concurrent_copying.cc revision 65b798ea10dd716c1bb3dda029f9bf255435af72 
1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "concurrent_copying.h"
18
19#include "gc/accounting/heap_bitmap-inl.h"
20#include "gc/accounting/space_bitmap-inl.h"
21#include "gc/space/image_space.h"
22#include "gc/space/space.h"
23#include "intern_table.h"
24#include "mirror/art_field-inl.h"
25#include "mirror/object-inl.h"
26#include "scoped_thread_state_change.h"
27#include "thread-inl.h"
28#include "thread_list.h"
29#include "well_known_classes.h"
30
31namespace art {
32namespace gc {
33namespace collector {
34
35ConcurrentCopying::ConcurrentCopying(Heap* heap, const std::string& name_prefix)
36    : GarbageCollector(heap,
37                       name_prefix + (name_prefix.empty() ? "" : " ") +
38                       "concurrent copying + mark sweep"),
39      region_space_(nullptr), gc_barrier_(new Barrier(0)), mark_queue_(2 * MB),
40      is_marking_(false), is_active_(false), is_asserting_to_space_invariant_(false),
41      heap_mark_bitmap_(nullptr), live_stack_freeze_size_(0),
42      skipped_blocks_lock_("concurrent copying bytes blocks lock", kMarkSweepMarkStackLock),
43      rb_table_(heap_->GetReadBarrierTable()),
44      force_evacuate_all_(false) {
45  static_assert(space::RegionSpace::kRegionSize == accounting::ReadBarrierTable::kRegionSize,
46                "The region space size and the read barrier table region size must match");
47  cc_heap_bitmap_.reset(new accounting::HeapBitmap(heap));
48  {
49    Thread* self = Thread::Current();
50    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
51    // Cache this so that we won't have to lock heap_bitmap_lock_ in
52    // Mark() which could cause a nested lock on heap_bitmap_lock_
53    // when GC causes a RB while doing GC or a lock order violation
54    // (class_linker_lock_ and heap_bitmap_lock_).
55    heap_mark_bitmap_ = heap->GetMarkBitmap();
56  }
57}
58
59ConcurrentCopying::~ConcurrentCopying() {
60}
61
62void ConcurrentCopying::RunPhases() {
63  CHECK(kUseBakerReadBarrier || kUseTableLookupReadBarrier);
64  CHECK(!is_active_);
65  is_active_ = true;
66  Thread* self = Thread::Current();
67  Locks::mutator_lock_->AssertNotHeld(self);
68  {
69    ReaderMutexLock mu(self, *Locks::mutator_lock_);
70    InitializePhase();
71  }
72  FlipThreadRoots();
73  {
74    ReaderMutexLock mu(self, *Locks::mutator_lock_);
75    MarkingPhase();
76  }
77  // Verify no from space refs. This causes a pause.
78  if (kEnableNoFromSpaceRefsVerification || kIsDebugBuild) {
79    TimingLogger::ScopedTiming split("(Paused)VerifyNoFromSpaceReferences", GetTimings());
80    ScopedPause pause(this);
81    CheckEmptyMarkQueue();
82    if (kVerboseMode) {
83      LOG(INFO) << "Verifying no from-space refs";
84    }
85    VerifyNoFromSpaceReferences();
86    CheckEmptyMarkQueue();
87  }
88  {
89    ReaderMutexLock mu(self, *Locks::mutator_lock_);
90    ReclaimPhase();
91  }
92  FinishPhase();
93  CHECK(is_active_);
94  is_active_ = false;
95}
96
97void ConcurrentCopying::BindBitmaps() {
98  Thread* self = Thread::Current();
99  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
100  // Mark all of the spaces we never collect as immune.
101  for (const auto& space : heap_->GetContinuousSpaces()) {
102    if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect
103        || space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect) {
104      CHECK(space->IsZygoteSpace() || space->IsImageSpace());
105      CHECK(immune_region_.AddContinuousSpace(space)) << "Failed to add space " << *space;
106      const char* bitmap_name = space->IsImageSpace() ? "cc image space bitmap" :
107          "cc zygote space bitmap";
108      // TODO: try avoiding using bitmaps for image/zygote to save space.
109      accounting::ContinuousSpaceBitmap* bitmap =
110          accounting::ContinuousSpaceBitmap::Create(bitmap_name, space->Begin(), space->Capacity());
111      cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
112      cc_bitmaps_.push_back(bitmap);
113    } else if (space == region_space_) {
114      accounting::ContinuousSpaceBitmap* bitmap =
115          accounting::ContinuousSpaceBitmap::Create("cc region space bitmap",
116                                                    space->Begin(), space->Capacity());
117      cc_heap_bitmap_->AddContinuousSpaceBitmap(bitmap);
118      cc_bitmaps_.push_back(bitmap);
119      region_space_bitmap_ = bitmap;
120    }
121  }
122}
123
124void ConcurrentCopying::InitializePhase() {
125  TimingLogger::ScopedTiming split("InitializePhase", GetTimings());
126  if (kVerboseMode) {
127    LOG(INFO) << "GC InitializePhase";
128    LOG(INFO) << "Region-space : " << reinterpret_cast<void*>(region_space_->Begin()) << "-"
129              << reinterpret_cast<void*>(region_space_->Limit());
130  }
131  CHECK(mark_queue_.IsEmpty());
132  immune_region_.Reset();
133  bytes_moved_.StoreRelaxed(0);
134  objects_moved_.StoreRelaxed(0);
135  if (GetCurrentIteration()->GetGcCause() == kGcCauseExplicit ||
136      GetCurrentIteration()->GetGcCause() == kGcCauseForNativeAlloc ||
137      GetCurrentIteration()->GetClearSoftReferences()) {
138    force_evacuate_all_ = true;
139  } else {
140    force_evacuate_all_ = false;
141  }
142  BindBitmaps();
143  if (kVerboseMode) {
144    LOG(INFO) << "force_evacuate_all=" << force_evacuate_all_;
145    LOG(INFO) << "Immune region: " << immune_region_.Begin() << "-" << immune_region_.End();
146    LOG(INFO) << "GC end of InitializePhase";
147  }
148}
149
150// Used to switch the thread roots of a thread from from-space refs to to-space refs.
151class ThreadFlipVisitor : public Closure {
152 public:
153  explicit ThreadFlipVisitor(ConcurrentCopying* concurrent_copying, bool use_tlab)
154      : concurrent_copying_(concurrent_copying), use_tlab_(use_tlab) {
155  }
156
157  virtual void Run(Thread* thread) OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
158    // Note: self is not necessarily equal to thread since thread may be suspended.
159    Thread* self = Thread::Current();
160    CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
161        << thread->GetState() << " thread " << thread << " self " << self;
162    if (use_tlab_ && thread->HasTlab()) {
163      if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
164        // This must come before the revoke.
165        size_t thread_local_objects = thread->GetThreadLocalObjectsAllocated();
166        concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
167        reinterpret_cast<Atomic<size_t>*>(&concurrent_copying_->from_space_num_objects_at_first_pause_)->
168            FetchAndAddSequentiallyConsistent(thread_local_objects);
169      } else {
170        concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread);
171      }
172    }
173    if (kUseThreadLocalAllocationStack) {
174      thread->RevokeThreadLocalAllocationStack();
175    }
176    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
177    thread->VisitRoots(concurrent_copying_);
178    concurrent_copying_->GetBarrier().Pass(self);
179  }
180
181 private:
182  ConcurrentCopying* const concurrent_copying_;
183  const bool use_tlab_;
184};
185
186// Called back from Runtime::FlipThreadRoots() during a pause.
187class FlipCallback : public Closure {
188 public:
189  explicit FlipCallback(ConcurrentCopying* concurrent_copying)
190      : concurrent_copying_(concurrent_copying) {
191  }
192
193  virtual void Run(Thread* thread) OVERRIDE EXCLUSIVE_LOCKS_REQUIRED(Locks::mutator_lock_) {
194    ConcurrentCopying* cc = concurrent_copying_;
195    TimingLogger::ScopedTiming split("(Paused)FlipCallback", cc->GetTimings());
196    // Note: self is not necessarily equal to thread since thread may be suspended.
197    Thread* self = Thread::Current();
198    CHECK(thread == self);
199    Locks::mutator_lock_->AssertExclusiveHeld(self);
200    cc->region_space_->SetFromSpace(cc->rb_table_, cc->force_evacuate_all_);
201    cc->SwapStacks(self);
202    if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) {
203      cc->RecordLiveStackFreezeSize(self);
204      cc->from_space_num_objects_at_first_pause_ = cc->region_space_->GetObjectsAllocated();
205      cc->from_space_num_bytes_at_first_pause_ = cc->region_space_->GetBytesAllocated();
206    }
207    cc->is_marking_ = true;
208    if (UNLIKELY(Runtime::Current()->IsActiveTransaction())) {
209      CHECK(Runtime::Current()->IsAotCompiler());
210      TimingLogger::ScopedTiming split2("(Paused)VisitTransactionRoots", cc->GetTimings());
211      Runtime::Current()->VisitTransactionRoots(cc);
212    }
213  }
214
215 private:
216  ConcurrentCopying* const concurrent_copying_;
217};
218
219// Switch threads that from from-space to to-space refs. Forward/mark the thread roots.
220void ConcurrentCopying::FlipThreadRoots() {
221  TimingLogger::ScopedTiming split("FlipThreadRoots", GetTimings());
222  if (kVerboseMode) {
223    LOG(INFO) << "time=" << region_space_->Time();
224    region_space_->DumpNonFreeRegions(LOG(INFO));
225  }
226  Thread* self = Thread::Current();
227  Locks::mutator_lock_->AssertNotHeld(self);
228  gc_barrier_->Init(self, 0);
229  ThreadFlipVisitor thread_flip_visitor(this, heap_->use_tlab_);
230  FlipCallback flip_callback(this);
231  size_t barrier_count = Runtime::Current()->FlipThreadRoots(
232      &thread_flip_visitor, &flip_callback, this);
233  {
234    ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
235    gc_barrier_->Increment(self, barrier_count);
236  }
237  is_asserting_to_space_invariant_ = true;
238  QuasiAtomic::ThreadFenceForConstructor();
239  if (kVerboseMode) {
240    LOG(INFO) << "time=" << region_space_->Time();
241    region_space_->DumpNonFreeRegions(LOG(INFO));
242    LOG(INFO) << "GC end of FlipThreadRoots";
243  }
244}
245
246void ConcurrentCopying::SwapStacks(Thread* self) {
247  heap_->SwapStacks(self);
248}
249
250void ConcurrentCopying::RecordLiveStackFreezeSize(Thread* self) {
251  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
252  live_stack_freeze_size_ = heap_->GetLiveStack()->Size();
253}
254
255// Used to visit objects in the immune spaces.
256class ConcurrentCopyingImmuneSpaceObjVisitor {
257 public:
258  explicit ConcurrentCopyingImmuneSpaceObjVisitor(ConcurrentCopying* cc)
259      : collector_(cc) {}
260
261  void operator()(mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
262      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
263    DCHECK(obj != nullptr);
264    DCHECK(collector_->immune_region_.ContainsObject(obj));
265    accounting::ContinuousSpaceBitmap* cc_bitmap =
266        collector_->cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
267    DCHECK(cc_bitmap != nullptr)
268        << "An immune space object must have a bitmap";
269    if (kIsDebugBuild) {
270      DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj))
271          << "Immune space object must be already marked";
272    }
273    // This may or may not succeed, which is ok.
274    if (kUseBakerReadBarrier) {
275      obj->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
276    }
277    if (cc_bitmap->AtomicTestAndSet(obj)) {
278      // Already marked. Do nothing.
279    } else {
280      // Newly marked. Set the gray bit and push it onto the mark stack.
281      CHECK(!kUseBakerReadBarrier || obj->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
282      collector_->PushOntoMarkStack<true>(obj);
283    }
284  }
285
286 private:
287  ConcurrentCopying* collector_;
288};
289
290class EmptyCheckpoint : public Closure {
291 public:
292  explicit EmptyCheckpoint(ConcurrentCopying* concurrent_copying)
293      : concurrent_copying_(concurrent_copying) {
294  }
295
296  virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
297    // Note: self is not necessarily equal to thread since thread may be suspended.
298    Thread* self = Thread::Current();
299    CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc)
300        << thread->GetState() << " thread " << thread << " self " << self;
301    // If thread is a running mutator, then act on behalf of the garbage collector.
302    // See the code in ThreadList::RunCheckpoint.
303    if (thread->GetState() == kRunnable) {
304      concurrent_copying_->GetBarrier().Pass(self);
305    }
306  }
307
308 private:
309  ConcurrentCopying* const concurrent_copying_;
310};
311
312// Concurrently mark roots that are guarded by read barriers and process the mark stack.
313void ConcurrentCopying::MarkingPhase() {
314  TimingLogger::ScopedTiming split("MarkingPhase", GetTimings());
315  if (kVerboseMode) {
316    LOG(INFO) << "GC MarkingPhase";
317  }
318  {
319    // Mark the image root. The WB-based collectors do not need to
320    // scan the image objects from roots by relying on the card table,
321    // but it's necessary for the RB to-space invariant to hold.
322    TimingLogger::ScopedTiming split1("VisitImageRoots", GetTimings());
323    gc::space::ImageSpace* image = heap_->GetImageSpace();
324    if (image != nullptr) {
325      mirror::ObjectArray<mirror::Object>* image_root = image->GetImageHeader().GetImageRoots();
326      mirror::Object* marked_image_root = Mark(image_root);
327      CHECK_EQ(image_root, marked_image_root) << "An image object does not move";
328      if (ReadBarrier::kEnableToSpaceInvariantChecks) {
329        AssertToSpaceInvariant(nullptr, MemberOffset(0), marked_image_root);
330      }
331    }
332  }
333  {
334    TimingLogger::ScopedTiming split2("VisitConstantRoots", GetTimings());
335    Runtime::Current()->VisitConstantRoots(this);
336  }
337  {
338    TimingLogger::ScopedTiming split3("VisitInternTableRoots", GetTimings());
339    Runtime::Current()->GetInternTable()->VisitRoots(this, kVisitRootFlagAllRoots);
340  }
341  {
342    TimingLogger::ScopedTiming split4("VisitClassLinkerRoots", GetTimings());
343    Runtime::Current()->GetClassLinker()->VisitRoots(this, kVisitRootFlagAllRoots);
344  }
345  {
346    // TODO: don't visit the transaction roots if it's not active.
347    TimingLogger::ScopedTiming split5("VisitNonThreadRoots", GetTimings());
348    Runtime::Current()->VisitNonThreadRoots(this);
349  }
350
351  // Immune spaces.
352  for (auto& space : heap_->GetContinuousSpaces()) {
353    if (immune_region_.ContainsSpace(space)) {
354      DCHECK(space->IsImageSpace() || space->IsZygoteSpace());
355      accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap();
356      ConcurrentCopyingImmuneSpaceObjVisitor visitor(this);
357      live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
358                                    reinterpret_cast<uintptr_t>(space->Limit()),
359                                    visitor);
360    }
361  }
362
363  Thread* self = Thread::Current();
364  {
365    TimingLogger::ScopedTiming split6("ProcessMarkStack", GetTimings());
366    // Process the mark stack and issue an empty check point. If the
367    // mark stack is still empty after the check point, we're
368    // done. Otherwise, repeat.
369    ProcessMarkStack();
370    size_t count = 0;
371    while (!ProcessMarkStack()) {
372      ++count;
373      if (kVerboseMode) {
374        LOG(INFO) << "Issue an empty check point. " << count;
375      }
376      IssueEmptyCheckpoint();
377    }
378    // Need to ensure the mark stack is empty before reference
379    // processing to get rid of non-reference gray objects.
380    CheckEmptyMarkQueue();
381    // Enable the GetReference slow path and disallow access to the system weaks.
382    GetHeap()->GetReferenceProcessor()->EnableSlowPath();
383    Runtime::Current()->DisallowNewSystemWeaks();
384    QuasiAtomic::ThreadFenceForConstructor();
385    // Lock-unlock the system weak locks so that there's no thread in
386    // the middle of accessing system weaks.
387    Runtime::Current()->EnsureNewSystemWeaksDisallowed();
388    // Note: Do not issue a checkpoint from here to the
389    // SweepSystemWeaks call or else a deadlock due to
390    // WaitHoldingLocks() would occur.
391    if (kVerboseMode) {
392      LOG(INFO) << "Enabled the ref proc slow path & disabled access to system weaks.";
393      LOG(INFO) << "ProcessReferences";
394    }
395    ProcessReferences(self, true);
396    CheckEmptyMarkQueue();
397    if (kVerboseMode) {
398      LOG(INFO) << "SweepSystemWeaks";
399    }
400    SweepSystemWeaks(self);
401    if (kVerboseMode) {
402      LOG(INFO) << "SweepSystemWeaks done";
403    }
404    // Because hash_set::Erase() can call the hash function for
405    // arbitrary elements in the weak intern table in
406    // InternTable::Table::SweepWeaks(), the above SweepSystemWeaks()
407    // call may have marked some objects (strings) alive. So process
408    // the mark stack here once again.
409    ProcessMarkStack();
410    CheckEmptyMarkQueue();
411    // Disable marking.
412    if (kUseTableLookupReadBarrier) {
413      heap_->rb_table_->ClearAll();
414      DCHECK(heap_->rb_table_->IsAllCleared());
415    }
416    is_mark_queue_push_disallowed_.StoreSequentiallyConsistent(1);
417    is_marking_ = false;
418    if (kVerboseMode) {
419      LOG(INFO) << "AllowNewSystemWeaks";
420    }
421    Runtime::Current()->AllowNewSystemWeaks();
422    CheckEmptyMarkQueue();
423  }
424
425  if (kVerboseMode) {
426    LOG(INFO) << "GC end of MarkingPhase";
427  }
428}
429
430void ConcurrentCopying::IssueEmptyCheckpoint() {
431  Thread* self = Thread::Current();
432  EmptyCheckpoint check_point(this);
433  ThreadList* thread_list = Runtime::Current()->GetThreadList();
434  gc_barrier_->Init(self, 0);
435  size_t barrier_count = thread_list->RunCheckpoint(&check_point);
436  // If there are no threads to wait which implys that all the checkpoint functions are finished,
437  // then no need to release the mutator lock.
438  if (barrier_count == 0) {
439    return;
440  }
441  // Release locks then wait for all mutator threads to pass the barrier.
442  Locks::mutator_lock_->SharedUnlock(self);
443  {
444    ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
445    gc_barrier_->Increment(self, barrier_count);
446  }
447  Locks::mutator_lock_->SharedLock(self);
448}
449
450mirror::Object* ConcurrentCopying::PopOffMarkStack() {
451  return mark_queue_.Dequeue();
452}
453
454template<bool kThreadSafe>
455void ConcurrentCopying::PushOntoMarkStack(mirror::Object* to_ref) {
456  CHECK_EQ(is_mark_queue_push_disallowed_.LoadRelaxed(), 0)
457      << " " << to_ref << " " << PrettyTypeOf(to_ref);
458  if (kThreadSafe) {
459    CHECK(mark_queue_.Enqueue(to_ref)) << "Mark queue overflow";
460  } else {
461    CHECK(mark_queue_.EnqueueThreadUnsafe(to_ref)) << "Mark queue overflow";
462  }
463}
464
465accounting::ObjectStack* ConcurrentCopying::GetAllocationStack() {
466  return heap_->allocation_stack_.get();
467}
468
469accounting::ObjectStack* ConcurrentCopying::GetLiveStack() {
470  return heap_->live_stack_.get();
471}
472
473inline mirror::Object* ConcurrentCopying::GetFwdPtr(mirror::Object* from_ref) {
474  DCHECK(region_space_->IsInFromSpace(from_ref));
475  LockWord lw = from_ref->GetLockWord(false);
476  if (lw.GetState() == LockWord::kForwardingAddress) {
477    mirror::Object* fwd_ptr = reinterpret_cast<mirror::Object*>(lw.ForwardingAddress());
478    CHECK(fwd_ptr != nullptr);
479    return fwd_ptr;
480  } else {
481    return nullptr;
482  }
483}
484
485// The following visitors are that used to verify that there's no
486// references to the from-space left after marking.
487class ConcurrentCopyingVerifyNoFromSpaceRefsVisitor : public SingleRootVisitor {
488 public:
489  explicit ConcurrentCopyingVerifyNoFromSpaceRefsVisitor(ConcurrentCopying* collector)
490      : collector_(collector) {}
491
492  void operator()(mirror::Object* ref) const
493      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
494    if (ref == nullptr) {
495      // OK.
496      return;
497    }
498    collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
499    if (kUseBakerReadBarrier) {
500      if (collector_->RegionSpace()->IsInToSpace(ref)) {
501        CHECK(ref->GetReadBarrierPointer() == nullptr)
502            << "To-space ref " << ref << " " << PrettyTypeOf(ref)
503            << " has non-white rb_ptr " << ref->GetReadBarrierPointer();
504      } else {
505        CHECK(ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
506              (ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
507               collector_->IsOnAllocStack(ref)))
508            << "Non-moving/unevac from space ref " << ref << " " << PrettyTypeOf(ref)
509            << " has non-black rb_ptr " << ref->GetReadBarrierPointer()
510            << " but isn't on the alloc stack (and has white rb_ptr)."
511            << " Is it in the non-moving space="
512            << (collector_->GetHeap()->GetNonMovingSpace()->HasAddress(ref));
513      }
514    }
515  }
516
517  void VisitRoot(mirror::Object* root, const RootInfo& info ATTRIBUTE_UNUSED)
518      OVERRIDE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
519    DCHECK(root != nullptr);
520    operator()(root);
521  }
522
523 private:
524  ConcurrentCopying* const collector_;
525};
526
527class ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor {
528 public:
529  explicit ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor(ConcurrentCopying* collector)
530      : collector_(collector) {}
531
532  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */) const
533      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
534    mirror::Object* ref =
535        obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
536    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor visitor(collector_);
537    visitor(ref);
538  }
539  void operator()(mirror::Class* klass, mirror::Reference* ref) const
540      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
541    CHECK(klass->IsTypeOfReferenceClass());
542    this->operator()(ref, mirror::Reference::ReferentOffset(), false);
543  }
544
545 private:
546  ConcurrentCopying* collector_;
547};
548
549class ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor {
550 public:
551  explicit ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor(ConcurrentCopying* collector)
552      : collector_(collector) {}
553  void operator()(mirror::Object* obj) const
554      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
555    ObjectCallback(obj, collector_);
556  }
557  static void ObjectCallback(mirror::Object* obj, void *arg)
558      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
559    CHECK(obj != nullptr);
560    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
561    space::RegionSpace* region_space = collector->RegionSpace();
562    CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
563    ConcurrentCopyingVerifyNoFromSpaceRefsFieldVisitor visitor(collector);
564    obj->VisitReferences<true>(visitor, visitor);
565    if (kUseBakerReadBarrier) {
566      if (collector->RegionSpace()->IsInToSpace(obj)) {
567        CHECK(obj->GetReadBarrierPointer() == nullptr)
568            << "obj=" << obj << " non-white rb_ptr " << obj->GetReadBarrierPointer();
569      } else {
570        CHECK(obj->GetReadBarrierPointer() == ReadBarrier::BlackPtr() ||
571              (obj->GetReadBarrierPointer() == ReadBarrier::WhitePtr() &&
572               collector->IsOnAllocStack(obj)))
573            << "Non-moving space/unevac from space ref " << obj << " " << PrettyTypeOf(obj)
574            << " has non-black rb_ptr " << obj->GetReadBarrierPointer()
575            << " but isn't on the alloc stack (and has white rb_ptr). Is it in the non-moving space="
576            << (collector->GetHeap()->GetNonMovingSpace()->HasAddress(obj));
577      }
578    }
579  }
580
581 private:
582  ConcurrentCopying* const collector_;
583};
584
585// Verify there's no from-space references left after the marking phase.
586void ConcurrentCopying::VerifyNoFromSpaceReferences() {
587  Thread* self = Thread::Current();
588  DCHECK(Locks::mutator_lock_->IsExclusiveHeld(self));
589  ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor visitor(this);
590  // Roots.
591  {
592    ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
593    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor ref_visitor(this);
594    Runtime::Current()->VisitRoots(&ref_visitor);
595  }
596  // The to-space.
597  region_space_->WalkToSpace(ConcurrentCopyingVerifyNoFromSpaceRefsObjectVisitor::ObjectCallback,
598                             this);
599  // Non-moving spaces.
600  {
601    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
602    heap_->GetMarkBitmap()->Visit(visitor);
603  }
604  // The alloc stack.
605  {
606    ConcurrentCopyingVerifyNoFromSpaceRefsVisitor ref_visitor(this);
607    for (auto* it = heap_->allocation_stack_->Begin(), *end = heap_->allocation_stack_->End();
608        it < end; ++it) {
609      mirror::Object* const obj = it->AsMirrorPtr();
610      if (obj != nullptr && obj->GetClass() != nullptr) {
611        // TODO: need to call this only if obj is alive?
612        ref_visitor(obj);
613        visitor(obj);
614      }
615    }
616  }
617  // TODO: LOS. But only refs in LOS are classes.
618}
619
620// The following visitors are used to assert the to-space invariant.
621class ConcurrentCopyingAssertToSpaceInvariantRefsVisitor {
622 public:
623  explicit ConcurrentCopyingAssertToSpaceInvariantRefsVisitor(ConcurrentCopying* collector)
624      : collector_(collector) {}
625
626  void operator()(mirror::Object* ref) const
627      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
628    if (ref == nullptr) {
629      // OK.
630      return;
631    }
632    collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref);
633  }
634  static void RootCallback(mirror::Object** root, void *arg, const RootInfo& /*root_info*/)
635      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
636    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
637    ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector);
638    DCHECK(root != nullptr);
639    visitor(*root);
640  }
641
642 private:
643  ConcurrentCopying* collector_;
644};
645
646class ConcurrentCopyingAssertToSpaceInvariantFieldVisitor {
647 public:
648  explicit ConcurrentCopyingAssertToSpaceInvariantFieldVisitor(ConcurrentCopying* collector)
649      : collector_(collector) {}
650
651  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */) const
652      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
653    mirror::Object* ref =
654        obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset);
655    ConcurrentCopyingAssertToSpaceInvariantRefsVisitor visitor(collector_);
656    visitor(ref);
657  }
658  void operator()(mirror::Class* klass, mirror::Reference* /* ref */) const
659      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
660    CHECK(klass->IsTypeOfReferenceClass());
661  }
662
663 private:
664  ConcurrentCopying* collector_;
665};
666
667class ConcurrentCopyingAssertToSpaceInvariantObjectVisitor {
668 public:
669  explicit ConcurrentCopyingAssertToSpaceInvariantObjectVisitor(ConcurrentCopying* collector)
670      : collector_(collector) {}
671  void operator()(mirror::Object* obj) const
672      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
673    ObjectCallback(obj, collector_);
674  }
675  static void ObjectCallback(mirror::Object* obj, void *arg)
676      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
677    CHECK(obj != nullptr);
678    ConcurrentCopying* collector = reinterpret_cast<ConcurrentCopying*>(arg);
679    space::RegionSpace* region_space = collector->RegionSpace();
680    CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space";
681    collector->AssertToSpaceInvariant(nullptr, MemberOffset(0), obj);
682    ConcurrentCopyingAssertToSpaceInvariantFieldVisitor visitor(collector);
683    obj->VisitReferences<true>(visitor, visitor);
684  }
685
686 private:
687  ConcurrentCopying* collector_;
688};
689
690bool ConcurrentCopying::ProcessMarkStack() {
691  if (kVerboseMode) {
692    LOG(INFO) << "ProcessMarkStack. ";
693  }
694  size_t count = 0;
695  mirror::Object* to_ref;
696  while ((to_ref = PopOffMarkStack()) != nullptr) {
697    ++count;
698    DCHECK(!region_space_->IsInFromSpace(to_ref));
699    if (kUseBakerReadBarrier) {
700      DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
701          << " " << to_ref << " " << to_ref->GetReadBarrierPointer()
702          << " is_marked=" << IsMarked(to_ref);
703    }
704    // Scan ref fields.
705    Scan(to_ref);
706    // Mark the gray ref as white or black.
707    if (kUseBakerReadBarrier) {
708      DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr())
709          << " " << to_ref << " " << to_ref->GetReadBarrierPointer()
710          << " is_marked=" << IsMarked(to_ref);
711    }
712    if (to_ref->GetClass<kVerifyNone, kWithoutReadBarrier>()->IsTypeOfReferenceClass() &&
713        to_ref->AsReference()->GetReferent<kWithoutReadBarrier>() != nullptr &&
714        !IsInToSpace(to_ref->AsReference()->GetReferent<kWithoutReadBarrier>())) {
715      // Leave References gray so that GetReferent() will trigger RB.
716      CHECK(to_ref->AsReference()->IsEnqueued()) << "Left unenqueued ref gray " << to_ref;
717    } else {
718      if (kUseBakerReadBarrier) {
719        if (region_space_->IsInToSpace(to_ref)) {
720          // If to-space, change from gray to white.
721          bool success = to_ref->AtomicSetReadBarrierPointer(ReadBarrier::GrayPtr(),
722                                                             ReadBarrier::WhitePtr());
723          CHECK(success) << "Must succeed as we won the race.";
724          CHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr());
725        } else {
726          // If non-moving space/unevac from space, change from gray
727          // to black. We can't change gray to white because it's not
728          // safe to use CAS if two threads change values in opposite
729          // directions (A->B and B->A). So, we change it to black to
730          // indicate non-moving objects that have been marked
731          // through. Note we'd need to change from black to white
732          // later (concurrently).
733          bool success = to_ref->AtomicSetReadBarrierPointer(ReadBarrier::GrayPtr(),
734                                                             ReadBarrier::BlackPtr());
735          CHECK(success) << "Must succeed as we won the race.";
736          CHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
737        }
738      }
739    }
740    if (ReadBarrier::kEnableToSpaceInvariantChecks || kIsDebugBuild) {
741      ConcurrentCopyingAssertToSpaceInvariantObjectVisitor visitor(this);
742      visitor(to_ref);
743    }
744  }
745  // Return true if the stack was empty.
746  return count == 0;
747}
748
749void ConcurrentCopying::CheckEmptyMarkQueue() {
750  if (!mark_queue_.IsEmpty()) {
751    while (!mark_queue_.IsEmpty()) {
752      mirror::Object* obj = mark_queue_.Dequeue();
753      if (kUseBakerReadBarrier) {
754        mirror::Object* rb_ptr = obj->GetReadBarrierPointer();
755        LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj) << " rb_ptr=" << rb_ptr
756                  << " is_marked=" << IsMarked(obj);
757      } else {
758        LOG(INFO) << "On mark queue : " << obj << " " << PrettyTypeOf(obj)
759                  << " is_marked=" << IsMarked(obj);
760      }
761    }
762    LOG(FATAL) << "mark queue is not empty";
763  }
764}
765
766void ConcurrentCopying::SweepSystemWeaks(Thread* self) {
767  TimingLogger::ScopedTiming split("SweepSystemWeaks", GetTimings());
768  ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_);
769  Runtime::Current()->SweepSystemWeaks(IsMarkedCallback, this);
770}
771
772void ConcurrentCopying::Sweep(bool swap_bitmaps) {
773  {
774    TimingLogger::ScopedTiming t("MarkStackAsLive", GetTimings());
775    accounting::ObjectStack* live_stack = heap_->GetLiveStack();
776    if (kEnableFromSpaceAccountingCheck) {
777      CHECK_GE(live_stack_freeze_size_, live_stack->Size());
778    }
779    heap_->MarkAllocStackAsLive(live_stack);
780    live_stack->Reset();
781  }
782  CHECK(mark_queue_.IsEmpty());
783  TimingLogger::ScopedTiming split("Sweep", GetTimings());
784  for (const auto& space : GetHeap()->GetContinuousSpaces()) {
785    if (space->IsContinuousMemMapAllocSpace()) {
786      space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace();
787      if (space == region_space_ || immune_region_.ContainsSpace(space)) {
788        continue;
789      }
790      TimingLogger::ScopedTiming split2(
791          alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", GetTimings());
792      RecordFree(alloc_space->Sweep(swap_bitmaps));
793    }
794  }
795  SweepLargeObjects(swap_bitmaps);
796}
797
798void ConcurrentCopying::SweepLargeObjects(bool swap_bitmaps) {
799  TimingLogger::ScopedTiming split("SweepLargeObjects", GetTimings());
800  RecordFreeLOS(heap_->GetLargeObjectsSpace()->Sweep(swap_bitmaps));
801}
802
803class ConcurrentCopyingClearBlackPtrsVisitor {
804 public:
805  explicit ConcurrentCopyingClearBlackPtrsVisitor(ConcurrentCopying* cc)
806      : collector_(cc) {}
807#ifndef USE_BAKER_OR_BROOKS_READ_BARRIER
808  NO_RETURN
809#endif
810  void operator()(mirror::Object* obj) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
811      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
812    DCHECK(obj != nullptr);
813    DCHECK(collector_->heap_->GetMarkBitmap()->Test(obj)) << obj;
814    DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << obj;
815    obj->SetReadBarrierPointer(ReadBarrier::WhitePtr());
816    DCHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
817  }
818
819 private:
820  ConcurrentCopying* const collector_;
821};
822
823// Clear the black ptrs in non-moving objects back to white.
824void ConcurrentCopying::ClearBlackPtrs() {
825  CHECK(kUseBakerReadBarrier);
826  TimingLogger::ScopedTiming split("ClearBlackPtrs", GetTimings());
827  ConcurrentCopyingClearBlackPtrsVisitor visitor(this);
828  for (auto& space : heap_->GetContinuousSpaces()) {
829    if (space == region_space_) {
830      continue;
831    }
832    accounting::ContinuousSpaceBitmap* mark_bitmap = space->GetMarkBitmap();
833    if (kVerboseMode) {
834      LOG(INFO) << "ClearBlackPtrs: " << *space << " bitmap: " << *mark_bitmap;
835    }
836    mark_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()),
837                                  reinterpret_cast<uintptr_t>(space->Limit()),
838                                  visitor);
839  }
840  space::LargeObjectSpace* large_object_space = heap_->GetLargeObjectsSpace();
841  large_object_space->GetMarkBitmap()->VisitMarkedRange(
842      reinterpret_cast<uintptr_t>(large_object_space->Begin()),
843      reinterpret_cast<uintptr_t>(large_object_space->End()),
844      visitor);
845  // Objects on the allocation stack?
846  if (ReadBarrier::kEnableReadBarrierInvariantChecks || kIsDebugBuild) {
847    size_t count = GetAllocationStack()->Size();
848    auto* it = GetAllocationStack()->Begin();
849    auto* end = GetAllocationStack()->End();
850    for (size_t i = 0; i < count; ++i, ++it) {
851      CHECK_LT(it, end);
852      mirror::Object* obj = it->AsMirrorPtr();
853      if (obj != nullptr) {
854        // Must have been cleared above.
855        CHECK_EQ(obj->GetReadBarrierPointer(), ReadBarrier::WhitePtr()) << obj;
856      }
857    }
858  }
859}
860
861void ConcurrentCopying::ReclaimPhase() {
862  TimingLogger::ScopedTiming split("ReclaimPhase", GetTimings());
863  if (kVerboseMode) {
864    LOG(INFO) << "GC ReclaimPhase";
865  }
866  Thread* self = Thread::Current();
867
868  {
869    // Double-check that the mark stack is empty.
870    // Note: need to set this after VerifyNoFromSpaceRef().
871    is_asserting_to_space_invariant_ = false;
872    QuasiAtomic::ThreadFenceForConstructor();
873    if (kVerboseMode) {
874      LOG(INFO) << "Issue an empty check point. ";
875    }
876    IssueEmptyCheckpoint();
877    // Disable the check.
878    is_mark_queue_push_disallowed_.StoreSequentiallyConsistent(0);
879    CheckEmptyMarkQueue();
880  }
881
882  {
883    // Record freed objects.
884    TimingLogger::ScopedTiming split2("RecordFree", GetTimings());
885    // Don't include thread-locals that are in the to-space.
886    uint64_t from_bytes = region_space_->GetBytesAllocatedInFromSpace();
887    uint64_t from_objects = region_space_->GetObjectsAllocatedInFromSpace();
888    uint64_t unevac_from_bytes = region_space_->GetBytesAllocatedInUnevacFromSpace();
889    uint64_t unevac_from_objects = region_space_->GetObjectsAllocatedInUnevacFromSpace();
890    uint64_t to_bytes = bytes_moved_.LoadSequentiallyConsistent();
891    uint64_t to_objects = objects_moved_.LoadSequentiallyConsistent();
892    if (kEnableFromSpaceAccountingCheck) {
893      CHECK_EQ(from_space_num_objects_at_first_pause_, from_objects + unevac_from_objects);
894      CHECK_EQ(from_space_num_bytes_at_first_pause_, from_bytes + unevac_from_bytes);
895    }
896    CHECK_LE(to_objects, from_objects);
897    CHECK_LE(to_bytes, from_bytes);
898    int64_t freed_bytes = from_bytes - to_bytes;
899    int64_t freed_objects = from_objects - to_objects;
900    if (kVerboseMode) {
901      LOG(INFO) << "RecordFree:"
902                << " from_bytes=" << from_bytes << " from_objects=" << from_objects
903                << " unevac_from_bytes=" << unevac_from_bytes << " unevac_from_objects=" << unevac_from_objects
904                << " to_bytes=" << to_bytes << " to_objects=" << to_objects
905                << " freed_bytes=" << freed_bytes << " freed_objects=" << freed_objects
906                << " from_space size=" << region_space_->FromSpaceSize()
907                << " unevac_from_space size=" << region_space_->UnevacFromSpaceSize()
908                << " to_space size=" << region_space_->ToSpaceSize();
909      LOG(INFO) << "(before) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
910    }
911    RecordFree(ObjectBytePair(freed_objects, freed_bytes));
912    if (kVerboseMode) {
913      LOG(INFO) << "(after) num_bytes_allocated=" << heap_->num_bytes_allocated_.LoadSequentiallyConsistent();
914    }
915  }
916
917  {
918    TimingLogger::ScopedTiming split3("ComputeUnevacFromSpaceLiveRatio", GetTimings());
919    ComputeUnevacFromSpaceLiveRatio();
920  }
921
922  {
923    TimingLogger::ScopedTiming split4("ClearFromSpace", GetTimings());
924    region_space_->ClearFromSpace();
925  }
926
927  {
928    WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
929    if (kUseBakerReadBarrier) {
930      ClearBlackPtrs();
931    }
932    Sweep(false);
933    SwapBitmaps();
934    heap_->UnBindBitmaps();
935
936    // Remove bitmaps for the immune spaces.
937    while (!cc_bitmaps_.empty()) {
938      accounting::ContinuousSpaceBitmap* cc_bitmap = cc_bitmaps_.back();
939      cc_heap_bitmap_->RemoveContinuousSpaceBitmap(cc_bitmap);
940      delete cc_bitmap;
941      cc_bitmaps_.pop_back();
942    }
943    region_space_bitmap_ = nullptr;
944  }
945
946  if (kVerboseMode) {
947    LOG(INFO) << "GC end of ReclaimPhase";
948  }
949}
950
951class ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor {
952 public:
953  explicit ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor(ConcurrentCopying* cc)
954      : collector_(cc) {}
955  void operator()(mirror::Object* ref) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
956      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
957    DCHECK(ref != nullptr);
958    DCHECK(collector_->region_space_bitmap_->Test(ref)) << ref;
959    DCHECK(collector_->region_space_->IsInUnevacFromSpace(ref)) << ref;
960    if (kUseBakerReadBarrier) {
961      DCHECK_EQ(ref->GetReadBarrierPointer(), ReadBarrier::BlackPtr()) << ref;
962      // Clear the black ptr.
963      ref->SetReadBarrierPointer(ReadBarrier::WhitePtr());
964    }
965    size_t obj_size = ref->SizeOf();
966    size_t alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
967    collector_->region_space_->AddLiveBytes(ref, alloc_size);
968  }
969
970 private:
971  ConcurrentCopying* collector_;
972};
973
974// Compute how much live objects are left in regions.
975void ConcurrentCopying::ComputeUnevacFromSpaceLiveRatio() {
976  region_space_->AssertAllRegionLiveBytesZeroOrCleared();
977  ConcurrentCopyingComputeUnevacFromSpaceLiveRatioVisitor visitor(this);
978  region_space_bitmap_->VisitMarkedRange(reinterpret_cast<uintptr_t>(region_space_->Begin()),
979                                         reinterpret_cast<uintptr_t>(region_space_->Limit()),
980                                         visitor);
981}
982
983// Assert the to-space invariant.
984void ConcurrentCopying::AssertToSpaceInvariant(mirror::Object* obj, MemberOffset offset,
985                                               mirror::Object* ref) {
986  CHECK(heap_->collector_type_ == kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_);
987  if (is_asserting_to_space_invariant_) {
988    if (region_space_->IsInToSpace(ref)) {
989      // OK.
990      return;
991    } else if (region_space_->IsInUnevacFromSpace(ref)) {
992      CHECK(region_space_bitmap_->Test(ref)) << ref;
993    } else if (region_space_->IsInFromSpace(ref)) {
994      // Not OK. Do extra logging.
995      if (obj != nullptr) {
996        if (kUseBakerReadBarrier) {
997          LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj)
998                    << " holder rb_ptr=" << obj->GetReadBarrierPointer();
999        } else {
1000          LOG(INFO) << "holder=" << obj << " " << PrettyTypeOf(obj);
1001        }
1002        if (region_space_->IsInFromSpace(obj)) {
1003          LOG(INFO) << "holder is in the from-space.";
1004        } else if (region_space_->IsInToSpace(obj)) {
1005          LOG(INFO) << "holder is in the to-space.";
1006        } else if (region_space_->IsInUnevacFromSpace(obj)) {
1007          LOG(INFO) << "holder is in the unevac from-space.";
1008          if (region_space_bitmap_->Test(obj)) {
1009            LOG(INFO) << "holder is marked in the region space bitmap.";
1010          } else {
1011            LOG(INFO) << "holder is not marked in the region space bitmap.";
1012          }
1013        } else {
1014          // In a non-moving space.
1015          if (immune_region_.ContainsObject(obj)) {
1016            LOG(INFO) << "holder is in the image or the zygote space.";
1017            accounting::ContinuousSpaceBitmap* cc_bitmap =
1018                cc_heap_bitmap_->GetContinuousSpaceBitmap(obj);
1019            CHECK(cc_bitmap != nullptr)
1020                << "An immune space object must have a bitmap.";
1021            if (cc_bitmap->Test(obj)) {
1022              LOG(INFO) << "holder is marked in the bit map.";
1023            } else {
1024              LOG(INFO) << "holder is NOT marked in the bit map.";
1025            }
1026          } else {
1027            LOG(INFO) << "holder is in a non-moving (or main) space.";
1028            accounting::ContinuousSpaceBitmap* mark_bitmap =
1029                heap_mark_bitmap_->GetContinuousSpaceBitmap(obj);
1030            accounting::LargeObjectBitmap* los_bitmap =
1031                heap_mark_bitmap_->GetLargeObjectBitmap(obj);
1032            CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1033            bool is_los = mark_bitmap == nullptr;
1034            if (!is_los && mark_bitmap->Test(obj)) {
1035              LOG(INFO) << "holder is marked in the mark bit map.";
1036            } else if (is_los && los_bitmap->Test(obj)) {
1037              LOG(INFO) << "holder is marked in the los bit map.";
1038            } else {
1039              // If ref is on the allocation stack, then it is considered
1040              // mark/alive (but not necessarily on the live stack.)
1041              if (IsOnAllocStack(obj)) {
1042                LOG(INFO) << "holder is on the alloc stack.";
1043              } else {
1044                LOG(INFO) << "holder is not marked or on the alloc stack.";
1045              }
1046            }
1047          }
1048        }
1049        LOG(INFO) << "offset=" << offset.SizeValue();
1050      }
1051      CHECK(false) << "Found from-space ref " << ref << " " << PrettyTypeOf(ref);
1052    } else {
1053      // In a non-moving spaces. Check that the ref is marked.
1054      if (immune_region_.ContainsObject(ref)) {
1055        accounting::ContinuousSpaceBitmap* cc_bitmap =
1056            cc_heap_bitmap_->GetContinuousSpaceBitmap(ref);
1057        CHECK(cc_bitmap != nullptr)
1058            << "An immune space ref must have a bitmap. " << ref;
1059        if (kUseBakerReadBarrier) {
1060          CHECK(cc_bitmap->Test(ref))
1061              << "Unmarked immune space ref. obj=" << obj << " rb_ptr="
1062              << obj->GetReadBarrierPointer() << " ref=" << ref;
1063        } else {
1064          CHECK(cc_bitmap->Test(ref))
1065              << "Unmarked immune space ref. obj=" << obj << " ref=" << ref;
1066        }
1067      } else {
1068        accounting::ContinuousSpaceBitmap* mark_bitmap =
1069            heap_mark_bitmap_->GetContinuousSpaceBitmap(ref);
1070        accounting::LargeObjectBitmap* los_bitmap =
1071            heap_mark_bitmap_->GetLargeObjectBitmap(ref);
1072        CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1073        bool is_los = mark_bitmap == nullptr;
1074        if ((!is_los && mark_bitmap->Test(ref)) ||
1075            (is_los && los_bitmap->Test(ref))) {
1076          // OK.
1077        } else {
1078          // If ref is on the allocation stack, then it may not be
1079          // marked live, but considered marked/alive (but not
1080          // necessarily on the live stack).
1081          CHECK(IsOnAllocStack(ref)) << "Unmarked ref that's not on the allocation stack. "
1082                                     << "obj=" << obj << " ref=" << ref;
1083        }
1084      }
1085    }
1086  }
1087}
1088
1089// Used to scan ref fields of an object.
1090class ConcurrentCopyingRefFieldsVisitor {
1091 public:
1092  explicit ConcurrentCopyingRefFieldsVisitor(ConcurrentCopying* collector)
1093      : collector_(collector) {}
1094
1095  void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */)
1096      const ALWAYS_INLINE SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
1097      SHARED_LOCKS_REQUIRED(Locks::heap_bitmap_lock_) {
1098    collector_->Process(obj, offset);
1099  }
1100
1101  void operator()(mirror::Class* klass, mirror::Reference* ref) const
1102      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
1103    CHECK(klass->IsTypeOfReferenceClass());
1104    collector_->DelayReferenceReferent(klass, ref);
1105  }
1106
1107 private:
1108  ConcurrentCopying* const collector_;
1109};
1110
1111// Scan ref fields of an object.
1112void ConcurrentCopying::Scan(mirror::Object* to_ref) {
1113  DCHECK(!region_space_->IsInFromSpace(to_ref));
1114  ConcurrentCopyingRefFieldsVisitor visitor(this);
1115  to_ref->VisitReferences<true>(visitor, visitor);
1116}
1117
1118// Process a field.
1119inline void ConcurrentCopying::Process(mirror::Object* obj, MemberOffset offset) {
1120  mirror::Object* ref = obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset);
1121  if (ref == nullptr || region_space_->IsInToSpace(ref)) {
1122    return;
1123  }
1124  mirror::Object* to_ref = Mark(ref);
1125  if (to_ref == ref) {
1126    return;
1127  }
1128  // This may fail if the mutator writes to the field at the same time. But it's ok.
1129  mirror::Object* expected_ref = ref;
1130  mirror::Object* new_ref = to_ref;
1131  do {
1132    if (expected_ref !=
1133        obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset)) {
1134      // It was updated by the mutator.
1135      break;
1136    }
1137  } while (!obj->CasFieldWeakSequentiallyConsistentObjectWithoutWriteBarrier<false, false, kVerifyNone>(
1138      offset, expected_ref, new_ref));
1139}
1140
1141// Process some roots.
1142void ConcurrentCopying::VisitRoots(
1143    mirror::Object*** roots, size_t count, const RootInfo& info ATTRIBUTE_UNUSED) {
1144  for (size_t i = 0; i < count; ++i) {
1145    mirror::Object** root = roots[i];
1146    mirror::Object* ref = *root;
1147    if (ref == nullptr || region_space_->IsInToSpace(ref)) {
1148      return;
1149    }
1150    mirror::Object* to_ref = Mark(ref);
1151    if (to_ref == ref) {
1152      return;
1153    }
1154    Atomic<mirror::Object*>* addr = reinterpret_cast<Atomic<mirror::Object*>*>(root);
1155    mirror::Object* expected_ref = ref;
1156    mirror::Object* new_ref = to_ref;
1157    do {
1158      if (expected_ref != addr->LoadRelaxed()) {
1159        // It was updated by the mutator.
1160        break;
1161      }
1162    } while (!addr->CompareExchangeWeakSequentiallyConsistent(expected_ref, new_ref));
1163  }
1164}
1165
1166void ConcurrentCopying::VisitRoots(
1167    mirror::CompressedReference<mirror::Object>** roots, size_t count,
1168    const RootInfo& info ATTRIBUTE_UNUSED) {
1169  for (size_t i = 0; i < count; ++i) {
1170    mirror::CompressedReference<mirror::Object>* root = roots[i];
1171    mirror::Object* ref = root->AsMirrorPtr();
1172    if (ref == nullptr || region_space_->IsInToSpace(ref)) {
1173      return;
1174    }
1175    mirror::Object* to_ref = Mark(ref);
1176    if (to_ref == ref) {
1177      return;
1178    }
1179    auto* addr = reinterpret_cast<Atomic<mirror::CompressedReference<mirror::Object>>*>(root);
1180    auto expected_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(ref);
1181    auto new_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(to_ref);
1182    do {
1183      if (ref != addr->LoadRelaxed().AsMirrorPtr()) {
1184        // It was updated by the mutator.
1185        break;
1186      }
1187    } while (!addr->CompareExchangeWeakSequentiallyConsistent(expected_ref, new_ref));
1188  }
1189}
1190
1191// Fill the given memory block with a dummy object. Used to fill in a
1192// copy of objects that was lost in race.
1193void ConcurrentCopying::FillWithDummyObject(mirror::Object* dummy_obj, size_t byte_size) {
1194  CHECK(IsAligned<kObjectAlignment>(byte_size));
1195  memset(dummy_obj, 0, byte_size);
1196  mirror::Class* int_array_class = mirror::IntArray::GetArrayClass();
1197  CHECK(int_array_class != nullptr);
1198  AssertToSpaceInvariant(nullptr, MemberOffset(0), int_array_class);
1199  size_t component_size = int_array_class->GetComponentSize();
1200  CHECK_EQ(component_size, sizeof(int32_t));
1201  size_t data_offset = mirror::Array::DataOffset(component_size).SizeValue();
1202  if (data_offset > byte_size) {
1203    // An int array is too big. Use java.lang.Object.
1204    mirror::Class* java_lang_Object = WellKnownClasses::ToClass(WellKnownClasses::java_lang_Object);
1205    AssertToSpaceInvariant(nullptr, MemberOffset(0), java_lang_Object);
1206    CHECK_EQ(byte_size, java_lang_Object->GetObjectSize());
1207    dummy_obj->SetClass(java_lang_Object);
1208    CHECK_EQ(byte_size, dummy_obj->SizeOf());
1209  } else {
1210    // Use an int array.
1211    dummy_obj->SetClass(int_array_class);
1212    CHECK(dummy_obj->IsArrayInstance());
1213    int32_t length = (byte_size - data_offset) / component_size;
1214    dummy_obj->AsArray()->SetLength(length);
1215    CHECK_EQ(dummy_obj->AsArray()->GetLength(), length)
1216        << "byte_size=" << byte_size << " length=" << length
1217        << " component_size=" << component_size << " data_offset=" << data_offset;
1218    CHECK_EQ(byte_size, dummy_obj->SizeOf())
1219        << "byte_size=" << byte_size << " length=" << length
1220        << " component_size=" << component_size << " data_offset=" << data_offset;
1221  }
1222}
1223
1224// Reuse the memory blocks that were copy of objects that were lost in race.
1225mirror::Object* ConcurrentCopying::AllocateInSkippedBlock(size_t alloc_size) {
1226  // Try to reuse the blocks that were unused due to CAS failures.
1227  CHECK(IsAligned<space::RegionSpace::kAlignment>(alloc_size));
1228  Thread* self = Thread::Current();
1229  size_t min_object_size = RoundUp(sizeof(mirror::Object), space::RegionSpace::kAlignment);
1230  MutexLock mu(self, skipped_blocks_lock_);
1231  auto it = skipped_blocks_map_.lower_bound(alloc_size);
1232  if (it == skipped_blocks_map_.end()) {
1233    // Not found.
1234    return nullptr;
1235  }
1236  {
1237    size_t byte_size = it->first;
1238    CHECK_GE(byte_size, alloc_size);
1239    if (byte_size > alloc_size && byte_size - alloc_size < min_object_size) {
1240      // If remainder would be too small for a dummy object, retry with a larger request size.
1241      it = skipped_blocks_map_.lower_bound(alloc_size + min_object_size);
1242      if (it == skipped_blocks_map_.end()) {
1243        // Not found.
1244        return nullptr;
1245      }
1246      CHECK(IsAligned<space::RegionSpace::kAlignment>(it->first - alloc_size));
1247      CHECK_GE(it->first - alloc_size, min_object_size)
1248          << "byte_size=" << byte_size << " it->first=" << it->first << " alloc_size=" << alloc_size;
1249    }
1250  }
1251  // Found a block.
1252  CHECK(it != skipped_blocks_map_.end());
1253  size_t byte_size = it->first;
1254  uint8_t* addr = it->second;
1255  CHECK_GE(byte_size, alloc_size);
1256  CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr)));
1257  CHECK(IsAligned<space::RegionSpace::kAlignment>(byte_size));
1258  if (kVerboseMode) {
1259    LOG(INFO) << "Reusing skipped bytes : " << reinterpret_cast<void*>(addr) << ", " << byte_size;
1260  }
1261  skipped_blocks_map_.erase(it);
1262  memset(addr, 0, byte_size);
1263  if (byte_size > alloc_size) {
1264    // Return the remainder to the map.
1265    CHECK(IsAligned<space::RegionSpace::kAlignment>(byte_size - alloc_size));
1266    CHECK_GE(byte_size - alloc_size, min_object_size);
1267    FillWithDummyObject(reinterpret_cast<mirror::Object*>(addr + alloc_size),
1268                        byte_size - alloc_size);
1269    CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr + alloc_size)));
1270    skipped_blocks_map_.insert(std::make_pair(byte_size - alloc_size, addr + alloc_size));
1271  }
1272  return reinterpret_cast<mirror::Object*>(addr);
1273}
1274
1275mirror::Object* ConcurrentCopying::Copy(mirror::Object* from_ref) {
1276  DCHECK(region_space_->IsInFromSpace(from_ref));
1277  // No read barrier to avoid nested RB that might violate the to-space
1278  // invariant. Note that from_ref is a from space ref so the SizeOf()
1279  // call will access the from-space meta objects, but it's ok and necessary.
1280  size_t obj_size = from_ref->SizeOf<kDefaultVerifyFlags, kWithoutReadBarrier>();
1281  size_t region_space_alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment);
1282  size_t region_space_bytes_allocated = 0U;
1283  size_t non_moving_space_bytes_allocated = 0U;
1284  size_t bytes_allocated = 0U;
1285  size_t dummy;
1286  mirror::Object* to_ref = region_space_->AllocNonvirtual<true>(
1287      region_space_alloc_size, &region_space_bytes_allocated, nullptr, &dummy);
1288  bytes_allocated = region_space_bytes_allocated;
1289  if (to_ref != nullptr) {
1290    DCHECK_EQ(region_space_alloc_size, region_space_bytes_allocated);
1291  }
1292  bool fall_back_to_non_moving = false;
1293  if (UNLIKELY(to_ref == nullptr)) {
1294    // Failed to allocate in the region space. Try the skipped blocks.
1295    to_ref = AllocateInSkippedBlock(region_space_alloc_size);
1296    if (to_ref != nullptr) {
1297      // Succeeded to allocate in a skipped block.
1298      if (heap_->use_tlab_) {
1299        // This is necessary for the tlab case as it's not accounted in the space.
1300        region_space_->RecordAlloc(to_ref);
1301      }
1302      bytes_allocated = region_space_alloc_size;
1303    } else {
1304      // Fall back to the non-moving space.
1305      fall_back_to_non_moving = true;
1306      if (kVerboseMode) {
1307        LOG(INFO) << "Out of memory in the to-space. Fall back to non-moving. skipped_bytes="
1308                  << to_space_bytes_skipped_.LoadSequentiallyConsistent()
1309                  << " skipped_objects=" << to_space_objects_skipped_.LoadSequentiallyConsistent();
1310      }
1311      fall_back_to_non_moving = true;
1312      to_ref = heap_->non_moving_space_->Alloc(Thread::Current(), obj_size,
1313                                               &non_moving_space_bytes_allocated, nullptr, &dummy);
1314      CHECK(to_ref != nullptr) << "Fall-back non-moving space allocation failed";
1315      bytes_allocated = non_moving_space_bytes_allocated;
1316      // Mark it in the mark bitmap.
1317      accounting::ContinuousSpaceBitmap* mark_bitmap =
1318          heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
1319      CHECK(mark_bitmap != nullptr);
1320      CHECK(!mark_bitmap->AtomicTestAndSet(to_ref));
1321    }
1322  }
1323  DCHECK(to_ref != nullptr);
1324
1325  // Attempt to install the forward pointer. This is in a loop as the
1326  // lock word atomic write can fail.
1327  while (true) {
1328    // Copy the object. TODO: copy only the lockword in the second iteration and on?
1329    memcpy(to_ref, from_ref, obj_size);
1330    // Set the gray ptr.
1331    if (kUseBakerReadBarrier) {
1332      to_ref->SetReadBarrierPointer(ReadBarrier::GrayPtr());
1333    }
1334
1335    LockWord old_lock_word = to_ref->GetLockWord(false);
1336
1337    if (old_lock_word.GetState() == LockWord::kForwardingAddress) {
1338      // Lost the race. Another thread (either GC or mutator) stored
1339      // the forwarding pointer first. Make the lost copy (to_ref)
1340      // look like a valid but dead (dummy) object and keep it for
1341      // future reuse.
1342      FillWithDummyObject(to_ref, bytes_allocated);
1343      if (!fall_back_to_non_moving) {
1344        DCHECK(region_space_->IsInToSpace(to_ref));
1345        if (bytes_allocated > space::RegionSpace::kRegionSize) {
1346          // Free the large alloc.
1347          region_space_->FreeLarge(to_ref, bytes_allocated);
1348        } else {
1349          // Record the lost copy for later reuse.
1350          heap_->num_bytes_allocated_.FetchAndAddSequentiallyConsistent(bytes_allocated);
1351          to_space_bytes_skipped_.FetchAndAddSequentiallyConsistent(bytes_allocated);
1352          to_space_objects_skipped_.FetchAndAddSequentiallyConsistent(1);
1353          MutexLock mu(Thread::Current(), skipped_blocks_lock_);
1354          skipped_blocks_map_.insert(std::make_pair(bytes_allocated,
1355                                                    reinterpret_cast<uint8_t*>(to_ref)));
1356        }
1357      } else {
1358        DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
1359        DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
1360        // Free the non-moving-space chunk.
1361        accounting::ContinuousSpaceBitmap* mark_bitmap =
1362            heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref);
1363        CHECK(mark_bitmap != nullptr);
1364        CHECK(mark_bitmap->Clear(to_ref));
1365        heap_->non_moving_space_->Free(Thread::Current(), to_ref);
1366      }
1367
1368      // Get the winner's forward ptr.
1369      mirror::Object* lost_fwd_ptr = to_ref;
1370      to_ref = reinterpret_cast<mirror::Object*>(old_lock_word.ForwardingAddress());
1371      CHECK(to_ref != nullptr);
1372      CHECK_NE(to_ref, lost_fwd_ptr);
1373      CHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref));
1374      CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
1375      return to_ref;
1376    }
1377
1378    LockWord new_lock_word = LockWord::FromForwardingAddress(reinterpret_cast<size_t>(to_ref));
1379
1380    // Try to atomically write the fwd ptr.
1381    bool success = from_ref->CasLockWordWeakSequentiallyConsistent(old_lock_word, new_lock_word);
1382    if (LIKELY(success)) {
1383      // The CAS succeeded.
1384      objects_moved_.FetchAndAddSequentiallyConsistent(1);
1385      bytes_moved_.FetchAndAddSequentiallyConsistent(region_space_alloc_size);
1386      if (LIKELY(!fall_back_to_non_moving)) {
1387        DCHECK(region_space_->IsInToSpace(to_ref));
1388      } else {
1389        DCHECK(heap_->non_moving_space_->HasAddress(to_ref));
1390        DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated);
1391      }
1392      if (kUseBakerReadBarrier) {
1393        DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1394      }
1395      DCHECK(GetFwdPtr(from_ref) == to_ref);
1396      CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress);
1397      PushOntoMarkStack<true>(to_ref);
1398      return to_ref;
1399    } else {
1400      // The CAS failed. It may have lost the race or may have failed
1401      // due to monitor/hashcode ops. Either way, retry.
1402    }
1403  }
1404}
1405
1406mirror::Object* ConcurrentCopying::IsMarked(mirror::Object* from_ref) {
1407  DCHECK(from_ref != nullptr);
1408  space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref);
1409  if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) {
1410    // It's already marked.
1411    return from_ref;
1412  }
1413  mirror::Object* to_ref;
1414  if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) {
1415    to_ref = GetFwdPtr(from_ref);
1416    DCHECK(to_ref == nullptr || region_space_->IsInToSpace(to_ref) ||
1417           heap_->non_moving_space_->HasAddress(to_ref))
1418        << "from_ref=" << from_ref << " to_ref=" << to_ref;
1419  } else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) {
1420    if (region_space_bitmap_->Test(from_ref)) {
1421      to_ref = from_ref;
1422    } else {
1423      to_ref = nullptr;
1424    }
1425  } else {
1426    // from_ref is in a non-moving space.
1427    if (immune_region_.ContainsObject(from_ref)) {
1428      accounting::ContinuousSpaceBitmap* cc_bitmap =
1429          cc_heap_bitmap_->GetContinuousSpaceBitmap(from_ref);
1430      DCHECK(cc_bitmap != nullptr)
1431          << "An immune space object must have a bitmap";
1432      if (kIsDebugBuild) {
1433        DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref)->Test(from_ref))
1434            << "Immune space object must be already marked";
1435      }
1436      if (cc_bitmap->Test(from_ref)) {
1437        // Already marked.
1438        to_ref = from_ref;
1439      } else {
1440        // Newly marked.
1441        to_ref = nullptr;
1442      }
1443    } else {
1444      // Non-immune non-moving space. Use the mark bitmap.
1445      accounting::ContinuousSpaceBitmap* mark_bitmap =
1446          heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref);
1447      accounting::LargeObjectBitmap* los_bitmap =
1448          heap_mark_bitmap_->GetLargeObjectBitmap(from_ref);
1449      CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1450      bool is_los = mark_bitmap == nullptr;
1451      if (!is_los && mark_bitmap->Test(from_ref)) {
1452        // Already marked.
1453        to_ref = from_ref;
1454      } else if (is_los && los_bitmap->Test(from_ref)) {
1455        // Already marked in LOS.
1456        to_ref = from_ref;
1457      } else {
1458        // Not marked.
1459        if (IsOnAllocStack(from_ref)) {
1460          // If on the allocation stack, it's considered marked.
1461          to_ref = from_ref;
1462        } else {
1463          // Not marked.
1464          to_ref = nullptr;
1465        }
1466      }
1467    }
1468  }
1469  return to_ref;
1470}
1471
1472bool ConcurrentCopying::IsOnAllocStack(mirror::Object* ref) {
1473  QuasiAtomic::ThreadFenceAcquire();
1474  accounting::ObjectStack* alloc_stack = GetAllocationStack();
1475  return alloc_stack->Contains(ref);
1476}
1477
1478mirror::Object* ConcurrentCopying::Mark(mirror::Object* from_ref) {
1479  if (from_ref == nullptr) {
1480    return nullptr;
1481  }
1482  DCHECK(from_ref != nullptr);
1483  DCHECK(heap_->collector_type_ == kCollectorTypeCC);
1484  space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref);
1485  if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) {
1486    // It's already marked.
1487    return from_ref;
1488  }
1489  mirror::Object* to_ref;
1490  if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) {
1491    to_ref = GetFwdPtr(from_ref);
1492    if (kUseBakerReadBarrier) {
1493      DCHECK(to_ref != ReadBarrier::GrayPtr()) << "from_ref=" << from_ref << " to_ref=" << to_ref;
1494    }
1495    if (to_ref == nullptr) {
1496      // It isn't marked yet. Mark it by copying it to the to-space.
1497      to_ref = Copy(from_ref);
1498    }
1499    DCHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref))
1500        << "from_ref=" << from_ref << " to_ref=" << to_ref;
1501  } else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) {
1502    // This may or may not succeed, which is ok.
1503    if (kUseBakerReadBarrier) {
1504      from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1505    }
1506    if (region_space_bitmap_->AtomicTestAndSet(from_ref)) {
1507      // Already marked.
1508      to_ref = from_ref;
1509    } else {
1510      // Newly marked.
1511      to_ref = from_ref;
1512      if (kUseBakerReadBarrier) {
1513        DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1514      }
1515      PushOntoMarkStack<true>(to_ref);
1516    }
1517  } else {
1518    // from_ref is in a non-moving space.
1519    DCHECK(!region_space_->HasAddress(from_ref)) << from_ref;
1520    if (immune_region_.ContainsObject(from_ref)) {
1521      accounting::ContinuousSpaceBitmap* cc_bitmap =
1522          cc_heap_bitmap_->GetContinuousSpaceBitmap(from_ref);
1523      DCHECK(cc_bitmap != nullptr)
1524          << "An immune space object must have a bitmap";
1525      if (kIsDebugBuild) {
1526        DCHECK(heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref)->Test(from_ref))
1527            << "Immune space object must be already marked";
1528      }
1529      // This may or may not succeed, which is ok.
1530      if (kUseBakerReadBarrier) {
1531        from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1532      }
1533      if (cc_bitmap->AtomicTestAndSet(from_ref)) {
1534        // Already marked.
1535        to_ref = from_ref;
1536      } else {
1537        // Newly marked.
1538        to_ref = from_ref;
1539        if (kUseBakerReadBarrier) {
1540          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1541        }
1542        PushOntoMarkStack<true>(to_ref);
1543      }
1544    } else {
1545      // Use the mark bitmap.
1546      accounting::ContinuousSpaceBitmap* mark_bitmap =
1547          heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref);
1548      accounting::LargeObjectBitmap* los_bitmap =
1549          heap_mark_bitmap_->GetLargeObjectBitmap(from_ref);
1550      CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range";
1551      bool is_los = mark_bitmap == nullptr;
1552      if (!is_los && mark_bitmap->Test(from_ref)) {
1553        // Already marked.
1554        to_ref = from_ref;
1555        if (kUseBakerReadBarrier) {
1556          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
1557                 to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
1558        }
1559      } else if (is_los && los_bitmap->Test(from_ref)) {
1560        // Already marked in LOS.
1561        to_ref = from_ref;
1562        if (kUseBakerReadBarrier) {
1563          DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr() ||
1564                 to_ref->GetReadBarrierPointer() == ReadBarrier::BlackPtr());
1565        }
1566      } else {
1567        // Not marked.
1568        if (IsOnAllocStack(from_ref)) {
1569          // If it's on the allocation stack, it's considered marked. Keep it white.
1570          to_ref = from_ref;
1571          // Objects on the allocation stack need not be marked.
1572          if (!is_los) {
1573            DCHECK(!mark_bitmap->Test(to_ref));
1574          } else {
1575            DCHECK(!los_bitmap->Test(to_ref));
1576          }
1577          if (kUseBakerReadBarrier) {
1578            DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::WhitePtr());
1579          }
1580        } else {
1581          // Not marked or on the allocation stack. Try to mark it.
1582          // This may or may not succeed, which is ok.
1583          if (kUseBakerReadBarrier) {
1584            from_ref->AtomicSetReadBarrierPointer(ReadBarrier::WhitePtr(), ReadBarrier::GrayPtr());
1585          }
1586          if (!is_los && mark_bitmap->AtomicTestAndSet(from_ref)) {
1587            // Already marked.
1588            to_ref = from_ref;
1589          } else if (is_los && los_bitmap->AtomicTestAndSet(from_ref)) {
1590            // Already marked in LOS.
1591            to_ref = from_ref;
1592          } else {
1593            // Newly marked.
1594            to_ref = from_ref;
1595            if (kUseBakerReadBarrier) {
1596              DCHECK(to_ref->GetReadBarrierPointer() == ReadBarrier::GrayPtr());
1597            }
1598            PushOntoMarkStack<true>(to_ref);
1599          }
1600        }
1601      }
1602    }
1603  }
1604  return to_ref;
1605}
1606
1607void ConcurrentCopying::FinishPhase() {
1608  region_space_ = nullptr;
1609  CHECK(mark_queue_.IsEmpty());
1610  mark_queue_.Clear();
1611  {
1612    MutexLock mu(Thread::Current(), skipped_blocks_lock_);
1613    skipped_blocks_map_.clear();
1614  }
1615  WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
1616  heap_->ClearMarkedObjects();
1617}
1618
1619mirror::Object* ConcurrentCopying::IsMarkedCallback(mirror::Object* from_ref, void* arg) {
1620  return reinterpret_cast<ConcurrentCopying*>(arg)->IsMarked(from_ref);
1621}
1622
1623bool ConcurrentCopying::IsHeapReferenceMarkedCallback(
1624    mirror::HeapReference<mirror::Object>* field, void* arg) {
1625  mirror::Object* from_ref = field->AsMirrorPtr();
1626  mirror::Object* to_ref = reinterpret_cast<ConcurrentCopying*>(arg)->IsMarked(from_ref);
1627  if (to_ref == nullptr) {
1628    return false;
1629  }
1630  if (from_ref != to_ref) {
1631    QuasiAtomic::ThreadFenceRelease();
1632    field->Assign(to_ref);
1633    QuasiAtomic::ThreadFenceSequentiallyConsistent();
1634  }
1635  return true;
1636}
1637
1638mirror::Object* ConcurrentCopying::MarkCallback(mirror::Object* from_ref, void* arg) {
1639  return reinterpret_cast<ConcurrentCopying*>(arg)->Mark(from_ref);
1640}
1641
1642void ConcurrentCopying::ProcessMarkStackCallback(void* arg) {
1643  reinterpret_cast<ConcurrentCopying*>(arg)->ProcessMarkStack();
1644}
1645
1646void ConcurrentCopying::DelayReferenceReferent(mirror::Class* klass, mirror::Reference* reference) {
1647  heap_->GetReferenceProcessor()->DelayReferenceReferent(
1648      klass, reference, &IsHeapReferenceMarkedCallback, this);
1649}
1650
1651void ConcurrentCopying::ProcessReferences(Thread* self, bool concurrent) {
1652  TimingLogger::ScopedTiming split("ProcessReferences", GetTimings());
1653  WriterMutexLock mu(self, *Locks::heap_bitmap_lock_);
1654  GetHeap()->GetReferenceProcessor()->ProcessReferences(
1655      concurrent, GetTimings(), GetCurrentIteration()->GetClearSoftReferences(),
1656      &IsHeapReferenceMarkedCallback, &MarkCallback, &ProcessMarkStackCallback, this);
1657}
1658
1659void ConcurrentCopying::RevokeAllThreadLocalBuffers() {
1660  TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings());
1661  region_space_->RevokeAllThreadLocalBuffers();
1662}
1663
1664}  // namespace collector
1665}  // namespace gc
1666}  // namespace art
1667