src/3rdparty/v8/src/incremental-marking.cc

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  27
  28 #include "v8.h"
  29
  30 #include "incremental-marking.h"
  31
  32 #include "code-stubs.h"
  33 #include "compilation-cache.h"
  34 #include "v8conversions.h"
  35
  36 namespace v8 {
  37 namespace internal {
  38
  39
  40 IncrementalMarking::IncrementalMarking(Heap* heap)
  41     : heap_(heap),
  42       state_(STOPPED),
  43       marking_deque_memory_(NULL),
  44       marking_deque_memory_committed_(false),
  45       marker_(this, heap->mark_compact_collector()),
  46       steps_count_(0),
  47       steps_took_(0),
  48       longest_step_(0.0),
  49       old_generation_space_available_at_start_of_incremental_(0),
  50       old_generation_space_used_at_start_of_incremental_(0),
  51       steps_count_since_last_gc_(0),
  52       steps_took_since_last_gc_(0),
  53       should_hurry_(false),
  54       allocation_marking_factor_(0),
  55       allocated_(0),
  56       no_marking_scope_depth_(0) {
  57 }
  58
  59
  60 void IncrementalMarking::TearDown() {
  61   delete marking_deque_memory_;
  62 }
  63
  64
  65 void IncrementalMarking::RecordWriteSlow(HeapObject* obj,
  66                                          Object** slot,
  67                                          Object* value) {
  68   if (BaseRecordWrite(obj, slot, value) && is_compacting_ && slot != NULL) {
  69     MarkBit obj_bit = Marking::MarkBitFrom(obj);
  70     if (Marking::IsBlack(obj_bit)) {
  71       // Object is not going to be rescanned we need to record the slot.
  72       heap_->mark_compact_collector()->RecordSlot(
  73           HeapObject::RawField(obj, 0), slot, value);
  74     }
  75   }
  76 }
  77
  78
  79 void IncrementalMarking::RecordWriteFromCode(HeapObject* obj,
  80                                              Object* value,
  81                                              Isolate* isolate) {
  82   ASSERT(obj->IsHeapObject());
  83
  84   // Fast cases should already be covered by RecordWriteStub.
  85   ASSERT(value->IsHeapObject());
  86   ASSERT(!value->IsHeapNumber());
  87   ASSERT(!value->IsString() ||
  88          value->IsConsString() ||
  89          value->IsSlicedString());
  90   ASSERT(Marking::IsWhite(Marking::MarkBitFrom(HeapObject::cast(value))));
  91
  92   IncrementalMarking* marking = isolate->heap()->incremental_marking();
  93   ASSERT(!marking->is_compacting_);
  94   marking->RecordWrite(obj, NULL, value);
  95 }
  96
  97
  98 void IncrementalMarking::RecordWriteForEvacuationFromCode(HeapObject* obj,
  99                                                           Object** slot,
 100                                                           Isolate* isolate) {
 101   IncrementalMarking* marking = isolate->heap()->incremental_marking();
 102   ASSERT(marking->is_compacting_);
 103   marking->RecordWrite(obj, slot, *slot);
 104 }
 105
 106
 107 void IncrementalMarking::RecordCodeTargetPatch(Code* host,
 108                                                Address pc,
 109                                                HeapObject* value) {
 110   if (IsMarking()) {
 111     RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
 112     RecordWriteIntoCode(host, &rinfo, value);
 113   }
 114 }
 115
 116
 117 void IncrementalMarking::RecordCodeTargetPatch(Address pc, HeapObject* value) {
 118   if (IsMarking()) {
 119     Code* host = heap_->isolate()->inner_pointer_to_code_cache()->
 120         GcSafeFindCodeForInnerPointer(pc);
 121     RelocInfo rinfo(pc, RelocInfo::CODE_TARGET, 0, host);
 122     RecordWriteIntoCode(host, &rinfo, value);
 123   }
 124 }
 125
 126
 127 void IncrementalMarking::RecordWriteOfCodeEntrySlow(JSFunction* host,
 128                                                 Object** slot,
 129                                                 Code* value) {
 130   if (BaseRecordWrite(host, slot, value) && is_compacting_) {
 131     ASSERT(slot != NULL);
 132     heap_->mark_compact_collector()->
 133         RecordCodeEntrySlot(reinterpret_cast<Address>(slot), value);
 134   }
 135 }
 136
 137
 138 void IncrementalMarking::RecordWriteIntoCodeSlow(HeapObject* obj,
 139                                                  RelocInfo* rinfo,
 140                                                  Object* value) {
 141   MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
 142   if (Marking::IsWhite(value_bit)) {
 143     MarkBit obj_bit = Marking::MarkBitFrom(obj);
 144     if (Marking::IsBlack(obj_bit)) {
 145       BlackToGreyAndUnshift(obj, obj_bit);
 146       RestartIfNotMarking();
 147     }
 148     // Object is either grey or white.  It will be scanned if survives.
 149     return;
 150   }
 151
 152   if (is_compacting_) {
 153     MarkBit obj_bit = Marking::MarkBitFrom(obj);
 154     if (Marking::IsBlack(obj_bit)) {
 155       // Object is not going to be rescanned.  We need to record the slot.
 156       heap_->mark_compact_collector()->RecordRelocSlot(rinfo,
 157                                                        Code::cast(value));
 158     }
 159   }
 160 }
 161
 162
 163 class IncrementalMarkingMarkingVisitor : public ObjectVisitor {
 164  public:
 165   IncrementalMarkingMarkingVisitor(Heap* heap,
 166                                    IncrementalMarking* incremental_marking)
 167       : heap_(heap),
 168         incremental_marking_(incremental_marking) {
 169   }
 170
 171   void VisitEmbeddedPointer(RelocInfo* rinfo) {
 172     ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
 173     Object* target = rinfo->target_object();
 174     if (target->NonFailureIsHeapObject()) {
 175       heap_->mark_compact_collector()->RecordRelocSlot(rinfo, target);
 176       MarkObject(target);
 177     }
 178   }
 179
 180   void VisitCodeTarget(RelocInfo* rinfo) {
 181     ASSERT(RelocInfo::IsCodeTarget(rinfo->rmode()));
 182     Code* target = Code::GetCodeFromTargetAddress(rinfo->target_address());
 183     if (FLAG_cleanup_code_caches_at_gc && target->is_inline_cache_stub()
 184         && (target->ic_age() != heap_->global_ic_age())) {
 185       IC::Clear(rinfo->pc());
 186       target = Code::GetCodeFromTargetAddress(rinfo->target_address());
 187     }
 188     heap_->mark_compact_collector()->RecordRelocSlot(rinfo, Code::cast(target));
 189     MarkObject(target);
 190   }
 191
 192   void VisitDebugTarget(RelocInfo* rinfo) {
 193     ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) &&
 194             rinfo->IsPatchedReturnSequence()) ||
 195            (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) &&
 196             rinfo->IsPatchedDebugBreakSlotSequence()));
 197     Object* target = Code::GetCodeFromTargetAddress(rinfo->call_address());
 198     heap_->mark_compact_collector()->RecordRelocSlot(rinfo, Code::cast(target));
 199     MarkObject(target);
 200   }
 201
 202   void VisitCodeEntry(Address entry_address) {
 203     Object* target = Code::GetObjectFromEntryAddress(entry_address);
 204     heap_->mark_compact_collector()->
 205         RecordCodeEntrySlot(entry_address, Code::cast(target));
 206     MarkObject(target);
 207   }
 208
 209   void VisitSharedFunctionInfo(SharedFunctionInfo* shared) {
 210     if (shared->ic_age() != heap_->global_ic_age()) {
 211       shared->ResetForNewContext(heap_->global_ic_age());
 212     }
 213   }
 214
 215   void VisitPointer(Object** p) {
 216     Object* obj = *p;
 217     if (obj->NonFailureIsHeapObject()) {
 218       heap_->mark_compact_collector()->RecordSlot(p, p, obj);
 219       MarkObject(obj);
 220     }
 221   }
 222
 223   void VisitPointers(Object** start, Object** end) {
 224     for (Object** p = start; p < end; p++) {
 225       Object* obj = *p;
 226       if (obj->NonFailureIsHeapObject()) {
 227         heap_->mark_compact_collector()->RecordSlot(start, p, obj);
 228         MarkObject(obj);
 229       }
 230     }
 231   }
 232
 233  private:
 234   // Mark object pointed to by p.
 235   INLINE(void MarkObject(Object* obj)) {
 236     HeapObject* heap_object = HeapObject::cast(obj);
 237     MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
 238     if (mark_bit.data_only()) {
 239       if (incremental_marking_->MarkBlackOrKeepGrey(mark_bit)) {
 240         MemoryChunk::IncrementLiveBytesFromGC(heap_object->address(),
 241                                               heap_object->Size());
 242       }
 243     } else if (Marking::IsWhite(mark_bit)) {
 244       incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
 245     }
 246   }
 247
 248   Heap* heap_;
 249   IncrementalMarking* incremental_marking_;
 250 };
 251
 252
 253 class IncrementalMarkingRootMarkingVisitor : public ObjectVisitor {
 254  public:
 255   IncrementalMarkingRootMarkingVisitor(Heap* heap,
 256                                        IncrementalMarking* incremental_marking)
 257       : heap_(heap),
 258         incremental_marking_(incremental_marking) {
 259   }
 260
 261   void VisitPointer(Object** p) {
 262     MarkObjectByPointer(p);
 263   }
 264
 265   void VisitPointers(Object** start, Object** end) {
 266     for (Object** p = start; p < end; p++) MarkObjectByPointer(p);
 267   }
 268
 269  private:
 270   void MarkObjectByPointer(Object** p) {
 271     Object* obj = *p;
 272     if (!obj->IsHeapObject()) return;
 273
 274     HeapObject* heap_object = HeapObject::cast(obj);
 275     MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
 276     if (mark_bit.data_only()) {
 277       if (incremental_marking_->MarkBlackOrKeepGrey(mark_bit)) {
 278           MemoryChunk::IncrementLiveBytesFromGC(heap_object->address(),
 279                                                 heap_object->Size());
 280       }
 281     } else {
 282       if (Marking::IsWhite(mark_bit)) {
 283         incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
 284       }
 285     }
 286   }
 287
 288   Heap* heap_;
 289   IncrementalMarking* incremental_marking_;
 290 };
 291
 292
 293 void IncrementalMarking::SetOldSpacePageFlags(MemoryChunk* chunk,
 294                                               bool is_marking,
 295                                               bool is_compacting) {
 296   if (is_marking) {
 297     chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
 298     chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 299
 300     // It's difficult to filter out slots recorded for large objects.
 301     if (chunk->owner()->identity() == LO_SPACE &&
 302         chunk->size() > static_cast<size_t>(Page::kPageSize) &&
 303         is_compacting) {
 304       chunk->SetFlag(MemoryChunk::RESCAN_ON_EVACUATION);
 305     }
 306   } else if (chunk->owner()->identity() == CELL_SPACE ||
 307              chunk->scan_on_scavenge()) {
 308     chunk->ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
 309     chunk->ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 310   } else {
 311     chunk->ClearFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
 312     chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 313   }
 314 }
 315
 316
 317 void IncrementalMarking::SetNewSpacePageFlags(NewSpacePage* chunk,
 318                                               bool is_marking) {
 319   chunk->SetFlag(MemoryChunk::POINTERS_TO_HERE_ARE_INTERESTING);
 320   if (is_marking) {
 321     chunk->SetFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 322   } else {
 323     chunk->ClearFlag(MemoryChunk::POINTERS_FROM_HERE_ARE_INTERESTING);
 324   }
 325   chunk->SetFlag(MemoryChunk::SCAN_ON_SCAVENGE);
 326 }
 327
 328
 329 void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
 330     PagedSpace* space) {
 331   PageIterator it(space);
 332   while (it.has_next()) {
 333     Page* p = it.next();
 334     SetOldSpacePageFlags(p, false, false);
 335   }
 336 }
 337
 338
 339 void IncrementalMarking::DeactivateIncrementalWriteBarrierForSpace(
 340     NewSpace* space) {
 341   NewSpacePageIterator it(space);
 342   while (it.has_next()) {
 343     NewSpacePage* p = it.next();
 344     SetNewSpacePageFlags(p, false);
 345   }
 346 }
 347
 348
 349 void IncrementalMarking::DeactivateIncrementalWriteBarrier() {
 350   DeactivateIncrementalWriteBarrierForSpace(heap_->old_pointer_space());
 351   DeactivateIncrementalWriteBarrierForSpace(heap_->old_data_space());
 352   DeactivateIncrementalWriteBarrierForSpace(heap_->cell_space());
 353   DeactivateIncrementalWriteBarrierForSpace(heap_->map_space());
 354   DeactivateIncrementalWriteBarrierForSpace(heap_->code_space());
 355   DeactivateIncrementalWriteBarrierForSpace(heap_->new_space());
 356
 357   LargePage* lop = heap_->lo_space()->first_page();
 358   while (lop->is_valid()) {
 359     SetOldSpacePageFlags(lop, false, false);
 360     lop = lop->next_page();
 361   }
 362 }
 363
 364
 365 void IncrementalMarking::ActivateIncrementalWriteBarrier(PagedSpace* space) {
 366   PageIterator it(space);
 367   while (it.has_next()) {
 368     Page* p = it.next();
 369     SetOldSpacePageFlags(p, true, is_compacting_);
 370   }
 371 }
 372
 373
 374 void IncrementalMarking::ActivateIncrementalWriteBarrier(NewSpace* space) {
 375   NewSpacePageIterator it(space->ToSpaceStart(), space->ToSpaceEnd());
 376   while (it.has_next()) {
 377     NewSpacePage* p = it.next();
 378     SetNewSpacePageFlags(p, true);
 379   }
 380 }
 381
 382
 383 void IncrementalMarking::ActivateIncrementalWriteBarrier() {
 384   ActivateIncrementalWriteBarrier(heap_->old_pointer_space());
 385   ActivateIncrementalWriteBarrier(heap_->old_data_space());
 386   ActivateIncrementalWriteBarrier(heap_->cell_space());
 387   ActivateIncrementalWriteBarrier(heap_->map_space());
 388   ActivateIncrementalWriteBarrier(heap_->code_space());
 389   ActivateIncrementalWriteBarrier(heap_->new_space());
 390
 391   LargePage* lop = heap_->lo_space()->first_page();
 392   while (lop->is_valid()) {
 393     SetOldSpacePageFlags(lop, true, is_compacting_);
 394     lop = lop->next_page();
 395   }
 396 }
 397
 398
 399 bool IncrementalMarking::WorthActivating() {
 400 #ifndef DEBUG
 401   static const intptr_t kActivationThreshold = 8 * MB;
 402 #else
 403   // TODO(gc) consider setting this to some low level so that some
 404   // debug tests run with incremental marking and some without.
 405   static const intptr_t kActivationThreshold = 0;
 406 #endif
 407
 408   return !FLAG_expose_gc &&
 409       FLAG_incremental_marking &&
 410       !Serializer::enabled() &&
 411       heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
 412 }
 413
 414
 415 void IncrementalMarking::ActivateGeneratedStub(Code* stub) {
 416   ASSERT(RecordWriteStub::GetMode(stub) ==
 417          RecordWriteStub::STORE_BUFFER_ONLY);
 418
 419   if (!IsMarking()) {
 420     // Initially stub is generated in STORE_BUFFER_ONLY mode thus
 421     // we don't need to do anything if incremental marking is
 422     // not active.
 423   } else if (IsCompacting()) {
 424     RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL_COMPACTION);
 425   } else {
 426     RecordWriteStub::Patch(stub, RecordWriteStub::INCREMENTAL);
 427   }
 428 }
 429
 430
 431 static void PatchIncrementalMarkingRecordWriteStubs(
 432     Heap* heap, RecordWriteStub::Mode mode) {
 433   UnseededNumberDictionary* stubs = heap->code_stubs();
 434
 435   int capacity = stubs->Capacity();
 436   for (int i = 0; i < capacity; i++) {
 437     Object* k = stubs->KeyAt(i);
 438     if (stubs->IsKey(k)) {
 439       uint32_t key = NumberToUint32(k);
 440
 441       if (CodeStub::MajorKeyFromKey(key) ==
 442           CodeStub::RecordWrite) {
 443         Object* e = stubs->ValueAt(i);
 444         if (e->IsCode()) {
 445           RecordWriteStub::Patch(Code::cast(e), mode);
 446         }
 447       }
 448     }
 449   }
 450 }
 451
 452
 453 void IncrementalMarking::EnsureMarkingDequeIsCommitted() {
 454   if (marking_deque_memory_ == NULL) {
 455     marking_deque_memory_ = new VirtualMemory(4 * MB);
 456   }
 457   if (!marking_deque_memory_committed_) {
 458     bool success = marking_deque_memory_->Commit(
 459         reinterpret_cast<Address>(marking_deque_memory_->address()),
 460         marking_deque_memory_->size(),
 461         false);  // Not executable.
 462     CHECK(success);
 463     marking_deque_memory_committed_ = true;
 464   }
 465 }
 466
 467 void IncrementalMarking::UncommitMarkingDeque() {
 468   if (state_ == STOPPED && marking_deque_memory_committed_) {
 469     bool success = marking_deque_memory_->Uncommit(
 470         reinterpret_cast<Address>(marking_deque_memory_->address()),
 471         marking_deque_memory_->size());
 472     CHECK(success);
 473     marking_deque_memory_committed_ = false;
 474   }
 475 }
 476
 477
 478 void IncrementalMarking::Start() {
 479   if (FLAG_trace_incremental_marking) {
 480     PrintF("[IncrementalMarking] Start\n");
 481   }
 482   ASSERT(FLAG_incremental_marking);
 483   ASSERT(state_ == STOPPED);
 484
 485   ResetStepCounters();
 486
 487   if (heap_->old_pointer_space()->IsSweepingComplete() &&
 488       heap_->old_data_space()->IsSweepingComplete()) {
 489     StartMarking(ALLOW_COMPACTION);
 490   } else {
 491     if (FLAG_trace_incremental_marking) {
 492       PrintF("[IncrementalMarking] Start sweeping.\n");
 493     }
 494     state_ = SWEEPING;
 495   }
 496
 497   heap_->new_space()->LowerInlineAllocationLimit(kAllocatedThreshold);
 498 }
 499
 500
 501 static void MarkObjectGreyDoNotEnqueue(Object* obj) {
 502   if (obj->IsHeapObject()) {
 503     HeapObject* heap_obj = HeapObject::cast(obj);
 504     MarkBit mark_bit = Marking::MarkBitFrom(HeapObject::cast(obj));
 505     if (Marking::IsBlack(mark_bit)) {
 506       MemoryChunk::IncrementLiveBytesFromGC(heap_obj->address(),
 507                                             -heap_obj->Size());
 508     }
 509     Marking::AnyToGrey(mark_bit);
 510   }
 511 }
 512
 513
 514 void IncrementalMarking::StartMarking(CompactionFlag flag) {
 515   if (FLAG_trace_incremental_marking) {
 516     PrintF("[IncrementalMarking] Start marking\n");
 517   }
 518
 519   is_compacting_ = !FLAG_never_compact && (flag == ALLOW_COMPACTION) &&
 520       heap_->mark_compact_collector()->StartCompaction(
 521           MarkCompactCollector::INCREMENTAL_COMPACTION);
 522
 523   state_ = MARKING;
 524
 525   RecordWriteStub::Mode mode = is_compacting_ ?
 526       RecordWriteStub::INCREMENTAL_COMPACTION : RecordWriteStub::INCREMENTAL;
 527
 528   PatchIncrementalMarkingRecordWriteStubs(heap_, mode);
 529
 530   EnsureMarkingDequeIsCommitted();
 531
 532   // Initialize marking stack.
 533   Address addr = static_cast<Address>(marking_deque_memory_->address());
 534   size_t size = marking_deque_memory_->size();
 535   if (FLAG_force_marking_deque_overflows) size = 64 * kPointerSize;
 536   marking_deque_.Initialize(addr, addr + size);
 537
 538   ActivateIncrementalWriteBarrier();
 539
 540 #ifdef DEBUG
 541   // Marking bits are cleared by the sweeper.
 542   if (FLAG_verify_heap) {
 543     heap_->mark_compact_collector()->VerifyMarkbitsAreClean();
 544   }
 545 #endif
 546
 547   heap_->CompletelyClearInstanceofCache();
 548   heap_->isolate()->compilation_cache()->MarkCompactPrologue();
 549
 550   if (FLAG_cleanup_code_caches_at_gc) {
 551     // We will mark cache black with a separate pass
 552     // when we finish marking.
 553     MarkObjectGreyDoNotEnqueue(heap_->polymorphic_code_cache());
 554   }
 555
 556   // Mark strong roots grey.
 557   IncrementalMarkingRootMarkingVisitor visitor(heap_, this);
 558   heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
 559
 560   // Ready to start incremental marking.
 561   if (FLAG_trace_incremental_marking) {
 562     PrintF("[IncrementalMarking] Running\n");
 563   }
 564 }
 565
 566
 567 void IncrementalMarking::PrepareForScavenge() {
 568   if (!IsMarking()) return;
 569   NewSpacePageIterator it(heap_->new_space()->FromSpaceStart(),
 570                           heap_->new_space()->FromSpaceEnd());
 571   while (it.has_next()) {
 572     Bitmap::Clear(it.next());
 573   }
 574 }
 575
 576
 577 void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
 578   if (!IsMarking()) return;
 579
 580   int current = marking_deque_.bottom();
 581   int mask = marking_deque_.mask();
 582   int limit = marking_deque_.top();
 583   HeapObject** array = marking_deque_.array();
 584   int new_top = current;
 585
 586   Map* filler_map = heap_->one_pointer_filler_map();
 587
 588   while (current != limit) {
 589     HeapObject* obj = array[current];
 590     ASSERT(obj->IsHeapObject());
 591     current = ((current + 1) & mask);
 592     if (heap_->InNewSpace(obj)) {
 593       MapWord map_word = obj->map_word();
 594       if (map_word.IsForwardingAddress()) {
 595         HeapObject* dest = map_word.ToForwardingAddress();
 596         array[new_top] = dest;
 597         new_top = ((new_top + 1) & mask);
 598         ASSERT(new_top != marking_deque_.bottom());
 599 #ifdef DEBUG
 600         MarkBit mark_bit = Marking::MarkBitFrom(obj);
 601         ASSERT(Marking::IsGrey(mark_bit) ||
 602                (obj->IsFiller() && Marking::IsWhite(mark_bit)));
 603 #endif
 604       }
 605     } else if (obj->map() != filler_map) {
 606       // Skip one word filler objects that appear on the
 607       // stack when we perform in place array shift.
 608       array[new_top] = obj;
 609       new_top = ((new_top + 1) & mask);
 610       ASSERT(new_top != marking_deque_.bottom());
 611 #ifdef DEBUG
 612         MarkBit mark_bit = Marking::MarkBitFrom(obj);
 613         ASSERT(Marking::IsGrey(mark_bit) ||
 614                (obj->IsFiller() && Marking::IsWhite(mark_bit)));
 615 #endif
 616     }
 617   }
 618   marking_deque_.set_top(new_top);
 619
 620   steps_took_since_last_gc_ = 0;
 621   steps_count_since_last_gc_ = 0;
 622   longest_step_ = 0.0;
 623 }
 624
 625
 626 void IncrementalMarking::VisitGlobalContext(Context* ctx, ObjectVisitor* v) {
 627   v->VisitPointers(
 628       HeapObject::RawField(
 629           ctx, Context::MarkCompactBodyDescriptor::kStartOffset),
 630       HeapObject::RawField(
 631           ctx, Context::MarkCompactBodyDescriptor::kEndOffset));
 632
 633   MarkCompactCollector* collector = heap_->mark_compact_collector();
 634   for (int idx = Context::FIRST_WEAK_SLOT;
 635        idx < Context::GLOBAL_CONTEXT_SLOTS;
 636        ++idx) {
 637     Object** slot =
 638         HeapObject::RawField(ctx, FixedArray::OffsetOfElementAt(idx));
 639     collector->RecordSlot(slot, slot, *slot);
 640   }
 641 }
 642
 643
 644 void IncrementalMarking::Hurry() {
 645   if (state() == MARKING) {
 646     double start = 0.0;
 647     if (FLAG_trace_incremental_marking) {
 648       PrintF("[IncrementalMarking] Hurry\n");
 649       start = OS::TimeCurrentMillis();
 650     }
 651     // TODO(gc) hurry can mark objects it encounters black as mutator
 652     // was stopped.
 653     Map* filler_map = heap_->one_pointer_filler_map();
 654     Map* global_context_map = heap_->global_context_map();
 655     IncrementalMarkingMarkingVisitor marking_visitor(heap_, this);
 656     while (!marking_deque_.IsEmpty()) {
 657       HeapObject* obj = marking_deque_.Pop();
 658
 659       // Explicitly skip one word fillers. Incremental markbit patterns are
 660       // correct only for objects that occupy at least two words.
 661       Map* map = obj->map();
 662       if (map == filler_map) {
 663         continue;
 664       } else if (map == global_context_map) {
 665         // Global contexts have weak fields.
 666         VisitGlobalContext(Context::cast(obj), &marking_visitor);
 667       } else if (map->instance_type() == MAP_TYPE) {
 668         Map* map = Map::cast(obj);
 669         heap_->ClearCacheOnMap(map);
 670
 671         // When map collection is enabled we have to mark through map's
 672         // transitions and back pointers in a special way to make these links
 673         // weak.  Only maps for subclasses of JSReceiver can have transitions.
 674         STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
 675         if (FLAG_collect_maps &&
 676             map->instance_type() >= FIRST_JS_RECEIVER_TYPE) {
 677           marker_.MarkMapContents(map);
 678         } else {
 679           marking_visitor.VisitPointers(
 680               HeapObject::RawField(map, Map::kPointerFieldsBeginOffset),
 681               HeapObject::RawField(map, Map::kPointerFieldsEndOffset));
 682         }
 683       } else {
 684         obj->Iterate(&marking_visitor);
 685       }
 686
 687       MarkBit mark_bit = Marking::MarkBitFrom(obj);
 688       ASSERT(!Marking::IsBlack(mark_bit));
 689       Marking::MarkBlack(mark_bit);
 690       MemoryChunk::IncrementLiveBytesFromGC(obj->address(), obj->Size());
 691     }
 692     state_ = COMPLETE;
 693     if (FLAG_trace_incremental_marking) {
 694       double end = OS::TimeCurrentMillis();
 695       PrintF("[IncrementalMarking] Complete (hurry), spent %d ms.\n",
 696              static_cast<int>(end - start));
 697     }
 698   }
 699
 700   if (FLAG_cleanup_code_caches_at_gc) {
 701     PolymorphicCodeCache* poly_cache = heap_->polymorphic_code_cache();
 702     Marking::GreyToBlack(Marking::MarkBitFrom(poly_cache));
 703     MemoryChunk::IncrementLiveBytesFromGC(poly_cache->address(),
 704                                           PolymorphicCodeCache::kSize);
 705   }
 706
 707   Object* context = heap_->global_contexts_list();
 708   while (!context->IsUndefined()) {
 709     // GC can happen when the context is not fully initialized,
 710     // so the cache can be undefined.
 711     HeapObject* cache = HeapObject::cast(
 712         Context::cast(context)->get(Context::NORMALIZED_MAP_CACHE_INDEX));
 713     if (!cache->IsUndefined()) {
 714       MarkBit mark_bit = Marking::MarkBitFrom(cache);
 715       if (Marking::IsGrey(mark_bit)) {
 716         Marking::GreyToBlack(mark_bit);
 717         MemoryChunk::IncrementLiveBytesFromGC(cache->address(), cache->Size());
 718       }
 719     }
 720     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
 721   }
 722 }
 723
 724
 725 void IncrementalMarking::Abort() {
 726   if (IsStopped()) return;
 727   if (FLAG_trace_incremental_marking) {
 728     PrintF("[IncrementalMarking] Aborting.\n");
 729   }
 730   heap_->new_space()->LowerInlineAllocationLimit(0);
 731   IncrementalMarking::set_should_hurry(false);
 732   ResetStepCounters();
 733   if (IsMarking()) {
 734     PatchIncrementalMarkingRecordWriteStubs(heap_,
 735                                             RecordWriteStub::STORE_BUFFER_ONLY);
 736     DeactivateIncrementalWriteBarrier();
 737
 738     if (is_compacting_) {
 739       LargeObjectIterator it(heap_->lo_space());
 740       for (HeapObject* obj = it.Next(); obj != NULL; obj = it.Next()) {
 741         Page* p = Page::FromAddress(obj->address());
 742         if (p->IsFlagSet(Page::RESCAN_ON_EVACUATION)) {
 743           p->ClearFlag(Page::RESCAN_ON_EVACUATION);
 744         }
 745       }
 746     }
 747   }
 748   heap_->isolate()->stack_guard()->Continue(GC_REQUEST);
 749   state_ = STOPPED;
 750   is_compacting_ = false;
 751 }
 752
 753
 754 void IncrementalMarking::Finalize() {
 755   Hurry();
 756   state_ = STOPPED;
 757   is_compacting_ = false;
 758   heap_->new_space()->LowerInlineAllocationLimit(0);
 759   IncrementalMarking::set_should_hurry(false);
 760   ResetStepCounters();
 761   PatchIncrementalMarkingRecordWriteStubs(heap_,
 762                                           RecordWriteStub::STORE_BUFFER_ONLY);
 763   DeactivateIncrementalWriteBarrier();
 764   ASSERT(marking_deque_.IsEmpty());
 765   heap_->isolate()->stack_guard()->Continue(GC_REQUEST);
 766 }
 767
 768
 769 void IncrementalMarking::MarkingComplete(CompletionAction action) {
 770   state_ = COMPLETE;
 771   // We will set the stack guard to request a GC now.  This will mean the rest
 772   // of the GC gets performed as soon as possible (we can't do a GC here in a
 773   // record-write context).  If a few things get allocated between now and then
 774   // that shouldn't make us do a scavenge and keep being incremental, so we set
 775   // the should-hurry flag to indicate that there can't be much work left to do.
 776   set_should_hurry(true);
 777   if (FLAG_trace_incremental_marking) {
 778     PrintF("[IncrementalMarking] Complete (normal).\n");
 779   }
 780   if (action == GC_VIA_STACK_GUARD) {
 781     heap_->isolate()->stack_guard()->RequestGC();
 782   }
 783 }
 784
 785
 786 void IncrementalMarking::Step(intptr_t allocated_bytes,
 787                               CompletionAction action) {
 788   if (heap_->gc_state() != Heap::NOT_IN_GC ||
 789       !FLAG_incremental_marking ||
 790       !FLAG_incremental_marking_steps ||
 791       (state_ != SWEEPING && state_ != MARKING)) {
 792     return;
 793   }
 794
 795   allocated_ += allocated_bytes;
 796
 797   if (allocated_ < kAllocatedThreshold) return;
 798
 799   if (state_ == MARKING && no_marking_scope_depth_ > 0) return;
 800
 801   intptr_t bytes_to_process = allocated_ * allocation_marking_factor_;
 802   bytes_scanned_ += bytes_to_process;
 803
 804   double start = 0;
 805
 806   if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
 807     start = OS::TimeCurrentMillis();
 808   }
 809
 810   if (state_ == SWEEPING) {
 811     if (heap_->AdvanceSweepers(static_cast<int>(bytes_to_process))) {
 812       bytes_scanned_ = 0;
 813       StartMarking(PREVENT_COMPACTION);
 814     }
 815   } else if (state_ == MARKING) {
 816     Map* filler_map = heap_->one_pointer_filler_map();
 817     Map* global_context_map = heap_->global_context_map();
 818     IncrementalMarkingMarkingVisitor marking_visitor(heap_, this);
 819     while (!marking_deque_.IsEmpty() && bytes_to_process > 0) {
 820       HeapObject* obj = marking_deque_.Pop();
 821
 822       // Explicitly skip one word fillers. Incremental markbit patterns are
 823       // correct only for objects that occupy at least two words.
 824       Map* map = obj->map();
 825       if (map == filler_map) continue;
 826
 827       int size = obj->SizeFromMap(map);
 828       bytes_to_process -= size;
 829       MarkBit map_mark_bit = Marking::MarkBitFrom(map);
 830       if (Marking::IsWhite(map_mark_bit)) {
 831         WhiteToGreyAndPush(map, map_mark_bit);
 832       }
 833
 834       // TODO(gc) switch to static visitor instead of normal visitor.
 835       if (map == global_context_map) {
 836         // Global contexts have weak fields.
 837         Context* ctx = Context::cast(obj);
 838
 839         // We will mark cache black with a separate pass
 840         // when we finish marking.
 841         MarkObjectGreyDoNotEnqueue(ctx->normalized_map_cache());
 842
 843         VisitGlobalContext(ctx, &marking_visitor);
 844       } else if (map->instance_type() == MAP_TYPE) {
 845         Map* map = Map::cast(obj);
 846         heap_->ClearCacheOnMap(map);
 847
 848         // When map collection is enabled we have to mark through map's
 849         // transitions and back pointers in a special way to make these links
 850         // weak.  Only maps for subclasses of JSReceiver can have transitions.
 851         STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
 852         if (FLAG_collect_maps &&
 853             map->instance_type() >= FIRST_JS_RECEIVER_TYPE) {
 854           marker_.MarkMapContents(map);
 855         } else {
 856           marking_visitor.VisitPointers(
 857               HeapObject::RawField(map, Map::kPointerFieldsBeginOffset),
 858               HeapObject::RawField(map, Map::kPointerFieldsEndOffset));
 859         }
 860       } else if (map->instance_type() == JS_FUNCTION_TYPE) {
 861         marking_visitor.VisitPointers(
 862             HeapObject::RawField(obj, JSFunction::kPropertiesOffset),
 863             HeapObject::RawField(obj, JSFunction::kCodeEntryOffset));
 864
 865         marking_visitor.VisitCodeEntry(
 866             obj->address() + JSFunction::kCodeEntryOffset);
 867
 868         marking_visitor.VisitPointers(
 869             HeapObject::RawField(obj,
 870                                  JSFunction::kCodeEntryOffset + kPointerSize),
 871             HeapObject::RawField(obj,
 872                                  JSFunction::kNonWeakFieldsEndOffset));
 873       } else {
 874         obj->IterateBody(map->instance_type(), size, &marking_visitor);
 875       }
 876
 877       MarkBit obj_mark_bit = Marking::MarkBitFrom(obj);
 878       SLOW_ASSERT(Marking::IsGrey(obj_mark_bit) ||
 879                   (obj->IsFiller() && Marking::IsWhite(obj_mark_bit)));
 880       Marking::MarkBlack(obj_mark_bit);
 881       MemoryChunk::IncrementLiveBytesFromGC(obj->address(), size);
 882     }
 883     if (marking_deque_.IsEmpty()) MarkingComplete(action);
 884   }
 885
 886   allocated_ = 0;
 887
 888   steps_count_++;
 889   steps_count_since_last_gc_++;
 890
 891   bool speed_up = false;
 892
 893   if ((steps_count_ % kAllocationMarkingFactorSpeedupInterval) == 0) {
 894     if (FLAG_trace_gc) {
 895       PrintF("Speed up marking after %d steps\n",
 896              static_cast<int>(kAllocationMarkingFactorSpeedupInterval));
 897     }
 898     speed_up = true;
 899   }
 900
 901   bool space_left_is_very_small =
 902       (old_generation_space_available_at_start_of_incremental_ < 10 * MB);
 903
 904   bool only_1_nth_of_space_that_was_available_still_left =
 905       (SpaceLeftInOldSpace() * (allocation_marking_factor_ + 1) <
 906           old_generation_space_available_at_start_of_incremental_);
 907
 908   if (space_left_is_very_small ||
 909       only_1_nth_of_space_that_was_available_still_left) {
 910     if (FLAG_trace_gc) PrintF("Speed up marking because of low space left\n");
 911     speed_up = true;
 912   }
 913
 914   bool size_of_old_space_multiplied_by_n_during_marking =
 915       (heap_->PromotedTotalSize() >
 916        (allocation_marking_factor_ + 1) *
 917            old_generation_space_used_at_start_of_incremental_);
 918   if (size_of_old_space_multiplied_by_n_during_marking) {
 919     speed_up = true;
 920     if (FLAG_trace_gc) {
 921       PrintF("Speed up marking because of heap size increase\n");
 922     }
 923   }
 924
 925   int64_t promoted_during_marking = heap_->PromotedTotalSize()
 926       - old_generation_space_used_at_start_of_incremental_;
 927   intptr_t delay = allocation_marking_factor_ * MB;
 928   intptr_t scavenge_slack = heap_->MaxSemiSpaceSize();
 929
 930   // We try to scan at at least twice the speed that we are allocating.
 931   if (promoted_during_marking > bytes_scanned_ / 2 + scavenge_slack + delay) {
 932     if (FLAG_trace_gc) {
 933       PrintF("Speed up marking because marker was not keeping up\n");
 934     }
 935     speed_up = true;
 936   }
 937
 938   if (speed_up) {
 939     if (state_ != MARKING) {
 940       if (FLAG_trace_gc) {
 941         PrintF("Postponing speeding up marking until marking starts\n");
 942       }
 943     } else {
 944       allocation_marking_factor_ += kAllocationMarkingFactorSpeedup;
 945       allocation_marking_factor_ = static_cast<int>(
 946           Min(kMaxAllocationMarkingFactor,
 947               static_cast<intptr_t>(allocation_marking_factor_ * 1.3)));
 948       if (FLAG_trace_gc) {
 949         PrintF("Marking speed increased to %d\n", allocation_marking_factor_);
 950       }
 951     }
 952   }
 953
 954   if (FLAG_trace_incremental_marking || FLAG_trace_gc) {
 955     double end = OS::TimeCurrentMillis();
 956     double delta = (end - start);
 957     longest_step_ = Max(longest_step_, delta);
 958     steps_took_ += delta;
 959     steps_took_since_last_gc_ += delta;
 960   }
 961 }
 962
 963
 964 void IncrementalMarking::ResetStepCounters() {
 965   steps_count_ = 0;
 966   steps_took_ = 0;
 967   longest_step_ = 0.0;
 968   old_generation_space_available_at_start_of_incremental_ =
 969       SpaceLeftInOldSpace();
 970   old_generation_space_used_at_start_of_incremental_ =
 971       heap_->PromotedTotalSize();
 972   steps_count_since_last_gc_ = 0;
 973   steps_took_since_last_gc_ = 0;
 974   bytes_rescanned_ = 0;
 975   allocation_marking_factor_ = kInitialAllocationMarkingFactor;
 976   bytes_scanned_ = 0;
 977 }
 978
 979
 980 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
 981   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
 982 }
 983
 984 } }  // namespace v8::internal