if clear_alloc_space_cards is true, then we clear cards instead of ageing them. We do
// not process the alloc space if process_alloc_space_cards is false.
void ProcessCards(TimingLogger* timings, bool use_rem_sets, bool process_alloc_space_cards,
bool clear_alloc_space_cards);
// Push an object onto the allocation stack.
void PushOnAllocationStack(Thread* self, mirror::Object** obj)
void PushOnAllocationStackWithInternalGC(Thread* self, mirror::Object** obj)
void PushOnThreadLocalAllocationStackWithInternalGC(Thread* thread, mirror::Object** obj)
void ClearConcurrentGCRequest();
void ClearPendingTrim(Thread* self) LOCKS_EXCLUDED(pending_task_lock_);
void ClearPendingCollectorTransition(Thread* self) LOCKS_EXCLUDED(pending_task_lock_);
// What kind of concurrency behavior is the runtime after? Currently true for concurrent mark
// sweep GC, false for other GC types.
bool IsGcConcurrent() const ALWAYS_INLINE {
return collector_type_ == kCollectorTypeCMS || collector_type_ == kCollectorTypeCC;
// Trim the managed and native spaces by releasing unused memory back to the OS.
void TrimSpaces(Thread* self) LOCKS_EXCLUDED(gc_complete_lock_);
// Trim 0 pages at the end of reference tables.
void TrimIndirectReferenceTables(Thread* self);
void VisitObjectsInternal(ObjectCallback callback, void* arg)
void VisitObjectsInternalRegionSpace(ObjectCallback callback, void* arg)
void UpdateGcCountRateHistograms() EXCLUSIVE_LOCKS_REQUIRED(gc_complete_lock_);
// All-known continuous spaces, where objects lie within fixed bounds.
std::vector<space::ContinuousSpace*> continuous_spaces_;
// All-known discontinuous spaces, where objects may be placed throughout virtual memory.
std::vector<space::DiscontinuousSpace*> discontinuous_spaces_;
// All-known alloc spaces, where objects may be or have been allocated.
std::vector<space::AllocSpace*> alloc_spaces_;
// A space where non-movable objects are allocated, when compaction is enabled it contains
// Classes, ArtMethods, ArtFields, and non moving objects.
space::MallocSpace* non_moving_space_;
// Space which we use for the kAllocatorTypeROSAlloc.
space::RosAllocSpace* rosalloc_space_;
// Space which we use for the kAllocatorTypeDlMalloc.
space::DlMallocSpace* dlmalloc_space_;
// The main space is the space which the GC copies to and from on process state updates. This
// space is typically either the dlmalloc_space_ or the rosalloc_space_.
space::MallocSpace* main_space_;
// The large object space we are currently allocating into.
space::LargeObjectSpace* large_object_space_;
// The card table, dirtied by the write barrier.
std::unique_ptr<accounting::CardTable> card_table_;
std::unique_ptr<accounting::ReadBarrierTable> rb_table_;
// A mod-union table remembers all of the references from the it's space to other spaces.
AllocationTrackingSafeMap<space::Space*, accounting::ModUnionTable*, kAllocatorTagHeap>
// A remembered set remembers all of the references from the it's space to the target space.
AllocationTrackingSafeMap<space::Space*, accounting::RememberedSet*, kAllocatorTagHeap>
// The current collector type.
CollectorType collector_type_;
// Which collector we use when the app is in the foreground.
CollectorType foreground_collector_type_;
// Which collector we will use when the app is notified of a transition to background.
CollectorType background_collector_type_;
// Desired collector type, heap trimming daemon transitions the heap if it is != collector_type_.
CollectorType desired_collector_type_;
// Lock which guards pending tasks.
Mutex* pending_task_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
// How many GC threads we may use for paused parts of garbage collection.
const size_t parallel_gc_threads_;
// How many GC threads we may use for unpaused parts of garbage collection.
const size_t conc_gc_threads_;
// Boolean for if we are in low memory mode.
const bool low_memory_mode_;
// If we get a pause longer than long pause log threshold, then we print out the GC after it
// finishes.
const size_t long_pause_log_threshold_;
// If we get a GC longer than long GC log threshold, then we print out the GC after it finishes.
const size_t long_gc_log_threshold_;
// If we ignore the max footprint it lets the heap grow until it hits the heap capacity, this is
// useful for benchmarking since it reduces time spent in GC to a low %.
const bool ignore_max_footprint_;
// Lock which guards zygote space creation.
Mutex zygote_creation_lock_;
// Non-null iff we have a zygote space. Doesn't contain the large objects allocated before
// zygote space creation.
space::ZygoteSpace* zygote_space_;
// Minimum allocation size of large object.
size_t large_object_threshold_;
// Guards access to the state of GC, associated conditional variable is used to signal when a GC
// completes.
Mutex* gc_complete_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
std::unique_ptr<ConditionVariable> gc_complete_cond_ GUARDED_BY(gc_complete_lock_);
// Reference processor;
ReferenceProcessor reference_processor_;
// Task processor, proxies heap trim requests to the daemon threads.
std::unique_ptr<TaskProcessor> task_processor_;
// True while the garbage collector is running.
volatile CollectorType collector_type_running_ GUARDED_BY(gc_complete_lock_);
// Last Gc type we ran. Used by WaitForConcurrentGc to know which Gc was waited on.
volatile collector::GcType last_gc_type_ GUARDED_BY(gc_complete_lock_);
collector::GcType next_gc_type_;
// Maximum size that the heap can reach.
size_t capacity_;
// The size the heap is limited to. This is initially smaller than capacity, but for largeHeap
// programs it is "cleared" making it the same as capacity.
size_t growth_limit_;
// When the number of bytes allocated exceeds the footprint TryAllocate returns null indicating
// a GC should be triggered.
size_t max_allowed_footprint_;
// The watermark at which a concurrent GC is requested by registerNativeAllocation.
size_t native_footprint_gc_watermark_;
// Whether or not we need to run finalizers in the next native allocation.
bool native_need_to_run_finalization_;
// Whether or not we currently care about pause times.
ProcessState process_state_;
// When num_bytes_allocated_ exceeds this amount then a concurrent GC should be requested so that
// it completes ahead of an allocation failing.
size_t concurrent_start_bytes_;
// Since the heap was created, how many bytes have been freed.
uint64_t total_bytes_freed_ever_;
// Since the heap was created, how many objects have been freed.
uint64_t total_objects_freed_ever_;
// Number of bytes allocated. Adjusted after each allocation and free.
Atomic<size_t> num_bytes_allocated_;
// Bytes which are allocated and managed by native code but still need to be accounted for.
Atomic<size_t> native_bytes_allocated_;
// Number of bytes freed by thread local buffer revokes. This will
// cancel out the ahead-of-time bulk counting of bytes allocated in
// rosalloc thread-local buffers. It is temporarily accumulated
// here to be subtracted from num_bytes_allocated_ later at the next
// GC.
Atomic<size_t> num_bytes_freed_revoke_;
// Info related to the current or previous GC iteration.
collector::Iteration current_gc_iteration_;
// Heap verification flags.
const bool verify_missing_card_marks_;
const bool verify_system_weaks_;
const bool verify_pre_gc_heap_;
const bool verify_pre_sweeping_heap_;
const bool verify_post_gc_heap_;
const bool verify_mod_union_table_;
bool verify_pre_gc_rosalloc_;
bool verify_pre_sweeping_rosalloc_;
bool verify_post_gc_rosalloc_;
// RAII that temporarily disables the rosalloc verification during
// the zygote fork.
class ScopedDisableRosAllocVerification {
Heap* const heap_;
const bool orig_verify_pre_gc_;
const bool orig_verify_pre_sweeping_;
const bool orig_verify_post_gc_;
explicit ScopedDisableRosAllocVerification(Heap* heap)
: heap_(heap),
orig_verify_post_gc_(heap_->verify_post_gc_rosalloc_) {
heap_->verify_pre_gc_rosalloc_ = false;
heap_->verify_pre_sweeping_rosalloc_ = false;
heap_->verify_post_gc_rosalloc_ = false;
~ScopedDisableRosAllocVerification() {
heap_->verify_pre_gc_rosalloc_ = orig_verify_pre_gc_;
heap_->verify_pre_sweeping_rosalloc_ = orig_verify_pre_sweeping_;
heap_->verify_post_gc_rosalloc_ = orig_verify_post_gc_;
// Parallel GC data structures.
std::unique_ptr<ThreadPool> thread_pool_;
// Estimated allocation rate (bytes / second). Computed between the time of the last GC cycle
// and the start of the current one.
uint64_t allocation_rate_;
// For a GC cycle, a bitmap that is set corresponding to the
std::unique_ptr<accounting::HeapBitmap> live_bitmap_ GUARDED_BY(Locks::heap_bitmap_lock_);
std::unique_ptr<accounting::HeapBitmap> mark_bitmap_ GUARDED_BY(Locks::heap_bitmap_lock_);
// Mark stack that we reuse to avoid re-allocating the mark stack.
std::unique_ptr<accounting::ObjectStack> mark_stack_;
// Allocation stack, new allocations go here so that we can do sticky mark bits. This enables us
// to use the live bitmap as the old mark bitmap.
const size_t max_allocation_stack_size_;
std::unique_ptr<accounting::ObjectStack> allocation_stack_;
// Second allocation stack so that we can process allocation with the heap unlocked.
std::unique_ptr<accounting::ObjectStack> live_stack_;
// Allocator type.
AllocatorType current_allocator_;
const AllocatorType current_non_moving_allocator_;
// Which GCs we run in order when we an allocation fails.
std::vector<collector::GcType> gc_plan_;
// Bump pointer spaces.
space::BumpPointerSpace* bump_pointer_space_;
// Temp space is the space which the semispace collector copies to.
space::BumpPointerSpace* temp_space_;
space::RegionSpace* region_space_;
// Minimum free guarantees that you always have at least min_free_ free bytes after growing for
// utilization, regardless of target utilization ratio.
size_t min_free_;
// The ideal maximum free size, when we grow the heap for utilization.
size_t max_free_;
// Target ideal heap utilization ratio
double target_utilization_;
// How much more we grow the heap when we are a foreground app instead of background.
double foreground_heap_growth_multiplier_;
// Total time which mutators are paused or waiting for GC to complete.
uint64_t total_wait_time_;
// Total number of objects allocated in microseconds.
AtomicInteger total_allocation_time_;
// The current state of heap verification, may be enabled or disabled.
VerifyObjectMode verify_object_mode_;
// Compacting GC disable count, prevents compacting GC from running iff > 0.
size_t disable_moving_gc_count_ GUARDED_BY(gc_complete_lock_);
std::vector<collector::GarbageCollector*> garbage_collectors_;
collector::SemiSpace* semi_space_collector_;
collector::MarkCompact* mark_compact_collector_;
collector::ConcurrentCopying* concurrent_copying_collector_;
const bool running_on_valgrind_;
const bool use_tlab_;
// Pointer to the space which becomes the new main space when we do homogeneous space compaction.
// Use unique_ptr since the space is only added during the homogeneous compaction phase.
std::unique_ptr<space::MallocSpace> main_space_backup_;
// Minimal interval allowed between two homogeneous space compactions caused by OOM.
uint64_t min_interval_homogeneous_space_compaction_by_oom_;
// Times of the last homogeneous space compaction caused by OOM.
uint64_t last_time_homogeneous_space_compaction_by_oom_;
// Saved OOMs by homogeneous space compaction.
Atomic<size_t> count_delayed_oom_;
// Count for requested homogeneous space compaction.
Atomic<size_t> count_requested_homogeneous_space_compaction_;
// Count for ignored homogeneous space compaction.
Atomic<size_t> count_ignored_homogeneous_space_compaction_;
// Count for performed homogeneous space compaction.
Atomic<size_t> count_performed_homogeneous_space_compaction_;
// Whether or not a concurrent GC is pending.
Atomic<bool> concurrent_gc_pending_;
// Active tasks which we can modify (change target time, desired collector type, etc..).
CollectorTransitionTask* pending_collector_transition_ GUARDED_BY(pending_task_lock_);
HeapTrimTask* pending_heap_trim_ GUARDED_BY(pending_task_lock_);
// Whether or not we use homogeneous space compaction to avoid OOM errors.
bool use_homogeneous_space_compaction_for_oom_;
// True if the currently running collection has made some thread wait.
bool running_collection_is_blocking_ GUARDED_BY(gc_complete_lock_);
// The number of blocking GC runs.
uint64_t blocking_gc_count_;
// The total duration of blocking GC runs.
uint64_t blocking_gc_time_;
// The duration of the window for the GC count rate histograms.
static constexpr uint64_t kGcCountRateHistogramWindowDuration = MsToNs(10 * 1000); // 10s.
// The last time when the GC count rate histograms were updated.
// This is rounded by kGcCountRateHistogramWindowDuration (a multiple of 10s).
uint64_t last_update_time_gc_count_rate_histograms_;
// The running count of GC runs in the last window.
uint64_t gc_count_last_window_;
// The running count of blocking GC runs in the last window.
uint64_t blocking_gc_count_last_window_;
// The maximum number of buckets in the GC count rate histograms.
static constexpr size_t kGcCountRateMaxBucketCount = 200;
// The histogram of the number of GC invocations per window duration.
Histogram<uint64_t> gc_count_rate_histogram_ GUARDED_BY(gc_complete_lock_);
// The histogram of the number of blocking GC invocations per window duration.
Histogram<uint64_t> blocking_gc_count_rate_histogram_ GUARDED_BY(gc_complete_lock_);
friend class CollectorTransitionTask;
friend class collector::GarbageCollector;
friend class collector::MarkCompact;
friend class collector::ConcurrentCopying;
friend class collector::MarkSweep;
friend class collector::SemiSpace;
friend class ReferenceQueue;
friend class VerifyReferenceCardVisitor;
friend class VerifyReferenceVisitor;
friend class VerifyObjectVisitor;
friend class ScopedHeapFill;
friend class ScopedHeapLock;
friend class space::SpaceTest;
class AllocationTimer {
Heap* heap_;
mirror::Object** allocated_obj_ptr_;
uint64_t allocation_start_time_;
AllocationTimer(Heap* heap, mirror::Object** allocated_obj_ptr);
// ScopedHeapFill changes the bytes allocated counter to be equal to the growth limit. This
// causes the next allocation to perform a GC and possibly an OOM. It can be used to ensure that a
// GC happens in specific methods such as ThrowIllegalMonitorStateExceptionF in Monitor::Wait.
class ScopedHeapFill {
explicit ScopedHeapFill(Heap* heap)
: heap_(heap),
delta_(heap_->GetMaxMemory() - heap_->GetBytesAllocated()) {
~ScopedHeapFill() {
Heap* const heap_;
const int64_t delta_;
} // namespace gc
} // namespace art