| // Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| #include "vm/heap/scavenger.h" |
| |
| #include "platform/assert.h" |
| #include "platform/leak_sanitizer.h" |
| #include "vm/class_id.h" |
| #include "vm/compiler/runtime_api.h" |
| #include "vm/dart.h" |
| #include "vm/dart_api_state.h" |
| #include "vm/flag_list.h" |
| #include "vm/flags.h" |
| #include "vm/heap/become.h" |
| #include "vm/heap/gc_shared.h" |
| #include "vm/heap/marker.h" |
| #include "vm/heap/pages.h" |
| #include "vm/heap/pointer_block.h" |
| #include "vm/heap/safepoint.h" |
| #include "vm/heap/verifier.h" |
| #include "vm/heap/weak_table.h" |
| #include "vm/isolate.h" |
| #include "vm/lockers.h" |
| #include "vm/log.h" |
| #include "vm/longjump.h" |
| #include "vm/object.h" |
| #include "vm/object_id_ring.h" |
| #include "vm/object_set.h" |
| #include "vm/port.h" |
| #include "vm/stack_frame.h" |
| #include "vm/tagged_pointer.h" |
| #include "vm/thread_barrier.h" |
| #include "vm/timeline.h" |
| #include "vm/visitor.h" |
| |
| namespace dart { |
| |
| DEFINE_FLAG(int, |
| early_tenuring_threshold, |
| 66, |
| "When more than this percentage of promotion candidates survive, " |
| "promote all survivors of next scavenge."); |
| DEFINE_FLAG(int, |
| new_gen_garbage_threshold, |
| 90, |
| "Grow new gen when less than this percentage is garbage."); |
| DEFINE_FLAG(int, new_gen_growth_factor, 2, "Grow new gen by this factor."); |
| |
| // Scavenger uses the kCardRememberedBit to distinguish forwarded and |
| // non-forwarded objects. We must choose a bit that is clear for all new-space |
| // object headers, and which doesn't intersect with the target address because |
| // of object alignment. |
| enum { |
| kForwardingMask = 1 << UntaggedObject::kCardRememberedBit, |
| kNotForwarded = 0, |
| kForwarded = kForwardingMask, |
| }; |
| |
| // If the forwarded bit and pointer tag bit are the same, we can avoid a few |
| // conversions. |
| COMPILE_ASSERT(static_cast<uword>(kForwarded) == |
| static_cast<uword>(kHeapObjectTag)); |
| |
| DART_FORCE_INLINE |
| static bool IsForwarding(uword header) { |
| uword bits = header & kForwardingMask; |
| ASSERT((bits == kNotForwarded) || (bits == kForwarded)); |
| return bits == kForwarded; |
| } |
| |
| DART_FORCE_INLINE |
| static ObjectPtr ForwardedObj(uword header) { |
| ASSERT(IsForwarding(header)); |
| return static_cast<ObjectPtr>(header); |
| } |
| |
| DART_FORCE_INLINE |
| static uword ForwardingHeader(ObjectPtr target) { |
| uword result = static_cast<uword>(target); |
| ASSERT(IsForwarding(result)); |
| return result; |
| } |
| |
| // Races: The first word in the copied region is a header word that may be |
| // updated by the scavenger worker in another thread, so we might copy either |
| // the original object header or an installed forwarding pointer. This race is |
| // harmless because if we copy the installed forwarding pointer, the scavenge |
| // worker in the current thread will abandon this copy. We do not mark the loads |
| // here as relaxed so the C++ compiler still has the freedom to reorder them. |
| NO_SANITIZE_THREAD |
| static void objcpy(void* dst, const void* src, size_t size) { |
| // A mem copy specialized for objects. We can assume: |
| // - dst and src do not overlap |
| ASSERT( |
| (reinterpret_cast<uword>(dst) + size <= reinterpret_cast<uword>(src)) || |
| (reinterpret_cast<uword>(src) + size <= reinterpret_cast<uword>(dst))); |
| // - dst and src are word aligned |
| ASSERT(Utils::IsAligned(reinterpret_cast<uword>(dst), sizeof(uword))); |
| ASSERT(Utils::IsAligned(reinterpret_cast<uword>(src), sizeof(uword))); |
| // - size is strictly positive |
| ASSERT(size > 0); |
| // - size is a multiple of double words |
| ASSERT(Utils::IsAligned(size, 2 * sizeof(uword))); |
| |
| uword* __restrict dst_cursor = reinterpret_cast<uword*>(dst); |
| const uword* __restrict src_cursor = reinterpret_cast<const uword*>(src); |
| do { |
| uword a = *src_cursor++; |
| uword b = *src_cursor++; |
| *dst_cursor++ = a; |
| *dst_cursor++ = b; |
| size -= (2 * sizeof(uword)); |
| } while (size > 0); |
| } |
| |
| DART_FORCE_INLINE |
| static uword ReadHeaderRelaxed(ObjectPtr obj) { |
| return reinterpret_cast<std::atomic<uword>*>(UntaggedObject::ToAddr(obj)) |
| ->load(std::memory_order_relaxed); |
| } |
| |
| DART_FORCE_INLINE |
| static void WriteHeaderRelaxed(ObjectPtr obj, uword header) { |
| reinterpret_cast<std::atomic<uword>*>(UntaggedObject::ToAddr(obj)) |
| ->store(header, std::memory_order_relaxed); |
| } |
| |
| template <bool parallel> |
| class ScavengerVisitorBase : public ObjectPointerVisitor, |
| public PredicateObjectPointerVisitor { |
| public: |
| explicit ScavengerVisitorBase(IsolateGroup* isolate_group, |
| Scavenger* scavenger, |
| SemiSpace* from, |
| FreeList* freelist, |
| PromotionStack* promotion_stack) |
| : ObjectPointerVisitor(isolate_group), |
| thread_(nullptr), |
| scavenger_(scavenger), |
| from_(from), |
| page_space_(scavenger->heap_->old_space()), |
| freelist_(freelist), |
| bytes_promoted_(0), |
| visiting_old_object_(nullptr), |
| promoted_list_(promotion_stack) {} |
| ~ScavengerVisitorBase() {} |
| |
| #ifdef DEBUG |
| constexpr static const char* const kName = "Scavenger"; |
| #endif |
| |
| void VisitTypedDataViewPointers(TypedDataViewPtr view, |
| CompressedObjectPtr* first, |
| CompressedObjectPtr* last) override { |
| // TypedDataViews require extra processing to update their |
| // PointerBase::data_ pointer. If the underlying typed data is external, no |
| // update is needed. If the underlying typed data is internal, the pointer |
| // must be updated if the typed data was copied or promoted. We cannot |
| // safely dereference the underlying typed data to make this distinction. |
| // It may have been forwarded by a different scavenger worker, so the access |
| // could have a data race. Rather than checking the CID of the underlying |
| // typed data, which requires dereferencing the copied/promoted header, we |
| // compare the view's internal pointer to what it should be if the |
| // underlying typed data was internal, and assume that external typed data |
| // never points into the Dart heap. We must do this before VisitPointers |
| // because we want to compare the old pointer and old typed data. |
| const bool is_external = |
| view->untag()->data_ != view->untag()->DataFieldForInternalTypedData(); |
| |
| // Forward all fields of the typed data view. |
| VisitCompressedPointers(view->heap_base(), first, last); |
| |
| if (view->untag()->data_ == nullptr) { |
| ASSERT(RawSmiValue(view->untag()->offset_in_bytes()) == 0 && |
| RawSmiValue(view->untag()->length()) == 0); |
| ASSERT(is_external); |
| return; |
| } |
| |
| // Explicit ifdefs because the compiler does not eliminate the unused |
| // relaxed load. |
| #if defined(DEBUG) |
| // Validate 'this' is a typed data view. |
| const uword view_header = ReadHeaderRelaxed(view); |
| ASSERT(!IsForwarding(view_header) || view->IsOldObject()); |
| ASSERT(IsTypedDataViewClassId(view->GetClassIdMayBeSmi()) || |
| IsUnmodifiableTypedDataViewClassId(view->GetClassIdMayBeSmi())); |
| |
| // Validate that the backing store is not a forwarding word. There is a data |
| // race reader the backing store's header unless there is only one worker. |
| TypedDataBasePtr td = view->untag()->typed_data(); |
| ASSERT(td->IsHeapObject()); |
| if (!parallel) { |
| const uword td_header = ReadHeaderRelaxed(td); |
| ASSERT(!IsForwarding(td_header) || td->IsOldObject()); |
| if (td != Object::null()) { |
| // Fast object copy temporarily stores null in the typed_data field of |
| // views. This can cause the RecomputeDataFieldForInternalTypedData to |
| // run inappropriately, but when the object copy continues it will fix |
| // the data_ pointer. |
| ASSERT_EQUAL(IsExternalTypedDataClassId(td->GetClassId()), is_external); |
| } |
| } |
| #endif |
| |
| // If we have external typed data we can simply return since the backing |
| // store lives in C-heap and will not move. |
| if (is_external) { |
| return; |
| } |
| |
| // Now we update the inner pointer. |
| #if defined(DEBUG) |
| if (!parallel) { |
| ASSERT(IsTypedDataClassId(td->GetClassId())); |
| } |
| #endif |
| view->untag()->RecomputeDataFieldForInternalTypedData(); |
| } |
| |
| void VisitPointers(ObjectPtr* first, ObjectPtr* last) override { |
| ASSERT(Utils::IsAligned(first, sizeof(*first))); |
| ASSERT(Utils::IsAligned(last, sizeof(*last))); |
| for (ObjectPtr* current = first; current <= last; current++) { |
| ScavengePointer(current); |
| } |
| } |
| |
| bool PredicateVisitPointers(ObjectPtr* first, ObjectPtr* last) override { |
| bool has_new_target = false; |
| for (ObjectPtr* current = first; current <= last; current++) { |
| has_new_target |= PredicateScavengePointer(current); |
| } |
| return has_new_target; |
| } |
| |
| #if defined(DART_COMPRESSED_POINTERS) |
| bool PredicateVisitCompressedPointers(uword heap_base, |
| CompressedObjectPtr* first, |
| CompressedObjectPtr* last) override { |
| bool has_new_target = false; |
| for (CompressedObjectPtr* current = first; current <= last; current++) { |
| has_new_target |= PredicateScavengeCompressedPointer(heap_base, current); |
| } |
| return has_new_target; |
| } |
| |
| void VisitCompressedPointers(uword heap_base, |
| CompressedObjectPtr* first, |
| CompressedObjectPtr* last) override { |
| if (PredicateVisitCompressedPointers(heap_base, first, last)) { |
| // Update the store buffer as needed. |
| ObjectPtr visiting_object = visiting_old_object_; |
| if (visiting_object != nullptr && |
| visiting_object->untag()->TryAcquireRememberedBit()) { |
| thread_->StoreBufferAddObjectGC(visiting_object); |
| } |
| } |
| } |
| #endif |
| |
| void VisitingOldObject(ObjectPtr obj) { |
| ASSERT((obj == nullptr) || obj->IsOldObject()); |
| visiting_old_object_ = obj; |
| if (obj != nullptr) { |
| // Card update happens in Page::VisitRememberedCards. |
| ASSERT(!obj->untag()->IsCardRemembered()); |
| } |
| } |
| DART_FORCE_INLINE intptr_t ProcessObject(ObjectPtr obj); |
| |
| intptr_t bytes_promoted() const { return bytes_promoted_; } |
| |
| void ProcessRoots() { |
| thread_ = Thread::Current(); |
| page_space_->AcquireLock(freelist_); |
| |
| LongJumpScope jump(thread_); |
| if (setjmp(*jump.Set()) == 0) { |
| scavenger_->IterateRoots(this); |
| } else { |
| ASSERT(scavenger_->abort_); |
| } |
| } |
| |
| void ProcessSurvivors() { |
| LongJumpScope jump(thread_); |
| if (setjmp(*jump.Set()) == 0) { |
| // Iterate until all work has been drained. |
| do { |
| ProcessToSpace(); |
| ProcessPromotedList(); |
| } while (HasWork()); |
| } else { |
| ASSERT(scavenger_->abort_); |
| } |
| } |
| |
| void ProcessAll() { |
| TIMELINE_FUNCTION_GC_DURATION(thread_, "ProcessToSpace"); |
| LongJumpScope jump(thread_); |
| if (setjmp(*jump.Set()) == 0) { |
| do { |
| do { |
| ProcessToSpace(); |
| ProcessPromotedList(); |
| } while (HasWork()); |
| ProcessWeakPropertiesScoped(); |
| } while (HasWork()); |
| } else { |
| ASSERT(scavenger_->abort_); |
| } |
| } |
| |
| void ProcessWeakProperties() { |
| LongJumpScope jump(thread_); |
| if (setjmp(*jump.Set()) == 0) { |
| ProcessWeakPropertiesScoped(); |
| } else { |
| ASSERT(scavenger_->abort_); |
| } |
| } |
| |
| bool HasWork() { |
| if (scavenger_->abort_) return false; |
| return (scan_ != tail_) || (scan_ != nullptr && !scan_->IsResolved()) || |
| !promoted_list_.IsEmpty(); |
| } |
| |
| bool WaitForWork(RelaxedAtomic<uintptr_t>* num_busy) { |
| return promoted_list_.WaitForWork(num_busy, scavenger_->abort_); |
| } |
| |
| void ProcessWeak() { |
| if (!scavenger_->abort_) { |
| ASSERT(!HasWork()); |
| |
| for (Page* page = head_; page != nullptr; page = page->next()) { |
| ASSERT(page->IsResolved()); |
| page->RecordSurvivors(); |
| } |
| |
| MournWeakProperties(); |
| MournWeakReferences(); |
| MournWeakArrays(); |
| MournFinalizerEntries(); |
| scavenger_->IterateWeak(); |
| } |
| page_space_->ReleaseLock(freelist_); |
| thread_ = nullptr; |
| } |
| |
| void Finalize() { |
| if (!scavenger_->abort_) { |
| promoted_list_.Finalize(); |
| weak_array_list_.Finalize(); |
| weak_property_list_.Finalize(); |
| weak_reference_list_.Finalize(); |
| finalizer_entry_list_.Finalize(); |
| } else { |
| promoted_list_.AbandonWork(); |
| weak_array_list_.AbandonWork(); |
| weak_property_list_.AbandonWork(); |
| weak_reference_list_.AbandonWork(); |
| finalizer_entry_list_.AbandonWork(); |
| } |
| } |
| |
| Page* head() const { return head_; } |
| Page* tail() const { return tail_; } |
| |
| static bool ForwardOrSetNullIfCollected(ObjectPtr parent, |
| CompressedObjectPtr* ptr_address); |
| |
| private: |
| DART_FORCE_INLINE |
| bool PredicateScavengePointer(ObjectPtr* p) { |
| // ScavengePointer cannot be called recursively. |
| ObjectPtr obj = *p; |
| |
| if (obj->IsImmediateOrOldObject()) { |
| return false; |
| } |
| |
| ObjectPtr new_obj = ScavengeObject(obj); |
| |
| // Update the reference. |
| *p = new_obj; |
| return new_obj->IsNewObject(); |
| } |
| |
| DART_FORCE_INLINE |
| void ScavengePointer(ObjectPtr* p) { |
| if (PredicateScavengePointer(p)) { |
| // Update the store buffer as needed. |
| ObjectPtr visiting_object = visiting_old_object_; |
| if (visiting_object != nullptr && |
| visiting_object->untag()->TryAcquireRememberedBit()) { |
| thread_->StoreBufferAddObjectGC(visiting_object); |
| } |
| } |
| } |
| |
| DART_FORCE_INLINE |
| bool PredicateScavengeCompressedPointer(uword heap_base, |
| CompressedObjectPtr* p) { |
| // ScavengePointer cannot be called recursively. |
| ObjectPtr obj = p->Decompress(heap_base); |
| |
| // Could be tested without decompression. |
| if (obj->IsImmediateOrOldObject()) { |
| return false; |
| } |
| |
| ObjectPtr new_obj = ScavengeObject(obj); |
| |
| // Update the reference. |
| *p = new_obj; |
| return new_obj->IsNewObject(); |
| } |
| |
| DART_FORCE_INLINE |
| void ScavengeCompressedPointer(uword heap_base, CompressedObjectPtr* p) { |
| if (PredicateScavengeCompressedPointer(heap_base, p)) { |
| // Update the store buffer as needed. |
| ObjectPtr visiting_object = visiting_old_object_; |
| if (visiting_object != nullptr && |
| visiting_object->untag()->TryAcquireRememberedBit()) { |
| thread_->StoreBufferAddObjectGC(visiting_object); |
| } |
| } |
| } |
| |
| DART_FORCE_INLINE |
| ObjectPtr ScavengeObject(ObjectPtr obj) { |
| // Fragmentation might cause the scavenge to fail. Ensure we always have |
| // somewhere to bail out to. |
| ASSERT(thread_->long_jump_base() != nullptr); |
| |
| uword raw_addr = UntaggedObject::ToAddr(obj); |
| // The scavenger is only expects objects located in the from space. |
| ASSERT(from_->Contains(raw_addr)); |
| // Read the header word of the object and determine if the object has |
| // already been copied. |
| uword header = ReadHeaderRelaxed(obj); |
| ObjectPtr new_obj; |
| if (IsForwarding(header)) { |
| // Get the new location of the object. |
| new_obj = ForwardedObj(header); |
| } else { |
| intptr_t size = obj->untag()->HeapSize(header); |
| ASSERT(IsAllocatableInNewSpace(size)); |
| uword new_addr = 0; |
| // Check whether object should be promoted. |
| if (!Page::Of(obj)->IsSurvivor(raw_addr)) { |
| // Not a survivor of a previous scavenge. Just copy the object into the |
| // to space. |
| new_addr = TryAllocateCopy(size); |
| } |
| if (new_addr == 0) { |
| // This object is a survivor of a previous scavenge. Attempt to promote |
| // the object. (Or, unlikely, to-space was exhausted by fragmentation.) |
| new_addr = page_space_->TryAllocatePromoLocked(freelist_, size); |
| if (UNLIKELY(new_addr == 0)) { |
| // Promotion did not succeed. Copy into the to space instead. |
| scavenger_->failed_to_promote_ = true; |
| new_addr = TryAllocateCopy(size); |
| // To-space was exhausted by fragmentation and old-space could not |
| // grow. |
| if (UNLIKELY(new_addr == 0)) { |
| AbortScavenge(); |
| } |
| } |
| } |
| ASSERT(new_addr != 0); |
| // Copy the object to the new location. |
| objcpy(reinterpret_cast<void*>(new_addr), |
| reinterpret_cast<void*>(raw_addr), size); |
| |
| new_obj = UntaggedObject::FromAddr(new_addr); |
| if (new_obj->IsOldObject()) { |
| // Promoted: update age/barrier tags. |
| uword tags = static_cast<uword>(header); |
| tags = UntaggedObject::OldAndNotRememberedBit::update(true, tags); |
| tags = UntaggedObject::NewBit::update(false, tags); |
| new_obj->untag()->tags_.store(tags, std::memory_order_relaxed); |
| } |
| |
| intptr_t cid = UntaggedObject::ClassIdTag::decode(header); |
| if (IsTypedDataClassId(cid)) { |
| static_cast<TypedDataPtr>(new_obj)->untag()->RecomputeDataField(); |
| } |
| |
| // Try to install forwarding address. |
| uword forwarding_header = ForwardingHeader(new_obj); |
| if (InstallForwardingPointer(raw_addr, &header, forwarding_header)) { |
| if (new_obj->IsOldObject()) { |
| // If promotion succeeded then we need to remember it so that it can |
| // be traversed later. |
| promoted_list_.Push(new_obj); |
| bytes_promoted_ += size; |
| } |
| } else { |
| ASSERT(IsForwarding(header)); |
| if (new_obj->IsOldObject()) { |
| // Abandon as a free list element. |
| FreeListElement::AsElement(new_addr, size); |
| bytes_promoted_ -= size; |
| } else { |
| // Undo to-space allocation. |
| tail_->Unallocate(new_addr, size); |
| } |
| // Use the winner's forwarding target. |
| new_obj = ForwardedObj(header); |
| } |
| } |
| |
| return new_obj; |
| } |
| |
| DART_FORCE_INLINE |
| bool InstallForwardingPointer(uword addr, |
| uword* old_header, |
| uword new_header) { |
| if (parallel) { |
| return reinterpret_cast<std::atomic<uword>*>(addr) |
| ->compare_exchange_strong(*old_header, new_header, |
| std::memory_order_relaxed); |
| } else { |
| *reinterpret_cast<uword*>(addr) = new_header; |
| return true; |
| } |
| } |
| |
| DART_FORCE_INLINE |
| uword TryAllocateCopy(intptr_t size) { |
| ASSERT(Utils::IsAligned(size, kObjectAlignment)); |
| // TODO(rmacnak): Allocate one to start? |
| if (tail_ != nullptr) { |
| uword result = tail_->top_; |
| ASSERT((result & kObjectAlignmentMask) == kNewObjectAlignmentOffset); |
| uword new_top = result + size; |
| if (LIKELY(new_top <= tail_->end_)) { |
| tail_->top_ = new_top; |
| return result; |
| } |
| } |
| return TryAllocateCopySlow(size); |
| } |
| |
| DART_NOINLINE uword TryAllocateCopySlow(intptr_t size); |
| |
| DART_NOINLINE DART_NORETURN void AbortScavenge() { |
| if (FLAG_verbose_gc) { |
| OS::PrintErr("Aborting scavenge\n"); |
| } |
| scavenger_->abort_ = true; |
| // N.B. We must not set the sticky error, which may be a data race if |
| // that root slot was processed by a different worker. |
| thread_->long_jump_base()->Jump(1); |
| } |
| |
| void ProcessToSpace(); |
| void ProcessPromotedList(); |
| void ProcessWeakPropertiesScoped(); |
| |
| void MournWeakProperties() { |
| weak_property_list_.Process([](WeakPropertyPtr weak_property) { |
| weak_property->untag()->key_ = Object::null(); |
| weak_property->untag()->value_ = Object::null(); |
| }); |
| } |
| |
| void MournWeakReferences() { |
| weak_reference_list_.Process([](WeakReferencePtr weak_reference) { |
| ForwardOrSetNullIfCollected(weak_reference, |
| &weak_reference->untag()->target_); |
| }); |
| } |
| |
| void MournWeakArrays() { |
| weak_array_list_.Process([](WeakArrayPtr weak_array) { |
| intptr_t length = Smi::Value(weak_array->untag()->length()); |
| for (intptr_t i = 0; i < length; i++) { |
| ForwardOrSetNullIfCollected(weak_array, |
| &(weak_array->untag()->data()[i])); |
| } |
| }); |
| } |
| |
| void MournFinalizerEntries() { |
| finalizer_entry_list_.Process([&](FinalizerEntryPtr finalizer_entry) { |
| MournFinalizerEntry(this, finalizer_entry); |
| }); |
| } |
| |
| Thread* thread_; |
| Scavenger* scavenger_; |
| SemiSpace* from_; |
| PageSpace* page_space_; |
| FreeList* freelist_; |
| intptr_t bytes_promoted_; |
| ObjectPtr visiting_old_object_; |
| PromotionWorkList promoted_list_; |
| LocalBlockWorkList<64, WeakArrayPtr> weak_array_list_; |
| LocalBlockWorkList<64, WeakPropertyPtr> weak_property_list_; |
| LocalBlockWorkList<64, WeakReferencePtr> weak_reference_list_; |
| LocalBlockWorkList<64, FinalizerEntryPtr> finalizer_entry_list_; |
| |
| Page* head_ = nullptr; |
| Page* tail_ = nullptr; // Allocating from here. |
| Page* scan_ = nullptr; // Resolving from here. |
| |
| DISALLOW_COPY_AND_ASSIGN(ScavengerVisitorBase); |
| }; |
| |
| typedef ScavengerVisitorBase<false> SerialScavengerVisitor; |
| typedef ScavengerVisitorBase<true> ParallelScavengerVisitor; |
| |
| static bool IsUnreachable(ObjectPtr* ptr) { |
| ObjectPtr obj = *ptr; |
| if (obj->IsImmediateOrOldObject()) { |
| return false; |
| } |
| uword raw_addr = UntaggedObject::ToAddr(obj); |
| uword header = *reinterpret_cast<uword*>(raw_addr); |
| if (IsForwarding(header)) { |
| *ptr = ForwardedObj(header); |
| return false; |
| } |
| return true; |
| } |
| |
| class ScavengerWeakVisitor : public HandleVisitor { |
| public: |
| explicit ScavengerWeakVisitor(Thread* thread) : HandleVisitor(thread) {} |
| |
| void VisitHandle(uword addr) override { |
| FinalizablePersistentHandle* handle = |
| reinterpret_cast<FinalizablePersistentHandle*>(addr); |
| ObjectPtr* p = handle->ptr_addr(); |
| if (IsUnreachable(p)) { |
| handle->UpdateUnreachable(thread()->isolate_group()); |
| } else { |
| handle->UpdateRelocated(thread()->isolate_group()); |
| } |
| } |
| |
| private: |
| DISALLOW_COPY_AND_ASSIGN(ScavengerWeakVisitor); |
| }; |
| |
| class ParallelScavengerTask : public ThreadPool::Task { |
| public: |
| ParallelScavengerTask(IsolateGroup* isolate_group, |
| ThreadBarrier* barrier, |
| ParallelScavengerVisitor* visitor, |
| RelaxedAtomic<uintptr_t>* num_busy) |
| : isolate_group_(isolate_group), |
| barrier_(barrier), |
| visitor_(visitor), |
| num_busy_(num_busy) {} |
| |
| virtual void Run() { |
| if (!barrier_->TryEnter()) { |
| barrier_->Release(); |
| return; |
| } |
| |
| bool result = Thread::EnterIsolateGroupAsHelper( |
| isolate_group_, Thread::kScavengerTask, /*bypass_safepoint=*/true); |
| ASSERT(result); |
| |
| RunEnteredIsolateGroup(); |
| |
| Thread::ExitIsolateGroupAsHelper(/*bypass_safepoint=*/true); |
| |
| barrier_->Sync(); |
| barrier_->Release(); |
| } |
| |
| void RunEnteredIsolateGroup() { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "ParallelScavenge"); |
| |
| num_busy_->fetch_add(1u); |
| visitor_->ProcessRoots(); |
| |
| // Phase 1: Copying. |
| bool more_to_scavenge = false; |
| do { |
| do { |
| visitor_->ProcessSurvivors(); |
| } while (visitor_->WaitForWork(num_busy_)); |
| // Wait for all scavengers to stop. |
| barrier_->Sync(); |
| #if defined(DEBUG) |
| ASSERT(num_busy_->load() == 0); |
| // Caveat: must not allow any marker to continue past the barrier |
| // before we checked num_busy, otherwise one of them might rush |
| // ahead and increment it. |
| barrier_->Sync(); |
| #endif |
| // Check if we have any pending properties with marked keys. |
| // Those might have been marked by another marker. |
| visitor_->ProcessWeakProperties(); |
| more_to_scavenge = visitor_->HasWork(); |
| if (more_to_scavenge) { |
| // We have more work to do. Notify others. |
| num_busy_->fetch_add(1u); |
| } |
| |
| // Wait for all other scavengers to finish processing their pending |
| // weak properties and decide if they need to continue marking. |
| // Caveat: we need two barriers here to make this decision in lock step |
| // between all scavengers and the main thread. |
| barrier_->Sync(); |
| if (!more_to_scavenge && (num_busy_->load() > 0)) { |
| // All scavengers continue to mark as long as any single marker has |
| // some work to do. |
| num_busy_->fetch_add(1u); |
| more_to_scavenge = true; |
| } |
| barrier_->Sync(); |
| } while (more_to_scavenge); |
| |
| ASSERT(!visitor_->HasWork()); |
| |
| // Phase 2: Weak processing, statistics. |
| visitor_->ProcessWeak(); |
| } |
| |
| private: |
| IsolateGroup* isolate_group_; |
| ThreadBarrier* barrier_; |
| ParallelScavengerVisitor* visitor_; |
| RelaxedAtomic<uintptr_t>* num_busy_; |
| |
| DISALLOW_COPY_AND_ASSIGN(ParallelScavengerTask); |
| }; |
| |
| SemiSpace::SemiSpace(intptr_t gc_threshold_in_words) |
| : gc_threshold_in_words_(gc_threshold_in_words) {} |
| |
| SemiSpace::~SemiSpace() { |
| Page* page = head_; |
| while (page != nullptr) { |
| Page* next = page->next(); |
| page->Deallocate(); |
| page = next; |
| } |
| } |
| |
| Page* SemiSpace::TryAllocatePageLocked(bool link) { |
| if (capacity_in_words_ >= gc_threshold_in_words_) { |
| return nullptr; // Full. |
| } |
| Page* page = Page::Allocate(kPageSize, Page::kNew); |
| if (page == nullptr) { |
| return nullptr; // Out of memory; |
| } |
| capacity_in_words_ += kPageSizeInWords; |
| if (link) { |
| if (head_ == nullptr) { |
| head_ = tail_ = page; |
| } else { |
| tail_->set_next(page); |
| tail_ = page; |
| } |
| } |
| return page; |
| } |
| |
| bool SemiSpace::Contains(uword addr) const { |
| for (Page* page = head_; page != nullptr; page = page->next()) { |
| if (page->Contains(addr)) return true; |
| } |
| return false; |
| } |
| |
| void SemiSpace::WriteProtect(bool read_only) { |
| for (Page* page = head_; page != nullptr; page = page->next()) { |
| page->WriteProtect(read_only); |
| } |
| } |
| |
| void SemiSpace::AddList(Page* head, Page* tail) { |
| if (head == nullptr) { |
| return; |
| } |
| if (head_ == nullptr) { |
| head_ = head; |
| tail_ = tail; |
| return; |
| } |
| tail_->set_next(head); |
| tail_ = tail; |
| } |
| |
| // The initial estimate of how many words we can scavenge per microsecond (usage |
| // before / scavenge time). This is a conservative value observed running |
| // Flutter on a Nexus 4. After the first scavenge, we instead use a value based |
| // on the device's actual speed. |
| static constexpr intptr_t kConservativeInitialScavengeSpeed = 40; |
| |
| Scavenger::Scavenger(Heap* heap, intptr_t max_semi_capacity_in_words) |
| : heap_(heap), |
| max_semi_capacity_in_words_(max_semi_capacity_in_words), |
| scavenge_words_per_micro_(kConservativeInitialScavengeSpeed) { |
| ASSERT(heap != nullptr); |
| |
| // Verify assumptions about the first word in objects which the scavenger is |
| // going to use for forwarding pointers. |
| ASSERT(Object::tags_offset() == 0); |
| |
| // Set initial semi space size in words. |
| const intptr_t initial_semi_capacity_in_words = Utils::Minimum( |
| max_semi_capacity_in_words, FLAG_new_gen_semi_initial_size * MBInWords); |
| |
| to_ = new SemiSpace(initial_semi_capacity_in_words); |
| idle_scavenge_threshold_in_words_ = initial_semi_capacity_in_words; |
| |
| UpdateMaxHeapCapacity(); |
| UpdateMaxHeapUsage(); |
| } |
| |
| Scavenger::~Scavenger() { |
| ASSERT(!scavenging_); |
| delete to_; |
| ASSERT(blocks_ == nullptr); |
| } |
| |
| intptr_t Scavenger::NewSizeInWords(intptr_t old_size_in_words, |
| GCReason reason) const { |
| bool grow = false; |
| if (2 * heap_->isolate_group()->MutatorCount() > |
| (old_size_in_words / kPageSizeInWords)) { |
| // Not enough TLABs to give two to each mutator. |
| grow = true; |
| } |
| |
| if (reason == GCReason::kNewSpace) { |
| // If we GC for a reason other than new-space being full (i.e., full |
| // collection for old-space or store-buffer overflow), that's not an |
| // indication that new-space is too small. |
| if (stats_history_.Size() != 0) { |
| double garbage = |
| stats_history_.Get(0).ExpectedGarbageFraction(old_size_in_words); |
| if (garbage < (FLAG_new_gen_garbage_threshold / 100.0)) { |
| // Too much survived last time; grow new-space in the hope that a |
| // greater fraction of objects will become unreachable before new-space |
| // becomes full. |
| grow = true; |
| } |
| } |
| } |
| |
| if (grow) { |
| return Utils::Minimum(max_semi_capacity_in_words_, |
| old_size_in_words * FLAG_new_gen_growth_factor); |
| } |
| return old_size_in_words; |
| } |
| |
| class CollectStoreBufferVisitor : public ObjectPointerVisitor { |
| public: |
| CollectStoreBufferVisitor(ObjectSet* in_store_buffer, const char* msg) |
| : ObjectPointerVisitor(IsolateGroup::Current()), |
| in_store_buffer_(in_store_buffer), |
| msg_(msg) {} |
| |
| void VisitPointers(ObjectPtr* from, ObjectPtr* to) override { |
| for (ObjectPtr* ptr = from; ptr <= to; ptr++) { |
| ObjectPtr obj = *ptr; |
| RELEASE_ASSERT_WITH_MSG(obj->untag()->IsRemembered(), msg_); |
| RELEASE_ASSERT_WITH_MSG(obj->IsOldObject(), msg_); |
| |
| RELEASE_ASSERT_WITH_MSG(!obj->untag()->IsCardRemembered(), msg_); |
| if (obj.GetClassId() == kArrayCid) { |
| const uword length = |
| Smi::Value(static_cast<UntaggedArray*>(obj.untag())->length()); |
| RELEASE_ASSERT_WITH_MSG(!Array::UseCardMarkingForAllocation(length), |
| msg_); |
| } |
| in_store_buffer_->Add(obj); |
| } |
| } |
| |
| #if defined(DART_COMPRESSED_POINTERS) |
| void VisitCompressedPointers(uword heap_base, |
| CompressedObjectPtr* from, |
| CompressedObjectPtr* to) override { |
| UNREACHABLE(); // Store buffer blocks are not compressed. |
| } |
| #endif |
| |
| private: |
| ObjectSet* const in_store_buffer_; |
| const char* msg_; |
| }; |
| |
| class CheckStoreBufferVisitor : public ObjectVisitor, |
| public ObjectPointerVisitor { |
| public: |
| CheckStoreBufferVisitor(ObjectSet* in_store_buffer, |
| const SemiSpace* to, |
| const char* msg) |
| : ObjectVisitor(), |
| ObjectPointerVisitor(IsolateGroup::Current()), |
| in_store_buffer_(in_store_buffer), |
| to_(to), |
| msg_(msg) {} |
| |
| void VisitObject(ObjectPtr obj) override { |
| if (obj->IsPseudoObject()) return; |
| RELEASE_ASSERT_WITH_MSG(obj->IsOldObject(), msg_); |
| |
| RELEASE_ASSERT_WITH_MSG( |
| obj->untag()->IsRemembered() == in_store_buffer_->Contains(obj), msg_); |
| |
| visiting_ = obj; |
| is_remembered_ = obj->untag()->IsRemembered(); |
| is_card_remembered_ = obj->untag()->IsCardRemembered(); |
| if (is_card_remembered_) { |
| RELEASE_ASSERT_WITH_MSG(!is_remembered_, msg_); |
| RELEASE_ASSERT_WITH_MSG(Page::Of(obj)->progress_bar_ == 0, msg_); |
| } |
| obj->untag()->VisitPointers(this); |
| } |
| |
| void VisitPointers(ObjectPtr* from, ObjectPtr* to) override { |
| for (ObjectPtr* ptr = from; ptr <= to; ptr++) { |
| ObjectPtr obj = *ptr; |
| if (obj->IsHeapObject() && obj->IsNewObject()) { |
| if (is_card_remembered_) { |
| if (!Page::Of(visiting_)->IsCardRemembered(ptr)) { |
| FATAL( |
| "%s: Old object %#" Px " references new object %#" Px |
| ", but the " |
| "slot's card is not remembered. Consider using rr to watch the " |
| "slot %p and reverse-continue to find the store with a missing " |
| "barrier.\n", |
| msg_, static_cast<uword>(visiting_), static_cast<uword>(obj), |
| ptr); |
| } |
| } else if (!is_remembered_) { |
| FATAL("%s: Old object %#" Px " references new object %#" Px |
| ", but it is " |
| "not in any store buffer. Consider using rr to watch the " |
| "slot %p and reverse-continue to find the store with a missing " |
| "barrier.\n", |
| msg_, static_cast<uword>(visiting_), static_cast<uword>(obj), |
| ptr); |
| } |
| RELEASE_ASSERT_WITH_MSG(to_->Contains(UntaggedObject::ToAddr(obj)), |
| msg_); |
| } |
| } |
| } |
| |
| #if defined(DART_COMPRESSED_POINTERS) |
| void VisitCompressedPointers(uword heap_base, |
| CompressedObjectPtr* from, |
| CompressedObjectPtr* to) override { |
| for (CompressedObjectPtr* ptr = from; ptr <= to; ptr++) { |
| ObjectPtr obj = ptr->Decompress(heap_base); |
| if (obj->IsHeapObject() && obj->IsNewObject()) { |
| if (is_card_remembered_) { |
| if (!Page::Of(visiting_)->IsCardRemembered(ptr)) { |
| FATAL( |
| "%s: Old object %#" Px " references new object %#" Px |
| ", but the " |
| "slot's card is not remembered. Consider using rr to watch the " |
| "slot %p and reverse-continue to find the store with a missing " |
| "barrier.\n", |
| msg_, static_cast<uword>(visiting_), static_cast<uword>(obj), |
| ptr); |
| } |
| } else if (!is_remembered_) { |
| FATAL("%s: Old object %#" Px " references new object %#" Px |
| ", but it is " |
| "not in any store buffer. Consider using rr to watch the " |
| "slot %p and reverse-continue to find the store with a missing " |
| "barrier.\n", |
| msg_, static_cast<uword>(visiting_), static_cast<uword>(obj), |
| ptr); |
| } |
| RELEASE_ASSERT_WITH_MSG(to_->Contains(UntaggedObject::ToAddr(obj)), |
| msg_); |
| } |
| } |
| } |
| #endif |
| |
| private: |
| const ObjectSet* const in_store_buffer_; |
| const SemiSpace* const to_; |
| ObjectPtr visiting_; |
| bool is_remembered_; |
| bool is_card_remembered_; |
| const char* msg_; |
| }; |
| |
| void Scavenger::VerifyStoreBuffers(const char* msg) { |
| ASSERT(msg != nullptr); |
| Thread* thread = Thread::Current(); |
| StackZone stack_zone(thread); |
| Zone* zone = stack_zone.GetZone(); |
| |
| ObjectSet* in_store_buffer = new (zone) ObjectSet(zone); |
| heap_->AddRegionsToObjectSet(in_store_buffer); |
| |
| { |
| CollectStoreBufferVisitor visitor(in_store_buffer, msg); |
| heap_->isolate_group()->store_buffer()->VisitObjectPointers(&visitor); |
| } |
| |
| { |
| CheckStoreBufferVisitor visitor(in_store_buffer, to_, msg); |
| heap_->old_space()->VisitObjects(&visitor); |
| } |
| } |
| |
| SemiSpace* Scavenger::Prologue(GCReason reason) { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "Prologue"); |
| |
| heap_->isolate_group()->ReleaseStoreBuffers(); |
| heap_->isolate_group()->FlushMarkingStacks(); |
| |
| if (FLAG_verify_store_buffer) { |
| heap_->WaitForSweeperTasksAtSafepoint(Thread::Current()); |
| VerifyStoreBuffers("Verifying remembered set before Scavenge"); |
| } |
| |
| // Need to stash the old remembered set before any worker begins adding to the |
| // new remembered set. |
| blocks_ = heap_->isolate_group()->store_buffer()->PopAll(); |
| GCMarker* marker = heap_->old_space()->marker(); |
| if (marker != nullptr) { |
| mark_blocks_ = marker->marking_stack_.PopAll(); |
| new_blocks_ = marker->new_marking_stack_.PopAll(); |
| deferred_blocks_ = marker->deferred_marking_stack_.PopAll(); |
| } |
| |
| UpdateMaxHeapCapacity(); |
| |
| // Flip the two semi-spaces so that to_ is always the space for allocating |
| // objects. |
| SemiSpace* from; |
| { |
| MutexLocker ml(&space_lock_); |
| from = to_; |
| to_ = new SemiSpace(NewSizeInWords(from->gc_threshold_in_words(), reason)); |
| } |
| |
| return from; |
| } |
| |
| void Scavenger::Epilogue(SemiSpace* from) { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "Epilogue"); |
| |
| // All objects in the to space have been copied from the from space at this |
| // moment. |
| |
| // Ensure the mutator thread will fail the next allocation. This will force |
| // mutator to allocate a new TLAB |
| #if defined(DEBUG) |
| heap_->isolate_group()->ForEachIsolate( |
| [&](Isolate* isolate) { |
| Thread* mutator_thread = isolate->mutator_thread(); |
| ASSERT(mutator_thread == nullptr || mutator_thread->top() == 0); |
| }, |
| /*at_safepoint=*/true); |
| #endif // DEBUG |
| |
| double avg_frac = stats_history_.Get(0).PromoCandidatesSuccessFraction(); |
| if (stats_history_.Size() >= 2) { |
| // Previous scavenge is only given half as much weight. |
| avg_frac += 0.5 * stats_history_.Get(1).PromoCandidatesSuccessFraction(); |
| avg_frac /= 1.0 + 0.5; // Normalize. |
| } |
| |
| early_tenure_ = avg_frac >= (FLAG_early_tenuring_threshold / 100.0); |
| |
| // Update estimate of scavenger speed. This statistic assumes survivorship |
| // rates don't change much. |
| intptr_t history_used = 0; |
| intptr_t history_micros = 0; |
| ASSERT(stats_history_.Size() > 0); |
| for (intptr_t i = 0; i < stats_history_.Size(); i++) { |
| history_used += stats_history_.Get(i).UsedBeforeInWords(); |
| history_micros += stats_history_.Get(i).DurationMicros(); |
| } |
| if (history_micros == 0) { |
| history_micros = 1; |
| } |
| scavenge_words_per_micro_ = history_used / history_micros; |
| if (scavenge_words_per_micro_ == 0) { |
| scavenge_words_per_micro_ = 1; |
| } |
| |
| // Update amount of new-space we must allocate before performing an idle |
| // scavenge. This is based on the amount of work we expect to be able to |
| // complete in a typical idle period. |
| intptr_t average_idle_task_micros = 6000; |
| idle_scavenge_threshold_in_words_ = |
| scavenge_words_per_micro_ * average_idle_task_micros; |
| // Even if the scavenge speed is slow, make sure we don't scavenge too |
| // frequently, which just wastes power and falsely increases the promotion |
| // rate. |
| intptr_t lower_bound = 512 * KBInWords; |
| if (idle_scavenge_threshold_in_words_ < lower_bound) { |
| idle_scavenge_threshold_in_words_ = lower_bound; |
| } |
| // Even if the scavenge speed is very high, make sure we start considering |
| // idle scavenges before new space is full to avoid requiring a scavenge in |
| // the middle of a frame. |
| intptr_t upper_bound = 8 * ThresholdInWords() / 10; |
| if (idle_scavenge_threshold_in_words_ > upper_bound) { |
| idle_scavenge_threshold_in_words_ = upper_bound; |
| } |
| |
| if (FLAG_verify_store_buffer) { |
| // Scavenging will insert into the store buffer block on the current |
| // thread (later will parallel scavenge, the worker's threads). We need to |
| // flush this thread-local block to the isolate group or we will incorrectly |
| // report some objects as absent from the store buffer. This might cause |
| // a program to hit a store buffer overflow a bit sooner than it might |
| // otherwise, since overflow is measured in blocks. Store buffer overflows |
| // are very rare. |
| heap_->isolate_group()->ReleaseStoreBuffers(); |
| |
| heap_->WaitForSweeperTasksAtSafepoint(Thread::Current()); |
| VerifyStoreBuffers("Verifying remembered set after Scavenge"); |
| } |
| |
| delete from; |
| UpdateMaxHeapUsage(); |
| if (heap_ != nullptr) { |
| heap_->UpdateGlobalMaxUsed(); |
| } |
| } |
| |
| bool Scavenger::ShouldPerformIdleScavenge(int64_t deadline) { |
| // To make a consistent decision, we should not yield for a safepoint in the |
| // middle of deciding whether to perform an idle GC. |
| NoSafepointScope no_safepoint; |
| |
| // TODO(rmacnak): Investigate collecting a history of idle period durations. |
| intptr_t used_in_words = UsedInWords() + freed_in_words_; |
| intptr_t external_in_words = ExternalInWords(); |
| // Normal reason: new space is getting full. |
| bool for_new_space = (used_in_words >= idle_scavenge_threshold_in_words_) || |
| (external_in_words >= idle_scavenge_threshold_in_words_); |
| if (!for_new_space) { |
| return false; |
| } |
| |
| int64_t estimated_scavenge_completion = |
| OS::GetCurrentMonotonicMicros() + |
| used_in_words / scavenge_words_per_micro_; |
| return estimated_scavenge_completion <= deadline; |
| } |
| |
| void Scavenger::IterateIsolateRoots(ObjectPointerVisitor* visitor) { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "IterateIsolateRoots"); |
| heap_->isolate_group()->VisitObjectPointers( |
| visitor, ValidationPolicy::kDontValidateFrames); |
| } |
| |
| template <bool parallel> |
| void Scavenger::IterateStoreBuffers(ScavengerVisitorBase<parallel>* visitor) { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "IterateStoreBuffers"); |
| |
| // Iterating through the store buffers. |
| // Grab the deduplication sets out of the isolate's consolidated store buffer. |
| StoreBuffer* store_buffer = heap_->isolate_group()->store_buffer(); |
| StoreBufferBlock* pending = blocks_; |
| while (pending != nullptr) { |
| StoreBufferBlock* next = pending->next(); |
| // Generated code appends to store buffers; tell MemorySanitizer. |
| MSAN_UNPOISON(pending, sizeof(*pending)); |
| while (!pending->IsEmpty()) { |
| ObjectPtr obj = pending->Pop(); |
| ASSERT(!obj->IsForwardingCorpse()); |
| ASSERT(obj->untag()->IsRemembered()); |
| obj->untag()->ClearRememberedBit(); |
| visitor->VisitingOldObject(obj); |
| visitor->ProcessObject(obj); |
| } |
| pending->Reset(); |
| // Return the emptied block for recycling (no need to check threshold). |
| store_buffer->PushBlock(pending, StoreBuffer::kIgnoreThreshold); |
| blocks_ = pending = next; |
| } |
| // Done iterating through old objects remembered in the store buffers. |
| } |
| |
| template <bool parallel> |
| void Scavenger::IterateRememberedCards( |
| ScavengerVisitorBase<parallel>* visitor) { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "IterateRememberedCards"); |
| heap_->old_space()->VisitRememberedCards(visitor); |
| } |
| |
| void Scavenger::IterateObjectIdTable(ObjectPointerVisitor* visitor) { |
| #ifndef PRODUCT |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "IterateObjectIdTable"); |
| heap_->isolate_group()->VisitObjectIdRingPointers(visitor); |
| #endif // !PRODUCT |
| } |
| |
| enum RootSlices { |
| kIsolate = 0, |
| kObjectIdRing, |
| kStoreBuffer, |
| kNumRootSlices, |
| }; |
| |
| template <bool parallel> |
| void Scavenger::IterateRoots(ScavengerVisitorBase<parallel>* visitor) { |
| for (;;) { |
| intptr_t slice = root_slices_started_.fetch_add(1); |
| if (slice >= kNumRootSlices) { |
| break; // No more slices. |
| } |
| |
| switch (slice) { |
| case kIsolate: |
| IterateIsolateRoots(visitor); |
| break; |
| case kObjectIdRing: |
| IterateObjectIdTable(visitor); |
| break; |
| case kStoreBuffer: |
| IterateStoreBuffers(visitor); |
| break; |
| default: |
| UNREACHABLE(); |
| } |
| } |
| |
| IterateRememberedCards(visitor); |
| } |
| |
| enum WeakSlices { |
| kWeakHandles = 0, |
| kWeakTables, |
| kProgressBars, |
| kRememberLiveTemporaries, |
| kPruneWeak, |
| kNumWeakSlices, |
| }; |
| |
| void Scavenger::IterateWeak() { |
| for (;;) { |
| intptr_t slice = weak_slices_started_.fetch_add(1); |
| if (slice >= kNumWeakSlices) { |
| break; // No more slices. |
| } |
| |
| switch (slice) { |
| case kWeakHandles: |
| MournWeakHandles(); |
| break; |
| case kWeakTables: |
| MournWeakTables(); |
| break; |
| case kProgressBars: |
| heap_->old_space()->ResetProgressBars(); |
| break; |
| case kRememberLiveTemporaries: |
| // Restore write-barrier assumptions. |
| heap_->isolate_group()->RememberLiveTemporaries(); |
| break; |
| case kPruneWeak: { |
| GCMarker* marker = heap_->old_space()->marker(); |
| if (marker != nullptr) { |
| marker->PruneWeak(this); |
| } |
| } break; |
| default: |
| UNREACHABLE(); |
| } |
| } |
| |
| GCMarker* marker = heap_->old_space()->marker(); |
| if (marker != nullptr) { |
| Prune(&mark_blocks_, &marker->marking_stack_); |
| Prune(&new_blocks_, &marker->marking_stack_); |
| Prune(&deferred_blocks_, &marker->deferred_marking_stack_); |
| } |
| } |
| |
| void Scavenger::MournWeakHandles() { |
| Thread* thread = Thread::Current(); |
| TIMELINE_FUNCTION_GC_DURATION(thread, "MournWeakHandles"); |
| ScavengerWeakVisitor weak_visitor(thread); |
| heap_->isolate_group()->VisitWeakPersistentHandles(&weak_visitor); |
| } |
| |
| template <bool parallel> |
| void ScavengerVisitorBase<parallel>::ProcessToSpace() { |
| VisitingOldObject(nullptr); |
| while (scan_ != nullptr) { |
| uword resolved_top = scan_->resolved_top_; |
| while (resolved_top < scan_->top_) { |
| ObjectPtr obj = UntaggedObject::FromAddr(resolved_top); |
| resolved_top += ProcessObject(obj); |
| } |
| scan_->resolved_top_ = resolved_top; |
| |
| Page* next = scan_->next(); |
| if (next == nullptr) { |
| // Don't update scan_. More objects may yet be copied to this TLAB. |
| return; |
| } |
| scan_ = next; |
| } |
| } |
| |
| template <bool parallel> |
| void ScavengerVisitorBase<parallel>::ProcessPromotedList() { |
| ObjectPtr obj; |
| while (promoted_list_.Pop(&obj)) { |
| VisitingOldObject(obj); |
| ProcessObject(obj); |
| // Black allocation. |
| if (thread_->is_marking() && obj->untag()->TryAcquireMarkBit()) { |
| thread_->MarkingStackAddObject(obj); |
| } |
| } |
| } |
| |
| template <bool parallel> |
| void ScavengerVisitorBase<parallel>::ProcessWeakPropertiesScoped() { |
| if (scavenger_->abort_) return; |
| |
| // Finished this round of scavenging. Process the pending weak properties |
| // for which the keys have become reachable. Potentially this adds more |
| // objects to the to space. |
| weak_property_list_.Process([&](WeakPropertyPtr weak_property) { |
| ObjectPtr key = weak_property->untag()->key(); |
| ASSERT(key->IsHeapObject()); |
| ASSERT(key->IsNewObject()); |
| ASSERT(from_->Contains(UntaggedObject::ToAddr(key))); |
| |
| uword header = ReadHeaderRelaxed(key); |
| if (IsForwarding(header)) { |
| VisitingOldObject(weak_property->IsOldObject() ? weak_property : nullptr); |
| weak_property->untag()->VisitPointersNonvirtual(this); |
| } else { |
| weak_property_list_.Push(weak_property); |
| } |
| }); |
| } |
| |
| void Scavenger::UpdateMaxHeapCapacity() { |
| ASSERT(to_ != nullptr); |
| ASSERT(heap_ != nullptr); |
| auto isolate_group = heap_->isolate_group(); |
| ASSERT(isolate_group != nullptr); |
| isolate_group->GetHeapNewCapacityMaxMetric()->SetValue( |
| to_->capacity_in_words() * kWordSize); |
| } |
| |
| void Scavenger::UpdateMaxHeapUsage() { |
| ASSERT(to_ != nullptr); |
| ASSERT(heap_ != nullptr); |
| auto isolate_group = heap_->isolate_group(); |
| ASSERT(isolate_group != nullptr); |
| isolate_group->GetHeapNewUsedMaxMetric()->SetValue(UsedInWords() * kWordSize); |
| } |
| |
| static bool IsScavengeSurvivor(ObjectPtr obj) { |
| if (obj->IsImmediateOrOldObject()) return true; |
| return IsForwarding(ReadHeaderRelaxed(obj)); |
| } |
| |
| template <bool parallel> |
| intptr_t ScavengerVisitorBase<parallel>::ProcessObject(ObjectPtr obj) { |
| #if defined(DEBUG) |
| if (obj->IsNewObject()) { |
| ASSERT(visiting_old_object_ == nullptr); |
| } else { |
| ASSERT(visiting_old_object_ == obj); |
| ASSERT(!obj->untag()->IsRemembered()); |
| } |
| #endif |
| |
| intptr_t cid = obj->GetClassId(); |
| if (UNLIKELY(cid == kWeakPropertyCid)) { |
| WeakPropertyPtr weak_property = static_cast<WeakPropertyPtr>(obj); |
| if (!IsScavengeSurvivor(weak_property->untag()->key())) { |
| weak_property_list_.Push(weak_property); |
| return WeakProperty::InstanceSize(); |
| } |
| } else if (UNLIKELY(cid == kWeakReferenceCid)) { |
| WeakReferencePtr weak_reference = static_cast<WeakReferencePtr>(obj); |
| if (!IsScavengeSurvivor(weak_reference->untag()->target())) { |
| #if !defined(DART_COMPRESSED_POINTERS) |
| ScavengePointer(&weak_reference->untag()->type_arguments_); |
| #else |
| ScavengeCompressedPointer(weak_reference->heap_base(), |
| &weak_reference->untag()->type_arguments_); |
| #endif |
| weak_reference_list_.Push(weak_reference); |
| return WeakReference::InstanceSize(); |
| } |
| } else if (UNLIKELY(cid == kWeakArrayCid)) { |
| WeakArrayPtr weak_array = static_cast<WeakArrayPtr>(obj); |
| weak_array_list_.Push(weak_array); |
| return WeakArray::InstanceSize(Smi::Value(weak_array->untag()->length())); |
| } else if (UNLIKELY(cid == kFinalizerEntryCid)) { |
| FinalizerEntryPtr finalizer_entry = static_cast<FinalizerEntryPtr>(obj); |
| #if !defined(DART_COMPRESSED_POINTERS) |
| ScavengePointer(&finalizer_entry->untag()->token_); |
| ScavengePointer(&finalizer_entry->untag()->next_); |
| #else |
| ScavengeCompressedPointer(finalizer_entry->heap_base(), |
| &finalizer_entry->untag()->token_); |
| ScavengeCompressedPointer(finalizer_entry->heap_base(), |
| &finalizer_entry->untag()->next_); |
| #endif |
| finalizer_entry_list_.Push(finalizer_entry); |
| return FinalizerEntry::InstanceSize(); |
| } |
| return obj->untag()->VisitPointersNonvirtual(this); |
| } |
| |
| void Scavenger::MournWeakTables() { |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "MournWeakTables"); |
| |
| auto rehash_weak_table = [](WeakTable* table, WeakTable* replacement_new, |
| WeakTable* replacement_old, |
| Dart_HeapSamplingDeleteCallback cleanup) { |
| intptr_t size = table->size(); |
| for (intptr_t i = 0; i < size; i++) { |
| if (table->IsValidEntryAtExclusive(i)) { |
| ObjectPtr obj = table->ObjectAtExclusive(i); |
| ASSERT(obj->IsHeapObject()); |
| uword raw_addr = UntaggedObject::ToAddr(obj); |
| uword header = *reinterpret_cast<uword*>(raw_addr); |
| if (IsForwarding(header)) { |
| // The object has survived. Preserve its record. |
| obj = ForwardedObj(header); |
| auto replacement = |
| obj->IsNewObject() ? replacement_new : replacement_old; |
| replacement->SetValueExclusive(obj, table->ValueAtExclusive(i)); |
| } else { |
| // The object has been collected. |
| if (cleanup != nullptr) { |
| cleanup(reinterpret_cast<void*>(table->ValueAtExclusive(i))); |
| } |
| } |
| } |
| } |
| }; |
| |
| // Rehash the weak tables now that we know which objects survive this cycle. |
| for (int sel = 0; sel < Heap::kNumWeakSelectors; sel++) { |
| const auto selector = static_cast<Heap::WeakSelector>(sel); |
| auto table = heap_->GetWeakTable(Heap::kNew, selector); |
| auto table_old = heap_->GetWeakTable(Heap::kOld, selector); |
| |
| // Create a new weak table for the new-space. |
| auto table_new = WeakTable::NewFrom(table); |
| |
| Dart_HeapSamplingDeleteCallback cleanup = nullptr; |
| #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER) |
| if (sel == Heap::kHeapSamplingData) { |
| cleanup = HeapProfileSampler::delete_callback(); |
| } |
| #endif |
| rehash_weak_table(table, table_new, table_old, cleanup); |
| heap_->SetWeakTable(Heap::kNew, selector, table_new); |
| |
| // Remove the old table as it has been replaced with the newly allocated |
| // table above. |
| delete table; |
| } |
| |
| // Each isolate might have a weak table used for fast snapshot writing (i.e. |
| // isolate communication). Rehash those tables if need be. |
| heap_->isolate_group()->ForEachIsolate( |
| [&](Isolate* isolate) { |
| auto table = isolate->forward_table_new(); |
| if (table != nullptr) { |
| auto replacement = WeakTable::NewFrom(table); |
| rehash_weak_table(table, replacement, isolate->forward_table_old(), |
| nullptr); |
| isolate->set_forward_table_new(replacement); |
| } |
| }, |
| /*at_safepoint=*/true); |
| } |
| |
| void Scavenger::Forward(MarkingStack* marking_stack) { |
| ASSERT(abort_); |
| |
| class ReverseMarkStack : public ObjectPointerVisitor { |
| public: |
| explicit ReverseMarkStack(IsolateGroup* group) |
| : ObjectPointerVisitor(group) {} |
| |
| void VisitPointers(ObjectPtr* first, ObjectPtr* last) override { |
| for (ObjectPtr* p = first; p <= last; p++) { |
| ObjectPtr obj = *p; |
| #if defined(DEBUG) |
| if (obj->IsNewObject()) { |
| uword header = ReadHeaderRelaxed(obj); |
| ASSERT(!IsForwarding(header)); |
| } |
| #endif |
| if (obj->IsForwardingCorpse()) { |
| // Promoted object was pushed to mark list but reversed. |
| *p = reinterpret_cast<ForwardingCorpse*>(UntaggedObject::ToAddr(obj)) |
| ->target(); |
| } |
| } |
| } |
| #if defined(DART_COMPRESSED_POINTERS) |
| void VisitCompressedPointers(uword heap_base, |
| CompressedObjectPtr* first, |
| CompressedObjectPtr* last) override { |
| UNREACHABLE(); |
| } |
| #endif |
| }; |
| |
| ReverseMarkStack visitor(heap_->isolate_group()); |
| marking_stack->VisitObjectPointers(&visitor); |
| } |
| |
| void Scavenger::Prune(MarkingStackBlock** source, MarkingStack* marking_stack) { |
| ASSERT(!abort_); |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "PruneMarkingStack"); |
| MarkingStackBlock* reading; |
| MarkingStackBlock* writing = marking_stack->PopNonFullBlock(); |
| for (;;) { |
| { |
| MutexLocker ml(&space_lock_); |
| reading = *source; |
| if (reading == nullptr) break; |
| *source = reading->next(); |
| } |
| // Generated code appends to marking stacks; tell MemorySanitizer. |
| MSAN_UNPOISON(reading, sizeof(*reading)); |
| while (!reading->IsEmpty()) { |
| ObjectPtr obj = reading->Pop(); |
| ASSERT(obj->IsHeapObject()); |
| if (obj->IsNewObject()) { |
| uword header = ReadHeaderRelaxed(obj); |
| if (!IsForwarding(header)) continue; |
| obj = ForwardedObj(header); |
| } |
| ASSERT(!obj->IsForwardingCorpse()); |
| ASSERT(!obj->IsFreeListElement()); |
| writing->Push(obj); |
| if (writing->IsFull()) { |
| marking_stack->PushBlock(writing); |
| writing = marking_stack->PopNonFullBlock(); |
| } |
| } |
| reading->Reset(); |
| marking_stack->PushBlock(reading); |
| } |
| marking_stack->PushBlock(writing); |
| } |
| |
| void Scavenger::PruneWeak(GCLinkedLists* deferred) { |
| ASSERT(!abort_); |
| TIMELINE_FUNCTION_GC_DURATION(Thread::Current(), "PruneWeak"); |
| PruneWeak(&deferred->weak_properties); |
| PruneWeak(&deferred->weak_references); |
| PruneWeak(&deferred->weak_arrays); |
| PruneWeak(&deferred->finalizer_entries); |
| } |
| |
| template <typename Type, typename PtrType> |
| void Scavenger::PruneWeak(GCLinkedList<Type, PtrType>* list) { |
| PtrType weak = list->Release(); |
| while (weak != Object::null()) { |
| PtrType next; |
| if (weak->IsOldObject()) { |
| ASSERT(weak->GetClassId() == Type::kClassId); |
| next = weak->untag()->next_seen_by_gc_.Decompress(weak->heap_base()); |
| weak->untag()->next_seen_by_gc_ = Type::null(); |
| list->Enqueue(weak); |
| } else { |
| uword header = ReadHeaderRelaxed(weak); |
| if (IsForwarding(header)) { |
| weak = static_cast<PtrType>(ForwardedObj(header)); |
| ASSERT(weak->GetClassId() == Type::kClassId); |
| next = weak->untag()->next_seen_by_gc_.Decompress(weak->heap_base()); |
| weak->untag()->next_seen_by_gc_ = Type::null(); |
| list->Enqueue(weak); |
| } else { |
| // Collected in this scavenge. |
| ASSERT(weak->GetClassId() == Type::kClassId); |
| next = weak->untag()->next_seen_by_gc_.Decompress(weak->heap_base()); |
| } |
| } |
| |
| weak = next; |
| } |
| } |
| |
| // Returns whether the object referred to in `slot` was GCed this GC. |
| template <bool parallel> |
| bool ScavengerVisitorBase<parallel>::ForwardOrSetNullIfCollected( |
| ObjectPtr parent, |
| CompressedObjectPtr* slot) { |
| ObjectPtr target = slot->Decompress(parent->heap_base()); |
| if (target->IsImmediateOrOldObject()) { |
| // Object already null (which is old) or not touched during this GC. |
| return false; |
| } |
| uword header = ReadHeaderRelaxed(target); |
| if (IsForwarding(header)) { |
| // Get the new location of the object. |
| target = ForwardedObj(header); |
| *slot = target; |
| if (target->IsNewObject() && parent->IsOldObject() && |
| parent->untag()->TryAcquireRememberedBit()) { |
| Thread::Current()->StoreBufferAddObjectGC(parent); |
| } |
| return false; |
| } |
| ASSERT(target->IsHeapObject()); |
| ASSERT(target->IsNewObject()); |
| *slot = Object::null(); |
| return true; |
| } |
| |
| void Scavenger::VisitObjectPointers(ObjectPointerVisitor* visitor) const { |
| ASSERT(Thread::Current()->OwnsGCSafepoint() || |
| (Thread::Current()->task_kind() == Thread::kMarkerTask) || |
| (Thread::Current()->task_kind() == Thread::kCompactorTask)); |
| for (Page* page = to_->head(); page != nullptr; page = page->next()) { |
| page->VisitObjectPointers(visitor); |
| } |
| } |
| |
| void Scavenger::VisitObjects(ObjectVisitor* visitor) const { |
| ASSERT(Thread::Current()->OwnsGCSafepoint() || |
| (Thread::Current()->task_kind() == Thread::kMarkerTask)); |
| for (Page* page = to_->head(); page != nullptr; page = page->next()) { |
| page->VisitObjects(visitor); |
| } |
| } |
| |
| void Scavenger::AddRegionsToObjectSet(ObjectSet* set) const { |
| for (Page* page = to_->head(); page != nullptr; page = page->next()) { |
| set->AddRegion(page->start(), page->end()); |
| } |
| } |
| |
| void Scavenger::TryAllocateNewTLAB(Thread* thread, |
| intptr_t min_size, |
| bool can_safepoint) { |
| ASSERT(heap_ != Dart::vm_isolate_group()->heap()); |
| ASSERT(!scavenging_); |
| |
| #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER) |
| // Find the remaining space available in the TLAB before abandoning it so we |
| // can reset the heap sampling offset in the new TLAB. |
| intptr_t remaining = thread->true_end() - thread->top(); |
| const bool heap_sampling_enabled = thread->end() != thread->true_end(); |
| const bool is_first_tlab = thread->true_end() == 0; |
| if (heap_sampling_enabled && remaining > min_size) { |
| // This is a sampling point and the TLAB isn't actually full. |
| thread->heap_sampler().SampleNewSpaceAllocation(min_size); |
| return; |
| } |
| #endif |
| |
| intptr_t allocated = AbandonRemainingTLAB(thread); |
| if (can_safepoint && !thread->force_growth()) { |
| ASSERT(thread->no_safepoint_scope_depth() == 0); |
| heap_->CheckConcurrentMarking(thread, GCReason::kNewSpace, allocated); |
| } |
| |
| MutexLocker ml(&space_lock_); |
| for (Page* page = to_->head(); page != nullptr; page = page->next()) { |
| if (page->owner() != nullptr) continue; |
| intptr_t available = |
| (page->end() - kAllocationRedZoneSize) - page->object_end(); |
| if (available >= min_size) { |
| page->Acquire(thread); |
| #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER) |
| thread->heap_sampler().HandleNewTLAB(remaining, /*is_first_tlab=*/false); |
| #endif |
| return; |
| } |
| } |
| |
| Page* page = to_->TryAllocatePageLocked(true); |
| if (page == nullptr) { |
| return; |
| } |
| page->Acquire(thread); |
| #if !defined(PRODUCT) || defined(FORCE_INCLUDE_SAMPLING_HEAP_PROFILER) |
| thread->heap_sampler().HandleNewTLAB(remaining, is_first_tlab); |
| #endif |
| |
| heap_->old_space()->PushDependencyToConcurrentMarking(); |
| } |
| |
| void Scavenger::AbandonRemainingTLABForDebugging(Thread* thread) { |
| // Allocate any remaining space so the TLAB won't be reused. Write a filler |
| // object so it remains iterable. |
| uword top = thread->top(); |
| intptr_t size = thread->end() - thread->top(); |
| if (size > 0) { |
| thread->set_top(top + size); |
| ForwardingCorpse::AsForwarder(top, size); |
| } |
| |
| AbandonRemainingTLAB(thread); |
| } |
| |
| intptr_t Scavenger::AbandonRemainingTLAB(Thread* thread) { |
| if (thread->top() == 0) return 0; |
| |
| Page* page = Page::Of(thread->top() - 1); |
| intptr_t allocated; |
| { |
| if (thread->is_marking()) { |
| thread->DeferredMarkLiveTemporaries(); |
| } |
| MutexLocker ml(&space_lock_); |
| allocated = page->Release(thread); |
| } |
| ASSERT(thread->top() == 0); |
| return allocated; |
| } |
| |
| template <bool parallel> |
| uword ScavengerVisitorBase<parallel>::TryAllocateCopySlow(intptr_t size) { |
| Page* page; |
| { |
| MutexLocker ml(&scavenger_->space_lock_); |
| page = scavenger_->to_->TryAllocatePageLocked(false); |
| } |
| if (page == nullptr) { |
| return 0; |
| } |
| |
| if (head_ == nullptr) { |
| head_ = scan_ = page; |
| } else { |
| ASSERT(scan_ != nullptr); |
| tail_->set_next(page); |
| } |
| tail_ = page; |
| |
| return tail_->TryAllocateGC(size); |
| } |
| |
| void Scavenger::Scavenge(Thread* thread, GCType type, GCReason reason) { |
| int64_t start = OS::GetCurrentMonotonicMicros(); |
| |
| ASSERT(thread->OwnsGCSafepoint()); |
| |
| // Scavenging is not reentrant. Make sure that is the case. |
| ASSERT(!scavenging_); |
| scavenging_ = true; |
| |
| if (type == GCType::kEvacuate) { |
| // Forces the next scavenge to promote all the objects in the new space. |
| early_tenure_ = true; |
| } |
| |
| if (FLAG_verify_before_gc) { |
| heap_->WaitForSweeperTasksAtSafepoint(thread); |
| heap_->VerifyGC("Verifying before Scavenge", |
| thread->is_marking() ? kAllowMarked : kForbidMarked); |
| } |
| |
| // Prepare for a scavenge. |
| failed_to_promote_ = false; |
| abort_ = false; |
| root_slices_started_ = 0; |
| weak_slices_started_ = 0; |
| freed_in_words_ = 0; |
| intptr_t abandoned_bytes = 0; // TODO(rmacnak): Count fragmentation? |
| SpaceUsage usage_before = GetCurrentUsage(); |
| intptr_t promo_candidate_words = 0; |
| for (Page* page = to_->head(); page != nullptr; page = page->next()) { |
| page->Release(); |
| if (early_tenure_) { |
| page->EarlyTenure(); |
| } |
| promo_candidate_words += page->promo_candidate_words(); |
| } |
| heap_->old_space()->PauseConcurrentMarking(); |
| SemiSpace* from = Prologue(reason); |
| |
| intptr_t bytes_promoted; |
| if (FLAG_scavenger_tasks == 0) { |
| bytes_promoted = SerialScavenge(from); |
| } else { |
| bytes_promoted = ParallelScavenge(from); |
| } |
| if (abort_) { |
| ReverseScavenge(&from); |
| bytes_promoted = 0; |
| } else { |
| if ((ThresholdInWords() - UsedInWords()) < KBInWords) { |
| // Don't scavenge again until the next old-space GC has occurred. Prevents |
| // performing one scavenge per allocation as the heap limit is approached. |
| heap_->assume_scavenge_will_fail_ = true; |
| } |
| } |
| ASSERT(promotion_stack_.IsEmpty()); |
| heap_->old_space()->ResumeConcurrentMarking(); |
| |
| // Scavenge finished. Run accounting. |
| int64_t end = OS::GetCurrentMonotonicMicros(); |
| stats_history_.Add(ScavengeStats( |
| start, end, usage_before, GetCurrentUsage(), promo_candidate_words, |
| bytes_promoted >> kWordSizeLog2, abandoned_bytes >> kWordSizeLog2)); |
| Epilogue(from); |
| |
| if (FLAG_verify_after_gc) { |
| heap_->WaitForSweeperTasksAtSafepoint(thread); |
| heap_->VerifyGC("Verifying after Scavenge...", |
| thread->is_marking() ? kAllowMarked : kForbidMarked); |
| } |
| |
| // Done scavenging. Reset the marker. |
| ASSERT(scavenging_); |
| scavenging_ = false; |
| |
| // It is possible for objects to stay in the new space |
| // if the VM cannot create more pages for these objects. |
| ASSERT((type != GCType::kEvacuate) || (UsedInWords() == 0) || |
| failed_to_promote_); |
| } |
| |
| intptr_t Scavenger::SerialScavenge(SemiSpace* from) { |
| FreeList* freelist = heap_->old_space()->DataFreeList(0); |
| SerialScavengerVisitor visitor(heap_->isolate_group(), this, from, freelist, |
| &promotion_stack_); |
| visitor.ProcessRoots(); |
| visitor.ProcessAll(); |
| visitor.ProcessWeak(); |
| visitor.Finalize(); |
| to_->AddList(visitor.head(), visitor.tail()); |
| return visitor.bytes_promoted(); |
| } |
| |
| intptr_t Scavenger::ParallelScavenge(SemiSpace* from) { |
| intptr_t bytes_promoted = 0; |
| const intptr_t num_tasks = FLAG_scavenger_tasks; |
| ASSERT(num_tasks > 0); |
| |
| ThreadBarrier* barrier = new ThreadBarrier(num_tasks, 1); |
| RelaxedAtomic<uintptr_t> num_busy = 0; |
| |
| ParallelScavengerVisitor** visitors = |
| new ParallelScavengerVisitor*[num_tasks]; |
| for (intptr_t i = 0; i < num_tasks; i++) { |
| FreeList* freelist = heap_->old_space()->DataFreeList(i); |
| visitors[i] = new ParallelScavengerVisitor( |
| heap_->isolate_group(), this, from, freelist, &promotion_stack_); |
| if (i < (num_tasks - 1)) { |
| // Begin scavenging on a helper thread. |
| bool result = Dart::thread_pool()->Run<ParallelScavengerTask>( |
| heap_->isolate_group(), barrier, visitors[i], &num_busy); |
| ASSERT(result); |
| } else { |
| // Last worker is the main thread. |
| ParallelScavengerTask task(heap_->isolate_group(), barrier, visitors[i], |
| &num_busy); |
| task.RunEnteredIsolateGroup(); |
| barrier->Sync(); |
| barrier->Release(); |
| } |
| } |
| |
| for (intptr_t i = 0; i < num_tasks; i++) { |
| ParallelScavengerVisitor* visitor = visitors[i]; |
| visitor->Finalize(); |
| to_->AddList(visitor->head(), visitor->tail()); |
| bytes_promoted += visitor->bytes_promoted(); |
| delete visitor; |
| } |
| |
| delete[] visitors; |
| return bytes_promoted; |
| } |
| |
| void Scavenger::ReverseScavenge(SemiSpace** from) { |
| Thread* thread = Thread::Current(); |
| TIMELINE_FUNCTION_GC_DURATION(thread, "ReverseScavenge"); |
| |
| class ReverseFromForwardingVisitor : public ObjectVisitor { |
| void VisitObject(ObjectPtr from_obj) override { |
| uword from_header = ReadHeaderRelaxed(from_obj); |
| if (IsForwarding(from_header)) { |
| ObjectPtr to_obj = ForwardedObj(from_header); |
| uword to_header = ReadHeaderRelaxed(to_obj); |
| intptr_t size = to_obj->untag()->HeapSize(); |
| |
| // Reset the ages bits in case this was a promotion. |
| uword from_header = static_cast<uword>(to_header); |
| from_header = |
| UntaggedObject::OldAndNotRememberedBit::update(false, from_header); |
| from_header = UntaggedObject::NewBit::update(true, from_header); |
| |
| WriteHeaderRelaxed(from_obj, from_header); |
| |
| ForwardingCorpse::AsForwarder(UntaggedObject::ToAddr(to_obj), size) |
| ->set_target(from_obj); |
| } |
| } |
| }; |
| |
| ReverseFromForwardingVisitor visitor; |
| for (Page* page = (*from)->head(); page != nullptr; page = page->next()) { |
| page->VisitObjects(&visitor); |
| } |
| |
| // Swap from-space and to-space. The abandoned to-space will be deleted in |
| // the epilogue. |
| { |
| MutexLocker ml(&space_lock_); |
| SemiSpace* temp = to_; |
| to_ = *from; |
| *from = temp; |
| } |
| |
| // Release any remaining part of the promotion worklist that wasn't completed. |
| promotion_stack_.Reset(); |
| |
| // Release any remaining part of the remembered set that wasn't completed. |
| StoreBuffer* store_buffer = heap_->isolate_group()->store_buffer(); |
| StoreBufferBlock* pending = blocks_; |
| while (pending != nullptr) { |
| StoreBufferBlock* next = pending->next(); |
| pending->Reset(); |
| // Return the emptied block for recycling (no need to check threshold). |
| store_buffer->PushBlock(pending, StoreBuffer::kIgnoreThreshold); |
| pending = next; |
| } |
| blocks_ = nullptr; |
| |
| // Reverse the partial forwarding from the aborted scavenge. This also |
| // rebuilds the remembered set. |
| heap_->WaitForSweeperTasksAtSafepoint(thread); |
| Become::FollowForwardingPointers(thread); |
| |
| heap_->old_space()->ResetProgressBars(); |
| |
| GCMarker* marker = heap_->old_space()->marker(); |
| if (marker != nullptr) { |
| marker->marking_stack_.PushAll(mark_blocks_); |
| mark_blocks_ = nullptr; |
| marker->marking_stack_.PushAll(new_blocks_); |
| new_blocks_ = nullptr; |
| marker->deferred_marking_stack_.PushAll(deferred_blocks_); |
| deferred_blocks_ = nullptr; |
| // Not redundant with the flush at the beginning of the scavenge because |
| // the scavenge workers may add promoted objects to the mark stack. |
| heap_->isolate_group()->FlushMarkingStacks(); |
| |
| Forward(&marker->marking_stack_); |
| ASSERT(marker->new_marking_stack_.IsEmpty()); |
| Forward(&marker->deferred_marking_stack_); |
| } |
| |
| // Restore write-barrier assumptions. Must occur after mark list fixups. |
| heap_->isolate_group()->RememberLiveTemporaries(); |
| |
| // Don't scavenge again until the next old-space GC has occurred. Prevents |
| // performing one scavenge per allocation as the heap limit is approached. |
| heap_->assume_scavenge_will_fail_ = true; |
| } |
| |
| void Scavenger::WriteProtect(bool read_only) { |
| ASSERT(!scavenging_); |
| to_->WriteProtect(read_only); |
| } |
| |
| #ifndef PRODUCT |
| void Scavenger::PrintToJSONObject(JSONObject* object) const { |
| auto isolate_group = IsolateGroup::Current(); |
| ASSERT(isolate_group != nullptr); |
| JSONObject space(object, "new"); |
| space.AddProperty("type", "HeapSpace"); |
| space.AddProperty("name", "new"); |
| space.AddProperty("vmName", "Scavenger"); |
| space.AddProperty("collections", collections()); |
| if (collections() > 0) { |
| int64_t run_time = isolate_group->UptimeMicros(); |
| run_time = Utils::Maximum(run_time, static_cast<int64_t>(0)); |
| double run_time_millis = MicrosecondsToMilliseconds(run_time); |
| double avg_time_between_collections = |
| run_time_millis / static_cast<double>(collections()); |
| space.AddProperty("avgCollectionPeriodMillis", |
| avg_time_between_collections); |
| } else { |
| space.AddProperty("avgCollectionPeriodMillis", 0.0); |
| } |
| space.AddProperty64("used", UsedInWords() * kWordSize); |
| space.AddProperty64("capacity", CapacityInWords() * kWordSize); |
| space.AddProperty64("external", ExternalInWords() * kWordSize); |
| space.AddProperty("time", MicrosecondsToSeconds(gc_time_micros())); |
| } |
| #endif // !PRODUCT |
| |
| } // namespace dart |