| /* |
| * Copyright (C) 2014 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 |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "concurrent_copying.h" |
| |
| #include "art_field-inl.h" |
| #include "base/enums.h" |
| #include "base/file_utils.h" |
| #include "base/histogram-inl.h" |
| #include "base/quasi_atomic.h" |
| #include "base/stl_util.h" |
| #include "base/systrace.h" |
| #include "class_root.h" |
| #include "debugger.h" |
| #include "gc/accounting/atomic_stack.h" |
| #include "gc/accounting/heap_bitmap-inl.h" |
| #include "gc/accounting/mod_union_table-inl.h" |
| #include "gc/accounting/read_barrier_table.h" |
| #include "gc/accounting/space_bitmap-inl.h" |
| #include "gc/gc_pause_listener.h" |
| #include "gc/reference_processor.h" |
| #include "gc/space/image_space.h" |
| #include "gc/space/space-inl.h" |
| #include "gc/verification.h" |
| #include "image-inl.h" |
| #include "intern_table.h" |
| #include "mirror/class-inl.h" |
| #include "mirror/object-inl.h" |
| #include "mirror/object-refvisitor-inl.h" |
| #include "scoped_thread_state_change-inl.h" |
| #include "thread-inl.h" |
| #include "thread_list.h" |
| #include "well_known_classes.h" |
| |
| namespace art { |
| namespace gc { |
| namespace collector { |
| |
| static constexpr size_t kDefaultGcMarkStackSize = 2 * MB; |
| // If kFilterModUnionCards then we attempt to filter cards that don't need to be dirty in the mod |
| // union table. Disabled since it does not seem to help the pause much. |
| static constexpr bool kFilterModUnionCards = kIsDebugBuild; |
| // If kDisallowReadBarrierDuringScan is true then the GC aborts if there are any read barrier that |
| // occur during ConcurrentCopying::Scan in GC thread. May be used to diagnose possibly unnecessary |
| // read barriers. Only enabled for kIsDebugBuild to avoid performance hit. |
| static constexpr bool kDisallowReadBarrierDuringScan = kIsDebugBuild; |
| // Slow path mark stack size, increase this if the stack is getting full and it is causing |
| // performance problems. |
| static constexpr size_t kReadBarrierMarkStackSize = 512 * KB; |
| // Size (in the number of objects) of the sweep array free buffer. |
| static constexpr size_t kSweepArrayChunkFreeSize = 1024; |
| // Verify that there are no missing card marks. |
| static constexpr bool kVerifyNoMissingCardMarks = kIsDebugBuild; |
| |
| ConcurrentCopying::ConcurrentCopying(Heap* heap, |
| bool young_gen, |
| const std::string& name_prefix, |
| bool measure_read_barrier_slow_path) |
| : GarbageCollector(heap, |
| name_prefix + (name_prefix.empty() ? "" : " ") + |
| "concurrent copying"), |
| region_space_(nullptr), gc_barrier_(new Barrier(0)), |
| gc_mark_stack_(accounting::ObjectStack::Create("concurrent copying gc mark stack", |
| kDefaultGcMarkStackSize, |
| kDefaultGcMarkStackSize)), |
| rb_mark_bit_stack_(accounting::ObjectStack::Create("rb copying gc mark stack", |
| kReadBarrierMarkStackSize, |
| kReadBarrierMarkStackSize)), |
| rb_mark_bit_stack_full_(false), |
| mark_stack_lock_("concurrent copying mark stack lock", kMarkSweepMarkStackLock), |
| thread_running_gc_(nullptr), |
| is_marking_(false), |
| is_using_read_barrier_entrypoints_(false), |
| is_active_(false), |
| is_asserting_to_space_invariant_(false), |
| region_space_bitmap_(nullptr), |
| heap_mark_bitmap_(nullptr), |
| live_stack_freeze_size_(0), |
| from_space_num_objects_at_first_pause_(0), |
| from_space_num_bytes_at_first_pause_(0), |
| mark_stack_mode_(kMarkStackModeOff), |
| weak_ref_access_enabled_(true), |
| copied_live_bytes_ratio_sum_(0.f), |
| gc_count_(0), |
| young_gen_(young_gen), |
| skipped_blocks_lock_("concurrent copying bytes blocks lock", kMarkSweepMarkStackLock), |
| measure_read_barrier_slow_path_(measure_read_barrier_slow_path), |
| mark_from_read_barrier_measurements_(false), |
| rb_slow_path_ns_(0), |
| rb_slow_path_count_(0), |
| rb_slow_path_count_gc_(0), |
| rb_slow_path_histogram_lock_("Read barrier histogram lock"), |
| rb_slow_path_time_histogram_("Mutator time in read barrier slow path", 500, 32), |
| rb_slow_path_count_total_(0), |
| rb_slow_path_count_gc_total_(0), |
| rb_table_(heap_->GetReadBarrierTable()), |
| force_evacuate_all_(false), |
| gc_grays_immune_objects_(false), |
| immune_gray_stack_lock_("concurrent copying immune gray stack lock", |
| kMarkSweepMarkStackLock) { |
| static_assert(space::RegionSpace::kRegionSize == accounting::ReadBarrierTable::kRegionSize, |
| "The region space size and the read barrier table region size must match"); |
| CHECK(kEnableGenerationalConcurrentCopyingCollection || !young_gen_); |
| Thread* self = Thread::Current(); |
| { |
| ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| // Cache this so that we won't have to lock heap_bitmap_lock_ in |
| // Mark() which could cause a nested lock on heap_bitmap_lock_ |
| // when GC causes a RB while doing GC or a lock order violation |
| // (class_linker_lock_ and heap_bitmap_lock_). |
| heap_mark_bitmap_ = heap->GetMarkBitmap(); |
| } |
| { |
| MutexLock mu(self, mark_stack_lock_); |
| for (size_t i = 0; i < kMarkStackPoolSize; ++i) { |
| accounting::AtomicStack<mirror::Object>* mark_stack = |
| accounting::AtomicStack<mirror::Object>::Create( |
| "thread local mark stack", kMarkStackSize, kMarkStackSize); |
| pooled_mark_stacks_.push_back(mark_stack); |
| } |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection) { |
| // Allocate sweep array free buffer. |
| std::string error_msg; |
| sweep_array_free_buffer_mem_map_ = MemMap::MapAnonymous( |
| "concurrent copying sweep array free buffer", |
| RoundUp(kSweepArrayChunkFreeSize * sizeof(mirror::Object*), kPageSize), |
| PROT_READ | PROT_WRITE, |
| /*low_4gb=*/ false, |
| &error_msg); |
| CHECK(sweep_array_free_buffer_mem_map_.IsValid()) |
| << "Couldn't allocate sweep array free buffer: " << error_msg; |
| } |
| } |
| |
| void ConcurrentCopying::MarkHeapReference(mirror::HeapReference<mirror::Object>* field, |
| bool do_atomic_update) { |
| Thread* const self = Thread::Current(); |
| if (UNLIKELY(do_atomic_update)) { |
| // Used to mark the referent in DelayReferenceReferent in transaction mode. |
| mirror::Object* from_ref = field->AsMirrorPtr(); |
| if (from_ref == nullptr) { |
| return; |
| } |
| mirror::Object* to_ref = Mark(self, from_ref); |
| if (from_ref != to_ref) { |
| do { |
| if (field->AsMirrorPtr() != from_ref) { |
| // Concurrently overwritten by a mutator. |
| break; |
| } |
| } while (!field->CasWeakRelaxed(from_ref, to_ref)); |
| } |
| } else { |
| // Used for preserving soft references, should be OK to not have a CAS here since there should be |
| // no other threads which can trigger read barriers on the same referent during reference |
| // processing. |
| field->Assign(Mark(self, field->AsMirrorPtr())); |
| } |
| } |
| |
| ConcurrentCopying::~ConcurrentCopying() { |
| STLDeleteElements(&pooled_mark_stacks_); |
| } |
| |
| void ConcurrentCopying::RunPhases() { |
| CHECK(kUseBakerReadBarrier || kUseTableLookupReadBarrier); |
| CHECK(!is_active_); |
| is_active_ = true; |
| Thread* self = Thread::Current(); |
| thread_running_gc_ = self; |
| Locks::mutator_lock_->AssertNotHeld(self); |
| { |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| InitializePhase(); |
| } |
| if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) { |
| // Switch to read barrier mark entrypoints before we gray the objects. This is required in case |
| // a mutator sees a gray bit and dispatches on the entrypoint. (b/37876887). |
| ActivateReadBarrierEntrypoints(); |
| // Gray dirty immune objects concurrently to reduce GC pause times. We re-process gray cards in |
| // the pause. |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| GrayAllDirtyImmuneObjects(); |
| } |
| FlipThreadRoots(); |
| { |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| MarkingPhase(); |
| } |
| // Verify no from space refs. This causes a pause. |
| if (kEnableNoFromSpaceRefsVerification) { |
| TimingLogger::ScopedTiming split("(Paused)VerifyNoFromSpaceReferences", GetTimings()); |
| ScopedPause pause(this, false); |
| CheckEmptyMarkStack(); |
| if (kVerboseMode) { |
| LOG(INFO) << "Verifying no from-space refs"; |
| } |
| VerifyNoFromSpaceReferences(); |
| if (kVerboseMode) { |
| LOG(INFO) << "Done verifying no from-space refs"; |
| } |
| CheckEmptyMarkStack(); |
| } |
| { |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| ReclaimPhase(); |
| } |
| FinishPhase(); |
| CHECK(is_active_); |
| is_active_ = false; |
| thread_running_gc_ = nullptr; |
| } |
| |
| class ConcurrentCopying::ActivateReadBarrierEntrypointsCheckpoint : public Closure { |
| public: |
| explicit ActivateReadBarrierEntrypointsCheckpoint(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) {} |
| |
| void Run(Thread* thread) override NO_THREAD_SAFETY_ANALYSIS { |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* self = Thread::Current(); |
| DCHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc) |
| << thread->GetState() << " thread " << thread << " self " << self; |
| // Switch to the read barrier entrypoints. |
| thread->SetReadBarrierEntrypoints(); |
| // If thread is a running mutator, then act on behalf of the garbage collector. |
| // See the code in ThreadList::RunCheckpoint. |
| concurrent_copying_->GetBarrier().Pass(self); |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| class ConcurrentCopying::ActivateReadBarrierEntrypointsCallback : public Closure { |
| public: |
| explicit ActivateReadBarrierEntrypointsCallback(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) {} |
| |
| void Run(Thread* self ATTRIBUTE_UNUSED) override REQUIRES(Locks::thread_list_lock_) { |
| // This needs to run under the thread_list_lock_ critical section in ThreadList::RunCheckpoint() |
| // to avoid a race with ThreadList::Register(). |
| CHECK(!concurrent_copying_->is_using_read_barrier_entrypoints_); |
| concurrent_copying_->is_using_read_barrier_entrypoints_ = true; |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| void ConcurrentCopying::ActivateReadBarrierEntrypoints() { |
| Thread* const self = Thread::Current(); |
| ActivateReadBarrierEntrypointsCheckpoint checkpoint(this); |
| ThreadList* thread_list = Runtime::Current()->GetThreadList(); |
| gc_barrier_->Init(self, 0); |
| ActivateReadBarrierEntrypointsCallback callback(this); |
| const size_t barrier_count = thread_list->RunCheckpoint(&checkpoint, &callback); |
| // If there are no threads to wait which implies that all the checkpoint functions are finished, |
| // then no need to release the mutator lock. |
| if (barrier_count == 0) { |
| return; |
| } |
| ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun); |
| gc_barrier_->Increment(self, barrier_count); |
| } |
| |
| void ConcurrentCopying::BindBitmaps() { |
| Thread* self = Thread::Current(); |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| // Mark all of the spaces we never collect as immune. |
| for (const auto& space : heap_->GetContinuousSpaces()) { |
| if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect || |
| space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect) { |
| CHECK(space->IsZygoteSpace() || space->IsImageSpace()); |
| immune_spaces_.AddSpace(space); |
| } else { |
| CHECK(!space->IsZygoteSpace()); |
| CHECK(!space->IsImageSpace()); |
| if (kEnableGenerationalConcurrentCopyingCollection) { |
| if (space == region_space_) { |
| region_space_bitmap_ = region_space_->GetMarkBitmap(); |
| } else if (young_gen_ && space->IsContinuousMemMapAllocSpace()) { |
| DCHECK_EQ(space->GetGcRetentionPolicy(), space::kGcRetentionPolicyAlwaysCollect); |
| space->AsContinuousMemMapAllocSpace()->BindLiveToMarkBitmap(); |
| } |
| // Age all of the cards for the region space so that we know which evac regions to scan. |
| Runtime::Current()->GetHeap()->GetCardTable()->ModifyCardsAtomic( |
| space->Begin(), |
| space->End(), |
| AgeCardVisitor(), |
| VoidFunctor()); |
| } else { |
| if (space == region_space_) { |
| // It is OK to clear the bitmap with mutators running since the only place it is read is |
| // VisitObjects which has exclusion with CC. |
| region_space_bitmap_ = region_space_->GetMarkBitmap(); |
| region_space_bitmap_->Clear(); |
| } |
| } |
| } |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| for (const auto& space : GetHeap()->GetDiscontinuousSpaces()) { |
| CHECK(space->IsLargeObjectSpace()); |
| space->AsLargeObjectSpace()->CopyLiveToMarked(); |
| } |
| } |
| } |
| |
| void ConcurrentCopying::InitializePhase() { |
| TimingLogger::ScopedTiming split("InitializePhase", GetTimings()); |
| if (kVerboseMode) { |
| LOG(INFO) << "GC InitializePhase"; |
| LOG(INFO) << "Region-space : " << reinterpret_cast<void*>(region_space_->Begin()) << "-" |
| << reinterpret_cast<void*>(region_space_->Limit()); |
| } |
| CheckEmptyMarkStack(); |
| if (kIsDebugBuild) { |
| MutexLock mu(Thread::Current(), mark_stack_lock_); |
| CHECK(false_gray_stack_.empty()); |
| } |
| |
| rb_mark_bit_stack_full_ = false; |
| mark_from_read_barrier_measurements_ = measure_read_barrier_slow_path_; |
| if (measure_read_barrier_slow_path_) { |
| rb_slow_path_ns_.store(0, std::memory_order_relaxed); |
| rb_slow_path_count_.store(0, std::memory_order_relaxed); |
| rb_slow_path_count_gc_.store(0, std::memory_order_relaxed); |
| } |
| |
| immune_spaces_.Reset(); |
| bytes_moved_.store(0, std::memory_order_relaxed); |
| objects_moved_.store(0, std::memory_order_relaxed); |
| bytes_moved_gc_thread_ = 0; |
| objects_moved_gc_thread_ = 0; |
| GcCause gc_cause = GetCurrentIteration()->GetGcCause(); |
| |
| force_evacuate_all_ = false; |
| if (!kEnableGenerationalConcurrentCopyingCollection || !young_gen_) { |
| if (gc_cause == kGcCauseExplicit || |
| gc_cause == kGcCauseCollectorTransition || |
| GetCurrentIteration()->GetClearSoftReferences()) { |
| force_evacuate_all_ = true; |
| } |
| } |
| if (kUseBakerReadBarrier) { |
| updated_all_immune_objects_.store(false, std::memory_order_relaxed); |
| // GC may gray immune objects in the thread flip. |
| gc_grays_immune_objects_ = true; |
| if (kIsDebugBuild) { |
| MutexLock mu(Thread::Current(), immune_gray_stack_lock_); |
| DCHECK(immune_gray_stack_.empty()); |
| } |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection) { |
| done_scanning_.store(false, std::memory_order_release); |
| } |
| BindBitmaps(); |
| if (kVerboseMode) { |
| LOG(INFO) << "young_gen=" << std::boolalpha << young_gen_ << std::noboolalpha; |
| LOG(INFO) << "force_evacuate_all=" << std::boolalpha << force_evacuate_all_ << std::noboolalpha; |
| LOG(INFO) << "Largest immune region: " << immune_spaces_.GetLargestImmuneRegion().Begin() |
| << "-" << immune_spaces_.GetLargestImmuneRegion().End(); |
| for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) { |
| LOG(INFO) << "Immune space: " << *space; |
| } |
| LOG(INFO) << "GC end of InitializePhase"; |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection && !young_gen_) { |
| region_space_bitmap_->Clear(); |
| } |
| // Mark all of the zygote large objects without graying them. |
| MarkZygoteLargeObjects(); |
| } |
| |
| // Used to switch the thread roots of a thread from from-space refs to to-space refs. |
| class ConcurrentCopying::ThreadFlipVisitor : public Closure, public RootVisitor { |
| public: |
| ThreadFlipVisitor(ConcurrentCopying* concurrent_copying, bool use_tlab) |
| : concurrent_copying_(concurrent_copying), use_tlab_(use_tlab) { |
| } |
| |
| void Run(Thread* thread) override REQUIRES_SHARED(Locks::mutator_lock_) { |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* self = Thread::Current(); |
| CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc) |
| << thread->GetState() << " thread " << thread << " self " << self; |
| thread->SetIsGcMarkingAndUpdateEntrypoints(true); |
| if (use_tlab_ && thread->HasTlab()) { |
| if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) { |
| // This must come before the revoke. |
| size_t thread_local_objects = thread->GetThreadLocalObjectsAllocated(); |
| concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread); |
| reinterpret_cast<Atomic<size_t>*>( |
| &concurrent_copying_->from_space_num_objects_at_first_pause_)-> |
| fetch_add(thread_local_objects, std::memory_order_relaxed); |
| } else { |
| concurrent_copying_->region_space_->RevokeThreadLocalBuffers(thread); |
| } |
| } |
| if (kUseThreadLocalAllocationStack) { |
| thread->RevokeThreadLocalAllocationStack(); |
| } |
| ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| // We can use the non-CAS VisitRoots functions below because we update thread-local GC roots |
| // only. |
| thread->VisitRoots(this, kVisitRootFlagAllRoots); |
| concurrent_copying_->GetBarrier().Pass(self); |
| } |
| |
| void VisitRoots(mirror::Object*** roots, |
| size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) override |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| Thread* self = Thread::Current(); |
| for (size_t i = 0; i < count; ++i) { |
| mirror::Object** root = roots[i]; |
| mirror::Object* ref = *root; |
| if (ref != nullptr) { |
| mirror::Object* to_ref = concurrent_copying_->Mark(self, ref); |
| if (to_ref != ref) { |
| *root = to_ref; |
| } |
| } |
| } |
| } |
| |
| void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, |
| size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) override |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| Thread* self = Thread::Current(); |
| for (size_t i = 0; i < count; ++i) { |
| mirror::CompressedReference<mirror::Object>* const root = roots[i]; |
| if (!root->IsNull()) { |
| mirror::Object* ref = root->AsMirrorPtr(); |
| mirror::Object* to_ref = concurrent_copying_->Mark(self, ref); |
| if (to_ref != ref) { |
| root->Assign(to_ref); |
| } |
| } |
| } |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| const bool use_tlab_; |
| }; |
| |
| // Called back from Runtime::FlipThreadRoots() during a pause. |
| class ConcurrentCopying::FlipCallback : public Closure { |
| public: |
| explicit FlipCallback(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) { |
| } |
| |
| void Run(Thread* thread) override REQUIRES(Locks::mutator_lock_) { |
| ConcurrentCopying* cc = concurrent_copying_; |
| TimingLogger::ScopedTiming split("(Paused)FlipCallback", cc->GetTimings()); |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* self = Thread::Current(); |
| if (kVerifyNoMissingCardMarks) { |
| cc->VerifyNoMissingCardMarks(); |
| } |
| CHECK_EQ(thread, self); |
| Locks::mutator_lock_->AssertExclusiveHeld(self); |
| space::RegionSpace::EvacMode evac_mode = space::RegionSpace::kEvacModeLivePercentNewlyAllocated; |
| if (cc->young_gen_) { |
| CHECK(!cc->force_evacuate_all_); |
| evac_mode = space::RegionSpace::kEvacModeNewlyAllocated; |
| } else if (cc->force_evacuate_all_) { |
| evac_mode = space::RegionSpace::kEvacModeForceAll; |
| } |
| { |
| TimingLogger::ScopedTiming split2("(Paused)SetFromSpace", cc->GetTimings()); |
| // Only change live bytes for full CC. |
| cc->region_space_->SetFromSpace( |
| cc->rb_table_, evac_mode, /*clear_live_bytes=*/ !cc->young_gen_); |
| } |
| cc->SwapStacks(); |
| if (ConcurrentCopying::kEnableFromSpaceAccountingCheck) { |
| cc->RecordLiveStackFreezeSize(self); |
| cc->from_space_num_objects_at_first_pause_ = cc->region_space_->GetObjectsAllocated(); |
| cc->from_space_num_bytes_at_first_pause_ = cc->region_space_->GetBytesAllocated(); |
| } |
| cc->is_marking_ = true; |
| cc->mark_stack_mode_.store(ConcurrentCopying::kMarkStackModeThreadLocal, |
| std::memory_order_relaxed); |
| if (kIsDebugBuild && !cc->young_gen_) { |
| cc->region_space_->AssertAllRegionLiveBytesZeroOrCleared(); |
| } |
| if (UNLIKELY(Runtime::Current()->IsActiveTransaction())) { |
| CHECK(Runtime::Current()->IsAotCompiler()); |
| TimingLogger::ScopedTiming split3("(Paused)VisitTransactionRoots", cc->GetTimings()); |
| Runtime::Current()->VisitTransactionRoots(cc); |
| } |
| if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) { |
| cc->GrayAllNewlyDirtyImmuneObjects(); |
| if (kIsDebugBuild) { |
| // Check that all non-gray immune objects only reference immune objects. |
| cc->VerifyGrayImmuneObjects(); |
| } |
| } |
| // May be null during runtime creation, in this case leave java_lang_Object null. |
| // This is safe since single threaded behavior should mean FillDummyObject does not |
| // happen when java_lang_Object_ is null. |
| if (WellKnownClasses::java_lang_Object != nullptr) { |
| cc->java_lang_Object_ = down_cast<mirror::Class*>(cc->Mark(thread, |
| WellKnownClasses::ToClass(WellKnownClasses::java_lang_Object).Ptr())); |
| } else { |
| cc->java_lang_Object_ = nullptr; |
| } |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| class ConcurrentCopying::VerifyGrayImmuneObjectsVisitor { |
| public: |
| explicit VerifyGrayImmuneObjectsVisitor(ConcurrentCopying* collector) |
| : collector_(collector) {} |
| |
| void operator()(ObjPtr<mirror::Object> obj, MemberOffset offset, bool /* is_static */) |
| const ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) |
| REQUIRES_SHARED(Locks::heap_bitmap_lock_) { |
| CheckReference(obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier>(offset), |
| obj, offset); |
| } |
| |
| void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| CHECK(klass->IsTypeOfReferenceClass()); |
| CheckReference(ref->GetReferent<kWithoutReadBarrier>(), |
| ref, |
| mirror::Reference::ReferentOffset()); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| ALWAYS_INLINE |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| ALWAYS_INLINE |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| CheckReference(root->AsMirrorPtr(), nullptr, MemberOffset(0)); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| |
| void CheckReference(ObjPtr<mirror::Object> ref, |
| ObjPtr<mirror::Object> holder, |
| MemberOffset offset) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (ref != nullptr) { |
| if (!collector_->immune_spaces_.ContainsObject(ref.Ptr())) { |
| // Not immune, must be a zygote large object. |
| space::LargeObjectSpace* large_object_space = |
| Runtime::Current()->GetHeap()->GetLargeObjectsSpace(); |
| CHECK(large_object_space->Contains(ref.Ptr()) && |
| large_object_space->IsZygoteLargeObject(Thread::Current(), ref.Ptr())) |
| << "Non gray object references non immune, non zygote large object "<< ref << " " |
| << mirror::Object::PrettyTypeOf(ref) << " in holder " << holder << " " |
| << mirror::Object::PrettyTypeOf(holder) << " offset=" << offset.Uint32Value(); |
| } else { |
| // Make sure the large object class is immune since we will never scan the large object. |
| CHECK(collector_->immune_spaces_.ContainsObject( |
| ref->GetClass<kVerifyNone, kWithoutReadBarrier>())); |
| } |
| } |
| } |
| }; |
| |
| void ConcurrentCopying::VerifyGrayImmuneObjects() { |
| TimingLogger::ScopedTiming split(__FUNCTION__, GetTimings()); |
| for (auto& space : immune_spaces_.GetSpaces()) { |
| DCHECK(space->IsImageSpace() || space->IsZygoteSpace()); |
| accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap(); |
| VerifyGrayImmuneObjectsVisitor visitor(this); |
| live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()), |
| reinterpret_cast<uintptr_t>(space->Limit()), |
| [&visitor](mirror::Object* obj) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| // If an object is not gray, it should only have references to things in the immune spaces. |
| if (obj->GetReadBarrierState() != ReadBarrier::GrayState()) { |
| obj->VisitReferences</*kVisitNativeRoots=*/true, |
| kDefaultVerifyFlags, |
| kWithoutReadBarrier>(visitor, visitor); |
| } |
| }); |
| } |
| } |
| |
| class ConcurrentCopying::VerifyNoMissingCardMarkVisitor { |
| public: |
| VerifyNoMissingCardMarkVisitor(ConcurrentCopying* cc, ObjPtr<mirror::Object> holder) |
| : cc_(cc), |
| holder_(holder) {} |
| |
| void operator()(ObjPtr<mirror::Object> obj, |
| MemberOffset offset, |
| bool is_static ATTRIBUTE_UNUSED) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| if (offset.Uint32Value() != mirror::Object::ClassOffset().Uint32Value()) { |
| CheckReference(obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>( |
| offset), offset.Uint32Value()); |
| } |
| } |
| void operator()(ObjPtr<mirror::Class> klass, |
| ObjPtr<mirror::Reference> ref) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| CHECK(klass->IsTypeOfReferenceClass()); |
| this->operator()(ref, mirror::Reference::ReferentOffset(), false); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| CheckReference(root->AsMirrorPtr()); |
| } |
| |
| void CheckReference(mirror::Object* ref, int32_t offset = -1) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (ref != nullptr && cc_->region_space_->IsInNewlyAllocatedRegion(ref)) { |
| LOG(FATAL_WITHOUT_ABORT) |
| << holder_->PrettyTypeOf() << "(" << holder_.Ptr() << ") references object " |
| << ref->PrettyTypeOf() << "(" << ref << ") in newly allocated region at offset=" << offset; |
| LOG(FATAL_WITHOUT_ABORT) << "time=" << cc_->region_space_->Time(); |
| constexpr const char* kIndent = " "; |
| LOG(FATAL_WITHOUT_ABORT) << cc_->DumpReferenceInfo(holder_.Ptr(), "holder_", kIndent); |
| LOG(FATAL_WITHOUT_ABORT) << cc_->DumpReferenceInfo(ref, "ref", kIndent); |
| LOG(FATAL) << "Unexpected reference to newly allocated region."; |
| } |
| } |
| |
| private: |
| ConcurrentCopying* const cc_; |
| ObjPtr<mirror::Object> const holder_; |
| }; |
| |
| void ConcurrentCopying::VerifyNoMissingCardMarks() { |
| auto visitor = [&](mirror::Object* obj) |
| REQUIRES(Locks::mutator_lock_) |
| REQUIRES(!mark_stack_lock_) { |
| // Objects on clean cards should never have references to newly allocated regions. Note |
| // that aged cards are also not clean. |
| if (heap_->GetCardTable()->GetCard(obj) == gc::accounting::CardTable::kCardClean) { |
| VerifyNoMissingCardMarkVisitor internal_visitor(this, /*holder=*/ obj); |
| obj->VisitReferences</*kVisitNativeRoots=*/true, kVerifyNone, kWithoutReadBarrier>( |
| internal_visitor, internal_visitor); |
| } |
| }; |
| TimingLogger::ScopedTiming split(__FUNCTION__, GetTimings()); |
| region_space_->Walk(visitor); |
| { |
| ReaderMutexLock rmu(Thread::Current(), *Locks::heap_bitmap_lock_); |
| heap_->GetLiveBitmap()->Visit(visitor); |
| } |
| } |
| |
| // Switch threads that from from-space to to-space refs. Forward/mark the thread roots. |
| void ConcurrentCopying::FlipThreadRoots() { |
| TimingLogger::ScopedTiming split("FlipThreadRoots", GetTimings()); |
| if (kVerboseMode) { |
| LOG(INFO) << "time=" << region_space_->Time(); |
| region_space_->DumpNonFreeRegions(LOG_STREAM(INFO)); |
| } |
| Thread* self = Thread::Current(); |
| Locks::mutator_lock_->AssertNotHeld(self); |
| gc_barrier_->Init(self, 0); |
| ThreadFlipVisitor thread_flip_visitor(this, heap_->use_tlab_); |
| FlipCallback flip_callback(this); |
| |
| size_t barrier_count = Runtime::Current()->GetThreadList()->FlipThreadRoots( |
| &thread_flip_visitor, &flip_callback, this, GetHeap()->GetGcPauseListener()); |
| |
| { |
| ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun); |
| gc_barrier_->Increment(self, barrier_count); |
| } |
| is_asserting_to_space_invariant_ = true; |
| QuasiAtomic::ThreadFenceForConstructor(); |
| if (kVerboseMode) { |
| LOG(INFO) << "time=" << region_space_->Time(); |
| region_space_->DumpNonFreeRegions(LOG_STREAM(INFO)); |
| LOG(INFO) << "GC end of FlipThreadRoots"; |
| } |
| } |
| |
| template <bool kConcurrent> |
| class ConcurrentCopying::GrayImmuneObjectVisitor { |
| public: |
| explicit GrayImmuneObjectVisitor(Thread* self) : self_(self) {} |
| |
| ALWAYS_INLINE void operator()(mirror::Object* obj) const REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (kUseBakerReadBarrier && obj->GetReadBarrierState() == ReadBarrier::NonGrayState()) { |
| if (kConcurrent) { |
| Locks::mutator_lock_->AssertSharedHeld(self_); |
| obj->AtomicSetReadBarrierState(ReadBarrier::NonGrayState(), ReadBarrier::GrayState()); |
| // Mod union table VisitObjects may visit the same object multiple times so we can't check |
| // the result of the atomic set. |
| } else { |
| Locks::mutator_lock_->AssertExclusiveHeld(self_); |
| obj->SetReadBarrierState(ReadBarrier::GrayState()); |
| } |
| } |
| } |
| |
| static void Callback(mirror::Object* obj, void* arg) REQUIRES_SHARED(Locks::mutator_lock_) { |
| reinterpret_cast<GrayImmuneObjectVisitor<kConcurrent>*>(arg)->operator()(obj); |
| } |
| |
| private: |
| Thread* const self_; |
| }; |
| |
| void ConcurrentCopying::GrayAllDirtyImmuneObjects() { |
| TimingLogger::ScopedTiming split("GrayAllDirtyImmuneObjects", GetTimings()); |
| accounting::CardTable* const card_table = heap_->GetCardTable(); |
| Thread* const self = Thread::Current(); |
| using VisitorType = GrayImmuneObjectVisitor</* kIsConcurrent= */ true>; |
| VisitorType visitor(self); |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) { |
| DCHECK(space->IsImageSpace() || space->IsZygoteSpace()); |
| accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space); |
| // Mark all the objects on dirty cards since these may point to objects in other space. |
| // Once these are marked, the GC will eventually clear them later. |
| // Table is non null for boot image and zygote spaces. It is only null for application image |
| // spaces. |
| if (table != nullptr) { |
| table->ProcessCards(); |
| table->VisitObjects(&VisitorType::Callback, &visitor); |
| // Don't clear cards here since we need to rescan in the pause. If we cleared the cards here, |
| // there would be races with the mutator marking new cards. |
| } else { |
| // Keep cards aged if we don't have a mod-union table since we may need to scan them in future |
| // GCs. This case is for app images. |
| card_table->ModifyCardsAtomic( |
| space->Begin(), |
| space->End(), |
| [](uint8_t card) { |
| return (card != gc::accounting::CardTable::kCardClean) |
| ? gc::accounting::CardTable::kCardAged |
| : card; |
| }, |
| /* card modified visitor */ VoidFunctor()); |
| card_table->Scan</*kClearCard=*/ false>(space->GetMarkBitmap(), |
| space->Begin(), |
| space->End(), |
| visitor, |
| gc::accounting::CardTable::kCardAged); |
| } |
| } |
| } |
| |
| void ConcurrentCopying::GrayAllNewlyDirtyImmuneObjects() { |
| TimingLogger::ScopedTiming split("(Paused)GrayAllNewlyDirtyImmuneObjects", GetTimings()); |
| accounting::CardTable* const card_table = heap_->GetCardTable(); |
| using VisitorType = GrayImmuneObjectVisitor</* kIsConcurrent= */ false>; |
| Thread* const self = Thread::Current(); |
| VisitorType visitor(self); |
| WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_); |
| for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) { |
| DCHECK(space->IsImageSpace() || space->IsZygoteSpace()); |
| accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space); |
| |
| // Don't need to scan aged cards since we did these before the pause. Note that scanning cards |
| // also handles the mod-union table cards. |
| card_table->Scan</*kClearCard=*/ false>(space->GetMarkBitmap(), |
| space->Begin(), |
| space->End(), |
| visitor, |
| gc::accounting::CardTable::kCardDirty); |
| if (table != nullptr) { |
| // Add the cards to the mod-union table so that we can clear cards to save RAM. |
| table->ProcessCards(); |
| TimingLogger::ScopedTiming split2("(Paused)ClearCards", GetTimings()); |
| card_table->ClearCardRange(space->Begin(), |
| AlignDown(space->End(), accounting::CardTable::kCardSize)); |
| } |
| } |
| // Since all of the objects that may point to other spaces are gray, we can avoid all the read |
| // barriers in the immune spaces. |
| updated_all_immune_objects_.store(true, std::memory_order_relaxed); |
| } |
| |
| void ConcurrentCopying::SwapStacks() { |
| heap_->SwapStacks(); |
| } |
| |
| void ConcurrentCopying::RecordLiveStackFreezeSize(Thread* self) { |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| live_stack_freeze_size_ = heap_->GetLiveStack()->Size(); |
| } |
| |
| // Used to visit objects in the immune spaces. |
| inline void ConcurrentCopying::ScanImmuneObject(mirror::Object* obj) { |
| DCHECK(obj != nullptr); |
| DCHECK(immune_spaces_.ContainsObject(obj)); |
| // Update the fields without graying it or pushing it onto the mark stack. |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| // Young GC does not care about references to unevac space. It is safe to not gray these as |
| // long as scan immune objects happens after scanning the dirty cards. |
| Scan<true>(obj); |
| } else { |
| Scan<false>(obj); |
| } |
| } |
| |
| class ConcurrentCopying::ImmuneSpaceScanObjVisitor { |
| public: |
| explicit ImmuneSpaceScanObjVisitor(ConcurrentCopying* cc) |
| : collector_(cc) {} |
| |
| ALWAYS_INLINE void operator()(mirror::Object* obj) const REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) { |
| // Only need to scan gray objects. |
| if (obj->GetReadBarrierState() == ReadBarrier::GrayState()) { |
| collector_->ScanImmuneObject(obj); |
| // Done scanning the object, go back to black (non-gray). |
| bool success = obj->AtomicSetReadBarrierState(ReadBarrier::GrayState(), |
| ReadBarrier::NonGrayState()); |
| CHECK(success) |
| << Runtime::Current()->GetHeap()->GetVerification()->DumpObjectInfo(obj, "failed CAS"); |
| } |
| } else { |
| collector_->ScanImmuneObject(obj); |
| } |
| } |
| |
| static void Callback(mirror::Object* obj, void* arg) REQUIRES_SHARED(Locks::mutator_lock_) { |
| reinterpret_cast<ImmuneSpaceScanObjVisitor*>(arg)->operator()(obj); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| }; |
| |
| // Concurrently mark roots that are guarded by read barriers and process the mark stack. |
| void ConcurrentCopying::MarkingPhase() { |
| TimingLogger::ScopedTiming split("MarkingPhase", GetTimings()); |
| if (kVerboseMode) { |
| LOG(INFO) << "GC MarkingPhase"; |
| } |
| Thread* self = Thread::Current(); |
| if (kIsDebugBuild) { |
| MutexLock mu(self, *Locks::thread_list_lock_); |
| CHECK(weak_ref_access_enabled_); |
| } |
| |
| // Scan immune spaces. |
| // Update all the fields in the immune spaces first without graying the objects so that we |
| // minimize dirty pages in the immune spaces. Note mutators can concurrently access and gray some |
| // of the objects. |
| if (kUseBakerReadBarrier) { |
| gc_grays_immune_objects_ = false; |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| if (kVerboseMode) { |
| LOG(INFO) << "GC ScanCardsForSpace"; |
| } |
| TimingLogger::ScopedTiming split2("ScanCardsForSpace", GetTimings()); |
| WriterMutexLock rmu(Thread::Current(), *Locks::heap_bitmap_lock_); |
| CHECK(!done_scanning_.load(std::memory_order_relaxed)); |
| if (kIsDebugBuild) { |
| // Leave some time for mutators to race ahead to try and find races between the GC card |
| // scanning and mutators reading references. |
| usleep(10 * 1000); |
| } |
| for (space::ContinuousSpace* space : GetHeap()->GetContinuousSpaces()) { |
| if (space->IsImageSpace() || space->IsZygoteSpace()) { |
| // Image and zygote spaces are already handled since we gray the objects in the pause. |
| continue; |
| } |
| // Scan all of the objects on dirty cards in unevac from space, and non moving space. These |
| // are from previous GCs and may reference things in the from space. |
| // |
| // Note that we do not need to process the large-object space (the only discontinuous space) |
| // as it contains only large string objects and large primitive array objects, that have no |
| // reference to other objects, except their class. There is no need to scan these large |
| // objects, as the String class and the primitive array classes are expected to never move |
| // during a minor (young-generation) collection: |
| // - In the case where we run with a boot image, these classes are part of the image space, |
| // which is an immune space. |
| // - In the case where we run without a boot image, these classes are allocated in the |
| // non-moving space (see art::ClassLinker::InitWithoutImage). |
| Runtime::Current()->GetHeap()->GetCardTable()->Scan<false>( |
| space->GetMarkBitmap(), |
| space->Begin(), |
| space->End(), |
| [this, space](mirror::Object* obj) |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| // Don't push or gray unevac refs. |
| if (kIsDebugBuild && space == region_space_) { |
| // We may get unevac large objects. |
| if (!region_space_->IsInUnevacFromSpace(obj)) { |
| CHECK(region_space_bitmap_->Test(obj)); |
| region_space_->DumpRegionForObject(LOG_STREAM(FATAL_WITHOUT_ABORT), obj); |
| LOG(FATAL) << "Scanning " << obj << " not in unevac space"; |
| } |
| } |
| Scan<true>(obj); |
| }, |
| accounting::CardTable::kCardDirty - 1); |
| } |
| // Done scanning unevac space. |
| done_scanning_.store(true, std::memory_order_release); |
| if (kVerboseMode) { |
| LOG(INFO) << "GC end of ScanCardsForSpace"; |
| } |
| } |
| { |
| // For a sticky-bit collection, this phase needs to be after the card scanning since the |
| // mutator may read an unevac space object out of an image object. If the image object is no |
| // longer gray it will trigger a read barrier for the unevac space object. |
| TimingLogger::ScopedTiming split2("ScanImmuneSpaces", GetTimings()); |
| for (auto& space : immune_spaces_.GetSpaces()) { |
| DCHECK(space->IsImageSpace() || space->IsZygoteSpace()); |
| accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap(); |
| accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space); |
| ImmuneSpaceScanObjVisitor visitor(this); |
| if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects && table != nullptr) { |
| table->VisitObjects(ImmuneSpaceScanObjVisitor::Callback, &visitor); |
| } else { |
| // TODO: Scan only the aged cards. |
| live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()), |
| reinterpret_cast<uintptr_t>(space->Limit()), |
| visitor); |
| } |
| } |
| } |
| if (kUseBakerReadBarrier) { |
| // This release fence makes the field updates in the above loop visible before allowing mutator |
| // getting access to immune objects without graying it first. |
| updated_all_immune_objects_.store(true, std::memory_order_release); |
| // Now "un-gray" (conceptually blacken) immune objects concurrently accessed and grayed by |
| // mutators. We can't do this in the above loop because we would incorrectly disable the read |
| // barrier by un-graying (conceptually blackening) an object which may point to an unscanned, |
| // white object, breaking the to-space invariant (a mutator shall never observe a from-space |
| // (white) object). |
| // |
| // Make sure no mutators are in the middle of marking an immune object before un-graying |
| // (blackening) immune objects. |
| IssueEmptyCheckpoint(); |
| MutexLock mu(Thread::Current(), immune_gray_stack_lock_); |
| if (kVerboseMode) { |
| LOG(INFO) << "immune gray stack size=" << immune_gray_stack_.size(); |
| } |
| for (mirror::Object* obj : immune_gray_stack_) { |
| DCHECK_EQ(obj->GetReadBarrierState(), ReadBarrier::GrayState()); |
| bool success = obj->AtomicSetReadBarrierState(ReadBarrier::GrayState(), |
| ReadBarrier::NonGrayState()); |
| DCHECK(success); |
| } |
| immune_gray_stack_.clear(); |
| } |
| |
| { |
| TimingLogger::ScopedTiming split2("VisitConcurrentRoots", GetTimings()); |
| Runtime::Current()->VisitConcurrentRoots(this, kVisitRootFlagAllRoots); |
| } |
| { |
| // TODO: don't visit the transaction roots if it's not active. |
| TimingLogger::ScopedTiming split5("VisitNonThreadRoots", GetTimings()); |
| Runtime::Current()->VisitNonThreadRoots(this); |
| } |
| |
| { |
| TimingLogger::ScopedTiming split7("ProcessMarkStack", GetTimings()); |
| // We transition through three mark stack modes (thread-local, shared, GC-exclusive). The |
| // primary reasons are the fact that we need to use a checkpoint to process thread-local mark |
| // stacks, but after we disable weak refs accesses, we can't use a checkpoint due to a deadlock |
| // issue because running threads potentially blocking at WaitHoldingLocks, and that once we |
| // reach the point where we process weak references, we can avoid using a lock when accessing |
| // the GC mark stack, which makes mark stack processing more efficient. |
| |
| // Process the mark stack once in the thread local stack mode. This marks most of the live |
| // objects, aside from weak ref accesses with read barriers (Reference::GetReferent() and system |
| // weaks) that may happen concurrently while we processing the mark stack and newly mark/gray |
| // objects and push refs on the mark stack. |
| ProcessMarkStack(); |
| // Switch to the shared mark stack mode. That is, revoke and process thread-local mark stacks |
| // for the last time before transitioning to the shared mark stack mode, which would process new |
| // refs that may have been concurrently pushed onto the mark stack during the ProcessMarkStack() |
| // call above. At the same time, disable weak ref accesses using a per-thread flag. It's |
| // important to do these together in a single checkpoint so that we can ensure that mutators |
| // won't newly gray objects and push new refs onto the mark stack due to weak ref accesses and |
| // mutators safely transition to the shared mark stack mode (without leaving unprocessed refs on |
| // the thread-local mark stacks), without a race. This is why we use a thread-local weak ref |
| // access flag Thread::tls32_.weak_ref_access_enabled_ instead of the global ones. |
| SwitchToSharedMarkStackMode(); |
| CHECK(!self->GetWeakRefAccessEnabled()); |
| // Now that weak refs accesses are disabled, once we exhaust the shared mark stack again here |
| // (which may be non-empty if there were refs found on thread-local mark stacks during the above |
| // SwitchToSharedMarkStackMode() call), we won't have new refs to process, that is, mutators |
| // (via read barriers) have no way to produce any more refs to process. Marking converges once |
| // before we process weak refs below. |
| ProcessMarkStack(); |
| CheckEmptyMarkStack(); |
| // Switch to the GC exclusive mark stack mode so that we can process the mark stack without a |
| // lock from this point on. |
| SwitchToGcExclusiveMarkStackMode(); |
| CheckEmptyMarkStack(); |
| if (kVerboseMode) { |
| LOG(INFO) << "ProcessReferences"; |
| } |
| // Process weak references. This may produce new refs to process and have them processed via |
| // ProcessMarkStack (in the GC exclusive mark stack mode). |
| ProcessReferences(self); |
| CheckEmptyMarkStack(); |
| if (kVerboseMode) { |
| LOG(INFO) << "SweepSystemWeaks"; |
| } |
| SweepSystemWeaks(self); |
| if (kVerboseMode) { |
| LOG(INFO) << "SweepSystemWeaks done"; |
| } |
| // Process the mark stack here one last time because the above SweepSystemWeaks() call may have |
| // marked some objects (strings alive) as hash_set::Erase() can call the hash function for |
| // arbitrary elements in the weak intern table in InternTable::Table::SweepWeaks(). |
| ProcessMarkStack(); |
| CheckEmptyMarkStack(); |
| // Re-enable weak ref accesses. |
| ReenableWeakRefAccess(self); |
| // Free data for class loaders that we unloaded. |
| Runtime::Current()->GetClassLinker()->CleanupClassLoaders(); |
| // Marking is done. Disable marking. |
| DisableMarking(); |
| if (kUseBakerReadBarrier) { |
| ProcessFalseGrayStack(); |
| } |
| CheckEmptyMarkStack(); |
| } |
| |
| if (kIsDebugBuild) { |
| MutexLock mu(self, *Locks::thread_list_lock_); |
| CHECK(weak_ref_access_enabled_); |
| } |
| if (kVerboseMode) { |
| LOG(INFO) << "GC end of MarkingPhase"; |
| } |
| } |
| |
| void ConcurrentCopying::ReenableWeakRefAccess(Thread* self) { |
| if (kVerboseMode) { |
| LOG(INFO) << "ReenableWeakRefAccess"; |
| } |
| // Iterate all threads (don't need to or can't use a checkpoint) and re-enable weak ref access. |
| { |
| MutexLock mu(self, *Locks::thread_list_lock_); |
| weak_ref_access_enabled_ = true; // This is for new threads. |
| std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList(); |
| for (Thread* thread : thread_list) { |
| thread->SetWeakRefAccessEnabled(true); |
| } |
| } |
| // Unblock blocking threads. |
| GetHeap()->GetReferenceProcessor()->BroadcastForSlowPath(self); |
| Runtime::Current()->BroadcastForNewSystemWeaks(); |
| } |
| |
| class ConcurrentCopying::DisableMarkingCheckpoint : public Closure { |
| public: |
| explicit DisableMarkingCheckpoint(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) { |
| } |
| |
| void Run(Thread* thread) override NO_THREAD_SAFETY_ANALYSIS { |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* self = Thread::Current(); |
| DCHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc) |
| << thread->GetState() << " thread " << thread << " self " << self; |
| // Disable the thread-local is_gc_marking flag. |
| // Note a thread that has just started right before this checkpoint may have already this flag |
| // set to false, which is ok. |
| thread->SetIsGcMarkingAndUpdateEntrypoints(false); |
| // If thread is a running mutator, then act on behalf of the garbage collector. |
| // See the code in ThreadList::RunCheckpoint. |
| concurrent_copying_->GetBarrier().Pass(self); |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| class ConcurrentCopying::DisableMarkingCallback : public Closure { |
| public: |
| explicit DisableMarkingCallback(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) { |
| } |
| |
| void Run(Thread* self ATTRIBUTE_UNUSED) override REQUIRES(Locks::thread_list_lock_) { |
| // This needs to run under the thread_list_lock_ critical section in ThreadList::RunCheckpoint() |
| // to avoid a race with ThreadList::Register(). |
| CHECK(concurrent_copying_->is_marking_); |
| concurrent_copying_->is_marking_ = false; |
| if (kUseBakerReadBarrier && kGrayDirtyImmuneObjects) { |
| CHECK(concurrent_copying_->is_using_read_barrier_entrypoints_); |
| concurrent_copying_->is_using_read_barrier_entrypoints_ = false; |
| } else { |
| CHECK(!concurrent_copying_->is_using_read_barrier_entrypoints_); |
| } |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| void ConcurrentCopying::IssueDisableMarkingCheckpoint() { |
| Thread* self = Thread::Current(); |
| DisableMarkingCheckpoint check_point(this); |
| ThreadList* thread_list = Runtime::Current()->GetThreadList(); |
| gc_barrier_->Init(self, 0); |
| DisableMarkingCallback dmc(this); |
| size_t barrier_count = thread_list->RunCheckpoint(&check_point, &dmc); |
| // If there are no threads to wait which implies that all the checkpoint functions are finished, |
| // then no need to release the mutator lock. |
| if (barrier_count == 0) { |
| return; |
| } |
| // Release locks then wait for all mutator threads to pass the barrier. |
| Locks::mutator_lock_->SharedUnlock(self); |
| { |
| ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun); |
| gc_barrier_->Increment(self, barrier_count); |
| } |
| Locks::mutator_lock_->SharedLock(self); |
| } |
| |
| void ConcurrentCopying::DisableMarking() { |
| // Use a checkpoint to turn off the global is_marking and the thread-local is_gc_marking flags and |
| // to ensure no threads are still in the middle of a read barrier which may have a from-space ref |
| // cached in a local variable. |
| IssueDisableMarkingCheckpoint(); |
| if (kUseTableLookupReadBarrier) { |
| heap_->rb_table_->ClearAll(); |
| DCHECK(heap_->rb_table_->IsAllCleared()); |
| } |
| is_mark_stack_push_disallowed_.store(1, std::memory_order_seq_cst); |
| mark_stack_mode_.store(kMarkStackModeOff, std::memory_order_seq_cst); |
| } |
| |
| void ConcurrentCopying::PushOntoFalseGrayStack(Thread* const self, mirror::Object* ref) { |
| CHECK(kUseBakerReadBarrier); |
| DCHECK(ref != nullptr); |
| MutexLock mu(self, mark_stack_lock_); |
| false_gray_stack_.push_back(ref); |
| } |
| |
| void ConcurrentCopying::ProcessFalseGrayStack() { |
| CHECK(kUseBakerReadBarrier); |
| // Change the objects on the false gray stack from gray to non-gray (conceptually black). |
| MutexLock mu(Thread::Current(), mark_stack_lock_); |
| for (mirror::Object* obj : false_gray_stack_) { |
| DCHECK(IsMarked(obj)); |
| // The object could be non-gray (conceptually black) here if a thread got preempted after a |
| // success at the AtomicSetReadBarrierState in MarkNonMoving(), GC started marking through it |
| // (but not finished so still gray), the thread ran to register it onto the false gray stack, |
| // and then GC eventually marked it black (non-gray) after it finished scanning it. |
| if (obj->GetReadBarrierState() == ReadBarrier::GrayState()) { |
| bool success = obj->AtomicSetReadBarrierState(ReadBarrier::GrayState(), |
| ReadBarrier::NonGrayState()); |
| DCHECK(success); |
| } |
| } |
| false_gray_stack_.clear(); |
| } |
| |
| void ConcurrentCopying::IssueEmptyCheckpoint() { |
| Thread* self = Thread::Current(); |
| ThreadList* thread_list = Runtime::Current()->GetThreadList(); |
| // Release locks then wait for all mutator threads to pass the barrier. |
| Locks::mutator_lock_->SharedUnlock(self); |
| thread_list->RunEmptyCheckpoint(); |
| Locks::mutator_lock_->SharedLock(self); |
| } |
| |
| void ConcurrentCopying::ExpandGcMarkStack() { |
| DCHECK(gc_mark_stack_->IsFull()); |
| const size_t new_size = gc_mark_stack_->Capacity() * 2; |
| std::vector<StackReference<mirror::Object>> temp(gc_mark_stack_->Begin(), |
| gc_mark_stack_->End()); |
| gc_mark_stack_->Resize(new_size); |
| for (auto& ref : temp) { |
| gc_mark_stack_->PushBack(ref.AsMirrorPtr()); |
| } |
| DCHECK(!gc_mark_stack_->IsFull()); |
| } |
| |
| void ConcurrentCopying::PushOntoMarkStack(Thread* const self, mirror::Object* to_ref) { |
| CHECK_EQ(is_mark_stack_push_disallowed_.load(std::memory_order_relaxed), 0) |
| << " " << to_ref << " " << mirror::Object::PrettyTypeOf(to_ref); |
| CHECK(thread_running_gc_ != nullptr); |
| MarkStackMode mark_stack_mode = mark_stack_mode_.load(std::memory_order_relaxed); |
| if (LIKELY(mark_stack_mode == kMarkStackModeThreadLocal)) { |
| if (LIKELY(self == thread_running_gc_)) { |
| // If GC-running thread, use the GC mark stack instead of a thread-local mark stack. |
| CHECK(self->GetThreadLocalMarkStack() == nullptr); |
| if (UNLIKELY(gc_mark_stack_->IsFull())) { |
| ExpandGcMarkStack(); |
| } |
| gc_mark_stack_->PushBack(to_ref); |
| } else { |
| // Otherwise, use a thread-local mark stack. |
| accounting::AtomicStack<mirror::Object>* tl_mark_stack = self->GetThreadLocalMarkStack(); |
| if (UNLIKELY(tl_mark_stack == nullptr || tl_mark_stack->IsFull())) { |
| MutexLock mu(self, mark_stack_lock_); |
| // Get a new thread local mark stack. |
| accounting::AtomicStack<mirror::Object>* new_tl_mark_stack; |
| if (!pooled_mark_stacks_.empty()) { |
| // Use a pooled mark stack. |
| new_tl_mark_stack = pooled_mark_stacks_.back(); |
| pooled_mark_stacks_.pop_back(); |
| } else { |
| // None pooled. Create a new one. |
| new_tl_mark_stack = |
| accounting::AtomicStack<mirror::Object>::Create( |
| "thread local mark stack", 4 * KB, 4 * KB); |
| } |
| DCHECK(new_tl_mark_stack != nullptr); |
| DCHECK(new_tl_mark_stack->IsEmpty()); |
| new_tl_mark_stack->PushBack(to_ref); |
| self->SetThreadLocalMarkStack(new_tl_mark_stack); |
| if (tl_mark_stack != nullptr) { |
| // Store the old full stack into a vector. |
| revoked_mark_stacks_.push_back(tl_mark_stack); |
| } |
| } else { |
| tl_mark_stack->PushBack(to_ref); |
| } |
| } |
| } else if (mark_stack_mode == kMarkStackModeShared) { |
| // Access the shared GC mark stack with a lock. |
| MutexLock mu(self, mark_stack_lock_); |
| if (UNLIKELY(gc_mark_stack_->IsFull())) { |
| ExpandGcMarkStack(); |
| } |
| gc_mark_stack_->PushBack(to_ref); |
| } else { |
| CHECK_EQ(static_cast<uint32_t>(mark_stack_mode), |
| static_cast<uint32_t>(kMarkStackModeGcExclusive)) |
| << "ref=" << to_ref |
| << " self->gc_marking=" << self->GetIsGcMarking() |
| << " cc->is_marking=" << is_marking_; |
| CHECK(self == thread_running_gc_) |
| << "Only GC-running thread should access the mark stack " |
| << "in the GC exclusive mark stack mode"; |
| // Access the GC mark stack without a lock. |
| if (UNLIKELY(gc_mark_stack_->IsFull())) { |
| ExpandGcMarkStack(); |
| } |
| gc_mark_stack_->PushBack(to_ref); |
| } |
| } |
| |
| accounting::ObjectStack* ConcurrentCopying::GetAllocationStack() { |
| return heap_->allocation_stack_.get(); |
| } |
| |
| accounting::ObjectStack* ConcurrentCopying::GetLiveStack() { |
| return heap_->live_stack_.get(); |
| } |
| |
| // The following visitors are used to verify that there's no references to the from-space left after |
| // marking. |
| class ConcurrentCopying::VerifyNoFromSpaceRefsVisitor : public SingleRootVisitor { |
| public: |
| explicit VerifyNoFromSpaceRefsVisitor(ConcurrentCopying* collector) |
| : collector_(collector) {} |
| |
| void operator()(mirror::Object* ref, |
| MemberOffset offset = MemberOffset(0), |
| mirror::Object* holder = nullptr) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| if (ref == nullptr) { |
| // OK. |
| return; |
| } |
| collector_->AssertToSpaceInvariant(holder, offset, ref); |
| if (kUseBakerReadBarrier) { |
| CHECK_EQ(ref->GetReadBarrierState(), ReadBarrier::NonGrayState()) |
| << "Ref " << ref << " " << ref->PrettyTypeOf() << " has gray rb_state"; |
| } |
| } |
| |
| void VisitRoot(mirror::Object* root, const RootInfo& info ATTRIBUTE_UNUSED) |
| override REQUIRES_SHARED(Locks::mutator_lock_) { |
| DCHECK(root != nullptr); |
| operator()(root); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| }; |
| |
| class ConcurrentCopying::VerifyNoFromSpaceRefsFieldVisitor { |
| public: |
| explicit VerifyNoFromSpaceRefsFieldVisitor(ConcurrentCopying* collector) |
| : collector_(collector) {} |
| |
| void operator()(ObjPtr<mirror::Object> obj, |
| MemberOffset offset, |
| bool is_static ATTRIBUTE_UNUSED) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| mirror::Object* ref = |
| obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset); |
| VerifyNoFromSpaceRefsVisitor visitor(collector_); |
| visitor(ref, offset, obj.Ptr()); |
| } |
| void operator()(ObjPtr<mirror::Class> klass, |
| ObjPtr<mirror::Reference> ref) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| CHECK(klass->IsTypeOfReferenceClass()); |
| this->operator()(ObjPtr<mirror::Object>(ref), mirror::Reference::ReferentOffset(), false); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| VerifyNoFromSpaceRefsVisitor visitor(collector_); |
| visitor(root->AsMirrorPtr()); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| }; |
| |
| // Verify there's no from-space references left after the marking phase. |
| void ConcurrentCopying::VerifyNoFromSpaceReferences() { |
| Thread* self = Thread::Current(); |
| DCHECK(Locks::mutator_lock_->IsExclusiveHeld(self)); |
| // Verify all threads have is_gc_marking to be false |
| { |
| MutexLock mu(self, *Locks::thread_list_lock_); |
| std::list<Thread*> thread_list = Runtime::Current()->GetThreadList()->GetList(); |
| for (Thread* thread : thread_list) { |
| CHECK(!thread->GetIsGcMarking()); |
| } |
| } |
| |
| auto verify_no_from_space_refs_visitor = [&](mirror::Object* obj) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| CHECK(obj != nullptr); |
| space::RegionSpace* region_space = RegionSpace(); |
| CHECK(!region_space->IsInFromSpace(obj)) << "Scanning object " << obj << " in from space"; |
| VerifyNoFromSpaceRefsFieldVisitor visitor(this); |
| obj->VisitReferences</*kVisitNativeRoots=*/true, kDefaultVerifyFlags, kWithoutReadBarrier>( |
| visitor, |
| visitor); |
| if (kUseBakerReadBarrier) { |
| CHECK_EQ(obj->GetReadBarrierState(), ReadBarrier::NonGrayState()) |
| << "obj=" << obj << " has gray rb_state " << obj->GetReadBarrierState(); |
| } |
| }; |
| // Roots. |
| { |
| ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| VerifyNoFromSpaceRefsVisitor ref_visitor(this); |
| Runtime::Current()->VisitRoots(&ref_visitor); |
| } |
| // The to-space. |
| region_space_->WalkToSpace(verify_no_from_space_refs_visitor); |
| // Non-moving spaces. |
| { |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| heap_->GetMarkBitmap()->Visit(verify_no_from_space_refs_visitor); |
| } |
| // The alloc stack. |
| { |
| VerifyNoFromSpaceRefsVisitor ref_visitor(this); |
| for (auto* it = heap_->allocation_stack_->Begin(), *end = heap_->allocation_stack_->End(); |
| it < end; ++it) { |
| mirror::Object* const obj = it->AsMirrorPtr(); |
| if (obj != nullptr && obj->GetClass() != nullptr) { |
| // TODO: need to call this only if obj is alive? |
| ref_visitor(obj); |
| verify_no_from_space_refs_visitor(obj); |
| } |
| } |
| } |
| // TODO: LOS. But only refs in LOS are classes. |
| } |
| |
| // The following visitors are used to assert the to-space invariant. |
| class ConcurrentCopying::AssertToSpaceInvariantRefsVisitor { |
| public: |
| explicit AssertToSpaceInvariantRefsVisitor(ConcurrentCopying* collector) |
| : collector_(collector) {} |
| |
| void operator()(mirror::Object* ref) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| if (ref == nullptr) { |
| // OK. |
| return; |
| } |
| collector_->AssertToSpaceInvariant(nullptr, MemberOffset(0), ref); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| }; |
| |
| class ConcurrentCopying::AssertToSpaceInvariantFieldVisitor { |
| public: |
| explicit AssertToSpaceInvariantFieldVisitor(ConcurrentCopying* collector) |
| : collector_(collector) {} |
| |
| void operator()(ObjPtr<mirror::Object> obj, |
| MemberOffset offset, |
| bool is_static ATTRIBUTE_UNUSED) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| mirror::Object* ref = |
| obj->GetFieldObject<mirror::Object, kDefaultVerifyFlags, kWithoutReadBarrier>(offset); |
| AssertToSpaceInvariantRefsVisitor visitor(collector_); |
| visitor(ref); |
| } |
| void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref ATTRIBUTE_UNUSED) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| CHECK(klass->IsTypeOfReferenceClass()); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| AssertToSpaceInvariantRefsVisitor visitor(collector_); |
| visitor(root->AsMirrorPtr()); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| }; |
| |
| class ConcurrentCopying::RevokeThreadLocalMarkStackCheckpoint : public Closure { |
| public: |
| RevokeThreadLocalMarkStackCheckpoint(ConcurrentCopying* concurrent_copying, |
| bool disable_weak_ref_access) |
| : concurrent_copying_(concurrent_copying), |
| disable_weak_ref_access_(disable_weak_ref_access) { |
| } |
| |
| void Run(Thread* thread) override NO_THREAD_SAFETY_ANALYSIS { |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* self = Thread::Current(); |
| CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc) |
| << thread->GetState() << " thread " << thread << " self " << self; |
| // Revoke thread local mark stacks. |
| accounting::AtomicStack<mirror::Object>* tl_mark_stack = thread->GetThreadLocalMarkStack(); |
| if (tl_mark_stack != nullptr) { |
| MutexLock mu(self, concurrent_copying_->mark_stack_lock_); |
| concurrent_copying_->revoked_mark_stacks_.push_back(tl_mark_stack); |
| thread->SetThreadLocalMarkStack(nullptr); |
| } |
| // Disable weak ref access. |
| if (disable_weak_ref_access_) { |
| thread->SetWeakRefAccessEnabled(false); |
| } |
| // If thread is a running mutator, then act on behalf of the garbage collector. |
| // See the code in ThreadList::RunCheckpoint. |
| concurrent_copying_->GetBarrier().Pass(self); |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| const bool disable_weak_ref_access_; |
| }; |
| |
| void ConcurrentCopying::RevokeThreadLocalMarkStacks(bool disable_weak_ref_access, |
| Closure* checkpoint_callback) { |
| Thread* self = Thread::Current(); |
| RevokeThreadLocalMarkStackCheckpoint check_point(this, disable_weak_ref_access); |
| ThreadList* thread_list = Runtime::Current()->GetThreadList(); |
| gc_barrier_->Init(self, 0); |
| size_t barrier_count = thread_list->RunCheckpoint(&check_point, checkpoint_callback); |
| // If there are no threads to wait which implys that all the checkpoint functions are finished, |
| // then no need to release the mutator lock. |
| if (barrier_count == 0) { |
| return; |
| } |
| Locks::mutator_lock_->SharedUnlock(self); |
| { |
| ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun); |
| gc_barrier_->Increment(self, barrier_count); |
| } |
| Locks::mutator_lock_->SharedLock(self); |
| } |
| |
| void ConcurrentCopying::RevokeThreadLocalMarkStack(Thread* thread) { |
| Thread* self = Thread::Current(); |
| CHECK_EQ(self, thread); |
| accounting::AtomicStack<mirror::Object>* tl_mark_stack = thread->GetThreadLocalMarkStack(); |
| if (tl_mark_stack != nullptr) { |
| CHECK(is_marking_); |
| MutexLock mu(self, mark_stack_lock_); |
| revoked_mark_stacks_.push_back(tl_mark_stack); |
| thread->SetThreadLocalMarkStack(nullptr); |
| } |
| } |
| |
| void ConcurrentCopying::ProcessMarkStack() { |
| if (kVerboseMode) { |
| LOG(INFO) << "ProcessMarkStack. "; |
| } |
| bool empty_prev = false; |
| while (true) { |
| bool empty = ProcessMarkStackOnce(); |
| if (empty_prev && empty) { |
| // Saw empty mark stack for a second time, done. |
| break; |
| } |
| empty_prev = empty; |
| } |
| } |
| |
| bool ConcurrentCopying::ProcessMarkStackOnce() { |
| DCHECK(thread_running_gc_ != nullptr); |
| Thread* const self = Thread::Current(); |
| DCHECK(self == thread_running_gc_); |
| DCHECK(thread_running_gc_->GetThreadLocalMarkStack() == nullptr); |
| size_t count = 0; |
| MarkStackMode mark_stack_mode = mark_stack_mode_.load(std::memory_order_relaxed); |
| if (mark_stack_mode == kMarkStackModeThreadLocal) { |
| // Process the thread-local mark stacks and the GC mark stack. |
| count += ProcessThreadLocalMarkStacks(/* disable_weak_ref_access= */ false, |
| /* checkpoint_callback= */ nullptr); |
| while (!gc_mark_stack_->IsEmpty()) { |
| mirror::Object* to_ref = gc_mark_stack_->PopBack(); |
| ProcessMarkStackRef(to_ref); |
| ++count; |
| } |
| gc_mark_stack_->Reset(); |
| } else if (mark_stack_mode == kMarkStackModeShared) { |
| // Do an empty checkpoint to avoid a race with a mutator preempted in the middle of a read |
| // barrier but before pushing onto the mark stack. b/32508093. Note the weak ref access is |
| // disabled at this point. |
| IssueEmptyCheckpoint(); |
| // Process the shared GC mark stack with a lock. |
| { |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| CHECK(revoked_mark_stacks_.empty()); |
| } |
| while (true) { |
| std::vector<mirror::Object*> refs; |
| { |
| // Copy refs with lock. Note the number of refs should be small. |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| if (gc_mark_stack_->IsEmpty()) { |
| break; |
| } |
| for (StackReference<mirror::Object>* p = gc_mark_stack_->Begin(); |
| p != gc_mark_stack_->End(); ++p) { |
| refs.push_back(p->AsMirrorPtr()); |
| } |
| gc_mark_stack_->Reset(); |
| } |
| for (mirror::Object* ref : refs) { |
| ProcessMarkStackRef(ref); |
| ++count; |
| } |
| } |
| } else { |
| CHECK_EQ(static_cast<uint32_t>(mark_stack_mode), |
| static_cast<uint32_t>(kMarkStackModeGcExclusive)); |
| { |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| CHECK(revoked_mark_stacks_.empty()); |
| } |
| // Process the GC mark stack in the exclusive mode. No need to take the lock. |
| while (!gc_mark_stack_->IsEmpty()) { |
| mirror::Object* to_ref = gc_mark_stack_->PopBack(); |
| ProcessMarkStackRef(to_ref); |
| ++count; |
| } |
| gc_mark_stack_->Reset(); |
| } |
| |
| // Return true if the stack was empty. |
| return count == 0; |
| } |
| |
| size_t ConcurrentCopying::ProcessThreadLocalMarkStacks(bool disable_weak_ref_access, |
| Closure* checkpoint_callback) { |
| // Run a checkpoint to collect all thread local mark stacks and iterate over them all. |
| RevokeThreadLocalMarkStacks(disable_weak_ref_access, checkpoint_callback); |
| size_t count = 0; |
| std::vector<accounting::AtomicStack<mirror::Object>*> mark_stacks; |
| { |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| // Make a copy of the mark stack vector. |
| mark_stacks = revoked_mark_stacks_; |
| revoked_mark_stacks_.clear(); |
| } |
| for (accounting::AtomicStack<mirror::Object>* mark_stack : mark_stacks) { |
| for (StackReference<mirror::Object>* p = mark_stack->Begin(); p != mark_stack->End(); ++p) { |
| mirror::Object* to_ref = p->AsMirrorPtr(); |
| ProcessMarkStackRef(to_ref); |
| ++count; |
| } |
| { |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| if (pooled_mark_stacks_.size() >= kMarkStackPoolSize) { |
| // The pool has enough. Delete it. |
| delete mark_stack; |
| } else { |
| // Otherwise, put it into the pool for later reuse. |
| mark_stack->Reset(); |
| pooled_mark_stacks_.push_back(mark_stack); |
| } |
| } |
| } |
| return count; |
| } |
| |
| inline void ConcurrentCopying::ProcessMarkStackRef(mirror::Object* to_ref) { |
| DCHECK(!region_space_->IsInFromSpace(to_ref)); |
| space::RegionSpace::RegionType rtype = region_space_->GetRegionType(to_ref); |
| if (kUseBakerReadBarrier) { |
| DCHECK(to_ref->GetReadBarrierState() == ReadBarrier::GrayState()) |
| << " to_ref=" << to_ref |
| << " rb_state=" << to_ref->GetReadBarrierState() |
| << " is_marked=" << IsMarked(to_ref) |
| << " type=" << to_ref->PrettyTypeOf() |
| << " young_gen=" << std::boolalpha << young_gen_ << std::noboolalpha |
| << " space=" << heap_->DumpSpaceNameFromAddress(to_ref) |
| << " region_type=" << rtype |
| // TODO: Temporary; remove this when this is no longer needed (b/116087961). |
| << " runtime->sentinel=" << Runtime::Current()->GetSentinel().Read<kWithoutReadBarrier>(); |
| } |
| bool add_to_live_bytes = false; |
| // Invariant: There should be no object from a newly-allocated |
| // region (either large or non-large) on the mark stack. |
| DCHECK(!region_space_->IsInNewlyAllocatedRegion(to_ref)) << to_ref; |
| if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) { |
| // Mark the bitmap only in the GC thread here so that we don't need a CAS. |
| if (!kUseBakerReadBarrier || |
| !region_space_bitmap_->Set(to_ref)) { |
| // It may be already marked if we accidentally pushed the same object twice due to the racy |
| // bitmap read in MarkUnevacFromSpaceRegion. |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| CHECK(region_space_->IsLargeObject(to_ref)); |
| region_space_->ZeroLiveBytesForLargeObject(to_ref); |
| Scan<true>(to_ref); |
| } else { |
| Scan<false>(to_ref); |
| } |
| // Only add to the live bytes if the object was not already marked and we are not the young |
| // GC. |
| add_to_live_bytes = true; |
| } |
| } else { |
| if (kEnableGenerationalConcurrentCopyingCollection) { |
| if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) { |
| // Copied to to-space, set the bit so that the next GC can scan objects. |
| region_space_bitmap_->Set(to_ref); |
| } |
| } |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| Scan<true>(to_ref); |
| } else { |
| Scan<false>(to_ref); |
| } |
| } |
| if (kUseBakerReadBarrier) { |
| DCHECK(to_ref->GetReadBarrierState() == ReadBarrier::GrayState()) |
| << " to_ref=" << to_ref |
| << " rb_state=" << to_ref->GetReadBarrierState() |
| << " is_marked=" << IsMarked(to_ref) |
| << " type=" << to_ref->PrettyTypeOf() |
| << " young_gen=" << std::boolalpha << young_gen_ << std::noboolalpha |
| << " space=" << heap_->DumpSpaceNameFromAddress(to_ref) |
| << " region_type=" << rtype |
| // TODO: Temporary; remove this when this is no longer needed (b/116087961). |
| << " runtime->sentinel=" << Runtime::Current()->GetSentinel().Read<kWithoutReadBarrier>(); |
| } |
| #ifdef USE_BAKER_OR_BROOKS_READ_BARRIER |
| mirror::Object* referent = nullptr; |
| if (UNLIKELY((to_ref->GetClass<kVerifyNone, kWithoutReadBarrier>()->IsTypeOfReferenceClass() && |
| (referent = to_ref->AsReference()->GetReferent<kWithoutReadBarrier>()) != nullptr && |
| !IsInToSpace(referent)))) { |
| // Leave this reference gray in the queue so that GetReferent() will trigger a read barrier. We |
| // will change it to non-gray later in ReferenceQueue::DisableReadBarrierForReference. |
| DCHECK(to_ref->AsReference()->GetPendingNext() != nullptr) |
| << "Left unenqueued ref gray " << to_ref; |
| } else { |
| // We may occasionally leave a reference non-gray in the queue if its referent happens to be |
| // concurrently marked after the Scan() call above has enqueued the Reference, in which case the |
| // above IsInToSpace() evaluates to true and we change the color from gray to non-gray here in |
| // this else block. |
| if (kUseBakerReadBarrier) { |
| bool success = to_ref->AtomicSetReadBarrierState<std::memory_order_release>( |
| ReadBarrier::GrayState(), |
| ReadBarrier::NonGrayState()); |
| DCHECK(success) << "Must succeed as we won the race."; |
| } |
| } |
| #else |
| DCHECK(!kUseBakerReadBarrier); |
| #endif |
| |
| if (add_to_live_bytes) { |
| // Add to the live bytes per unevacuated from-space. Note this code is always run by the |
| // GC-running thread (no synchronization required). |
| DCHECK(region_space_bitmap_->Test(to_ref)); |
| size_t obj_size = to_ref->SizeOf<kDefaultVerifyFlags>(); |
| size_t alloc_size = RoundUp(obj_size, space::RegionSpace::kAlignment); |
| region_space_->AddLiveBytes(to_ref, alloc_size); |
| } |
| if (ReadBarrier::kEnableToSpaceInvariantChecks) { |
| CHECK(to_ref != nullptr); |
| space::RegionSpace* region_space = RegionSpace(); |
| CHECK(!region_space->IsInFromSpace(to_ref)) << "Scanning object " << to_ref << " in from space"; |
| AssertToSpaceInvariant(nullptr, MemberOffset(0), to_ref); |
| AssertToSpaceInvariantFieldVisitor visitor(this); |
| to_ref->VisitReferences</*kVisitNativeRoots=*/true, kDefaultVerifyFlags, kWithoutReadBarrier>( |
| visitor, |
| visitor); |
| } |
| } |
| |
| class ConcurrentCopying::DisableWeakRefAccessCallback : public Closure { |
| public: |
| explicit DisableWeakRefAccessCallback(ConcurrentCopying* concurrent_copying) |
| : concurrent_copying_(concurrent_copying) { |
| } |
| |
| void Run(Thread* self ATTRIBUTE_UNUSED) override REQUIRES(Locks::thread_list_lock_) { |
| // This needs to run under the thread_list_lock_ critical section in ThreadList::RunCheckpoint() |
| // to avoid a deadlock b/31500969. |
| CHECK(concurrent_copying_->weak_ref_access_enabled_); |
| concurrent_copying_->weak_ref_access_enabled_ = false; |
| } |
| |
| private: |
| ConcurrentCopying* const concurrent_copying_; |
| }; |
| |
| void ConcurrentCopying::SwitchToSharedMarkStackMode() { |
| Thread* self = Thread::Current(); |
| DCHECK(thread_running_gc_ != nullptr); |
| DCHECK(self == thread_running_gc_); |
| DCHECK(thread_running_gc_->GetThreadLocalMarkStack() == nullptr); |
| MarkStackMode before_mark_stack_mode = mark_stack_mode_.load(std::memory_order_relaxed); |
| CHECK_EQ(static_cast<uint32_t>(before_mark_stack_mode), |
| static_cast<uint32_t>(kMarkStackModeThreadLocal)); |
| mark_stack_mode_.store(kMarkStackModeShared, std::memory_order_relaxed); |
| DisableWeakRefAccessCallback dwrac(this); |
| // Process the thread local mark stacks one last time after switching to the shared mark stack |
| // mode and disable weak ref accesses. |
| ProcessThreadLocalMarkStacks(/* disable_weak_ref_access= */ true, &dwrac); |
| if (kVerboseMode) { |
| LOG(INFO) << "Switched to shared mark stack mode and disabled weak ref access"; |
| } |
| } |
| |
| void ConcurrentCopying::SwitchToGcExclusiveMarkStackMode() { |
| Thread* self = Thread::Current(); |
| DCHECK(thread_running_gc_ != nullptr); |
| DCHECK(self == thread_running_gc_); |
| DCHECK(thread_running_gc_->GetThreadLocalMarkStack() == nullptr); |
| MarkStackMode before_mark_stack_mode = mark_stack_mode_.load(std::memory_order_relaxed); |
| CHECK_EQ(static_cast<uint32_t>(before_mark_stack_mode), |
| static_cast<uint32_t>(kMarkStackModeShared)); |
| mark_stack_mode_.store(kMarkStackModeGcExclusive, std::memory_order_relaxed); |
| QuasiAtomic::ThreadFenceForConstructor(); |
| if (kVerboseMode) { |
| LOG(INFO) << "Switched to GC exclusive mark stack mode"; |
| } |
| } |
| |
| void ConcurrentCopying::CheckEmptyMarkStack() { |
| Thread* self = Thread::Current(); |
| DCHECK(thread_running_gc_ != nullptr); |
| DCHECK(self == thread_running_gc_); |
| DCHECK(thread_running_gc_->GetThreadLocalMarkStack() == nullptr); |
| MarkStackMode mark_stack_mode = mark_stack_mode_.load(std::memory_order_relaxed); |
| if (mark_stack_mode == kMarkStackModeThreadLocal) { |
| // Thread-local mark stack mode. |
| RevokeThreadLocalMarkStacks(false, nullptr); |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| if (!revoked_mark_stacks_.empty()) { |
| for (accounting::AtomicStack<mirror::Object>* mark_stack : revoked_mark_stacks_) { |
| while (!mark_stack->IsEmpty()) { |
| mirror::Object* obj = mark_stack->PopBack(); |
| if (kUseBakerReadBarrier) { |
| uint32_t rb_state = obj->GetReadBarrierState(); |
| LOG(INFO) << "On mark queue : " << obj << " " << obj->PrettyTypeOf() << " rb_state=" |
| << rb_state << " is_marked=" << IsMarked(obj); |
| } else { |
| LOG(INFO) << "On mark queue : " << obj << " " << obj->PrettyTypeOf() |
| << " is_marked=" << IsMarked(obj); |
| } |
| } |
| } |
| LOG(FATAL) << "mark stack is not empty"; |
| } |
| } else { |
| // Shared, GC-exclusive, or off. |
| MutexLock mu(thread_running_gc_, mark_stack_lock_); |
| CHECK(gc_mark_stack_->IsEmpty()); |
| CHECK(revoked_mark_stacks_.empty()); |
| } |
| } |
| |
| void ConcurrentCopying::SweepSystemWeaks(Thread* self) { |
| TimingLogger::ScopedTiming split("SweepSystemWeaks", GetTimings()); |
| ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| Runtime::Current()->SweepSystemWeaks(this); |
| } |
| |
| void ConcurrentCopying::Sweep(bool swap_bitmaps) { |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| // Only sweep objects on the live stack. |
| SweepArray(heap_->GetLiveStack(), /* swap_bitmaps= */ false); |
| } else { |
| { |
| TimingLogger::ScopedTiming t("MarkStackAsLive", GetTimings()); |
| accounting::ObjectStack* live_stack = heap_->GetLiveStack(); |
| if (kEnableFromSpaceAccountingCheck) { |
| // Ensure that nobody inserted items in the live stack after we swapped the stacks. |
| CHECK_GE(live_stack_freeze_size_, live_stack->Size()); |
| } |
| heap_->MarkAllocStackAsLive(live_stack); |
| live_stack->Reset(); |
| } |
| CheckEmptyMarkStack(); |
| TimingLogger::ScopedTiming split("Sweep", GetTimings()); |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if (space->IsContinuousMemMapAllocSpace()) { |
| space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace(); |
| if (space == region_space_ || immune_spaces_.ContainsSpace(space)) { |
| continue; |
| } |
| TimingLogger::ScopedTiming split2( |
| alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepAllocSpace", GetTimings()); |
| RecordFree(alloc_space->Sweep(swap_bitmaps)); |
| } |
| } |
| SweepLargeObjects(swap_bitmaps); |
| } |
| } |
| |
| // Copied and adapted from MarkSweep::SweepArray. |
| void ConcurrentCopying::SweepArray(accounting::ObjectStack* allocations, bool swap_bitmaps) { |
| // This method is only used when Generational CC collection is enabled. |
| DCHECK(kEnableGenerationalConcurrentCopyingCollection); |
| CheckEmptyMarkStack(); |
| TimingLogger::ScopedTiming t("SweepArray", GetTimings()); |
| Thread* self = Thread::Current(); |
| mirror::Object** chunk_free_buffer = reinterpret_cast<mirror::Object**>( |
| sweep_array_free_buffer_mem_map_.BaseBegin()); |
| size_t chunk_free_pos = 0; |
| ObjectBytePair freed; |
| ObjectBytePair freed_los; |
| // How many objects are left in the array, modified after each space is swept. |
| StackReference<mirror::Object>* objects = allocations->Begin(); |
| size_t count = allocations->Size(); |
| // Start by sweeping the continuous spaces. |
| for (space::ContinuousSpace* space : heap_->GetContinuousSpaces()) { |
| if (!space->IsAllocSpace() || |
| space == region_space_ || |
| immune_spaces_.ContainsSpace(space) || |
| space->GetLiveBitmap() == nullptr) { |
| continue; |
| } |
| space::AllocSpace* alloc_space = space->AsAllocSpace(); |
| accounting::ContinuousSpaceBitmap* live_bitmap = space->GetLiveBitmap(); |
| accounting::ContinuousSpaceBitmap* mark_bitmap = space->GetMarkBitmap(); |
| if (swap_bitmaps) { |
| std::swap(live_bitmap, mark_bitmap); |
| } |
| StackReference<mirror::Object>* out = objects; |
| for (size_t i = 0; i < count; ++i) { |
| mirror::Object* const obj = objects[i].AsMirrorPtr(); |
| if (kUseThreadLocalAllocationStack && obj == nullptr) { |
| continue; |
| } |
| if (space->HasAddress(obj)) { |
| // This object is in the space, remove it from the array and add it to the sweep buffer |
| // if needed. |
| if (!mark_bitmap->Test(obj)) { |
| if (chunk_free_pos >= kSweepArrayChunkFreeSize) { |
| TimingLogger::ScopedTiming t2("FreeList", GetTimings()); |
| freed.objects += chunk_free_pos; |
| freed.bytes += alloc_space->FreeList(self, chunk_free_pos, chunk_free_buffer); |
| chunk_free_pos = 0; |
| } |
| chunk_free_buffer[chunk_free_pos++] = obj; |
| } |
| } else { |
| (out++)->Assign(obj); |
| } |
| } |
| if (chunk_free_pos > 0) { |
| TimingLogger::ScopedTiming t2("FreeList", GetTimings()); |
| freed.objects += chunk_free_pos; |
| freed.bytes += alloc_space->FreeList(self, chunk_free_pos, chunk_free_buffer); |
| chunk_free_pos = 0; |
| } |
| // All of the references which space contained are no longer in the allocation stack, update |
| // the count. |
| count = out - objects; |
| } |
| // Handle the large object space. |
| space::LargeObjectSpace* large_object_space = GetHeap()->GetLargeObjectsSpace(); |
| if (large_object_space != nullptr) { |
| accounting::LargeObjectBitmap* large_live_objects = large_object_space->GetLiveBitmap(); |
| accounting::LargeObjectBitmap* large_mark_objects = large_object_space->GetMarkBitmap(); |
| if (swap_bitmaps) { |
| std::swap(large_live_objects, large_mark_objects); |
| } |
| for (size_t i = 0; i < count; ++i) { |
| mirror::Object* const obj = objects[i].AsMirrorPtr(); |
| // Handle large objects. |
| if (kUseThreadLocalAllocationStack && obj == nullptr) { |
| continue; |
| } |
| if (!large_mark_objects->Test(obj)) { |
| ++freed_los.objects; |
| freed_los.bytes += large_object_space->Free(self, obj); |
| } |
| } |
| } |
| { |
| TimingLogger::ScopedTiming t2("RecordFree", GetTimings()); |
| RecordFree(freed); |
| RecordFreeLOS(freed_los); |
| t2.NewTiming("ResetStack"); |
| allocations->Reset(); |
| } |
| sweep_array_free_buffer_mem_map_.MadviseDontNeedAndZero(); |
| } |
| |
| void ConcurrentCopying::MarkZygoteLargeObjects() { |
| TimingLogger::ScopedTiming split(__FUNCTION__, GetTimings()); |
| Thread* const self = Thread::Current(); |
| WriterMutexLock rmu(self, *Locks::heap_bitmap_lock_); |
| space::LargeObjectSpace* const los = heap_->GetLargeObjectsSpace(); |
| if (los != nullptr) { |
| // Pick the current live bitmap (mark bitmap if swapped). |
| accounting::LargeObjectBitmap* const live_bitmap = los->GetLiveBitmap(); |
| accounting::LargeObjectBitmap* const mark_bitmap = los->GetMarkBitmap(); |
| // Walk through all of the objects and explicitly mark the zygote ones so they don't get swept. |
| std::pair<uint8_t*, uint8_t*> range = los->GetBeginEndAtomic(); |
| live_bitmap->VisitMarkedRange(reinterpret_cast<uintptr_t>(range.first), |
| reinterpret_cast<uintptr_t>(range.second), |
| [mark_bitmap, los, self](mirror::Object* obj) |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (los->IsZygoteLargeObject(self, obj)) { |
| mark_bitmap->Set(obj); |
| } |
| }); |
| } |
| } |
| |
| void ConcurrentCopying::SweepLargeObjects(bool swap_bitmaps) { |
| TimingLogger::ScopedTiming split("SweepLargeObjects", GetTimings()); |
| if (heap_->GetLargeObjectsSpace() != nullptr) { |
| RecordFreeLOS(heap_->GetLargeObjectsSpace()->Sweep(swap_bitmaps)); |
| } |
| } |
| |
| void ConcurrentCopying::ReclaimPhase() { |
| TimingLogger::ScopedTiming split("ReclaimPhase", GetTimings()); |
| if (kVerboseMode) { |
| LOG(INFO) << "GC ReclaimPhase"; |
| } |
| Thread* self = Thread::Current(); |
| |
| { |
| // Double-check that the mark stack is empty. |
| // Note: need to set this after VerifyNoFromSpaceRef(). |
| is_asserting_to_space_invariant_ = false; |
| QuasiAtomic::ThreadFenceForConstructor(); |
| if (kVerboseMode) { |
| LOG(INFO) << "Issue an empty check point. "; |
| } |
| IssueEmptyCheckpoint(); |
| // Disable the check. |
| is_mark_stack_push_disallowed_.store(0, std::memory_order_seq_cst); |
| if (kUseBakerReadBarrier) { |
| updated_all_immune_objects_.store(false, std::memory_order_seq_cst); |
| } |
| CheckEmptyMarkStack(); |
| } |
| |
| { |
| // Record freed objects. |
| TimingLogger::ScopedTiming split2("RecordFree", GetTimings()); |
| // Don't include thread-locals that are in the to-space. |
| const uint64_t from_bytes = region_space_->GetBytesAllocatedInFromSpace(); |
| const uint64_t from_objects = region_space_->GetObjectsAllocatedInFromSpace(); |
| const uint64_t unevac_from_bytes = region_space_->GetBytesAllocatedInUnevacFromSpace(); |
| const uint64_t unevac_from_objects = region_space_->GetObjectsAllocatedInUnevacFromSpace(); |
| uint64_t to_bytes = bytes_moved_.load(std::memory_order_relaxed) + bytes_moved_gc_thread_; |
| cumulative_bytes_moved_.fetch_add(to_bytes, std::memory_order_relaxed); |
| uint64_t to_objects = objects_moved_.load(std::memory_order_relaxed) + objects_moved_gc_thread_; |
| cumulative_objects_moved_.fetch_add(to_objects, std::memory_order_relaxed); |
| if (kEnableFromSpaceAccountingCheck) { |
| CHECK_EQ(from_space_num_objects_at_first_pause_, from_objects + unevac_from_objects); |
| CHECK_EQ(from_space_num_bytes_at_first_pause_, from_bytes + unevac_from_bytes); |
| } |
| CHECK_LE(to_objects, from_objects); |
| CHECK_LE(to_bytes, from_bytes); |
| if (from_bytes > 0) { |
| copied_live_bytes_ratio_sum_ += static_cast<float>(to_bytes) / from_bytes; |
| gc_count_++; |
| } |
| |
| // Cleared bytes and objects, populated by the call to RegionSpace::ClearFromSpace below. |
| uint64_t cleared_bytes; |
| uint64_t cleared_objects; |
| { |
| TimingLogger::ScopedTiming split4("ClearFromSpace", GetTimings()); |
| region_space_->ClearFromSpace(&cleared_bytes, &cleared_objects); |
| // `cleared_bytes` and `cleared_objects` may be greater than the from space equivalents since |
| // RegionSpace::ClearFromSpace may clear empty unevac regions. |
| CHECK_GE(cleared_bytes, from_bytes); |
| CHECK_GE(cleared_objects, from_objects); |
| } |
| int64_t freed_bytes = cleared_bytes - to_bytes; |
| int64_t freed_objects = cleared_objects - to_objects; |
| if (kVerboseMode) { |
| LOG(INFO) << "RecordFree:" |
| << " from_bytes=" << from_bytes << " from_objects=" << from_objects |
| << " unevac_from_bytes=" << unevac_from_bytes |
| << " unevac_from_objects=" << unevac_from_objects |
| << " to_bytes=" << to_bytes << " to_objects=" << to_objects |
| << " freed_bytes=" << freed_bytes << " freed_objects=" << freed_objects |
| << " from_space size=" << region_space_->FromSpaceSize() |
| << " unevac_from_space size=" << region_space_->UnevacFromSpaceSize() |
| << " to_space size=" << region_space_->ToSpaceSize(); |
| LOG(INFO) << "(before) num_bytes_allocated=" |
| << heap_->num_bytes_allocated_.load(); |
| } |
| RecordFree(ObjectBytePair(freed_objects, freed_bytes)); |
| if (kVerboseMode) { |
| LOG(INFO) << "(after) num_bytes_allocated=" |
| << heap_->num_bytes_allocated_.load(); |
| } |
| } |
| |
| { |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| Sweep(/* swap_bitmaps= */ false); |
| SwapBitmaps(); |
| heap_->UnBindBitmaps(); |
| |
| // The bitmap was cleared at the start of the GC, there is nothing we need to do here. |
| DCHECK(region_space_bitmap_ != nullptr); |
| region_space_bitmap_ = nullptr; |
| } |
| |
| CheckEmptyMarkStack(); |
| |
| if (kVerboseMode) { |
| LOG(INFO) << "GC end of ReclaimPhase"; |
| } |
| } |
| |
| std::string ConcurrentCopying::DumpReferenceInfo(mirror::Object* ref, |
| const char* ref_name, |
| const char* indent) { |
| std::ostringstream oss; |
| oss << indent << heap_->GetVerification()->DumpObjectInfo(ref, ref_name) << '\n'; |
| if (ref != nullptr) { |
| if (kUseBakerReadBarrier) { |
| oss << indent << ref_name << "->GetMarkBit()=" << ref->GetMarkBit() << '\n'; |
| oss << indent << ref_name << "->GetReadBarrierState()=" << ref->GetReadBarrierState() << '\n'; |
| } |
| } |
| if (region_space_->HasAddress(ref)) { |
| oss << indent << "Region containing " << ref_name << ":" << '\n'; |
| region_space_->DumpRegionForObject(oss, ref); |
| if (region_space_bitmap_ != nullptr) { |
| oss << indent << "region_space_bitmap_->Test(" << ref_name << ")=" |
| << std::boolalpha << region_space_bitmap_->Test(ref) << std::noboolalpha; |
| } |
| } |
| return oss.str(); |
| } |
| |
| std::string ConcurrentCopying::DumpHeapReference(mirror::Object* obj, |
| MemberOffset offset, |
| mirror::Object* ref) { |
| std::ostringstream oss; |
| constexpr const char* kIndent = " "; |
| oss << kIndent << "Invalid reference: ref=" << ref |
| << " referenced from: object=" << obj << " offset= " << offset << '\n'; |
| // Information about `obj`. |
| oss << DumpReferenceInfo(obj, "obj", kIndent) << '\n'; |
| // Information about `ref`. |
| oss << DumpReferenceInfo(ref, "ref", kIndent); |
| return oss.str(); |
| } |
| |
| void ConcurrentCopying::AssertToSpaceInvariant(mirror::Object* obj, |
| MemberOffset offset, |
| mirror::Object* ref) { |
| CHECK_EQ(heap_->collector_type_, kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_); |
| if (is_asserting_to_space_invariant_) { |
| if (region_space_->HasAddress(ref)) { |
| // Check to-space invariant in region space (moving space). |
| using RegionType = space::RegionSpace::RegionType; |
| space::RegionSpace::RegionType type = region_space_->GetRegionTypeUnsafe(ref); |
| if (type == RegionType::kRegionTypeToSpace) { |
| // OK. |
| return; |
| } else if (type == RegionType::kRegionTypeUnevacFromSpace) { |
| if (!IsMarkedInUnevacFromSpace(ref)) { |
| LOG(FATAL_WITHOUT_ABORT) << "Found unmarked reference in unevac from-space:"; |
| // Remove memory protection from the region space and log debugging information. |
| region_space_->Unprotect(); |
| LOG(FATAL_WITHOUT_ABORT) << DumpHeapReference(obj, offset, ref); |
| Thread::Current()->DumpJavaStack(LOG_STREAM(FATAL_WITHOUT_ABORT)); |
| } |
| CHECK(IsMarkedInUnevacFromSpace(ref)) << ref; |
| } else { |
| // Not OK: either a from-space ref or a reference in an unused region. |
| if (type == RegionType::kRegionTypeFromSpace) { |
| LOG(FATAL_WITHOUT_ABORT) << "Found from-space reference:"; |
| } else { |
| LOG(FATAL_WITHOUT_ABORT) << "Found reference in region with type " << type << ":"; |
| } |
| // Remove memory protection from the region space and log debugging information. |
| region_space_->Unprotect(); |
| LOG(FATAL_WITHOUT_ABORT) << DumpHeapReference(obj, offset, ref); |
| if (obj != nullptr) { |
| LogFromSpaceRefHolder(obj, offset); |
| LOG(FATAL_WITHOUT_ABORT) << "UNEVAC " << region_space_->IsInUnevacFromSpace(obj) << " " |
| << obj << " " << obj->GetMarkBit(); |
| if (region_space_->HasAddress(obj)) { |
| region_space_->DumpRegionForObject(LOG_STREAM(FATAL_WITHOUT_ABORT), obj); |
| } |
| LOG(FATAL_WITHOUT_ABORT) << "CARD " << static_cast<size_t>( |
| *Runtime::Current()->GetHeap()->GetCardTable()->CardFromAddr( |
| reinterpret_cast<uint8_t*>(obj))); |
| if (region_space_->HasAddress(obj)) { |
| LOG(FATAL_WITHOUT_ABORT) << "BITMAP " << region_space_bitmap_->Test(obj); |
| } else { |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(obj); |
| if (mark_bitmap != nullptr) { |
| LOG(FATAL_WITHOUT_ABORT) << "BITMAP " << mark_bitmap->Test(obj); |
| } else { |
| accounting::LargeObjectBitmap* los_bitmap = |
| heap_mark_bitmap_->GetLargeObjectBitmap(obj); |
| LOG(FATAL_WITHOUT_ABORT) << "BITMAP " << los_bitmap->Test(obj); |
| } |
| } |
| } |
| ref->GetLockWord(false).Dump(LOG_STREAM(FATAL_WITHOUT_ABORT)); |
| LOG(FATAL_WITHOUT_ABORT) << "Non-free regions:"; |
| region_space_->DumpNonFreeRegions(LOG_STREAM(FATAL_WITHOUT_ABORT)); |
| PrintFileToLog("/proc/self/maps", LogSeverity::FATAL_WITHOUT_ABORT); |
| MemMap::DumpMaps(LOG_STREAM(FATAL_WITHOUT_ABORT), /* terse= */ true); |
| LOG(FATAL) << "Invalid reference " << ref |
| << " referenced from object " << obj << " at offset " << offset; |
| } |
| } else { |
| // Check to-space invariant in non-moving space. |
| AssertToSpaceInvariantInNonMovingSpace(obj, ref); |
| } |
| } |
| } |
| |
| class RootPrinter { |
| public: |
| RootPrinter() { } |
| |
| template <class MirrorType> |
| ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| template <class MirrorType> |
| void VisitRoot(mirror::Object** root) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| LOG(FATAL_WITHOUT_ABORT) << "root=" << root << " ref=" << *root; |
| } |
| |
| template <class MirrorType> |
| void VisitRoot(mirror::CompressedReference<MirrorType>* root) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| LOG(FATAL_WITHOUT_ABORT) << "root=" << root << " ref=" << root->AsMirrorPtr(); |
| } |
| }; |
| |
| std::string ConcurrentCopying::DumpGcRoot(mirror::Object* ref) { |
| std::ostringstream oss; |
| constexpr const char* kIndent = " "; |
| oss << kIndent << "Invalid GC root: ref=" << ref << '\n'; |
| // Information about `ref`. |
| oss << DumpReferenceInfo(ref, "ref", kIndent); |
| return oss.str(); |
| } |
| |
| void ConcurrentCopying::AssertToSpaceInvariant(GcRootSource* gc_root_source, |
| mirror::Object* ref) { |
| CHECK_EQ(heap_->collector_type_, kCollectorTypeCC) << static_cast<size_t>(heap_->collector_type_); |
| if (is_asserting_to_space_invariant_) { |
| if (region_space_->HasAddress(ref)) { |
| // Check to-space invariant in region space (moving space). |
| using RegionType = space::RegionSpace::RegionType; |
| space::RegionSpace::RegionType type = region_space_->GetRegionTypeUnsafe(ref); |
| if (type == RegionType::kRegionTypeToSpace) { |
| // OK. |
| return; |
| } else if (type == RegionType::kRegionTypeUnevacFromSpace) { |
| if (!IsMarkedInUnevacFromSpace(ref)) { |
| LOG(FATAL_WITHOUT_ABORT) << "Found unmarked reference in unevac from-space:"; |
| // Remove memory protection from the region space and log debugging information. |
| region_space_->Unprotect(); |
| LOG(FATAL_WITHOUT_ABORT) << DumpGcRoot(ref); |
| } |
| CHECK(IsMarkedInUnevacFromSpace(ref)) << ref; |
| } else { |
| // Not OK: either a from-space ref or a reference in an unused region. |
| if (type == RegionType::kRegionTypeFromSpace) { |
| LOG(FATAL_WITHOUT_ABORT) << "Found from-space reference:"; |
| } else { |
| LOG(FATAL_WITHOUT_ABORT) << "Found reference in region with type " << type << ":"; |
| } |
| // Remove memory protection from the region space and log debugging information. |
| region_space_->Unprotect(); |
| LOG(FATAL_WITHOUT_ABORT) << DumpGcRoot(ref); |
| if (gc_root_source == nullptr) { |
| // No info. |
| } else if (gc_root_source->HasArtField()) { |
| ArtField* field = gc_root_source->GetArtField(); |
| LOG(FATAL_WITHOUT_ABORT) << "gc root in field " << field << " " |
| << ArtField::PrettyField(field); |
| RootPrinter root_printer; |
| field->VisitRoots(root_printer); |
| } else if (gc_root_source->HasArtMethod()) { |
| ArtMethod* method = gc_root_source->GetArtMethod(); |
| LOG(FATAL_WITHOUT_ABORT) << "gc root in method " << method << " " |
| << ArtMethod::PrettyMethod(method); |
| RootPrinter root_printer; |
| method->VisitRoots(root_printer, kRuntimePointerSize); |
| } |
| ref->GetLockWord(false).Dump(LOG_STREAM(FATAL_WITHOUT_ABORT)); |
| LOG(FATAL_WITHOUT_ABORT) << "Non-free regions:"; |
| region_space_->DumpNonFreeRegions(LOG_STREAM(FATAL_WITHOUT_ABORT)); |
| PrintFileToLog("/proc/self/maps", LogSeverity::FATAL_WITHOUT_ABORT); |
| MemMap::DumpMaps(LOG_STREAM(FATAL_WITHOUT_ABORT), /* terse= */ true); |
| LOG(FATAL) << "Invalid reference " << ref; |
| } |
| } else { |
| // Check to-space invariant in non-moving space. |
| AssertToSpaceInvariantInNonMovingSpace(/* obj= */ nullptr, ref); |
| } |
| } |
| } |
| |
| void ConcurrentCopying::LogFromSpaceRefHolder(mirror::Object* obj, MemberOffset offset) { |
| if (kUseBakerReadBarrier) { |
| LOG(INFO) << "holder=" << obj << " " << obj->PrettyTypeOf() |
| << " holder rb_state=" << obj->GetReadBarrierState(); |
| } else { |
| LOG(INFO) << "holder=" << obj << " " << obj->PrettyTypeOf(); |
| } |
| if (region_space_->IsInFromSpace(obj)) { |
| LOG(INFO) << "holder is in the from-space."; |
| } else if (region_space_->IsInToSpace(obj)) { |
| LOG(INFO) << "holder is in the to-space."; |
| } else if (region_space_->IsInUnevacFromSpace(obj)) { |
| LOG(INFO) << "holder is in the unevac from-space."; |
| if (IsMarkedInUnevacFromSpace(obj)) { |
| LOG(INFO) << "holder is marked in the region space bitmap."; |
| } else { |
| LOG(INFO) << "holder is not marked in the region space bitmap."; |
| } |
| } else { |
| // In a non-moving space. |
| if (immune_spaces_.ContainsObject(obj)) { |
| LOG(INFO) << "holder is in an immune image or the zygote space."; |
| } else { |
| LOG(INFO) << "holder is in a non-immune, non-moving (or main) space."; |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(obj); |
| accounting::LargeObjectBitmap* los_bitmap = |
| heap_mark_bitmap_->GetLargeObjectBitmap(obj); |
| CHECK(los_bitmap != nullptr) << "LOS bitmap covers the entire address range"; |
| bool is_los = mark_bitmap == nullptr; |
| if (!is_los && mark_bitmap->Test(obj)) { |
| LOG(INFO) << "holder is marked in the mark bit map."; |
| } else if (is_los && los_bitmap->Test(obj)) { |
| LOG(INFO) << "holder is marked in the los bit map."; |
| } else { |
| // If ref is on the allocation stack, then it is considered |
| // mark/alive (but not necessarily on the live stack.) |
| if (IsOnAllocStack(obj)) { |
| LOG(INFO) << "holder is on the alloc stack."; |
| } else { |
| LOG(INFO) << "holder is not marked or on the alloc stack."; |
| } |
| } |
| } |
| } |
| LOG(INFO) << "offset=" << offset.SizeValue(); |
| } |
| |
| void ConcurrentCopying::AssertToSpaceInvariantInNonMovingSpace(mirror::Object* obj, |
| mirror::Object* ref) { |
| CHECK(ref != nullptr); |
| CHECK(!region_space_->HasAddress(ref)) << "obj=" << obj << " ref=" << ref; |
| // In a non-moving space. Check that the ref is marked. |
| if (immune_spaces_.ContainsObject(ref)) { |
| // Immune space case. |
| if (kUseBakerReadBarrier) { |
| // Immune object may not be gray if called from the GC. |
| if (Thread::Current() == thread_running_gc_ && !gc_grays_immune_objects_) { |
| return; |
| } |
| bool updated_all_immune_objects = updated_all_immune_objects_.load(std::memory_order_seq_cst); |
| CHECK(updated_all_immune_objects || ref->GetReadBarrierState() == ReadBarrier::GrayState()) |
| << "Unmarked immune space ref. obj=" << obj << " rb_state=" |
| << (obj != nullptr ? obj->GetReadBarrierState() : 0U) |
| << " ref=" << ref << " ref rb_state=" << ref->GetReadBarrierState() |
| << " updated_all_immune_objects=" << updated_all_immune_objects; |
| } |
| } else { |
| // Non-moving space and large-object space (LOS) cases. |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(ref); |
| accounting::LargeObjectBitmap* los_bitmap = |
| heap_mark_bitmap_->GetLargeObjectBitmap(ref); |
| bool is_los = (mark_bitmap == nullptr); |
| |
| bool marked_in_non_moving_space_or_los = |
| (kUseBakerReadBarrier |
| && kEnableGenerationalConcurrentCopyingCollection |
| && young_gen_ |
| && !done_scanning_.load(std::memory_order_acquire)) |
| // Don't use the mark bitmap to ensure `ref` is marked: check that the |
| // read barrier state is gray instead. This is to take into account a |
| // potential race between two read barriers on the same reference when the |
| // young-generation collector is still scanning the dirty cards. |
| // |
| // For instance consider two concurrent read barriers on the same GC root |
| // reference during the dirty-card-scanning step of a young-generation |
| // collection. Both threads would call ReadBarrier::BarrierForRoot, which |
| // would: |
| // a. mark the reference (leading to a call to |
| // ConcurrentCopying::MarkNonMoving); then |
| // b. check the to-space invariant (leading to a call this |
| // ConcurrentCopying::AssertToSpaceInvariantInNonMovingSpace -- this |
| // method). |
| // |
| // In this situation, the following race could happen: |
| // 1. Thread A successfully changes `ref`'s read barrier state from |
| // non-gray (white) to gray (with AtomicSetReadBarrierState) in |
| // ConcurrentCopying::MarkNonMoving, then gets preempted. |
| // 2. Thread B also tries to change `ref`'s read barrier state with |
| // AtomicSetReadBarrierState from non-gray to gray in |
| // ConcurrentCopying::MarkNonMoving, but fails, as Thread A already |
| // changed it. |
| // 3. Because Thread B failed the previous CAS, it does *not* set the |
| // bit in the mark bitmap for `ref`. |
| // 4. Thread B checks the to-space invariant and calls |
| // ConcurrentCopying::AssertToSpaceInvariantInNonMovingSpace: the bit |
| // is not set in the mark bitmap for `ref`; checking that this bit is |
| // set to check the to-space invariant is therefore not a reliable |
| // test. |
| // 5. (Note that eventually, Thread A will resume its execution and set |
| // the bit for `ref` in the mark bitmap.) |
| ? (ref->GetReadBarrierState() == ReadBarrier::GrayState()) |
| // It is safe to use the heap mark bitmap otherwise. |
| : (!is_los && mark_bitmap->Test(ref)) || (is_los && los_bitmap->Test(ref)); |
| |
| // If `ref` is on the allocation stack, then it may not be |
| // marked live, but considered marked/alive (but not |
| // necessarily on the live stack). |
| CHECK(marked_in_non_moving_space_or_los || IsOnAllocStack(ref)) |
| << "Unmarked ref that's not on the allocation stack." |
| << " obj=" << obj |
| << " ref=" << ref |
| << " rb_state=" << ref->GetReadBarrierState() |
| << " is_los=" << std::boolalpha << is_los << std::noboolalpha |
| << " is_marking=" << std::boolalpha << is_marking_ << std::noboolalpha |
| << " young_gen=" << std::boolalpha << young_gen_ << std::noboolalpha |
| << " done_scanning=" |
| << std::boolalpha << done_scanning_.load(std::memory_order_acquire) << std::noboolalpha |
| << " self=" << Thread::Current(); |
| } |
| } |
| |
| // Used to scan ref fields of an object. |
| template <bool kNoUnEvac> |
| class ConcurrentCopying::RefFieldsVisitor { |
| public: |
| explicit RefFieldsVisitor(ConcurrentCopying* collector, Thread* const thread) |
| : collector_(collector), thread_(thread) { |
| // Cannot have `kNoUnEvac` when Generational CC collection is disabled. |
| DCHECK(kEnableGenerationalConcurrentCopyingCollection || !kNoUnEvac); |
| } |
| |
| void operator()(mirror::Object* obj, MemberOffset offset, bool /* is_static */) |
| const ALWAYS_INLINE REQUIRES_SHARED(Locks::mutator_lock_) |
| REQUIRES_SHARED(Locks::heap_bitmap_lock_) { |
| collector_->Process<kNoUnEvac>(obj, offset); |
| } |
| |
| void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const |
| REQUIRES_SHARED(Locks::mutator_lock_) ALWAYS_INLINE { |
| CHECK(klass->IsTypeOfReferenceClass()); |
| collector_->DelayReferenceReferent(klass, ref); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| ALWAYS_INLINE |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| ALWAYS_INLINE |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| collector_->MarkRoot</*kGrayImmuneObject=*/false>(thread_, root); |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| Thread* const thread_; |
| }; |
| |
| template <bool kNoUnEvac> |
| inline void ConcurrentCopying::Scan(mirror::Object* to_ref) { |
| // Cannot have `kNoUnEvac` when Generational CC collection is disabled. |
| DCHECK(kEnableGenerationalConcurrentCopyingCollection || !kNoUnEvac); |
| if (kDisallowReadBarrierDuringScan && !Runtime::Current()->IsActiveTransaction()) { |
| // Avoid all read barriers during visit references to help performance. |
| // Don't do this in transaction mode because we may read the old value of an field which may |
| // trigger read barriers. |
| Thread::Current()->ModifyDebugDisallowReadBarrier(1); |
| } |
| DCHECK(!region_space_->IsInFromSpace(to_ref)); |
| DCHECK_EQ(Thread::Current(), thread_running_gc_); |
| RefFieldsVisitor<kNoUnEvac> visitor(this, thread_running_gc_); |
| // Disable the read barrier for a performance reason. |
| to_ref->VisitReferences</*kVisitNativeRoots=*/true, kDefaultVerifyFlags, kWithoutReadBarrier>( |
| visitor, visitor); |
| if (kDisallowReadBarrierDuringScan && !Runtime::Current()->IsActiveTransaction()) { |
| thread_running_gc_->ModifyDebugDisallowReadBarrier(-1); |
| } |
| } |
| |
| template <bool kNoUnEvac> |
| inline void ConcurrentCopying::Process(mirror::Object* obj, MemberOffset offset) { |
| // Cannot have `kNoUnEvac` when Generational CC collection is disabled. |
| DCHECK(kEnableGenerationalConcurrentCopyingCollection || !kNoUnEvac); |
| DCHECK_EQ(Thread::Current(), thread_running_gc_); |
| mirror::Object* ref = obj->GetFieldObject< |
| mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset); |
| mirror::Object* to_ref = Mark</*kGrayImmuneObject=*/false, kNoUnEvac, /*kFromGCThread=*/true>( |
| thread_running_gc_, |
| ref, |
| /*holder=*/ obj, |
| offset); |
| if (to_ref == ref) { |
| return; |
| } |
| // This may fail if the mutator writes to the field at the same time. But it's ok. |
| mirror::Object* expected_ref = ref; |
| mirror::Object* new_ref = to_ref; |
| do { |
| if (expected_ref != |
| obj->GetFieldObject<mirror::Object, kVerifyNone, kWithoutReadBarrier, false>(offset)) { |
| // It was updated by the mutator. |
| break; |
| } |
| // Use release CAS to make sure threads reading the reference see contents of copied objects. |
| } while (!obj->CasFieldObjectWithoutWriteBarrier<false, false, kVerifyNone>( |
| offset, |
| expected_ref, |
| new_ref, |
| CASMode::kWeak, |
| std::memory_order_release)); |
| } |
| |
| // Process some roots. |
| inline void ConcurrentCopying::VisitRoots( |
| mirror::Object*** roots, size_t count, const RootInfo& info ATTRIBUTE_UNUSED) { |
| Thread* const self = Thread::Current(); |
| for (size_t i = 0; i < count; ++i) { |
| mirror::Object** root = roots[i]; |
| mirror::Object* ref = *root; |
| mirror::Object* to_ref = Mark(self, ref); |
| if (to_ref == ref) { |
| continue; |
| } |
| Atomic<mirror::Object*>* addr = reinterpret_cast<Atomic<mirror::Object*>*>(root); |
| mirror::Object* expected_ref = ref; |
| mirror::Object* new_ref = to_ref; |
| do { |
| if (expected_ref != addr->load(std::memory_order_relaxed)) { |
| // It was updated by the mutator. |
| break; |
| } |
| } while (!addr->CompareAndSetWeakRelaxed(expected_ref, new_ref)); |
| } |
| } |
| |
| template<bool kGrayImmuneObject> |
| inline void ConcurrentCopying::MarkRoot(Thread* const self, |
| mirror::CompressedReference<mirror::Object>* root) { |
| DCHECK(!root->IsNull()); |
| mirror::Object* const ref = root->AsMirrorPtr(); |
| mirror::Object* to_ref = Mark<kGrayImmuneObject>(self, ref); |
| if (to_ref != ref) { |
| auto* addr = reinterpret_cast<Atomic<mirror::CompressedReference<mirror::Object>>*>(root); |
| auto expected_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(ref); |
| auto new_ref = mirror::CompressedReference<mirror::Object>::FromMirrorPtr(to_ref); |
| // If the cas fails, then it was updated by the mutator. |
| do { |
| if (ref != addr->load(std::memory_order_relaxed).AsMirrorPtr()) { |
| // It was updated by the mutator. |
| break; |
| } |
| } while (!addr->CompareAndSetWeakRelaxed(expected_ref, new_ref)); |
| } |
| } |
| |
| inline void ConcurrentCopying::VisitRoots( |
| mirror::CompressedReference<mirror::Object>** roots, size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) { |
| Thread* const self = Thread::Current(); |
| for (size_t i = 0; i < count; ++i) { |
| mirror::CompressedReference<mirror::Object>* const root = roots[i]; |
| if (!root->IsNull()) { |
| // kGrayImmuneObject is true because this is used for the thread flip. |
| MarkRoot</*kGrayImmuneObject=*/true>(self, root); |
| } |
| } |
| } |
| |
| // Temporary set gc_grays_immune_objects_ to true in a scope if the current thread is GC. |
| class ConcurrentCopying::ScopedGcGraysImmuneObjects { |
| public: |
| explicit ScopedGcGraysImmuneObjects(ConcurrentCopying* collector) |
| : collector_(collector), enabled_(false) { |
| if (kUseBakerReadBarrier && |
| collector_->thread_running_gc_ == Thread::Current() && |
| !collector_->gc_grays_immune_objects_) { |
| collector_->gc_grays_immune_objects_ = true; |
| enabled_ = true; |
| } |
| } |
| |
| ~ScopedGcGraysImmuneObjects() { |
| if (kUseBakerReadBarrier && |
| collector_->thread_running_gc_ == Thread::Current() && |
| enabled_) { |
| DCHECK(collector_->gc_grays_immune_objects_); |
| collector_->gc_grays_immune_objects_ = false; |
| } |
| } |
| |
| private: |
| ConcurrentCopying* const collector_; |
| bool enabled_; |
| }; |
| |
| // Fill the given memory block with a dummy object. Used to fill in a |
| // copy of objects that was lost in race. |
| void ConcurrentCopying::FillWithDummyObject(Thread* const self, |
| mirror::Object* dummy_obj, |
| size_t byte_size) { |
| // GC doesn't gray immune objects while scanning immune objects. But we need to trigger the read |
| // barriers here because we need the updated reference to the int array class, etc. Temporary set |
| // gc_grays_immune_objects_ to true so that we won't cause a DCHECK failure in MarkImmuneSpace(). |
| ScopedGcGraysImmuneObjects scoped_gc_gray_immune_objects(this); |
| CHECK_ALIGNED(byte_size, kObjectAlignment); |
| memset(dummy_obj, 0, byte_size); |
| // Avoid going through read barrier for since kDisallowReadBarrierDuringScan may be enabled. |
| // Explicitly mark to make sure to get an object in the to-space. |
| mirror::Class* int_array_class = down_cast<mirror::Class*>( |
| Mark(self, GetClassRoot<mirror::IntArray, kWithoutReadBarrier>().Ptr())); |
| CHECK(int_array_class != nullptr); |
| if (ReadBarrier::kEnableToSpaceInvariantChecks) { |
| AssertToSpaceInvariant(nullptr, MemberOffset(0), int_array_class); |
| } |
| size_t component_size = int_array_class->GetComponentSize<kWithoutReadBarrier>(); |
| CHECK_EQ(component_size, sizeof(int32_t)); |
| size_t data_offset = mirror::Array::DataOffset(component_size).SizeValue(); |
| if (data_offset > byte_size) { |
| // An int array is too big. Use java.lang.Object. |
| CHECK(java_lang_Object_ != nullptr); |
| if (ReadBarrier::kEnableToSpaceInvariantChecks) { |
| AssertToSpaceInvariant(nullptr, MemberOffset(0), java_lang_Object_); |
| } |
| CHECK_EQ(byte_size, java_lang_Object_->GetObjectSize<kVerifyNone>()); |
| dummy_obj->SetClass(java_lang_Object_); |
| CHECK_EQ(byte_size, (dummy_obj->SizeOf<kVerifyNone>())); |
| } else { |
| // Use an int array. |
| dummy_obj->SetClass(int_array_class); |
| CHECK(dummy_obj->IsArrayInstance<kVerifyNone>()); |
| int32_t length = (byte_size - data_offset) / component_size; |
| mirror::Array* dummy_arr = dummy_obj->AsArray<kVerifyNone>(); |
| dummy_arr->SetLength(length); |
| CHECK_EQ(dummy_arr->GetLength(), length) |
| << "byte_size=" << byte_size << " length=" << length |
| << " component_size=" << component_size << " data_offset=" << data_offset; |
| CHECK_EQ(byte_size, (dummy_obj->SizeOf<kVerifyNone>())) |
| << "byte_size=" << byte_size << " length=" << length |
| << " component_size=" << component_size << " data_offset=" << data_offset; |
| } |
| } |
| |
| // Reuse the memory blocks that were copy of objects that were lost in race. |
| mirror::Object* ConcurrentCopying::AllocateInSkippedBlock(Thread* const self, size_t alloc_size) { |
| // Try to reuse the blocks that were unused due to CAS failures. |
| CHECK_ALIGNED(alloc_size, space::RegionSpace::kAlignment); |
| size_t min_object_size = RoundUp(sizeof(mirror::Object), space::RegionSpace::kAlignment); |
| size_t byte_size; |
| uint8_t* addr; |
| { |
| MutexLock mu(self, skipped_blocks_lock_); |
| auto it = skipped_blocks_map_.lower_bound(alloc_size); |
| if (it == skipped_blocks_map_.end()) { |
| // Not found. |
| return nullptr; |
| } |
| byte_size = it->first; |
| CHECK_GE(byte_size, alloc_size); |
| if (byte_size > alloc_size && byte_size - alloc_size < min_object_size) { |
| // If remainder would be too small for a dummy object, retry with a larger request size. |
| it = skipped_blocks_map_.lower_bound(alloc_size + min_object_size); |
| if (it == skipped_blocks_map_.end()) { |
| // Not found. |
| return nullptr; |
| } |
| CHECK_ALIGNED(it->first - alloc_size, space::RegionSpace::kAlignment); |
| CHECK_GE(it->first - alloc_size, min_object_size) |
| << "byte_size=" << byte_size << " it->first=" << it->first << " alloc_size=" << alloc_size; |
| } |
| // Found a block. |
| CHECK(it != skipped_blocks_map_.end()); |
| byte_size = it->first; |
| addr = it->second; |
| CHECK_GE(byte_size, alloc_size); |
| CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr))); |
| CHECK_ALIGNED(byte_size, space::RegionSpace::kAlignment); |
| if (kVerboseMode) { |
| LOG(INFO) << "Reusing skipped bytes : " << reinterpret_cast<void*>(addr) << ", " << byte_size; |
| } |
| skipped_blocks_map_.erase(it); |
| } |
| memset(addr, 0, byte_size); |
| if (byte_size > alloc_size) { |
| // Return the remainder to the map. |
| CHECK_ALIGNED(byte_size - alloc_size, space::RegionSpace::kAlignment); |
| CHECK_GE(byte_size - alloc_size, min_object_size); |
| // FillWithDummyObject may mark an object, avoid holding skipped_blocks_lock_ to prevent lock |
| // violation and possible deadlock. The deadlock case is a recursive case: |
| // FillWithDummyObject -> Mark(IntArray.class) -> Copy -> AllocateInSkippedBlock. |
| FillWithDummyObject(self, |
| reinterpret_cast<mirror::Object*>(addr + alloc_size), |
| byte_size - alloc_size); |
| CHECK(region_space_->IsInToSpace(reinterpret_cast<mirror::Object*>(addr + alloc_size))); |
| { |
| MutexLock mu(self, skipped_blocks_lock_); |
| skipped_blocks_map_.insert(std::make_pair(byte_size - alloc_size, addr + alloc_size)); |
| } |
| } |
| return reinterpret_cast<mirror::Object*>(addr); |
| } |
| |
| mirror::Object* ConcurrentCopying::Copy(Thread* const self, |
| mirror::Object* from_ref, |
| mirror::Object* holder, |
| MemberOffset offset) { |
| DCHECK(region_space_->IsInFromSpace(from_ref)); |
| // If the class pointer is null, the object is invalid. This could occur for a dangling pointer |
| // from a previous GC that is either inside or outside the allocated region. |
| mirror::Class* klass = from_ref->GetClass<kVerifyNone, kWithoutReadBarrier>(); |
| if (UNLIKELY(klass == nullptr)) { |
| // Remove memory protection from the region space and log debugging information. |
| region_space_->Unprotect(); |
| heap_->GetVerification()->LogHeapCorruption(holder, offset, from_ref, /* fatal= */ true); |
| } |
| // There must not be a read barrier to avoid nested RB that might violate the to-space invariant. |
| // Note that from_ref is a from space ref so the SizeOf() call will access the from-space meta |
| // objects, but it's ok and necessary. |
| size_t obj_size = from_ref->SizeOf<kDefaultVerifyFlags>(); |
| size_t region_space_alloc_size = (obj_size <= space::RegionSpace::kRegionSize) |
| ? RoundUp(obj_size, space::RegionSpace::kAlignment) |
| : RoundUp(obj_size, space::RegionSpace::kRegionSize); |
| size_t region_space_bytes_allocated = 0U; |
| size_t non_moving_space_bytes_allocated = 0U; |
| size_t bytes_allocated = 0U; |
| size_t dummy; |
| bool fall_back_to_non_moving = false; |
| mirror::Object* to_ref = region_space_->AllocNonvirtual</*kForEvac=*/ true>( |
| region_space_alloc_size, ®ion_space_bytes_allocated, nullptr, &dummy); |
| bytes_allocated = region_space_bytes_allocated; |
| if (LIKELY(to_ref != nullptr)) { |
| DCHECK_EQ(region_space_alloc_size, region_space_bytes_allocated); |
| } else { |
| // Failed to allocate in the region space. Try the skipped blocks. |
| to_ref = AllocateInSkippedBlock(self, region_space_alloc_size); |
| if (to_ref != nullptr) { |
| // Succeeded to allocate in a skipped block. |
| if (heap_->use_tlab_) { |
| // This is necessary for the tlab case as it's not accounted in the space. |
| region_space_->RecordAlloc(to_ref); |
| } |
| bytes_allocated = region_space_alloc_size; |
| heap_->num_bytes_allocated_.fetch_sub(bytes_allocated, std::memory_order_relaxed); |
| to_space_bytes_skipped_.fetch_sub(bytes_allocated, std::memory_order_relaxed); |
| to_space_objects_skipped_.fetch_sub(1, std::memory_order_relaxed); |
| } else { |
| // Fall back to the non-moving space. |
| fall_back_to_non_moving = true; |
| if (kVerboseMode) { |
| LOG(INFO) << "Out of memory in the to-space. Fall back to non-moving. skipped_bytes=" |
| << to_space_bytes_skipped_.load(std::memory_order_relaxed) |
| << " skipped_objects=" |
| << to_space_objects_skipped_.load(std::memory_order_relaxed); |
| } |
| to_ref = heap_->non_moving_space_->Alloc(self, obj_size, |
| &non_moving_space_bytes_allocated, nullptr, &dummy); |
| if (UNLIKELY(to_ref == nullptr)) { |
| LOG(FATAL_WITHOUT_ABORT) << "Fall-back non-moving space allocation failed for a " |
| << obj_size << " byte object in region type " |
| << region_space_->GetRegionType(from_ref); |
| LOG(FATAL) << "Object address=" << from_ref << " type=" << from_ref->PrettyTypeOf(); |
| } |
| bytes_allocated = non_moving_space_bytes_allocated; |
| // Mark it in the mark bitmap. |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref); |
| CHECK(mark_bitmap != nullptr); |
| bool previously_marked_in_bitmap = mark_bitmap->AtomicTestAndSet(to_ref); |
| CHECK(!previously_marked_in_bitmap); |
| } |
| } |
| DCHECK(to_ref != nullptr); |
| |
| // Copy the object excluding the lock word since that is handled in the loop. |
| to_ref->SetClass(klass); |
| const size_t kObjectHeaderSize = sizeof(mirror::Object); |
| DCHECK_GE(obj_size, kObjectHeaderSize); |
| static_assert(kObjectHeaderSize == sizeof(mirror::HeapReference<mirror::Class>) + |
| sizeof(LockWord), |
| "Object header size does not match"); |
| // Memcpy can tear for words since it may do byte copy. It is only safe to do this since the |
| // object in the from space is immutable other than the lock word. b/31423258 |
| memcpy(reinterpret_cast<uint8_t*>(to_ref) + kObjectHeaderSize, |
| reinterpret_cast<const uint8_t*>(from_ref) + kObjectHeaderSize, |
| obj_size - kObjectHeaderSize); |
| |
| // Attempt to install the forward pointer. This is in a loop as the |
| // lock word atomic write can fail. |
| while (true) { |
| LockWord old_lock_word = from_ref->GetLockWord(false); |
| |
| if (old_lock_word.GetState() == LockWord::kForwardingAddress) { |
| // Lost the race. Another thread (either GC or mutator) stored |
| // the forwarding pointer first. Make the lost copy (to_ref) |
| // look like a valid but dead (dummy) object and keep it for |
| // future reuse. |
| FillWithDummyObject(self, to_ref, bytes_allocated); |
| if (!fall_back_to_non_moving) { |
| DCHECK(region_space_->IsInToSpace(to_ref)); |
| if (bytes_allocated > space::RegionSpace::kRegionSize) { |
| // Free the large alloc. |
| region_space_->FreeLarge</*kForEvac=*/ true>(to_ref, bytes_allocated); |
| } else { |
| // Record the lost copy for later reuse. |
| heap_->num_bytes_allocated_.fetch_add(bytes_allocated, std::memory_order_relaxed); |
| to_space_bytes_skipped_.fetch_add(bytes_allocated, std::memory_order_relaxed); |
| to_space_objects_skipped_.fetch_add(1, std::memory_order_relaxed); |
| MutexLock mu(self, skipped_blocks_lock_); |
| skipped_blocks_map_.insert(std::make_pair(bytes_allocated, |
| reinterpret_cast<uint8_t*>(to_ref))); |
| } |
| } else { |
| DCHECK(heap_->non_moving_space_->HasAddress(to_ref)); |
| DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated); |
| // Free the non-moving-space chunk. |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(to_ref); |
| CHECK(mark_bitmap != nullptr); |
| CHECK(mark_bitmap->Clear(to_ref)); |
| heap_->non_moving_space_->Free(self, to_ref); |
| } |
| |
| // Get the winner's forward ptr. |
| mirror::Object* lost_fwd_ptr = to_ref; |
| to_ref = reinterpret_cast<mirror::Object*>(old_lock_word.ForwardingAddress()); |
| CHECK(to_ref != nullptr); |
| CHECK_NE(to_ref, lost_fwd_ptr); |
| CHECK(region_space_->IsInToSpace(to_ref) || heap_->non_moving_space_->HasAddress(to_ref)) |
| << "to_ref=" << to_ref << " " << heap_->DumpSpaces(); |
| CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress); |
| return to_ref; |
| } |
| |
| // Copy the old lock word over since we did not copy it yet. |
| to_ref->SetLockWord(old_lock_word, false); |
| // Set the gray ptr. |
| if (kUseBakerReadBarrier) { |
| to_ref->SetReadBarrierState(ReadBarrier::GrayState()); |
| } |
| |
| // Do a fence to prevent the field CAS in ConcurrentCopying::Process from possibly reordering |
| // before the object copy. |
| std::atomic_thread_fence(std::memory_order_release); |
| |
| LockWord new_lock_word = LockWord::FromForwardingAddress(reinterpret_cast<size_t>(to_ref)); |
| |
| // Try to atomically write the fwd ptr. |
| bool success = from_ref->CasLockWord(old_lock_word, |
| new_lock_word, |
| CASMode::kWeak, |
| std::memory_order_relaxed); |
| if (LIKELY(success)) { |
| // The CAS succeeded. |
| DCHECK(thread_running_gc_ != nullptr); |
| if (LIKELY(self == thread_running_gc_)) { |
| objects_moved_gc_thread_ += 1; |
| bytes_moved_gc_thread_ += region_space_alloc_size; |
| } else { |
| objects_moved_.fetch_add(1, std::memory_order_relaxed); |
| bytes_moved_.fetch_add(region_space_alloc_size, std::memory_order_relaxed); |
| } |
| |
| if (LIKELY(!fall_back_to_non_moving)) { |
| DCHECK(region_space_->IsInToSpace(to_ref)); |
| } else { |
| DCHECK(heap_->non_moving_space_->HasAddress(to_ref)); |
| DCHECK_EQ(bytes_allocated, non_moving_space_bytes_allocated); |
| } |
| if (kUseBakerReadBarrier) { |
| DCHECK(to_ref->GetReadBarrierState() == ReadBarrier::GrayState()); |
| } |
| DCHECK(GetFwdPtr(from_ref) == to_ref); |
| CHECK_NE(to_ref->GetLockWord(false).GetState(), LockWord::kForwardingAddress); |
| PushOntoMarkStack(self, to_ref); |
| return to_ref; |
| } else { |
| // The CAS failed. It may have lost the race or may have failed |
| // due to monitor/hashcode ops. Either way, retry. |
| } |
| } |
| } |
| |
| mirror::Object* ConcurrentCopying::IsMarked(mirror::Object* from_ref) { |
| DCHECK(from_ref != nullptr); |
| space::RegionSpace::RegionType rtype = region_space_->GetRegionType(from_ref); |
| if (rtype == space::RegionSpace::RegionType::kRegionTypeToSpace) { |
| // It's already marked. |
| return from_ref; |
| } |
| mirror::Object* to_ref; |
| if (rtype == space::RegionSpace::RegionType::kRegionTypeFromSpace) { |
| to_ref = GetFwdPtr(from_ref); |
| DCHECK(to_ref == nullptr || region_space_->IsInToSpace(to_ref) || |
| heap_->non_moving_space_->HasAddress(to_ref)) |
| << "from_ref=" << from_ref << " to_ref=" << to_ref; |
| } else if (rtype == space::RegionSpace::RegionType::kRegionTypeUnevacFromSpace) { |
| if (IsMarkedInUnevacFromSpace(from_ref)) { |
| to_ref = from_ref; |
| } else { |
| to_ref = nullptr; |
| } |
| } else { |
| // At this point, `from_ref` should not be in the region space |
| // (i.e. within an "unused" region). |
| DCHECK(!region_space_->HasAddress(from_ref)) << from_ref; |
| // from_ref is in a non-moving space. |
| if (immune_spaces_.ContainsObject(from_ref)) { |
| // An immune object is alive. |
| to_ref = from_ref; |
| } else { |
| // Non-immune non-moving space. Use the mark bitmap. |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(from_ref); |
| bool is_los = mark_bitmap == nullptr; |
| if (!is_los && mark_bitmap->Test(from_ref)) { |
| // Already marked. |
| to_ref = from_ref; |
| } else { |
| accounting::LargeObjectBitmap* los_bitmap = |
| heap_mark_bitmap_->GetLargeObjectBitmap(from_ref); |
| // We may not have a large object space for dex2oat, don't assume it exists. |
| if (los_bitmap == nullptr) { |
| CHECK(heap_->GetLargeObjectsSpace() == nullptr) |
| << "LOS bitmap covers the entire address range " << from_ref |
| << " " << heap_->DumpSpaces(); |
| } |
| if (los_bitmap != nullptr && is_los && los_bitmap->Test(from_ref)) { |
| // Already marked in LOS. |
| to_ref = from_ref; |
| } else { |
| // Not marked. |
| if (IsOnAllocStack(from_ref)) { |
| // If on the allocation stack, it's considered marked. |
| to_ref = from_ref; |
| } else { |
| // Not marked. |
| to_ref = nullptr; |
| } |
| } |
| } |
| } |
| } |
| return to_ref; |
| } |
| |
| bool ConcurrentCopying::IsOnAllocStack(mirror::Object* ref) { |
| // TODO: Explain why this is here. What release operation does it pair with? |
| std::atomic_thread_fence(std::memory_order_acquire); |
| accounting::ObjectStack* alloc_stack = GetAllocationStack(); |
| return alloc_stack->Contains(ref); |
| } |
| |
| mirror::Object* ConcurrentCopying::MarkNonMoving(Thread* const self, |
| mirror::Object* ref, |
| mirror::Object* holder, |
| MemberOffset offset) { |
| // ref is in a non-moving space (from_ref == to_ref). |
| DCHECK(!region_space_->HasAddress(ref)) << ref; |
| DCHECK(!immune_spaces_.ContainsObject(ref)); |
| // Use the mark bitmap. |
| accounting::ContinuousSpaceBitmap* mark_bitmap = |
| heap_mark_bitmap_->GetContinuousSpaceBitmap(ref); |
| accounting::LargeObjectBitmap* los_bitmap = |
| heap_mark_bitmap_->GetLargeObjectBitmap(ref); |
| bool is_los = mark_bitmap == nullptr; |
| if (kEnableGenerationalConcurrentCopyingCollection && young_gen_) { |
| // The sticky-bit CC collector is only compatible with Baker-style read barriers. |
| DCHECK(kUseBakerReadBarrier); |
| // Not done scanning, use AtomicSetReadBarrierPointer. |
| if (!done_scanning_.load(std::memory_order_acquire)) { |
| // Since the mark bitmap is still filled in from last GC, we can not use that or else the |
| // mutator may see references to the from space. Instead, use the Baker pointer itself as |
| // the mark bit. |
| // |
| // We need to avoid marking objects that are on allocation stack as that will lead to a |
| // situation (after this GC cycle is finished) where some object(s) are on both allocation |
| // stack and live bitmap. This leads to visiting the same object(s) twice during a heapdump |
| // (b/117426281). |
| if (!IsOnAllocStack(ref) && |
| ref->AtomicSetReadBarrierState(ReadBarrier::NonGrayState(), ReadBarrier::GrayState())) { |
| // TODO: We don't actually need to scan this object later, we just need to clear the gray |
| // bit. |
| // Also make sure the object is marked. |
| if (is_los) { |
| los_bitmap->AtomicTestAndSet(ref); |
| } else { |
| mark_bitmap->AtomicTestAndSet(ref); |
| } |
| // We don't need to mark newly allocated objects (those in allocation stack) as they can |
| // only point to to-space objects. Also, they are considered live till the next GC cycle. |
| PushOntoMarkStack(self, ref); |
| } |
| return ref; |
| } |
| } |
| if (!is_los && mark_bitmap->Test(ref)) { |
| // Already marked. |
| } else if (is_los && los_bitmap->Test(ref)) { |
| // Already marked in LOS. |
| } else { |
| // Not marked. |
| if (IsOnAllocStack(ref)) { |
| // If it's on the allocation stack, it's considered marked. Keep it white (non-gray). |
| // Objects on the allocation stack need not be marked. |
| if (!is_los) { |
| DCHECK(!mark_bitmap->Test(ref)); |
| } else { |
| DCHECK(!los_bitmap->Test(ref)); |
| } |
| if (kUseBakerReadBarrier) { |
| DCHECK_EQ(ref->GetReadBarrierState(), ReadBarrier::NonGrayState()); |
| } |
| } else { |
| // For the baker-style RB, we need to handle 'false-gray' cases. See the |
| // kRegionTypeUnevacFromSpace-case comment in Mark(). |
| if (kUseBakerReadBarrier) { |
| // Test the bitmap first to reduce the chance of false gray cases. |
| if ((!is_los && mark_bitmap->Test(ref)) || |
| (is_los && los_bitmap->Test(ref))) { |
| return ref; |
| } |
| } |
| if (is_los && !IsAligned<kPageSize>(ref)) { |
| // Ref is a large object that is not aligned, it must be heap |
| // corruption. Remove memory protection and dump data before |
| // AtomicSetReadBarrierState since it will fault if the address is not |
| // valid. |
| region_space_->Unprotect(); |
| heap_->GetVerification()->LogHeapCorruption(holder, offset, ref, /* fatal= */ true); |
| } |
| // Not marked nor on the allocation stack. Try to mark it. |
| // This may or may not succeed, which is ok. |
| bool cas_success = false; |
| if (kUseBakerReadBarrier) { |
| cas_success = ref->AtomicSetReadBarrierState(ReadBarrier::NonGrayState(), |
| ReadBarrier::GrayState()); |
| } |
| if (!is_los && mark_bitmap->AtomicTestAndSet(ref)) { |
| // Already marked. |
| if (kUseBakerReadBarrier && |
| cas_success && |
| ref->GetReadBarrierState() == ReadBarrier::GrayState()) { |
| PushOntoFalseGrayStack(self, ref); |
| } |
| } else if (is_los && los_bitmap->AtomicTestAndSet(ref)) { |
| // Already marked in LOS. |
| if (kUseBakerReadBarrier && |
| cas_success && |
| ref->GetReadBarrierState() == ReadBarrier::GrayState()) { |
| PushOntoFalseGrayStack(self, ref); |
| } |
| } else { |
| // Newly marked. |
| if (kUseBakerReadBarrier) { |
| DCHECK_EQ(ref->GetReadBarrierState(), ReadBarrier::GrayState()); |
| } |
| PushOntoMarkStack(self, ref); |
| } |
| } |
| } |
| return ref; |
| } |
| |
| void ConcurrentCopying::FinishPhase() { |
| Thread* const self = Thread::Current(); |
| { |
| MutexLock mu(self, mark_stack_lock_); |
| CHECK_EQ(pooled_mark_stacks_.size(), kMarkStackPoolSize); |
| } |
| // kVerifyNoMissingCardMarks relies on the region space cards not being cleared to avoid false |
| // positives. |
| if (!kEnableGenerationalConcurrentCopyingCollection && !kVerifyNoMissingCardMarks) { |
| TimingLogger::ScopedTiming split("ClearRegionSpaceCards", GetTimings()); |
| // We do not currently use the region space cards at all, madvise them away to save ram. |
| heap_->GetCardTable()->ClearCardRange(region_space_->Begin(), region_space_->Limit()); |
| } |
| { |
| MutexLock mu(self, skipped_blocks_lock_); |
| skipped_blocks_map_.clear(); |
| } |
| { |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| { |
| WriterMutexLock mu2(self, *Locks::heap_bitmap_lock_); |
| heap_->ClearMarkedObjects(); |
| } |
| if (kUseBakerReadBarrier && kFilterModUnionCards) { |
| TimingLogger::ScopedTiming split("FilterModUnionCards", GetTimings()); |
| ReaderMutexLock mu2(self, *Locks::heap_bitmap_lock_); |
| for (space::ContinuousSpace* space : immune_spaces_.GetSpaces()) { |
| DCHECK(space->IsImageSpace() || space->IsZygoteSpace()); |
| accounting::ModUnionTable* table = heap_->FindModUnionTableFromSpace(space); |
| // Filter out cards that don't need to be set. |
| if (table != nullptr) { |
| table->FilterCards(); |
| } |
| } |
| } |
| if (kUseBakerReadBarrier) { |
| TimingLogger::ScopedTiming split("EmptyRBMarkBitStack", GetTimings()); |
| DCHECK(rb_mark_bit_stack_ != nullptr); |
| const auto* limit = rb_mark_bit_stack_->End(); |
| for (StackReference<mirror::Object>* it = rb_mark_bit_stack_->Begin(); it != limit; ++it) { |
| CHECK(it->AsMirrorPtr()->AtomicSetMarkBit(1, 0)) |
| << "rb_mark_bit_stack_->Begin()" << rb_mark_bit_stack_->Begin() << '\n' |
| << "rb_mark_bit_stack_->End()" << rb_mark_bit_stack_->End() << '\n' |
| << "rb_mark_bit_stack_->IsFull()" |
| << std::boolalpha << rb_mark_bit_stack_->IsFull() << std::noboolalpha << '\n' |
| << DumpReferenceInfo(it->AsMirrorPtr(), "*it"); |
| } |
| rb_mark_bit_stack_->Reset(); |
| } |
| } |
| if (measure_read_barrier_slow_path_) { |
| MutexLock mu(self, rb_slow_path_histogram_lock_); |
| rb_slow_path_time_histogram_.AdjustAndAddValue( |
| rb_slow_path_ns_.load(std::memory_order_relaxed)); |
| rb_slow_path_count_total_ += rb_slow_path_count_.load(std::memory_order_relaxed); |
| rb_slow_path_count_gc_total_ += rb_slow_path_count_gc_.load(std::memory_order_relaxed); |
| } |
| } |
| |
| bool ConcurrentCopying::IsNullOrMarkedHeapReference(mirror::HeapReference<mirror::Object>* field, |
| bool do_atomic_update) { |
| mirror::Object* from_ref = field->AsMirrorPtr(); |
| if (from_ref == nullptr) { |
| return true; |
| } |
| mirror::Object* to_ref = IsMarked(from_ref); |
| if (to_ref == nullptr) { |
| return false; |
| } |
| if (from_ref != to_ref) { |
| if (do_atomic_update) { |
| do { |
| if (field->AsMirrorPtr() != from_ref) { |
| // Concurrently overwritten by a mutator. |
| break; |
| } |
| } while (!field->CasWeakRelaxed(from_ref, to_ref)); |
| } else { |
| // TODO: Why is this seq_cst when the above is relaxed? Document memory ordering. |
| field->Assign</* kIsVolatile= */ true>(to_ref); |
| } |
| } |
| return true; |
| } |
| |
| mirror::Object* ConcurrentCopying::MarkObject(mirror::Object* from_ref) { |
| return Mark(Thread::Current(), from_ref); |
| } |
| |
| void ConcurrentCopying::DelayReferenceReferent(ObjPtr<mirror::Class> klass, |
| ObjPtr<mirror::Reference> reference) { |
| heap_->GetReferenceProcessor()->DelayReferenceReferent(klass, reference, this); |
| } |
| |
| void ConcurrentCopying::ProcessReferences(Thread* self) { |
| TimingLogger::ScopedTiming split("ProcessReferences", GetTimings()); |
| // We don't really need to lock the heap bitmap lock as we use CAS to mark in bitmaps. |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| GetHeap()->GetReferenceProcessor()->ProcessReferences( |
| /*concurrent=*/ true, GetTimings(), GetCurrentIteration()->GetClearSoftReferences(), this); |
| } |
| |
| void ConcurrentCopying::RevokeAllThreadLocalBuffers() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| region_space_->RevokeAllThreadLocalBuffers(); |
| } |
| |
| mirror::Object* ConcurrentCopying::MarkFromReadBarrierWithMeasurements(Thread* const self, |
| mirror::Object* from_ref) { |
| if (self != thread_running_gc_) { |
| rb_slow_path_count_.fetch_add(1u, std::memory_order_relaxed); |
| } else { |
| rb_slow_path_count_gc_.fetch_add(1u, std::memory_order_relaxed); |
| } |
| ScopedTrace tr(__FUNCTION__); |
| const uint64_t start_time = measure_read_barrier_slow_path_ ? NanoTime() : 0u; |
| mirror::Object* ret = |
| Mark</*kGrayImmuneObject=*/true, /*kNoUnEvac=*/false, /*kFromGCThread=*/false>(self, |
| from_ref); |
| if (measure_read_barrier_slow_path_) { |
| rb_slow_path_ns_.fetch_add(NanoTime() - start_time, std::memory_order_relaxed); |
| } |
| return ret; |
| } |
| |
| void ConcurrentCopying::DumpPerformanceInfo(std::ostream& os) { |
| GarbageCollector::DumpPerformanceInfo(os); |
| MutexLock mu(Thread::Current(), rb_slow_path_histogram_lock_); |
| if (rb_slow_path_time_histogram_.SampleSize() > 0) { |
| Histogram<uint64_t>::CumulativeData cumulative_data; |
| rb_slow_path_time_histogram_.CreateHistogram(&cumulative_data); |
| rb_slow_path_time_histogram_.PrintConfidenceIntervals(os, 0.99, cumulative_data); |
| } |
| if (rb_slow_path_count_total_ > 0) { |
| os << "Slow path count " << rb_slow_path_count_total_ << "\n"; |
| } |
| if (rb_slow_path_count_gc_total_ > 0) { |
| os << "GC slow path count " << rb_slow_path_count_gc_total_ << "\n"; |
| } |
| float average_ratio = copied_live_bytes_ratio_sum_ / gc_count_; |
| |
| if (young_gen_) { |
| os << "Average minor GC copied live bytes ratio " |
| << average_ratio << " over " << gc_count_ << " minor GCs\n"; |
| } else { |
| os << "Average major GC copied live bytes ratio " |
| << average_ratio << " over " << gc_count_ << " major GCs\n"; |
| } |
| os << "Cumulative bytes moved " |
| << cumulative_bytes_moved_.load(std::memory_order_relaxed) << "\n"; |
| os << "Cumulative objects moved " |
| << cumulative_objects_moved_.load(std::memory_order_relaxed) << "\n"; |
| |
| os << "Peak regions allocated " |
| << region_space_->GetMaxPeakNumNonFreeRegions() << " (" |
| << PrettySize(region_space_->GetMaxPeakNumNonFreeRegions() * space::RegionSpace::kRegionSize) |
| << ") / " << region_space_->GetNumRegions() / 2 << " (" |
| << PrettySize(region_space_->GetNumRegions() * space::RegionSpace::kRegionSize / 2) |
| << ")\n"; |
| } |
| |
| } // namespace collector |
| } // namespace gc |
| } // namespace art |