| // Copyright 2012 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/heap/mark-compact.h" |
| |
| #include "src/base/atomicops.h" |
| #include "src/base/bits.h" |
| #include "src/base/sys-info.h" |
| #include "src/code-stubs.h" |
| #include "src/compilation-cache.h" |
| #include "src/deoptimizer.h" |
| #include "src/execution.h" |
| #include "src/frames-inl.h" |
| #include "src/gdb-jit.h" |
| #include "src/global-handles.h" |
| #include "src/heap/array-buffer-tracker.h" |
| #include "src/heap/gc-tracer.h" |
| #include "src/heap/incremental-marking.h" |
| #include "src/heap/mark-compact-inl.h" |
| #include "src/heap/object-stats.h" |
| #include "src/heap/objects-visiting-inl.h" |
| #include "src/heap/objects-visiting.h" |
| #include "src/heap/slots-buffer.h" |
| #include "src/heap/spaces-inl.h" |
| #include "src/ic/ic.h" |
| #include "src/ic/stub-cache.h" |
| #include "src/profiler/cpu-profiler.h" |
| #include "src/utils-inl.h" |
| #include "src/v8.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| |
| const char* Marking::kWhiteBitPattern = "00"; |
| const char* Marking::kBlackBitPattern = "11"; |
| const char* Marking::kGreyBitPattern = "10"; |
| const char* Marking::kImpossibleBitPattern = "01"; |
| |
| |
| // The following has to hold in order for {Marking::MarkBitFrom} to not produce |
| // invalid {kImpossibleBitPattern} in the marking bitmap by overlapping. |
| STATIC_ASSERT(Heap::kMinObjectSizeInWords >= 2); |
| |
| |
| // ------------------------------------------------------------------------- |
| // MarkCompactCollector |
| |
| MarkCompactCollector::MarkCompactCollector(Heap* heap) |
| : // NOLINT |
| #ifdef DEBUG |
| state_(IDLE), |
| #endif |
| marking_parity_(ODD_MARKING_PARITY), |
| was_marked_incrementally_(false), |
| evacuation_(false), |
| slots_buffer_allocator_(nullptr), |
| migration_slots_buffer_(nullptr), |
| heap_(heap), |
| marking_deque_memory_(NULL), |
| marking_deque_memory_committed_(0), |
| code_flusher_(nullptr), |
| have_code_to_deoptimize_(false), |
| compacting_(false), |
| sweeping_in_progress_(false), |
| compaction_in_progress_(false), |
| pending_sweeper_tasks_semaphore_(0), |
| pending_compaction_tasks_semaphore_(0) { |
| } |
| |
| #ifdef VERIFY_HEAP |
| class VerifyMarkingVisitor : public ObjectVisitor { |
| public: |
| explicit VerifyMarkingVisitor(Heap* heap) : heap_(heap) {} |
| |
| void VisitPointers(Object** start, Object** end) override { |
| for (Object** current = start; current < end; current++) { |
| if ((*current)->IsHeapObject()) { |
| HeapObject* object = HeapObject::cast(*current); |
| CHECK(heap_->mark_compact_collector()->IsMarked(object)); |
| } |
| } |
| } |
| |
| void VisitEmbeddedPointer(RelocInfo* rinfo) override { |
| DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT); |
| if (!rinfo->host()->IsWeakObject(rinfo->target_object())) { |
| Object* p = rinfo->target_object(); |
| VisitPointer(&p); |
| } |
| } |
| |
| void VisitCell(RelocInfo* rinfo) override { |
| Code* code = rinfo->host(); |
| DCHECK(rinfo->rmode() == RelocInfo::CELL); |
| if (!code->IsWeakObject(rinfo->target_cell())) { |
| ObjectVisitor::VisitCell(rinfo); |
| } |
| } |
| |
| private: |
| Heap* heap_; |
| }; |
| |
| |
| static void VerifyMarking(Heap* heap, Address bottom, Address top) { |
| VerifyMarkingVisitor visitor(heap); |
| HeapObject* object; |
| Address next_object_must_be_here_or_later = bottom; |
| |
| for (Address current = bottom; current < top; current += kPointerSize) { |
| object = HeapObject::FromAddress(current); |
| if (MarkCompactCollector::IsMarked(object)) { |
| CHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| CHECK(current >= next_object_must_be_here_or_later); |
| object->Iterate(&visitor); |
| next_object_must_be_here_or_later = current + object->Size(); |
| // The next word for sure belongs to the current object, jump over it. |
| current += kPointerSize; |
| } |
| } |
| } |
| |
| |
| static void VerifyMarking(NewSpace* space) { |
| Address end = space->top(); |
| NewSpacePageIterator it(space->bottom(), end); |
| // The bottom position is at the start of its page. Allows us to use |
| // page->area_start() as start of range on all pages. |
| CHECK_EQ(space->bottom(), |
| NewSpacePage::FromAddress(space->bottom())->area_start()); |
| while (it.has_next()) { |
| NewSpacePage* page = it.next(); |
| Address limit = it.has_next() ? page->area_end() : end; |
| CHECK(limit == end || !page->Contains(end)); |
| VerifyMarking(space->heap(), page->area_start(), limit); |
| } |
| } |
| |
| |
| static void VerifyMarking(PagedSpace* space) { |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| VerifyMarking(space->heap(), p->area_start(), p->area_end()); |
| } |
| } |
| |
| |
| static void VerifyMarking(Heap* heap) { |
| VerifyMarking(heap->old_space()); |
| VerifyMarking(heap->code_space()); |
| VerifyMarking(heap->map_space()); |
| VerifyMarking(heap->new_space()); |
| |
| VerifyMarkingVisitor visitor(heap); |
| |
| LargeObjectIterator it(heap->lo_space()); |
| for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) { |
| if (MarkCompactCollector::IsMarked(obj)) { |
| obj->Iterate(&visitor); |
| } |
| } |
| |
| heap->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG); |
| } |
| |
| |
| class VerifyEvacuationVisitor : public ObjectVisitor { |
| public: |
| void VisitPointers(Object** start, Object** end) override { |
| for (Object** current = start; current < end; current++) { |
| if ((*current)->IsHeapObject()) { |
| HeapObject* object = HeapObject::cast(*current); |
| CHECK(!MarkCompactCollector::IsOnEvacuationCandidate(object)); |
| } |
| } |
| } |
| }; |
| |
| |
| static void VerifyEvacuation(Page* page) { |
| VerifyEvacuationVisitor visitor; |
| HeapObjectIterator iterator(page); |
| for (HeapObject* heap_object = iterator.Next(); heap_object != NULL; |
| heap_object = iterator.Next()) { |
| // We skip free space objects. |
| if (!heap_object->IsFiller()) { |
| heap_object->Iterate(&visitor); |
| } |
| } |
| } |
| |
| |
| static void VerifyEvacuation(NewSpace* space) { |
| NewSpacePageIterator it(space->bottom(), space->top()); |
| VerifyEvacuationVisitor visitor; |
| |
| while (it.has_next()) { |
| NewSpacePage* page = it.next(); |
| Address current = page->area_start(); |
| Address limit = it.has_next() ? page->area_end() : space->top(); |
| CHECK(limit == space->top() || !page->Contains(space->top())); |
| while (current < limit) { |
| HeapObject* object = HeapObject::FromAddress(current); |
| object->Iterate(&visitor); |
| current += object->Size(); |
| } |
| } |
| } |
| |
| |
| static void VerifyEvacuation(Heap* heap, PagedSpace* space) { |
| if (FLAG_use_allocation_folding && (space == heap->old_space())) { |
| return; |
| } |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| if (p->IsEvacuationCandidate()) continue; |
| VerifyEvacuation(p); |
| } |
| } |
| |
| |
| static void VerifyEvacuation(Heap* heap) { |
| VerifyEvacuation(heap, heap->old_space()); |
| VerifyEvacuation(heap, heap->code_space()); |
| VerifyEvacuation(heap, heap->map_space()); |
| VerifyEvacuation(heap->new_space()); |
| |
| VerifyEvacuationVisitor visitor; |
| heap->IterateStrongRoots(&visitor, VISIT_ALL); |
| } |
| #endif // VERIFY_HEAP |
| |
| |
| void MarkCompactCollector::SetUp() { |
| DCHECK(strcmp(Marking::kWhiteBitPattern, "00") == 0); |
| DCHECK(strcmp(Marking::kBlackBitPattern, "11") == 0); |
| DCHECK(strcmp(Marking::kGreyBitPattern, "10") == 0); |
| DCHECK(strcmp(Marking::kImpossibleBitPattern, "01") == 0); |
| |
| free_list_old_space_.Reset(new FreeList(heap_->old_space())); |
| free_list_code_space_.Reset(new FreeList(heap_->code_space())); |
| free_list_map_space_.Reset(new FreeList(heap_->map_space())); |
| EnsureMarkingDequeIsReserved(); |
| EnsureMarkingDequeIsCommitted(kMinMarkingDequeSize); |
| slots_buffer_allocator_ = new SlotsBufferAllocator(); |
| |
| if (FLAG_flush_code) { |
| code_flusher_ = new CodeFlusher(isolate()); |
| if (FLAG_trace_code_flushing) { |
| PrintF("[code-flushing is now on]\n"); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::TearDown() { |
| AbortCompaction(); |
| delete marking_deque_memory_; |
| delete slots_buffer_allocator_; |
| delete code_flusher_; |
| } |
| |
| |
| void MarkCompactCollector::AddEvacuationCandidate(Page* p) { |
| DCHECK(!p->NeverEvacuate()); |
| p->MarkEvacuationCandidate(); |
| evacuation_candidates_.Add(p); |
| } |
| |
| |
| static void TraceFragmentation(PagedSpace* space) { |
| int number_of_pages = space->CountTotalPages(); |
| intptr_t reserved = (number_of_pages * space->AreaSize()); |
| intptr_t free = reserved - space->SizeOfObjects(); |
| PrintF("[%s]: %d pages, %d (%.1f%%) free\n", |
| AllocationSpaceName(space->identity()), number_of_pages, |
| static_cast<int>(free), static_cast<double>(free) * 100 / reserved); |
| } |
| |
| |
| bool MarkCompactCollector::StartCompaction(CompactionMode mode) { |
| if (!compacting_) { |
| DCHECK(evacuation_candidates_.length() == 0); |
| |
| CollectEvacuationCandidates(heap()->old_space()); |
| |
| if (FLAG_compact_code_space) { |
| CollectEvacuationCandidates(heap()->code_space()); |
| } else if (FLAG_trace_fragmentation) { |
| TraceFragmentation(heap()->code_space()); |
| } |
| |
| if (FLAG_trace_fragmentation) { |
| TraceFragmentation(heap()->map_space()); |
| } |
| |
| heap()->old_space()->EvictEvacuationCandidatesFromLinearAllocationArea(); |
| heap()->code_space()->EvictEvacuationCandidatesFromLinearAllocationArea(); |
| |
| compacting_ = evacuation_candidates_.length() > 0; |
| } |
| |
| return compacting_; |
| } |
| |
| |
| void MarkCompactCollector::ClearInvalidStoreAndSlotsBufferEntries() { |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_STORE_BUFFER); |
| RememberedSet<OLD_TO_NEW>::ClearInvalidSlots(heap()); |
| } |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_SLOTS_BUFFER); |
| for (Page* p : evacuation_candidates_) { |
| SlotsBuffer::RemoveInvalidSlots(heap_, p->slots_buffer()); |
| } |
| } |
| #ifdef VERIFY_HEAP |
| if (FLAG_verify_heap) { |
| VerifyValidStoreAndSlotsBufferEntries(); |
| } |
| #endif |
| } |
| |
| |
| #ifdef VERIFY_HEAP |
| static void VerifyValidSlotsBufferEntries(Heap* heap, PagedSpace* space) { |
| PageIterator it(space); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| SlotsBuffer::VerifySlots(heap, p->slots_buffer()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::VerifyValidStoreAndSlotsBufferEntries() { |
| RememberedSet<OLD_TO_NEW>::VerifyValidSlots(heap()); |
| |
| VerifyValidSlotsBufferEntries(heap(), heap()->old_space()); |
| VerifyValidSlotsBufferEntries(heap(), heap()->code_space()); |
| VerifyValidSlotsBufferEntries(heap(), heap()->map_space()); |
| |
| LargeObjectIterator it(heap()->lo_space()); |
| for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) { |
| MemoryChunk* chunk = MemoryChunk::FromAddress(object->address()); |
| SlotsBuffer::VerifySlots(heap(), chunk->slots_buffer()); |
| } |
| } |
| #endif |
| |
| |
| void MarkCompactCollector::CollectGarbage() { |
| // Make sure that Prepare() has been called. The individual steps below will |
| // update the state as they proceed. |
| DCHECK(state_ == PREPARE_GC); |
| |
| MarkLiveObjects(); |
| |
| DCHECK(heap_->incremental_marking()->IsStopped()); |
| |
| ClearNonLiveReferences(); |
| |
| #ifdef VERIFY_HEAP |
| if (FLAG_verify_heap) { |
| VerifyMarking(heap_); |
| } |
| #endif |
| |
| SweepSpaces(); |
| |
| EvacuateNewSpaceAndCandidates(); |
| |
| Finish(); |
| } |
| |
| |
| #ifdef VERIFY_HEAP |
| void MarkCompactCollector::VerifyMarkbitsAreClean(PagedSpace* space) { |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| CHECK(p->markbits()->IsClean()); |
| CHECK_EQ(0, p->LiveBytes()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::VerifyMarkbitsAreClean(NewSpace* space) { |
| NewSpacePageIterator it(space->bottom(), space->top()); |
| |
| while (it.has_next()) { |
| NewSpacePage* p = it.next(); |
| CHECK(p->markbits()->IsClean()); |
| CHECK_EQ(0, p->LiveBytes()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::VerifyMarkbitsAreClean() { |
| VerifyMarkbitsAreClean(heap_->old_space()); |
| VerifyMarkbitsAreClean(heap_->code_space()); |
| VerifyMarkbitsAreClean(heap_->map_space()); |
| VerifyMarkbitsAreClean(heap_->new_space()); |
| |
| LargeObjectIterator it(heap_->lo_space()); |
| for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) { |
| MarkBit mark_bit = Marking::MarkBitFrom(obj); |
| CHECK(Marking::IsWhite(mark_bit)); |
| CHECK_EQ(0, Page::FromAddress(obj->address())->LiveBytes()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::VerifyWeakEmbeddedObjectsInCode() { |
| HeapObjectIterator code_iterator(heap()->code_space()); |
| for (HeapObject* obj = code_iterator.Next(); obj != NULL; |
| obj = code_iterator.Next()) { |
| Code* code = Code::cast(obj); |
| if (!code->is_optimized_code()) continue; |
| if (WillBeDeoptimized(code)) continue; |
| code->VerifyEmbeddedObjectsDependency(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::VerifyOmittedMapChecks() { |
| HeapObjectIterator iterator(heap()->map_space()); |
| for (HeapObject* obj = iterator.Next(); obj != NULL; obj = iterator.Next()) { |
| Map* map = Map::cast(obj); |
| map->VerifyOmittedMapChecks(); |
| } |
| } |
| #endif // VERIFY_HEAP |
| |
| |
| static void ClearMarkbitsInPagedSpace(PagedSpace* space) { |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Bitmap::Clear(it.next()); |
| } |
| } |
| |
| |
| static void ClearMarkbitsInNewSpace(NewSpace* space) { |
| NewSpacePageIterator it(space->ToSpaceStart(), space->ToSpaceEnd()); |
| |
| while (it.has_next()) { |
| Bitmap::Clear(it.next()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearMarkbits() { |
| ClearMarkbitsInPagedSpace(heap_->code_space()); |
| ClearMarkbitsInPagedSpace(heap_->map_space()); |
| ClearMarkbitsInPagedSpace(heap_->old_space()); |
| ClearMarkbitsInNewSpace(heap_->new_space()); |
| |
| LargeObjectIterator it(heap_->lo_space()); |
| for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) { |
| Marking::MarkWhite(Marking::MarkBitFrom(obj)); |
| Page::FromAddress(obj->address())->ResetProgressBar(); |
| Page::FromAddress(obj->address())->ResetLiveBytes(); |
| } |
| } |
| |
| |
| class MarkCompactCollector::SweeperTask : public v8::Task { |
| public: |
| SweeperTask(Heap* heap, AllocationSpace space_to_start) |
| : heap_(heap), space_to_start_(space_to_start) {} |
| |
| virtual ~SweeperTask() {} |
| |
| private: |
| // v8::Task overrides. |
| void Run() override { |
| DCHECK_GE(space_to_start_, FIRST_PAGED_SPACE); |
| DCHECK_LE(space_to_start_, LAST_PAGED_SPACE); |
| const int offset = space_to_start_ - FIRST_PAGED_SPACE; |
| const int num_spaces = LAST_PAGED_SPACE - FIRST_PAGED_SPACE + 1; |
| for (int i = 0; i < num_spaces; i++) { |
| const int space_id = FIRST_PAGED_SPACE + ((i + offset) % num_spaces); |
| DCHECK_GE(space_id, FIRST_PAGED_SPACE); |
| DCHECK_LE(space_id, LAST_PAGED_SPACE); |
| heap_->mark_compact_collector()->SweepInParallel( |
| heap_->paged_space(space_id), 0); |
| } |
| heap_->mark_compact_collector()->pending_sweeper_tasks_semaphore_.Signal(); |
| } |
| |
| Heap* heap_; |
| AllocationSpace space_to_start_; |
| |
| DISALLOW_COPY_AND_ASSIGN(SweeperTask); |
| }; |
| |
| |
| void MarkCompactCollector::StartSweeperThreads() { |
| DCHECK(free_list_old_space_.get()->IsEmpty()); |
| DCHECK(free_list_code_space_.get()->IsEmpty()); |
| DCHECK(free_list_map_space_.get()->IsEmpty()); |
| V8::GetCurrentPlatform()->CallOnBackgroundThread( |
| new SweeperTask(heap(), OLD_SPACE), v8::Platform::kShortRunningTask); |
| V8::GetCurrentPlatform()->CallOnBackgroundThread( |
| new SweeperTask(heap(), CODE_SPACE), v8::Platform::kShortRunningTask); |
| V8::GetCurrentPlatform()->CallOnBackgroundThread( |
| new SweeperTask(heap(), MAP_SPACE), v8::Platform::kShortRunningTask); |
| } |
| |
| |
| void MarkCompactCollector::SweepOrWaitUntilSweepingCompleted(Page* page) { |
| PagedSpace* owner = reinterpret_cast<PagedSpace*>(page->owner()); |
| if (!page->SweepingDone()) { |
| SweepInParallel(page, owner); |
| if (!page->SweepingDone()) { |
| // We were not able to sweep that page, i.e., a concurrent |
| // sweeper thread currently owns this page. Wait for the sweeper |
| // thread to be done with this page. |
| page->WaitUntilSweepingCompleted(); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::SweepAndRefill(CompactionSpace* space) { |
| if (FLAG_concurrent_sweeping && !IsSweepingCompleted()) { |
| SweepInParallel(heap()->paged_space(space->identity()), 0); |
| space->RefillFreeList(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::EnsureSweepingCompleted() { |
| DCHECK(sweeping_in_progress_ == true); |
| |
| // If sweeping is not completed or not running at all, we try to complete it |
| // here. |
| if (!FLAG_concurrent_sweeping || !IsSweepingCompleted()) { |
| SweepInParallel(heap()->paged_space(OLD_SPACE), 0); |
| SweepInParallel(heap()->paged_space(CODE_SPACE), 0); |
| SweepInParallel(heap()->paged_space(MAP_SPACE), 0); |
| } |
| |
| if (FLAG_concurrent_sweeping) { |
| pending_sweeper_tasks_semaphore_.Wait(); |
| pending_sweeper_tasks_semaphore_.Wait(); |
| pending_sweeper_tasks_semaphore_.Wait(); |
| } |
| |
| ParallelSweepSpacesComplete(); |
| sweeping_in_progress_ = false; |
| heap()->old_space()->RefillFreeList(); |
| heap()->code_space()->RefillFreeList(); |
| heap()->map_space()->RefillFreeList(); |
| |
| #ifdef VERIFY_HEAP |
| if (FLAG_verify_heap && !evacuation()) { |
| VerifyEvacuation(heap_); |
| } |
| #endif |
| } |
| |
| |
| bool MarkCompactCollector::IsSweepingCompleted() { |
| if (!pending_sweeper_tasks_semaphore_.WaitFor( |
| base::TimeDelta::FromSeconds(0))) { |
| return false; |
| } |
| pending_sweeper_tasks_semaphore_.Signal(); |
| return true; |
| } |
| |
| |
| void Marking::TransferMark(Heap* heap, Address old_start, Address new_start) { |
| // This is only used when resizing an object. |
| DCHECK(MemoryChunk::FromAddress(old_start) == |
| MemoryChunk::FromAddress(new_start)); |
| |
| if (!heap->incremental_marking()->IsMarking()) return; |
| |
| // If the mark doesn't move, we don't check the color of the object. |
| // It doesn't matter whether the object is black, since it hasn't changed |
| // size, so the adjustment to the live data count will be zero anyway. |
| if (old_start == new_start) return; |
| |
| MarkBit new_mark_bit = MarkBitFrom(new_start); |
| MarkBit old_mark_bit = MarkBitFrom(old_start); |
| |
| #ifdef DEBUG |
| ObjectColor old_color = Color(old_mark_bit); |
| #endif |
| |
| if (Marking::IsBlack(old_mark_bit)) { |
| Marking::BlackToWhite(old_mark_bit); |
| Marking::MarkBlack(new_mark_bit); |
| return; |
| } else if (Marking::IsGrey(old_mark_bit)) { |
| Marking::GreyToWhite(old_mark_bit); |
| heap->incremental_marking()->WhiteToGreyAndPush( |
| HeapObject::FromAddress(new_start), new_mark_bit); |
| heap->incremental_marking()->RestartIfNotMarking(); |
| } |
| |
| #ifdef DEBUG |
| ObjectColor new_color = Color(new_mark_bit); |
| DCHECK(new_color == old_color); |
| #endif |
| } |
| |
| |
| const char* AllocationSpaceName(AllocationSpace space) { |
| switch (space) { |
| case NEW_SPACE: |
| return "NEW_SPACE"; |
| case OLD_SPACE: |
| return "OLD_SPACE"; |
| case CODE_SPACE: |
| return "CODE_SPACE"; |
| case MAP_SPACE: |
| return "MAP_SPACE"; |
| case LO_SPACE: |
| return "LO_SPACE"; |
| default: |
| UNREACHABLE(); |
| } |
| |
| return NULL; |
| } |
| |
| |
| void MarkCompactCollector::ComputeEvacuationHeuristics( |
| int area_size, int* target_fragmentation_percent, |
| int* max_evacuated_bytes) { |
| // For memory reducing mode we directly define both constants. |
| const int kTargetFragmentationPercentForReduceMemory = 20; |
| const int kMaxEvacuatedBytesForReduceMemory = 12 * Page::kPageSize; |
| |
| // For regular mode (which is latency critical) we define less aggressive |
| // defaults to start and switch to a trace-based (using compaction speed) |
| // approach as soon as we have enough samples. |
| const int kTargetFragmentationPercent = 70; |
| const int kMaxEvacuatedBytes = 4 * Page::kPageSize; |
| // Time to take for a single area (=payload of page). Used as soon as there |
| // exist enough compaction speed samples. |
| const int kTargetMsPerArea = 1; |
| |
| if (heap()->ShouldReduceMemory()) { |
| *target_fragmentation_percent = kTargetFragmentationPercentForReduceMemory; |
| *max_evacuated_bytes = kMaxEvacuatedBytesForReduceMemory; |
| } else { |
| const intptr_t estimated_compaction_speed = |
| heap()->tracer()->CompactionSpeedInBytesPerMillisecond(); |
| if (estimated_compaction_speed != 0) { |
| // Estimate the target fragmentation based on traced compaction speed |
| // and a goal for a single page. |
| const intptr_t estimated_ms_per_area = |
| 1 + static_cast<intptr_t>(area_size) / estimated_compaction_speed; |
| *target_fragmentation_percent = |
| 100 - 100 * kTargetMsPerArea / estimated_ms_per_area; |
| if (*target_fragmentation_percent < |
| kTargetFragmentationPercentForReduceMemory) { |
| *target_fragmentation_percent = |
| kTargetFragmentationPercentForReduceMemory; |
| } |
| } else { |
| *target_fragmentation_percent = kTargetFragmentationPercent; |
| } |
| *max_evacuated_bytes = kMaxEvacuatedBytes; |
| } |
| } |
| |
| |
| void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) { |
| DCHECK(space->identity() == OLD_SPACE || space->identity() == CODE_SPACE); |
| |
| int number_of_pages = space->CountTotalPages(); |
| int area_size = space->AreaSize(); |
| |
| // Pairs of (live_bytes_in_page, page). |
| typedef std::pair<int, Page*> LiveBytesPagePair; |
| std::vector<LiveBytesPagePair> pages; |
| pages.reserve(number_of_pages); |
| |
| PageIterator it(space); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| if (p->NeverEvacuate()) continue; |
| if (p->IsFlagSet(Page::POPULAR_PAGE)) { |
| // This page had slots buffer overflow on previous GC, skip it. |
| p->ClearFlag(Page::POPULAR_PAGE); |
| continue; |
| } |
| // Invariant: Evacuation candidates are just created when marking is |
| // started. This means that sweeping has finished. Furthermore, at the end |
| // of a GC all evacuation candidates are cleared and their slot buffers are |
| // released. |
| CHECK(!p->IsEvacuationCandidate()); |
| CHECK(p->slots_buffer() == nullptr); |
| CHECK(p->SweepingDone()); |
| DCHECK(p->area_size() == area_size); |
| pages.push_back(std::make_pair(p->LiveBytesFromFreeList(), p)); |
| } |
| |
| int candidate_count = 0; |
| int total_live_bytes = 0; |
| |
| const bool reduce_memory = heap()->ShouldReduceMemory(); |
| if (FLAG_manual_evacuation_candidates_selection) { |
| for (size_t i = 0; i < pages.size(); i++) { |
| Page* p = pages[i].second; |
| if (p->IsFlagSet(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING)) { |
| candidate_count++; |
| total_live_bytes += pages[i].first; |
| p->ClearFlag(MemoryChunk::FORCE_EVACUATION_CANDIDATE_FOR_TESTING); |
| AddEvacuationCandidate(p); |
| } |
| } |
| } else if (FLAG_stress_compaction) { |
| for (size_t i = 0; i < pages.size(); i++) { |
| Page* p = pages[i].second; |
| if (i % 2 == 0) { |
| candidate_count++; |
| total_live_bytes += pages[i].first; |
| AddEvacuationCandidate(p); |
| } |
| } |
| } else { |
| // The following approach determines the pages that should be evacuated. |
| // |
| // We use two conditions to decide whether a page qualifies as an evacuation |
| // candidate, or not: |
| // * Target fragmentation: How fragmented is a page, i.e., how is the ratio |
| // between live bytes and capacity of this page (= area). |
| // * Evacuation quota: A global quota determining how much bytes should be |
| // compacted. |
| // |
| // The algorithm sorts all pages by live bytes and then iterates through |
| // them starting with the page with the most free memory, adding them to the |
| // set of evacuation candidates as long as both conditions (fragmentation |
| // and quota) hold. |
| int max_evacuated_bytes; |
| int target_fragmentation_percent; |
| ComputeEvacuationHeuristics(area_size, &target_fragmentation_percent, |
| &max_evacuated_bytes); |
| |
| const intptr_t free_bytes_threshold = |
| target_fragmentation_percent * (area_size / 100); |
| |
| // Sort pages from the most free to the least free, then select |
| // the first n pages for evacuation such that: |
| // - the total size of evacuated objects does not exceed the specified |
| // limit. |
| // - fragmentation of (n+1)-th page does not exceed the specified limit. |
| std::sort(pages.begin(), pages.end(), |
| [](const LiveBytesPagePair& a, const LiveBytesPagePair& b) { |
| return a.first < b.first; |
| }); |
| for (size_t i = 0; i < pages.size(); i++) { |
| int live_bytes = pages[i].first; |
| int free_bytes = area_size - live_bytes; |
| if (FLAG_always_compact || |
| ((free_bytes >= free_bytes_threshold) && |
| ((total_live_bytes + live_bytes) <= max_evacuated_bytes))) { |
| candidate_count++; |
| total_live_bytes += live_bytes; |
| } |
| if (FLAG_trace_fragmentation_verbose) { |
| PrintIsolate(isolate(), |
| "compaction-selection-page: space=%s free_bytes_page=%d " |
| "fragmentation_limit_kb=%d fragmentation_limit_percent=%d " |
| "sum_compaction_kb=%d " |
| "compaction_limit_kb=%d\n", |
| AllocationSpaceName(space->identity()), free_bytes / KB, |
| free_bytes_threshold / KB, target_fragmentation_percent, |
| total_live_bytes / KB, max_evacuated_bytes / KB); |
| } |
| } |
| // How many pages we will allocated for the evacuated objects |
| // in the worst case: ceil(total_live_bytes / area_size) |
| int estimated_new_pages = (total_live_bytes + area_size - 1) / area_size; |
| DCHECK_LE(estimated_new_pages, candidate_count); |
| int estimated_released_pages = candidate_count - estimated_new_pages; |
| // Avoid (compact -> expand) cycles. |
| if ((estimated_released_pages == 0) && !FLAG_always_compact) { |
| candidate_count = 0; |
| } |
| for (int i = 0; i < candidate_count; i++) { |
| AddEvacuationCandidate(pages[i].second); |
| } |
| } |
| |
| if (FLAG_trace_fragmentation) { |
| PrintIsolate(isolate(), |
| "compaction-selection: space=%s reduce_memory=%d pages=%d " |
| "total_live_bytes=%d\n", |
| AllocationSpaceName(space->identity()), reduce_memory, |
| candidate_count, total_live_bytes / KB); |
| } |
| } |
| |
| |
| void MarkCompactCollector::AbortCompaction() { |
| if (compacting_) { |
| for (Page* p : evacuation_candidates_) { |
| slots_buffer_allocator_->DeallocateChain(p->slots_buffer_address()); |
| p->ClearEvacuationCandidate(); |
| p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION); |
| } |
| compacting_ = false; |
| evacuation_candidates_.Rewind(0); |
| } |
| DCHECK_EQ(0, evacuation_candidates_.length()); |
| } |
| |
| |
| void MarkCompactCollector::Prepare() { |
| was_marked_incrementally_ = heap()->incremental_marking()->IsMarking(); |
| |
| #ifdef DEBUG |
| DCHECK(state_ == IDLE); |
| state_ = PREPARE_GC; |
| #endif |
| |
| DCHECK(!FLAG_never_compact || !FLAG_always_compact); |
| |
| if (sweeping_in_progress()) { |
| // Instead of waiting we could also abort the sweeper threads here. |
| EnsureSweepingCompleted(); |
| } |
| |
| // If concurrent unmapping tasks are still running, we should wait for |
| // them here. |
| heap()->WaitUntilUnmappingOfFreeChunksCompleted(); |
| |
| // Clear marking bits if incremental marking is aborted. |
| if (was_marked_incrementally_ && heap_->ShouldAbortIncrementalMarking()) { |
| heap()->incremental_marking()->Stop(); |
| ClearMarkbits(); |
| AbortWeakCollections(); |
| AbortWeakCells(); |
| AbortTransitionArrays(); |
| AbortCompaction(); |
| was_marked_incrementally_ = false; |
| } |
| |
| // Don't start compaction if we are in the middle of incremental |
| // marking cycle. We did not collect any slots. |
| if (!FLAG_never_compact && !was_marked_incrementally_) { |
| StartCompaction(NON_INCREMENTAL_COMPACTION); |
| } |
| |
| PagedSpaces spaces(heap()); |
| for (PagedSpace* space = spaces.next(); space != NULL; |
| space = spaces.next()) { |
| space->PrepareForMarkCompact(); |
| } |
| |
| #ifdef VERIFY_HEAP |
| if (!was_marked_incrementally_ && FLAG_verify_heap) { |
| VerifyMarkbitsAreClean(); |
| } |
| #endif |
| } |
| |
| |
| void MarkCompactCollector::Finish() { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_FINISH); |
| |
| // The hashing of weak_object_to_code_table is no longer valid. |
| heap()->weak_object_to_code_table()->Rehash( |
| heap()->isolate()->factory()->undefined_value()); |
| |
| // Clear the marking state of live large objects. |
| heap_->lo_space()->ClearMarkingStateOfLiveObjects(); |
| |
| #ifdef DEBUG |
| DCHECK(state_ == SWEEP_SPACES || state_ == RELOCATE_OBJECTS); |
| state_ = IDLE; |
| #endif |
| heap_->isolate()->inner_pointer_to_code_cache()->Flush(); |
| |
| // The stub cache is not traversed during GC; clear the cache to |
| // force lazy re-initialization of it. This must be done after the |
| // GC, because it relies on the new address of certain old space |
| // objects (empty string, illegal builtin). |
| isolate()->stub_cache()->Clear(); |
| |
| if (have_code_to_deoptimize_) { |
| // Some code objects were marked for deoptimization during the GC. |
| Deoptimizer::DeoptimizeMarkedCode(isolate()); |
| have_code_to_deoptimize_ = false; |
| } |
| |
| heap_->incremental_marking()->ClearIdleMarkingDelayCounter(); |
| |
| if (marking_parity_ == EVEN_MARKING_PARITY) { |
| marking_parity_ = ODD_MARKING_PARITY; |
| } else { |
| DCHECK(marking_parity_ == ODD_MARKING_PARITY); |
| marking_parity_ = EVEN_MARKING_PARITY; |
| } |
| } |
| |
| |
| // ------------------------------------------------------------------------- |
| // Phase 1: tracing and marking live objects. |
| // before: all objects are in normal state. |
| // after: a live object's map pointer is marked as '00'. |
| |
| // Marking all live objects in the heap as part of mark-sweep or mark-compact |
| // collection. Before marking, all objects are in their normal state. After |
| // marking, live objects' map pointers are marked indicating that the object |
| // has been found reachable. |
| // |
| // The marking algorithm is a (mostly) depth-first (because of possible stack |
| // overflow) traversal of the graph of objects reachable from the roots. It |
| // uses an explicit stack of pointers rather than recursion. The young |
| // generation's inactive ('from') space is used as a marking stack. The |
| // objects in the marking stack are the ones that have been reached and marked |
| // but their children have not yet been visited. |
| // |
| // The marking stack can overflow during traversal. In that case, we set an |
| // overflow flag. When the overflow flag is set, we continue marking objects |
| // reachable from the objects on the marking stack, but no longer push them on |
| // the marking stack. Instead, we mark them as both marked and overflowed. |
| // When the stack is in the overflowed state, objects marked as overflowed |
| // have been reached and marked but their children have not been visited yet. |
| // After emptying the marking stack, we clear the overflow flag and traverse |
| // the heap looking for objects marked as overflowed, push them on the stack, |
| // and continue with marking. This process repeats until all reachable |
| // objects have been marked. |
| |
| void CodeFlusher::ProcessJSFunctionCandidates() { |
| Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy); |
| Object* undefined = isolate_->heap()->undefined_value(); |
| |
| JSFunction* candidate = jsfunction_candidates_head_; |
| JSFunction* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| ClearNextCandidate(candidate, undefined); |
| |
| SharedFunctionInfo* shared = candidate->shared(); |
| |
| Code* code = shared->code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| if (Marking::IsWhite(code_mark)) { |
| if (FLAG_trace_code_flushing && shared->is_compiled()) { |
| PrintF("[code-flushing clears: "); |
| shared->ShortPrint(); |
| PrintF(" - age: %d]\n", code->GetAge()); |
| } |
| // Always flush the optimized code map if there is one. |
| if (!shared->OptimizedCodeMapIsCleared()) { |
| shared->ClearOptimizedCodeMap(); |
| } |
| shared->set_code(lazy_compile); |
| candidate->set_code(lazy_compile); |
| } else { |
| DCHECK(Marking::IsBlack(code_mark)); |
| candidate->set_code(code); |
| } |
| |
| // We are in the middle of a GC cycle so the write barrier in the code |
| // setter did not record the slot update and we have to do that manually. |
| Address slot = candidate->address() + JSFunction::kCodeEntryOffset; |
| Code* target = Code::cast(Code::GetObjectFromEntryAddress(slot)); |
| isolate_->heap()->mark_compact_collector()->RecordCodeEntrySlot( |
| candidate, slot, target); |
| |
| Object** shared_code_slot = |
| HeapObject::RawField(shared, SharedFunctionInfo::kCodeOffset); |
| isolate_->heap()->mark_compact_collector()->RecordSlot( |
| shared, shared_code_slot, *shared_code_slot); |
| |
| candidate = next_candidate; |
| } |
| |
| jsfunction_candidates_head_ = NULL; |
| } |
| |
| |
| void CodeFlusher::ProcessSharedFunctionInfoCandidates() { |
| Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kCompileLazy); |
| |
| SharedFunctionInfo* candidate = shared_function_info_candidates_head_; |
| SharedFunctionInfo* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| ClearNextCandidate(candidate); |
| |
| Code* code = candidate->code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| if (Marking::IsWhite(code_mark)) { |
| if (FLAG_trace_code_flushing && candidate->is_compiled()) { |
| PrintF("[code-flushing clears: "); |
| candidate->ShortPrint(); |
| PrintF(" - age: %d]\n", code->GetAge()); |
| } |
| // Always flush the optimized code map if there is one. |
| if (!candidate->OptimizedCodeMapIsCleared()) { |
| candidate->ClearOptimizedCodeMap(); |
| } |
| candidate->set_code(lazy_compile); |
| } |
| |
| Object** code_slot = |
| HeapObject::RawField(candidate, SharedFunctionInfo::kCodeOffset); |
| isolate_->heap()->mark_compact_collector()->RecordSlot(candidate, code_slot, |
| *code_slot); |
| |
| candidate = next_candidate; |
| } |
| |
| shared_function_info_candidates_head_ = NULL; |
| } |
| |
| |
| void CodeFlusher::EvictCandidate(SharedFunctionInfo* shared_info) { |
| // Make sure previous flushing decisions are revisited. |
| isolate_->heap()->incremental_marking()->RecordWrites(shared_info); |
| |
| if (FLAG_trace_code_flushing) { |
| PrintF("[code-flushing abandons function-info: "); |
| shared_info->ShortPrint(); |
| PrintF("]\n"); |
| } |
| |
| SharedFunctionInfo* candidate = shared_function_info_candidates_head_; |
| SharedFunctionInfo* next_candidate; |
| if (candidate == shared_info) { |
| next_candidate = GetNextCandidate(shared_info); |
| shared_function_info_candidates_head_ = next_candidate; |
| ClearNextCandidate(shared_info); |
| } else { |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| |
| if (next_candidate == shared_info) { |
| next_candidate = GetNextCandidate(shared_info); |
| SetNextCandidate(candidate, next_candidate); |
| ClearNextCandidate(shared_info); |
| break; |
| } |
| |
| candidate = next_candidate; |
| } |
| } |
| } |
| |
| |
| void CodeFlusher::EvictCandidate(JSFunction* function) { |
| DCHECK(!function->next_function_link()->IsUndefined()); |
| Object* undefined = isolate_->heap()->undefined_value(); |
| |
| // Make sure previous flushing decisions are revisited. |
| isolate_->heap()->incremental_marking()->RecordWrites(function); |
| isolate_->heap()->incremental_marking()->RecordWrites(function->shared()); |
| |
| if (FLAG_trace_code_flushing) { |
| PrintF("[code-flushing abandons closure: "); |
| function->shared()->ShortPrint(); |
| PrintF("]\n"); |
| } |
| |
| JSFunction* candidate = jsfunction_candidates_head_; |
| JSFunction* next_candidate; |
| if (candidate == function) { |
| next_candidate = GetNextCandidate(function); |
| jsfunction_candidates_head_ = next_candidate; |
| ClearNextCandidate(function, undefined); |
| } else { |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| |
| if (next_candidate == function) { |
| next_candidate = GetNextCandidate(function); |
| SetNextCandidate(candidate, next_candidate); |
| ClearNextCandidate(function, undefined); |
| break; |
| } |
| |
| candidate = next_candidate; |
| } |
| } |
| } |
| |
| |
| void CodeFlusher::IteratePointersToFromSpace(ObjectVisitor* v) { |
| Heap* heap = isolate_->heap(); |
| |
| JSFunction** slot = &jsfunction_candidates_head_; |
| JSFunction* candidate = jsfunction_candidates_head_; |
| while (candidate != NULL) { |
| if (heap->InFromSpace(candidate)) { |
| v->VisitPointer(reinterpret_cast<Object**>(slot)); |
| } |
| candidate = GetNextCandidate(*slot); |
| slot = GetNextCandidateSlot(*slot); |
| } |
| } |
| |
| |
| class MarkCompactMarkingVisitor |
| : public StaticMarkingVisitor<MarkCompactMarkingVisitor> { |
| public: |
| static void Initialize(); |
| |
| INLINE(static void VisitPointer(Heap* heap, HeapObject* object, Object** p)) { |
| MarkObjectByPointer(heap->mark_compact_collector(), object, p); |
| } |
| |
| INLINE(static void VisitPointers(Heap* heap, HeapObject* object, |
| Object** start, Object** end)) { |
| // Mark all objects pointed to in [start, end). |
| const int kMinRangeForMarkingRecursion = 64; |
| if (end - start >= kMinRangeForMarkingRecursion) { |
| if (VisitUnmarkedObjects(heap, object, start, end)) return; |
| // We are close to a stack overflow, so just mark the objects. |
| } |
| MarkCompactCollector* collector = heap->mark_compact_collector(); |
| for (Object** p = start; p < end; p++) { |
| MarkObjectByPointer(collector, object, p); |
| } |
| } |
| |
| // Marks the object black and pushes it on the marking stack. |
| INLINE(static void MarkObject(Heap* heap, HeapObject* object)) { |
| MarkBit mark = Marking::MarkBitFrom(object); |
| heap->mark_compact_collector()->MarkObject(object, mark); |
| } |
| |
| // Marks the object black without pushing it on the marking stack. |
| // Returns true if object needed marking and false otherwise. |
| INLINE(static bool MarkObjectWithoutPush(Heap* heap, HeapObject* object)) { |
| MarkBit mark_bit = Marking::MarkBitFrom(object); |
| if (Marking::IsWhite(mark_bit)) { |
| heap->mark_compact_collector()->SetMark(object, mark_bit); |
| return true; |
| } |
| return false; |
| } |
| |
| // Mark object pointed to by p. |
| INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector, |
| HeapObject* object, Object** p)) { |
| if (!(*p)->IsHeapObject()) return; |
| HeapObject* target_object = HeapObject::cast(*p); |
| collector->RecordSlot(object, p, target_object); |
| MarkBit mark = Marking::MarkBitFrom(target_object); |
| collector->MarkObject(target_object, mark); |
| } |
| |
| |
| // Visit an unmarked object. |
| INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector, |
| HeapObject* obj)) { |
| #ifdef DEBUG |
| DCHECK(collector->heap()->Contains(obj)); |
| DCHECK(!collector->heap()->mark_compact_collector()->IsMarked(obj)); |
| #endif |
| Map* map = obj->map(); |
| Heap* heap = obj->GetHeap(); |
| MarkBit mark = Marking::MarkBitFrom(obj); |
| heap->mark_compact_collector()->SetMark(obj, mark); |
| // Mark the map pointer and the body. |
| MarkBit map_mark = Marking::MarkBitFrom(map); |
| heap->mark_compact_collector()->MarkObject(map, map_mark); |
| IterateBody(map, obj); |
| } |
| |
| // Visit all unmarked objects pointed to by [start, end). |
| // Returns false if the operation fails (lack of stack space). |
| INLINE(static bool VisitUnmarkedObjects(Heap* heap, HeapObject* object, |
| Object** start, Object** end)) { |
| // Return false is we are close to the stack limit. |
| StackLimitCheck check(heap->isolate()); |
| if (check.HasOverflowed()) return false; |
| |
| MarkCompactCollector* collector = heap->mark_compact_collector(); |
| // Visit the unmarked objects. |
| for (Object** p = start; p < end; p++) { |
| Object* o = *p; |
| if (!o->IsHeapObject()) continue; |
| collector->RecordSlot(object, p, o); |
| HeapObject* obj = HeapObject::cast(o); |
| MarkBit mark = Marking::MarkBitFrom(obj); |
| if (Marking::IsBlackOrGrey(mark)) continue; |
| VisitUnmarkedObject(collector, obj); |
| } |
| return true; |
| } |
| |
| private: |
| // Code flushing support. |
| |
| static const int kRegExpCodeThreshold = 5; |
| |
| static void UpdateRegExpCodeAgeAndFlush(Heap* heap, JSRegExp* re, |
| bool is_one_byte) { |
| // Make sure that the fixed array is in fact initialized on the RegExp. |
| // We could potentially trigger a GC when initializing the RegExp. |
| if (HeapObject::cast(re->data())->map()->instance_type() != |
| FIXED_ARRAY_TYPE) |
| return; |
| |
| // Make sure this is a RegExp that actually contains code. |
| if (re->TypeTag() != JSRegExp::IRREGEXP) return; |
| |
| Object* code = re->DataAt(JSRegExp::code_index(is_one_byte)); |
| if (!code->IsSmi() && |
| HeapObject::cast(code)->map()->instance_type() == CODE_TYPE) { |
| // Save a copy that can be reinstated if we need the code again. |
| re->SetDataAt(JSRegExp::saved_code_index(is_one_byte), code); |
| |
| // Saving a copy might create a pointer into compaction candidate |
| // that was not observed by marker. This might happen if JSRegExp data |
| // was marked through the compilation cache before marker reached JSRegExp |
| // object. |
| FixedArray* data = FixedArray::cast(re->data()); |
| Object** slot = |
| data->data_start() + JSRegExp::saved_code_index(is_one_byte); |
| heap->mark_compact_collector()->RecordSlot(data, slot, code); |
| |
| // Set a number in the 0-255 range to guarantee no smi overflow. |
| re->SetDataAt(JSRegExp::code_index(is_one_byte), |
| Smi::FromInt(heap->ms_count() & 0xff)); |
| } else if (code->IsSmi()) { |
| int value = Smi::cast(code)->value(); |
| // The regexp has not been compiled yet or there was a compilation error. |
| if (value == JSRegExp::kUninitializedValue || |
| value == JSRegExp::kCompilationErrorValue) { |
| return; |
| } |
| |
| // Check if we should flush now. |
| if (value == ((heap->ms_count() - kRegExpCodeThreshold) & 0xff)) { |
| re->SetDataAt(JSRegExp::code_index(is_one_byte), |
| Smi::FromInt(JSRegExp::kUninitializedValue)); |
| re->SetDataAt(JSRegExp::saved_code_index(is_one_byte), |
| Smi::FromInt(JSRegExp::kUninitializedValue)); |
| } |
| } |
| } |
| |
| |
| // Works by setting the current sweep_generation (as a smi) in the |
| // code object place in the data array of the RegExp and keeps a copy |
| // around that can be reinstated if we reuse the RegExp before flushing. |
| // If we did not use the code for kRegExpCodeThreshold mark sweep GCs |
| // we flush the code. |
| static void VisitRegExpAndFlushCode(Map* map, HeapObject* object) { |
| Heap* heap = map->GetHeap(); |
| MarkCompactCollector* collector = heap->mark_compact_collector(); |
| if (!collector->is_code_flushing_enabled()) { |
| VisitJSRegExp(map, object); |
| return; |
| } |
| JSRegExp* re = reinterpret_cast<JSRegExp*>(object); |
| // Flush code or set age on both one byte and two byte code. |
| UpdateRegExpCodeAgeAndFlush(heap, re, true); |
| UpdateRegExpCodeAgeAndFlush(heap, re, false); |
| // Visit the fields of the RegExp, including the updated FixedArray. |
| VisitJSRegExp(map, object); |
| } |
| }; |
| |
| |
| void MarkCompactMarkingVisitor::Initialize() { |
| StaticMarkingVisitor<MarkCompactMarkingVisitor>::Initialize(); |
| |
| table_.Register(kVisitJSRegExp, &VisitRegExpAndFlushCode); |
| |
| if (FLAG_track_gc_object_stats) { |
| ObjectStatsVisitor::Initialize(&table_); |
| } |
| } |
| |
| |
| class CodeMarkingVisitor : public ThreadVisitor { |
| public: |
| explicit CodeMarkingVisitor(MarkCompactCollector* collector) |
| : collector_(collector) {} |
| |
| void VisitThread(Isolate* isolate, ThreadLocalTop* top) { |
| collector_->PrepareThreadForCodeFlushing(isolate, top); |
| } |
| |
| private: |
| MarkCompactCollector* collector_; |
| }; |
| |
| |
| class SharedFunctionInfoMarkingVisitor : public ObjectVisitor { |
| public: |
| explicit SharedFunctionInfoMarkingVisitor(MarkCompactCollector* collector) |
| : collector_(collector) {} |
| |
| void VisitPointers(Object** start, Object** end) override { |
| for (Object** p = start; p < end; p++) VisitPointer(p); |
| } |
| |
| void VisitPointer(Object** slot) override { |
| Object* obj = *slot; |
| if (obj->IsSharedFunctionInfo()) { |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(obj); |
| MarkBit shared_mark = Marking::MarkBitFrom(shared); |
| MarkBit code_mark = Marking::MarkBitFrom(shared->code()); |
| collector_->MarkObject(shared->code(), code_mark); |
| collector_->MarkObject(shared, shared_mark); |
| } |
| } |
| |
| private: |
| MarkCompactCollector* collector_; |
| }; |
| |
| |
| void MarkCompactCollector::PrepareThreadForCodeFlushing(Isolate* isolate, |
| ThreadLocalTop* top) { |
| for (StackFrameIterator it(isolate, top); !it.done(); it.Advance()) { |
| // Note: for the frame that has a pending lazy deoptimization |
| // StackFrame::unchecked_code will return a non-optimized code object for |
| // the outermost function and StackFrame::LookupCode will return |
| // actual optimized code object. |
| StackFrame* frame = it.frame(); |
| Code* code = frame->unchecked_code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| MarkObject(code, code_mark); |
| if (frame->is_optimized()) { |
| Code* optimized_code = frame->LookupCode(); |
| MarkBit optimized_code_mark = Marking::MarkBitFrom(optimized_code); |
| MarkObject(optimized_code, optimized_code_mark); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::PrepareForCodeFlushing() { |
| // If code flushing is disabled, there is no need to prepare for it. |
| if (!is_code_flushing_enabled()) return; |
| |
| // Ensure that empty descriptor array is marked. Method MarkDescriptorArray |
| // relies on it being marked before any other descriptor array. |
| HeapObject* descriptor_array = heap()->empty_descriptor_array(); |
| MarkBit descriptor_array_mark = Marking::MarkBitFrom(descriptor_array); |
| MarkObject(descriptor_array, descriptor_array_mark); |
| |
| // Make sure we are not referencing the code from the stack. |
| DCHECK(this == heap()->mark_compact_collector()); |
| PrepareThreadForCodeFlushing(heap()->isolate(), |
| heap()->isolate()->thread_local_top()); |
| |
| // Iterate the archived stacks in all threads to check if |
| // the code is referenced. |
| CodeMarkingVisitor code_marking_visitor(this); |
| heap()->isolate()->thread_manager()->IterateArchivedThreads( |
| &code_marking_visitor); |
| |
| SharedFunctionInfoMarkingVisitor visitor(this); |
| heap()->isolate()->compilation_cache()->IterateFunctions(&visitor); |
| heap()->isolate()->handle_scope_implementer()->Iterate(&visitor); |
| |
| ProcessMarkingDeque(); |
| } |
| |
| |
| // Visitor class for marking heap roots. |
| class RootMarkingVisitor : public ObjectVisitor { |
| public: |
| explicit RootMarkingVisitor(Heap* heap) |
| : collector_(heap->mark_compact_collector()) {} |
| |
| void VisitPointer(Object** p) override { MarkObjectByPointer(p); } |
| |
| void VisitPointers(Object** start, Object** end) override { |
| for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| } |
| |
| // Skip the weak next code link in a code object, which is visited in |
| // ProcessTopOptimizedFrame. |
| void VisitNextCodeLink(Object** p) override {} |
| |
| private: |
| void MarkObjectByPointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| // Replace flat cons strings in place. |
| HeapObject* object = HeapObject::cast(*p); |
| MarkBit mark_bit = Marking::MarkBitFrom(object); |
| if (Marking::IsBlackOrGrey(mark_bit)) return; |
| |
| Map* map = object->map(); |
| // Mark the object. |
| collector_->SetMark(object, mark_bit); |
| |
| // Mark the map pointer and body, and push them on the marking stack. |
| MarkBit map_mark = Marking::MarkBitFrom(map); |
| collector_->MarkObject(map, map_mark); |
| MarkCompactMarkingVisitor::IterateBody(map, object); |
| |
| // Mark all the objects reachable from the map and body. May leave |
| // overflowed objects in the heap. |
| collector_->EmptyMarkingDeque(); |
| } |
| |
| MarkCompactCollector* collector_; |
| }; |
| |
| |
| // Helper class for pruning the string table. |
| template <bool finalize_external_strings> |
| class StringTableCleaner : public ObjectVisitor { |
| public: |
| explicit StringTableCleaner(Heap* heap) : heap_(heap), pointers_removed_(0) {} |
| |
| void VisitPointers(Object** start, Object** end) override { |
| // Visit all HeapObject pointers in [start, end). |
| for (Object** p = start; p < end; p++) { |
| Object* o = *p; |
| if (o->IsHeapObject() && |
| Marking::IsWhite(Marking::MarkBitFrom(HeapObject::cast(o)))) { |
| if (finalize_external_strings) { |
| DCHECK(o->IsExternalString()); |
| heap_->FinalizeExternalString(String::cast(*p)); |
| } else { |
| pointers_removed_++; |
| } |
| // Set the entry to the_hole_value (as deleted). |
| *p = heap_->the_hole_value(); |
| } |
| } |
| } |
| |
| int PointersRemoved() { |
| DCHECK(!finalize_external_strings); |
| return pointers_removed_; |
| } |
| |
| private: |
| Heap* heap_; |
| int pointers_removed_; |
| }; |
| |
| |
| typedef StringTableCleaner<false> InternalizedStringTableCleaner; |
| typedef StringTableCleaner<true> ExternalStringTableCleaner; |
| |
| |
| // Implementation of WeakObjectRetainer for mark compact GCs. All marked objects |
| // are retained. |
| class MarkCompactWeakObjectRetainer : public WeakObjectRetainer { |
| public: |
| virtual Object* RetainAs(Object* object) { |
| MarkBit mark_bit = Marking::MarkBitFrom(HeapObject::cast(object)); |
| DCHECK(!Marking::IsGrey(mark_bit)); |
| if (Marking::IsBlack(mark_bit)) { |
| return object; |
| } else if (object->IsAllocationSite() && |
| !(AllocationSite::cast(object)->IsZombie())) { |
| // "dead" AllocationSites need to live long enough for a traversal of new |
| // space. These sites get a one-time reprieve. |
| AllocationSite* site = AllocationSite::cast(object); |
| site->MarkZombie(); |
| site->GetHeap()->mark_compact_collector()->MarkAllocationSite(site); |
| return object; |
| } else { |
| return NULL; |
| } |
| } |
| }; |
| |
| |
| // Fill the marking stack with overflowed objects returned by the given |
| // iterator. Stop when the marking stack is filled or the end of the space |
| // is reached, whichever comes first. |
| template <class T> |
| void MarkCompactCollector::DiscoverGreyObjectsWithIterator(T* it) { |
| // The caller should ensure that the marking stack is initially not full, |
| // so that we don't waste effort pointlessly scanning for objects. |
| DCHECK(!marking_deque()->IsFull()); |
| |
| Map* filler_map = heap()->one_pointer_filler_map(); |
| for (HeapObject* object = it->Next(); object != NULL; object = it->Next()) { |
| MarkBit markbit = Marking::MarkBitFrom(object); |
| if ((object->map() != filler_map) && Marking::IsGrey(markbit)) { |
| Marking::GreyToBlack(markbit); |
| PushBlack(object); |
| if (marking_deque()->IsFull()) return; |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::DiscoverGreyObjectsOnPage(MemoryChunk* p) { |
| DCHECK(!marking_deque()->IsFull()); |
| LiveObjectIterator<kGreyObjects> it(p); |
| HeapObject* object = NULL; |
| while ((object = it.Next()) != NULL) { |
| MarkBit markbit = Marking::MarkBitFrom(object); |
| DCHECK(Marking::IsGrey(markbit)); |
| Marking::GreyToBlack(markbit); |
| PushBlack(object); |
| if (marking_deque()->IsFull()) return; |
| } |
| } |
| |
| |
| class MarkCompactCollector::HeapObjectVisitor { |
| public: |
| virtual ~HeapObjectVisitor() {} |
| virtual bool Visit(HeapObject* object) = 0; |
| }; |
| |
| |
| class MarkCompactCollector::EvacuateVisitorBase |
| : public MarkCompactCollector::HeapObjectVisitor { |
| public: |
| EvacuateVisitorBase(Heap* heap, CompactionSpaceCollection* compaction_spaces, |
| SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer) |
| : heap_(heap), |
| evacuation_slots_buffer_(evacuation_slots_buffer), |
| compaction_spaces_(compaction_spaces), |
| local_store_buffer_(local_store_buffer) {} |
| |
| bool TryEvacuateObject(PagedSpace* target_space, HeapObject* object, |
| HeapObject** target_object) { |
| int size = object->Size(); |
| AllocationAlignment alignment = object->RequiredAlignment(); |
| AllocationResult allocation = target_space->AllocateRaw(size, alignment); |
| if (allocation.To(target_object)) { |
| heap_->mark_compact_collector()->MigrateObject( |
| *target_object, object, size, target_space->identity(), |
| evacuation_slots_buffer_, local_store_buffer_); |
| return true; |
| } |
| return false; |
| } |
| |
| protected: |
| Heap* heap_; |
| SlotsBuffer** evacuation_slots_buffer_; |
| CompactionSpaceCollection* compaction_spaces_; |
| LocalStoreBuffer* local_store_buffer_; |
| }; |
| |
| |
| class MarkCompactCollector::EvacuateNewSpaceVisitor final |
| : public MarkCompactCollector::EvacuateVisitorBase { |
| public: |
| static const intptr_t kLabSize = 4 * KB; |
| static const intptr_t kMaxLabObjectSize = 256; |
| |
| explicit EvacuateNewSpaceVisitor(Heap* heap, |
| CompactionSpaceCollection* compaction_spaces, |
| SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer, |
| HashMap* local_pretenuring_feedback) |
| : EvacuateVisitorBase(heap, compaction_spaces, evacuation_slots_buffer, |
| local_store_buffer), |
| buffer_(LocalAllocationBuffer::InvalidBuffer()), |
| space_to_allocate_(NEW_SPACE), |
| promoted_size_(0), |
| semispace_copied_size_(0), |
| local_pretenuring_feedback_(local_pretenuring_feedback) {} |
| |
| bool Visit(HeapObject* object) override { |
| heap_->UpdateAllocationSite<Heap::kCached>(object, |
| local_pretenuring_feedback_); |
| int size = object->Size(); |
| HeapObject* target_object = nullptr; |
| if (heap_->ShouldBePromoted(object->address(), size) && |
| TryEvacuateObject(compaction_spaces_->Get(OLD_SPACE), object, |
| &target_object)) { |
| // If we end up needing more special cases, we should factor this out. |
| if (V8_UNLIKELY(target_object->IsJSArrayBuffer())) { |
| heap_->array_buffer_tracker()->Promote( |
| JSArrayBuffer::cast(target_object)); |
| } |
| promoted_size_ += size; |
| return true; |
| } |
| HeapObject* target = nullptr; |
| AllocationSpace space = AllocateTargetObject(object, &target); |
| heap_->mark_compact_collector()->MigrateObject( |
| HeapObject::cast(target), object, size, space, |
| (space == NEW_SPACE) ? nullptr : evacuation_slots_buffer_, |
| (space == NEW_SPACE) ? nullptr : local_store_buffer_); |
| if (V8_UNLIKELY(target->IsJSArrayBuffer())) { |
| heap_->array_buffer_tracker()->MarkLive(JSArrayBuffer::cast(target)); |
| } |
| semispace_copied_size_ += size; |
| return true; |
| } |
| |
| intptr_t promoted_size() { return promoted_size_; } |
| intptr_t semispace_copied_size() { return semispace_copied_size_; } |
| |
| private: |
| enum NewSpaceAllocationMode { |
| kNonstickyBailoutOldSpace, |
| kStickyBailoutOldSpace, |
| }; |
| |
| inline AllocationSpace AllocateTargetObject(HeapObject* old_object, |
| HeapObject** target_object) { |
| const int size = old_object->Size(); |
| AllocationAlignment alignment = old_object->RequiredAlignment(); |
| AllocationResult allocation; |
| if (space_to_allocate_ == NEW_SPACE) { |
| if (size > kMaxLabObjectSize) { |
| allocation = |
| AllocateInNewSpace(size, alignment, kNonstickyBailoutOldSpace); |
| } else { |
| allocation = AllocateInLab(size, alignment); |
| } |
| } |
| if (allocation.IsRetry() || (space_to_allocate_ == OLD_SPACE)) { |
| allocation = AllocateInOldSpace(size, alignment); |
| } |
| bool ok = allocation.To(target_object); |
| DCHECK(ok); |
| USE(ok); |
| return space_to_allocate_; |
| } |
| |
| inline bool NewLocalAllocationBuffer() { |
| AllocationResult result = |
| AllocateInNewSpace(kLabSize, kWordAligned, kStickyBailoutOldSpace); |
| LocalAllocationBuffer saved_old_buffer = buffer_; |
| buffer_ = LocalAllocationBuffer::FromResult(heap_, result, kLabSize); |
| if (buffer_.IsValid()) { |
| buffer_.TryMerge(&saved_old_buffer); |
| return true; |
| } |
| return false; |
| } |
| |
| inline AllocationResult AllocateInNewSpace(int size_in_bytes, |
| AllocationAlignment alignment, |
| NewSpaceAllocationMode mode) { |
| AllocationResult allocation = |
| heap_->new_space()->AllocateRawSynchronized(size_in_bytes, alignment); |
| if (allocation.IsRetry()) { |
| if (!heap_->new_space()->AddFreshPageSynchronized()) { |
| if (mode == kStickyBailoutOldSpace) space_to_allocate_ = OLD_SPACE; |
| } else { |
| allocation = heap_->new_space()->AllocateRawSynchronized(size_in_bytes, |
| alignment); |
| if (allocation.IsRetry()) { |
| if (mode == kStickyBailoutOldSpace) space_to_allocate_ = OLD_SPACE; |
| } |
| } |
| } |
| return allocation; |
| } |
| |
| inline AllocationResult AllocateInOldSpace(int size_in_bytes, |
| AllocationAlignment alignment) { |
| AllocationResult allocation = |
| compaction_spaces_->Get(OLD_SPACE)->AllocateRaw(size_in_bytes, |
| alignment); |
| if (allocation.IsRetry()) { |
| FatalProcessOutOfMemory( |
| "MarkCompactCollector: semi-space copy, fallback in old gen\n"); |
| } |
| return allocation; |
| } |
| |
| inline AllocationResult AllocateInLab(int size_in_bytes, |
| AllocationAlignment alignment) { |
| AllocationResult allocation; |
| if (!buffer_.IsValid()) { |
| if (!NewLocalAllocationBuffer()) { |
| space_to_allocate_ = OLD_SPACE; |
| return AllocationResult::Retry(OLD_SPACE); |
| } |
| } |
| allocation = buffer_.AllocateRawAligned(size_in_bytes, alignment); |
| if (allocation.IsRetry()) { |
| if (!NewLocalAllocationBuffer()) { |
| space_to_allocate_ = OLD_SPACE; |
| return AllocationResult::Retry(OLD_SPACE); |
| } else { |
| allocation = buffer_.AllocateRawAligned(size_in_bytes, alignment); |
| if (allocation.IsRetry()) { |
| space_to_allocate_ = OLD_SPACE; |
| return AllocationResult::Retry(OLD_SPACE); |
| } |
| } |
| } |
| return allocation; |
| } |
| |
| LocalAllocationBuffer buffer_; |
| AllocationSpace space_to_allocate_; |
| intptr_t promoted_size_; |
| intptr_t semispace_copied_size_; |
| HashMap* local_pretenuring_feedback_; |
| }; |
| |
| |
| class MarkCompactCollector::EvacuateOldSpaceVisitor final |
| : public MarkCompactCollector::EvacuateVisitorBase { |
| public: |
| EvacuateOldSpaceVisitor(Heap* heap, |
| CompactionSpaceCollection* compaction_spaces, |
| SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer) |
| : EvacuateVisitorBase(heap, compaction_spaces, evacuation_slots_buffer, |
| local_store_buffer) {} |
| |
| bool Visit(HeapObject* object) override { |
| CompactionSpace* target_space = compaction_spaces_->Get( |
| Page::FromAddress(object->address())->owner()->identity()); |
| HeapObject* target_object = nullptr; |
| if (TryEvacuateObject(target_space, object, &target_object)) { |
| DCHECK(object->map_word().IsForwardingAddress()); |
| return true; |
| } |
| return false; |
| } |
| }; |
| |
| |
| void MarkCompactCollector::DiscoverGreyObjectsInSpace(PagedSpace* space) { |
| PageIterator it(space); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| DiscoverGreyObjectsOnPage(p); |
| if (marking_deque()->IsFull()) return; |
| } |
| } |
| |
| |
| void MarkCompactCollector::DiscoverGreyObjectsInNewSpace() { |
| NewSpace* space = heap()->new_space(); |
| NewSpacePageIterator it(space->bottom(), space->top()); |
| while (it.has_next()) { |
| NewSpacePage* page = it.next(); |
| DiscoverGreyObjectsOnPage(page); |
| if (marking_deque()->IsFull()) return; |
| } |
| } |
| |
| |
| bool MarkCompactCollector::IsUnmarkedHeapObject(Object** p) { |
| Object* o = *p; |
| if (!o->IsHeapObject()) return false; |
| HeapObject* heap_object = HeapObject::cast(o); |
| MarkBit mark = Marking::MarkBitFrom(heap_object); |
| return Marking::IsWhite(mark); |
| } |
| |
| |
| bool MarkCompactCollector::IsUnmarkedHeapObjectWithHeap(Heap* heap, |
| Object** p) { |
| Object* o = *p; |
| DCHECK(o->IsHeapObject()); |
| HeapObject* heap_object = HeapObject::cast(o); |
| MarkBit mark = Marking::MarkBitFrom(heap_object); |
| return Marking::IsWhite(mark); |
| } |
| |
| |
| void MarkCompactCollector::MarkStringTable(RootMarkingVisitor* visitor) { |
| StringTable* string_table = heap()->string_table(); |
| // Mark the string table itself. |
| MarkBit string_table_mark = Marking::MarkBitFrom(string_table); |
| if (Marking::IsWhite(string_table_mark)) { |
| // String table could have already been marked by visiting the handles list. |
| SetMark(string_table, string_table_mark); |
| } |
| // Explicitly mark the prefix. |
| string_table->IteratePrefix(visitor); |
| ProcessMarkingDeque(); |
| } |
| |
| |
| void MarkCompactCollector::MarkAllocationSite(AllocationSite* site) { |
| MarkBit mark_bit = Marking::MarkBitFrom(site); |
| SetMark(site, mark_bit); |
| } |
| |
| |
| void MarkCompactCollector::MarkRoots(RootMarkingVisitor* visitor) { |
| // Mark the heap roots including global variables, stack variables, |
| // etc., and all objects reachable from them. |
| heap()->IterateStrongRoots(visitor, VISIT_ONLY_STRONG); |
| |
| // Handle the string table specially. |
| MarkStringTable(visitor); |
| |
| // There may be overflowed objects in the heap. Visit them now. |
| while (marking_deque_.overflowed()) { |
| RefillMarkingDeque(); |
| EmptyMarkingDeque(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkImplicitRefGroups( |
| MarkObjectFunction mark_object) { |
| List<ImplicitRefGroup*>* ref_groups = |
| isolate()->global_handles()->implicit_ref_groups(); |
| |
| int last = 0; |
| for (int i = 0; i < ref_groups->length(); i++) { |
| ImplicitRefGroup* entry = ref_groups->at(i); |
| DCHECK(entry != NULL); |
| |
| if (!IsMarked(*entry->parent)) { |
| (*ref_groups)[last++] = entry; |
| continue; |
| } |
| |
| Object*** children = entry->children; |
| // A parent object is marked, so mark all child heap objects. |
| for (size_t j = 0; j < entry->length; ++j) { |
| if ((*children[j])->IsHeapObject()) { |
| mark_object(heap(), HeapObject::cast(*children[j])); |
| } |
| } |
| |
| // Once the entire group has been marked, dispose it because it's |
| // not needed anymore. |
| delete entry; |
| } |
| ref_groups->Rewind(last); |
| } |
| |
| |
| // Mark all objects reachable from the objects on the marking stack. |
| // Before: the marking stack contains zero or more heap object pointers. |
| // After: the marking stack is empty, and all objects reachable from the |
| // marking stack have been marked, or are overflowed in the heap. |
| void MarkCompactCollector::EmptyMarkingDeque() { |
| Map* filler_map = heap_->one_pointer_filler_map(); |
| while (!marking_deque_.IsEmpty()) { |
| HeapObject* object = marking_deque_.Pop(); |
| // Explicitly skip one word fillers. Incremental markbit patterns are |
| // correct only for objects that occupy at least two words. |
| Map* map = object->map(); |
| if (map == filler_map) continue; |
| |
| DCHECK(object->IsHeapObject()); |
| DCHECK(heap()->Contains(object)); |
| DCHECK(!Marking::IsWhite(Marking::MarkBitFrom(object))); |
| |
| MarkBit map_mark = Marking::MarkBitFrom(map); |
| MarkObject(map, map_mark); |
| |
| MarkCompactMarkingVisitor::IterateBody(map, object); |
| } |
| } |
| |
| |
| // Sweep the heap for overflowed objects, clear their overflow bits, and |
| // push them on the marking stack. Stop early if the marking stack fills |
| // before sweeping completes. If sweeping completes, there are no remaining |
| // overflowed objects in the heap so the overflow flag on the markings stack |
| // is cleared. |
| void MarkCompactCollector::RefillMarkingDeque() { |
| isolate()->CountUsage(v8::Isolate::UseCounterFeature::kMarkDequeOverflow); |
| DCHECK(marking_deque_.overflowed()); |
| |
| DiscoverGreyObjectsInNewSpace(); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap()->old_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap()->code_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap()->map_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| LargeObjectIterator lo_it(heap()->lo_space()); |
| DiscoverGreyObjectsWithIterator(&lo_it); |
| if (marking_deque_.IsFull()) return; |
| |
| marking_deque_.ClearOverflowed(); |
| } |
| |
| |
| // Mark all objects reachable (transitively) from objects on the marking |
| // stack. Before: the marking stack contains zero or more heap object |
| // pointers. After: the marking stack is empty and there are no overflowed |
| // objects in the heap. |
| void MarkCompactCollector::ProcessMarkingDeque() { |
| EmptyMarkingDeque(); |
| while (marking_deque_.overflowed()) { |
| RefillMarkingDeque(); |
| EmptyMarkingDeque(); |
| } |
| } |
| |
| |
| // Mark all objects reachable (transitively) from objects on the marking |
| // stack including references only considered in the atomic marking pause. |
| void MarkCompactCollector::ProcessEphemeralMarking( |
| ObjectVisitor* visitor, bool only_process_harmony_weak_collections) { |
| bool work_to_do = true; |
| DCHECK(marking_deque_.IsEmpty() && !marking_deque_.overflowed()); |
| while (work_to_do) { |
| if (!only_process_harmony_weak_collections) { |
| isolate()->global_handles()->IterateObjectGroups( |
| visitor, &IsUnmarkedHeapObjectWithHeap); |
| MarkImplicitRefGroups(&MarkCompactMarkingVisitor::MarkObject); |
| } |
| ProcessWeakCollections(); |
| work_to_do = !marking_deque_.IsEmpty(); |
| ProcessMarkingDeque(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) { |
| for (StackFrameIterator it(isolate(), isolate()->thread_local_top()); |
| !it.done(); it.Advance()) { |
| if (it.frame()->type() == StackFrame::JAVA_SCRIPT) { |
| return; |
| } |
| if (it.frame()->type() == StackFrame::OPTIMIZED) { |
| Code* code = it.frame()->LookupCode(); |
| if (!code->CanDeoptAt(it.frame()->pc())) { |
| Code::BodyDescriptor::IterateBody(code, visitor); |
| } |
| ProcessMarkingDeque(); |
| return; |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::EnsureMarkingDequeIsReserved() { |
| DCHECK(!marking_deque_.in_use()); |
| if (marking_deque_memory_ == NULL) { |
| marking_deque_memory_ = new base::VirtualMemory(kMaxMarkingDequeSize); |
| marking_deque_memory_committed_ = 0; |
| } |
| if (marking_deque_memory_ == NULL) { |
| V8::FatalProcessOutOfMemory("EnsureMarkingDequeIsReserved"); |
| } |
| } |
| |
| |
| void MarkCompactCollector::EnsureMarkingDequeIsCommitted(size_t max_size) { |
| // If the marking deque is too small, we try to allocate a bigger one. |
| // If that fails, make do with a smaller one. |
| CHECK(!marking_deque_.in_use()); |
| for (size_t size = max_size; size >= kMinMarkingDequeSize; size >>= 1) { |
| base::VirtualMemory* memory = marking_deque_memory_; |
| size_t currently_committed = marking_deque_memory_committed_; |
| |
| if (currently_committed == size) return; |
| |
| if (currently_committed > size) { |
| bool success = marking_deque_memory_->Uncommit( |
| reinterpret_cast<Address>(marking_deque_memory_->address()) + size, |
| currently_committed - size); |
| if (success) { |
| marking_deque_memory_committed_ = size; |
| return; |
| } |
| UNREACHABLE(); |
| } |
| |
| bool success = memory->Commit( |
| reinterpret_cast<Address>(memory->address()) + currently_committed, |
| size - currently_committed, |
| false); // Not executable. |
| if (success) { |
| marking_deque_memory_committed_ = size; |
| return; |
| } |
| } |
| V8::FatalProcessOutOfMemory("EnsureMarkingDequeIsCommitted"); |
| } |
| |
| |
| void MarkCompactCollector::InitializeMarkingDeque() { |
| DCHECK(!marking_deque_.in_use()); |
| DCHECK(marking_deque_memory_committed_ > 0); |
| Address addr = static_cast<Address>(marking_deque_memory_->address()); |
| size_t size = marking_deque_memory_committed_; |
| if (FLAG_force_marking_deque_overflows) size = 64 * kPointerSize; |
| marking_deque_.Initialize(addr, addr + size); |
| } |
| |
| |
| void MarkingDeque::Initialize(Address low, Address high) { |
| DCHECK(!in_use_); |
| HeapObject** obj_low = reinterpret_cast<HeapObject**>(low); |
| HeapObject** obj_high = reinterpret_cast<HeapObject**>(high); |
| array_ = obj_low; |
| mask_ = base::bits::RoundDownToPowerOfTwo32( |
| static_cast<uint32_t>(obj_high - obj_low)) - |
| 1; |
| top_ = bottom_ = 0; |
| overflowed_ = false; |
| in_use_ = true; |
| } |
| |
| |
| void MarkingDeque::Uninitialize(bool aborting) { |
| if (!aborting) { |
| DCHECK(IsEmpty()); |
| DCHECK(!overflowed_); |
| } |
| DCHECK(in_use_); |
| top_ = bottom_ = 0xdecbad; |
| in_use_ = false; |
| } |
| |
| |
| void MarkCompactCollector::MarkLiveObjects() { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_MARK); |
| double start_time = 0.0; |
| if (FLAG_print_cumulative_gc_stat) { |
| start_time = heap_->MonotonicallyIncreasingTimeInMs(); |
| } |
| // The recursive GC marker detects when it is nearing stack overflow, |
| // and switches to a different marking system. JS interrupts interfere |
| // with the C stack limit check. |
| PostponeInterruptsScope postpone(isolate()); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_MARK_FINISH_INCREMENTAL); |
| IncrementalMarking* incremental_marking = heap_->incremental_marking(); |
| if (was_marked_incrementally_) { |
| incremental_marking->Finalize(); |
| } else { |
| // Abort any pending incremental activities e.g. incremental sweeping. |
| incremental_marking->Stop(); |
| if (marking_deque_.in_use()) { |
| marking_deque_.Uninitialize(true); |
| } |
| } |
| } |
| |
| #ifdef DEBUG |
| DCHECK(state_ == PREPARE_GC); |
| state_ = MARK_LIVE_OBJECTS; |
| #endif |
| |
| EnsureMarkingDequeIsCommittedAndInitialize( |
| MarkCompactCollector::kMaxMarkingDequeSize); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_MARK_PREPARE_CODE_FLUSH); |
| PrepareForCodeFlushing(); |
| } |
| |
| RootMarkingVisitor root_visitor(heap()); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_MARK_ROOTS); |
| MarkRoots(&root_visitor); |
| ProcessTopOptimizedFrame(&root_visitor); |
| } |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_MARK_WEAK_CLOSURE); |
| |
| // The objects reachable from the roots are marked, yet unreachable |
| // objects are unmarked. Mark objects reachable due to host |
| // application specific logic or through Harmony weak maps. |
| ProcessEphemeralMarking(&root_visitor, false); |
| |
| // The objects reachable from the roots, weak maps or object groups |
| // are marked. Objects pointed to only by weak global handles cannot be |
| // immediately reclaimed. Instead, we have to mark them as pending and mark |
| // objects reachable from them. |
| // |
| // First we identify nonlive weak handles and mark them as pending |
| // destruction. |
| heap()->isolate()->global_handles()->IdentifyWeakHandles( |
| &IsUnmarkedHeapObject); |
| // Then we mark the objects. |
| heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor); |
| ProcessMarkingDeque(); |
| |
| // Repeat Harmony weak maps marking to mark unmarked objects reachable from |
| // the weak roots we just marked as pending destruction. |
| // |
| // We only process harmony collections, as all object groups have been fully |
| // processed and no weakly reachable node can discover new objects groups. |
| ProcessEphemeralMarking(&root_visitor, true); |
| } |
| |
| if (FLAG_print_cumulative_gc_stat) { |
| heap_->tracer()->AddMarkingTime(heap_->MonotonicallyIncreasingTimeInMs() - |
| start_time); |
| } |
| if (FLAG_track_gc_object_stats) { |
| if (FLAG_trace_gc_object_stats) { |
| heap()->object_stats_->TraceObjectStats(); |
| } |
| heap()->object_stats_->CheckpointObjectStats(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearNonLiveReferences() { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_CLEAR); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_STRING_TABLE); |
| |
| // Prune the string table removing all strings only pointed to by the |
| // string table. Cannot use string_table() here because the string |
| // table is marked. |
| StringTable* string_table = heap()->string_table(); |
| InternalizedStringTableCleaner internalized_visitor(heap()); |
| string_table->IterateElements(&internalized_visitor); |
| string_table->ElementsRemoved(internalized_visitor.PointersRemoved()); |
| |
| ExternalStringTableCleaner external_visitor(heap()); |
| heap()->external_string_table_.Iterate(&external_visitor); |
| heap()->external_string_table_.CleanUp(); |
| } |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_WEAK_LISTS); |
| // Process the weak references. |
| MarkCompactWeakObjectRetainer mark_compact_object_retainer; |
| heap()->ProcessAllWeakReferences(&mark_compact_object_retainer); |
| } |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_GLOBAL_HANDLES); |
| |
| // Remove object groups after marking phase. |
| heap()->isolate()->global_handles()->RemoveObjectGroups(); |
| heap()->isolate()->global_handles()->RemoveImplicitRefGroups(); |
| } |
| |
| // Flush code from collected candidates. |
| if (is_code_flushing_enabled()) { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_CODE_FLUSH); |
| code_flusher_->ProcessCandidates(); |
| } |
| |
| |
| DependentCode* dependent_code_list; |
| Object* non_live_map_list; |
| ClearWeakCells(&non_live_map_list, &dependent_code_list); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_CLEAR_MAPS); |
| ClearSimpleMapTransitions(non_live_map_list); |
| ClearFullMapTransitions(); |
| } |
| |
| MarkDependentCodeForDeoptimization(dependent_code_list); |
| |
| ClearWeakCollections(); |
| |
| ClearInvalidStoreAndSlotsBufferEntries(); |
| } |
| |
| |
| void MarkCompactCollector::MarkDependentCodeForDeoptimization( |
| DependentCode* list_head) { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_DEPENDENT_CODE); |
| Isolate* isolate = this->isolate(); |
| DependentCode* current = list_head; |
| while (current->length() > 0) { |
| have_code_to_deoptimize_ |= current->MarkCodeForDeoptimization( |
| isolate, DependentCode::kWeakCodeGroup); |
| current = current->next_link(); |
| } |
| |
| WeakHashTable* table = heap_->weak_object_to_code_table(); |
| uint32_t capacity = table->Capacity(); |
| for (uint32_t i = 0; i < capacity; i++) { |
| uint32_t key_index = table->EntryToIndex(i); |
| Object* key = table->get(key_index); |
| if (!table->IsKey(key)) continue; |
| uint32_t value_index = table->EntryToValueIndex(i); |
| Object* value = table->get(value_index); |
| DCHECK(key->IsWeakCell()); |
| if (WeakCell::cast(key)->cleared()) { |
| have_code_to_deoptimize_ |= |
| DependentCode::cast(value)->MarkCodeForDeoptimization( |
| isolate, DependentCode::kWeakCodeGroup); |
| table->set(key_index, heap_->the_hole_value()); |
| table->set(value_index, heap_->the_hole_value()); |
| table->ElementRemoved(); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearSimpleMapTransitions( |
| Object* non_live_map_list) { |
| Object* the_hole_value = heap()->the_hole_value(); |
| Object* weak_cell_obj = non_live_map_list; |
| while (weak_cell_obj != Smi::FromInt(0)) { |
| WeakCell* weak_cell = WeakCell::cast(weak_cell_obj); |
| Map* map = Map::cast(weak_cell->value()); |
| DCHECK(Marking::IsWhite(Marking::MarkBitFrom(map))); |
| Object* potential_parent = map->constructor_or_backpointer(); |
| if (potential_parent->IsMap()) { |
| Map* parent = Map::cast(potential_parent); |
| if (Marking::IsBlackOrGrey(Marking::MarkBitFrom(parent)) && |
| parent->raw_transitions() == weak_cell) { |
| ClearSimpleMapTransition(parent, map); |
| } |
| } |
| weak_cell->clear(); |
| weak_cell_obj = weak_cell->next(); |
| weak_cell->clear_next(the_hole_value); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearSimpleMapTransition(Map* map, |
| Map* dead_transition) { |
| // A previously existing simple transition (stored in a WeakCell) is going |
| // to be cleared. Clear the useless cell pointer, and take ownership |
| // of the descriptor array. |
| map->set_raw_transitions(Smi::FromInt(0)); |
| int number_of_own_descriptors = map->NumberOfOwnDescriptors(); |
| DescriptorArray* descriptors = map->instance_descriptors(); |
| if (descriptors == dead_transition->instance_descriptors() && |
| number_of_own_descriptors > 0) { |
| TrimDescriptorArray(map, descriptors); |
| DCHECK(descriptors->number_of_descriptors() == number_of_own_descriptors); |
| map->set_owns_descriptors(true); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearFullMapTransitions() { |
| HeapObject* undefined = heap()->undefined_value(); |
| Object* obj = heap()->encountered_transition_arrays(); |
| while (obj != Smi::FromInt(0)) { |
| TransitionArray* array = TransitionArray::cast(obj); |
| int num_transitions = array->number_of_entries(); |
| DCHECK_EQ(TransitionArray::NumberOfTransitions(array), num_transitions); |
| if (num_transitions > 0) { |
| Map* map = array->GetTarget(0); |
| Map* parent = Map::cast(map->constructor_or_backpointer()); |
| bool parent_is_alive = |
| Marking::IsBlackOrGrey(Marking::MarkBitFrom(parent)); |
| DescriptorArray* descriptors = |
| parent_is_alive ? parent->instance_descriptors() : nullptr; |
| bool descriptors_owner_died = |
| CompactTransitionArray(parent, array, descriptors); |
| if (descriptors_owner_died) { |
| TrimDescriptorArray(parent, descriptors); |
| } |
| } |
| obj = array->next_link(); |
| array->set_next_link(undefined, SKIP_WRITE_BARRIER); |
| } |
| heap()->set_encountered_transition_arrays(Smi::FromInt(0)); |
| } |
| |
| |
| bool MarkCompactCollector::CompactTransitionArray( |
| Map* map, TransitionArray* transitions, DescriptorArray* descriptors) { |
| int num_transitions = transitions->number_of_entries(); |
| bool descriptors_owner_died = false; |
| int transition_index = 0; |
| // Compact all live transitions to the left. |
| for (int i = 0; i < num_transitions; ++i) { |
| Map* target = transitions->GetTarget(i); |
| DCHECK_EQ(target->constructor_or_backpointer(), map); |
| if (Marking::IsWhite(Marking::MarkBitFrom(target))) { |
| if (descriptors != nullptr && |
| target->instance_descriptors() == descriptors) { |
| descriptors_owner_died = true; |
| } |
| } else { |
| if (i != transition_index) { |
| Name* key = transitions->GetKey(i); |
| transitions->SetKey(transition_index, key); |
| Object** key_slot = transitions->GetKeySlot(transition_index); |
| RecordSlot(transitions, key_slot, key); |
| // Target slots do not need to be recorded since maps are not compacted. |
| transitions->SetTarget(transition_index, transitions->GetTarget(i)); |
| } |
| transition_index++; |
| } |
| } |
| // If there are no transitions to be cleared, return. |
| if (transition_index == num_transitions) { |
| DCHECK(!descriptors_owner_died); |
| return false; |
| } |
| // Note that we never eliminate a transition array, though we might right-trim |
| // such that number_of_transitions() == 0. If this assumption changes, |
| // TransitionArray::Insert() will need to deal with the case that a transition |
| // array disappeared during GC. |
| int trim = TransitionArray::Capacity(transitions) - transition_index; |
| if (trim > 0) { |
| heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>( |
| transitions, trim * TransitionArray::kTransitionSize); |
| transitions->SetNumberOfTransitions(transition_index); |
| } |
| return descriptors_owner_died; |
| } |
| |
| |
| void MarkCompactCollector::TrimDescriptorArray(Map* map, |
| DescriptorArray* descriptors) { |
| int number_of_own_descriptors = map->NumberOfOwnDescriptors(); |
| if (number_of_own_descriptors == 0) { |
| DCHECK(descriptors == heap_->empty_descriptor_array()); |
| return; |
| } |
| |
| int number_of_descriptors = descriptors->number_of_descriptors_storage(); |
| int to_trim = number_of_descriptors - number_of_own_descriptors; |
| if (to_trim > 0) { |
| heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>( |
| descriptors, to_trim * DescriptorArray::kDescriptorSize); |
| descriptors->SetNumberOfDescriptors(number_of_own_descriptors); |
| |
| if (descriptors->HasEnumCache()) TrimEnumCache(map, descriptors); |
| descriptors->Sort(); |
| |
| if (FLAG_unbox_double_fields) { |
| LayoutDescriptor* layout_descriptor = map->layout_descriptor(); |
| layout_descriptor = layout_descriptor->Trim(heap_, map, descriptors, |
| number_of_own_descriptors); |
| SLOW_DCHECK(layout_descriptor->IsConsistentWithMap(map, true)); |
| } |
| } |
| DCHECK(descriptors->number_of_descriptors() == number_of_own_descriptors); |
| map->set_owns_descriptors(true); |
| } |
| |
| |
| void MarkCompactCollector::TrimEnumCache(Map* map, |
| DescriptorArray* descriptors) { |
| int live_enum = map->EnumLength(); |
| if (live_enum == kInvalidEnumCacheSentinel) { |
| live_enum = |
| map->NumberOfDescribedProperties(OWN_DESCRIPTORS, ENUMERABLE_STRINGS); |
| } |
| if (live_enum == 0) return descriptors->ClearEnumCache(); |
| |
| FixedArray* enum_cache = descriptors->GetEnumCache(); |
| |
| int to_trim = enum_cache->length() - live_enum; |
| if (to_trim <= 0) return; |
| heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>( |
| descriptors->GetEnumCache(), to_trim); |
| |
| if (!descriptors->HasEnumIndicesCache()) return; |
| FixedArray* enum_indices_cache = descriptors->GetEnumIndicesCache(); |
| heap_->RightTrimFixedArray<Heap::SEQUENTIAL_TO_SWEEPER>(enum_indices_cache, |
| to_trim); |
| } |
| |
| |
| void MarkCompactCollector::ProcessWeakCollections() { |
| Object* weak_collection_obj = heap()->encountered_weak_collections(); |
| while (weak_collection_obj != Smi::FromInt(0)) { |
| JSWeakCollection* weak_collection = |
| reinterpret_cast<JSWeakCollection*>(weak_collection_obj); |
| DCHECK(MarkCompactCollector::IsMarked(weak_collection)); |
| if (weak_collection->table()->IsHashTable()) { |
| ObjectHashTable* table = ObjectHashTable::cast(weak_collection->table()); |
| for (int i = 0; i < table->Capacity(); i++) { |
| if (MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) { |
| Object** key_slot = |
| table->RawFieldOfElementAt(ObjectHashTable::EntryToIndex(i)); |
| RecordSlot(table, key_slot, *key_slot); |
| Object** value_slot = |
| table->RawFieldOfElementAt(ObjectHashTable::EntryToValueIndex(i)); |
| MarkCompactMarkingVisitor::MarkObjectByPointer(this, table, |
| value_slot); |
| } |
| } |
| } |
| weak_collection_obj = weak_collection->next(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearWeakCollections() { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_CLEAR_WEAK_COLLECTIONS); |
| Object* weak_collection_obj = heap()->encountered_weak_collections(); |
| while (weak_collection_obj != Smi::FromInt(0)) { |
| JSWeakCollection* weak_collection = |
| reinterpret_cast<JSWeakCollection*>(weak_collection_obj); |
| DCHECK(MarkCompactCollector::IsMarked(weak_collection)); |
| if (weak_collection->table()->IsHashTable()) { |
| ObjectHashTable* table = ObjectHashTable::cast(weak_collection->table()); |
| for (int i = 0; i < table->Capacity(); i++) { |
| HeapObject* key = HeapObject::cast(table->KeyAt(i)); |
| if (!MarkCompactCollector::IsMarked(key)) { |
| table->RemoveEntry(i); |
| } |
| } |
| } |
| weak_collection_obj = weak_collection->next(); |
| weak_collection->set_next(heap()->undefined_value()); |
| } |
| heap()->set_encountered_weak_collections(Smi::FromInt(0)); |
| } |
| |
| |
| void MarkCompactCollector::AbortWeakCollections() { |
| Object* weak_collection_obj = heap()->encountered_weak_collections(); |
| while (weak_collection_obj != Smi::FromInt(0)) { |
| JSWeakCollection* weak_collection = |
| reinterpret_cast<JSWeakCollection*>(weak_collection_obj); |
| weak_collection_obj = weak_collection->next(); |
| weak_collection->set_next(heap()->undefined_value()); |
| } |
| heap()->set_encountered_weak_collections(Smi::FromInt(0)); |
| } |
| |
| |
| void MarkCompactCollector::ClearWeakCells(Object** non_live_map_list, |
| DependentCode** dependent_code_list) { |
| Heap* heap = this->heap(); |
| GCTracer::Scope gc_scope(heap->tracer(), |
| GCTracer::Scope::MC_CLEAR_WEAK_CELLS); |
| Object* weak_cell_obj = heap->encountered_weak_cells(); |
| Object* the_hole_value = heap->the_hole_value(); |
| DependentCode* dependent_code_head = |
| DependentCode::cast(heap->empty_fixed_array()); |
| Object* non_live_map_head = Smi::FromInt(0); |
| while (weak_cell_obj != Smi::FromInt(0)) { |
| WeakCell* weak_cell = reinterpret_cast<WeakCell*>(weak_cell_obj); |
| Object* next_weak_cell = weak_cell->next(); |
| bool clear_value = true; |
| bool clear_next = true; |
| // We do not insert cleared weak cells into the list, so the value |
| // cannot be a Smi here. |
| HeapObject* value = HeapObject::cast(weak_cell->value()); |
| if (!MarkCompactCollector::IsMarked(value)) { |
| // Cells for new-space objects embedded in optimized code are wrapped in |
| // WeakCell and put into Heap::weak_object_to_code_table. |
| // Such cells do not have any strong references but we want to keep them |
| // alive as long as the cell value is alive. |
| // TODO(ulan): remove this once we remove Heap::weak_object_to_code_table. |
| if (value->IsCell()) { |
| Object* cell_value = Cell::cast(value)->value(); |
| if (cell_value->IsHeapObject() && |
| MarkCompactCollector::IsMarked(HeapObject::cast(cell_value))) { |
| // Resurrect the cell. |
| MarkBit mark = Marking::MarkBitFrom(value); |
| SetMark(value, mark); |
| Object** slot = HeapObject::RawField(value, Cell::kValueOffset); |
| RecordSlot(value, slot, *slot); |
| slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset); |
| RecordSlot(weak_cell, slot, *slot); |
| clear_value = false; |
| } |
| } |
| if (value->IsMap()) { |
| // The map is non-live. |
| Map* map = Map::cast(value); |
| // Add dependent code to the dependent_code_list. |
| DependentCode* candidate = map->dependent_code(); |
| // We rely on the fact that the weak code group comes first. |
| STATIC_ASSERT(DependentCode::kWeakCodeGroup == 0); |
| if (candidate->length() > 0 && |
| candidate->group() == DependentCode::kWeakCodeGroup) { |
| candidate->set_next_link(dependent_code_head); |
| dependent_code_head = candidate; |
| } |
| // Add the weak cell to the non_live_map list. |
| weak_cell->set_next(non_live_map_head); |
| non_live_map_head = weak_cell; |
| clear_value = false; |
| clear_next = false; |
| } |
| } else { |
| // The value of the weak cell is alive. |
| Object** slot = HeapObject::RawField(weak_cell, WeakCell::kValueOffset); |
| RecordSlot(weak_cell, slot, *slot); |
| clear_value = false; |
| } |
| if (clear_value) { |
| weak_cell->clear(); |
| } |
| if (clear_next) { |
| weak_cell->clear_next(the_hole_value); |
| } |
| weak_cell_obj = next_weak_cell; |
| } |
| heap->set_encountered_weak_cells(Smi::FromInt(0)); |
| *non_live_map_list = non_live_map_head; |
| *dependent_code_list = dependent_code_head; |
| } |
| |
| |
| void MarkCompactCollector::AbortWeakCells() { |
| Object* the_hole_value = heap()->the_hole_value(); |
| Object* weak_cell_obj = heap()->encountered_weak_cells(); |
| while (weak_cell_obj != Smi::FromInt(0)) { |
| WeakCell* weak_cell = reinterpret_cast<WeakCell*>(weak_cell_obj); |
| weak_cell_obj = weak_cell->next(); |
| weak_cell->clear_next(the_hole_value); |
| } |
| heap()->set_encountered_weak_cells(Smi::FromInt(0)); |
| } |
| |
| |
| void MarkCompactCollector::AbortTransitionArrays() { |
| HeapObject* undefined = heap()->undefined_value(); |
| Object* obj = heap()->encountered_transition_arrays(); |
| while (obj != Smi::FromInt(0)) { |
| TransitionArray* array = TransitionArray::cast(obj); |
| obj = array->next_link(); |
| array->set_next_link(undefined, SKIP_WRITE_BARRIER); |
| } |
| heap()->set_encountered_transition_arrays(Smi::FromInt(0)); |
| } |
| |
| void MarkCompactCollector::RecordMigratedSlot( |
| Object* value, Address slot, SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer) { |
| // When parallel compaction is in progress, store and slots buffer entries |
| // require synchronization. |
| if (heap_->InNewSpace(value)) { |
| if (compaction_in_progress_) { |
| local_store_buffer->Record(slot); |
| } else { |
| Page* page = Page::FromAddress(slot); |
| RememberedSet<OLD_TO_NEW>::Insert(page, slot); |
| } |
| } else if (value->IsHeapObject() && IsOnEvacuationCandidate(value)) { |
| SlotsBuffer::AddTo(slots_buffer_allocator_, evacuation_slots_buffer, |
| reinterpret_cast<Object**>(slot), |
| SlotsBuffer::IGNORE_OVERFLOW); |
| } |
| } |
| |
| |
| void MarkCompactCollector::RecordMigratedCodeEntrySlot( |
| Address code_entry, Address code_entry_slot, |
| SlotsBuffer** evacuation_slots_buffer) { |
| if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) { |
| SlotsBuffer::AddTo(slots_buffer_allocator_, evacuation_slots_buffer, |
| SlotsBuffer::CODE_ENTRY_SLOT, code_entry_slot, |
| SlotsBuffer::IGNORE_OVERFLOW); |
| } |
| } |
| |
| |
| void MarkCompactCollector::RecordMigratedCodeObjectSlot( |
| Address code_object, SlotsBuffer** evacuation_slots_buffer) { |
| SlotsBuffer::AddTo(slots_buffer_allocator_, evacuation_slots_buffer, |
| SlotsBuffer::RELOCATED_CODE_OBJECT, code_object, |
| SlotsBuffer::IGNORE_OVERFLOW); |
| } |
| |
| |
| static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) { |
| if (RelocInfo::IsCodeTarget(rmode)) { |
| return SlotsBuffer::CODE_TARGET_SLOT; |
| } else if (RelocInfo::IsCell(rmode)) { |
| return SlotsBuffer::CELL_TARGET_SLOT; |
| } else if (RelocInfo::IsEmbeddedObject(rmode)) { |
| return SlotsBuffer::EMBEDDED_OBJECT_SLOT; |
| } else if (RelocInfo::IsDebugBreakSlot(rmode)) { |
| return SlotsBuffer::DEBUG_TARGET_SLOT; |
| } |
| UNREACHABLE(); |
| return SlotsBuffer::NUMBER_OF_SLOT_TYPES; |
| } |
| |
| |
| static inline SlotsBuffer::SlotType DecodeSlotType( |
| SlotsBuffer::ObjectSlot slot) { |
| return static_cast<SlotsBuffer::SlotType>(reinterpret_cast<intptr_t>(slot)); |
| } |
| |
| |
| void MarkCompactCollector::RecordRelocSlot(RelocInfo* rinfo, Object* target) { |
| Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target)); |
| RelocInfo::Mode rmode = rinfo->rmode(); |
| if (target_page->IsEvacuationCandidate() && |
| (rinfo->host() == NULL || |
| !ShouldSkipEvacuationSlotRecording(rinfo->host()))) { |
| Address addr = rinfo->pc(); |
| SlotsBuffer::SlotType slot_type = SlotTypeForRMode(rmode); |
| if (rinfo->IsInConstantPool()) { |
| addr = rinfo->constant_pool_entry_address(); |
| if (RelocInfo::IsCodeTarget(rmode)) { |
| slot_type = SlotsBuffer::CODE_ENTRY_SLOT; |
| } else { |
| DCHECK(RelocInfo::IsEmbeddedObject(rmode)); |
| slot_type = SlotsBuffer::OBJECT_SLOT; |
| } |
| } |
| bool success = SlotsBuffer::AddTo( |
| slots_buffer_allocator_, target_page->slots_buffer_address(), slot_type, |
| addr, SlotsBuffer::FAIL_ON_OVERFLOW); |
| if (!success) { |
| EvictPopularEvacuationCandidate(target_page); |
| } |
| } |
| } |
| |
| |
| class RecordMigratedSlotVisitor final : public ObjectVisitor { |
| public: |
| RecordMigratedSlotVisitor(MarkCompactCollector* collector, |
| SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer) |
| : collector_(collector), |
| evacuation_slots_buffer_(evacuation_slots_buffer), |
| local_store_buffer_(local_store_buffer) {} |
| |
| V8_INLINE void VisitPointer(Object** p) override { |
| collector_->RecordMigratedSlot(*p, reinterpret_cast<Address>(p), |
| evacuation_slots_buffer_, |
| local_store_buffer_); |
| } |
| |
| V8_INLINE void VisitPointers(Object** start, Object** end) override { |
| while (start < end) { |
| collector_->RecordMigratedSlot(*start, reinterpret_cast<Address>(start), |
| evacuation_slots_buffer_, |
| local_store_buffer_); |
| ++start; |
| } |
| } |
| |
| V8_INLINE void VisitCodeEntry(Address code_entry_slot) override { |
| if (collector_->compacting_) { |
| Address code_entry = Memory::Address_at(code_entry_slot); |
| collector_->RecordMigratedCodeEntrySlot(code_entry, code_entry_slot, |
| evacuation_slots_buffer_); |
| } |
| } |
| |
| private: |
| MarkCompactCollector* collector_; |
| SlotsBuffer** evacuation_slots_buffer_; |
| LocalStoreBuffer* local_store_buffer_; |
| }; |
| |
| |
| // We scavenge new space simultaneously with sweeping. This is done in two |
| // passes. |
| // |
| // The first pass migrates all alive objects from one semispace to another or |
| // promotes them to old space. Forwarding address is written directly into |
| // first word of object without any encoding. If object is dead we write |
| // NULL as a forwarding address. |
| // |
| // The second pass updates pointers to new space in all spaces. It is possible |
| // to encounter pointers to dead new space objects during traversal of pointers |
| // to new space. We should clear them to avoid encountering them during next |
| // pointer iteration. This is an issue if the store buffer overflows and we |
| // have to scan the entire old space, including dead objects, looking for |
| // pointers to new space. |
| void MarkCompactCollector::MigrateObject(HeapObject* dst, HeapObject* src, |
| int size, AllocationSpace dest, |
| SlotsBuffer** evacuation_slots_buffer, |
| LocalStoreBuffer* local_store_buffer) { |
| Address dst_addr = dst->address(); |
| Address src_addr = src->address(); |
| DCHECK(heap()->AllowedToBeMigrated(src, dest)); |
| DCHECK(dest != LO_SPACE); |
| if (dest == OLD_SPACE) { |
| DCHECK_OBJECT_SIZE(size); |
| DCHECK(evacuation_slots_buffer != nullptr); |
| DCHECK(IsAligned(size, kPointerSize)); |
| |
| heap()->MoveBlock(dst->address(), src->address(), size); |
| RecordMigratedSlotVisitor visitor(this, evacuation_slots_buffer, |
| local_store_buffer); |
| dst->IterateBody(&visitor); |
| } else if (dest == CODE_SPACE) { |
| DCHECK_CODEOBJECT_SIZE(size, heap()->code_space()); |
| DCHECK(evacuation_slots_buffer != nullptr); |
| PROFILE(isolate(), CodeMoveEvent(src_addr, dst_addr)); |
| heap()->MoveBlock(dst_addr, src_addr, size); |
| RecordMigratedCodeObjectSlot(dst_addr, evacuation_slots_buffer); |
| Code::cast(dst)->Relocate(dst_addr - src_addr); |
| } else { |
| DCHECK_OBJECT_SIZE(size); |
| DCHECK(evacuation_slots_buffer == nullptr); |
| DCHECK(dest == NEW_SPACE); |
| heap()->MoveBlock(dst_addr, src_addr, size); |
| } |
| heap()->OnMoveEvent(dst, src, size); |
| Memory::Address_at(src_addr) = dst_addr; |
| } |
| |
| |
| static inline void UpdateSlot(Isolate* isolate, ObjectVisitor* v, |
| SlotsBuffer::SlotType slot_type, Address addr) { |
| switch (slot_type) { |
| case SlotsBuffer::CODE_TARGET_SLOT: { |
| RelocInfo rinfo(isolate, addr, RelocInfo::CODE_TARGET, 0, NULL); |
| rinfo.Visit(isolate, v); |
| break; |
| } |
| case SlotsBuffer::CELL_TARGET_SLOT: { |
| RelocInfo rinfo(isolate, addr, RelocInfo::CELL, 0, NULL); |
| rinfo.Visit(isolate, v); |
| break; |
| } |
| case SlotsBuffer::CODE_ENTRY_SLOT: { |
| v->VisitCodeEntry(addr); |
| break; |
| } |
| case SlotsBuffer::RELOCATED_CODE_OBJECT: { |
| HeapObject* obj = HeapObject::FromAddress(addr); |
| Code::BodyDescriptor::IterateBody(obj, v); |
| break; |
| } |
| case SlotsBuffer::DEBUG_TARGET_SLOT: { |
| RelocInfo rinfo(isolate, addr, RelocInfo::DEBUG_BREAK_SLOT_AT_POSITION, 0, |
| NULL); |
| if (rinfo.IsPatchedDebugBreakSlotSequence()) rinfo.Visit(isolate, v); |
| break; |
| } |
| case SlotsBuffer::EMBEDDED_OBJECT_SLOT: { |
| RelocInfo rinfo(isolate, addr, RelocInfo::EMBEDDED_OBJECT, 0, NULL); |
| rinfo.Visit(isolate, v); |
| break; |
| } |
| case SlotsBuffer::OBJECT_SLOT: { |
| v->VisitPointer(reinterpret_cast<Object**>(addr)); |
| break; |
| } |
| default: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| |
| |
| // Visitor for updating pointers from live objects in old spaces to new space. |
| // It does not expect to encounter pointers to dead objects. |
| class PointersUpdatingVisitor : public ObjectVisitor { |
| public: |
| explicit PointersUpdatingVisitor(Heap* heap) : heap_(heap) {} |
| |
| void VisitPointer(Object** p) override { UpdatePointer(p); } |
| |
| void VisitPointers(Object** start, Object** end) override { |
| for (Object** p = start; p < end; p++) UpdatePointer(p); |
| } |
| |
| void VisitCell(RelocInfo* rinfo) override { |
| DCHECK(rinfo->rmode() == RelocInfo::CELL); |
| Object* cell = rinfo->target_cell(); |
| Object* old_cell = cell; |
| VisitPointer(&cell); |
| if (cell != old_cell) { |
| rinfo->set_target_cell(reinterpret_cast<Cell*>(cell)); |
| } |
| } |
| |
| void VisitEmbeddedPointer(RelocInfo* rinfo) override { |
| DCHECK(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT); |
| Object* target = rinfo->target_object(); |
| Object* old_target = target; |
| VisitPointer(&target); |
| // Avoid unnecessary changes that might unnecessary flush the instruction |
| // cache. |
| if (target != old_target) { |
| rinfo->set_target_object(target); |
| } |
| } |
| |
| void VisitCodeTarget(RelocInfo* rinfo) override { |
| DCHECK(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| Object* old_target = target; |
| VisitPointer(&target); |
| if (target != old_target) { |
| rinfo->set_target_address(Code::cast(target)->instruction_start()); |
| } |
| } |
| |
| void VisitCodeAgeSequence(RelocInfo* rinfo) override { |
| DCHECK(RelocInfo::IsCodeAgeSequence(rinfo->rmode())); |
| Object* stub = rinfo->code_age_stub(); |
| DCHECK(stub != NULL); |
| VisitPointer(&stub); |
| if (stub != rinfo->code_age_stub()) { |
| rinfo->set_code_age_stub(Code::cast(stub)); |
| } |
| } |
| |
| void VisitDebugTarget(RelocInfo* rinfo) override { |
| DCHECK(RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence()); |
| Object* target = |
| Code::GetCodeFromTargetAddress(rinfo->debug_call_address()); |
| VisitPointer(&target); |
| rinfo->set_debug_call_address(Code::cast(target)->instruction_start()); |
| } |
| |
| static inline void UpdateSlot(Heap* heap, Object** slot) { |
| Object* obj = reinterpret_cast<Object*>( |
| base::NoBarrier_Load(reinterpret_cast<base::AtomicWord*>(slot))); |
| |
| if (!obj->IsHeapObject()) return; |
| |
| HeapObject* heap_obj = HeapObject::cast(obj); |
| |
| MapWord map_word = heap_obj->map_word(); |
| if (map_word.IsForwardingAddress()) { |
| DCHECK(heap->InFromSpace(heap_obj) || |
| MarkCompactCollector::IsOnEvacuationCandidate(heap_obj) || |
| Page::FromAddress(heap_obj->address()) |
| ->IsFlagSet(Page::COMPACTION_WAS_ABORTED)); |
| HeapObject* target = map_word.ToForwardingAddress(); |
| base::NoBarrier_CompareAndSwap( |
| reinterpret_cast<base::AtomicWord*>(slot), |
| reinterpret_cast<base::AtomicWord>(obj), |
| reinterpret_cast<base::AtomicWord>(target)); |
| DCHECK(!heap->InFromSpace(target) && |
| !MarkCompactCollector::IsOnEvacuationCandidate(target)); |
| } |
| } |
| |
| private: |
| inline void UpdatePointer(Object** p) { UpdateSlot(heap_, p); } |
| |
| Heap* heap_; |
| }; |
| |
| |
| void MarkCompactCollector::UpdateSlots(SlotsBuffer* buffer) { |
| PointersUpdatingVisitor v(heap_); |
| size_t buffer_size = buffer->Size(); |
| |
| for (size_t slot_idx = 0; slot_idx < buffer_size; ++slot_idx) { |
| SlotsBuffer::ObjectSlot slot = buffer->Get(slot_idx); |
| if (!SlotsBuffer::IsTypedSlot(slot)) { |
| PointersUpdatingVisitor::UpdateSlot(heap_, slot); |
| } else { |
| ++slot_idx; |
| DCHECK(slot_idx < buffer_size); |
| UpdateSlot(heap_->isolate(), &v, DecodeSlotType(slot), |
| reinterpret_cast<Address>(buffer->Get(slot_idx))); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::UpdateSlotsRecordedIn(SlotsBuffer* buffer) { |
| while (buffer != NULL) { |
| UpdateSlots(buffer); |
| buffer = buffer->next(); |
| } |
| } |
| |
| |
| static void UpdatePointer(HeapObject** address, HeapObject* object) { |
| MapWord map_word = object->map_word(); |
| // Since we only filter invalid slots in old space, the store buffer can |
| // still contain stale pointers in large object and in map spaces. Ignore |
| // these pointers here. |
| DCHECK(map_word.IsForwardingAddress() || |
| !object->GetHeap()->old_space()->Contains( |
| reinterpret_cast<Address>(address))); |
| if (map_word.IsForwardingAddress()) { |
| // Update the corresponding slot. |
| *address = map_word.ToForwardingAddress(); |
| } |
| } |
| |
| |
| static String* UpdateReferenceInExternalStringTableEntry(Heap* heap, |
| Object** p) { |
| MapWord map_word = HeapObject::cast(*p)->map_word(); |
| |
| if (map_word.IsForwardingAddress()) { |
| return String::cast(map_word.ToForwardingAddress()); |
| } |
| |
| return String::cast(*p); |
| } |
| |
| |
| bool MarkCompactCollector::IsSlotInBlackObject(Page* p, Address slot, |
| HeapObject** out_object) { |
| Space* owner = p->owner(); |
| if (owner == heap_->lo_space() || owner == NULL) { |
| Object* large_object = heap_->lo_space()->FindObject(slot); |
| // This object has to exist, otherwise we would not have recorded a slot |
| // for it. |
| CHECK(large_object->IsHeapObject()); |
| HeapObject* large_heap_object = HeapObject::cast(large_object); |
| if (IsMarked(large_heap_object)) { |
| *out_object = large_heap_object; |
| return true; |
| } |
| return false; |
| } |
| |
| uint32_t mark_bit_index = p->AddressToMarkbitIndex(slot); |
| unsigned int cell_index = mark_bit_index >> Bitmap::kBitsPerCellLog2; |
| MarkBit::CellType index_mask = 1u << Bitmap::IndexInCell(mark_bit_index); |
| MarkBit::CellType* cells = p->markbits()->cells(); |
| Address base_address = p->area_start(); |
| unsigned int base_address_cell_index = Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex(p->AddressToMarkbitIndex(base_address))); |
| |
| // Check if the slot points to the start of an object. This can happen e.g. |
| // when we left trim a fixed array. Such slots are invalid and we can remove |
| // them. |
| if (index_mask > 1) { |
| if ((cells[cell_index] & index_mask) != 0 && |
| (cells[cell_index] & (index_mask >> 1)) == 0) { |
| return false; |
| } |
| } else { |
| // Left trimming moves the mark bits so we cannot be in the very first cell. |
| DCHECK(cell_index != base_address_cell_index); |
| if ((cells[cell_index] & index_mask) != 0 && |
| (cells[cell_index - 1] & (1u << Bitmap::kBitIndexMask)) == 0) { |
| return false; |
| } |
| } |
| |
| // Check if the object is in the current cell. |
| MarkBit::CellType slot_mask; |
| if ((cells[cell_index] == 0) || |
| (base::bits::CountTrailingZeros32(cells[cell_index]) > |
| base::bits::CountTrailingZeros32(cells[cell_index] | index_mask))) { |
| // If we are already in the first cell, there is no live object. |
| if (cell_index == base_address_cell_index) return false; |
| |
| // If not, find a cell in a preceding cell slot that has a mark bit set. |
| do { |
| cell_index--; |
| } while (cell_index > base_address_cell_index && cells[cell_index] == 0); |
| |
| // The slot must be in a dead object if there are no preceding cells that |
| // have mark bits set. |
| if (cells[cell_index] == 0) { |
| return false; |
| } |
| |
| // The object is in a preceding cell. Set the mask to find any object. |
| slot_mask = ~0u; |
| } else { |
| // We are interested in object mark bits right before the slot. |
| slot_mask = index_mask + (index_mask - 1); |
| } |
| |
| MarkBit::CellType current_cell = cells[cell_index]; |
| CHECK(current_cell != 0); |
| |
| // Find the last live object in the cell. |
| unsigned int leading_zeros = |
| base::bits::CountLeadingZeros32(current_cell & slot_mask); |
| CHECK(leading_zeros != Bitmap::kBitsPerCell); |
| int offset = static_cast<int>(Bitmap::kBitIndexMask - leading_zeros) - 1; |
| |
| base_address += (cell_index - base_address_cell_index) * |
| Bitmap::kBitsPerCell * kPointerSize; |
| Address address = base_address + offset * kPointerSize; |
| HeapObject* object = HeapObject::FromAddress(address); |
| CHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| CHECK(object->address() < reinterpret_cast<Address>(slot)); |
| if ((object->address() + kPointerSize) <= slot && |
| (object->address() + object->Size()) > slot) { |
| // If the slot is within the last found object in the cell, the slot is |
| // in a live object. |
| // Slots pointing to the first word of an object are invalid and removed. |
| // This can happen when we move the object header while left trimming. |
| *out_object = object; |
| return true; |
| } |
| return false; |
| } |
| |
| |
| bool MarkCompactCollector::IsSlotInBlackObjectSlow(Page* p, Address slot) { |
| // This function does not support large objects right now. |
| Space* owner = p->owner(); |
| if (owner == heap_->lo_space() || owner == NULL) { |
| Object* large_object = heap_->lo_space()->FindObject(slot); |
| // This object has to exist, otherwise we would not have recorded a slot |
| // for it. |
| CHECK(large_object->IsHeapObject()); |
| HeapObject* large_heap_object = HeapObject::cast(large_object); |
| if (IsMarked(large_heap_object)) { |
| return true; |
| } |
| return false; |
| } |
| |
| LiveObjectIterator<kBlackObjects> it(p); |
| HeapObject* object = NULL; |
| while ((object = it.Next()) != NULL) { |
| int size = object->Size(); |
| |
| if (object->address() > slot) return false; |
| if (object->address() <= slot && slot < (object->address() + size)) { |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| |
| bool MarkCompactCollector::IsSlotInLiveObject(Address slot) { |
| HeapObject* object = NULL; |
| // The target object is black but we don't know if the source slot is black. |
| // The source object could have died and the slot could be part of a free |
| // space. Find out based on mark bits if the slot is part of a live object. |
| if (!IsSlotInBlackObject(Page::FromAddress(slot), slot, &object)) { |
| return false; |
| } |
| |
| DCHECK(object != NULL); |
| int offset = static_cast<int>(slot - object->address()); |
| return object->IsValidSlot(offset); |
| } |
| |
| |
| void MarkCompactCollector::VerifyIsSlotInLiveObject(Address slot, |
| HeapObject* object) { |
| // The target object has to be black. |
| CHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| |
| // The target object is black but we don't know if the source slot is black. |
| // The source object could have died and the slot could be part of a free |
| // space. Use the mark bit iterator to find out about liveness of the slot. |
| CHECK(IsSlotInBlackObjectSlow(Page::FromAddress(slot), slot)); |
| } |
| |
| |
| void MarkCompactCollector::EvacuateNewSpacePrologue() { |
| NewSpace* new_space = heap()->new_space(); |
| NewSpacePageIterator it(new_space->bottom(), new_space->top()); |
| // Append the list of new space pages to be processed. |
| while (it.has_next()) { |
| newspace_evacuation_candidates_.Add(it.next()); |
| } |
| new_space->Flip(); |
| new_space->ResetAllocationInfo(); |
| } |
| |
| void MarkCompactCollector::EvacuateNewSpaceEpilogue() { |
| newspace_evacuation_candidates_.Rewind(0); |
| } |
| |
| |
| void MarkCompactCollector::AddEvacuationSlotsBufferSynchronized( |
| SlotsBuffer* evacuation_slots_buffer) { |
| base::LockGuard<base::Mutex> lock_guard(&evacuation_slots_buffers_mutex_); |
| evacuation_slots_buffers_.Add(evacuation_slots_buffer); |
| } |
| |
| class MarkCompactCollector::Evacuator : public Malloced { |
| public: |
| Evacuator(MarkCompactCollector* collector, |
| const List<Page*>& evacuation_candidates, |
| const List<NewSpacePage*>& newspace_evacuation_candidates) |
| : collector_(collector), |
| evacuation_candidates_(evacuation_candidates), |
| newspace_evacuation_candidates_(newspace_evacuation_candidates), |
| compaction_spaces_(collector->heap()), |
| local_slots_buffer_(nullptr), |
| local_store_buffer_(collector->heap()), |
| local_pretenuring_feedback_(HashMap::PointersMatch, |
| kInitialLocalPretenuringFeedbackCapacity), |
| new_space_visitor_(collector->heap(), &compaction_spaces_, |
| &local_slots_buffer_, &local_store_buffer_, |
| &local_pretenuring_feedback_), |
| old_space_visitor_(collector->heap(), &compaction_spaces_, |
| &local_slots_buffer_, &local_store_buffer_), |
| duration_(0.0), |
| bytes_compacted_(0), |
| task_id_(0) {} |
| |
| // Evacuate the configured set of pages in parallel. |
| inline void EvacuatePages(); |
| |
| // Merge back locally cached info sequentially. Note that this method needs |
| // to be called from the main thread. |
| inline void Finalize(); |
| |
| CompactionSpaceCollection* compaction_spaces() { return &compaction_spaces_; } |
| |
| uint32_t task_id() { return task_id_; } |
| void set_task_id(uint32_t id) { task_id_ = id; } |
| |
| private: |
| static const int kInitialLocalPretenuringFeedbackCapacity = 256; |
| |
| Heap* heap() { return collector_->heap(); } |
| |
| void ReportCompactionProgress(double duration, intptr_t bytes_compacted) { |
| duration_ += duration; |
| bytes_compacted_ += bytes_compacted; |
| } |
| |
| inline bool EvacuateSinglePage(MemoryChunk* p, HeapObjectVisitor* visitor); |
| |
| MarkCompactCollector* collector_; |
| |
| // Pages to process. |
| const List<Page*>& evacuation_candidates_; |
| const List<NewSpacePage*>& newspace_evacuation_candidates_; |
| |
| // Locally cached collector data. |
| CompactionSpaceCollection compaction_spaces_; |
| SlotsBuffer* local_slots_buffer_; |
| LocalStoreBuffer local_store_buffer_; |
| HashMap local_pretenuring_feedback_; |
| |
| // Vistors for the corresponding spaces. |
| EvacuateNewSpaceVisitor new_space_visitor_; |
| EvacuateOldSpaceVisitor old_space_visitor_; |
| |
| // Book keeping info. |
| double duration_; |
| intptr_t bytes_compacted_; |
| |
| // Task id, if this evacuator is executed on a background task instead of |
| // the main thread. Can be used to try to abort the task currently scheduled |
| // to executed to evacuate pages. |
| uint32_t task_id_; |
| }; |
| |
| bool MarkCompactCollector::Evacuator::EvacuateSinglePage( |
| MemoryChunk* p, HeapObjectVisitor* visitor) { |
| bool success = true; |
| if (p->parallel_compaction_state().TrySetValue( |
| MemoryChunk::kCompactingDone, MemoryChunk::kCompactingInProgress)) { |
| if (p->IsEvacuationCandidate() || p->InNewSpace()) { |
| DCHECK_EQ(p->parallel_compaction_state().Value(), |
| MemoryChunk::kCompactingInProgress); |
| int saved_live_bytes = p->LiveBytes(); |
| double evacuation_time; |
| { |
| AlwaysAllocateScope always_allocate(heap()->isolate()); |
| TimedScope timed_scope(&evacuation_time); |
| success = collector_->VisitLiveObjects(p, visitor, kClearMarkbits); |
| } |
| if (success) { |
| ReportCompactionProgress(evacuation_time, saved_live_bytes); |
| p->parallel_compaction_state().SetValue( |
| MemoryChunk::kCompactingFinalize); |
| } else { |
| p->parallel_compaction_state().SetValue( |
| MemoryChunk::kCompactingAborted); |
| } |
| } else { |
| // There could be popular pages in the list of evacuation candidates |
| // which we do not compact. |
| p->parallel_compaction_state().SetValue(MemoryChunk::kCompactingDone); |
| } |
| } |
| return success; |
| } |
| |
| void MarkCompactCollector::Evacuator::EvacuatePages() { |
| for (NewSpacePage* p : newspace_evacuation_candidates_) { |
| DCHECK(p->InNewSpace()); |
| DCHECK_EQ(p->concurrent_sweeping_state().Value(), |
| NewSpacePage::kSweepingDone); |
| bool success = EvacuateSinglePage(p, &new_space_visitor_); |
| DCHECK(success); |
| USE(success); |
| } |
| for (Page* p : evacuation_candidates_) { |
| DCHECK(p->IsEvacuationCandidate() || |
| p->IsFlagSet(MemoryChunk::RESCAN_ON_EVACUATION)); |
| DCHECK_EQ(p->concurrent_sweeping_state().Value(), Page::kSweepingDone); |
| EvacuateSinglePage(p, &old_space_visitor_); |
| } |
| } |
| |
| void MarkCompactCollector::Evacuator::Finalize() { |
| heap()->old_space()->MergeCompactionSpace(compaction_spaces_.Get(OLD_SPACE)); |
| heap()->code_space()->MergeCompactionSpace( |
| compaction_spaces_.Get(CODE_SPACE)); |
| heap()->tracer()->AddCompactionEvent(duration_, bytes_compacted_); |
| heap()->IncrementPromotedObjectsSize(new_space_visitor_.promoted_size()); |
| heap()->IncrementSemiSpaceCopiedObjectSize( |
| new_space_visitor_.semispace_copied_size()); |
| heap()->IncrementYoungSurvivorsCounter( |
| new_space_visitor_.promoted_size() + |
| new_space_visitor_.semispace_copied_size()); |
| heap()->MergeAllocationSitePretenuringFeedback(local_pretenuring_feedback_); |
| local_store_buffer_.Process(heap()->store_buffer()); |
| collector_->AddEvacuationSlotsBufferSynchronized(local_slots_buffer_); |
| } |
| |
| class MarkCompactCollector::CompactionTask : public CancelableTask { |
| public: |
| explicit CompactionTask(Heap* heap, Evacuator* evacuator) |
| : CancelableTask(heap->isolate()), heap_(heap), evacuator_(evacuator) { |
| evacuator->set_task_id(id()); |
| } |
| |
| virtual ~CompactionTask() {} |
| |
| private: |
| // v8::internal::CancelableTask overrides. |
| void RunInternal() override { |
| evacuator_->EvacuatePages(); |
| heap_->mark_compact_collector() |
| ->pending_compaction_tasks_semaphore_.Signal(); |
| } |
| |
| Heap* heap_; |
| Evacuator* evacuator_; |
| |
| DISALLOW_COPY_AND_ASSIGN(CompactionTask); |
| }; |
| |
| int MarkCompactCollector::NumberOfParallelCompactionTasks(int pages, |
| intptr_t live_bytes) { |
| if (!FLAG_parallel_compaction) return 1; |
| // Compute the number of needed tasks based on a target compaction time, the |
| // profiled compaction speed and marked live memory. |
| // |
| // The number of parallel compaction tasks is limited by: |
| // - #evacuation pages |
| // - (#cores - 1) |
| const double kTargetCompactionTimeInMs = 1; |
| const int kNumSweepingTasks = 3; |
| |
| intptr_t compaction_speed = |
| heap()->tracer()->CompactionSpeedInBytesPerMillisecond(); |
| |
| const int available_cores = |
| Max(1, base::SysInfo::NumberOfProcessors() - kNumSweepingTasks - 1); |
| int tasks; |
| if (compaction_speed > 0) { |
| tasks = 1 + static_cast<int>(static_cast<double>(live_bytes) / |
| compaction_speed / kTargetCompactionTimeInMs); |
| } else { |
| tasks = pages; |
| } |
| const int tasks_capped_pages = Min(pages, tasks); |
| return Min(available_cores, tasks_capped_pages); |
| } |
| |
| |
| void MarkCompactCollector::EvacuatePagesInParallel() { |
| int num_pages = 0; |
| intptr_t live_bytes = 0; |
| for (Page* page : evacuation_candidates_) { |
| num_pages++; |
| live_bytes += page->LiveBytes(); |
| } |
| for (NewSpacePage* page : newspace_evacuation_candidates_) { |
| num_pages++; |
| live_bytes += page->LiveBytes(); |
| } |
| DCHECK_GE(num_pages, 1); |
| |
| // Used for trace summary. |
| intptr_t compaction_speed = 0; |
| if (FLAG_trace_fragmentation) { |
| compaction_speed = heap()->tracer()->CompactionSpeedInBytesPerMillisecond(); |
| } |
| |
| const int num_tasks = NumberOfParallelCompactionTasks(num_pages, live_bytes); |
| |
| // Set up compaction spaces. |
| Evacuator** evacuators = new Evacuator*[num_tasks]; |
| for (int i = 0; i < num_tasks; i++) { |
| evacuators[i] = new Evacuator(this, evacuation_candidates_, |
| newspace_evacuation_candidates_); |
| } |
| |
| // Kick off parallel tasks. |
| StartParallelCompaction(evacuators, num_tasks); |
| // Wait for unfinished and not-yet-started tasks. |
| WaitUntilCompactionCompleted(&evacuators[1], num_tasks - 1); |
| |
| // Finalize local evacuators by merging back all locally cached data. |
| for (int i = 0; i < num_tasks; i++) { |
| evacuators[i]->Finalize(); |
| delete evacuators[i]; |
| } |
| delete[] evacuators; |
| |
| // Finalize pages sequentially. |
| for (NewSpacePage* p : newspace_evacuation_candidates_) { |
| DCHECK_EQ(p->parallel_compaction_state().Value(), |
| MemoryChunk::kCompactingFinalize); |
| p->parallel_compaction_state().SetValue(MemoryChunk::kCompactingDone); |
| } |
| |
| int abandoned_pages = 0; |
| for (Page* p : evacuation_candidates_) { |
| switch (p->parallel_compaction_state().Value()) { |
| case MemoryChunk::ParallelCompactingState::kCompactingAborted: |
| // We have partially compacted the page, i.e., some objects may have |
| // moved, others are still in place. |
| // We need to: |
| // - Leave the evacuation candidate flag for later processing of |
| // slots buffer entries. |
| // - Leave the slots buffer there for processing of entries added by |
| // the write barrier. |
| // - Rescan the page as slot recording in the migration buffer only |
| // happens upon moving (which we potentially didn't do). |
| // - Leave the page in the list of pages of a space since we could not |
| // fully evacuate it. |
| // - Mark them for rescanning for store buffer entries as we otherwise |
| // might have stale store buffer entries that become "valid" again |
| // after reusing the memory. Note that all existing store buffer |
| // entries of such pages are filtered before rescanning. |
| DCHECK(p->IsEvacuationCandidate()); |
| p->SetFlag(Page::COMPACTION_WAS_ABORTED); |
| abandoned_pages++; |
| break; |
| case MemoryChunk::kCompactingFinalize: |
| DCHECK(p->IsEvacuationCandidate()); |
| DCHECK(p->SweepingDone()); |
| p->Unlink(); |
| break; |
| case MemoryChunk::kCompactingDone: |
| DCHECK(p->IsFlagSet(Page::POPULAR_PAGE)); |
| DCHECK(p->IsFlagSet(Page::RESCAN_ON_EVACUATION)); |
| break; |
| default: |
| // MemoryChunk::kCompactingInProgress. |
| UNREACHABLE(); |
| } |
| p->parallel_compaction_state().SetValue(MemoryChunk::kCompactingDone); |
| } |
| if (FLAG_trace_fragmentation) { |
| PrintIsolate(isolate(), |
| "%8.0f ms: compaction: parallel=%d pages=%d aborted=%d " |
| "tasks=%d cores=%d live_bytes=%" V8_PTR_PREFIX |
| "d compaction_speed=%" V8_PTR_PREFIX "d\n", |
| isolate()->time_millis_since_init(), FLAG_parallel_compaction, |
| num_pages, abandoned_pages, num_tasks, |
| base::SysInfo::NumberOfProcessors(), live_bytes, |
| compaction_speed); |
| } |
| } |
| |
| void MarkCompactCollector::StartParallelCompaction(Evacuator** evacuators, |
| int len) { |
| compaction_in_progress_ = true; |
| for (int i = 1; i < len; i++) { |
| CompactionTask* task = new CompactionTask(heap(), evacuators[i]); |
| V8::GetCurrentPlatform()->CallOnBackgroundThread( |
| task, v8::Platform::kShortRunningTask); |
| } |
| |
| // Contribute on main thread. |
| evacuators[0]->EvacuatePages(); |
| } |
| |
| void MarkCompactCollector::WaitUntilCompactionCompleted(Evacuator** evacuators, |
| int len) { |
| // Try to cancel compaction tasks that have not been run (as they might be |
| // stuck in a worker queue). Tasks that cannot be canceled, have either |
| // already completed or are still running, hence we need to wait for their |
| // semaphore signal. |
| for (int i = 0; i < len; i++) { |
| if (!heap()->isolate()->cancelable_task_manager()->TryAbort( |
| evacuators[i]->task_id())) { |
| pending_compaction_tasks_semaphore_.Wait(); |
| } |
| } |
| compaction_in_progress_ = false; |
| } |
| |
| |
| class EvacuationWeakObjectRetainer : public WeakObjectRetainer { |
| public: |
| virtual Object* RetainAs(Object* object) { |
| if (object->IsHeapObject()) { |
| HeapObject* heap_object = HeapObject::cast(object); |
| MapWord map_word = heap_object->map_word(); |
| if (map_word.IsForwardingAddress()) { |
| return map_word.ToForwardingAddress(); |
| } |
| } |
| return object; |
| } |
| }; |
| |
| |
| enum SweepingMode { SWEEP_ONLY, SWEEP_AND_VISIT_LIVE_OBJECTS }; |
| |
| |
| enum SkipListRebuildingMode { REBUILD_SKIP_LIST, IGNORE_SKIP_LIST }; |
| |
| |
| enum FreeSpaceTreatmentMode { IGNORE_FREE_SPACE, ZAP_FREE_SPACE }; |
| |
| |
| template <MarkCompactCollector::SweepingParallelism mode> |
| static intptr_t Free(PagedSpace* space, FreeList* free_list, Address start, |
| int size) { |
| if (mode == MarkCompactCollector::SWEEP_ON_MAIN_THREAD) { |
| DCHECK(free_list == NULL); |
| return space->Free(start, size); |
| } else { |
| return size - free_list->Free(start, size); |
| } |
| } |
| |
| |
| // Sweeps a page. After sweeping the page can be iterated. |
| // Slots in live objects pointing into evacuation candidates are updated |
| // if requested. |
| // Returns the size of the biggest continuous freed memory chunk in bytes. |
| template <SweepingMode sweeping_mode, |
| MarkCompactCollector::SweepingParallelism parallelism, |
| SkipListRebuildingMode skip_list_mode, |
| FreeSpaceTreatmentMode free_space_mode> |
| static int Sweep(PagedSpace* space, FreeList* free_list, Page* p, |
| ObjectVisitor* v) { |
| DCHECK(!p->IsEvacuationCandidate() && !p->SweepingDone()); |
| DCHECK_EQ(skip_list_mode == REBUILD_SKIP_LIST, |
| space->identity() == CODE_SPACE); |
| DCHECK((p->skip_list() == NULL) || (skip_list_mode == REBUILD_SKIP_LIST)); |
| DCHECK(parallelism == MarkCompactCollector::SWEEP_ON_MAIN_THREAD || |
| sweeping_mode == SWEEP_ONLY); |
| |
| Address free_start = p->area_start(); |
| DCHECK(reinterpret_cast<intptr_t>(free_start) % (32 * kPointerSize) == 0); |
| |
| // If we use the skip list for code space pages, we have to lock the skip |
| // list because it could be accessed concurrently by the runtime or the |
| // deoptimizer. |
| SkipList* skip_list = p->skip_list(); |
| if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list) { |
| skip_list->Clear(); |
| } |
| |
| intptr_t freed_bytes = 0; |
| intptr_t max_freed_bytes = 0; |
| int curr_region = -1; |
| |
| LiveObjectIterator<kBlackObjects> it(p); |
| HeapObject* object = NULL; |
| while ((object = it.Next()) != NULL) { |
| DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| Address free_end = object->address(); |
| if (free_end != free_start) { |
| int size = static_cast<int>(free_end - free_start); |
| if (free_space_mode == ZAP_FREE_SPACE) { |
| memset(free_start, 0xcc, size); |
| } |
| freed_bytes = Free<parallelism>(space, free_list, free_start, size); |
| max_freed_bytes = Max(freed_bytes, max_freed_bytes); |
| } |
| Map* map = object->synchronized_map(); |
| int size = object->SizeFromMap(map); |
| if (sweeping_mode == SWEEP_AND_VISIT_LIVE_OBJECTS) { |
| object->IterateBody(map->instance_type(), size, v); |
| } |
| if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list != NULL) { |
| int new_region_start = SkipList::RegionNumber(free_end); |
| int new_region_end = |
| SkipList::RegionNumber(free_end + size - kPointerSize); |
| if (new_region_start != curr_region || new_region_end != curr_region) { |
| skip_list->AddObject(free_end, size); |
| curr_region = new_region_end; |
| } |
| } |
| free_start = free_end + size; |
| } |
| |
| // Clear the mark bits of that page and reset live bytes count. |
| Bitmap::Clear(p); |
| |
| if (free_start != p->area_end()) { |
| int size = static_cast<int>(p->area_end() - free_start); |
| if (free_space_mode == ZAP_FREE_SPACE) { |
| memset(free_start, 0xcc, size); |
| } |
| freed_bytes = Free<parallelism>(space, free_list, free_start, size); |
| max_freed_bytes = Max(freed_bytes, max_freed_bytes); |
| } |
| p->concurrent_sweeping_state().SetValue(Page::kSweepingDone); |
| return FreeList::GuaranteedAllocatable(static_cast<int>(max_freed_bytes)); |
| } |
| |
| |
| void MarkCompactCollector::InvalidateCode(Code* code) { |
| if (heap_->incremental_marking()->IsCompacting() && |
| !ShouldSkipEvacuationSlotRecording(code)) { |
| DCHECK(compacting_); |
| |
| // If the object is white than no slots were recorded on it yet. |
| MarkBit mark_bit = Marking::MarkBitFrom(code); |
| if (Marking::IsWhite(mark_bit)) return; |
| |
| // Ignore all slots that might have been recorded in the body of the |
| // deoptimized code object. Assumption: no slots will be recorded for |
| // this object after invalidating it. |
| RemoveObjectSlots(code->instruction_start(), |
| code->address() + code->Size()); |
| } |
| } |
| |
| |
| // Return true if the given code is deoptimized or will be deoptimized. |
| bool MarkCompactCollector::WillBeDeoptimized(Code* code) { |
| return code->is_optimized_code() && code->marked_for_deoptimization(); |
| } |
| |
| |
| void MarkCompactCollector::RemoveObjectSlots(Address start_slot, |
| Address end_slot) { |
| // Remove entries by replacing them with an old-space slot containing a smi |
| // that is located in an unmovable page. |
| for (Page* p : evacuation_candidates_) { |
| DCHECK(p->IsEvacuationCandidate() || |
| p->IsFlagSet(Page::RESCAN_ON_EVACUATION)); |
| if (p->IsEvacuationCandidate()) { |
| SlotsBuffer::RemoveObjectSlots(heap_, p->slots_buffer(), start_slot, |
| end_slot); |
| } |
| } |
| } |
| |
| |
| #ifdef VERIFY_HEAP |
| static void VerifyAllBlackObjects(MemoryChunk* page) { |
| LiveObjectIterator<kAllLiveObjects> it(page); |
| HeapObject* object = NULL; |
| while ((object = it.Next()) != NULL) { |
| CHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| } |
| } |
| #endif // VERIFY_HEAP |
| |
| |
| bool MarkCompactCollector::VisitLiveObjects(MemoryChunk* page, |
| HeapObjectVisitor* visitor, |
| IterationMode mode) { |
| #ifdef VERIFY_HEAP |
| VerifyAllBlackObjects(page); |
| #endif // VERIFY_HEAP |
| |
| LiveObjectIterator<kBlackObjects> it(page); |
| HeapObject* object = nullptr; |
| while ((object = it.Next()) != nullptr) { |
| DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| if (!visitor->Visit(object)) { |
| if (mode == kClearMarkbits) { |
| page->markbits()->ClearRange( |
| page->AddressToMarkbitIndex(page->area_start()), |
| page->AddressToMarkbitIndex(object->address())); |
| if (page->old_to_new_slots() != nullptr) { |
| page->old_to_new_slots()->RemoveRange( |
| 0, static_cast<int>(object->address() - page->address())); |
| } |
| RecomputeLiveBytes(page); |
| } |
| return false; |
| } |
| } |
| if (mode == kClearMarkbits) { |
| Bitmap::Clear(page); |
| } |
| return true; |
| } |
| |
| |
| void MarkCompactCollector::RecomputeLiveBytes(MemoryChunk* page) { |
| LiveObjectIterator<kBlackObjects> it(page); |
| int new_live_size = 0; |
| HeapObject* object = nullptr; |
| while ((object = it.Next()) != nullptr) { |
| new_live_size += object->Size(); |
| } |
| page->SetLiveBytes(new_live_size); |
| } |
| |
| |
| void MarkCompactCollector::VisitLiveObjectsBody(Page* page, |
| ObjectVisitor* visitor) { |
| #ifdef VERIFY_HEAP |
| VerifyAllBlackObjects(page); |
| #endif // VERIFY_HEAP |
| |
| LiveObjectIterator<kBlackObjects> it(page); |
| HeapObject* object = NULL; |
| while ((object = it.Next()) != NULL) { |
| DCHECK(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| Map* map = object->synchronized_map(); |
| int size = object->SizeFromMap(map); |
| object->IterateBody(map->instance_type(), size, visitor); |
| } |
| } |
| |
| |
| void MarkCompactCollector::SweepAbortedPages() { |
| // Second pass on aborted pages. |
| for (Page* p : evacuation_candidates_) { |
| if (p->IsFlagSet(Page::COMPACTION_WAS_ABORTED)) { |
| p->ClearFlag(MemoryChunk::COMPACTION_WAS_ABORTED); |
| p->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress); |
| PagedSpace* space = static_cast<PagedSpace*>(p->owner()); |
| switch (space->identity()) { |
| case OLD_SPACE: |
| Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, IGNORE_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, nullptr, p, nullptr); |
| break; |
| case CODE_SPACE: |
| if (FLAG_zap_code_space) { |
| Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, REBUILD_SKIP_LIST, |
| ZAP_FREE_SPACE>(space, NULL, p, nullptr); |
| } else { |
| Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, REBUILD_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, NULL, p, nullptr); |
| } |
| break; |
| default: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::EvacuateNewSpaceAndCandidates() { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_EVACUATE); |
| Heap::RelocationLock relocation_lock(heap()); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_NEW_SPACE); |
| EvacuationScope evacuation_scope(this); |
| |
| EvacuateNewSpacePrologue(); |
| EvacuatePagesInParallel(); |
| EvacuateNewSpaceEpilogue(); |
| heap()->new_space()->set_age_mark(heap()->new_space()->top()); |
| } |
| |
| UpdatePointersAfterEvacuation(); |
| |
| // Give pages that are queued to be freed back to the OS. Note that filtering |
| // slots only handles old space (for unboxed doubles), and thus map space can |
| // still contain stale pointers. We only free the chunks after pointer updates |
| // to still have access to page headers. |
| heap()->FreeQueuedChunks(); |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_CLEAN_UP); |
| // After updating all pointers, we can finally sweep the aborted pages, |
| // effectively overriding any forward pointers. |
| SweepAbortedPages(); |
| |
| // EvacuateNewSpaceAndCandidates iterates over new space objects and for |
| // ArrayBuffers either re-registers them as live or promotes them. This is |
| // needed to properly free them. |
| heap()->array_buffer_tracker()->FreeDead(false); |
| |
| // Deallocate evacuated candidate pages. |
| ReleaseEvacuationCandidates(); |
| } |
| |
| #ifdef VERIFY_HEAP |
| if (FLAG_verify_heap && !sweeping_in_progress_) { |
| VerifyEvacuation(heap()); |
| } |
| #endif |
| } |
| |
| |
| void MarkCompactCollector::UpdatePointersAfterEvacuation() { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS); |
| { |
| GCTracer::Scope gc_scope( |
| heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS_TO_EVACUATED); |
| UpdateSlotsRecordedIn(migration_slots_buffer_); |
| if (FLAG_trace_fragmentation_verbose) { |
| PrintF(" migration slots buffer: %d\n", |
| SlotsBuffer::SizeOfChain(migration_slots_buffer_)); |
| } |
| slots_buffer_allocator_->DeallocateChain(&migration_slots_buffer_); |
| DCHECK(migration_slots_buffer_ == NULL); |
| |
| // TODO(hpayer): Process the slots buffers in parallel. This has to be done |
| // after evacuation of all pages finishes. |
| int buffers = evacuation_slots_buffers_.length(); |
| for (int i = 0; i < buffers; i++) { |
| SlotsBuffer* buffer = evacuation_slots_buffers_[i]; |
| UpdateSlotsRecordedIn(buffer); |
| slots_buffer_allocator_->DeallocateChain(&buffer); |
| } |
| evacuation_slots_buffers_.Rewind(0); |
| } |
| |
| // Second pass: find pointers to new space and update them. |
| PointersUpdatingVisitor updating_visitor(heap()); |
| |
| { |
| GCTracer::Scope gc_scope( |
| heap()->tracer(), GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS_TO_NEW); |
| // Update pointers in to space. |
| SemiSpaceIterator to_it(heap()->new_space()); |
| for (HeapObject* object = to_it.Next(); object != NULL; |
| object = to_it.Next()) { |
| Map* map = object->map(); |
| object->IterateBody(map->instance_type(), object->SizeFromMap(map), |
| &updating_visitor); |
| } |
| // Update roots. |
| heap_->IterateRoots(&updating_visitor, VISIT_ALL_IN_SWEEP_NEWSPACE); |
| |
| RememberedSet<OLD_TO_NEW>::IterateWithWrapper(heap_, UpdatePointer); |
| } |
| |
| { |
| GCTracer::Scope gc_scope( |
| heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS_BETWEEN_EVACUATED); |
| for (Page* p : evacuation_candidates_) { |
| DCHECK(p->IsEvacuationCandidate() || |
| p->IsFlagSet(Page::RESCAN_ON_EVACUATION)); |
| |
| if (p->IsEvacuationCandidate()) { |
| UpdateSlotsRecordedIn(p->slots_buffer()); |
| if (FLAG_trace_fragmentation_verbose) { |
| PrintF(" page %p slots buffer: %d\n", reinterpret_cast<void*>(p), |
| SlotsBuffer::SizeOfChain(p->slots_buffer())); |
| } |
| slots_buffer_allocator_->DeallocateChain(p->slots_buffer_address()); |
| |
| // Important: skip list should be cleared only after roots were updated |
| // because root iteration traverses the stack and might have to find |
| // code objects from non-updated pc pointing into evacuation candidate. |
| SkipList* list = p->skip_list(); |
| if (list != NULL) list->Clear(); |
| |
| // First pass on aborted pages, fixing up all live objects. |
| if (p->IsFlagSet(Page::COMPACTION_WAS_ABORTED)) { |
| p->ClearEvacuationCandidate(); |
| VisitLiveObjectsBody(p, &updating_visitor); |
| } |
| } |
| |
| if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) { |
| if (FLAG_gc_verbose) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " during evacuation.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| PagedSpace* space = static_cast<PagedSpace*>(p->owner()); |
| p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION); |
| p->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress); |
| |
| switch (space->identity()) { |
| case OLD_SPACE: |
| Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD, |
| IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(space, NULL, p, |
| &updating_visitor); |
| break; |
| case CODE_SPACE: |
| if (FLAG_zap_code_space) { |
| Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD, |
| REBUILD_SKIP_LIST, ZAP_FREE_SPACE>(space, NULL, p, |
| &updating_visitor); |
| } else { |
| Sweep<SWEEP_AND_VISIT_LIVE_OBJECTS, SWEEP_ON_MAIN_THREAD, |
| REBUILD_SKIP_LIST, IGNORE_FREE_SPACE>(space, NULL, p, |
| &updating_visitor); |
| } |
| break; |
| default: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| } |
| } |
| |
| { |
| GCTracer::Scope gc_scope(heap()->tracer(), |
| GCTracer::Scope::MC_EVACUATE_UPDATE_POINTERS_WEAK); |
| heap_->string_table()->Iterate(&updating_visitor); |
| |
| // Update pointers from external string table. |
| heap_->UpdateReferencesInExternalStringTable( |
| &UpdateReferenceInExternalStringTableEntry); |
| |
| EvacuationWeakObjectRetainer evacuation_object_retainer; |
| heap()->ProcessAllWeakReferences(&evacuation_object_retainer); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ReleaseEvacuationCandidates() { |
| for (Page* p : evacuation_candidates_) { |
| if (!p->IsEvacuationCandidate()) continue; |
| PagedSpace* space = static_cast<PagedSpace*>(p->owner()); |
| space->Free(p->area_start(), p->area_size()); |
| p->ResetLiveBytes(); |
| CHECK(p->SweepingDone()); |
| space->ReleasePage(p, true); |
| } |
| evacuation_candidates_.Rewind(0); |
| compacting_ = false; |
| heap()->FreeQueuedChunks(); |
| } |
| |
| |
| int MarkCompactCollector::SweepInParallel(PagedSpace* space, |
| int required_freed_bytes, |
| int max_pages) { |
| int max_freed = 0; |
| int max_freed_overall = 0; |
| int page_count = 0; |
| for (Page* p : sweeping_list(space)) { |
| max_freed = SweepInParallel(p, space); |
| DCHECK(max_freed >= 0); |
| if (required_freed_bytes > 0 && max_freed >= required_freed_bytes) { |
| return max_freed; |
| } |
| max_freed_overall = Max(max_freed, max_freed_overall); |
| page_count++; |
| if (max_pages > 0 && page_count >= max_pages) { |
| break; |
| } |
| } |
| return max_freed_overall; |
| } |
| |
| |
| int MarkCompactCollector::SweepInParallel(Page* page, PagedSpace* space) { |
| int max_freed = 0; |
| if (page->mutex()->TryLock()) { |
| // If this page was already swept in the meantime, we can return here. |
| if (page->concurrent_sweeping_state().Value() != Page::kSweepingPending) { |
| page->mutex()->Unlock(); |
| return 0; |
| } |
| page->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress); |
| FreeList* free_list; |
| FreeList private_free_list(space); |
| if (space->identity() == OLD_SPACE) { |
| free_list = free_list_old_space_.get(); |
| max_freed = |
| Sweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, &private_free_list, page, NULL); |
| } else if (space->identity() == CODE_SPACE) { |
| free_list = free_list_code_space_.get(); |
| max_freed = |
| Sweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, REBUILD_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, &private_free_list, page, NULL); |
| } else { |
| free_list = free_list_map_space_.get(); |
| max_freed = |
| Sweep<SWEEP_ONLY, SWEEP_IN_PARALLEL, IGNORE_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, &private_free_list, page, NULL); |
| } |
| free_list->Concatenate(&private_free_list); |
| page->concurrent_sweeping_state().SetValue(Page::kSweepingDone); |
| page->mutex()->Unlock(); |
| } |
| return max_freed; |
| } |
| |
| |
| void MarkCompactCollector::StartSweepSpace(PagedSpace* space) { |
| space->ClearStats(); |
| |
| PageIterator it(space); |
| |
| int will_be_swept = 0; |
| bool unused_page_present = false; |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| DCHECK(p->SweepingDone()); |
| |
| if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION) || |
| p->IsEvacuationCandidate()) { |
| // Will be processed in EvacuateNewSpaceAndCandidates. |
| DCHECK(evacuation_candidates_.length() > 0); |
| continue; |
| } |
| |
| if (p->IsFlagSet(Page::NEVER_ALLOCATE_ON_PAGE)) { |
| // We need to sweep the page to get it into an iterable state again. Note |
| // that this adds unusable memory into the free list that is later on |
| // (in the free list) dropped again. Since we only use the flag for |
| // testing this is fine. |
| p->concurrent_sweeping_state().SetValue(Page::kSweepingInProgress); |
| Sweep<SWEEP_ONLY, SWEEP_ON_MAIN_THREAD, IGNORE_SKIP_LIST, |
| IGNORE_FREE_SPACE>(space, nullptr, p, nullptr); |
| continue; |
| } |
| |
| // One unused page is kept, all further are released before sweeping them. |
| if (p->LiveBytes() == 0) { |
| if (unused_page_present) { |
| if (FLAG_gc_verbose) { |
| PrintIsolate(isolate(), "sweeping: released page: %p", p); |
| } |
| space->ReleasePage(p, false); |
| continue; |
| } |
| unused_page_present = true; |
| } |
| |
| p->concurrent_sweeping_state().SetValue(Page::kSweepingPending); |
| sweeping_list(space).push_back(p); |
| int to_sweep = p->area_size() - p->LiveBytes(); |
| space->accounting_stats_.ShrinkSpace(to_sweep); |
| will_be_swept++; |
| } |
| |
| if (FLAG_gc_verbose) { |
| PrintIsolate(isolate(), "sweeping: space=%s initialized_for_sweeping=%d", |
| AllocationSpaceName(space->identity()), will_be_swept); |
| } |
| std::sort(sweeping_list(space).begin(), sweeping_list(space).end(), |
| [](Page* a, Page* b) { return a->LiveBytes() < b->LiveBytes(); }); |
| } |
| |
| |
| void MarkCompactCollector::SweepSpaces() { |
| GCTracer::Scope gc_scope(heap()->tracer(), GCTracer::Scope::MC_SWEEP); |
| double start_time = 0.0; |
| if (FLAG_print_cumulative_gc_stat) { |
| start_time = heap_->MonotonicallyIncreasingTimeInMs(); |
| } |
| |
| #ifdef DEBUG |
| state_ = SWEEP_SPACES; |
| #endif |
| |
| { |
| sweeping_in_progress_ = true; |
| { |
| GCTracer::Scope sweep_scope(heap()->tracer(), |
| GCTracer::Scope::MC_SWEEP_OLD); |
| StartSweepSpace(heap()->old_space()); |
| } |
| { |
| GCTracer::Scope sweep_scope(heap()->tracer(), |
| GCTracer::Scope::MC_SWEEP_CODE); |
| StartSweepSpace(heap()->code_space()); |
| } |
| { |
| GCTracer::Scope sweep_scope(heap()->tracer(), |
| GCTracer::Scope::MC_SWEEP_MAP); |
| StartSweepSpace(heap()->map_space()); |
| } |
| if (FLAG_concurrent_sweeping) { |
| StartSweeperThreads(); |
| } |
| } |
| |
| // Deallocate unmarked large objects. |
| heap_->lo_space()->FreeUnmarkedObjects(); |
| |
| if (FLAG_print_cumulative_gc_stat) { |
| heap_->tracer()->AddSweepingTime(heap_->MonotonicallyIncreasingTimeInMs() - |
| start_time); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ParallelSweepSpacesComplete() { |
| sweeping_list(heap()->old_space()).clear(); |
| sweeping_list(heap()->code_space()).clear(); |
| sweeping_list(heap()->map_space()).clear(); |
| } |
| |
| |
| // TODO(1466) ReportDeleteIfNeeded is not called currently. |
| // Our profiling tools do not expect intersections between |
| // code objects. We should either reenable it or change our tools. |
| void MarkCompactCollector::ReportDeleteIfNeeded(HeapObject* obj, |
| Isolate* isolate) { |
| if (obj->IsCode()) { |
| PROFILE(isolate, CodeDeleteEvent(obj->address())); |
| } |
| } |
| |
| |
| Isolate* MarkCompactCollector::isolate() const { return heap_->isolate(); } |
| |
| |
| void MarkCompactCollector::Initialize() { |
| MarkCompactMarkingVisitor::Initialize(); |
| IncrementalMarking::Initialize(); |
| } |
| |
| |
| void MarkCompactCollector::EvictPopularEvacuationCandidate(Page* page) { |
| if (FLAG_trace_fragmentation) { |
| PrintF("Page %p is too popular. Disabling evacuation.\n", |
| reinterpret_cast<void*>(page)); |
| } |
| |
| isolate()->CountUsage(v8::Isolate::UseCounterFeature::kSlotsBufferOverflow); |
| |
| // TODO(gc) If all evacuation candidates are too popular we |
| // should stop slots recording entirely. |
| page->ClearEvacuationCandidate(); |
| |
| DCHECK(!page->IsFlagSet(Page::POPULAR_PAGE)); |
| page->SetFlag(Page::POPULAR_PAGE); |
| |
| // We were not collecting slots on this page that point |
| // to other evacuation candidates thus we have to |
| // rescan the page after evacuation to discover and update all |
| // pointers to evacuated objects. |
| page->SetFlag(Page::RESCAN_ON_EVACUATION); |
| } |
| |
| |
| void MarkCompactCollector::RecordCodeEntrySlot(HeapObject* object, Address slot, |
| Code* target) { |
| Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target)); |
| if (target_page->IsEvacuationCandidate() && |
| !ShouldSkipEvacuationSlotRecording(object)) { |
| if (!SlotsBuffer::AddTo(slots_buffer_allocator_, |
| target_page->slots_buffer_address(), |
| SlotsBuffer::CODE_ENTRY_SLOT, slot, |
| SlotsBuffer::FAIL_ON_OVERFLOW)) { |
| EvictPopularEvacuationCandidate(target_page); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::RecordCodeTargetPatch(Address pc, Code* target) { |
| DCHECK(heap()->gc_state() == Heap::MARK_COMPACT); |
| if (is_compacting()) { |
| Code* host = |
| isolate()->inner_pointer_to_code_cache()->GcSafeFindCodeForInnerPointer( |
| pc); |
| MarkBit mark_bit = Marking::MarkBitFrom(host); |
| if (Marking::IsBlack(mark_bit)) { |
| RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host); |
| RecordRelocSlot(&rinfo, target); |
| } |
| } |
| } |
| |
| } // namespace internal |
| } // namespace v8 |