| // Copyright 2012 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "v8.h" |
| |
| #include "code-stubs.h" |
| #include "compilation-cache.h" |
| #include "deoptimizer.h" |
| #include "execution.h" |
| #include "gdb-jit.h" |
| #include "global-handles.h" |
| #include "heap-profiler.h" |
| #include "ic-inl.h" |
| #include "incremental-marking.h" |
| #include "liveobjectlist-inl.h" |
| #include "mark-compact.h" |
| #include "objects-visiting.h" |
| #include "objects-visiting-inl.h" |
| #include "stub-cache.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| |
| const char* Marking::kWhiteBitPattern = "00"; |
| const char* Marking::kBlackBitPattern = "10"; |
| const char* Marking::kGreyBitPattern = "11"; |
| const char* Marking::kImpossibleBitPattern = "01"; |
| |
| |
| // ------------------------------------------------------------------------- |
| // MarkCompactCollector |
| |
| MarkCompactCollector::MarkCompactCollector() : // NOLINT |
| #ifdef DEBUG |
| state_(IDLE), |
| #endif |
| sweep_precisely_(false), |
| reduce_memory_footprint_(false), |
| abort_incremental_marking_(false), |
| compacting_(false), |
| was_marked_incrementally_(false), |
| flush_monomorphic_ics_(false), |
| tracer_(NULL), |
| migration_slots_buffer_(NULL), |
| heap_(NULL), |
| code_flusher_(NULL), |
| encountered_weak_maps_(NULL), |
| marker_(this, this) { } |
| |
| |
| #ifdef DEBUG |
| class VerifyMarkingVisitor: public ObjectVisitor { |
| public: |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** current = start; current < end; current++) { |
| if ((*current)->IsHeapObject()) { |
| HeapObject* object = HeapObject::cast(*current); |
| ASSERT(HEAP->mark_compact_collector()->IsMarked(object)); |
| } |
| } |
| } |
| }; |
| |
| |
| static void VerifyMarking(Address bottom, Address top) { |
| VerifyMarkingVisitor visitor; |
| 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)) { |
| ASSERT(current >= next_object_must_be_here_or_later); |
| object->Iterate(&visitor); |
| next_object_must_be_here_or_later = current + object->Size(); |
| } |
| } |
| } |
| |
| |
| 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. |
| ASSERT_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; |
| ASSERT(limit == end || !page->Contains(end)); |
| VerifyMarking(page->area_start(), limit); |
| } |
| } |
| |
| |
| static void VerifyMarking(PagedSpace* space) { |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| VerifyMarking(p->area_start(), p->area_end()); |
| } |
| } |
| |
| |
| static void VerifyMarking(Heap* heap) { |
| VerifyMarking(heap->old_pointer_space()); |
| VerifyMarking(heap->old_data_space()); |
| VerifyMarking(heap->code_space()); |
| VerifyMarking(heap->cell_space()); |
| VerifyMarking(heap->map_space()); |
| VerifyMarking(heap->new_space()); |
| |
| VerifyMarkingVisitor visitor; |
| |
| 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) { |
| for (Object** current = start; current < end; current++) { |
| if ((*current)->IsHeapObject()) { |
| HeapObject* object = HeapObject::cast(*current); |
| CHECK(!MarkCompactCollector::IsOnEvacuationCandidate(object)); |
| } |
| } |
| } |
| }; |
| |
| |
| static void VerifyEvacuation(Address bottom, Address top) { |
| VerifyEvacuationVisitor visitor; |
| 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)) { |
| ASSERT(current >= next_object_must_be_here_or_later); |
| object->Iterate(&visitor); |
| next_object_must_be_here_or_later = current + object->Size(); |
| } |
| } |
| } |
| |
| |
| 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(); |
| ASSERT(limit == space->top() || !page->Contains(space->top())); |
| while (current < limit) { |
| HeapObject* object = HeapObject::FromAddress(current); |
| object->Iterate(&visitor); |
| current += object->Size(); |
| } |
| } |
| } |
| |
| |
| static void VerifyEvacuation(PagedSpace* space) { |
| PageIterator it(space); |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| if (p->IsEvacuationCandidate()) continue; |
| VerifyEvacuation(p->area_start(), p->area_end()); |
| } |
| } |
| |
| |
| static void VerifyEvacuation(Heap* heap) { |
| VerifyEvacuation(heap->old_pointer_space()); |
| VerifyEvacuation(heap->old_data_space()); |
| VerifyEvacuation(heap->code_space()); |
| VerifyEvacuation(heap->cell_space()); |
| VerifyEvacuation(heap->map_space()); |
| VerifyEvacuation(heap->new_space()); |
| |
| VerifyEvacuationVisitor visitor; |
| heap->IterateStrongRoots(&visitor, VISIT_ALL); |
| } |
| #endif |
| |
| |
| void MarkCompactCollector::AddEvacuationCandidate(Page* p) { |
| 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_) { |
| ASSERT(evacuation_candidates_.length() == 0); |
| |
| CollectEvacuationCandidates(heap()->old_pointer_space()); |
| CollectEvacuationCandidates(heap()->old_data_space()); |
| |
| if (FLAG_compact_code_space && mode == NON_INCREMENTAL_COMPACTION) { |
| CollectEvacuationCandidates(heap()->code_space()); |
| } else if (FLAG_trace_fragmentation) { |
| TraceFragmentation(heap()->code_space()); |
| } |
| |
| if (FLAG_trace_fragmentation) { |
| TraceFragmentation(heap()->map_space()); |
| TraceFragmentation(heap()->cell_space()); |
| } |
| |
| heap()->old_pointer_space()->EvictEvacuationCandidatesFromFreeLists(); |
| heap()->old_data_space()->EvictEvacuationCandidatesFromFreeLists(); |
| heap()->code_space()->EvictEvacuationCandidatesFromFreeLists(); |
| |
| compacting_ = evacuation_candidates_.length() > 0; |
| } |
| |
| return compacting_; |
| } |
| |
| |
| void MarkCompactCollector::CollectGarbage() { |
| // Make sure that Prepare() has been called. The individual steps below will |
| // update the state as they proceed. |
| ASSERT(state_ == PREPARE_GC); |
| ASSERT(encountered_weak_maps_ == Smi::FromInt(0)); |
| |
| MarkLiveObjects(); |
| ASSERT(heap_->incremental_marking()->IsStopped()); |
| |
| if (FLAG_collect_maps) ClearNonLiveTransitions(); |
| |
| ClearWeakMaps(); |
| |
| #ifdef DEBUG |
| if (FLAG_verify_heap) { |
| VerifyMarking(heap_); |
| } |
| #endif |
| |
| SweepSpaces(); |
| |
| if (!FLAG_collect_maps) ReattachInitialMaps(); |
| |
| Finish(); |
| |
| tracer_ = NULL; |
| } |
| |
| |
| #ifdef DEBUG |
| 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_pointer_space()); |
| VerifyMarkbitsAreClean(heap_->old_data_space()); |
| VerifyMarkbitsAreClean(heap_->code_space()); |
| VerifyMarkbitsAreClean(heap_->cell_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); |
| ASSERT(Marking::IsWhite(mark_bit)); |
| ASSERT_EQ(0, Page::FromAddress(obj->address())->LiveBytes()); |
| } |
| } |
| #endif |
| |
| |
| 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_pointer_space()); |
| ClearMarkbitsInPagedSpace(heap_->old_data_space()); |
| ClearMarkbitsInPagedSpace(heap_->cell_space()); |
| ClearMarkbitsInNewSpace(heap_->new_space()); |
| |
| LargeObjectIterator it(heap_->lo_space()); |
| for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) { |
| MarkBit mark_bit = Marking::MarkBitFrom(obj); |
| mark_bit.Clear(); |
| mark_bit.Next().Clear(); |
| Page::FromAddress(obj->address())->ResetLiveBytes(); |
| } |
| } |
| |
| |
| bool Marking::TransferMark(Address old_start, Address new_start) { |
| // This is only used when resizing an object. |
| ASSERT(MemoryChunk::FromAddress(old_start) == |
| MemoryChunk::FromAddress(new_start)); |
| |
| // 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 false; |
| |
| 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)) { |
| old_mark_bit.Clear(); |
| ASSERT(IsWhite(old_mark_bit)); |
| Marking::MarkBlack(new_mark_bit); |
| return true; |
| } else if (Marking::IsGrey(old_mark_bit)) { |
| ASSERT(heap_->incremental_marking()->IsMarking()); |
| old_mark_bit.Clear(); |
| old_mark_bit.Next().Clear(); |
| ASSERT(IsWhite(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); |
| ASSERT(new_color == old_color); |
| #endif |
| |
| return false; |
| } |
| |
| |
| const char* AllocationSpaceName(AllocationSpace space) { |
| switch (space) { |
| case NEW_SPACE: return "NEW_SPACE"; |
| case OLD_POINTER_SPACE: return "OLD_POINTER_SPACE"; |
| case OLD_DATA_SPACE: return "OLD_DATA_SPACE"; |
| case CODE_SPACE: return "CODE_SPACE"; |
| case MAP_SPACE: return "MAP_SPACE"; |
| case CELL_SPACE: return "CELL_SPACE"; |
| case LO_SPACE: return "LO_SPACE"; |
| default: |
| UNREACHABLE(); |
| } |
| |
| return NULL; |
| } |
| |
| |
| // Returns zero for pages that have so little fragmentation that it is not |
| // worth defragmenting them. Otherwise a positive integer that gives an |
| // estimate of fragmentation on an arbitrary scale. |
| static int FreeListFragmentation(PagedSpace* space, Page* p) { |
| // If page was not swept then there are no free list items on it. |
| if (!p->WasSwept()) { |
| if (FLAG_trace_fragmentation) { |
| PrintF("%p [%s]: %d bytes live (unswept)\n", |
| reinterpret_cast<void*>(p), |
| AllocationSpaceName(space->identity()), |
| p->LiveBytes()); |
| } |
| return 0; |
| } |
| |
| FreeList::SizeStats sizes; |
| space->CountFreeListItems(p, &sizes); |
| |
| intptr_t ratio; |
| intptr_t ratio_threshold; |
| intptr_t area_size = space->AreaSize(); |
| if (space->identity() == CODE_SPACE) { |
| ratio = (sizes.medium_size_ * 10 + sizes.large_size_ * 2) * 100 / |
| area_size; |
| ratio_threshold = 10; |
| } else { |
| ratio = (sizes.small_size_ * 5 + sizes.medium_size_) * 100 / |
| area_size; |
| ratio_threshold = 15; |
| } |
| |
| if (FLAG_trace_fragmentation) { |
| PrintF("%p [%s]: %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %s\n", |
| reinterpret_cast<void*>(p), |
| AllocationSpaceName(space->identity()), |
| static_cast<int>(sizes.small_size_), |
| static_cast<double>(sizes.small_size_ * 100) / |
| area_size, |
| static_cast<int>(sizes.medium_size_), |
| static_cast<double>(sizes.medium_size_ * 100) / |
| area_size, |
| static_cast<int>(sizes.large_size_), |
| static_cast<double>(sizes.large_size_ * 100) / |
| area_size, |
| static_cast<int>(sizes.huge_size_), |
| static_cast<double>(sizes.huge_size_ * 100) / |
| area_size, |
| (ratio > ratio_threshold) ? "[fragmented]" : ""); |
| } |
| |
| if (FLAG_always_compact && sizes.Total() != area_size) { |
| return 1; |
| } |
| |
| if (ratio <= ratio_threshold) return 0; // Not fragmented. |
| |
| return static_cast<int>(ratio - ratio_threshold); |
| } |
| |
| |
| void MarkCompactCollector::CollectEvacuationCandidates(PagedSpace* space) { |
| ASSERT(space->identity() == OLD_POINTER_SPACE || |
| space->identity() == OLD_DATA_SPACE || |
| space->identity() == CODE_SPACE); |
| |
| static const int kMaxMaxEvacuationCandidates = 1000; |
| int number_of_pages = space->CountTotalPages(); |
| int max_evacuation_candidates = |
| static_cast<int>(sqrt(static_cast<double>(number_of_pages / 2)) + 1); |
| |
| if (FLAG_stress_compaction || FLAG_always_compact) { |
| max_evacuation_candidates = kMaxMaxEvacuationCandidates; |
| } |
| |
| class Candidate { |
| public: |
| Candidate() : fragmentation_(0), page_(NULL) { } |
| Candidate(int f, Page* p) : fragmentation_(f), page_(p) { } |
| |
| int fragmentation() { return fragmentation_; } |
| Page* page() { return page_; } |
| |
| private: |
| int fragmentation_; |
| Page* page_; |
| }; |
| |
| enum CompactionMode { |
| COMPACT_FREE_LISTS, |
| REDUCE_MEMORY_FOOTPRINT |
| }; |
| |
| CompactionMode mode = COMPACT_FREE_LISTS; |
| |
| intptr_t reserved = number_of_pages * space->AreaSize(); |
| intptr_t over_reserved = reserved - space->SizeOfObjects(); |
| static const intptr_t kFreenessThreshold = 50; |
| |
| if (over_reserved >= 2 * space->AreaSize()) { |
| // If reduction of memory footprint was requested, we are aggressive |
| // about choosing pages to free. We expect that half-empty pages |
| // are easier to compact so slightly bump the limit. |
| if (reduce_memory_footprint_) { |
| mode = REDUCE_MEMORY_FOOTPRINT; |
| max_evacuation_candidates += 2; |
| } |
| |
| // If over-usage is very high (more than a third of the space), we |
| // try to free all mostly empty pages. We expect that almost empty |
| // pages are even easier to compact so bump the limit even more. |
| if (over_reserved > reserved / 3) { |
| mode = REDUCE_MEMORY_FOOTPRINT; |
| max_evacuation_candidates *= 2; |
| } |
| |
| if (FLAG_trace_fragmentation && mode == REDUCE_MEMORY_FOOTPRINT) { |
| PrintF("Estimated over reserved memory: %.1f / %.1f MB (threshold %d)\n", |
| static_cast<double>(over_reserved) / MB, |
| static_cast<double>(reserved) / MB, |
| static_cast<int>(kFreenessThreshold)); |
| } |
| } |
| |
| intptr_t estimated_release = 0; |
| |
| Candidate candidates[kMaxMaxEvacuationCandidates]; |
| |
| max_evacuation_candidates = |
| Min(kMaxMaxEvacuationCandidates, max_evacuation_candidates); |
| |
| int count = 0; |
| int fragmentation = 0; |
| Candidate* least = NULL; |
| |
| PageIterator it(space); |
| if (it.has_next()) it.next(); // Never compact the first page. |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| p->ClearEvacuationCandidate(); |
| |
| if (FLAG_stress_compaction) { |
| int counter = space->heap()->ms_count(); |
| uintptr_t page_number = reinterpret_cast<uintptr_t>(p) >> kPageSizeBits; |
| if ((counter & 1) == (page_number & 1)) fragmentation = 1; |
| } else if (mode == REDUCE_MEMORY_FOOTPRINT) { |
| // Don't try to release too many pages. |
| if (estimated_release >= ((over_reserved * 3) / 4)) { |
| continue; |
| } |
| |
| intptr_t free_bytes = 0; |
| |
| if (!p->WasSwept()) { |
| free_bytes = (p->area_size() - p->LiveBytes()); |
| } else { |
| FreeList::SizeStats sizes; |
| space->CountFreeListItems(p, &sizes); |
| free_bytes = sizes.Total(); |
| } |
| |
| int free_pct = static_cast<int>(free_bytes * 100) / p->area_size(); |
| |
| if (free_pct >= kFreenessThreshold) { |
| estimated_release += 2 * p->area_size() - free_bytes; |
| fragmentation = free_pct; |
| } else { |
| fragmentation = 0; |
| } |
| |
| if (FLAG_trace_fragmentation) { |
| PrintF("%p [%s]: %d (%.2f%%) free %s\n", |
| reinterpret_cast<void*>(p), |
| AllocationSpaceName(space->identity()), |
| static_cast<int>(free_bytes), |
| static_cast<double>(free_bytes * 100) / p->area_size(), |
| (fragmentation > 0) ? "[fragmented]" : ""); |
| } |
| } else { |
| fragmentation = FreeListFragmentation(space, p); |
| } |
| |
| if (fragmentation != 0) { |
| if (count < max_evacuation_candidates) { |
| candidates[count++] = Candidate(fragmentation, p); |
| } else { |
| if (least == NULL) { |
| for (int i = 0; i < max_evacuation_candidates; i++) { |
| if (least == NULL || |
| candidates[i].fragmentation() < least->fragmentation()) { |
| least = candidates + i; |
| } |
| } |
| } |
| if (least->fragmentation() < fragmentation) { |
| *least = Candidate(fragmentation, p); |
| least = NULL; |
| } |
| } |
| } |
| } |
| |
| for (int i = 0; i < count; i++) { |
| AddEvacuationCandidate(candidates[i].page()); |
| } |
| |
| if (count > 0 && FLAG_trace_fragmentation) { |
| PrintF("Collected %d evacuation candidates for space %s\n", |
| count, |
| AllocationSpaceName(space->identity())); |
| } |
| } |
| |
| |
| void MarkCompactCollector::AbortCompaction() { |
| if (compacting_) { |
| int npages = evacuation_candidates_.length(); |
| for (int i = 0; i < npages; i++) { |
| Page* p = evacuation_candidates_[i]; |
| slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address()); |
| p->ClearEvacuationCandidate(); |
| p->ClearFlag(MemoryChunk::RESCAN_ON_EVACUATION); |
| } |
| compacting_ = false; |
| evacuation_candidates_.Rewind(0); |
| invalidated_code_.Rewind(0); |
| } |
| ASSERT_EQ(0, evacuation_candidates_.length()); |
| } |
| |
| |
| void MarkCompactCollector::Prepare(GCTracer* tracer) { |
| was_marked_incrementally_ = heap()->incremental_marking()->IsMarking(); |
| |
| // Monomorphic ICs are preserved when possible, but need to be flushed |
| // when they might be keeping a Context alive, or when the heap is about |
| // to be serialized. |
| flush_monomorphic_ics_ = |
| heap()->isolate()->context_exit_happened() || Serializer::enabled(); |
| |
| // Rather than passing the tracer around we stash it in a static member |
| // variable. |
| tracer_ = tracer; |
| |
| #ifdef DEBUG |
| ASSERT(state_ == IDLE); |
| state_ = PREPARE_GC; |
| #endif |
| |
| ASSERT(!FLAG_never_compact || !FLAG_always_compact); |
| |
| #ifdef ENABLE_GDB_JIT_INTERFACE |
| if (FLAG_gdbjit) { |
| // If GDBJIT interface is active disable compaction. |
| compacting_collection_ = false; |
| } |
| #endif |
| |
| // Clear marking bits if incremental marking is aborted. |
| if (was_marked_incrementally_ && abort_incremental_marking_) { |
| heap()->incremental_marking()->Abort(); |
| ClearMarkbits(); |
| 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; |
| for (PagedSpace* space = spaces.next(); |
| space != NULL; |
| space = spaces.next()) { |
| space->PrepareForMarkCompact(); |
| } |
| |
| #ifdef DEBUG |
| if (!was_marked_incrementally_ && FLAG_verify_heap) { |
| VerifyMarkbitsAreClean(); |
| } |
| #endif |
| } |
| |
| |
| void MarkCompactCollector::Finish() { |
| #ifdef DEBUG |
| ASSERT(state_ == SWEEP_SPACES || state_ == RELOCATE_OBJECTS); |
| state_ = IDLE; |
| #endif |
| // 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). |
| heap()->isolate()->stub_cache()->Clear(); |
| |
| heap()->external_string_table_.CleanUp(); |
| } |
| |
| |
| // ------------------------------------------------------------------------- |
| // 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. |
| |
| class CodeFlusher { |
| public: |
| explicit CodeFlusher(Isolate* isolate) |
| : isolate_(isolate), |
| jsfunction_candidates_head_(NULL), |
| shared_function_info_candidates_head_(NULL) {} |
| |
| void AddCandidate(SharedFunctionInfo* shared_info) { |
| SetNextCandidate(shared_info, shared_function_info_candidates_head_); |
| shared_function_info_candidates_head_ = shared_info; |
| } |
| |
| void AddCandidate(JSFunction* function) { |
| ASSERT(function->code() == function->shared()->code()); |
| |
| SetNextCandidate(function, jsfunction_candidates_head_); |
| jsfunction_candidates_head_ = function; |
| } |
| |
| void ProcessCandidates() { |
| ProcessSharedFunctionInfoCandidates(); |
| ProcessJSFunctionCandidates(); |
| } |
| |
| private: |
| void ProcessJSFunctionCandidates() { |
| Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kLazyCompile); |
| |
| JSFunction* candidate = jsfunction_candidates_head_; |
| JSFunction* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| |
| SharedFunctionInfo* shared = candidate->shared(); |
| |
| Code* code = shared->code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| if (!code_mark.Get()) { |
| shared->set_code(lazy_compile); |
| candidate->set_code(lazy_compile); |
| } else { |
| candidate->set_code(shared->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(slot, target); |
| |
| RecordSharedFunctionInfoCodeSlot(shared); |
| |
| candidate = next_candidate; |
| } |
| |
| jsfunction_candidates_head_ = NULL; |
| } |
| |
| |
| void ProcessSharedFunctionInfoCandidates() { |
| Code* lazy_compile = isolate_->builtins()->builtin(Builtins::kLazyCompile); |
| |
| SharedFunctionInfo* candidate = shared_function_info_candidates_head_; |
| SharedFunctionInfo* next_candidate; |
| while (candidate != NULL) { |
| next_candidate = GetNextCandidate(candidate); |
| SetNextCandidate(candidate, NULL); |
| |
| Code* code = candidate->code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| if (!code_mark.Get()) { |
| candidate->set_code(lazy_compile); |
| } |
| |
| RecordSharedFunctionInfoCodeSlot(candidate); |
| |
| candidate = next_candidate; |
| } |
| |
| shared_function_info_candidates_head_ = NULL; |
| } |
| |
| void RecordSharedFunctionInfoCodeSlot(SharedFunctionInfo* shared) { |
| Object** slot = HeapObject::RawField(shared, |
| SharedFunctionInfo::kCodeOffset); |
| isolate_->heap()->mark_compact_collector()-> |
| RecordSlot(slot, slot, HeapObject::cast(*slot)); |
| } |
| |
| static JSFunction** GetNextCandidateField(JSFunction* candidate) { |
| return reinterpret_cast<JSFunction**>( |
| candidate->address() + JSFunction::kCodeEntryOffset); |
| } |
| |
| static JSFunction* GetNextCandidate(JSFunction* candidate) { |
| return *GetNextCandidateField(candidate); |
| } |
| |
| static void SetNextCandidate(JSFunction* candidate, |
| JSFunction* next_candidate) { |
| *GetNextCandidateField(candidate) = next_candidate; |
| } |
| |
| static SharedFunctionInfo** GetNextCandidateField( |
| SharedFunctionInfo* candidate) { |
| Code* code = candidate->code(); |
| return reinterpret_cast<SharedFunctionInfo**>( |
| code->address() + Code::kGCMetadataOffset); |
| } |
| |
| static SharedFunctionInfo* GetNextCandidate(SharedFunctionInfo* candidate) { |
| return reinterpret_cast<SharedFunctionInfo*>( |
| candidate->code()->gc_metadata()); |
| } |
| |
| static void SetNextCandidate(SharedFunctionInfo* candidate, |
| SharedFunctionInfo* next_candidate) { |
| candidate->code()->set_gc_metadata(next_candidate); |
| } |
| |
| Isolate* isolate_; |
| JSFunction* jsfunction_candidates_head_; |
| SharedFunctionInfo* shared_function_info_candidates_head_; |
| |
| DISALLOW_COPY_AND_ASSIGN(CodeFlusher); |
| }; |
| |
| |
| MarkCompactCollector::~MarkCompactCollector() { |
| if (code_flusher_ != NULL) { |
| delete code_flusher_; |
| code_flusher_ = NULL; |
| } |
| } |
| |
| |
| static inline HeapObject* ShortCircuitConsString(Object** p) { |
| // Optimization: If the heap object pointed to by p is a non-symbol |
| // cons string whose right substring is HEAP->empty_string, update |
| // it in place to its left substring. Return the updated value. |
| // |
| // Here we assume that if we change *p, we replace it with a heap object |
| // (i.e., the left substring of a cons string is always a heap object). |
| // |
| // The check performed is: |
| // object->IsConsString() && !object->IsSymbol() && |
| // (ConsString::cast(object)->second() == HEAP->empty_string()) |
| // except the maps for the object and its possible substrings might be |
| // marked. |
| HeapObject* object = HeapObject::cast(*p); |
| if (!FLAG_clever_optimizations) return object; |
| Map* map = object->map(); |
| InstanceType type = map->instance_type(); |
| if ((type & kShortcutTypeMask) != kShortcutTypeTag) return object; |
| |
| Object* second = reinterpret_cast<ConsString*>(object)->unchecked_second(); |
| Heap* heap = map->GetHeap(); |
| if (second != heap->empty_string()) { |
| return object; |
| } |
| |
| // Since we don't have the object's start, it is impossible to update the |
| // page dirty marks. Therefore, we only replace the string with its left |
| // substring when page dirty marks do not change. |
| Object* first = reinterpret_cast<ConsString*>(object)->unchecked_first(); |
| if (!heap->InNewSpace(object) && heap->InNewSpace(first)) return object; |
| |
| *p = first; |
| return HeapObject::cast(first); |
| } |
| |
| |
| class StaticMarkingVisitor : public StaticVisitorBase { |
| public: |
| static inline void IterateBody(Map* map, HeapObject* obj) { |
| table_.GetVisitor(map)(map, obj); |
| } |
| |
| static void Initialize() { |
| table_.Register(kVisitShortcutCandidate, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| ConsString::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitConsString, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| ConsString::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitSlicedString, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| SlicedString::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitFixedArray, |
| &FlexibleBodyVisitor<StaticMarkingVisitor, |
| FixedArray::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitGlobalContext, &VisitGlobalContext); |
| |
| table_.Register(kVisitFixedDoubleArray, DataObjectVisitor::Visit); |
| |
| table_.Register(kVisitByteArray, &DataObjectVisitor::Visit); |
| table_.Register(kVisitFreeSpace, &DataObjectVisitor::Visit); |
| table_.Register(kVisitSeqAsciiString, &DataObjectVisitor::Visit); |
| table_.Register(kVisitSeqTwoByteString, &DataObjectVisitor::Visit); |
| |
| table_.Register(kVisitJSWeakMap, &VisitJSWeakMap); |
| |
| table_.Register(kVisitOddball, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| Oddball::BodyDescriptor, |
| void>::Visit); |
| table_.Register(kVisitMap, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| Map::BodyDescriptor, |
| void>::Visit); |
| |
| table_.Register(kVisitCode, &VisitCode); |
| |
| table_.Register(kVisitSharedFunctionInfo, |
| &VisitSharedFunctionInfoAndFlushCode); |
| |
| table_.Register(kVisitJSFunction, |
| &VisitJSFunctionAndFlushCode); |
| |
| table_.Register(kVisitJSRegExp, |
| &VisitRegExpAndFlushCode); |
| |
| table_.Register(kVisitPropertyCell, |
| &FixedBodyVisitor<StaticMarkingVisitor, |
| JSGlobalPropertyCell::BodyDescriptor, |
| void>::Visit); |
| |
| table_.RegisterSpecializations<DataObjectVisitor, |
| kVisitDataObject, |
| kVisitDataObjectGeneric>(); |
| |
| table_.RegisterSpecializations<JSObjectVisitor, |
| kVisitJSObject, |
| kVisitJSObjectGeneric>(); |
| |
| table_.RegisterSpecializations<StructObjectVisitor, |
| kVisitStruct, |
| kVisitStructGeneric>(); |
| } |
| |
| INLINE(static void VisitPointer(Heap* heap, Object** p)) { |
| MarkObjectByPointer(heap->mark_compact_collector(), p, p); |
| } |
| |
| INLINE(static void VisitPointers(Heap* heap, Object** start, Object** end)) { |
| // Mark all objects pointed to in [start, end). |
| const int kMinRangeForMarkingRecursion = 64; |
| if (end - start >= kMinRangeForMarkingRecursion) { |
| if (VisitUnmarkedObjects(heap, 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, start, p); |
| } |
| } |
| |
| static void VisitGlobalPropertyCell(Heap* heap, RelocInfo* rinfo) { |
| ASSERT(rinfo->rmode() == RelocInfo::GLOBAL_PROPERTY_CELL); |
| JSGlobalPropertyCell* cell = |
| JSGlobalPropertyCell::cast(rinfo->target_cell()); |
| MarkBit mark = Marking::MarkBitFrom(cell); |
| heap->mark_compact_collector()->MarkObject(cell, mark); |
| } |
| |
| static inline void VisitEmbeddedPointer(Heap* heap, RelocInfo* rinfo) { |
| ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT); |
| // TODO(mstarzinger): We do not short-circuit cons strings here, verify |
| // that there can be no such embedded pointers and add assertion here. |
| HeapObject* object = HeapObject::cast(rinfo->target_object()); |
| heap->mark_compact_collector()->RecordRelocSlot(rinfo, object); |
| MarkBit mark = Marking::MarkBitFrom(object); |
| heap->mark_compact_collector()->MarkObject(object, mark); |
| } |
| |
| static inline void VisitCodeTarget(Heap* heap, RelocInfo* rinfo) { |
| ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Code* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| if (FLAG_cleanup_code_caches_at_gc && target->is_inline_cache_stub() |
| && (target->ic_state() == MEGAMORPHIC || |
| heap->mark_compact_collector()->flush_monomorphic_ics_ || |
| target->ic_age() != heap->global_ic_age())) { |
| IC::Clear(rinfo->pc()); |
| target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| } |
| MarkBit code_mark = Marking::MarkBitFrom(target); |
| heap->mark_compact_collector()->MarkObject(target, code_mark); |
| heap->mark_compact_collector()->RecordRelocSlot(rinfo, target); |
| } |
| |
| static inline void VisitDebugTarget(Heap* heap, RelocInfo* rinfo) { |
| ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) && |
| rinfo->IsPatchedReturnSequence()) || |
| (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence())); |
| Code* target = Code::GetCodeFromTargetAddress(rinfo->call_address()); |
| MarkBit code_mark = Marking::MarkBitFrom(target); |
| heap->mark_compact_collector()->MarkObject(target, code_mark); |
| heap->mark_compact_collector()->RecordRelocSlot(rinfo, target); |
| } |
| |
| // Mark object pointed to by p. |
| INLINE(static void MarkObjectByPointer(MarkCompactCollector* collector, |
| Object** anchor_slot, |
| Object** p)) { |
| if (!(*p)->IsHeapObject()) return; |
| HeapObject* object = ShortCircuitConsString(p); |
| collector->RecordSlot(anchor_slot, p, object); |
| MarkBit mark = Marking::MarkBitFrom(object); |
| collector->MarkObject(object, mark); |
| } |
| |
| |
| // Visit an unmarked object. |
| INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector, |
| HeapObject* obj)) { |
| #ifdef DEBUG |
| ASSERT(Isolate::Current()->heap()->Contains(obj)); |
| ASSERT(!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). |
| static inline bool VisitUnmarkedObjects(Heap* heap, |
| 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(start, p, o); |
| HeapObject* obj = HeapObject::cast(o); |
| MarkBit mark = Marking::MarkBitFrom(obj); |
| if (mark.Get()) continue; |
| VisitUnmarkedObject(collector, obj); |
| } |
| return true; |
| } |
| |
| static inline void VisitExternalReference(Address* p) { } |
| static inline void VisitExternalReference(RelocInfo* rinfo) { } |
| static inline void VisitRuntimeEntry(RelocInfo* rinfo) { } |
| |
| private: |
| class DataObjectVisitor { |
| public: |
| template<int size> |
| static void VisitSpecialized(Map* map, HeapObject* object) { |
| } |
| |
| static void Visit(Map* map, HeapObject* object) { |
| } |
| }; |
| |
| typedef FlexibleBodyVisitor<StaticMarkingVisitor, |
| JSObject::BodyDescriptor, |
| void> JSObjectVisitor; |
| |
| typedef FlexibleBodyVisitor<StaticMarkingVisitor, |
| StructBodyDescriptor, |
| void> StructObjectVisitor; |
| |
| static void VisitJSWeakMap(Map* map, HeapObject* object) { |
| MarkCompactCollector* collector = map->GetHeap()->mark_compact_collector(); |
| JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(object); |
| |
| // Enqueue weak map in linked list of encountered weak maps. |
| if (weak_map->next() == Smi::FromInt(0)) { |
| weak_map->set_next(collector->encountered_weak_maps()); |
| collector->set_encountered_weak_maps(weak_map); |
| } |
| |
| // Skip visiting the backing hash table containing the mappings. |
| int object_size = JSWeakMap::BodyDescriptor::SizeOf(map, object); |
| BodyVisitorBase<StaticMarkingVisitor>::IteratePointers( |
| map->GetHeap(), |
| object, |
| JSWeakMap::BodyDescriptor::kStartOffset, |
| JSWeakMap::kTableOffset); |
| BodyVisitorBase<StaticMarkingVisitor>::IteratePointers( |
| map->GetHeap(), |
| object, |
| JSWeakMap::kTableOffset + kPointerSize, |
| object_size); |
| |
| // Mark the backing hash table without pushing it on the marking stack. |
| Object* table_object = weak_map->table(); |
| if (!table_object->IsHashTable()) return; |
| ObjectHashTable* table = ObjectHashTable::cast(table_object); |
| Object** table_slot = |
| HeapObject::RawField(weak_map, JSWeakMap::kTableOffset); |
| MarkBit table_mark = Marking::MarkBitFrom(table); |
| collector->RecordSlot(table_slot, table_slot, table); |
| if (!table_mark.Get()) collector->SetMark(table, table_mark); |
| // Recording the map slot can be skipped, because maps are not compacted. |
| collector->MarkObject(table->map(), Marking::MarkBitFrom(table->map())); |
| ASSERT(MarkCompactCollector::IsMarked(table->map())); |
| } |
| |
| static void VisitCode(Map* map, HeapObject* object) { |
| Heap* heap = map->GetHeap(); |
| Code* code = reinterpret_cast<Code*>(object); |
| if (FLAG_cleanup_code_caches_at_gc) { |
| code->ClearTypeFeedbackCells(heap); |
| } |
| code->CodeIterateBody<StaticMarkingVisitor>(heap); |
| } |
| |
| // Code flushing support. |
| |
| // How many collections newly compiled code object will survive before being |
| // flushed. |
| static const int kCodeAgeThreshold = 5; |
| |
| static const int kRegExpCodeThreshold = 5; |
| |
| inline static bool HasSourceCode(Heap* heap, SharedFunctionInfo* info) { |
| Object* undefined = heap->undefined_value(); |
| return (info->script() != undefined) && |
| (reinterpret_cast<Script*>(info->script())->source() != undefined); |
| } |
| |
| |
| inline static bool IsCompiled(JSFunction* function) { |
| return function->code() != |
| function->GetIsolate()->builtins()->builtin(Builtins::kLazyCompile); |
| } |
| |
| inline static bool IsCompiled(SharedFunctionInfo* function) { |
| return function->code() != |
| function->GetIsolate()->builtins()->builtin(Builtins::kLazyCompile); |
| } |
| |
| inline static bool IsFlushable(Heap* heap, JSFunction* function) { |
| SharedFunctionInfo* shared_info = function->unchecked_shared(); |
| |
| // Code is either on stack, in compilation cache or referenced |
| // by optimized version of function. |
| MarkBit code_mark = Marking::MarkBitFrom(function->code()); |
| if (code_mark.Get()) { |
| if (!Marking::MarkBitFrom(shared_info).Get()) { |
| shared_info->set_code_age(0); |
| } |
| return false; |
| } |
| |
| // We do not flush code for optimized functions. |
| if (function->code() != shared_info->code()) { |
| return false; |
| } |
| |
| return IsFlushable(heap, shared_info); |
| } |
| |
| inline static bool IsFlushable(Heap* heap, SharedFunctionInfo* shared_info) { |
| // Code is either on stack, in compilation cache or referenced |
| // by optimized version of function. |
| MarkBit code_mark = |
| Marking::MarkBitFrom(shared_info->code()); |
| if (code_mark.Get()) { |
| return false; |
| } |
| |
| // The function must be compiled and have the source code available, |
| // to be able to recompile it in case we need the function again. |
| if (!(shared_info->is_compiled() && HasSourceCode(heap, shared_info))) { |
| return false; |
| } |
| |
| // We never flush code for Api functions. |
| Object* function_data = shared_info->function_data(); |
| if (function_data->IsFunctionTemplateInfo()) { |
| return false; |
| } |
| |
| // Only flush code for functions. |
| if (shared_info->code()->kind() != Code::FUNCTION) { |
| return false; |
| } |
| |
| // Function must be lazy compilable. |
| if (!shared_info->allows_lazy_compilation()) { |
| return false; |
| } |
| |
| // If this is a full script wrapped in a function we do no flush the code. |
| if (shared_info->is_toplevel()) { |
| return false; |
| } |
| |
| // Age this shared function info. |
| if (shared_info->code_age() < kCodeAgeThreshold) { |
| shared_info->set_code_age(shared_info->code_age() + 1); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| |
| static bool FlushCodeForFunction(Heap* heap, JSFunction* function) { |
| if (!IsFlushable(heap, function)) return false; |
| |
| // This function's code looks flushable. But we have to postpone the |
| // decision until we see all functions that point to the same |
| // SharedFunctionInfo because some of them might be optimized. |
| // That would make the nonoptimized version of the code nonflushable, |
| // because it is required for bailing out from optimized code. |
| heap->mark_compact_collector()->code_flusher()->AddCandidate(function); |
| return true; |
| } |
| |
| static inline bool IsValidNotBuiltinContext(Object* ctx) { |
| return ctx->IsContext() && |
| !Context::cast(ctx)->global()->IsJSBuiltinsObject(); |
| } |
| |
| |
| static void VisitSharedFunctionInfoGeneric(Map* map, HeapObject* object) { |
| SharedFunctionInfo::cast(object)->BeforeVisitingPointers(); |
| |
| FixedBodyVisitor<StaticMarkingVisitor, |
| SharedFunctionInfo::BodyDescriptor, |
| void>::Visit(map, object); |
| } |
| |
| |
| static void UpdateRegExpCodeAgeAndFlush(Heap* heap, |
| JSRegExp* re, |
| bool is_ascii) { |
| // 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->TypeTagUnchecked() != JSRegExp::IRREGEXP) return; |
| |
| Object* code = re->DataAtUnchecked(JSRegExp::code_index(is_ascii)); |
| 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->SetDataAtUnchecked(JSRegExp::saved_code_index(is_ascii), |
| code, |
| heap); |
| |
| // 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_ascii); |
| heap->mark_compact_collector()-> |
| RecordSlot(slot, slot, code); |
| |
| // Set a number in the 0-255 range to guarantee no smi overflow. |
| re->SetDataAtUnchecked(JSRegExp::code_index(is_ascii), |
| Smi::FromInt(heap->sweep_generation() & 0xff), |
| heap); |
| } 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->sweep_generation() - kRegExpCodeThreshold) & 0xff)) { |
| re->SetDataAtUnchecked(JSRegExp::code_index(is_ascii), |
| Smi::FromInt(JSRegExp::kUninitializedValue), |
| heap); |
| re->SetDataAtUnchecked(JSRegExp::saved_code_index(is_ascii), |
| Smi::FromInt(JSRegExp::kUninitializedValue), |
| heap); |
| } |
| } |
| } |
| |
| |
| // 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()) { |
| VisitJSRegExpFields(map, object); |
| return; |
| } |
| JSRegExp* re = reinterpret_cast<JSRegExp*>(object); |
| // Flush code or set age on both ASCII and two byte code. |
| UpdateRegExpCodeAgeAndFlush(heap, re, true); |
| UpdateRegExpCodeAgeAndFlush(heap, re, false); |
| // Visit the fields of the RegExp, including the updated FixedArray. |
| VisitJSRegExpFields(map, object); |
| } |
| |
| |
| static void VisitSharedFunctionInfoAndFlushCode(Map* map, |
| HeapObject* object) { |
| Heap* heap = map->GetHeap(); |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(object); |
| if (shared->ic_age() != heap->global_ic_age()) { |
| shared->ResetForNewContext(heap->global_ic_age()); |
| } |
| |
| MarkCompactCollector* collector = map->GetHeap()->mark_compact_collector(); |
| if (!collector->is_code_flushing_enabled()) { |
| VisitSharedFunctionInfoGeneric(map, object); |
| return; |
| } |
| VisitSharedFunctionInfoAndFlushCodeGeneric(map, object, false); |
| } |
| |
| |
| static void VisitSharedFunctionInfoAndFlushCodeGeneric( |
| Map* map, HeapObject* object, bool known_flush_code_candidate) { |
| Heap* heap = map->GetHeap(); |
| SharedFunctionInfo* shared = reinterpret_cast<SharedFunctionInfo*>(object); |
| |
| shared->BeforeVisitingPointers(); |
| |
| if (!known_flush_code_candidate) { |
| known_flush_code_candidate = IsFlushable(heap, shared); |
| if (known_flush_code_candidate) { |
| heap->mark_compact_collector()->code_flusher()->AddCandidate(shared); |
| } |
| } |
| |
| VisitSharedFunctionInfoFields(heap, object, known_flush_code_candidate); |
| } |
| |
| |
| static void VisitCodeEntry(Heap* heap, Address entry_address) { |
| Code* code = Code::cast(Code::GetObjectFromEntryAddress(entry_address)); |
| MarkBit mark = Marking::MarkBitFrom(code); |
| heap->mark_compact_collector()->MarkObject(code, mark); |
| heap->mark_compact_collector()-> |
| RecordCodeEntrySlot(entry_address, code); |
| } |
| |
| static void VisitGlobalContext(Map* map, HeapObject* object) { |
| FixedBodyVisitor<StaticMarkingVisitor, |
| Context::MarkCompactBodyDescriptor, |
| void>::Visit(map, object); |
| |
| MarkCompactCollector* collector = map->GetHeap()->mark_compact_collector(); |
| for (int idx = Context::FIRST_WEAK_SLOT; |
| idx < Context::GLOBAL_CONTEXT_SLOTS; |
| ++idx) { |
| Object** slot = |
| HeapObject::RawField(object, FixedArray::OffsetOfElementAt(idx)); |
| collector->RecordSlot(slot, slot, *slot); |
| } |
| } |
| |
| static void VisitJSFunctionAndFlushCode(Map* map, HeapObject* object) { |
| Heap* heap = map->GetHeap(); |
| MarkCompactCollector* collector = heap->mark_compact_collector(); |
| if (!collector->is_code_flushing_enabled()) { |
| VisitJSFunction(map, object); |
| return; |
| } |
| |
| JSFunction* jsfunction = reinterpret_cast<JSFunction*>(object); |
| // The function must have a valid context and not be a builtin. |
| bool flush_code_candidate = false; |
| if (IsValidNotBuiltinContext(jsfunction->unchecked_context())) { |
| flush_code_candidate = FlushCodeForFunction(heap, jsfunction); |
| } |
| |
| if (!flush_code_candidate) { |
| Code* code = jsfunction->shared()->code(); |
| MarkBit code_mark = Marking::MarkBitFrom(code); |
| collector->MarkObject(code, code_mark); |
| |
| if (jsfunction->code()->kind() == Code::OPTIMIZED_FUNCTION) { |
| collector->MarkInlinedFunctionsCode(jsfunction->code()); |
| } |
| } |
| |
| VisitJSFunctionFields(map, |
| reinterpret_cast<JSFunction*>(object), |
| flush_code_candidate); |
| } |
| |
| |
| static void VisitJSFunction(Map* map, HeapObject* object) { |
| VisitJSFunctionFields(map, |
| reinterpret_cast<JSFunction*>(object), |
| false); |
| } |
| |
| |
| #define SLOT_ADDR(obj, offset) \ |
| reinterpret_cast<Object**>((obj)->address() + offset) |
| |
| |
| static inline void VisitJSFunctionFields(Map* map, |
| JSFunction* object, |
| bool flush_code_candidate) { |
| Heap* heap = map->GetHeap(); |
| |
| VisitPointers(heap, |
| HeapObject::RawField(object, JSFunction::kPropertiesOffset), |
| HeapObject::RawField(object, JSFunction::kCodeEntryOffset)); |
| |
| if (!flush_code_candidate) { |
| VisitCodeEntry(heap, object->address() + JSFunction::kCodeEntryOffset); |
| } else { |
| // Don't visit code object. |
| |
| // Visit shared function info to avoid double checking of it's |
| // flushability. |
| SharedFunctionInfo* shared_info = object->unchecked_shared(); |
| MarkBit shared_info_mark = Marking::MarkBitFrom(shared_info); |
| if (!shared_info_mark.Get()) { |
| Map* shared_info_map = shared_info->map(); |
| MarkBit shared_info_map_mark = |
| Marking::MarkBitFrom(shared_info_map); |
| heap->mark_compact_collector()->SetMark(shared_info, shared_info_mark); |
| heap->mark_compact_collector()->MarkObject(shared_info_map, |
| shared_info_map_mark); |
| VisitSharedFunctionInfoAndFlushCodeGeneric(shared_info_map, |
| shared_info, |
| true); |
| } |
| } |
| |
| VisitPointers( |
| heap, |
| HeapObject::RawField(object, |
| JSFunction::kCodeEntryOffset + kPointerSize), |
| HeapObject::RawField(object, |
| JSFunction::kNonWeakFieldsEndOffset)); |
| } |
| |
| static inline void VisitJSRegExpFields(Map* map, |
| HeapObject* object) { |
| int last_property_offset = |
| JSRegExp::kSize + kPointerSize * map->inobject_properties(); |
| VisitPointers(map->GetHeap(), |
| SLOT_ADDR(object, JSRegExp::kPropertiesOffset), |
| SLOT_ADDR(object, last_property_offset)); |
| } |
| |
| |
| static void VisitSharedFunctionInfoFields(Heap* heap, |
| HeapObject* object, |
| bool flush_code_candidate) { |
| VisitPointer(heap, SLOT_ADDR(object, SharedFunctionInfo::kNameOffset)); |
| |
| if (!flush_code_candidate) { |
| VisitPointer(heap, SLOT_ADDR(object, SharedFunctionInfo::kCodeOffset)); |
| } |
| |
| VisitPointers(heap, |
| SLOT_ADDR(object, SharedFunctionInfo::kOptimizedCodeMapOffset), |
| SLOT_ADDR(object, SharedFunctionInfo::kSize)); |
| } |
| |
| #undef SLOT_ADDR |
| |
| typedef void (*Callback)(Map* map, HeapObject* object); |
| |
| static VisitorDispatchTable<Callback> table_; |
| }; |
| |
| |
| VisitorDispatchTable<StaticMarkingVisitor::Callback> |
| StaticMarkingVisitor::table_; |
| |
| |
| class MarkingVisitor : public ObjectVisitor { |
| public: |
| explicit MarkingVisitor(Heap* heap) : heap_(heap) { } |
| |
| void VisitPointer(Object** p) { |
| StaticMarkingVisitor::VisitPointer(heap_, p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| StaticMarkingVisitor::VisitPointers(heap_, start, end); |
| } |
| |
| private: |
| Heap* heap_; |
| }; |
| |
| |
| 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) { |
| for (Object** p = start; p < end; p++) VisitPointer(p); |
| } |
| |
| void VisitPointer(Object** slot) { |
| 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::MarkInlinedFunctionsCode(Code* code) { |
| // For optimized functions we should retain both non-optimized version |
| // of it's code and non-optimized version of all inlined functions. |
| // This is required to support bailing out from inlined code. |
| DeoptimizationInputData* data = |
| DeoptimizationInputData::cast(code->deoptimization_data()); |
| |
| FixedArray* literals = data->LiteralArray(); |
| |
| for (int i = 0, count = data->InlinedFunctionCount()->value(); |
| i < count; |
| i++) { |
| JSFunction* inlined = JSFunction::cast(literals->get(i)); |
| Code* inlined_code = inlined->shared()->code(); |
| MarkBit inlined_code_mark = Marking::MarkBitFrom(inlined_code); |
| MarkObject(inlined_code, inlined_code_mark); |
| } |
| } |
| |
| |
| 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()) { |
| MarkInlinedFunctionsCode(frame->LookupCode()); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::PrepareForCodeFlushing() { |
| ASSERT(heap() == Isolate::Current()->heap()); |
| |
| // TODO(1609) Currently incremental marker does not support code flushing. |
| if (!FLAG_flush_code || was_marked_incrementally_) { |
| EnableCodeFlushing(false); |
| return; |
| } |
| |
| #ifdef ENABLE_DEBUGGER_SUPPORT |
| if (heap()->isolate()->debug()->IsLoaded() || |
| heap()->isolate()->debug()->has_break_points()) { |
| EnableCodeFlushing(false); |
| return; |
| } |
| #endif |
| |
| EnableCodeFlushing(true); |
| |
| // 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. |
| ASSERT(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) { |
| MarkObjectByPointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) MarkObjectByPointer(p); |
| } |
| |
| private: |
| void MarkObjectByPointer(Object** p) { |
| if (!(*p)->IsHeapObject()) return; |
| |
| // Replace flat cons strings in place. |
| HeapObject* object = ShortCircuitConsString(p); |
| MarkBit mark_bit = Marking::MarkBitFrom(object); |
| if (mark_bit.Get()) 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); |
| StaticMarkingVisitor::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 symbol table. |
| class SymbolTableCleaner : public ObjectVisitor { |
| public: |
| explicit SymbolTableCleaner(Heap* heap) |
| : heap_(heap), pointers_removed_(0) { } |
| |
| virtual void VisitPointers(Object** start, Object** end) { |
| // Visit all HeapObject pointers in [start, end). |
| for (Object** p = start; p < end; p++) { |
| Object* o = *p; |
| if (o->IsHeapObject() && |
| !Marking::MarkBitFrom(HeapObject::cast(o)).Get()) { |
| // Check if the symbol being pruned is an external symbol. We need to |
| // delete the associated external data as this symbol is going away. |
| |
| // Since no objects have yet been moved we can safely access the map of |
| // the object. |
| if (o->IsExternalString()) { |
| heap_->FinalizeExternalString(String::cast(*p)); |
| } |
| // Set the entry to the_hole_value (as deleted). |
| *p = heap_->the_hole_value(); |
| pointers_removed_++; |
| } |
| } |
| } |
| |
| int PointersRemoved() { |
| return pointers_removed_; |
| } |
| |
| private: |
| Heap* heap_; |
| int pointers_removed_; |
| }; |
| |
| |
| // Implementation of WeakObjectRetainer for mark compact GCs. All marked objects |
| // are retained. |
| class MarkCompactWeakObjectRetainer : public WeakObjectRetainer { |
| public: |
| virtual Object* RetainAs(Object* object) { |
| if (Marking::MarkBitFrom(HeapObject::cast(object)).Get()) { |
| return object; |
| } else { |
| return NULL; |
| } |
| } |
| }; |
| |
| |
| void MarkCompactCollector::ProcessNewlyMarkedObject(HeapObject* object) { |
| ASSERT(IsMarked(object)); |
| ASSERT(HEAP->Contains(object)); |
| if (object->IsMap()) { |
| Map* map = Map::cast(object); |
| heap_->ClearCacheOnMap(map); |
| |
| // When map collection is enabled we have to mark through map's transitions |
| // in a special way to make transition links weak. Only maps for subclasses |
| // of JSReceiver can have transitions. |
| STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE); |
| if (FLAG_collect_maps && map->instance_type() >= FIRST_JS_RECEIVER_TYPE) { |
| marker_.MarkMapContents(map); |
| } else { |
| marking_deque_.PushBlack(map); |
| } |
| } else { |
| marking_deque_.PushBlack(object); |
| } |
| } |
| |
| |
| // Force instantiation of template instances. |
| template void Marker<IncrementalMarking>::MarkMapContents(Map* map); |
| template void Marker<MarkCompactCollector>::MarkMapContents(Map* map); |
| |
| |
| template <class T> |
| void Marker<T>::MarkMapContents(Map* map) { |
| // Mark prototype transitions array but don't push it into marking stack. |
| // This will make references from it weak. We will clean dead prototype |
| // transitions in ClearNonLiveTransitions. |
| Object** proto_trans_slot = |
| HeapObject::RawField(map, Map::kPrototypeTransitionsOrBackPointerOffset); |
| HeapObject* prototype_transitions = HeapObject::cast(*proto_trans_slot); |
| if (prototype_transitions->IsFixedArray()) { |
| mark_compact_collector()->RecordSlot(proto_trans_slot, |
| proto_trans_slot, |
| prototype_transitions); |
| MarkBit mark = Marking::MarkBitFrom(prototype_transitions); |
| if (!mark.Get()) { |
| mark.Set(); |
| MemoryChunk::IncrementLiveBytesFromGC(prototype_transitions->address(), |
| prototype_transitions->Size()); |
| } |
| } |
| |
| // Make sure that the back pointer stored either in the map itself or inside |
| // its prototype transitions array is marked. Treat pointers in the descriptor |
| // array as weak and also mark that array to prevent visiting it later. |
| base_marker()->MarkObjectAndPush(HeapObject::cast(map->GetBackPointer())); |
| |
| Object** descriptor_array_slot = |
| HeapObject::RawField(map, Map::kInstanceDescriptorsOrBitField3Offset); |
| Object* descriptor_array = *descriptor_array_slot; |
| if (!descriptor_array->IsSmi()) { |
| MarkDescriptorArray(reinterpret_cast<DescriptorArray*>(descriptor_array)); |
| } |
| |
| // Mark the Object* fields of the Map. Since the descriptor array has been |
| // marked already, it is fine that one of these fields contains a pointer |
| // to it. But make sure to skip back pointer and prototype transitions. |
| STATIC_ASSERT(Map::kPointerFieldsEndOffset == |
| Map::kPrototypeTransitionsOrBackPointerOffset + kPointerSize); |
| Object** start_slot = HeapObject::RawField( |
| map, Map::kPointerFieldsBeginOffset); |
| Object** end_slot = HeapObject::RawField( |
| map, Map::kPrototypeTransitionsOrBackPointerOffset); |
| for (Object** slot = start_slot; slot < end_slot; slot++) { |
| Object* obj = *slot; |
| if (!obj->NonFailureIsHeapObject()) continue; |
| mark_compact_collector()->RecordSlot(start_slot, slot, obj); |
| base_marker()->MarkObjectAndPush(reinterpret_cast<HeapObject*>(obj)); |
| } |
| } |
| |
| |
| template <class T> |
| void Marker<T>::MarkDescriptorArray(DescriptorArray* descriptors) { |
| // Empty descriptor array is marked as a root before any maps are marked. |
| ASSERT(descriptors != descriptors->GetHeap()->empty_descriptor_array()); |
| |
| if (!base_marker()->MarkObjectWithoutPush(descriptors)) return; |
| Object** descriptor_start = descriptors->data_start(); |
| |
| // Since the descriptor array itself is not pushed for scanning, all fields |
| // that point to objects manually have to be pushed, marked, and their slots |
| // recorded. |
| if (descriptors->HasEnumCache()) { |
| Object** enum_cache_slot = descriptors->GetEnumCacheSlot(); |
| Object* enum_cache = *enum_cache_slot; |
| base_marker()->MarkObjectAndPush( |
| reinterpret_cast<HeapObject*>(enum_cache)); |
| mark_compact_collector()->RecordSlot(descriptor_start, |
| enum_cache_slot, |
| enum_cache); |
| } |
| |
| if (descriptors->elements_transition_map() != NULL) { |
| Object** transitions_slot = descriptors->GetTransitionsSlot(); |
| Object* transitions = *transitions_slot; |
| mark_compact_collector()->RecordSlot(descriptor_start, |
| transitions_slot, |
| transitions); |
| } |
| |
| // If the descriptor contains a transition (value is a Map), we don't mark the |
| // value as live. It might be removed by ClearNonLiveTransitions later. |
| for (int i = 0; i < descriptors->number_of_descriptors(); ++i) { |
| Object** key_slot = descriptors->GetKeySlot(i); |
| Object* key = *key_slot; |
| if (key->IsHeapObject()) { |
| base_marker()->MarkObjectAndPush(reinterpret_cast<HeapObject*>(key)); |
| mark_compact_collector()->RecordSlot(descriptor_start, key_slot, key); |
| } |
| |
| Object** value_slot = descriptors->GetValueSlot(i); |
| if (!(*value_slot)->IsHeapObject()) continue; |
| HeapObject* value = HeapObject::cast(*value_slot); |
| |
| mark_compact_collector()->RecordSlot(descriptor_start, |
| value_slot, |
| value); |
| |
| PropertyDetails details(descriptors->GetDetails(i)); |
| |
| switch (details.type()) { |
| case NORMAL: |
| case FIELD: |
| case CONSTANT_FUNCTION: |
| case HANDLER: |
| case INTERCEPTOR: |
| base_marker()->MarkObjectAndPush(value); |
| break; |
| case CALLBACKS: |
| if (!value->IsAccessorPair()) { |
| base_marker()->MarkObjectAndPush(value); |
| } else if (base_marker()->MarkObjectWithoutPush(value)) { |
| AccessorPair* accessors = AccessorPair::cast(value); |
| MarkAccessorPairSlot(accessors, AccessorPair::kGetterOffset); |
| MarkAccessorPairSlot(accessors, AccessorPair::kSetterOffset); |
| } |
| break; |
| case MAP_TRANSITION: |
| case CONSTANT_TRANSITION: |
| break; |
| case NONEXISTENT: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| } |
| |
| |
| template <class T> |
| void Marker<T>::MarkAccessorPairSlot(AccessorPair* accessors, int offset) { |
| Object** slot = HeapObject::RawField(accessors, offset); |
| HeapObject* accessor = HeapObject::cast(*slot); |
| if (accessor->IsMap()) return; |
| mark_compact_collector()->RecordSlot(slot, slot, accessor); |
| base_marker()->MarkObjectAndPush(accessor); |
| } |
| |
| |
| // 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> |
| static void DiscoverGreyObjectsWithIterator(Heap* heap, |
| MarkingDeque* marking_deque, |
| 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. |
| ASSERT(!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); |
| MemoryChunk::IncrementLiveBytesFromGC(object->address(), object->Size()); |
| marking_deque->PushBlack(object); |
| if (marking_deque->IsFull()) return; |
| } |
| } |
| } |
| |
| |
| static inline int MarkWordToObjectStarts(uint32_t mark_bits, int* starts); |
| |
| |
| static void DiscoverGreyObjectsOnPage(MarkingDeque* marking_deque, Page* p) { |
| ASSERT(!marking_deque->IsFull()); |
| ASSERT(strcmp(Marking::kWhiteBitPattern, "00") == 0); |
| ASSERT(strcmp(Marking::kBlackBitPattern, "10") == 0); |
| ASSERT(strcmp(Marking::kGreyBitPattern, "11") == 0); |
| ASSERT(strcmp(Marking::kImpossibleBitPattern, "01") == 0); |
| |
| MarkBit::CellType* cells = p->markbits()->cells(); |
| |
| int last_cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(p->area_end()))); |
| |
| Address cell_base = p->area_start(); |
| int cell_index = Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(cell_base))); |
| |
| |
| for (; |
| cell_index < last_cell_index; |
| cell_index++, cell_base += 32 * kPointerSize) { |
| ASSERT((unsigned)cell_index == |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(cell_base)))); |
| |
| const MarkBit::CellType current_cell = cells[cell_index]; |
| if (current_cell == 0) continue; |
| |
| const MarkBit::CellType next_cell = cells[cell_index + 1]; |
| MarkBit::CellType grey_objects = current_cell & |
| ((current_cell >> 1) | (next_cell << (Bitmap::kBitsPerCell - 1))); |
| |
| int offset = 0; |
| while (grey_objects != 0) { |
| int trailing_zeros = CompilerIntrinsics::CountTrailingZeros(grey_objects); |
| grey_objects >>= trailing_zeros; |
| offset += trailing_zeros; |
| MarkBit markbit(&cells[cell_index], 1 << offset, false); |
| ASSERT(Marking::IsGrey(markbit)); |
| Marking::GreyToBlack(markbit); |
| Address addr = cell_base + offset * kPointerSize; |
| HeapObject* object = HeapObject::FromAddress(addr); |
| MemoryChunk::IncrementLiveBytesFromGC(object->address(), object->Size()); |
| marking_deque->PushBlack(object); |
| if (marking_deque->IsFull()) return; |
| offset += 2; |
| grey_objects >>= 2; |
| } |
| |
| grey_objects >>= (Bitmap::kBitsPerCell - 1); |
| } |
| } |
| |
| |
| static void DiscoverGreyObjectsInSpace(Heap* heap, |
| MarkingDeque* marking_deque, |
| PagedSpace* space) { |
| if (!space->was_swept_conservatively()) { |
| HeapObjectIterator it(space); |
| DiscoverGreyObjectsWithIterator(heap, marking_deque, &it); |
| } else { |
| PageIterator it(space); |
| while (it.has_next()) { |
| Page* p = it.next(); |
| DiscoverGreyObjectsOnPage(marking_deque, p); |
| 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 !mark.Get(); |
| } |
| |
| |
| void MarkCompactCollector::MarkSymbolTable() { |
| SymbolTable* symbol_table = heap()->symbol_table(); |
| // Mark the symbol table itself. |
| MarkBit symbol_table_mark = Marking::MarkBitFrom(symbol_table); |
| SetMark(symbol_table, symbol_table_mark); |
| // Explicitly mark the prefix. |
| MarkingVisitor marker(heap()); |
| symbol_table->IteratePrefix(&marker); |
| ProcessMarkingDeque(); |
| } |
| |
| |
| 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 symbol table specially. |
| MarkSymbolTable(); |
| |
| // There may be overflowed objects in the heap. Visit them now. |
| while (marking_deque_.overflowed()) { |
| RefillMarkingDeque(); |
| EmptyMarkingDeque(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkObjectGroups() { |
| List<ObjectGroup*>* object_groups = |
| heap()->isolate()->global_handles()->object_groups(); |
| |
| int last = 0; |
| for (int i = 0; i < object_groups->length(); i++) { |
| ObjectGroup* entry = object_groups->at(i); |
| ASSERT(entry != NULL); |
| |
| Object*** objects = entry->objects_; |
| bool group_marked = false; |
| for (size_t j = 0; j < entry->length_; j++) { |
| Object* object = *objects[j]; |
| if (object->IsHeapObject()) { |
| HeapObject* heap_object = HeapObject::cast(object); |
| MarkBit mark = Marking::MarkBitFrom(heap_object); |
| if (mark.Get()) { |
| group_marked = true; |
| break; |
| } |
| } |
| } |
| |
| if (!group_marked) { |
| (*object_groups)[last++] = entry; |
| continue; |
| } |
| |
| // An object in the group is marked, so mark as grey all white heap |
| // objects in the group. |
| for (size_t j = 0; j < entry->length_; ++j) { |
| Object* object = *objects[j]; |
| if (object->IsHeapObject()) { |
| HeapObject* heap_object = HeapObject::cast(object); |
| MarkBit mark = Marking::MarkBitFrom(heap_object); |
| MarkObject(heap_object, mark); |
| } |
| } |
| |
| // Once the entire group has been colored grey, set the object group |
| // to NULL so it won't be processed again. |
| entry->Dispose(); |
| object_groups->at(i) = NULL; |
| } |
| object_groups->Rewind(last); |
| } |
| |
| |
| void MarkCompactCollector::MarkImplicitRefGroups() { |
| List<ImplicitRefGroup*>* ref_groups = |
| heap()->isolate()->global_handles()->implicit_ref_groups(); |
| |
| int last = 0; |
| for (int i = 0; i < ref_groups->length(); i++) { |
| ImplicitRefGroup* entry = ref_groups->at(i); |
| ASSERT(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()) { |
| HeapObject* child = HeapObject::cast(*children[j]); |
| MarkBit mark = Marking::MarkBitFrom(child); |
| MarkObject(child, mark); |
| } |
| } |
| |
| // Once the entire group has been marked, dispose it because it's |
| // not needed anymore. |
| entry->Dispose(); |
| } |
| 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() { |
| while (!marking_deque_.IsEmpty()) { |
| while (!marking_deque_.IsEmpty()) { |
| HeapObject* object = marking_deque_.Pop(); |
| ASSERT(object->IsHeapObject()); |
| ASSERT(heap()->Contains(object)); |
| ASSERT(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| |
| Map* map = object->map(); |
| MarkBit map_mark = Marking::MarkBitFrom(map); |
| MarkObject(map, map_mark); |
| |
| StaticMarkingVisitor::IterateBody(map, object); |
| } |
| |
| // Process encountered weak maps, mark objects only reachable by those |
| // weak maps and repeat until fix-point is reached. |
| ProcessWeakMaps(); |
| } |
| } |
| |
| |
| // 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() { |
| ASSERT(marking_deque_.overflowed()); |
| |
| SemiSpaceIterator new_it(heap()->new_space()); |
| DiscoverGreyObjectsWithIterator(heap(), &marking_deque_, &new_it); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap(), |
| &marking_deque_, |
| heap()->old_pointer_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap(), |
| &marking_deque_, |
| heap()->old_data_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap(), |
| &marking_deque_, |
| heap()->code_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap(), |
| &marking_deque_, |
| heap()->map_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| DiscoverGreyObjectsInSpace(heap(), |
| &marking_deque_, |
| heap()->cell_space()); |
| if (marking_deque_.IsFull()) return; |
| |
| LargeObjectIterator lo_it(heap()->lo_space()); |
| DiscoverGreyObjectsWithIterator(heap(), |
| &marking_deque_, |
| &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(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessExternalMarking() { |
| bool work_to_do = true; |
| ASSERT(marking_deque_.IsEmpty()); |
| while (work_to_do) { |
| MarkObjectGroups(); |
| MarkImplicitRefGroups(); |
| work_to_do = !marking_deque_.IsEmpty(); |
| ProcessMarkingDeque(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::MarkLiveObjects() { |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_MARK); |
| // 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(heap()->isolate()); |
| |
| bool incremental_marking_overflowed = false; |
| IncrementalMarking* incremental_marking = heap_->incremental_marking(); |
| if (was_marked_incrementally_) { |
| // Finalize the incremental marking and check whether we had an overflow. |
| // Both markers use grey color to mark overflowed objects so |
| // non-incremental marker can deal with them as if overflow |
| // occured during normal marking. |
| // But incremental marker uses a separate marking deque |
| // so we have to explicitly copy it's overflow state. |
| incremental_marking->Finalize(); |
| incremental_marking_overflowed = |
| incremental_marking->marking_deque()->overflowed(); |
| incremental_marking->marking_deque()->ClearOverflowed(); |
| } else { |
| // Abort any pending incremental activities e.g. incremental sweeping. |
| incremental_marking->Abort(); |
| } |
| |
| #ifdef DEBUG |
| ASSERT(state_ == PREPARE_GC); |
| state_ = MARK_LIVE_OBJECTS; |
| #endif |
| // The to space contains live objects, a page in from space is used as a |
| // marking stack. |
| Address marking_deque_start = heap()->new_space()->FromSpacePageLow(); |
| Address marking_deque_end = heap()->new_space()->FromSpacePageHigh(); |
| if (FLAG_force_marking_deque_overflows) { |
| marking_deque_end = marking_deque_start + 64 * kPointerSize; |
| } |
| marking_deque_.Initialize(marking_deque_start, |
| marking_deque_end); |
| ASSERT(!marking_deque_.overflowed()); |
| |
| if (incremental_marking_overflowed) { |
| // There are overflowed objects left in the heap after incremental marking. |
| marking_deque_.SetOverflowed(); |
| } |
| |
| PrepareForCodeFlushing(); |
| |
| if (was_marked_incrementally_) { |
| // There is no write barrier on cells so we have to scan them now at the end |
| // of the incremental marking. |
| { |
| HeapObjectIterator cell_iterator(heap()->cell_space()); |
| HeapObject* cell; |
| while ((cell = cell_iterator.Next()) != NULL) { |
| ASSERT(cell->IsJSGlobalPropertyCell()); |
| if (IsMarked(cell)) { |
| int offset = JSGlobalPropertyCell::kValueOffset; |
| StaticMarkingVisitor::VisitPointer( |
| heap(), |
| reinterpret_cast<Object**>(cell->address() + offset)); |
| } |
| } |
| } |
| } |
| |
| RootMarkingVisitor root_visitor(heap()); |
| MarkRoots(&root_visitor); |
| |
| // The objects reachable from the roots are marked, yet unreachable |
| // objects are unmarked. Mark objects reachable due to host |
| // application specific logic. |
| ProcessExternalMarking(); |
| |
| // The objects reachable from the roots or object groups are marked, |
| // yet unreachable objects are unmarked. Mark objects reachable |
| // only from weak global handles. |
| // |
| // First we identify nonlive weak handles and mark them as pending |
| // destruction. |
| heap()->isolate()->global_handles()->IdentifyWeakHandles( |
| &IsUnmarkedHeapObject); |
| // Then we mark the objects and process the transitive closure. |
| heap()->isolate()->global_handles()->IterateWeakRoots(&root_visitor); |
| while (marking_deque_.overflowed()) { |
| RefillMarkingDeque(); |
| EmptyMarkingDeque(); |
| } |
| |
| // Repeat host application specific marking to mark unmarked objects |
| // reachable from the weak roots. |
| ProcessExternalMarking(); |
| |
| AfterMarking(); |
| } |
| |
| |
| void MarkCompactCollector::AfterMarking() { |
| // Object literal map caches reference symbols (cache keys) and maps |
| // (cache values). At this point still useful maps have already been |
| // marked. Mark the keys for the alive values before we process the |
| // symbol table. |
| ProcessMapCaches(); |
| |
| // Prune the symbol table removing all symbols only pointed to by the |
| // symbol table. Cannot use symbol_table() here because the symbol |
| // table is marked. |
| SymbolTable* symbol_table = heap()->symbol_table(); |
| SymbolTableCleaner v(heap()); |
| symbol_table->IterateElements(&v); |
| symbol_table->ElementsRemoved(v.PointersRemoved()); |
| heap()->external_string_table_.Iterate(&v); |
| heap()->external_string_table_.CleanUp(); |
| |
| // Process the weak references. |
| MarkCompactWeakObjectRetainer mark_compact_object_retainer; |
| heap()->ProcessWeakReferences(&mark_compact_object_retainer); |
| |
| // 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()) { |
| code_flusher_->ProcessCandidates(); |
| } |
| |
| if (!FLAG_watch_ic_patching) { |
| // Clean up dead objects from the runtime profiler. |
| heap()->isolate()->runtime_profiler()->RemoveDeadSamples(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessMapCaches() { |
| Object* raw_context = heap()->global_contexts_list_; |
| while (raw_context != heap()->undefined_value()) { |
| Context* context = reinterpret_cast<Context*>(raw_context); |
| if (IsMarked(context)) { |
| HeapObject* raw_map_cache = |
| HeapObject::cast(context->get(Context::MAP_CACHE_INDEX)); |
| // A map cache may be reachable from the stack. In this case |
| // it's already transitively marked and it's too late to clean |
| // up its parts. |
| if (!IsMarked(raw_map_cache) && |
| raw_map_cache != heap()->undefined_value()) { |
| MapCache* map_cache = reinterpret_cast<MapCache*>(raw_map_cache); |
| int existing_elements = map_cache->NumberOfElements(); |
| int used_elements = 0; |
| for (int i = MapCache::kElementsStartIndex; |
| i < map_cache->length(); |
| i += MapCache::kEntrySize) { |
| Object* raw_key = map_cache->get(i); |
| if (raw_key == heap()->undefined_value() || |
| raw_key == heap()->the_hole_value()) continue; |
| STATIC_ASSERT(MapCache::kEntrySize == 2); |
| Object* raw_map = map_cache->get(i + 1); |
| if (raw_map->IsHeapObject() && IsMarked(raw_map)) { |
| ++used_elements; |
| } else { |
| // Delete useless entries with unmarked maps. |
| ASSERT(raw_map->IsMap()); |
| map_cache->set_the_hole(i); |
| map_cache->set_the_hole(i + 1); |
| } |
| } |
| if (used_elements == 0) { |
| context->set(Context::MAP_CACHE_INDEX, heap()->undefined_value()); |
| } else { |
| // Note: we don't actually shrink the cache here to avoid |
| // extra complexity during GC. We rely on subsequent cache |
| // usages (EnsureCapacity) to do this. |
| map_cache->ElementsRemoved(existing_elements - used_elements); |
| MarkBit map_cache_markbit = Marking::MarkBitFrom(map_cache); |
| MarkObject(map_cache, map_cache_markbit); |
| } |
| } |
| } |
| // Move to next element in the list. |
| raw_context = context->get(Context::NEXT_CONTEXT_LINK); |
| } |
| ProcessMarkingDeque(); |
| } |
| |
| |
| void MarkCompactCollector::ReattachInitialMaps() { |
| HeapObjectIterator map_iterator(heap()->map_space()); |
| for (HeapObject* obj = map_iterator.Next(); |
| obj != NULL; |
| obj = map_iterator.Next()) { |
| if (obj->IsFreeSpace()) continue; |
| Map* map = Map::cast(obj); |
| |
| STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE); |
| if (map->instance_type() < FIRST_JS_RECEIVER_TYPE) continue; |
| |
| if (map->attached_to_shared_function_info()) { |
| JSFunction::cast(map->constructor())->shared()->AttachInitialMap(map); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearNonLiveTransitions() { |
| HeapObjectIterator map_iterator(heap()->map_space()); |
| // Iterate over the map space, setting map transitions that go from |
| // a marked map to an unmarked map to null transitions. This action |
| // is carried out only on maps of JSObjects and related subtypes. |
| for (HeapObject* obj = map_iterator.Next(); |
| obj != NULL; obj = map_iterator.Next()) { |
| Map* map = reinterpret_cast<Map*>(obj); |
| MarkBit map_mark = Marking::MarkBitFrom(map); |
| if (map->IsFreeSpace()) continue; |
| |
| ASSERT(map->IsMap()); |
| // Only JSObject and subtypes have map transitions and back pointers. |
| STATIC_ASSERT(LAST_TYPE == LAST_JS_OBJECT_TYPE); |
| if (map->instance_type() < FIRST_JS_OBJECT_TYPE) continue; |
| |
| if (map_mark.Get() && |
| map->attached_to_shared_function_info()) { |
| // This map is used for inobject slack tracking and has been detached |
| // from SharedFunctionInfo during the mark phase. |
| // Since it survived the GC, reattach it now. |
| map->unchecked_constructor()->unchecked_shared()->AttachInitialMap(map); |
| } |
| |
| ClearNonLivePrototypeTransitions(map); |
| ClearNonLiveMapTransitions(map, map_mark); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearNonLivePrototypeTransitions(Map* map) { |
| int number_of_transitions = map->NumberOfProtoTransitions(); |
| FixedArray* prototype_transitions = map->prototype_transitions(); |
| |
| int new_number_of_transitions = 0; |
| const int header = Map::kProtoTransitionHeaderSize; |
| const int proto_offset = header + Map::kProtoTransitionPrototypeOffset; |
| const int map_offset = header + Map::kProtoTransitionMapOffset; |
| const int step = Map::kProtoTransitionElementsPerEntry; |
| for (int i = 0; i < number_of_transitions; i++) { |
| Object* prototype = prototype_transitions->get(proto_offset + i * step); |
| Object* cached_map = prototype_transitions->get(map_offset + i * step); |
| if (IsMarked(prototype) && IsMarked(cached_map)) { |
| int proto_index = proto_offset + new_number_of_transitions * step; |
| int map_index = map_offset + new_number_of_transitions * step; |
| if (new_number_of_transitions != i) { |
| prototype_transitions->set_unchecked( |
| heap_, |
| proto_index, |
| prototype, |
| UPDATE_WRITE_BARRIER); |
| prototype_transitions->set_unchecked( |
| heap_, |
| map_index, |
| cached_map, |
| SKIP_WRITE_BARRIER); |
| } |
| Object** slot = |
| HeapObject::RawField(prototype_transitions, |
| FixedArray::OffsetOfElementAt(proto_index)); |
| RecordSlot(slot, slot, prototype); |
| new_number_of_transitions++; |
| } |
| } |
| |
| if (new_number_of_transitions != number_of_transitions) { |
| map->SetNumberOfProtoTransitions(new_number_of_transitions); |
| } |
| |
| // Fill slots that became free with undefined value. |
| for (int i = new_number_of_transitions * step; |
| i < number_of_transitions * step; |
| i++) { |
| prototype_transitions->set_undefined(heap_, header + i); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearNonLiveMapTransitions(Map* map, |
| MarkBit map_mark) { |
| Object* potential_parent = map->GetBackPointer(); |
| if (!potential_parent->IsMap()) return; |
| Map* parent = Map::cast(potential_parent); |
| |
| // Follow back pointer, check whether we are dealing with a map transition |
| // from a live map to a dead path and in case clear transitions of parent. |
| bool current_is_alive = map_mark.Get(); |
| bool parent_is_alive = Marking::MarkBitFrom(parent).Get(); |
| if (!current_is_alive && parent_is_alive) { |
| parent->ClearNonLiveTransitions(heap()); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessWeakMaps() { |
| Object* weak_map_obj = encountered_weak_maps(); |
| while (weak_map_obj != Smi::FromInt(0)) { |
| ASSERT(MarkCompactCollector::IsMarked(HeapObject::cast(weak_map_obj))); |
| JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj); |
| ObjectHashTable* table = ObjectHashTable::cast(weak_map->table()); |
| Object** anchor = reinterpret_cast<Object**>(table->address()); |
| for (int i = 0; i < table->Capacity(); i++) { |
| if (MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) { |
| Object** key_slot = |
| HeapObject::RawField(table, FixedArray::OffsetOfElementAt( |
| ObjectHashTable::EntryToIndex(i))); |
| RecordSlot(anchor, key_slot, *key_slot); |
| Object** value_slot = |
| HeapObject::RawField(table, FixedArray::OffsetOfElementAt( |
| ObjectHashTable::EntryToValueIndex(i))); |
| StaticMarkingVisitor::MarkObjectByPointer(this, anchor, value_slot); |
| } |
| } |
| weak_map_obj = weak_map->next(); |
| } |
| } |
| |
| |
| void MarkCompactCollector::ClearWeakMaps() { |
| Object* weak_map_obj = encountered_weak_maps(); |
| while (weak_map_obj != Smi::FromInt(0)) { |
| ASSERT(MarkCompactCollector::IsMarked(HeapObject::cast(weak_map_obj))); |
| JSWeakMap* weak_map = reinterpret_cast<JSWeakMap*>(weak_map_obj); |
| ObjectHashTable* table = ObjectHashTable::cast(weak_map->table()); |
| for (int i = 0; i < table->Capacity(); i++) { |
| if (!MarkCompactCollector::IsMarked(HeapObject::cast(table->KeyAt(i)))) { |
| table->RemoveEntry(i); |
| } |
| } |
| weak_map_obj = weak_map->next(); |
| weak_map->set_next(Smi::FromInt(0)); |
| } |
| set_encountered_weak_maps(Smi::FromInt(0)); |
| } |
| |
| |
| // We scavange 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(Address dst, |
| Address src, |
| int size, |
| AllocationSpace dest) { |
| HEAP_PROFILE(heap(), ObjectMoveEvent(src, dst)); |
| if (dest == OLD_POINTER_SPACE || dest == LO_SPACE) { |
| Address src_slot = src; |
| Address dst_slot = dst; |
| ASSERT(IsAligned(size, kPointerSize)); |
| |
| for (int remaining = size / kPointerSize; remaining > 0; remaining--) { |
| Object* value = Memory::Object_at(src_slot); |
| |
| Memory::Object_at(dst_slot) = value; |
| |
| if (heap_->InNewSpace(value)) { |
| heap_->store_buffer()->Mark(dst_slot); |
| } else if (value->IsHeapObject() && IsOnEvacuationCandidate(value)) { |
| SlotsBuffer::AddTo(&slots_buffer_allocator_, |
| &migration_slots_buffer_, |
| reinterpret_cast<Object**>(dst_slot), |
| SlotsBuffer::IGNORE_OVERFLOW); |
| } |
| |
| src_slot += kPointerSize; |
| dst_slot += kPointerSize; |
| } |
| |
| if (compacting_ && HeapObject::FromAddress(dst)->IsJSFunction()) { |
| Address code_entry_slot = dst + JSFunction::kCodeEntryOffset; |
| Address code_entry = Memory::Address_at(code_entry_slot); |
| |
| if (Page::FromAddress(code_entry)->IsEvacuationCandidate()) { |
| SlotsBuffer::AddTo(&slots_buffer_allocator_, |
| &migration_slots_buffer_, |
| SlotsBuffer::CODE_ENTRY_SLOT, |
| code_entry_slot, |
| SlotsBuffer::IGNORE_OVERFLOW); |
| } |
| } |
| } else if (dest == CODE_SPACE) { |
| PROFILE(heap()->isolate(), CodeMoveEvent(src, dst)); |
| heap()->MoveBlock(dst, src, size); |
| SlotsBuffer::AddTo(&slots_buffer_allocator_, |
| &migration_slots_buffer_, |
| SlotsBuffer::RELOCATED_CODE_OBJECT, |
| dst, |
| SlotsBuffer::IGNORE_OVERFLOW); |
| Code::cast(HeapObject::FromAddress(dst))->Relocate(dst - src); |
| } else { |
| ASSERT(dest == OLD_DATA_SPACE || dest == NEW_SPACE); |
| heap()->MoveBlock(dst, src, size); |
| } |
| Memory::Address_at(src) = dst; |
| } |
| |
| |
| // 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) { |
| UpdatePointer(p); |
| } |
| |
| void VisitPointers(Object** start, Object** end) { |
| for (Object** p = start; p < end; p++) UpdatePointer(p); |
| } |
| |
| void VisitEmbeddedPointer(RelocInfo* rinfo) { |
| ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT); |
| Object* target = rinfo->target_object(); |
| VisitPointer(&target); |
| rinfo->set_target_object(target); |
| } |
| |
| void VisitCodeTarget(RelocInfo* rinfo) { |
| ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->target_address()); |
| VisitPointer(&target); |
| rinfo->set_target_address(Code::cast(target)->instruction_start()); |
| } |
| |
| void VisitDebugTarget(RelocInfo* rinfo) { |
| ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) && |
| rinfo->IsPatchedReturnSequence()) || |
| (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) && |
| rinfo->IsPatchedDebugBreakSlotSequence())); |
| Object* target = Code::GetCodeFromTargetAddress(rinfo->call_address()); |
| VisitPointer(&target); |
| rinfo->set_call_address(Code::cast(target)->instruction_start()); |
| } |
| |
| static inline void UpdateSlot(Heap* heap, Object** slot) { |
| Object* obj = *slot; |
| |
| if (!obj->IsHeapObject()) return; |
| |
| HeapObject* heap_obj = HeapObject::cast(obj); |
| |
| MapWord map_word = heap_obj->map_word(); |
| if (map_word.IsForwardingAddress()) { |
| ASSERT(heap->InFromSpace(heap_obj) || |
| MarkCompactCollector::IsOnEvacuationCandidate(heap_obj)); |
| HeapObject* target = map_word.ToForwardingAddress(); |
| *slot = target; |
| ASSERT(!heap->InFromSpace(target) && |
| !MarkCompactCollector::IsOnEvacuationCandidate(target)); |
| } |
| } |
| |
| private: |
| inline void UpdatePointer(Object** p) { |
| UpdateSlot(heap_, p); |
| } |
| |
| Heap* heap_; |
| }; |
| |
| |
| static void UpdatePointer(HeapObject** p, HeapObject* object) { |
| ASSERT(*p == object); |
| |
| Address old_addr = object->address(); |
| |
| Address new_addr = Memory::Address_at(old_addr); |
| |
| // The new space sweep will overwrite the map word of dead objects |
| // with NULL. In this case we do not need to transfer this entry to |
| // the store buffer which we are rebuilding. |
| if (new_addr != NULL) { |
| *p = HeapObject::FromAddress(new_addr); |
| } else { |
| // We have to zap this pointer, because the store buffer may overflow later, |
| // and then we have to scan the entire heap and we don't want to find |
| // spurious newspace pointers in the old space. |
| // TODO(mstarzinger): This was changed to a sentinel value to track down |
| // rare crashes, change it back to Smi::FromInt(0) later. |
| *p = reinterpret_cast<HeapObject*>(Smi::FromInt(0x0f100d00 >> 1)); // flood |
| } |
| } |
| |
| |
| 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::TryPromoteObject(HeapObject* object, |
| int object_size) { |
| Object* result; |
| |
| if (object_size > Page::kMaxNonCodeHeapObjectSize) { |
| MaybeObject* maybe_result = |
| heap()->lo_space()->AllocateRaw(object_size, NOT_EXECUTABLE); |
| if (maybe_result->ToObject(&result)) { |
| HeapObject* target = HeapObject::cast(result); |
| MigrateObject(target->address(), |
| object->address(), |
| object_size, |
| LO_SPACE); |
| heap()->mark_compact_collector()->tracer()-> |
| increment_promoted_objects_size(object_size); |
| return true; |
| } |
| } else { |
| OldSpace* target_space = heap()->TargetSpace(object); |
| |
| ASSERT(target_space == heap()->old_pointer_space() || |
| target_space == heap()->old_data_space()); |
| MaybeObject* maybe_result = target_space->AllocateRaw(object_size); |
| if (maybe_result->ToObject(&result)) { |
| HeapObject* target = HeapObject::cast(result); |
| MigrateObject(target->address(), |
| object->address(), |
| object_size, |
| target_space->identity()); |
| heap()->mark_compact_collector()->tracer()-> |
| increment_promoted_objects_size(object_size); |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| |
| void MarkCompactCollector::EvacuateNewSpace() { |
| // There are soft limits in the allocation code, designed trigger a mark |
| // sweep collection by failing allocations. But since we are already in |
| // a mark-sweep allocation, there is no sense in trying to trigger one. |
| AlwaysAllocateScope scope; |
| heap()->CheckNewSpaceExpansionCriteria(); |
| |
| NewSpace* new_space = heap()->new_space(); |
| |
| // Store allocation range before flipping semispaces. |
| Address from_bottom = new_space->bottom(); |
| Address from_top = new_space->top(); |
| |
| // Flip the semispaces. After flipping, to space is empty, from space has |
| // live objects. |
| new_space->Flip(); |
| new_space->ResetAllocationInfo(); |
| |
| int survivors_size = 0; |
| |
| // First pass: traverse all objects in inactive semispace, remove marks, |
| // migrate live objects and write forwarding addresses. This stage puts |
| // new entries in the store buffer and may cause some pages to be marked |
| // scan-on-scavenge. |
| SemiSpaceIterator from_it(from_bottom, from_top); |
| for (HeapObject* object = from_it.Next(); |
| object != NULL; |
| object = from_it.Next()) { |
| MarkBit mark_bit = Marking::MarkBitFrom(object); |
| if (mark_bit.Get()) { |
| mark_bit.Clear(); |
| // Don't bother decrementing live bytes count. We'll discard the |
| // entire page at the end. |
| int size = object->Size(); |
| survivors_size += size; |
| |
| // Aggressively promote young survivors to the old space. |
| if (TryPromoteObject(object, size)) { |
| continue; |
| } |
| |
| // Promotion failed. Just migrate object to another semispace. |
| MaybeObject* allocation = new_space->AllocateRaw(size); |
| if (allocation->IsFailure()) { |
| if (!new_space->AddFreshPage()) { |
| // Shouldn't happen. We are sweeping linearly, and to-space |
| // has the same number of pages as from-space, so there is |
| // always room. |
| UNREACHABLE(); |
| } |
| allocation = new_space->AllocateRaw(size); |
| ASSERT(!allocation->IsFailure()); |
| } |
| Object* target = allocation->ToObjectUnchecked(); |
| |
| MigrateObject(HeapObject::cast(target)->address(), |
| object->address(), |
| size, |
| NEW_SPACE); |
| } else { |
| // Process the dead object before we write a NULL into its header. |
| LiveObjectList::ProcessNonLive(object); |
| |
| // Mark dead objects in the new space with null in their map field. |
| Memory::Address_at(object->address()) = NULL; |
| } |
| } |
| |
| heap_->IncrementYoungSurvivorsCounter(survivors_size); |
| new_space->set_age_mark(new_space->top()); |
| } |
| |
| |
| void MarkCompactCollector::EvacuateLiveObjectsFromPage(Page* p) { |
| AlwaysAllocateScope always_allocate; |
| PagedSpace* space = static_cast<PagedSpace*>(p->owner()); |
| ASSERT(p->IsEvacuationCandidate() && !p->WasSwept()); |
| MarkBit::CellType* cells = p->markbits()->cells(); |
| p->MarkSweptPrecisely(); |
| |
| int last_cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(p->area_end()))); |
| |
| Address cell_base = p->area_start(); |
| int cell_index = Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(cell_base))); |
| |
| int offsets[16]; |
| |
| for (; |
| cell_index < last_cell_index; |
| cell_index++, cell_base += 32 * kPointerSize) { |
| ASSERT((unsigned)cell_index == |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(cell_base)))); |
| if (cells[cell_index] == 0) continue; |
| |
| int live_objects = MarkWordToObjectStarts(cells[cell_index], offsets); |
| for (int i = 0; i < live_objects; i++) { |
| Address object_addr = cell_base + offsets[i] * kPointerSize; |
| HeapObject* object = HeapObject::FromAddress(object_addr); |
| ASSERT(Marking::IsBlack(Marking::MarkBitFrom(object))); |
| |
| int size = object->Size(); |
| |
| MaybeObject* target = space->AllocateRaw(size); |
| if (target->IsFailure()) { |
| // OS refused to give us memory. |
| V8::FatalProcessOutOfMemory("Evacuation"); |
| return; |
| } |
| |
| Object* target_object = target->ToObjectUnchecked(); |
| |
| MigrateObject(HeapObject::cast(target_object)->address(), |
| object_addr, |
| size, |
| space->identity()); |
| ASSERT(object->map_word().IsForwardingAddress()); |
| } |
| |
| // Clear marking bits for current cell. |
| cells[cell_index] = 0; |
| } |
| p->ResetLiveBytes(); |
| } |
| |
| |
| void MarkCompactCollector::EvacuatePages() { |
| int npages = evacuation_candidates_.length(); |
| for (int i = 0; i < npages; i++) { |
| Page* p = evacuation_candidates_[i]; |
| ASSERT(p->IsEvacuationCandidate() || |
| p->IsFlagSet(Page::RESCAN_ON_EVACUATION)); |
| if (p->IsEvacuationCandidate()) { |
| // During compaction we might have to request a new page. |
| // Check that space still have room for that. |
| if (static_cast<PagedSpace*>(p->owner())->CanExpand()) { |
| EvacuateLiveObjectsFromPage(p); |
| } else { |
| // Without room for expansion evacuation is not guaranteed to succeed. |
| // Pessimistically abandon unevacuated pages. |
| for (int j = i; j < npages; j++) { |
| Page* page = evacuation_candidates_[j]; |
| slots_buffer_allocator_.DeallocateChain(page->slots_buffer_address()); |
| page->ClearEvacuationCandidate(); |
| page->SetFlag(Page::RESCAN_ON_EVACUATION); |
| } |
| return; |
| } |
| } |
| } |
| } |
| |
| |
| 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; |
| } |
| }; |
| |
| |
| static inline void UpdateSlot(ObjectVisitor* v, |
| SlotsBuffer::SlotType slot_type, |
| Address addr) { |
| switch (slot_type) { |
| case SlotsBuffer::CODE_TARGET_SLOT: { |
| RelocInfo rinfo(addr, RelocInfo::CODE_TARGET, 0, NULL); |
| rinfo.Visit(v); |
| break; |
| } |
| case SlotsBuffer::CODE_ENTRY_SLOT: { |
| v->VisitCodeEntry(addr); |
| break; |
| } |
| case SlotsBuffer::RELOCATED_CODE_OBJECT: { |
| HeapObject* obj = HeapObject::FromAddress(addr); |
| Code::cast(obj)->CodeIterateBody(v); |
| break; |
| } |
| case SlotsBuffer::DEBUG_TARGET_SLOT: { |
| RelocInfo rinfo(addr, RelocInfo::DEBUG_BREAK_SLOT, 0, NULL); |
| if (rinfo.IsPatchedDebugBreakSlotSequence()) rinfo.Visit(v); |
| break; |
| } |
| case SlotsBuffer::JS_RETURN_SLOT: { |
| RelocInfo rinfo(addr, RelocInfo::JS_RETURN, 0, NULL); |
| if (rinfo.IsPatchedReturnSequence()) rinfo.Visit(v); |
| break; |
| } |
| case SlotsBuffer::EMBEDDED_OBJECT_SLOT: { |
| RelocInfo rinfo(addr, RelocInfo::EMBEDDED_OBJECT, 0, NULL); |
| rinfo.Visit(v); |
| break; |
| } |
| default: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| |
| |
| enum SweepingMode { |
| SWEEP_ONLY, |
| SWEEP_AND_VISIT_LIVE_OBJECTS |
| }; |
| |
| |
| enum SkipListRebuildingMode { |
| REBUILD_SKIP_LIST, |
| IGNORE_SKIP_LIST |
| }; |
| |
| |
| // Sweep a space precisely. After this has been done the space can |
| // be iterated precisely, hitting only the live objects. Code space |
| // is always swept precisely because we want to be able to iterate |
| // over it. Map space is swept precisely, because it is not compacted. |
| // Slots in live objects pointing into evacuation candidates are updated |
| // if requested. |
| template<SweepingMode sweeping_mode, SkipListRebuildingMode skip_list_mode> |
| static void SweepPrecisely(PagedSpace* space, |
| Page* p, |
| ObjectVisitor* v) { |
| ASSERT(!p->IsEvacuationCandidate() && !p->WasSwept()); |
| ASSERT_EQ(skip_list_mode == REBUILD_SKIP_LIST, |
| space->identity() == CODE_SPACE); |
| ASSERT((p->skip_list() == NULL) || (skip_list_mode == REBUILD_SKIP_LIST)); |
| |
| MarkBit::CellType* cells = p->markbits()->cells(); |
| p->MarkSweptPrecisely(); |
| |
| int last_cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(p->area_end()))); |
| |
| Address free_start = p->area_start(); |
| int cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(free_start))); |
| |
| ASSERT(reinterpret_cast<intptr_t>(free_start) % (32 * kPointerSize) == 0); |
| Address object_address = free_start; |
| int offsets[16]; |
| |
| SkipList* skip_list = p->skip_list(); |
| int curr_region = -1; |
| if ((skip_list_mode == REBUILD_SKIP_LIST) && skip_list) { |
| skip_list->Clear(); |
| } |
| |
| for (; |
| cell_index < last_cell_index; |
| cell_index++, object_address += 32 * kPointerSize) { |
| ASSERT((unsigned)cell_index == |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(object_address)))); |
| int live_objects = MarkWordToObjectStarts(cells[cell_index], offsets); |
| int live_index = 0; |
| for ( ; live_objects != 0; live_objects--) { |
| Address free_end = object_address + offsets[live_index++] * kPointerSize; |
| if (free_end != free_start) { |
| space->Free(free_start, static_cast<int>(free_end - free_start)); |
| } |
| HeapObject* live_object = HeapObject::FromAddress(free_end); |
| ASSERT(Marking::IsBlack(Marking::MarkBitFrom(live_object))); |
| Map* map = live_object->map(); |
| int size = live_object->SizeFromMap(map); |
| if (sweeping_mode == SWEEP_AND_VISIT_LIVE_OBJECTS) { |
| live_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 marking bits for current cell. |
| cells[cell_index] = 0; |
| } |
| if (free_start != p->area_end()) { |
| space->Free(free_start, static_cast<int>(p->area_end() - free_start)); |
| } |
| p->ResetLiveBytes(); |
| } |
| |
| |
| static bool SetMarkBitsUnderInvalidatedCode(Code* code, bool value) { |
| Page* p = Page::FromAddress(code->address()); |
| |
| if (p->IsEvacuationCandidate() || |
| p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) { |
| return false; |
| } |
| |
| Address code_start = code->address(); |
| Address code_end = code_start + code->Size(); |
| |
| uint32_t start_index = MemoryChunk::FastAddressToMarkbitIndex(code_start); |
| uint32_t end_index = |
| MemoryChunk::FastAddressToMarkbitIndex(code_end - kPointerSize); |
| |
| Bitmap* b = p->markbits(); |
| |
| MarkBit start_mark_bit = b->MarkBitFromIndex(start_index); |
| MarkBit end_mark_bit = b->MarkBitFromIndex(end_index); |
| |
| MarkBit::CellType* start_cell = start_mark_bit.cell(); |
| MarkBit::CellType* end_cell = end_mark_bit.cell(); |
| |
| if (value) { |
| MarkBit::CellType start_mask = ~(start_mark_bit.mask() - 1); |
| MarkBit::CellType end_mask = (end_mark_bit.mask() << 1) - 1; |
| |
| if (start_cell == end_cell) { |
| *start_cell |= start_mask & end_mask; |
| } else { |
| *start_cell |= start_mask; |
| for (MarkBit::CellType* cell = start_cell + 1; cell < end_cell; cell++) { |
| *cell = ~0; |
| } |
| *end_cell |= end_mask; |
| } |
| } else { |
| for (MarkBit::CellType* cell = start_cell ; cell <= end_cell; cell++) { |
| *cell = 0; |
| } |
| } |
| |
| return true; |
| } |
| |
| |
| static bool IsOnInvalidatedCodeObject(Address addr) { |
| // We did not record any slots in large objects thus |
| // we can safely go to the page from the slot address. |
| Page* p = Page::FromAddress(addr); |
| |
| // First check owner's identity because old pointer and old data spaces |
| // are swept lazily and might still have non-zero mark-bits on some |
| // pages. |
| if (p->owner()->identity() != CODE_SPACE) return false; |
| |
| // In code space only bits on evacuation candidates (but we don't record |
| // any slots on them) and under invalidated code objects are non-zero. |
| MarkBit mark_bit = |
| p->markbits()->MarkBitFromIndex(Page::FastAddressToMarkbitIndex(addr)); |
| |
| return mark_bit.Get(); |
| } |
| |
| |
| void MarkCompactCollector::InvalidateCode(Code* code) { |
| if (heap_->incremental_marking()->IsCompacting() && |
| !ShouldSkipEvacuationSlotRecording(code)) { |
| ASSERT(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; |
| |
| invalidated_code_.Add(code); |
| } |
| } |
| |
| |
| bool MarkCompactCollector::MarkInvalidatedCode() { |
| bool code_marked = false; |
| |
| int length = invalidated_code_.length(); |
| for (int i = 0; i < length; i++) { |
| Code* code = invalidated_code_[i]; |
| |
| if (SetMarkBitsUnderInvalidatedCode(code, true)) { |
| code_marked = true; |
| } |
| } |
| |
| return code_marked; |
| } |
| |
| |
| void MarkCompactCollector::RemoveDeadInvalidatedCode() { |
| int length = invalidated_code_.length(); |
| for (int i = 0; i < length; i++) { |
| if (!IsMarked(invalidated_code_[i])) invalidated_code_[i] = NULL; |
| } |
| } |
| |
| |
| void MarkCompactCollector::ProcessInvalidatedCode(ObjectVisitor* visitor) { |
| int length = invalidated_code_.length(); |
| for (int i = 0; i < length; i++) { |
| Code* code = invalidated_code_[i]; |
| if (code != NULL) { |
| code->Iterate(visitor); |
| SetMarkBitsUnderInvalidatedCode(code, false); |
| } |
| } |
| invalidated_code_.Rewind(0); |
| } |
| |
| |
| void MarkCompactCollector::EvacuateNewSpaceAndCandidates() { |
| bool code_slots_filtering_required; |
| { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP_NEWSPACE); |
| code_slots_filtering_required = MarkInvalidatedCode(); |
| |
| EvacuateNewSpace(); |
| } |
| |
| |
| { GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_EVACUATE_PAGES); |
| EvacuatePages(); |
| } |
| |
| // Second pass: find pointers to new space and update them. |
| PointersUpdatingVisitor updating_visitor(heap()); |
| |
| { GCTracer::Scope gc_scope(tracer_, |
| GCTracer::Scope::MC_UPDATE_NEW_TO_NEW_POINTERS); |
| // Update pointers in to space. |
| SemiSpaceIterator to_it(heap()->new_space()->bottom(), |
| heap()->new_space()->top()); |
| 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); |
| } |
| } |
| |
| { GCTracer::Scope gc_scope(tracer_, |
| GCTracer::Scope::MC_UPDATE_ROOT_TO_NEW_POINTERS); |
| // Update roots. |
| heap_->IterateRoots(&updating_visitor, VISIT_ALL_IN_SWEEP_NEWSPACE); |
| LiveObjectList::IterateElements(&updating_visitor); |
| } |
| |
| { GCTracer::Scope gc_scope(tracer_, |
| GCTracer::Scope::MC_UPDATE_OLD_TO_NEW_POINTERS); |
| StoreBufferRebuildScope scope(heap_, |
| heap_->store_buffer(), |
| &Heap::ScavengeStoreBufferCallback); |
| heap_->store_buffer()->IteratePointersToNewSpace(&UpdatePointer); |
| } |
| |
| { GCTracer::Scope gc_scope(tracer_, |
| GCTracer::Scope::MC_UPDATE_POINTERS_TO_EVACUATED); |
| SlotsBuffer::UpdateSlotsRecordedIn(heap_, |
| migration_slots_buffer_, |
| code_slots_filtering_required); |
| if (FLAG_trace_fragmentation) { |
| PrintF(" migration slots buffer: %d\n", |
| SlotsBuffer::SizeOfChain(migration_slots_buffer_)); |
| } |
| |
| if (compacting_ && was_marked_incrementally_) { |
| // It's difficult to filter out slots recorded for large objects. |
| LargeObjectIterator it(heap_->lo_space()); |
| for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) { |
| // LargeObjectSpace is not swept yet thus we have to skip |
| // dead objects explicitly. |
| if (!IsMarked(obj)) continue; |
| |
| Page* p = Page::FromAddress(obj->address()); |
| if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) { |
| obj->Iterate(&updating_visitor); |
| p->ClearFlag(Page::RESCAN_ON_EVACUATION); |
| } |
| } |
| } |
| } |
| |
| int npages = evacuation_candidates_.length(); |
| { GCTracer::Scope gc_scope( |
| tracer_, GCTracer::Scope::MC_UPDATE_POINTERS_BETWEEN_EVACUATED); |
| for (int i = 0; i < npages; i++) { |
| Page* p = evacuation_candidates_[i]; |
| ASSERT(p->IsEvacuationCandidate() || |
| p->IsFlagSet(Page::RESCAN_ON_EVACUATION)); |
| |
| if (p->IsEvacuationCandidate()) { |
| SlotsBuffer::UpdateSlotsRecordedIn(heap_, |
| p->slots_buffer(), |
| code_slots_filtering_required); |
| if (FLAG_trace_fragmentation) { |
| PrintF(" page %p slots buffer: %d\n", |
| reinterpret_cast<void*>(p), |
| SlotsBuffer::SizeOfChain(p->slots_buffer())); |
| } |
| |
| // 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(); |
| } else { |
| 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); |
| |
| switch (space->identity()) { |
| case OLD_DATA_SPACE: |
| SweepConservatively(space, p); |
| break; |
| case OLD_POINTER_SPACE: |
| SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS, IGNORE_SKIP_LIST>( |
| space, p, &updating_visitor); |
| break; |
| case CODE_SPACE: |
| SweepPrecisely<SWEEP_AND_VISIT_LIVE_OBJECTS, REBUILD_SKIP_LIST>( |
| space, p, &updating_visitor); |
| break; |
| default: |
| UNREACHABLE(); |
| break; |
| } |
| } |
| } |
| } |
| |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_UPDATE_MISC_POINTERS); |
| |
| // Update pointers from cells. |
| HeapObjectIterator cell_iterator(heap_->cell_space()); |
| for (HeapObject* cell = cell_iterator.Next(); |
| cell != NULL; |
| cell = cell_iterator.Next()) { |
| if (cell->IsJSGlobalPropertyCell()) { |
| Address value_address = |
| reinterpret_cast<Address>(cell) + |
| (JSGlobalPropertyCell::kValueOffset - kHeapObjectTag); |
| updating_visitor.VisitPointer(reinterpret_cast<Object**>(value_address)); |
| } |
| } |
| |
| // Update pointer from the global contexts list. |
| updating_visitor.VisitPointer(heap_->global_contexts_list_address()); |
| |
| heap_->symbol_table()->Iterate(&updating_visitor); |
| |
| // Update pointers from external string table. |
| heap_->UpdateReferencesInExternalStringTable( |
| &UpdateReferenceInExternalStringTableEntry); |
| |
| if (!FLAG_watch_ic_patching) { |
| // Update JSFunction pointers from the runtime profiler. |
| heap()->isolate()->runtime_profiler()->UpdateSamplesAfterCompact( |
| &updating_visitor); |
| } |
| |
| EvacuationWeakObjectRetainer evacuation_object_retainer; |
| heap()->ProcessWeakReferences(&evacuation_object_retainer); |
| |
| // Visit invalidated code (we ignored all slots on it) and clear mark-bits |
| // under it. |
| ProcessInvalidatedCode(&updating_visitor); |
| |
| heap_->isolate()->inner_pointer_to_code_cache()->Flush(); |
| |
| #ifdef DEBUG |
| if (FLAG_verify_heap) { |
| VerifyEvacuation(heap_); |
| } |
| #endif |
| |
| slots_buffer_allocator_.DeallocateChain(&migration_slots_buffer_); |
| ASSERT(migration_slots_buffer_ == NULL); |
| for (int i = 0; i < npages; i++) { |
| Page* p = evacuation_candidates_[i]; |
| if (!p->IsEvacuationCandidate()) continue; |
| PagedSpace* space = static_cast<PagedSpace*>(p->owner()); |
| space->Free(p->area_start(), p->area_size()); |
| p->set_scan_on_scavenge(false); |
| slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address()); |
| p->ResetLiveBytes(); |
| space->ReleasePage(p); |
| } |
| evacuation_candidates_.Rewind(0); |
| compacting_ = false; |
| } |
| |
| |
| static const int kStartTableEntriesPerLine = 5; |
| static const int kStartTableLines = 171; |
| static const int kStartTableInvalidLine = 127; |
| static const int kStartTableUnusedEntry = 126; |
| |
| #define _ kStartTableUnusedEntry |
| #define X kStartTableInvalidLine |
| // Mark-bit to object start offset table. |
| // |
| // The line is indexed by the mark bits in a byte. The first number on |
| // the line describes the number of live object starts for the line and the |
| // other numbers on the line describe the offsets (in words) of the object |
| // starts. |
| // |
| // Since objects are at least 2 words large we don't have entries for two |
| // consecutive 1 bits. All entries after 170 have at least 2 consecutive bits. |
| char kStartTable[kStartTableLines * kStartTableEntriesPerLine] = { |
| 0, _, _, _, _, // 0 |
| 1, 0, _, _, _, // 1 |
| 1, 1, _, _, _, // 2 |
| X, _, _, _, _, // 3 |
| 1, 2, _, _, _, // 4 |
| 2, 0, 2, _, _, // 5 |
| X, _, _, _, _, // 6 |
| X, _, _, _, _, // 7 |
| 1, 3, _, _, _, // 8 |
| 2, 0, 3, _, _, // 9 |
| 2, 1, 3, _, _, // 10 |
| X, _, _, _, _, // 11 |
| X, _, _, _, _, // 12 |
| X, _, _, _, _, // 13 |
| X, _, _, _, _, // 14 |
| X, _, _, _, _, // 15 |
| 1, 4, _, _, _, // 16 |
| 2, 0, 4, _, _, // 17 |
| 2, 1, 4, _, _, // 18 |
| X, _, _, _, _, // 19 |
| 2, 2, 4, _, _, // 20 |
| 3, 0, 2, 4, _, // 21 |
| X, _, _, _, _, // 22 |
| X, _, _, _, _, // 23 |
| X, _, _, _, _, // 24 |
| X, _, _, _, _, // 25 |
| X, _, _, _, _, // 26 |
| X, _, _, _, _, // 27 |
| X, _, _, _, _, // 28 |
| X, _, _, _, _, // 29 |
| X, _, _, _, _, // 30 |
| X, _, _, _, _, // 31 |
| 1, 5, _, _, _, // 32 |
| 2, 0, 5, _, _, // 33 |
| 2, 1, 5, _, _, // 34 |
| X, _, _, _, _, // 35 |
| 2, 2, 5, _, _, // 36 |
| 3, 0, 2, 5, _, // 37 |
| X, _, _, _, _, // 38 |
| X, _, _, _, _, // 39 |
| 2, 3, 5, _, _, // 40 |
| 3, 0, 3, 5, _, // 41 |
| 3, 1, 3, 5, _, // 42 |
| X, _, _, _, _, // 43 |
| X, _, _, _, _, // 44 |
| X, _, _, _, _, // 45 |
| X, _, _, _, _, // 46 |
| X, _, _, _, _, // 47 |
| X, _, _, _, _, // 48 |
| X, _, _, _, _, // 49 |
| X, _, _, _, _, // 50 |
| X, _, _, _, _, // 51 |
| X, _, _, _, _, // 52 |
| X, _, _, _, _, // 53 |
| X, _, _, _, _, // 54 |
| X, _, _, _, _, // 55 |
| X, _, _, _, _, // 56 |
| X, _, _, _, _, // 57 |
| X, _, _, _, _, // 58 |
| X, _, _, _, _, // 59 |
| X, _, _, _, _, // 60 |
| X, _, _, _, _, // 61 |
| X, _, _, _, _, // 62 |
| X, _, _, _, _, // 63 |
| 1, 6, _, _, _, // 64 |
| 2, 0, 6, _, _, // 65 |
| 2, 1, 6, _, _, // 66 |
| X, _, _, _, _, // 67 |
| 2, 2, 6, _, _, // 68 |
| 3, 0, 2, 6, _, // 69 |
| X, _, _, _, _, // 70 |
| X, _, _, _, _, // 71 |
| 2, 3, 6, _, _, // 72 |
| 3, 0, 3, 6, _, // 73 |
| 3, 1, 3, 6, _, // 74 |
| X, _, _, _, _, // 75 |
| X, _, _, _, _, // 76 |
| X, _, _, _, _, // 77 |
| X, _, _, _, _, // 78 |
| X, _, _, _, _, // 79 |
| 2, 4, 6, _, _, // 80 |
| 3, 0, 4, 6, _, // 81 |
| 3, 1, 4, 6, _, // 82 |
| X, _, _, _, _, // 83 |
| 3, 2, 4, 6, _, // 84 |
| 4, 0, 2, 4, 6, // 85 |
| X, _, _, _, _, // 86 |
| X, _, _, _, _, // 87 |
| X, _, _, _, _, // 88 |
| X, _, _, _, _, // 89 |
| X, _, _, _, _, // 90 |
| X, _, _, _, _, // 91 |
| X, _, _, _, _, // 92 |
| X, _, _, _, _, // 93 |
| X, _, _, _, _, // 94 |
| X, _, _, _, _, // 95 |
| X, _, _, _, _, // 96 |
| X, _, _, _, _, // 97 |
| X, _, _, _, _, // 98 |
| X, _, _, _, _, // 99 |
| X, _, _, _, _, // 100 |
| X, _, _, _, _, // 101 |
| X, _, _, _, _, // 102 |
| X, _, _, _, _, // 103 |
| X, _, _, _, _, // 104 |
| X, _, _, _, _, // 105 |
| X, _, _, _, _, // 106 |
| X, _, _, _, _, // 107 |
| X, _, _, _, _, // 108 |
| X, _, _, _, _, // 109 |
| X, _, _, _, _, // 110 |
| X, _, _, _, _, // 111 |
| X, _, _, _, _, // 112 |
| X, _, _, _, _, // 113 |
| X, _, _, _, _, // 114 |
| X, _, _, _, _, // 115 |
| X, _, _, _, _, // 116 |
| X, _, _, _, _, // 117 |
| X, _, _, _, _, // 118 |
| X, _, _, _, _, // 119 |
| X, _, _, _, _, // 120 |
| X, _, _, _, _, // 121 |
| X, _, _, _, _, // 122 |
| X, _, _, _, _, // 123 |
| X, _, _, _, _, // 124 |
| X, _, _, _, _, // 125 |
| X, _, _, _, _, // 126 |
| X, _, _, _, _, // 127 |
| 1, 7, _, _, _, // 128 |
| 2, 0, 7, _, _, // 129 |
| 2, 1, 7, _, _, // 130 |
| X, _, _, _, _, // 131 |
| 2, 2, 7, _, _, // 132 |
| 3, 0, 2, 7, _, // 133 |
| X, _, _, _, _, // 134 |
| X, _, _, _, _, // 135 |
| 2, 3, 7, _, _, // 136 |
| 3, 0, 3, 7, _, // 137 |
| 3, 1, 3, 7, _, // 138 |
| X, _, _, _, _, // 139 |
| X, _, _, _, _, // 140 |
| X, _, _, _, _, // 141 |
| X, _, _, _, _, // 142 |
| X, _, _, _, _, // 143 |
| 2, 4, 7, _, _, // 144 |
| 3, 0, 4, 7, _, // 145 |
| 3, 1, 4, 7, _, // 146 |
| X, _, _, _, _, // 147 |
| 3, 2, 4, 7, _, // 148 |
| 4, 0, 2, 4, 7, // 149 |
| X, _, _, _, _, // 150 |
| X, _, _, _, _, // 151 |
| X, _, _, _, _, // 152 |
| X, _, _, _, _, // 153 |
| X, _, _, _, _, // 154 |
| X, _, _, _, _, // 155 |
| X, _, _, _, _, // 156 |
| X, _, _, _, _, // 157 |
| X, _, _, _, _, // 158 |
| X, _, _, _, _, // 159 |
| 2, 5, 7, _, _, // 160 |
| 3, 0, 5, 7, _, // 161 |
| 3, 1, 5, 7, _, // 162 |
| X, _, _, _, _, // 163 |
| 3, 2, 5, 7, _, // 164 |
| 4, 0, 2, 5, 7, // 165 |
| X, _, _, _, _, // 166 |
| X, _, _, _, _, // 167 |
| 3, 3, 5, 7, _, // 168 |
| 4, 0, 3, 5, 7, // 169 |
| 4, 1, 3, 5, 7 // 170 |
| }; |
| #undef _ |
| #undef X |
| |
| |
| // Takes a word of mark bits. Returns the number of objects that start in the |
| // range. Puts the offsets of the words in the supplied array. |
| static inline int MarkWordToObjectStarts(uint32_t mark_bits, int* starts) { |
| int objects = 0; |
| int offset = 0; |
| |
| // No consecutive 1 bits. |
| ASSERT((mark_bits & 0x180) != 0x180); |
| ASSERT((mark_bits & 0x18000) != 0x18000); |
| ASSERT((mark_bits & 0x1800000) != 0x1800000); |
| |
| while (mark_bits != 0) { |
| int byte = (mark_bits & 0xff); |
| mark_bits >>= 8; |
| if (byte != 0) { |
| ASSERT(byte < kStartTableLines); // No consecutive 1 bits. |
| char* table = kStartTable + byte * kStartTableEntriesPerLine; |
| int objects_in_these_8_words = table[0]; |
| ASSERT(objects_in_these_8_words != kStartTableInvalidLine); |
| ASSERT(objects_in_these_8_words < kStartTableEntriesPerLine); |
| for (int i = 0; i < objects_in_these_8_words; i++) { |
| starts[objects++] = offset + table[1 + i]; |
| } |
| } |
| offset += 8; |
| } |
| return objects; |
| } |
| |
| |
| static inline Address DigestFreeStart(Address approximate_free_start, |
| uint32_t free_start_cell) { |
| ASSERT(free_start_cell != 0); |
| |
| // No consecutive 1 bits. |
| ASSERT((free_start_cell & (free_start_cell << 1)) == 0); |
| |
| int offsets[16]; |
| uint32_t cell = free_start_cell; |
| int offset_of_last_live; |
| if ((cell & 0x80000000u) != 0) { |
| // This case would overflow below. |
| offset_of_last_live = 31; |
| } else { |
| // Remove all but one bit, the most significant. This is an optimization |
| // that may or may not be worthwhile. |
| cell |= cell >> 16; |
| cell |= cell >> 8; |
| cell |= cell >> 4; |
| cell |= cell >> 2; |
| cell |= cell >> 1; |
| cell = (cell + 1) >> 1; |
| int live_objects = MarkWordToObjectStarts(cell, offsets); |
| ASSERT(live_objects == 1); |
| offset_of_last_live = offsets[live_objects - 1]; |
| } |
| Address last_live_start = |
| approximate_free_start + offset_of_last_live * kPointerSize; |
| HeapObject* last_live = HeapObject::FromAddress(last_live_start); |
| Address free_start = last_live_start + last_live->Size(); |
| return free_start; |
| } |
| |
| |
| static inline Address StartOfLiveObject(Address block_address, uint32_t cell) { |
| ASSERT(cell != 0); |
| |
| // No consecutive 1 bits. |
| ASSERT((cell & (cell << 1)) == 0); |
| |
| int offsets[16]; |
| if (cell == 0x80000000u) { // Avoid overflow below. |
| return block_address + 31 * kPointerSize; |
| } |
| uint32_t first_set_bit = ((cell ^ (cell - 1)) + 1) >> 1; |
| ASSERT((first_set_bit & cell) == first_set_bit); |
| int live_objects = MarkWordToObjectStarts(first_set_bit, offsets); |
| ASSERT(live_objects == 1); |
| USE(live_objects); |
| return block_address + offsets[0] * kPointerSize; |
| } |
| |
| |
| // Sweeps a space conservatively. After this has been done the larger free |
| // spaces have been put on the free list and the smaller ones have been |
| // ignored and left untouched. A free space is always either ignored or put |
| // on the free list, never split up into two parts. This is important |
| // because it means that any FreeSpace maps left actually describe a region of |
| // memory that can be ignored when scanning. Dead objects other than free |
| // spaces will not contain the free space map. |
| intptr_t MarkCompactCollector::SweepConservatively(PagedSpace* space, Page* p) { |
| ASSERT(!p->IsEvacuationCandidate() && !p->WasSwept()); |
| MarkBit::CellType* cells = p->markbits()->cells(); |
| p->MarkSweptConservatively(); |
| |
| int last_cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(p->area_end()))); |
| |
| int cell_index = |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(p->area_start()))); |
| |
| intptr_t freed_bytes = 0; |
| |
| // This is the start of the 32 word block that we are currently looking at. |
| Address block_address = p->area_start(); |
| |
| // Skip over all the dead objects at the start of the page and mark them free. |
| for (; |
| cell_index < last_cell_index; |
| cell_index++, block_address += 32 * kPointerSize) { |
| if (cells[cell_index] != 0) break; |
| } |
| size_t size = block_address - p->area_start(); |
| if (cell_index == last_cell_index) { |
| freed_bytes += static_cast<int>(space->Free(p->area_start(), |
| static_cast<int>(size))); |
| ASSERT_EQ(0, p->LiveBytes()); |
| return freed_bytes; |
| } |
| // Grow the size of the start-of-page free space a little to get up to the |
| // first live object. |
| Address free_end = StartOfLiveObject(block_address, cells[cell_index]); |
| // Free the first free space. |
| size = free_end - p->area_start(); |
| freed_bytes += space->Free(p->area_start(), |
| static_cast<int>(size)); |
| // The start of the current free area is represented in undigested form by |
| // the address of the last 32-word section that contained a live object and |
| // the marking bitmap for that cell, which describes where the live object |
| // started. Unless we find a large free space in the bitmap we will not |
| // digest this pair into a real address. We start the iteration here at the |
| // first word in the marking bit map that indicates a live object. |
| Address free_start = block_address; |
| uint32_t free_start_cell = cells[cell_index]; |
| |
| for ( ; |
| cell_index < last_cell_index; |
| cell_index++, block_address += 32 * kPointerSize) { |
| ASSERT((unsigned)cell_index == |
| Bitmap::IndexToCell( |
| Bitmap::CellAlignIndex( |
| p->AddressToMarkbitIndex(block_address)))); |
| uint32_t cell = cells[cell_index]; |
| if (cell != 0) { |
| // We have a live object. Check approximately whether it is more than 32 |
| // words since the last live object. |
| if (block_address - free_start > 32 * kPointerSize) { |
| free_start = DigestFreeStart(free_start, free_start_cell); |
| if (block_address - free_start > 32 * kPointerSize) { |
| // Now that we know the exact start of the free space it still looks |
| // like we have a large enough free space to be worth bothering with. |
| // so now we need to find the start of the first live object at the |
| // end of the free space. |
| free_end = StartOfLiveObject(block_address, cell); |
| freed_bytes += space->Free(free_start, |
| static_cast<int>(free_end - free_start)); |
| } |
| } |
| // Update our undigested record of where the current free area started. |
| free_start = block_address; |
| free_start_cell = cell; |
| // Clear marking bits for current cell. |
| cells[cell_index] = 0; |
| } |
| } |
| |
| // Handle the free space at the end of the page. |
| if (block_address - free_start > 32 * kPointerSize) { |
| free_start = DigestFreeStart(free_start, free_start_cell); |
| freed_bytes += space->Free(free_start, |
| static_cast<int>(block_address - free_start)); |
| } |
| |
| p->ResetLiveBytes(); |
| return freed_bytes; |
| } |
| |
| |
| void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) { |
| space->set_was_swept_conservatively(sweeper == CONSERVATIVE || |
| sweeper == LAZY_CONSERVATIVE); |
| |
| space->ClearStats(); |
| |
| PageIterator it(space); |
| |
| intptr_t freed_bytes = 0; |
| int pages_swept = 0; |
| intptr_t newspace_size = space->heap()->new_space()->Size(); |
| bool lazy_sweeping_active = false; |
| bool unused_page_present = false; |
| |
| while (it.has_next()) { |
| Page* p = it.next(); |
| |
| // Clear sweeping flags indicating that marking bits are still intact. |
| p->ClearSweptPrecisely(); |
| p->ClearSweptConservatively(); |
| |
| if (p->IsEvacuationCandidate()) { |
| ASSERT(evacuation_candidates_.length() > 0); |
| continue; |
| } |
| |
| if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) { |
| // Will be processed in EvacuateNewSpaceAndCandidates. |
| 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) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " released page.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| // Adjust unswept free bytes because releasing a page expects said |
| // counter to be accurate for unswept pages. |
| space->IncreaseUnsweptFreeBytes(p); |
| space->ReleasePage(p); |
| continue; |
| } |
| unused_page_present = true; |
| } |
| |
| if (lazy_sweeping_active) { |
| if (FLAG_gc_verbose) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " lazily postponed.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| space->IncreaseUnsweptFreeBytes(p); |
| continue; |
| } |
| |
| switch (sweeper) { |
| case CONSERVATIVE: { |
| if (FLAG_gc_verbose) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " conservatively.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| SweepConservatively(space, p); |
| pages_swept++; |
| break; |
| } |
| case LAZY_CONSERVATIVE: { |
| if (FLAG_gc_verbose) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " conservatively as needed.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| freed_bytes += SweepConservatively(space, p); |
| pages_swept++; |
| if (freed_bytes > 2 * newspace_size) { |
| space->SetPagesToSweep(p->next_page()); |
| lazy_sweeping_active = true; |
| } else { |
| if (FLAG_gc_verbose) { |
| PrintF("Only %" V8PRIdPTR " bytes freed. Still sweeping.\n", |
| freed_bytes); |
| } |
| } |
| break; |
| } |
| case PRECISE: { |
| if (FLAG_gc_verbose) { |
| PrintF("Sweeping 0x%" V8PRIxPTR " precisely.\n", |
| reinterpret_cast<intptr_t>(p)); |
| } |
| if (space->identity() == CODE_SPACE) { |
| SweepPrecisely<SWEEP_ONLY, REBUILD_SKIP_LIST>(space, p, NULL); |
| } else { |
| SweepPrecisely<SWEEP_ONLY, IGNORE_SKIP_LIST>(space, p, NULL); |
| } |
| pages_swept++; |
| break; |
| } |
| default: { |
| UNREACHABLE(); |
| } |
| } |
| } |
| |
| if (FLAG_gc_verbose) { |
| PrintF("SweepSpace: %s (%d pages swept)\n", |
| AllocationSpaceName(space->identity()), |
| pages_swept); |
| } |
| |
| // Give pages that are queued to be freed back to the OS. |
| heap()->FreeQueuedChunks(); |
| } |
| |
| |
| void MarkCompactCollector::SweepSpaces() { |
| GCTracer::Scope gc_scope(tracer_, GCTracer::Scope::MC_SWEEP); |
| #ifdef DEBUG |
| state_ = SWEEP_SPACES; |
| #endif |
| SweeperType how_to_sweep = |
| FLAG_lazy_sweeping ? LAZY_CONSERVATIVE : CONSERVATIVE; |
| if (FLAG_expose_gc) how_to_sweep = CONSERVATIVE; |
| if (sweep_precisely_) how_to_sweep = PRECISE; |
| // Noncompacting collections simply sweep the spaces to clear the mark |
| // bits and free the nonlive blocks (for old and map spaces). We sweep |
| // the map space last because freeing non-live maps overwrites them and |
| // the other spaces rely on possibly non-live maps to get the sizes for |
| // non-live objects. |
| SweepSpace(heap()->old_pointer_space(), how_to_sweep); |
| SweepSpace(heap()->old_data_space(), how_to_sweep); |
| |
| RemoveDeadInvalidatedCode(); |
| SweepSpace(heap()->code_space(), PRECISE); |
| |
| SweepSpace(heap()->cell_space(), PRECISE); |
| |
| EvacuateNewSpaceAndCandidates(); |
| |
| // ClearNonLiveTransitions depends on precise sweeping of map space to |
| // detect whether unmarked map became dead in this collection or in one |
| // of the previous ones. |
| SweepSpace(heap()->map_space(), PRECISE); |
| |
| // Deallocate unmarked objects and clear marked bits for marked objects. |
| heap_->lo_space()->FreeUnmarkedObjects(); |
| } |
| |
| |
| void MarkCompactCollector::EnableCodeFlushing(bool enable) { |
| if (enable) { |
| if (code_flusher_ != NULL) return; |
| code_flusher_ = new CodeFlusher(heap()->isolate()); |
| } else { |
| if (code_flusher_ == NULL) return; |
| delete code_flusher_; |
| code_flusher_ = NULL; |
| } |
| } |
| |
| |
| // 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) { |
| #ifdef ENABLE_GDB_JIT_INTERFACE |
| if (obj->IsCode()) { |
| GDBJITInterface::RemoveCode(reinterpret_cast<Code*>(obj)); |
| } |
| #endif |
| if (obj->IsCode()) { |
| PROFILE(isolate, CodeDeleteEvent(obj->address())); |
| } |
| } |
| |
| |
| void MarkCompactCollector::Initialize() { |
| StaticMarkingVisitor::Initialize(); |
| } |
| |
| |
| bool SlotsBuffer::IsTypedSlot(ObjectSlot slot) { |
| return reinterpret_cast<uintptr_t>(slot) < NUMBER_OF_SLOT_TYPES; |
| } |
| |
| |
| bool SlotsBuffer::AddTo(SlotsBufferAllocator* allocator, |
| SlotsBuffer** buffer_address, |
| SlotType type, |
| Address addr, |
| AdditionMode mode) { |
| SlotsBuffer* buffer = *buffer_address; |
| if (buffer == NULL || !buffer->HasSpaceForTypedSlot()) { |
| if (mode == FAIL_ON_OVERFLOW && ChainLengthThresholdReached(buffer)) { |
| allocator->DeallocateChain(buffer_address); |
| return false; |
| } |
| buffer = allocator->AllocateBuffer(buffer); |
| *buffer_address = buffer; |
| } |
| ASSERT(buffer->HasSpaceForTypedSlot()); |
| buffer->Add(reinterpret_cast<ObjectSlot>(type)); |
| buffer->Add(reinterpret_cast<ObjectSlot>(addr)); |
| return true; |
| } |
| |
| |
| static inline SlotsBuffer::SlotType SlotTypeForRMode(RelocInfo::Mode rmode) { |
| if (RelocInfo::IsCodeTarget(rmode)) { |
| return SlotsBuffer::CODE_TARGET_SLOT; |
| } else if (RelocInfo::IsEmbeddedObject(rmode)) { |
| return SlotsBuffer::EMBEDDED_OBJECT_SLOT; |
| } else if (RelocInfo::IsDebugBreakSlot(rmode)) { |
| return SlotsBuffer::DEBUG_TARGET_SLOT; |
| } else if (RelocInfo::IsJSReturn(rmode)) { |
| return SlotsBuffer::JS_RETURN_SLOT; |
| } |
| UNREACHABLE(); |
| return SlotsBuffer::NUMBER_OF_SLOT_TYPES; |
| } |
| |
| |
| void MarkCompactCollector::RecordRelocSlot(RelocInfo* rinfo, Object* target) { |
| Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target)); |
| if (target_page->IsEvacuationCandidate() && |
| (rinfo->host() == NULL || |
| !ShouldSkipEvacuationSlotRecording(rinfo->host()))) { |
| if (!SlotsBuffer::AddTo(&slots_buffer_allocator_, |
| target_page->slots_buffer_address(), |
| SlotTypeForRMode(rinfo->rmode()), |
| rinfo->pc(), |
| SlotsBuffer::FAIL_ON_OVERFLOW)) { |
| EvictEvacuationCandidate(target_page); |
| } |
| } |
| } |
| |
| |
| void MarkCompactCollector::RecordCodeEntrySlot(Address slot, Code* target) { |
| Page* target_page = Page::FromAddress(reinterpret_cast<Address>(target)); |
| if (target_page->IsEvacuationCandidate() && |
| !ShouldSkipEvacuationSlotRecording(reinterpret_cast<Object**>(slot))) { |
| if (!SlotsBuffer::AddTo(&slots_buffer_allocator_, |
| target_page->slots_buffer_address(), |
| SlotsBuffer::CODE_ENTRY_SLOT, |
| slot, |
| SlotsBuffer::FAIL_ON_OVERFLOW)) { |
| EvictEvacuationCandidate(target_page); |
| } |
| } |
| } |
| |
| |
| static inline SlotsBuffer::SlotType DecodeSlotType( |
| SlotsBuffer::ObjectSlot slot) { |
| return static_cast<SlotsBuffer::SlotType>(reinterpret_cast<intptr_t>(slot)); |
| } |
| |
| |
| void SlotsBuffer::UpdateSlots(Heap* heap) { |
| PointersUpdatingVisitor v(heap); |
| |
| for (int slot_idx = 0; slot_idx < idx_; ++slot_idx) { |
| ObjectSlot slot = slots_[slot_idx]; |
| if (!IsTypedSlot(slot)) { |
| PointersUpdatingVisitor::UpdateSlot(heap, slot); |
| } else { |
| ++slot_idx; |
| ASSERT(slot_idx < idx_); |
| UpdateSlot(&v, |
| DecodeSlotType(slot), |
| reinterpret_cast<Address>(slots_[slot_idx])); |
| } |
| } |
| } |
| |
| |
| void SlotsBuffer::UpdateSlotsWithFilter(Heap* heap) { |
| PointersUpdatingVisitor v(heap); |
| |
| for (int slot_idx = 0; slot_idx < idx_; ++slot_idx) { |
| ObjectSlot slot = slots_[slot_idx]; |
| if (!IsTypedSlot(slot)) { |
| if (!IsOnInvalidatedCodeObject(reinterpret_cast<Address>(slot))) { |
| PointersUpdatingVisitor::UpdateSlot(heap, slot); |
| } |
| } else { |
| ++slot_idx; |
| ASSERT(slot_idx < idx_); |
| Address pc = reinterpret_cast<Address>(slots_[slot_idx]); |
| if (!IsOnInvalidatedCodeObject(pc)) { |
| UpdateSlot(&v, |
| DecodeSlotType(slot), |
| reinterpret_cast<Address>(slots_[slot_idx])); |
| } |
| } |
| } |
| } |
| |
| |
| SlotsBuffer* SlotsBufferAllocator::AllocateBuffer(SlotsBuffer* next_buffer) { |
| return new SlotsBuffer(next_buffer); |
| } |
| |
| |
| void SlotsBufferAllocator::DeallocateBuffer(SlotsBuffer* buffer) { |
| delete buffer; |
| } |
| |
| |
| void SlotsBufferAllocator::DeallocateChain(SlotsBuffer** buffer_address) { |
| SlotsBuffer* buffer = *buffer_address; |
| while (buffer != NULL) { |
| SlotsBuffer* next_buffer = buffer->next(); |
| DeallocateBuffer(buffer); |
| buffer = next_buffer; |
| } |
| *buffer_address = NULL; |
| } |
| |
| |
| } } // namespace v8::internal |