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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.
#ifndef ART_SRC_HEAP_H_
#define ART_SRC_HEAP_H_
#include <iosfwd>
#include <string>
#include <vector>
#include "atomic_integer.h"
#include "gc/atomic_stack.h"
#include "gc/card_table.h"
#include "gc/heap_bitmap.h"
#include "globals.h"
#include "gtest/gtest.h"
#include "locks.h"
#include "offsets.h"
#include "safe_map.h"
#include "timing_logger.h"
// Fast verification means we do not verify the classes of objects.
namespace art {
class AllocSpace;
class Class;
class ConditionVariable;
class DlMallocSpace;
class HeapBitmap;
class ImageSpace;
class LargeObjectSpace;
class MarkSweep;
class ModUnionTable;
class Mutex;
class Object;
class Space;
class SpaceTest;
class Thread;
class TimingLogger;
typedef AtomicStack<Object*> ObjectStack;
typedef std::vector<ContinuousSpace*> Spaces;
// The ordering of the enum matters, it is used to determine which GCs are run first.
enum GcType {
// No Gc
// Sticky mark bits "generational" GC.
// Partial GC, over only the alloc space.
// Full GC
// Number of different Gc types.
std::ostream& operator<<(std::ostream& os, const GcType& policy);
enum GcCause {
std::ostream& operator<<(std::ostream& os, const GcCause& policy);
class Heap {
static const size_t kDefaultInitialSize = 2 * MB;
static const size_t kDefaultMaximumSize = 32 * MB;
static const size_t kDefaultMaxFree = 2 * MB;
static const size_t kDefaultMinFree = kDefaultMaxFree / 4;
// Default target utilization.
static const double kDefaultTargetUtilization;
// Used so that we don't overflow the allocation time atomic integer.
static const size_t kTimeAdjust = 1024;
typedef void (RootVisitor)(const Object* root, void* arg);
typedef void (VerifyRootVisitor)(const Object* root, void* arg, size_t vreg,
const AbstractMethod* method);
typedef bool (IsMarkedTester)(const Object* object, void* arg);
// 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, size_t capacity,
const std::string& original_image_file_name, bool concurrent_gc);
// Allocates and initializes storage for an object instance.
Object* AllocObject(Thread* self, Class* klass, size_t num_bytes)
// Check sanity of given reference. Requires the heap lock.
void VerifyObject(const Object* o);
void VerifyObject(const Object*) {}
// Check sanity of all live references. Requires the heap lock.
void VerifyHeap() LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
static void RootMatchesObjectVisitor(const Object* root, void* arg);
bool VerifyHeapReferences()
bool VerifyMissingCardMarks()
// 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 IsHeapAddress(const Object* obj);
// Returns true if 'obj' is a live heap object, false otherwise (including for invalid addresses).
// Requires the heap lock to be held.
bool IsLiveObjectLocked(const Object* obj)
// 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 java.lang.Runtime.maxMemory.
int64_t GetMaxMemory() const;
// Implements java.lang.Runtime.totalMemory.
int64_t GetTotalMemory() const;
// Implements java.lang.Runtime.freeMemory.
int64_t GetFreeMemory() const;
// Implements VMDebug.countInstancesOfClass.
int64_t CountInstances(Class* c, bool count_assignable)
// 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();
// Target ideal heap utilization ratio, implements
// dalvik.system.VMRuntime.getTargetHeapUtilization.
double GetTargetHeapUtilization() const {
return target_utilization_;
// 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
// true if we waited for the GC to complete.
GcType WaitForConcurrentGcToComplete(Thread* self) LOCKS_EXCLUDED(gc_complete_lock_);
const Spaces& GetSpaces() {
return spaces_;
void SetReferenceOffsets(MemberOffset reference_referent_offset,
MemberOffset reference_queue_offset,
MemberOffset reference_queueNext_offset,
MemberOffset reference_pendingNext_offset,
MemberOffset finalizer_reference_zombie_offset);
Object* GetReferenceReferent(Object* reference);
void ClearReferenceReferent(Object* reference) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
// Returns true if the reference object has not yet been enqueued.
bool IsEnqueuable(const Object* ref);
void EnqueueReference(Object* ref, Object** list) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
void EnqueuePendingReference(Object* ref, Object** list)
Object* DequeuePendingReference(Object** list) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
MemberOffset GetReferencePendingNextOffset() {
DCHECK_NE(reference_pendingNext_offset_.Uint32Value(), 0U);
return reference_pendingNext_offset_;
MemberOffset GetFinalizerReferenceZombieOffset() {
DCHECK_NE(finalizer_reference_zombie_offset_.Uint32Value(), 0U);
return finalizer_reference_zombie_offset_;
void EnableObjectValidation() {
verify_objects_ = true;
void DisableObjectValidation() {
verify_objects_ = false;
bool IsObjectValidationEnabled() const {
return verify_objects_;
void RecordFree(size_t freed_objects, size_t freed_bytes);
// 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.
void WriteBarrierField(const Object* dst, MemberOffset /*offset*/, const Object* /*new_value*/) {
if (!card_marking_disabled_) {
// Write barrier for array operations that update many field positions
void WriteBarrierArray(const Object* dst, int /*start_offset*/,
size_t /*length TODO: element_count or byte_count?*/) {
if (UNLIKELY(!card_marking_disabled_)) {
CardTable* GetCardTable() {
return card_table_.get();
void DisableCardMarking() {
// TODO: we shouldn't need to disable card marking, this is here to help the image_writer
card_marking_disabled_ = true;
void AddFinalizerReference(Thread* self, Object* object);
size_t GetBytesAllocated() const;
size_t GetObjectsAllocated() const;
size_t GetConcurrentStartSize() const;
size_t GetConcurrentMinFree() const;
size_t GetUsedMemorySize() const;
// Returns the total number of objects allocated since the heap was created.
size_t GetTotalObjectsAllocated() const;
// Returns the total number of bytes allocated since the heap was created.
size_t GetTotalBytesAllocated() const;
// Returns the total number of objects freed since the heap was created.
size_t GetTotalObjectsFreed() const;
// Returns the total number of bytes freed since the heap was created.
size_t GetTotalBytesFreed() const;
// Functions for getting the bitmap which corresponds to an object's address.
// This is probably slow, TODO: use better data structure like binary tree .
ContinuousSpace* FindSpaceFromObject(const Object*) const;
void DumpForSigQuit(std::ostream& os);
void Trim();
HeapBitmap* GetLiveBitmap() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
return live_bitmap_.get();
HeapBitmap* GetMarkBitmap() SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
return mark_bitmap_.get();
void PreZygoteFork() LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// Mark and empty stack.
void FlushAllocStack()
// Mark all the objects in the allocation stack in the specified bitmap.
void MarkAllocStack(SpaceBitmap* bitmap, SpaceSetMap* large_objects, ObjectStack* stack)
// Unmark all the objects in the allocation stack in the specified bitmap.
void UnMarkAllocStack(SpaceBitmap* bitmap, SpaceSetMap* large_objects, ObjectStack* stack)
// Update and mark mod union table based on gc type.
void UpdateAndMarkModUnion(MarkSweep* mark_sweep, TimingLogger& timings, GcType gc_type)
// DEPRECATED: Should remove in "near" future when support for multiple image spaces is added.
// Assumes there is only one image space.
ImageSpace* GetImageSpace();
DlMallocSpace* GetAllocSpace();
LargeObjectSpace* GetLargeObjectsSpace() {
return large_object_space_.get();
void DumpSpaces();
// UnReserve the address range where the oat file will be placed.
void UnReserveOatFileAddressRange();
// GC performance measuring
void DumpGcPerformanceInfo();
// Allocates uninitialized storage. Passing in a null space tries to place the object in the
// large object space.
Object* Allocate(Thread* self, AllocSpace* space, size_t num_bytes)
// Try to allocate a number of bytes, this function never does any GCs.
Object* TryToAllocate(Thread* self, AllocSpace* space, size_t alloc_size, bool grow)
// Pushes a list of cleared references out to the managed heap.
void EnqueueClearedReferences(Object** cleared_references);
void RequestHeapTrim() LOCKS_EXCLUDED(Locks::runtime_shutdown_lock_);
void RequestConcurrentGC(Thread* self) LOCKS_EXCLUDED(Locks::runtime_shutdown_lock_);
// Swap bitmaps (if we are a full Gc then we swap the zygote bitmap too).
void SwapBitmaps(GcType gc_type) EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
void SwapLargeObjects() EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_);
void RecordAllocation(size_t size, Object* object)
// Sometimes CollectGarbageInternal decides to run a different Gc than you requested. Returns
// which type of Gc was actually ran.
GcType CollectGarbageInternal(GcType gc_plan, GcCause gc_cause, bool clear_soft_references)
void CollectGarbageMarkSweepPlan(Thread* self, GcType gc_plan, GcCause gc_cause,
bool clear_soft_references)
void CollectGarbageConcurrentMarkSweepPlan(Thread* self, GcType gc_plan, GcCause gc_cause,
bool clear_soft_references)
// 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.
void GrowForUtilization();
size_t GetPercentFree();
void AddSpace(ContinuousSpace* space) LOCKS_EXCLUDED(Locks::heap_bitmap_lock_);
// No thread saftey analysis since we call this everywhere and it is impossible to find a proper
// lock ordering for it.
void VerifyObjectBody(const Object *obj) NO_THREAD_SAFETY_ANALYSIS;
static void VerificationCallback(Object* obj, void* arg)
// Swap the allocation stack with the live stack.
void SwapStacks();
// Clear cards and update the mod union table.
void ClearCards(TimingLogger& timings);
Spaces spaces_;
// A map that we use to temporarily reserve address range for the oat file.
UniquePtr<MemMap> oat_file_map_;
// The alloc space which we are currently allocating into.
DlMallocSpace* alloc_space_;
// One cumulative logger for each type of Gc.
typedef SafeMap<GcType, CumulativeLogger*> CumulativeTimings;
CumulativeTimings cumulative_timings_;
// The mod-union table remembers all of the references from the image space to the alloc /
// zygote spaces.
UniquePtr<ModUnionTable> mod_union_table_;
// This table holds all of the references from the zygote space to the alloc space.
UniquePtr<ModUnionTable> zygote_mod_union_table_;
UniquePtr<CardTable> card_table_;
// True for concurrent mark sweep GC, false for mark sweep.
const bool concurrent_gc_;
// If we have a zygote space.
bool have_zygote_space_;
// Used by the image writer to disable card marking on copied objects
// TODO: remove
bool card_marking_disabled_;
// 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;
UniquePtr<ConditionVariable> gc_complete_cond_ GUARDED_BY(gc_complete_lock_);
// True while the garbage collector is running.
volatile bool is_gc_running_ GUARDED_BY(gc_complete_lock_);
// Last Gc type we ran. Used by WaitForConcurrentGc to know which Gc was waited on.
volatile GcType last_gc_type_ GUARDED_BY(gc_complete_lock_);
// If enabled, causes Gc for alloc when heap size reaches the current footprint limit before the
// Gc updates it.
const bool enforce_heap_growth_rate_;
// Maximum size that the heap can reach.
size_t growth_limit_;
size_t max_allowed_footprint_;
// Bytes until concurrent GC starts.
size_t concurrent_start_size_;
size_t concurrent_min_free_;
size_t concurrent_start_bytes_;
// Number of bytes allocated since the last Gc, we use this to help determine when to schedule concurrent GCs.
size_t bytes_since_last_gc_;
size_t sticky_gc_count_;
size_t total_bytes_freed_;
size_t total_objects_freed_;
// Primitive objects larger than this size are put in the large object space.
size_t large_object_threshold_;
// Large object space.
UniquePtr<LargeObjectSpace> large_object_space_;
// Number of bytes allocated. Adjusted after each allocation and free.
AtomicInteger num_bytes_allocated_;
// Heap verification flags.
const bool verify_missing_card_marks_;
const bool verify_system_weaks_;
const bool verify_pre_gc_heap_;
const bool verify_post_gc_heap_;
const bool verify_mod_union_table_;
// After how many GCs we force to do a partial GC instead of sticky mark bits GC.
const size_t partial_gc_frequency_;
// Sticky mark bits GC has some overhead, so if we have less a few megabytes of AllocSpace then
// it's probably better to just do a partial GC.
const size_t min_alloc_space_size_for_sticky_gc_;
// Minimum remaining size for sticky GC. Since sticky GC doesn't free up as much memory as a
// normal GC, it is important to not use it when we are almost out of memory.
const size_t min_remaining_space_for_sticky_gc_;
// Last trim time
uint64_t last_trim_time_;
UniquePtr<HeapBitmap> live_bitmap_ GUARDED_BY(Locks::heap_bitmap_lock_);
UniquePtr<HeapBitmap> mark_bitmap_ GUARDED_BY(Locks::heap_bitmap_lock_);
// Used to ensure that we don't ever recursively request GC.
volatile bool requesting_gc_;
// Mark stack that we reuse to avoid re-allocating the mark stack.
UniquePtr<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_;
UniquePtr<ObjectStack> allocation_stack_;
// Second allocation stack so that we can process allocation with the heap unlocked.
UniquePtr<ObjectStack> live_stack_;
// offset of java.lang.ref.Reference.referent
MemberOffset reference_referent_offset_;
// offset of java.lang.ref.Reference.queue
MemberOffset reference_queue_offset_;
// offset of java.lang.ref.Reference.queueNext
MemberOffset reference_queueNext_offset_;
// offset of java.lang.ref.Reference.pendingNext
MemberOffset reference_pendingNext_offset_;
// offset of java.lang.ref.FinalizerReference.zombie
MemberOffset finalizer_reference_zombie_offset_;
// 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_;
// Total time which mutators are paused or waiting for GC to complete.
uint64_t total_paused_time_;
uint64_t total_wait_time_;
// Total number of objects allocated in microseconds.
const bool measure_allocation_time_;
AtomicInteger total_allocation_time_;
bool verify_objects_;
friend class MarkSweep;
friend class VerifyReferenceCardVisitor;
friend class VerifyReferenceVisitor;
friend class VerifyObjectVisitor;
friend class ScopedHeapLock;
FRIEND_TEST(SpaceTest, AllocAndFree);
FRIEND_TEST(SpaceTest, AllocAndFreeList);
FRIEND_TEST(SpaceTest, ZygoteSpace);
friend class SpaceTest;
} // namespace art
#endif // ART_SRC_HEAP_H_