| /* |
| * Copyright (C) 2011 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 "mark_sweep.h" |
| |
| #include <atomic> |
| #include <functional> |
| #include <numeric> |
| #include <climits> |
| #include <vector> |
| |
| #include "base/bounded_fifo.h" |
| #include "base/enums.h" |
| #include "base/logging.h" |
| #include "base/macros.h" |
| #include "base/mutex-inl.h" |
| #include "base/systrace.h" |
| #include "base/time_utils.h" |
| #include "base/timing_logger.h" |
| #include "gc/accounting/card_table-inl.h" |
| #include "gc/accounting/heap_bitmap-inl.h" |
| #include "gc/accounting/mod_union_table.h" |
| #include "gc/accounting/space_bitmap-inl.h" |
| #include "gc/heap.h" |
| #include "gc/reference_processor.h" |
| #include "gc/space/large_object_space.h" |
| #include "gc/space/space-inl.h" |
| #include "mark_sweep-inl.h" |
| #include "mirror/object-inl.h" |
| #include "runtime.h" |
| #include "scoped_thread_state_change-inl.h" |
| #include "thread-current-inl.h" |
| #include "thread_list.h" |
| |
| namespace art { |
| namespace gc { |
| namespace collector { |
| |
| // Performance options. |
| static constexpr bool kUseRecursiveMark = false; |
| static constexpr bool kUseMarkStackPrefetch = true; |
| static constexpr size_t kSweepArrayChunkFreeSize = 1024; |
| static constexpr bool kPreCleanCards = true; |
| |
| // Parallelism options. |
| static constexpr bool kParallelCardScan = true; |
| static constexpr bool kParallelRecursiveMark = true; |
| // Don't attempt to parallelize mark stack processing unless the mark stack is at least n |
| // elements. This is temporary until we reduce the overhead caused by allocating tasks, etc.. Not |
| // having this can add overhead in ProcessReferences since we may end up doing many calls of |
| // ProcessMarkStack with very small mark stacks. |
| static constexpr size_t kMinimumParallelMarkStackSize = 128; |
| static constexpr bool kParallelProcessMarkStack = true; |
| |
| // Profiling and information flags. |
| static constexpr bool kProfileLargeObjects = false; |
| static constexpr bool kMeasureOverhead = false; |
| static constexpr bool kCountTasks = false; |
| static constexpr bool kCountMarkedObjects = false; |
| |
| // Turn off kCheckLocks when profiling the GC since it slows the GC down by up to 40%. |
| static constexpr bool kCheckLocks = kDebugLocking; |
| static constexpr bool kVerifyRootsMarked = kIsDebugBuild; |
| |
| // If true, revoke the rosalloc thread-local buffers at the |
| // checkpoint, as opposed to during the pause. |
| static constexpr bool kRevokeRosAllocThreadLocalBuffersAtCheckpoint = true; |
| |
| void MarkSweep::BindBitmaps() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_); |
| // Mark all of the spaces we never collect as immune. |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if (space->GetGcRetentionPolicy() == space::kGcRetentionPolicyNeverCollect) { |
| immune_spaces_.AddSpace(space); |
| } |
| } |
| } |
| |
| MarkSweep::MarkSweep(Heap* heap, bool is_concurrent, const std::string& name_prefix) |
| : GarbageCollector(heap, |
| name_prefix + |
| (is_concurrent ? "concurrent mark sweep": "mark sweep")), |
| current_space_bitmap_(nullptr), |
| mark_bitmap_(nullptr), |
| mark_stack_(nullptr), |
| gc_barrier_(new Barrier(0)), |
| mark_stack_lock_("mark sweep mark stack lock", kMarkSweepMarkStackLock), |
| is_concurrent_(is_concurrent), |
| live_stack_freeze_size_(0) { |
| std::string error_msg; |
| MemMap* mem_map = MemMap::MapAnonymous( |
| "mark sweep sweep array free buffer", nullptr, |
| RoundUp(kSweepArrayChunkFreeSize * sizeof(mirror::Object*), kPageSize), |
| PROT_READ | PROT_WRITE, false, false, &error_msg); |
| CHECK(mem_map != nullptr) << "Couldn't allocate sweep array free buffer: " << error_msg; |
| sweep_array_free_buffer_mem_map_.reset(mem_map); |
| } |
| |
| void MarkSweep::InitializePhase() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| mark_stack_ = heap_->GetMarkStack(); |
| DCHECK(mark_stack_ != nullptr); |
| immune_spaces_.Reset(); |
| no_reference_class_count_.StoreRelaxed(0); |
| normal_count_.StoreRelaxed(0); |
| class_count_.StoreRelaxed(0); |
| object_array_count_.StoreRelaxed(0); |
| other_count_.StoreRelaxed(0); |
| reference_count_.StoreRelaxed(0); |
| large_object_test_.StoreRelaxed(0); |
| large_object_mark_.StoreRelaxed(0); |
| overhead_time_ .StoreRelaxed(0); |
| work_chunks_created_.StoreRelaxed(0); |
| work_chunks_deleted_.StoreRelaxed(0); |
| mark_null_count_.StoreRelaxed(0); |
| mark_immune_count_.StoreRelaxed(0); |
| mark_fastpath_count_.StoreRelaxed(0); |
| mark_slowpath_count_.StoreRelaxed(0); |
| { |
| // TODO: I don't think we should need heap bitmap lock to Get the mark bitmap. |
| ReaderMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_); |
| mark_bitmap_ = heap_->GetMarkBitmap(); |
| } |
| if (!GetCurrentIteration()->GetClearSoftReferences()) { |
| // Always clear soft references if a non-sticky collection. |
| GetCurrentIteration()->SetClearSoftReferences(GetGcType() != collector::kGcTypeSticky); |
| } |
| } |
| |
| void MarkSweep::RunPhases() { |
| Thread* self = Thread::Current(); |
| InitializePhase(); |
| Locks::mutator_lock_->AssertNotHeld(self); |
| if (IsConcurrent()) { |
| GetHeap()->PreGcVerification(this); |
| { |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| MarkingPhase(); |
| } |
| ScopedPause pause(this); |
| GetHeap()->PrePauseRosAllocVerification(this); |
| PausePhase(); |
| RevokeAllThreadLocalBuffers(); |
| } else { |
| ScopedPause pause(this); |
| GetHeap()->PreGcVerificationPaused(this); |
| MarkingPhase(); |
| GetHeap()->PrePauseRosAllocVerification(this); |
| PausePhase(); |
| RevokeAllThreadLocalBuffers(); |
| } |
| { |
| // Sweeping always done concurrently, even for non concurrent mark sweep. |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| ReclaimPhase(); |
| } |
| GetHeap()->PostGcVerification(this); |
| FinishPhase(); |
| } |
| |
| void MarkSweep::ProcessReferences(Thread* self) { |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| GetHeap()->GetReferenceProcessor()->ProcessReferences( |
| true, |
| GetTimings(), |
| GetCurrentIteration()->GetClearSoftReferences(), |
| this); |
| } |
| |
| void MarkSweep::PausePhase() { |
| TimingLogger::ScopedTiming t("(Paused)PausePhase", GetTimings()); |
| Thread* self = Thread::Current(); |
| Locks::mutator_lock_->AssertExclusiveHeld(self); |
| if (IsConcurrent()) { |
| // Handle the dirty objects if we are a concurrent GC. |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| // Re-mark root set. |
| ReMarkRoots(); |
| // Scan dirty objects, this is only required if we are not doing concurrent GC. |
| RecursiveMarkDirtyObjects(true, accounting::CardTable::kCardDirty); |
| } |
| { |
| TimingLogger::ScopedTiming t2("SwapStacks", GetTimings()); |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| heap_->SwapStacks(); |
| live_stack_freeze_size_ = heap_->GetLiveStack()->Size(); |
| // Need to revoke all the thread local allocation stacks since we just swapped the allocation |
| // stacks and don't want anybody to allocate into the live stack. |
| RevokeAllThreadLocalAllocationStacks(self); |
| } |
| heap_->PreSweepingGcVerification(this); |
| // Disallow new system weaks to prevent a race which occurs when someone adds a new system |
| // weak before we sweep them. Since this new system weak may not be marked, the GC may |
| // incorrectly sweep it. This also fixes a race where interning may attempt to return a strong |
| // reference to a string that is about to be swept. |
| Runtime::Current()->DisallowNewSystemWeaks(); |
| // Enable the reference processing slow path, needs to be done with mutators paused since there |
| // is no lock in the GetReferent fast path. |
| GetHeap()->GetReferenceProcessor()->EnableSlowPath(); |
| } |
| |
| void MarkSweep::PreCleanCards() { |
| // Don't do this for non concurrent GCs since they don't have any dirty cards. |
| if (kPreCleanCards && IsConcurrent()) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Thread* self = Thread::Current(); |
| CHECK(!Locks::mutator_lock_->IsExclusiveHeld(self)); |
| // Process dirty cards and add dirty cards to mod union tables, also ages cards. |
| heap_->ProcessCards(GetTimings(), false, true, false); |
| // The checkpoint root marking is required to avoid a race condition which occurs if the |
| // following happens during a reference write: |
| // 1. mutator dirties the card (write barrier) |
| // 2. GC ages the card (the above ProcessCards call) |
| // 3. GC scans the object (the RecursiveMarkDirtyObjects call below) |
| // 4. mutator writes the value (corresponding to the write barrier in 1.) |
| // This causes the GC to age the card but not necessarily mark the reference which the mutator |
| // wrote into the object stored in the card. |
| // Having the checkpoint fixes this issue since it ensures that the card mark and the |
| // reference write are visible to the GC before the card is scanned (this is due to locks being |
| // acquired / released in the checkpoint code). |
| // The other roots are also marked to help reduce the pause. |
| MarkRootsCheckpoint(self, false); |
| MarkNonThreadRoots(); |
| MarkConcurrentRoots( |
| static_cast<VisitRootFlags>(kVisitRootFlagClearRootLog | kVisitRootFlagNewRoots)); |
| // Process the newly aged cards. |
| RecursiveMarkDirtyObjects(false, accounting::CardTable::kCardDirty - 1); |
| // TODO: Empty allocation stack to reduce the number of objects we need to test / mark as live |
| // in the next GC. |
| } |
| } |
| |
| void MarkSweep::RevokeAllThreadLocalAllocationStacks(Thread* self) { |
| if (kUseThreadLocalAllocationStack) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Locks::mutator_lock_->AssertExclusiveHeld(self); |
| heap_->RevokeAllThreadLocalAllocationStacks(self); |
| } |
| } |
| |
| void MarkSweep::MarkingPhase() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Thread* self = Thread::Current(); |
| BindBitmaps(); |
| FindDefaultSpaceBitmap(); |
| // Process dirty cards and add dirty cards to mod union tables. |
| // If the GC type is non sticky, then we just clear the cards instead of ageing them. |
| heap_->ProcessCards(GetTimings(), false, true, GetGcType() != kGcTypeSticky); |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| MarkRoots(self); |
| MarkReachableObjects(); |
| // Pre-clean dirtied cards to reduce pauses. |
| PreCleanCards(); |
| } |
| |
| class MarkSweep::ScanObjectVisitor { |
| public: |
| explicit ScanObjectVisitor(MarkSweep* const mark_sweep) ALWAYS_INLINE |
| : mark_sweep_(mark_sweep) {} |
| |
| void operator()(ObjPtr<mirror::Object> obj) const |
| ALWAYS_INLINE |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (kCheckLocks) { |
| Locks::mutator_lock_->AssertSharedHeld(Thread::Current()); |
| Locks::heap_bitmap_lock_->AssertExclusiveHeld(Thread::Current()); |
| } |
| mark_sweep_->ScanObject(obj.Ptr()); |
| } |
| |
| private: |
| MarkSweep* const mark_sweep_; |
| }; |
| |
| void MarkSweep::UpdateAndMarkModUnion() { |
| for (const auto& space : immune_spaces_.GetSpaces()) { |
| const char* name = space->IsZygoteSpace() |
| ? "UpdateAndMarkZygoteModUnionTable" |
| : "UpdateAndMarkImageModUnionTable"; |
| DCHECK(space->IsZygoteSpace() || space->IsImageSpace()) << *space; |
| TimingLogger::ScopedTiming t(name, GetTimings()); |
| accounting::ModUnionTable* mod_union_table = heap_->FindModUnionTableFromSpace(space); |
| if (mod_union_table != nullptr) { |
| mod_union_table->UpdateAndMarkReferences(this); |
| } else { |
| // No mod-union table, scan all the live bits. This can only occur for app images. |
| space->GetLiveBitmap()->VisitMarkedRange(reinterpret_cast<uintptr_t>(space->Begin()), |
| reinterpret_cast<uintptr_t>(space->End()), |
| ScanObjectVisitor(this)); |
| } |
| } |
| } |
| |
| void MarkSweep::MarkReachableObjects() { |
| UpdateAndMarkModUnion(); |
| // Recursively mark all the non-image bits set in the mark bitmap. |
| RecursiveMark(); |
| } |
| |
| void MarkSweep::ReclaimPhase() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Thread* const self = Thread::Current(); |
| // Process the references concurrently. |
| ProcessReferences(self); |
| SweepSystemWeaks(self); |
| Runtime* const runtime = Runtime::Current(); |
| runtime->AllowNewSystemWeaks(); |
| // Clean up class loaders after system weaks are swept since that is how we know if class |
| // unloading occurred. |
| runtime->GetClassLinker()->CleanupClassLoaders(); |
| { |
| WriterMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| GetHeap()->RecordFreeRevoke(); |
| // Reclaim unmarked objects. |
| Sweep(false); |
| // Swap the live and mark bitmaps for each space which we modified space. This is an |
| // optimization that enables us to not clear live bits inside of the sweep. Only swaps unbound |
| // bitmaps. |
| SwapBitmaps(); |
| // Unbind the live and mark bitmaps. |
| GetHeap()->UnBindBitmaps(); |
| } |
| } |
| |
| void MarkSweep::FindDefaultSpaceBitmap() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| accounting::ContinuousSpaceBitmap* bitmap = space->GetMarkBitmap(); |
| // We want to have the main space instead of non moving if possible. |
| if (bitmap != nullptr && |
| space->GetGcRetentionPolicy() == space::kGcRetentionPolicyAlwaysCollect) { |
| current_space_bitmap_ = bitmap; |
| // If we are not the non moving space exit the loop early since this will be good enough. |
| if (space != heap_->GetNonMovingSpace()) { |
| break; |
| } |
| } |
| } |
| CHECK(current_space_bitmap_ != nullptr) << "Could not find a default mark bitmap\n" |
| << heap_->DumpSpaces(); |
| } |
| |
| void MarkSweep::ExpandMarkStack() { |
| ResizeMarkStack(mark_stack_->Capacity() * 2); |
| } |
| |
| void MarkSweep::ResizeMarkStack(size_t new_size) { |
| // Rare case, no need to have Thread::Current be a parameter. |
| if (UNLIKELY(mark_stack_->Size() < mark_stack_->Capacity())) { |
| // Someone else acquired the lock and expanded the mark stack before us. |
| return; |
| } |
| std::vector<StackReference<mirror::Object>> temp(mark_stack_->Begin(), mark_stack_->End()); |
| CHECK_LE(mark_stack_->Size(), new_size); |
| mark_stack_->Resize(new_size); |
| for (auto& obj : temp) { |
| mark_stack_->PushBack(obj.AsMirrorPtr()); |
| } |
| } |
| |
| mirror::Object* MarkSweep::MarkObject(mirror::Object* obj) { |
| MarkObject(obj, nullptr, MemberOffset(0)); |
| return obj; |
| } |
| |
| inline void MarkSweep::MarkObjectNonNullParallel(mirror::Object* obj) { |
| DCHECK(obj != nullptr); |
| if (MarkObjectParallel(obj)) { |
| MutexLock mu(Thread::Current(), mark_stack_lock_); |
| if (UNLIKELY(mark_stack_->Size() >= mark_stack_->Capacity())) { |
| ExpandMarkStack(); |
| } |
| // The object must be pushed on to the mark stack. |
| mark_stack_->PushBack(obj); |
| } |
| } |
| |
| bool MarkSweep::IsNullOrMarkedHeapReference(mirror::HeapReference<mirror::Object>* ref, |
| bool do_atomic_update ATTRIBUTE_UNUSED) { |
| mirror::Object* obj = ref->AsMirrorPtr(); |
| if (obj == nullptr) { |
| return true; |
| } |
| return IsMarked(obj); |
| } |
| |
| class MarkSweep::MarkObjectSlowPath { |
| public: |
| explicit MarkObjectSlowPath(MarkSweep* mark_sweep, |
| mirror::Object* holder = nullptr, |
| MemberOffset offset = MemberOffset(0)) |
| : mark_sweep_(mark_sweep), |
| holder_(holder), |
| offset_(offset) {} |
| |
| void operator()(const mirror::Object* obj) const NO_THREAD_SAFETY_ANALYSIS { |
| if (kProfileLargeObjects) { |
| // TODO: Differentiate between marking and testing somehow. |
| ++mark_sweep_->large_object_test_; |
| ++mark_sweep_->large_object_mark_; |
| } |
| space::LargeObjectSpace* large_object_space = mark_sweep_->GetHeap()->GetLargeObjectsSpace(); |
| if (UNLIKELY(obj == nullptr || !IsAligned<kPageSize>(obj) || |
| (kIsDebugBuild && large_object_space != nullptr && |
| !large_object_space->Contains(obj)))) { |
| // Lowest priority logging first: |
| PrintFileToLog("/proc/self/maps", LogSeverity::FATAL_WITHOUT_ABORT); |
| MemMap::DumpMaps(LOG_STREAM(FATAL_WITHOUT_ABORT), true); |
| // Buffer the output in the string stream since it is more important than the stack traces |
| // and we want it to have log priority. The stack traces are printed from Runtime::Abort |
| // which is called from LOG(FATAL) but before the abort message. |
| std::ostringstream oss; |
| oss << "Tried to mark " << obj << " not contained by any spaces" << std::endl; |
| if (holder_ != nullptr) { |
| size_t holder_size = holder_->SizeOf(); |
| ArtField* field = holder_->FindFieldByOffset(offset_); |
| oss << "Field info: " |
| << " holder=" << holder_ |
| << " holder is " |
| << (mark_sweep_->GetHeap()->IsLiveObjectLocked(holder_) |
| ? "alive" : "dead") |
| << " holder_size=" << holder_size |
| << " holder_type=" << holder_->PrettyTypeOf() |
| << " offset=" << offset_.Uint32Value() |
| << " field=" << (field != nullptr ? field->GetName() : "nullptr") |
| << " field_type=" |
| << (field != nullptr ? field->GetTypeDescriptor() : "") |
| << " first_ref_field_offset=" |
| << (holder_->IsClass() |
| ? holder_->AsClass()->GetFirstReferenceStaticFieldOffset( |
| kRuntimePointerSize) |
| : holder_->GetClass()->GetFirstReferenceInstanceFieldOffset()) |
| << " num_of_ref_fields=" |
| << (holder_->IsClass() |
| ? holder_->AsClass()->NumReferenceStaticFields() |
| : holder_->GetClass()->NumReferenceInstanceFields()) |
| << std::endl; |
| // Print the memory content of the holder. |
| for (size_t i = 0; i < holder_size / sizeof(uint32_t); ++i) { |
| uint32_t* p = reinterpret_cast<uint32_t*>(holder_); |
| oss << &p[i] << ": " << "holder+" << (i * sizeof(uint32_t)) << " = " << std::hex << p[i] |
| << std::endl; |
| } |
| } |
| oss << "Attempting see if it's a bad thread root" << std::endl; |
| mark_sweep_->VerifySuspendedThreadRoots(oss); |
| LOG(FATAL) << oss.str(); |
| } |
| } |
| |
| private: |
| MarkSweep* const mark_sweep_; |
| mirror::Object* const holder_; |
| MemberOffset offset_; |
| }; |
| |
| inline void MarkSweep::MarkObjectNonNull(mirror::Object* obj, |
| mirror::Object* holder, |
| MemberOffset offset) { |
| DCHECK(obj != nullptr); |
| if (kUseBakerReadBarrier) { |
| // Verify all the objects have the correct state installed. |
| obj->AssertReadBarrierState(); |
| } |
| if (immune_spaces_.IsInImmuneRegion(obj)) { |
| if (kCountMarkedObjects) { |
| ++mark_immune_count_; |
| } |
| DCHECK(mark_bitmap_->Test(obj)); |
| } else if (LIKELY(current_space_bitmap_->HasAddress(obj))) { |
| if (kCountMarkedObjects) { |
| ++mark_fastpath_count_; |
| } |
| if (UNLIKELY(!current_space_bitmap_->Set(obj))) { |
| PushOnMarkStack(obj); // This object was not previously marked. |
| } |
| } else { |
| if (kCountMarkedObjects) { |
| ++mark_slowpath_count_; |
| } |
| MarkObjectSlowPath visitor(this, holder, offset); |
| // TODO: We already know that the object is not in the current_space_bitmap_ but MarkBitmap::Set |
| // will check again. |
| if (!mark_bitmap_->Set(obj, visitor)) { |
| PushOnMarkStack(obj); // Was not already marked, push. |
| } |
| } |
| } |
| |
| inline void MarkSweep::PushOnMarkStack(mirror::Object* obj) { |
| if (UNLIKELY(mark_stack_->Size() >= mark_stack_->Capacity())) { |
| // Lock is not needed but is here anyways to please annotalysis. |
| MutexLock mu(Thread::Current(), mark_stack_lock_); |
| ExpandMarkStack(); |
| } |
| // The object must be pushed on to the mark stack. |
| mark_stack_->PushBack(obj); |
| } |
| |
| inline bool MarkSweep::MarkObjectParallel(mirror::Object* obj) { |
| DCHECK(obj != nullptr); |
| if (kUseBakerReadBarrier) { |
| // Verify all the objects have the correct state installed. |
| obj->AssertReadBarrierState(); |
| } |
| if (immune_spaces_.IsInImmuneRegion(obj)) { |
| DCHECK(IsMarked(obj) != nullptr); |
| return false; |
| } |
| // Try to take advantage of locality of references within a space, failing this find the space |
| // the hard way. |
| accounting::ContinuousSpaceBitmap* object_bitmap = current_space_bitmap_; |
| if (LIKELY(object_bitmap->HasAddress(obj))) { |
| return !object_bitmap->AtomicTestAndSet(obj); |
| } |
| MarkObjectSlowPath visitor(this); |
| return !mark_bitmap_->AtomicTestAndSet(obj, visitor); |
| } |
| |
| void MarkSweep::MarkHeapReference(mirror::HeapReference<mirror::Object>* ref, |
| bool do_atomic_update ATTRIBUTE_UNUSED) { |
| MarkObject(ref->AsMirrorPtr(), nullptr, MemberOffset(0)); |
| } |
| |
| // Used to mark objects when processing the mark stack. If an object is null, it is not marked. |
| inline void MarkSweep::MarkObject(mirror::Object* obj, |
| mirror::Object* holder, |
| MemberOffset offset) { |
| if (obj != nullptr) { |
| MarkObjectNonNull(obj, holder, offset); |
| } else if (kCountMarkedObjects) { |
| ++mark_null_count_; |
| } |
| } |
| |
| class MarkSweep::VerifyRootMarkedVisitor : public SingleRootVisitor { |
| public: |
| explicit VerifyRootMarkedVisitor(MarkSweep* collector) : collector_(collector) { } |
| |
| void VisitRoot(mirror::Object* root, const RootInfo& info) OVERRIDE |
| REQUIRES_SHARED(Locks::mutator_lock_, Locks::heap_bitmap_lock_) { |
| CHECK(collector_->IsMarked(root) != nullptr) << info.ToString(); |
| } |
| |
| private: |
| MarkSweep* const collector_; |
| }; |
| |
| void MarkSweep::VisitRoots(mirror::Object*** roots, |
| size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) { |
| for (size_t i = 0; i < count; ++i) { |
| MarkObjectNonNull(*roots[i]); |
| } |
| } |
| |
| void MarkSweep::VisitRoots(mirror::CompressedReference<mirror::Object>** roots, |
| size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) { |
| for (size_t i = 0; i < count; ++i) { |
| MarkObjectNonNull(roots[i]->AsMirrorPtr()); |
| } |
| } |
| |
| class MarkSweep::VerifyRootVisitor : public SingleRootVisitor { |
| public: |
| explicit VerifyRootVisitor(std::ostream& os) : os_(os) {} |
| |
| void VisitRoot(mirror::Object* root, const RootInfo& info) OVERRIDE |
| REQUIRES_SHARED(Locks::mutator_lock_, Locks::heap_bitmap_lock_) { |
| // See if the root is on any space bitmap. |
| auto* heap = Runtime::Current()->GetHeap(); |
| if (heap->GetLiveBitmap()->GetContinuousSpaceBitmap(root) == nullptr) { |
| space::LargeObjectSpace* large_object_space = heap->GetLargeObjectsSpace(); |
| if (large_object_space != nullptr && !large_object_space->Contains(root)) { |
| os_ << "Found invalid root: " << root << " " << info << std::endl; |
| } |
| } |
| } |
| |
| private: |
| std::ostream& os_; |
| }; |
| |
| void MarkSweep::VerifySuspendedThreadRoots(std::ostream& os) { |
| VerifyRootVisitor visitor(os); |
| Runtime::Current()->GetThreadList()->VisitRootsForSuspendedThreads(&visitor); |
| } |
| |
| void MarkSweep::MarkRoots(Thread* self) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| if (Locks::mutator_lock_->IsExclusiveHeld(self)) { |
| // If we exclusively hold the mutator lock, all threads must be suspended. |
| Runtime::Current()->VisitRoots(this); |
| RevokeAllThreadLocalAllocationStacks(self); |
| } else { |
| MarkRootsCheckpoint(self, kRevokeRosAllocThreadLocalBuffersAtCheckpoint); |
| // At this point the live stack should no longer have any mutators which push into it. |
| MarkNonThreadRoots(); |
| MarkConcurrentRoots( |
| static_cast<VisitRootFlags>(kVisitRootFlagAllRoots | kVisitRootFlagStartLoggingNewRoots)); |
| } |
| } |
| |
| void MarkSweep::MarkNonThreadRoots() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Runtime::Current()->VisitNonThreadRoots(this); |
| } |
| |
| void MarkSweep::MarkConcurrentRoots(VisitRootFlags flags) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| // Visit all runtime roots and clear dirty flags. |
| Runtime::Current()->VisitConcurrentRoots(this, flags); |
| } |
| |
| class MarkSweep::DelayReferenceReferentVisitor { |
| public: |
| explicit DelayReferenceReferentVisitor(MarkSweep* collector) : collector_(collector) {} |
| |
| void operator()(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) const |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| collector_->DelayReferenceReferent(klass, ref); |
| } |
| |
| private: |
| MarkSweep* const collector_; |
| }; |
| |
| template <bool kUseFinger = false> |
| class MarkSweep::MarkStackTask : public Task { |
| public: |
| MarkStackTask(ThreadPool* thread_pool, |
| MarkSweep* mark_sweep, |
| size_t mark_stack_size, |
| StackReference<mirror::Object>* mark_stack) |
| : mark_sweep_(mark_sweep), |
| thread_pool_(thread_pool), |
| mark_stack_pos_(mark_stack_size) { |
| // We may have to copy part of an existing mark stack when another mark stack overflows. |
| if (mark_stack_size != 0) { |
| DCHECK(mark_stack != nullptr); |
| // TODO: Check performance? |
| std::copy(mark_stack, mark_stack + mark_stack_size, mark_stack_); |
| } |
| if (kCountTasks) { |
| ++mark_sweep_->work_chunks_created_; |
| } |
| } |
| |
| static const size_t kMaxSize = 1 * KB; |
| |
| protected: |
| class MarkObjectParallelVisitor { |
| public: |
| ALWAYS_INLINE MarkObjectParallelVisitor(MarkStackTask<kUseFinger>* chunk_task, |
| MarkSweep* mark_sweep) |
| : chunk_task_(chunk_task), mark_sweep_(mark_sweep) {} |
| |
| ALWAYS_INLINE void operator()(mirror::Object* obj, |
| MemberOffset offset, |
| bool is_static ATTRIBUTE_UNUSED) const |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| Mark(obj->GetFieldObject<mirror::Object>(offset)); |
| } |
| |
| 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_) { |
| if (kCheckLocks) { |
| Locks::mutator_lock_->AssertSharedHeld(Thread::Current()); |
| Locks::heap_bitmap_lock_->AssertExclusiveHeld(Thread::Current()); |
| } |
| Mark(root->AsMirrorPtr()); |
| } |
| |
| private: |
| ALWAYS_INLINE void Mark(mirror::Object* ref) const REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (ref != nullptr && mark_sweep_->MarkObjectParallel(ref)) { |
| if (kUseFinger) { |
| std::atomic_thread_fence(std::memory_order_seq_cst); |
| if (reinterpret_cast<uintptr_t>(ref) >= |
| static_cast<uintptr_t>(mark_sweep_->atomic_finger_.LoadRelaxed())) { |
| return; |
| } |
| } |
| chunk_task_->MarkStackPush(ref); |
| } |
| } |
| |
| MarkStackTask<kUseFinger>* const chunk_task_; |
| MarkSweep* const mark_sweep_; |
| }; |
| |
| class ScanObjectParallelVisitor { |
| public: |
| ALWAYS_INLINE explicit ScanObjectParallelVisitor(MarkStackTask<kUseFinger>* chunk_task) |
| : chunk_task_(chunk_task) {} |
| |
| // No thread safety analysis since multiple threads will use this visitor. |
| void operator()(mirror::Object* obj) const |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| MarkSweep* const mark_sweep = chunk_task_->mark_sweep_; |
| MarkObjectParallelVisitor mark_visitor(chunk_task_, mark_sweep); |
| DelayReferenceReferentVisitor ref_visitor(mark_sweep); |
| mark_sweep->ScanObjectVisit(obj, mark_visitor, ref_visitor); |
| } |
| |
| private: |
| MarkStackTask<kUseFinger>* const chunk_task_; |
| }; |
| |
| virtual ~MarkStackTask() { |
| // Make sure that we have cleared our mark stack. |
| DCHECK_EQ(mark_stack_pos_, 0U); |
| if (kCountTasks) { |
| ++mark_sweep_->work_chunks_deleted_; |
| } |
| } |
| |
| MarkSweep* const mark_sweep_; |
| ThreadPool* const thread_pool_; |
| // Thread local mark stack for this task. |
| StackReference<mirror::Object> mark_stack_[kMaxSize]; |
| // Mark stack position. |
| size_t mark_stack_pos_; |
| |
| ALWAYS_INLINE void MarkStackPush(mirror::Object* obj) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (UNLIKELY(mark_stack_pos_ == kMaxSize)) { |
| // Mark stack overflow, give 1/2 the stack to the thread pool as a new work task. |
| mark_stack_pos_ /= 2; |
| auto* task = new MarkStackTask(thread_pool_, |
| mark_sweep_, |
| kMaxSize - mark_stack_pos_, |
| mark_stack_ + mark_stack_pos_); |
| thread_pool_->AddTask(Thread::Current(), task); |
| } |
| DCHECK(obj != nullptr); |
| DCHECK_LT(mark_stack_pos_, kMaxSize); |
| mark_stack_[mark_stack_pos_++].Assign(obj); |
| } |
| |
| virtual void Finalize() { |
| delete this; |
| } |
| |
| // Scans all of the objects |
| virtual void Run(Thread* self ATTRIBUTE_UNUSED) |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| ScanObjectParallelVisitor visitor(this); |
| // TODO: Tune this. |
| static const size_t kFifoSize = 4; |
| BoundedFifoPowerOfTwo<mirror::Object*, kFifoSize> prefetch_fifo; |
| for (;;) { |
| mirror::Object* obj = nullptr; |
| if (kUseMarkStackPrefetch) { |
| while (mark_stack_pos_ != 0 && prefetch_fifo.size() < kFifoSize) { |
| mirror::Object* const mark_stack_obj = mark_stack_[--mark_stack_pos_].AsMirrorPtr(); |
| DCHECK(mark_stack_obj != nullptr); |
| __builtin_prefetch(mark_stack_obj); |
| prefetch_fifo.push_back(mark_stack_obj); |
| } |
| if (UNLIKELY(prefetch_fifo.empty())) { |
| break; |
| } |
| obj = prefetch_fifo.front(); |
| prefetch_fifo.pop_front(); |
| } else { |
| if (UNLIKELY(mark_stack_pos_ == 0)) { |
| break; |
| } |
| obj = mark_stack_[--mark_stack_pos_].AsMirrorPtr(); |
| } |
| DCHECK(obj != nullptr); |
| visitor(obj); |
| } |
| } |
| }; |
| |
| class MarkSweep::CardScanTask : public MarkStackTask<false> { |
| public: |
| CardScanTask(ThreadPool* thread_pool, |
| MarkSweep* mark_sweep, |
| accounting::ContinuousSpaceBitmap* bitmap, |
| uint8_t* begin, |
| uint8_t* end, |
| uint8_t minimum_age, |
| size_t mark_stack_size, |
| StackReference<mirror::Object>* mark_stack_obj, |
| bool clear_card) |
| : MarkStackTask<false>(thread_pool, mark_sweep, mark_stack_size, mark_stack_obj), |
| bitmap_(bitmap), |
| begin_(begin), |
| end_(end), |
| minimum_age_(minimum_age), |
| clear_card_(clear_card) {} |
| |
| protected: |
| accounting::ContinuousSpaceBitmap* const bitmap_; |
| uint8_t* const begin_; |
| uint8_t* const end_; |
| const uint8_t minimum_age_; |
| const bool clear_card_; |
| |
| virtual void Finalize() { |
| delete this; |
| } |
| |
| virtual void Run(Thread* self) NO_THREAD_SAFETY_ANALYSIS { |
| ScanObjectParallelVisitor visitor(this); |
| accounting::CardTable* card_table = mark_sweep_->GetHeap()->GetCardTable(); |
| size_t cards_scanned = clear_card_ |
| ? card_table->Scan<true>(bitmap_, begin_, end_, visitor, minimum_age_) |
| : card_table->Scan<false>(bitmap_, begin_, end_, visitor, minimum_age_); |
| VLOG(heap) << "Parallel scanning cards " << reinterpret_cast<void*>(begin_) << " - " |
| << reinterpret_cast<void*>(end_) << " = " << cards_scanned; |
| // Finish by emptying our local mark stack. |
| MarkStackTask::Run(self); |
| } |
| }; |
| |
| size_t MarkSweep::GetThreadCount(bool paused) const { |
| // Use less threads if we are in a background state (non jank perceptible) since we want to leave |
| // more CPU time for the foreground apps. |
| if (heap_->GetThreadPool() == nullptr || !Runtime::Current()->InJankPerceptibleProcessState()) { |
| return 1; |
| } |
| return (paused ? heap_->GetParallelGCThreadCount() : heap_->GetConcGCThreadCount()) + 1; |
| } |
| |
| void MarkSweep::ScanGrayObjects(bool paused, uint8_t minimum_age) { |
| accounting::CardTable* card_table = GetHeap()->GetCardTable(); |
| ThreadPool* thread_pool = GetHeap()->GetThreadPool(); |
| size_t thread_count = GetThreadCount(paused); |
| // The parallel version with only one thread is faster for card scanning, TODO: fix. |
| if (kParallelCardScan && thread_count > 1) { |
| Thread* self = Thread::Current(); |
| // Can't have a different split for each space since multiple spaces can have their cards being |
| // scanned at the same time. |
| TimingLogger::ScopedTiming t(paused ? "(Paused)ScanGrayObjects" : __FUNCTION__, |
| GetTimings()); |
| // Try to take some of the mark stack since we can pass this off to the worker tasks. |
| StackReference<mirror::Object>* mark_stack_begin = mark_stack_->Begin(); |
| StackReference<mirror::Object>* mark_stack_end = mark_stack_->End(); |
| const size_t mark_stack_size = mark_stack_end - mark_stack_begin; |
| // Estimated number of work tasks we will create. |
| const size_t mark_stack_tasks = GetHeap()->GetContinuousSpaces().size() * thread_count; |
| DCHECK_NE(mark_stack_tasks, 0U); |
| const size_t mark_stack_delta = std::min(CardScanTask::kMaxSize / 2, |
| mark_stack_size / mark_stack_tasks + 1); |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if (space->GetMarkBitmap() == nullptr) { |
| continue; |
| } |
| uint8_t* card_begin = space->Begin(); |
| uint8_t* card_end = space->End(); |
| // Align up the end address. For example, the image space's end |
| // may not be card-size-aligned. |
| card_end = AlignUp(card_end, accounting::CardTable::kCardSize); |
| DCHECK_ALIGNED(card_begin, accounting::CardTable::kCardSize); |
| DCHECK_ALIGNED(card_end, accounting::CardTable::kCardSize); |
| // Calculate how many bytes of heap we will scan, |
| const size_t address_range = card_end - card_begin; |
| // Calculate how much address range each task gets. |
| const size_t card_delta = RoundUp(address_range / thread_count + 1, |
| accounting::CardTable::kCardSize); |
| // If paused and the space is neither zygote nor image space, we could clear the dirty |
| // cards to avoid accumulating them to increase card scanning load in the following GC |
| // cycles. We need to keep dirty cards of image space and zygote space in order to track |
| // references to the other spaces. |
| bool clear_card = paused && !space->IsZygoteSpace() && !space->IsImageSpace(); |
| // Create the worker tasks for this space. |
| while (card_begin != card_end) { |
| // Add a range of cards. |
| size_t addr_remaining = card_end - card_begin; |
| size_t card_increment = std::min(card_delta, addr_remaining); |
| // Take from the back of the mark stack. |
| size_t mark_stack_remaining = mark_stack_end - mark_stack_begin; |
| size_t mark_stack_increment = std::min(mark_stack_delta, mark_stack_remaining); |
| mark_stack_end -= mark_stack_increment; |
| mark_stack_->PopBackCount(static_cast<int32_t>(mark_stack_increment)); |
| DCHECK_EQ(mark_stack_end, mark_stack_->End()); |
| // Add the new task to the thread pool. |
| auto* task = new CardScanTask(thread_pool, |
| this, |
| space->GetMarkBitmap(), |
| card_begin, |
| card_begin + card_increment, |
| minimum_age, |
| mark_stack_increment, |
| mark_stack_end, |
| clear_card); |
| thread_pool->AddTask(self, task); |
| card_begin += card_increment; |
| } |
| } |
| |
| // Note: the card scan below may dirty new cards (and scan them) |
| // as a side effect when a Reference object is encountered and |
| // queued during the marking. See b/11465268. |
| thread_pool->SetMaxActiveWorkers(thread_count - 1); |
| thread_pool->StartWorkers(self); |
| thread_pool->Wait(self, true, true); |
| thread_pool->StopWorkers(self); |
| } else { |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if (space->GetMarkBitmap() != nullptr) { |
| // Image spaces are handled properly since live == marked for them. |
| const char* name = nullptr; |
| switch (space->GetGcRetentionPolicy()) { |
| case space::kGcRetentionPolicyNeverCollect: |
| name = paused ? "(Paused)ScanGrayImageSpaceObjects" : "ScanGrayImageSpaceObjects"; |
| break; |
| case space::kGcRetentionPolicyFullCollect: |
| name = paused ? "(Paused)ScanGrayZygoteSpaceObjects" : "ScanGrayZygoteSpaceObjects"; |
| break; |
| case space::kGcRetentionPolicyAlwaysCollect: |
| name = paused ? "(Paused)ScanGrayAllocSpaceObjects" : "ScanGrayAllocSpaceObjects"; |
| break; |
| default: |
| LOG(FATAL) << "Unreachable"; |
| UNREACHABLE(); |
| } |
| TimingLogger::ScopedTiming t(name, GetTimings()); |
| ScanObjectVisitor visitor(this); |
| bool clear_card = paused && !space->IsZygoteSpace() && !space->IsImageSpace(); |
| if (clear_card) { |
| card_table->Scan<true>(space->GetMarkBitmap(), |
| space->Begin(), |
| space->End(), |
| visitor, |
| minimum_age); |
| } else { |
| card_table->Scan<false>(space->GetMarkBitmap(), |
| space->Begin(), |
| space->End(), |
| visitor, |
| minimum_age); |
| } |
| } |
| } |
| } |
| } |
| |
| class MarkSweep::RecursiveMarkTask : public MarkStackTask<false> { |
| public: |
| RecursiveMarkTask(ThreadPool* thread_pool, |
| MarkSweep* mark_sweep, |
| accounting::ContinuousSpaceBitmap* bitmap, |
| uintptr_t begin, |
| uintptr_t end) |
| : MarkStackTask<false>(thread_pool, mark_sweep, 0, nullptr), |
| bitmap_(bitmap), |
| begin_(begin), |
| end_(end) {} |
| |
| protected: |
| accounting::ContinuousSpaceBitmap* const bitmap_; |
| const uintptr_t begin_; |
| const uintptr_t end_; |
| |
| virtual void Finalize() { |
| delete this; |
| } |
| |
| // Scans all of the objects |
| virtual void Run(Thread* self) NO_THREAD_SAFETY_ANALYSIS { |
| ScanObjectParallelVisitor visitor(this); |
| bitmap_->VisitMarkedRange(begin_, end_, visitor); |
| // Finish by emptying our local mark stack. |
| MarkStackTask::Run(self); |
| } |
| }; |
| |
| // Populates the mark stack based on the set of marked objects and |
| // recursively marks until the mark stack is emptied. |
| void MarkSweep::RecursiveMark() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| // RecursiveMark will build the lists of known instances of the Reference classes. See |
| // DelayReferenceReferent for details. |
| if (kUseRecursiveMark) { |
| const bool partial = GetGcType() == kGcTypePartial; |
| ScanObjectVisitor scan_visitor(this); |
| auto* self = Thread::Current(); |
| ThreadPool* thread_pool = heap_->GetThreadPool(); |
| size_t thread_count = GetThreadCount(false); |
| const bool parallel = kParallelRecursiveMark && thread_count > 1; |
| mark_stack_->Reset(); |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if ((space->GetGcRetentionPolicy() == space::kGcRetentionPolicyAlwaysCollect) || |
| (!partial && space->GetGcRetentionPolicy() == space::kGcRetentionPolicyFullCollect)) { |
| current_space_bitmap_ = space->GetMarkBitmap(); |
| if (current_space_bitmap_ == nullptr) { |
| continue; |
| } |
| if (parallel) { |
| // We will use the mark stack the future. |
| // CHECK(mark_stack_->IsEmpty()); |
| // This function does not handle heap end increasing, so we must use the space end. |
| uintptr_t begin = reinterpret_cast<uintptr_t>(space->Begin()); |
| uintptr_t end = reinterpret_cast<uintptr_t>(space->End()); |
| atomic_finger_.StoreRelaxed(AtomicInteger::MaxValue()); |
| |
| // Create a few worker tasks. |
| const size_t n = thread_count * 2; |
| while (begin != end) { |
| uintptr_t start = begin; |
| uintptr_t delta = (end - begin) / n; |
| delta = RoundUp(delta, KB); |
| if (delta < 16 * KB) delta = end - begin; |
| begin += delta; |
| auto* task = new RecursiveMarkTask(thread_pool, |
| this, |
| current_space_bitmap_, |
| start, |
| begin); |
| thread_pool->AddTask(self, task); |
| } |
| thread_pool->SetMaxActiveWorkers(thread_count - 1); |
| thread_pool->StartWorkers(self); |
| thread_pool->Wait(self, true, true); |
| thread_pool->StopWorkers(self); |
| } else { |
| // This function does not handle heap end increasing, so we must use the space end. |
| uintptr_t begin = reinterpret_cast<uintptr_t>(space->Begin()); |
| uintptr_t end = reinterpret_cast<uintptr_t>(space->End()); |
| current_space_bitmap_->VisitMarkedRange(begin, end, scan_visitor); |
| } |
| } |
| } |
| } |
| ProcessMarkStack(false); |
| } |
| |
| void MarkSweep::RecursiveMarkDirtyObjects(bool paused, uint8_t minimum_age) { |
| ScanGrayObjects(paused, minimum_age); |
| ProcessMarkStack(paused); |
| } |
| |
| void MarkSweep::ReMarkRoots() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| Locks::mutator_lock_->AssertExclusiveHeld(Thread::Current()); |
| Runtime::Current()->VisitRoots(this, static_cast<VisitRootFlags>( |
| kVisitRootFlagNewRoots | kVisitRootFlagStopLoggingNewRoots | kVisitRootFlagClearRootLog)); |
| if (kVerifyRootsMarked) { |
| TimingLogger::ScopedTiming t2("(Paused)VerifyRoots", GetTimings()); |
| VerifyRootMarkedVisitor visitor(this); |
| Runtime::Current()->VisitRoots(&visitor); |
| } |
| } |
| |
| void MarkSweep::SweepSystemWeaks(Thread* self) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| ReaderMutexLock mu(self, *Locks::heap_bitmap_lock_); |
| Runtime::Current()->SweepSystemWeaks(this); |
| } |
| |
| class MarkSweep::VerifySystemWeakVisitor : public IsMarkedVisitor { |
| public: |
| explicit VerifySystemWeakVisitor(MarkSweep* mark_sweep) : mark_sweep_(mark_sweep) {} |
| |
| virtual mirror::Object* IsMarked(mirror::Object* obj) |
| OVERRIDE |
| REQUIRES_SHARED(Locks::mutator_lock_, Locks::heap_bitmap_lock_) { |
| mark_sweep_->VerifyIsLive(obj); |
| return obj; |
| } |
| |
| MarkSweep* const mark_sweep_; |
| }; |
| |
| void MarkSweep::VerifyIsLive(const mirror::Object* obj) { |
| if (!heap_->GetLiveBitmap()->Test(obj)) { |
| // TODO: Consider live stack? Has this code bitrotted? |
| CHECK(!heap_->allocation_stack_->Contains(obj)) |
| << "Found dead object " << obj << "\n" << heap_->DumpSpaces(); |
| } |
| } |
| |
| void MarkSweep::VerifySystemWeaks() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| // Verify system weaks, uses a special object visitor which returns the input object. |
| VerifySystemWeakVisitor visitor(this); |
| Runtime::Current()->SweepSystemWeaks(&visitor); |
| } |
| |
| class MarkSweep::CheckpointMarkThreadRoots : public Closure, public RootVisitor { |
| public: |
| CheckpointMarkThreadRoots(MarkSweep* mark_sweep, |
| bool revoke_ros_alloc_thread_local_buffers_at_checkpoint) |
| : mark_sweep_(mark_sweep), |
| revoke_ros_alloc_thread_local_buffers_at_checkpoint_( |
| revoke_ros_alloc_thread_local_buffers_at_checkpoint) { |
| } |
| |
| void VisitRoots(mirror::Object*** roots, size_t count, const RootInfo& info ATTRIBUTE_UNUSED) |
| OVERRIDE REQUIRES_SHARED(Locks::mutator_lock_) |
| REQUIRES(Locks::heap_bitmap_lock_) { |
| for (size_t i = 0; i < count; ++i) { |
| mark_sweep_->MarkObjectNonNullParallel(*roots[i]); |
| } |
| } |
| |
| void VisitRoots(mirror::CompressedReference<mirror::Object>** roots, |
| size_t count, |
| const RootInfo& info ATTRIBUTE_UNUSED) |
| OVERRIDE REQUIRES_SHARED(Locks::mutator_lock_) |
| REQUIRES(Locks::heap_bitmap_lock_) { |
| for (size_t i = 0; i < count; ++i) { |
| mark_sweep_->MarkObjectNonNullParallel(roots[i]->AsMirrorPtr()); |
| } |
| } |
| |
| virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS { |
| ScopedTrace trace("Marking thread roots"); |
| // Note: self is not necessarily equal to thread since thread may be suspended. |
| Thread* const self = Thread::Current(); |
| CHECK(thread == self || thread->IsSuspended() || thread->GetState() == kWaitingPerformingGc) |
| << thread->GetState() << " thread " << thread << " self " << self; |
| thread->VisitRoots(this, kVisitRootFlagAllRoots); |
| if (revoke_ros_alloc_thread_local_buffers_at_checkpoint_) { |
| ScopedTrace trace2("RevokeRosAllocThreadLocalBuffers"); |
| mark_sweep_->GetHeap()->RevokeRosAllocThreadLocalBuffers(thread); |
| } |
| // If thread is a running mutator, then act on behalf of the garbage collector. |
| // See the code in ThreadList::RunCheckpoint. |
| mark_sweep_->GetBarrier().Pass(self); |
| } |
| |
| private: |
| MarkSweep* const mark_sweep_; |
| const bool revoke_ros_alloc_thread_local_buffers_at_checkpoint_; |
| }; |
| |
| void MarkSweep::MarkRootsCheckpoint(Thread* self, |
| bool revoke_ros_alloc_thread_local_buffers_at_checkpoint) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| CheckpointMarkThreadRoots check_point(this, revoke_ros_alloc_thread_local_buffers_at_checkpoint); |
| ThreadList* thread_list = Runtime::Current()->GetThreadList(); |
| // Request the check point is run on all threads returning a count of the threads that must |
| // run through the barrier including self. |
| size_t barrier_count = thread_list->RunCheckpoint(&check_point); |
| // Release locks then wait for all mutator threads to pass the barrier. |
| // If there are no threads to wait which implys that all the checkpoint functions are finished, |
| // then no need to release locks. |
| if (barrier_count == 0) { |
| return; |
| } |
| Locks::heap_bitmap_lock_->ExclusiveUnlock(self); |
| Locks::mutator_lock_->SharedUnlock(self); |
| { |
| ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun); |
| gc_barrier_->Increment(self, barrier_count); |
| } |
| Locks::mutator_lock_->SharedLock(self); |
| Locks::heap_bitmap_lock_->ExclusiveLock(self); |
| } |
| |
| void MarkSweep::SweepArray(accounting::ObjectStack* allocations, bool swap_bitmaps) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, 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(); |
| // Change the order to ensure that the non-moving space last swept as an optimization. |
| std::vector<space::ContinuousSpace*> sweep_spaces; |
| space::ContinuousSpace* non_moving_space = nullptr; |
| for (space::ContinuousSpace* space : heap_->GetContinuousSpaces()) { |
| if (space->IsAllocSpace() && |
| !immune_spaces_.ContainsSpace(space) && |
| space->GetLiveBitmap() != nullptr) { |
| if (space == heap_->GetNonMovingSpace()) { |
| non_moving_space = space; |
| } else { |
| sweep_spaces.push_back(space); |
| } |
| } |
| } |
| // Unlikely to sweep a significant amount of non_movable objects, so we do these after the after |
| // the other alloc spaces as an optimization. |
| if (non_moving_space != nullptr) { |
| sweep_spaces.push_back(non_moving_space); |
| } |
| // Start by sweeping the continuous spaces. |
| for (space::ContinuousSpace* space : sweep_spaces) { |
| 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 MarkSweep::Sweep(bool swap_bitmaps) { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| // Ensure that nobody inserted items in the live stack after we swapped the stacks. |
| CHECK_GE(live_stack_freeze_size_, GetHeap()->GetLiveStack()->Size()); |
| { |
| TimingLogger::ScopedTiming t2("MarkAllocStackAsLive", GetTimings()); |
| // Mark everything allocated since the last as GC live so that we can sweep concurrently, |
| // knowing that new allocations won't be marked as live. |
| accounting::ObjectStack* live_stack = heap_->GetLiveStack(); |
| heap_->MarkAllocStackAsLive(live_stack); |
| live_stack->Reset(); |
| DCHECK(mark_stack_->IsEmpty()); |
| } |
| for (const auto& space : GetHeap()->GetContinuousSpaces()) { |
| if (space->IsContinuousMemMapAllocSpace()) { |
| space::ContinuousMemMapAllocSpace* alloc_space = space->AsContinuousMemMapAllocSpace(); |
| TimingLogger::ScopedTiming split( |
| alloc_space->IsZygoteSpace() ? "SweepZygoteSpace" : "SweepMallocSpace", |
| GetTimings()); |
| RecordFree(alloc_space->Sweep(swap_bitmaps)); |
| } |
| } |
| SweepLargeObjects(swap_bitmaps); |
| } |
| |
| void MarkSweep::SweepLargeObjects(bool swap_bitmaps) { |
| space::LargeObjectSpace* los = heap_->GetLargeObjectsSpace(); |
| if (los != nullptr) { |
| TimingLogger::ScopedTiming split(__FUNCTION__, GetTimings()); |
| RecordFreeLOS(los->Sweep(swap_bitmaps)); |
| } |
| } |
| |
| // Process the "referent" field lin a java.lang.ref.Reference. If the referent has not yet been |
| // marked, put it on the appropriate list in the heap for later processing. |
| void MarkSweep::DelayReferenceReferent(ObjPtr<mirror::Class> klass, ObjPtr<mirror::Reference> ref) { |
| heap_->GetReferenceProcessor()->DelayReferenceReferent(klass, ref, this); |
| } |
| |
| class MarkVisitor { |
| public: |
| ALWAYS_INLINE explicit MarkVisitor(MarkSweep* const mark_sweep) : mark_sweep_(mark_sweep) {} |
| |
| ALWAYS_INLINE void operator()(mirror::Object* obj, |
| MemberOffset offset, |
| bool is_static ATTRIBUTE_UNUSED) const |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (kCheckLocks) { |
| Locks::mutator_lock_->AssertSharedHeld(Thread::Current()); |
| Locks::heap_bitmap_lock_->AssertExclusiveHeld(Thread::Current()); |
| } |
| mark_sweep_->MarkObject(obj->GetFieldObject<mirror::Object>(offset), obj, offset); |
| } |
| |
| void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (!root->IsNull()) { |
| VisitRoot(root); |
| } |
| } |
| |
| void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const |
| REQUIRES(Locks::heap_bitmap_lock_) |
| REQUIRES_SHARED(Locks::mutator_lock_) { |
| if (kCheckLocks) { |
| Locks::mutator_lock_->AssertSharedHeld(Thread::Current()); |
| Locks::heap_bitmap_lock_->AssertExclusiveHeld(Thread::Current()); |
| } |
| mark_sweep_->MarkObject(root->AsMirrorPtr()); |
| } |
| |
| private: |
| MarkSweep* const mark_sweep_; |
| }; |
| |
| // Scans an object reference. Determines the type of the reference |
| // and dispatches to a specialized scanning routine. |
| void MarkSweep::ScanObject(mirror::Object* obj) { |
| MarkVisitor mark_visitor(this); |
| DelayReferenceReferentVisitor ref_visitor(this); |
| ScanObjectVisit(obj, mark_visitor, ref_visitor); |
| } |
| |
| void MarkSweep::ProcessMarkStackParallel(size_t thread_count) { |
| Thread* self = Thread::Current(); |
| ThreadPool* thread_pool = GetHeap()->GetThreadPool(); |
| const size_t chunk_size = std::min(mark_stack_->Size() / thread_count + 1, |
| static_cast<size_t>(MarkStackTask<false>::kMaxSize)); |
| CHECK_GT(chunk_size, 0U); |
| // Split the current mark stack up into work tasks. |
| for (auto* it = mark_stack_->Begin(), *end = mark_stack_->End(); it < end; ) { |
| const size_t delta = std::min(static_cast<size_t>(end - it), chunk_size); |
| thread_pool->AddTask(self, new MarkStackTask<false>(thread_pool, this, delta, it)); |
| it += delta; |
| } |
| thread_pool->SetMaxActiveWorkers(thread_count - 1); |
| thread_pool->StartWorkers(self); |
| thread_pool->Wait(self, true, true); |
| thread_pool->StopWorkers(self); |
| mark_stack_->Reset(); |
| CHECK_EQ(work_chunks_created_.LoadSequentiallyConsistent(), |
| work_chunks_deleted_.LoadSequentiallyConsistent()) |
| << " some of the work chunks were leaked"; |
| } |
| |
| // Scan anything that's on the mark stack. |
| void MarkSweep::ProcessMarkStack(bool paused) { |
| TimingLogger::ScopedTiming t(paused ? "(Paused)ProcessMarkStack" : __FUNCTION__, GetTimings()); |
| size_t thread_count = GetThreadCount(paused); |
| if (kParallelProcessMarkStack && thread_count > 1 && |
| mark_stack_->Size() >= kMinimumParallelMarkStackSize) { |
| ProcessMarkStackParallel(thread_count); |
| } else { |
| // TODO: Tune this. |
| static const size_t kFifoSize = 4; |
| BoundedFifoPowerOfTwo<mirror::Object*, kFifoSize> prefetch_fifo; |
| for (;;) { |
| mirror::Object* obj = nullptr; |
| if (kUseMarkStackPrefetch) { |
| while (!mark_stack_->IsEmpty() && prefetch_fifo.size() < kFifoSize) { |
| mirror::Object* mark_stack_obj = mark_stack_->PopBack(); |
| DCHECK(mark_stack_obj != nullptr); |
| __builtin_prefetch(mark_stack_obj); |
| prefetch_fifo.push_back(mark_stack_obj); |
| } |
| if (prefetch_fifo.empty()) { |
| break; |
| } |
| obj = prefetch_fifo.front(); |
| prefetch_fifo.pop_front(); |
| } else { |
| if (mark_stack_->IsEmpty()) { |
| break; |
| } |
| obj = mark_stack_->PopBack(); |
| } |
| DCHECK(obj != nullptr); |
| ScanObject(obj); |
| } |
| } |
| } |
| |
| inline mirror::Object* MarkSweep::IsMarked(mirror::Object* object) { |
| if (immune_spaces_.IsInImmuneRegion(object)) { |
| return object; |
| } |
| if (current_space_bitmap_->HasAddress(object)) { |
| return current_space_bitmap_->Test(object) ? object : nullptr; |
| } |
| return mark_bitmap_->Test(object) ? object : nullptr; |
| } |
| |
| void MarkSweep::FinishPhase() { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| if (kCountScannedTypes) { |
| VLOG(gc) |
| << "MarkSweep scanned" |
| << " no reference objects=" << no_reference_class_count_.LoadRelaxed() |
| << " normal objects=" << normal_count_.LoadRelaxed() |
| << " classes=" << class_count_.LoadRelaxed() |
| << " object arrays=" << object_array_count_.LoadRelaxed() |
| << " references=" << reference_count_.LoadRelaxed() |
| << " other=" << other_count_.LoadRelaxed(); |
| } |
| if (kCountTasks) { |
| VLOG(gc) << "Total number of work chunks allocated: " << work_chunks_created_.LoadRelaxed(); |
| } |
| if (kMeasureOverhead) { |
| VLOG(gc) << "Overhead time " << PrettyDuration(overhead_time_.LoadRelaxed()); |
| } |
| if (kProfileLargeObjects) { |
| VLOG(gc) << "Large objects tested " << large_object_test_.LoadRelaxed() |
| << " marked " << large_object_mark_.LoadRelaxed(); |
| } |
| if (kCountMarkedObjects) { |
| VLOG(gc) << "Marked: null=" << mark_null_count_.LoadRelaxed() |
| << " immune=" << mark_immune_count_.LoadRelaxed() |
| << " fastpath=" << mark_fastpath_count_.LoadRelaxed() |
| << " slowpath=" << mark_slowpath_count_.LoadRelaxed(); |
| } |
| CHECK(mark_stack_->IsEmpty()); // Ensure that the mark stack is empty. |
| mark_stack_->Reset(); |
| Thread* const self = Thread::Current(); |
| ReaderMutexLock mu(self, *Locks::mutator_lock_); |
| WriterMutexLock mu2(self, *Locks::heap_bitmap_lock_); |
| heap_->ClearMarkedObjects(); |
| } |
| |
| void MarkSweep::RevokeAllThreadLocalBuffers() { |
| if (kRevokeRosAllocThreadLocalBuffersAtCheckpoint && IsConcurrent()) { |
| // If concurrent, rosalloc thread-local buffers are revoked at the |
| // thread checkpoint. Bump pointer space thread-local buffers must |
| // not be in use. |
| GetHeap()->AssertAllBumpPointerSpaceThreadLocalBuffersAreRevoked(); |
| } else { |
| TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings()); |
| GetHeap()->RevokeAllThreadLocalBuffers(); |
| } |
| } |
| |
| } // namespace collector |
| } // namespace gc |
| } // namespace art |