1// Copyright 2012 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
4// met:
5//
6//     * Redistributions of source code must retain the above copyright
7//       notice, this list of conditions and the following disclaimer.
8//     * Redistributions in binary form must reproduce the above
9//       copyright notice, this list of conditions and the following
10//       disclaimer in the documentation and/or other materials provided
11//       with the distribution.
12//     * Neither the name of Google Inc. nor the names of its
13//       contributors may be used to endorse or promote products derived
14//       from this software without specific prior written permission.
15//
16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28#include "v8.h"
29
30#include "incremental-marking.h"
31
32#include "code-stubs.h"
33#include "compilation-cache.h"
34#include "objects-visiting.h"
35#include "objects-visiting-inl.h"
36#include "v8conversions.h"
37
38namespace v8 {
39namespace internal {
40
41
42IncrementalMarking::IncrementalMarking(Heap* heap)
43    : heap_(heap),
44      state_(STOPPED),
45      marking_deque_memory_(NULL),
46      marking_deque_memory_committed_(false),
47      steps_count_(0),
48      steps_took_(0),
49      longest_step_(0.0),
50      old_generation_space_available_at_start_of_incremental_(0),
51      old_generation_space_used_at_start_of_incremental_(0),
52      steps_count_since_last_gc_(0),
53      steps_took_since_last_gc_(0),
54      should_hurry_(false),
55      marking_speed_(0),
56      allocated_(0),
57      no_marking_scope_depth_(0),
58      unscanned_bytes_of_large_object_(0) {
59}
60
61
62void IncrementalMarking::TearDown() {
63  delete marking_deque_memory_;
64}
65
66
67void IncrementalMarking::RecordWriteSlow(HeapObject* obj,
68                                         Object** slot,
69                                         Object* value) {
70  if (BaseRecordWrite(obj, slot, value) && slot != NULL) {
71    MarkBit obj_bit = Marking::MarkBitFrom(obj);
72    if (Marking::IsBlack(obj_bit)) {
73      // Object is not going to be rescanned we need to record the slot.
74      heap_->mark_compact_collector()->RecordSlot(
75          HeapObject::RawField(obj, 0), slot, value);
76    }
77  }
78}
79
80
81void IncrementalMarking::RecordWriteFromCode(HeapObject* obj,
82                                             Object** slot,
83                                             Isolate* isolate) {
84  ASSERT(obj->IsHeapObject());
85  IncrementalMarking* marking = isolate->heap()->incremental_marking();
86  ASSERT(!marking->is_compacting_);
87
88  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
89  int counter = chunk->write_barrier_counter();
90  if (counter < (MemoryChunk::kWriteBarrierCounterGranularity / 2)) {
91    marking->write_barriers_invoked_since_last_step_ +=
92        MemoryChunk::kWriteBarrierCounterGranularity -
93            chunk->write_barrier_counter();
94    chunk->set_write_barrier_counter(
95        MemoryChunk::kWriteBarrierCounterGranularity);
96  }
97
98  marking->RecordWrite(obj, slot, *slot);
99}
100
101
102void IncrementalMarking::RecordWriteForEvacuationFromCode(HeapObject* obj,
103                                                          Object** slot,
104                                                          Isolate* isolate) {
105  ASSERT(obj->IsHeapObject());
106  IncrementalMarking* marking = isolate->heap()->incremental_marking();
107  ASSERT(marking->is_compacting_);
108
109  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
110  int counter = chunk->write_barrier_counter();
111  if (counter < (MemoryChunk::kWriteBarrierCounterGranularity / 2)) {
112    marking->write_barriers_invoked_since_last_step_ +=
113        MemoryChunk::kWriteBarrierCounterGranularity -
114            chunk->write_barrier_counter();
115    chunk->set_write_barrier_counter(
116        MemoryChunk::kWriteBarrierCounterGranularity);
117  }
118
119  marking->RecordWrite(obj, slot, *slot);
120}
121
122
123void IncrementalMarking::RecordCodeTargetPatch(Code* host,
124                                               Address pc,
125                                               HeapObject* value) {
126  if (IsMarking()) {
127    RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
128    RecordWriteIntoCode(host, &rinfo, value);
129  }
130}
131
132
133void IncrementalMarking::RecordCodeTargetPatch(Address pc, HeapObject* value) {
134  if (IsMarking()) {
135    Code* host = heap_->isolate()->inner_pointer_to_code_cache()->
136        GcSafeFindCodeForInnerPointer(pc);
137    RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
138    RecordWriteIntoCode(host, &rinfo, value);
139  }
140}
141
142
143void IncrementalMarking::RecordWriteOfCodeEntrySlow(JSFunction* host,
144                                                    Object** slot,
145                                                    Code* value) {
146  if (BaseRecordWrite(host, slot, value)) {
147    ASSERT(slot != NULL);
148    heap_->mark_compact_collector()->
149        RecordCodeEntrySlot(reinterpret_cast<Address>(slot), value);
150  }
151}
152
153
154void IncrementalMarking::RecordWriteIntoCodeSlow(HeapObject* obj,
155                                                 RelocInfo* rinfo,
156                                                 Object* value) {
157  MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
158  if (Marking::IsWhite(value_bit)) {
159    MarkBit obj_bit = Marking::MarkBitFrom(obj);
160    if (Marking::IsBlack(obj_bit)) {
161      BlackToGreyAndUnshift(obj, obj_bit);
162      RestartIfNotMarking();
163    }
164    // Object is either grey or white.  It will be scanned if survives.
165    return;
166  }
167
168  if (is_compacting_) {
169    MarkBit obj_bit = Marking::MarkBitFrom(obj);
170    if (Marking::IsBlack(obj_bit)) {
171      // Object is not going to be rescanned.  We need to record the slot.
172      heap_->mark_compact_collector()->RecordRelocSlot(rinfo,
173                                                       Code::cast(value));
174    }
175  }
176}
177
178
179static void MarkObjectGreyDoNotEnqueue(Object* obj) {
180  if (obj->IsHeapObject()) {
181    HeapObject* heap_obj = HeapObject::cast(obj);
182    MarkBit mark_bit = Marking::MarkBitFrom(HeapObject::cast(obj));
183    if (Marking::IsBlack(mark_bit)) {
184      MemoryChunk::IncrementLiveBytesFromGC(heap_obj->address(),
185                                            -heap_obj->Size());
186    }
187    Marking::AnyToGrey(mark_bit);
188  }
189}
190
191
192static inline void MarkBlackOrKeepGrey(HeapObject* heap_object,
193                                       MarkBit mark_bit,
194                                       int size) {
195  ASSERT(!Marking::IsImpossible(mark_bit));
196  if (mark_bit.Get()) return;
197  mark_bit.Set();
198  MemoryChunk::IncrementLiveBytesFromGC(heap_object->address(), size);
199  ASSERT(Marking::IsBlack(mark_bit));
200}
201
202
203static inline void MarkBlackOrKeepBlack(HeapObject* heap_object,
204                                        MarkBit mark_bit,
205                                        int size) {
206  ASSERT(!Marking::IsImpossible(mark_bit));
207  if (Marking::IsBlack(mark_bit)) return;
208  Marking::MarkBlack(mark_bit);
209  MemoryChunk::IncrementLiveBytesFromGC(heap_object->address(), size);
210  ASSERT(Marking::IsBlack(mark_bit));
211}
212
213
214class IncrementalMarkingMarkingVisitor
215    : public StaticMarkingVisitor<IncrementalMarkingMarkingVisitor> {
216 public:
217  static void Initialize() {
218    StaticMarkingVisitor<IncrementalMarkingMarkingVisitor>::Initialize();
219    table_.Register(kVisitFixedArray, &VisitFixedArrayIncremental);
220    table_.Register(kVisitNativeContext, &VisitNativeContextIncremental);
221    table_.Register(kVisitJSRegExp, &VisitJSRegExp);
222  }
223
224  static const int kProgressBarScanningChunk = 32 * 1024;
225
226  static void VisitFixedArrayIncremental(Map* map, HeapObject* object) {
227    MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
228    // TODO(mstarzinger): Move setting of the flag to the allocation site of
229    // the array. The visitor should just check the flag.
230    if (FLAG_use_marking_progress_bar &&
231        chunk->owner()->identity() == LO_SPACE) {
232      chunk->SetFlag(MemoryChunk::HAS_PROGRESS_BAR);
233    }
234    if (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR)) {
235      Heap* heap = map->GetHeap();
236      // When using a progress bar for large fixed arrays, scan only a chunk of
237      // the array and try to push it onto the marking deque again until it is
238      // fully scanned. Fall back to scanning it through to the end in case this
239      // fails because of a full deque.
240      int object_size = FixedArray::BodyDescriptor::SizeOf(map, object);
241      int start_offset = Max(FixedArray::BodyDescriptor::kStartOffset,
242                             chunk->progress_bar());
243      int end_offset = Min(object_size,
244                           start_offset + kProgressBarScanningChunk);
245      int already_scanned_offset = start_offset;
246      bool scan_until_end = false;
247      do {
248        VisitPointersWithAnchor(heap,
249                                HeapObject::RawField(object, 0),
250                                HeapObject::RawField(object, start_offset),
251                                HeapObject::RawField(object, end_offset));
252        start_offset = end_offset;
253        end_offset = Min(object_size, end_offset + kProgressBarScanningChunk);
254        scan_until_end = heap->incremental_marking()->marking_deque()->IsFull();
255      } while (scan_until_end && start_offset < object_size);
256      chunk->set_progress_bar(start_offset);
257      if (start_offset < object_size) {
258        heap->incremental_marking()->marking_deque()->UnshiftGrey(object);
259        heap->incremental_marking()->NotifyIncompleteScanOfObject(
260            object_size - (start_offset - already_scanned_offset));
261      }
262    } else {
263      FixedArrayVisitor::Visit(map, object);
264    }
265  }
266
267  static void VisitNativeContextIncremental(Map* map, HeapObject* object) {
268    Context* context = Context::cast(object);
269
270    // We will mark cache black with a separate pass
271    // when we finish marking.
272    MarkObjectGreyDoNotEnqueue(context->normalized_map_cache());
273    VisitNativeContext(map, context);
274  }
275
276  static void VisitWeakCollection(Map* map, HeapObject* object) {
277    Heap* heap = map->GetHeap();
278    VisitPointers(heap,
279                  HeapObject::RawField(object,
280                                       JSWeakCollection::kPropertiesOffset),
281                  HeapObject::RawField(object, JSWeakCollection::kSize));
282  }
283
284  static void BeforeVisitingSharedFunctionInfo(HeapObject* object) {}
285
286  INLINE(static void VisitPointer(Heap* heap, Object** p)) {
287    Object* obj = *p;
288    if (obj->NonFailureIsHeapObject()) {
289      heap->mark_compact_collector()->RecordSlot(p, p, obj);
290      MarkObject(heap, obj);
291    }
292  }
293
294  INLINE(static void VisitPointers(Heap* heap, Object** start, Object** end)) {
295    for (Object** p = start; p < end; p++) {
296      Object* obj = *p;
297      if (obj->NonFailureIsHeapObject()) {
298        heap->mark_compact_collector()->RecordSlot(start, p, obj);
299        MarkObject(heap, obj);
300      }
301    }
302  }
303
304  INLINE(static void VisitPointersWithAnchor(Heap* heap,
305                                             Object** anchor,
306                                             Object** start,
307                                             Object** end)) {
308    for (Object** p = start; p < end; p++) {
309      Object* obj = *p;
310      if (obj->NonFailureIsHeapObject()) {
311        heap->mark_compact_collector()->RecordSlot(anchor, p, obj);
312        MarkObject(heap, obj);
313      }
314    }
315  }
316
317  // Marks the object grey and pushes it on the marking stack.
318  INLINE(static void MarkObject(Heap* heap, Object* obj)) {
319    HeapObject* heap_object = HeapObject::cast(obj);
320    MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
321    if (mark_bit.data_only()) {
322      MarkBlackOrKeepGrey(heap_object, mark_bit, heap_object->Size());
323    } else if (Marking::IsWhite(mark_bit)) {
324      heap->incremental_marking()->WhiteToGreyAndPush(heap_object, mark_bit);
325    }
326  }
327
328  // Marks the object black without pushing it on the marking stack.
329  // Returns true if object needed marking and false otherwise.
330  INLINE(static bool MarkObjectWithoutPush(Heap* heap, Object* obj)) {
331    HeapObject* heap_object = HeapObject::cast(obj);
332    MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
333    if (Marking::IsWhite(mark_bit)) {
334      mark_bit.Set();
335      MemoryChunk::IncrementLiveBytesFromGC(heap_object->address(),
336                                            heap_object->Size());
337      return true;
338    }
339    return false;
340  }
341};
342
343
344class IncrementalMarkingRootMarkingVisitor : public ObjectVisitor {
345 public:
346  explicit IncrementalMarkingRootMarkingVisitor(
347      IncrementalMarking* incremental_marking)
348      : incremental_marking_(incremental_marking) {
349  }
350
351  void VisitPointer(Object** p) {
352    MarkObjectByPointer(p);
353  }
354
355  void VisitPointers(Object** start, Object** end) {
356    for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
357  }
358
359 private:
360  void MarkObjectByPointer(Object** p) {
361    Object* obj = *p;
362    if (!obj->IsHeapObject()) return;
363
364    HeapObject* heap_object = HeapObject::cast(obj);
365    MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
366    if (mark_bit.data_only()) {
367      MarkBlackOrKeepGrey(heap_object, mark_bit, heap_object->Size());
368    } else {
369      if (Marking::IsWhite(mark_bit)) {
370        incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
371      }
372    }
373  }
374
375  IncrementalMarking* incremental_marking_;
376};
377
378
379void IncrementalMarking::Initialize() {
380  IncrementalMarkingMarkingVisitor::Initialize();
381}
382
383
384void IncrementalMarking::SetOldSpacePageFlags(MemoryChunk* chunk,
385                                              bool is_marking,
386                                              bool is_compacting) {
387  if (is_marking) {
388    chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
389    chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
390
391    // It's difficult to filter out slots recorded for large objects.
392    if (chunk->owner()->identity() == LO_SPACE &&
393        chunk->size() > static_cast<size_t>(Page::kPageSize) &&
394        is_compacting) {
395      chunk->SetFlag(MemoryChunk::RESCAN_ON_EVACUATION);
396    }
397  } else if (chunk->owner()->identity() == CELL_SPACE ||
398             chunk->owner()->identity() == PROPERTY_CELL_SPACE ||
399             chunk->scan_on_scavenge()) {
400    chunk->ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
401    chunk->ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
402  } else {
403    chunk->ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
404    chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
405  }
406}
407
408
409void IncrementalMarking::SetNewSpacePageFlags(NewSpacePage* chunk,
410                                              bool is_marking) {
411  chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
412  if (is_marking) {
413    chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
414  } else {
415    chunk->ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
416  }
417  chunk->SetFlag(MemoryChunk::SCAN_ON_SCAVENGE);
418}
419
420
421void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
422    PagedSpace* space) {
423  PageIterator it(space);
424  while (it.has_next()) {
425    Page* p = it.next();
426    SetOldSpacePageFlags(p, false, false);
427  }
428}
429
430
431void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
432    NewSpace* space) {
433  NewSpacePageIterator it(space);
434  while (it.has_next()) {
435    NewSpacePage* p = it.next();
436    SetNewSpacePageFlags(p, false);
437  }
438}
439
440
441void IncrementalMarking::DeactivateIncrementalWriteBarrier() {
442  DeactivateIncrementalWriteBarrierForSpace(heap_->old_pointer_space());
443  DeactivateIncrementalWriteBarrierForSpace(heap_->old_data_space());
444  DeactivateIncrementalWriteBarrierForSpace(heap_->cell_space());
445  DeactivateIncrementalWriteBarrierForSpace(heap_->property_cell_space());
446  DeactivateIncrementalWriteBarrierForSpace(heap_->map_space());
447  DeactivateIncrementalWriteBarrierForSpace(heap_->code_space());
448  DeactivateIncrementalWriteBarrierForSpace(heap_->new_space());
449
450  LargePage* lop = heap_->lo_space()->first_page();
451  while (lop->is_valid()) {
452    SetOldSpacePageFlags(lop, false, false);
453    lop = lop->next_page();
454  }
455}
456
457
458void IncrementalMarking::ActivateIncrementalWriteBarrier(PagedSpace* space) {
459  PageIterator it(space);
460  while (it.has_next()) {
461    Page* p = it.next();
462    SetOldSpacePageFlags(p, true, is_compacting_);
463  }
464}
465
466
467void IncrementalMarking::ActivateIncrementalWriteBarrier(NewSpace* space) {
468  NewSpacePageIterator it(space->ToSpaceStart(), space->ToSpaceEnd());
469  while (it.has_next()) {
470    NewSpacePage* p = it.next();
471    SetNewSpacePageFlags(p, true);
472  }
473}
474
475
476void IncrementalMarking::ActivateIncrementalWriteBarrier() {
477  ActivateIncrementalWriteBarrier(heap_->old_pointer_space());
478  ActivateIncrementalWriteBarrier(heap_->old_data_space());
479  ActivateIncrementalWriteBarrier(heap_->cell_space());
480  ActivateIncrementalWriteBarrier(heap_->property_cell_space());
481  ActivateIncrementalWriteBarrier(heap_->map_space());
482  ActivateIncrementalWriteBarrier(heap_->code_space());
483  ActivateIncrementalWriteBarrier(heap_->new_space());
484
485  LargePage* lop = heap_->lo_space()->first_page();
486  while (lop->is_valid()) {
487    SetOldSpacePageFlags(lop, true, is_compacting_);
488    lop = lop->next_page();
489  }
490}
491
492
493bool IncrementalMarking::WorthActivating() {
494#ifndef DEBUG
495  static const intptr_t kActivationThreshold = 8 * MB;
496#else
497  // TODO(gc) consider setting this to some low level so that some
498  // debug tests run with incremental marking and some without.
499  static const intptr_t kActivationThreshold = 0;
500#endif
501  // Only start incremental marking in a safe state: 1) when expose GC is
502  // deactivated, 2) when incremental marking is turned on, 3) when we are
503  // currently not in a GC, and 4) when we are currently not serializing
504  // or deserializing the heap.
505  return !FLAG_expose_gc &&
506      FLAG_incremental_marking &&
507      FLAG_incremental_marking_steps &&
508      heap_->gc_state() == Heap::NOT_IN_GC &&
509      !Serializer::enabled() &&
510      heap_->isolate()->IsInitialized() &&
511      heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
512}
513
514
515void IncrementalMarking::ActivateGeneratedStub(Code* stub) {
516  ASSERT(RecordWriteStub::GetMode(stub) ==
517         RecordWriteStub::STORE_BUFFER_ONLY);
518
519  if (!IsMarking()) {
520    // Initially stub is generated in STORE_BUFFER_ONLY mode thus
521    // we don't need to do anything if incremental marking is
522    // not active.
523  } else if (IsCompacting()) {
524    RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL_COMPACTION);
525  } else {
526    RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL);
527  }
528}
529
530
531static void PatchIncrementalMarkingRecordWriteStubs(
532    Heap* heap, RecordWriteStub::Mode mode) {
533  UnseededNumberDictionary* stubs = heap->code_stubs();
534
535  int capacity = stubs->Capacity();
536  for (int i = 0; i < capacity; i++) {
537    Object* k = stubs->KeyAt(i);
538    if (stubs->IsKey(k)) {
539      uint32_t key = NumberToUint32(k);
540
541      if (CodeStub::MajorKeyFromKey(key) ==
542          CodeStub::RecordWrite) {
543        Object* e = stubs->ValueAt(i);
544        if (e->IsCode()) {
545          RecordWriteStub::Patch(Code::cast(e), mode);
546        }
547      }
548    }
549  }
550}
551
552
553void IncrementalMarking::EnsureMarkingDequeIsCommitted() {
554  if (marking_deque_memory_ == NULL) {
555    marking_deque_memory_ = new VirtualMemory(4 * MB);
556  }
557  if (!marking_deque_memory_committed_) {
558    bool success = marking_deque_memory_->Commit(
559        reinterpret_cast<Address>(marking_deque_memory_->address()),
560        marking_deque_memory_->size(),
561        false);  // Not executable.
562    CHECK(success);
563    marking_deque_memory_committed_ = true;
564  }
565}
566
567
568void IncrementalMarking::UncommitMarkingDeque() {
569  if (state_ == STOPPED && marking_deque_memory_committed_) {
570    bool success = marking_deque_memory_->Uncommit(
571        reinterpret_cast<Address>(marking_deque_memory_->address()),
572        marking_deque_memory_->size());
573    CHECK(success);
574    marking_deque_memory_committed_ = false;
575  }
576}
577
578
579void IncrementalMarking::Start(CompactionFlag flag) {
580  if (FLAG_trace_incremental_marking) {
581    PrintF("[IncrementalMarking] Start\n");
582  }
583  ASSERT(FLAG_incremental_marking);
584  ASSERT(FLAG_incremental_marking_steps);
585  ASSERT(state_ == STOPPED);
586  ASSERT(heap_->gc_state() == Heap::NOT_IN_GC);
587  ASSERT(!Serializer::enabled());
588  ASSERT(heap_->isolate()->IsInitialized());
589
590  ResetStepCounters();
591
592  if (heap_->IsSweepingComplete()) {
593    StartMarking(flag);
594  } else {
595    if (FLAG_trace_incremental_marking) {
596      PrintF("[IncrementalMarking] Start sweeping.\n");
597    }
598    state_ = SWEEPING;
599  }
600
601  heap_->new_space()->LowerInlineAllocationLimit(kAllocatedThreshold);
602}
603
604
605void IncrementalMarking::StartMarking(CompactionFlag flag) {
606  if (FLAG_trace_incremental_marking) {
607    PrintF("[IncrementalMarking] Start marking\n");
608  }
609
610  is_compacting_ = !FLAG_never_compact && (flag == ALLOW_COMPACTION) &&
611      heap_->mark_compact_collector()->StartCompaction(
612          MarkCompactCollector::INCREMENTAL_COMPACTION);
613
614  state_ = MARKING;
615
616  RecordWriteStub::Mode mode = is_compacting_ ?
617      RecordWriteStub::INCREMENTAL_COMPACTION : RecordWriteStub::INCREMENTAL;
618
619  PatchIncrementalMarkingRecordWriteStubs(heap_, mode);
620
621  EnsureMarkingDequeIsCommitted();
622
623  // Initialize marking stack.
624  Address addr = static_cast<Address>(marking_deque_memory_->address());
625  size_t size = marking_deque_memory_->size();
626  if (FLAG_force_marking_deque_overflows) size = 64 * kPointerSize;
627  marking_deque_.Initialize(addr, addr + size);
628
629  ActivateIncrementalWriteBarrier();
630
631  // Marking bits are cleared by the sweeper.
632#ifdef VERIFY_HEAP
633  if (FLAG_verify_heap) {
634    heap_->mark_compact_collector()->VerifyMarkbitsAreClean();
635  }
636#endif
637
638  heap_->CompletelyClearInstanceofCache();
639  heap_->isolate()->compilation_cache()->MarkCompactPrologue();
640
641  if (FLAG_cleanup_code_caches_at_gc) {
642    // We will mark cache black with a separate pass
643    // when we finish marking.
644    MarkObjectGreyDoNotEnqueue(heap_->polymorphic_code_cache());
645  }
646
647  // Mark strong roots grey.
648  IncrementalMarkingRootMarkingVisitor visitor(this);
649  heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
650
651  heap_->mark_compact_collector()->MarkWeakObjectToCodeTable();
652
653  // Ready to start incremental marking.
654  if (FLAG_trace_incremental_marking) {
655    PrintF("[IncrementalMarking] Running\n");
656  }
657}
658
659
660void IncrementalMarking::PrepareForScavenge() {
661  if (!IsMarking()) return;
662  NewSpacePageIterator it(heap_->new_space()->FromSpaceStart(),
663                          heap_->new_space()->FromSpaceEnd());
664  while (it.has_next()) {
665    Bitmap::Clear(it.next());
666  }
667}
668
669
670void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
671  if (!IsMarking()) return;
672
673  int current = marking_deque_.bottom();
674  int mask = marking_deque_.mask();
675  int limit = marking_deque_.top();
676  HeapObject** array = marking_deque_.array();
677  int new_top = current;
678
679  Map* filler_map = heap_->one_pointer_filler_map();
680
681  while (current != limit) {
682    HeapObject* obj = array[current];
683    ASSERT(obj->IsHeapObject());
684    current = ((current + 1) & mask);
685    if (heap_->InNewSpace(obj)) {
686      MapWord map_word = obj->map_word();
687      if (map_word.IsForwardingAddress()) {
688        HeapObject* dest = map_word.ToForwardingAddress();
689        array[new_top] = dest;
690        new_top = ((new_top + 1) & mask);
691        ASSERT(new_top != marking_deque_.bottom());
692#ifdef DEBUG
693        MarkBit mark_bit = Marking::MarkBitFrom(obj);
694        ASSERT(Marking::IsGrey(mark_bit) ||
695               (obj->IsFiller() && Marking::IsWhite(mark_bit)));
696#endif
697      }
698    } else if (obj->map() != filler_map) {
699      // Skip one word filler objects that appear on the
700      // stack when we perform in place array shift.
701      array[new_top] = obj;
702      new_top = ((new_top + 1) & mask);
703      ASSERT(new_top != marking_deque_.bottom());
704#ifdef DEBUG
705        MarkBit mark_bit = Marking::MarkBitFrom(obj);
706        MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
707        ASSERT(Marking::IsGrey(mark_bit) ||
708               (obj->IsFiller() && Marking::IsWhite(mark_bit)) ||
709               (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR) &&
710                Marking::IsBlack(mark_bit)));
711#endif
712    }
713  }
714  marking_deque_.set_top(new_top);
715
716  steps_took_since_last_gc_ = 0;
717  steps_count_since_last_gc_ = 0;
718  longest_step_ = 0.0;
719}
720
721
722void IncrementalMarking::VisitObject(Map* map, HeapObject* obj, int size) {
723  MarkBit map_mark_bit = Marking::MarkBitFrom(map);
724  if (Marking::IsWhite(map_mark_bit)) {
725    WhiteToGreyAndPush(map, map_mark_bit);
726  }
727
728  IncrementalMarkingMarkingVisitor::IterateBody(map, obj);
729
730  MarkBit mark_bit = Marking::MarkBitFrom(obj);
731#if ENABLE_SLOW_ASSERTS
732  MemoryChunk* chunk = MemoryChunk::FromAddress(obj->address());
733  SLOW_ASSERT(Marking::IsGrey(mark_bit) ||
734              (obj->IsFiller() && Marking::IsWhite(mark_bit)) ||
735              (chunk->IsFlagSet(MemoryChunk::HAS_PROGRESS_BAR) &&
736               Marking::IsBlack(mark_bit)));
737#endif
738  MarkBlackOrKeepBlack(obj, mark_bit, size);
739}
740
741
742void IncrementalMarking::ProcessMarkingDeque(intptr_t bytes_to_process) {
743  Map* filler_map = heap_->one_pointer_filler_map();
744  while (!marking_deque_.IsEmpty() && bytes_to_process > 0) {
745    HeapObject* obj = marking_deque_.Pop();
746
747    // Explicitly skip one word fillers. Incremental markbit patterns are
748    // correct only for objects that occupy at least two words.
749    Map* map = obj->map();
750    if (map == filler_map) continue;
751
752    int size = obj->SizeFromMap(map);
753    unscanned_bytes_of_large_object_ = 0;
754    VisitObject(map, obj, size);
755    bytes_to_process -= (size - unscanned_bytes_of_large_object_);
756  }
757}
758
759
760void IncrementalMarking::ProcessMarkingDeque() {
761  Map* filler_map = heap_->one_pointer_filler_map();
762  while (!marking_deque_.IsEmpty()) {
763    HeapObject* obj = marking_deque_.Pop();
764
765    // Explicitly skip one word fillers. Incremental markbit patterns are
766    // correct only for objects that occupy at least two words.
767    Map* map = obj->map();
768    if (map == filler_map) continue;
769
770    VisitObject(map, obj, obj->SizeFromMap(map));
771  }
772}
773
774
775void IncrementalMarking::Hurry() {
776  if (state() == MARKING) {
777    double start = 0.0;
778    if (FLAG_trace_incremental_marking || FLAG_print_cumulative_gc_stat) {
779      start = OS::TimeCurrentMillis();
780      if (FLAG_trace_incremental_marking) {
781        PrintF("[IncrementalMarking] Hurry\n");
782      }
783    }
784    // TODO(gc) hurry can mark objects it encounters black as mutator
785    // was stopped.
786    ProcessMarkingDeque();
787    state_ = COMPLETE;
788    if (FLAG_trace_incremental_marking || FLAG_print_cumulative_gc_stat) {
789      double end = OS::TimeCurrentMillis();
790      double delta = end - start;
791      heap_->AddMarkingTime(delta);
792      if (FLAG_trace_incremental_marking) {
793        PrintF("[IncrementalMarking] Complete (hurry), spent %d ms.\n",
794               static_cast<int>(delta));
795      }
796    }
797  }
798
799  if (FLAG_cleanup_code_caches_at_gc) {
800    PolymorphicCodeCache* poly_cache = heap_->polymorphic_code_cache();
801    Marking::GreyToBlack(Marking::MarkBitFrom(poly_cache));
802    MemoryChunk::IncrementLiveBytesFromGC(poly_cache->address(),
803                                          PolymorphicCodeCache::kSize);
804  }
805
806  Object* context = heap_->native_contexts_list();
807  while (!context->IsUndefined()) {
808    // GC can happen when the context is not fully initialized,
809    // so the cache can be undefined.
810    HeapObject* cache = HeapObject::cast(
811        Context::cast(context)->get(Context::NORMALIZED_MAP_CACHE_INDEX));
812    if (!cache->IsUndefined()) {
813      MarkBit mark_bit = Marking::MarkBitFrom(cache);
814      if (Marking::IsGrey(mark_bit)) {
815        Marking::GreyToBlack(mark_bit);
816        MemoryChunk::IncrementLiveBytesFromGC(cache->address(), cache->Size());
817      }
818    }
819    context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
820  }
821}
822
823
824void IncrementalMarking::Abort() {
825  if (IsStopped()) return;
826  if (FLAG_trace_incremental_marking) {
827    PrintF("[IncrementalMarking] Aborting.\n");
828  }
829  heap_->new_space()->LowerInlineAllocationLimit(0);
830  IncrementalMarking::set_should_hurry(false);
831  ResetStepCounters();
832  if (IsMarking()) {
833    PatchIncrementalMarkingRecordWriteStubs(heap_,
834                                            RecordWriteStub::STORE_BUFFER_ONLY);
835    DeactivateIncrementalWriteBarrier();
836
837    if (is_compacting_) {
838      LargeObjectIterator it(heap_->lo_space());
839      for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
840        Page* p = Page::FromAddress(obj->address());
841        if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
842          p->ClearFlag(Page::RESCAN_ON_EVACUATION);
843        }
844      }
845    }
846  }
847  heap_->isolate()->stack_guard()->Continue(GC_REQUEST);
848  state_ = STOPPED;
849  is_compacting_ = false;
850}
851
852
853void IncrementalMarking::Finalize() {
854  Hurry();
855  state_ = STOPPED;
856  is_compacting_ = false;
857  heap_->new_space()->LowerInlineAllocationLimit(0);
858  IncrementalMarking::set_should_hurry(false);
859  ResetStepCounters();
860  PatchIncrementalMarkingRecordWriteStubs(heap_,
861                                          RecordWriteStub::STORE_BUFFER_ONLY);
862  DeactivateIncrementalWriteBarrier();
863  ASSERT(marking_deque_.IsEmpty());
864  heap_->isolate()->stack_guard()->Continue(GC_REQUEST);
865}
866
867
868void IncrementalMarking::MarkingComplete(CompletionAction action) {
869  state_ = COMPLETE;
870  // We will set the stack guard to request a GC now.  This will mean the rest
871  // of the GC gets performed as soon as possible (we can't do a GC here in a
872  // record-write context).  If a few things get allocated between now and then
873  // that shouldn't make us do a scavenge and keep being incremental, so we set
874  // the should-hurry flag to indicate that there can't be much work left to do.
875  set_should_hurry(true);
876  if (FLAG_trace_incremental_marking) {
877    PrintF("[IncrementalMarking] Complete (normal).\n");
878  }
879  if (action == GC_VIA_STACK_GUARD) {
880    heap_->isolate()->stack_guard()->RequestGC();
881  }
882}
883
884
885void IncrementalMarking::OldSpaceStep(intptr_t allocated) {
886  if (IsStopped() && WorthActivating() && heap_->NextGCIsLikelyToBeFull()) {
887    // TODO(hpayer): Let's play safe for now, but compaction should be
888    // in principle possible.
889    Start(PREVENT_COMPACTION);
890  } else {
891    Step(allocated * kFastMarking / kInitialMarkingSpeed, GC_VIA_STACK_GUARD);
892  }
893}
894
895
896void IncrementalMarking::Step(intptr_t allocated_bytes,
897                              CompletionAction action) {
898  if (heap_->gc_state() != Heap::NOT_IN_GC ||
899      !FLAG_incremental_marking ||
900      !FLAG_incremental_marking_steps ||
901      (state_ != SWEEPING && state_ != MARKING)) {
902    return;
903  }
904
905  allocated_ += allocated_bytes;
906
907  if (allocated_ < kAllocatedThreshold &&
908      write_barriers_invoked_since_last_step_ <
909          kWriteBarriersInvokedThreshold) {
910    return;
911  }
912
913  if (state_ == MARKING && no_marking_scope_depth_ > 0) return;
914
915  // The marking speed is driven either by the allocation rate or by the rate
916  // at which we are having to check the color of objects in the write barrier.
917  // It is possible for a tight non-allocating loop to run a lot of write
918  // barriers before we get here and check them (marking can only take place on
919  // allocation), so to reduce the lumpiness we don't use the write barriers
920  // invoked since last step directly to determine the amount of work to do.
921  intptr_t bytes_to_process =
922      marking_speed_ * Max(allocated_, write_barriers_invoked_since_last_step_);
923  allocated_ = 0;
924  write_barriers_invoked_since_last_step_ = 0;
925
926  bytes_scanned_ += bytes_to_process;
927
928  double start = 0;
929
930  if (FLAG_trace_incremental_marking || FLAG_trace_gc ||
931      FLAG_print_cumulative_gc_stat) {
932    start = OS::TimeCurrentMillis();
933  }
934
935  if (state_ == SWEEPING) {
936    if (heap_->EnsureSweepersProgressed(static_cast<int>(bytes_to_process))) {
937      bytes_scanned_ = 0;
938      StartMarking(PREVENT_COMPACTION);
939    }
940  } else if (state_ == MARKING) {
941    ProcessMarkingDeque(bytes_to_process);
942    if (marking_deque_.IsEmpty()) MarkingComplete(action);
943  }
944
945  steps_count_++;
946  steps_count_since_last_gc_++;
947
948  bool speed_up = false;
949
950  if ((steps_count_ % kMarkingSpeedAccellerationInterval) == 0) {
951    if (FLAG_trace_gc) {
952      PrintPID("Speed up marking after %d steps\n",
953               static_cast<int>(kMarkingSpeedAccellerationInterval));
954    }
955    speed_up = true;
956  }
957
958  bool space_left_is_very_small =
959      (old_generation_space_available_at_start_of_incremental_ < 10 * MB);
960
961  bool only_1_nth_of_space_that_was_available_still_left =
962      (SpaceLeftInOldSpace() * (marking_speed_ + 1) <
963          old_generation_space_available_at_start_of_incremental_);
964
965  if (space_left_is_very_small ||
966      only_1_nth_of_space_that_was_available_still_left) {
967    if (FLAG_trace_gc) PrintPID("Speed up marking because of low space left\n");
968    speed_up = true;
969  }
970
971  bool size_of_old_space_multiplied_by_n_during_marking =
972      (heap_->PromotedTotalSize() >
973       (marking_speed_ + 1) *
974           old_generation_space_used_at_start_of_incremental_);
975  if (size_of_old_space_multiplied_by_n_during_marking) {
976    speed_up = true;
977    if (FLAG_trace_gc) {
978      PrintPID("Speed up marking because of heap size increase\n");
979    }
980  }
981
982  int64_t promoted_during_marking = heap_->PromotedTotalSize()
983      - old_generation_space_used_at_start_of_incremental_;
984  intptr_t delay = marking_speed_ * MB;
985  intptr_t scavenge_slack = heap_->MaxSemiSpaceSize();
986
987  // We try to scan at at least twice the speed that we are allocating.
988  if (promoted_during_marking > bytes_scanned_ / 2 + scavenge_slack + delay) {
989    if (FLAG_trace_gc) {
990      PrintPID("Speed up marking because marker was not keeping up\n");
991    }
992    speed_up = true;
993  }
994
995  if (speed_up) {
996    if (state_ != MARKING) {
997      if (FLAG_trace_gc) {
998        PrintPID("Postponing speeding up marking until marking starts\n");
999      }
1000    } else {
1001      marking_speed_ += kMarkingSpeedAccelleration;
1002      marking_speed_ = static_cast<int>(
1003          Min(kMaxMarkingSpeed,
1004              static_cast<intptr_t>(marking_speed_ * 1.3)));
1005      if (FLAG_trace_gc) {
1006        PrintPID("Marking speed increased to %d\n", marking_speed_);
1007      }
1008    }
1009  }
1010
1011  if (FLAG_trace_incremental_marking || FLAG_trace_gc ||
1012      FLAG_print_cumulative_gc_stat) {
1013    double end = OS::TimeCurrentMillis();
1014    double delta = (end - start);
1015    longest_step_ = Max(longest_step_, delta);
1016    steps_took_ += delta;
1017    steps_took_since_last_gc_ += delta;
1018    heap_->AddMarkingTime(delta);
1019  }
1020}
1021
1022
1023void IncrementalMarking::ResetStepCounters() {
1024  steps_count_ = 0;
1025  steps_took_ = 0;
1026  longest_step_ = 0.0;
1027  old_generation_space_available_at_start_of_incremental_ =
1028      SpaceLeftInOldSpace();
1029  old_generation_space_used_at_start_of_incremental_ =
1030      heap_->PromotedTotalSize();
1031  steps_count_since_last_gc_ = 0;
1032  steps_took_since_last_gc_ = 0;
1033  bytes_rescanned_ = 0;
1034  marking_speed_ = kInitialMarkingSpeed;
1035  bytes_scanned_ = 0;
1036  write_barriers_invoked_since_last_step_ = 0;
1037}
1038
1039
1040int64_t IncrementalMarking::SpaceLeftInOldSpace() {
1041  return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
1042}
1043
1044} }  // namespace v8::internal
1045