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* Copyright (C) 2012 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 <stdint.h>
#include <vector>
#include "base/histogram.h"
#include "base/mutex.h"
#include "base/timing_logger.h"
#include "gc/collector_type.h"
#include "gc/gc_cause.h"
#include "gc_root.h"
#include "gc_type.h"
#include "object_callbacks.h"
namespace art {
namespace mirror {
class Class;
class Object;
class Reference;
} // namespace mirror
namespace gc {
class Heap;
namespace collector {
struct ObjectBytePair {
ObjectBytePair(uint64_t num_objects = 0, int64_t num_bytes = 0)
: objects(num_objects), bytes(num_bytes) {}
void Add(const ObjectBytePair& other) {
objects += other.objects;
bytes += other.bytes;
// Number of objects which were freed.
uint64_t objects;
// Freed bytes are signed since the GC can free negative bytes if it promotes objects to a space
// which has a larger allocation size.
int64_t bytes;
// A information related single garbage collector iteration. Since we only ever have one GC running
// at any given time, we can have a single iteration info.
class Iteration {
// Returns how long the mutators were paused in nanoseconds.
const std::vector<uint64_t>& GetPauseTimes() const {
return pause_times_;
TimingLogger* GetTimings() {
return &timings_;
// Returns how long the GC took to complete in nanoseconds.
uint64_t GetDurationNs() const {
return duration_ns_;
int64_t GetFreedBytes() const {
return freed_.bytes;
int64_t GetFreedLargeObjectBytes() const {
return freed_los_.bytes;
uint64_t GetFreedObjects() const {
return freed_.objects;
uint64_t GetFreedLargeObjects() const {
return freed_los_.objects;
uint64_t GetFreedRevokeBytes() const {
return freed_bytes_revoke_;
void SetFreedRevoke(uint64_t freed) {
freed_bytes_revoke_ = freed;
void Reset(GcCause gc_cause, bool clear_soft_references);
// Returns the estimated throughput of the iteration.
uint64_t GetEstimatedThroughput() const;
bool GetClearSoftReferences() const {
return clear_soft_references_;
void SetClearSoftReferences(bool clear_soft_references) {
clear_soft_references_ = clear_soft_references;
GcCause GetGcCause() const {
return gc_cause_;
void SetDurationNs(uint64_t duration) {
duration_ns_ = duration;
GcCause gc_cause_;
bool clear_soft_references_;
uint64_t duration_ns_;
TimingLogger timings_;
ObjectBytePair freed_;
ObjectBytePair freed_los_;
uint64_t freed_bytes_revoke_; // see Heap::num_bytes_freed_revoke_.
std::vector<uint64_t> pause_times_;
friend class GarbageCollector;
class GarbageCollector : public RootVisitor, public IsMarkedVisitor, public MarkObjectVisitor {
class SCOPED_LOCKABLE ScopedPause {
explicit ScopedPause(GarbageCollector* collector) EXCLUSIVE_LOCK_FUNCTION(Locks::mutator_lock_);
~ScopedPause() UNLOCK_FUNCTION();
const uint64_t start_time_;
GarbageCollector* const collector_;
GarbageCollector(Heap* heap, const std::string& name);
virtual ~GarbageCollector() { }
const char* GetName() const {
return name_.c_str();
virtual GcType GetGcType() const = 0;
virtual CollectorType GetCollectorType() const = 0;
// Run the garbage collector.
void Run(GcCause gc_cause, bool clear_soft_references) REQUIRES(!pause_histogram_lock_);
Heap* GetHeap() const {
return heap_;
void RegisterPause(uint64_t nano_length);
const CumulativeLogger& GetCumulativeTimings() const {
return cumulative_timings_;
void ResetCumulativeStatistics() REQUIRES(!pause_histogram_lock_);
// Swap the live and mark bitmaps of spaces that are active for the collector. For partial GC,
// this is the allocation space, for full GC then we swap the zygote bitmaps too.
void SwapBitmaps()
uint64_t GetTotalPausedTimeNs() REQUIRES(!pause_histogram_lock_);
int64_t GetTotalFreedBytes() const {
return total_freed_bytes_;
uint64_t GetTotalFreedObjects() const {
return total_freed_objects_;
// Reset the cumulative timings and pause histogram.
void ResetMeasurements() REQUIRES(!pause_histogram_lock_);
// Returns the estimated throughput in bytes / second.
uint64_t GetEstimatedMeanThroughput() const;
// Returns how many GC iterations have been run.
size_t NumberOfIterations() const {
return GetCumulativeTimings().GetIterations();
// Returns the current GC iteration and assocated info.
Iteration* GetCurrentIteration();
const Iteration* GetCurrentIteration() const;
TimingLogger* GetTimings() {
return &GetCurrentIteration()->timings_;
// Record a free of normal objects.
void RecordFree(const ObjectBytePair& freed);
// Record a free of large objects.
void RecordFreeLOS(const ObjectBytePair& freed);
void DumpPerformanceInfo(std::ostream& os) REQUIRES(!pause_histogram_lock_);
// Helper functions for querying if objects are marked. These are used for processing references,
// and will be used for reading system weaks while the GC is running.
virtual mirror::Object* IsMarked(mirror::Object* obj)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
virtual bool IsMarkedHeapReference(mirror::HeapReference<mirror::Object>* obj)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
// Used by reference processor.
virtual void ProcessMarkStack() SHARED_REQUIRES(Locks::mutator_lock_) = 0;
// Force mark an object.
virtual mirror::Object* MarkObject(mirror::Object* obj)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
virtual void MarkHeapReference(mirror::HeapReference<mirror::Object>* obj)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
virtual void DelayReferenceReferent(mirror::Class* klass, mirror::Reference* reference)
SHARED_REQUIRES(Locks::mutator_lock_) = 0;
// Run all of the GC phases.
virtual void RunPhases() = 0;
// Revoke all the thread-local buffers.
virtual void RevokeAllThreadLocalBuffers() = 0;
static constexpr size_t kPauseBucketSize = 500;
static constexpr size_t kPauseBucketCount = 32;
Heap* const heap_;
std::string name_;
// Cumulative statistics.
Histogram<uint64_t> pause_histogram_ GUARDED_BY(pause_histogram_lock_);
uint64_t total_time_ns_;
uint64_t total_freed_objects_;
int64_t total_freed_bytes_;
CumulativeLogger cumulative_timings_;
mutable Mutex pause_histogram_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
} // namespace collector
} // namespace gc
} // namespace art