spaces.cc.svn-base

Google浏览器V8内核代码

};


// must be small, since an iteration is used for lookup
const int kMaxComments = 64;
static CommentStatistic comments_statistics[kMaxComments+1];


void PagedSpace::ReportCodeStatistics() {
  ReportCodeKindStatistics();
  PrintF("Code comment statistics (\"   [ comment-txt   :    size/   "
         "count  (average)\"):\n");
  for (int i = 0; i <= kMaxComments; i++) {
    const CommentStatistic& cs = comments_statistics[i];
    if (cs.size > 0) {
      PrintF("   %-30s: %10d/%6d     (%d)\n", cs.comment, cs.size, cs.count,
             cs.size/cs.count);
    }
  }
  PrintF("\n");
}


void PagedSpace::ResetCodeStatistics() {
  ClearCodeKindStatistics();
  for (int i = 0; i < kMaxComments; i++) comments_statistics[i].Clear();
  comments_statistics[kMaxComments].comment = "Unknown";
  comments_statistics[kMaxComments].size = 0;
  comments_statistics[kMaxComments].count = 0;
}


// Adds comment to 'comment_statistics' table. Performance OK sa long as
// 'kMaxComments' is small
static void EnterComment(const char* comment, int delta) {
  // Do not count empty comments
  if (delta <= 0) return;
  CommentStatistic* cs = &comments_statistics[kMaxComments];
  // Search for a free or matching entry in 'comments_statistics': 'cs'
  // points to result.
  for (int i = 0; i < kMaxComments; i++) {
    if (comments_statistics[i].comment == NULL) {
      cs = &comments_statistics[i];
      cs->comment = comment;
      break;
    } else if (strcmp(comments_statistics[i].comment, comment) == 0) {
      cs = &comments_statistics[i];
      break;
    }
  }
  // Update entry for 'comment'
  cs->size += delta;
  cs->count += 1;
}


// Call for each nested comment start (start marked with '[ xxx', end marked
// with ']'.  RelocIterator 'it' must point to a comment reloc info.
static void CollectCommentStatistics(RelocIterator* it) {
  ASSERT(!it->done());
  ASSERT(it->rinfo()->rmode() == RelocInfo::COMMENT);
  const char* tmp = reinterpret_cast<const char*>(it->rinfo()->data());
  if (tmp[0] != '[') {
    // Not a nested comment; skip
    return;
  }

  // Search for end of nested comment or a new nested comment
  const char* const comment_txt =
      reinterpret_cast<const char*>(it->rinfo()->data());
  const byte* prev_pc = it->rinfo()->pc();
  int flat_delta = 0;
  it->next();
  while (true) {
    // All nested comments must be terminated properly, and therefore exit
    // from loop.
    ASSERT(!it->done());
    if (it->rinfo()->rmode() == RelocInfo::COMMENT) {
      const char* const txt =
          reinterpret_cast<const char*>(it->rinfo()->data());
      flat_delta += it->rinfo()->pc() - prev_pc;
      if (txt[0] == ']') break;  // End of nested  comment
      // A new comment
      CollectCommentStatistics(it);
      // Skip code that was covered with previous comment
      prev_pc = it->rinfo()->pc();
    }
    it->next();
  }
  EnterComment(comment_txt, flat_delta);
}


// Collects code size statistics:
// - by code kind
// - by code comment
void PagedSpace::CollectCodeStatistics() {
  HeapObjectIterator obj_it(this);
  while (obj_it.has_next()) {
    HeapObject* obj = obj_it.next();
    if (obj->IsCode()) {
      Code* code = Code::cast(obj);
      code_kind_statistics[code->kind()] += code->Size();
      RelocIterator it(code);
      int delta = 0;
      const byte* prev_pc = code->instruction_start();
      while (!it.done()) {
        if (it.rinfo()->rmode() == RelocInfo::COMMENT) {
          delta += it.rinfo()->pc() - prev_pc;
          CollectCommentStatistics(&it);
          prev_pc = it.rinfo()->pc();
        }
        it.next();
      }

      ASSERT(code->instruction_start() <= prev_pc &&
             prev_pc <= code->relocation_start());
      delta += code->relocation_start() - prev_pc;
      EnterComment("NoComment", delta);
    }
  }
}


void OldSpace::ReportStatistics() {
  int pct = Available() * 100 / Capacity();
  PrintF("  capacity: %d, waste: %d, available: %d, %%%d\n",
         Capacity(), Waste(), Available(), pct);

  // Report remembered set statistics.
  int rset_marked_pointers = 0;
  int rset_marked_arrays = 0;
  int rset_marked_array_elements = 0;
  int cross_gen_pointers = 0;
  int cross_gen_array_elements = 0;

  PageIterator page_it(this, PageIterator::PAGES_IN_USE);
  while (page_it.has_next()) {
    Page* p = page_it.next();

    for (Address rset_addr = p->RSetStart();
         rset_addr < p->RSetEnd();
         rset_addr += kIntSize) {
      int rset = Memory::int_at(rset_addr);
      if (rset != 0) {
        // Bits were set
        int intoff = rset_addr - p->address();
        int bitoff = 0;
        for (; bitoff < kBitsPerInt; ++bitoff) {
          if ((rset & (1 << bitoff)) != 0) {
            int bitpos = intoff*kBitsPerByte + bitoff;
            Address slot = p->OffsetToAddress(bitpos << kObjectAlignmentBits);
            Object** obj = reinterpret_cast<Object**>(slot);
            if (*obj == Heap::fixed_array_map()) {
              rset_marked_arrays++;
              FixedArray* fa = FixedArray::cast(HeapObject::FromAddress(slot));

              rset_marked_array_elements += fa->length();
              // Manually inline FixedArray::IterateBody
              Address elm_start = slot + FixedArray::kHeaderSize;
              Address elm_stop = elm_start + fa->length() * kPointerSize;
              for (Address elm_addr = elm_start;
                   elm_addr < elm_stop; elm_addr += kPointerSize) {
                // Filter non-heap-object pointers
                Object** elm_p = reinterpret_cast<Object**>(elm_addr);
                if (Heap::InNewSpace(*elm_p))
                  cross_gen_array_elements++;
              }
            } else {
              rset_marked_pointers++;
              if (Heap::InNewSpace(*obj))
                cross_gen_pointers++;
            }
          }
        }
      }
    }
  }

  pct = rset_marked_pointers == 0 ?
        0 : cross_gen_pointers * 100 / rset_marked_pointers;
  PrintF("  rset-marked pointers %d, to-new-space %d (%%%d)\n",
            rset_marked_pointers, cross_gen_pointers, pct);
  PrintF("  rset_marked arrays %d, ", rset_marked_arrays);
  PrintF("  elements %d, ", rset_marked_array_elements);
  pct = rset_marked_array_elements == 0 ? 0
           : cross_gen_array_elements * 100 / rset_marked_array_elements;
  PrintF("  pointers to new space %d (%%%d)\n", cross_gen_array_elements, pct);
  PrintF("  total rset-marked bits %d\n",
            (rset_marked_pointers + rset_marked_arrays));
  pct = (rset_marked_pointers + rset_marked_array_elements) == 0 ? 0
        : (cross_gen_pointers + cross_gen_array_elements) * 100 /
          (rset_marked_pointers + rset_marked_array_elements);
  PrintF("  total rset pointers %d, true cross generation ones %d (%%%d)\n",
         (rset_marked_pointers + rset_marked_array_elements),
         (cross_gen_pointers + cross_gen_array_elements),
         pct);

  ClearHistograms();
  HeapObjectIterator obj_it(this);
  while (obj_it.has_next()) { CollectHistogramInfo(obj_it.next()); }
  ReportHistogram(true);
}


// Dump the range of remembered set words between [start, end) corresponding
// to the pointers starting at object_p.  The allocation_top is an object
// pointer which should not be read past.  This is important for large object
// pages, where some bits in the remembered set range do not correspond to
// allocated addresses.
static void PrintRSetRange(Address start, Address end, Object** object_p,
                           Address allocation_top) {
  Address rset_address = start;

  // If the range starts on on odd numbered word (eg, for large object extra
  // remembered set ranges), print some spaces.
  if ((reinterpret_cast<uint32_t>(start) / kIntSize) % 2 == 1) {
    PrintF("                                    ");
  }

  // Loop over all the words in the range.
  while (rset_address < end) {
    uint32_t rset_word = Memory::uint32_at(rset_address);
    int bit_position = 0;

    // Loop over all the bits in the word.
    while (bit_position < kBitsPerInt) {
      if (object_p == reinterpret_cast<Object**>(allocation_top)) {
        // Print a bar at the allocation pointer.
        PrintF("|");
      } else if (object_p > reinterpret_cast<Object**>(allocation_top)) {
        // Do not dereference object_p past the allocation pointer.
        PrintF("#");
      } else if ((rset_word & (1 << bit_position)) == 0) {
        // Print a dot for zero bits.
        PrintF(".");
      } else if (Heap::InNewSpace(*object_p)) {
        // Print an X for one bits for pointers to new space.
        PrintF("X");
      } else {
        // Print a circle for one bits for pointers to old space.
        PrintF("o");
      }

      // Print a space after every 8th bit except the last.
      if (bit_position % 8 == 7 && bit_position != (kBitsPerInt - 1)) {
        PrintF(" ");
      }

      // Advance to next bit.
      bit_position++;
      object_p++;
    }

    // Print a newline after every odd numbered word, otherwise a space.
    if ((reinterpret_cast<uint32_t>(rset_address) / kIntSize) % 2 == 1) {
      PrintF("\n");
    } else {
      PrintF(" ");
    }

    // Advance to next remembered set word.
    rset_address += kIntSize;
  }
}


void PagedSpace::DoPrintRSet(const char* space_name) {
  PageIterator it(this, PageIterator::PAGES_IN_USE);
  while (it.has_next()) {
    Page* p = it.next();
    PrintF("%s page 0x%x:\n", space_name, p);
    PrintRSetRange(p->RSetStart(), p->RSetEnd(),
                   reinterpret_cast<Object**>(p->ObjectAreaStart()),
                   p->AllocationTop());
    PrintF("\n");
  }
}


void OldSpace::PrintRSet() { DoPrintRSet("old"); }
#endif

// -----------------------------------------------------------------------------
// MapSpace implementation

void MapSpace::PrepareForMarkCompact(bool will_compact) {
  if (will_compact) {
    // Reset relocation info.
    MCResetRelocationInfo();

    // Initialize map index entry.
    int page_count = 0;
    PageIterator it(this, PageIterator::ALL_PAGES);
    while (it.has_next()) {
      ASSERT_MAP_PAGE_INDEX(page_count);

      Page* p = it.next();
      ASSERT(p->mc_page_index == page_count);

      page_addresses_[page_count++] = p->address();
    }

    // During a compacting collection, everything in the space is considered
    // 'available' (set by the call to MCResetRelocationInfo) and we will
    // rediscover live and wasted bytes during the collection.
    ASSERT(Available() == Capacity());
  } else {
    // During a non-compacting collection, everything below the linear
    // allocation pointer except wasted top-of-page blocks is considered
    // allocated and we will rediscover available bytes during the
    // collection.
    accounting_stats_.AllocateBytes(free_list_.available());
  }

  // Clear the free list before a full GC---it will be rebuilt afterward.
  free_list_.Reset();
}


void MapSpace::MCCommitRelocationInfo() {
  // Update fast allocation info.
  allocation_info_.top = mc_forwarding_info_.top;
  allocation_info_.limit = mc_forwarding_info_.limit;
  ASSERT(allocation_info_.VerifyPagedAllocation());

  // The space is compacted and we haven't yet wasted any space.
  ASSERT(Waste() == 0);

  // Update allocation_top of each page in use and compute waste.
  int computed_size = 0;
  PageIterator it(this, PageIterator::PAGES_USED_BY_MC);
  while (it.has_next()) {
    Page* page = it.next();
    Address page_top = page->AllocationTop();
    computed_size += page_top - page->ObjectAreaStart();
    if (it.has_next()) {
      accounting_stats_.WasteBytes(page->ObjectAreaEnd() - page_top);
    }
  }

  // Make sure the computed size - based on the used portion of the
  // pages in use - matches the size we adjust during allocation.
  ASSERT(computed_size == Size());
}


// Slow case for normal allocation. Try in order: (1) allocate in the next
// page in the space, (2) allocate off the space's free list, (3) expand the
// space, (4) fail.
HeapObject* MapSpace::SlowAllocateRaw(int size_in_bytes) {
  // Linear allocation in this space has failed.  If there is another page
  // in the space, move to that page and allocate there.  This allocation
  // should succeed.
  Page* current_page = TopPageOf(allocation_info_);
  if (current_page->next_page()->is_valid()) {
    return AllocateInNextPage(current_page, size_in_bytes);
  }

  // There is no next page in this space.  Try free list allocation.  The
  // map space free list implicitly assumes that all free blocks are map
  // sized.
  if (size_in_bytes == Map::kSize) {
    Object* result = free_list_.Allocate();
    if (!result->IsFailure()) {
      accounting_stats_.AllocateBytes(size_in_bytes);
      return HeapObject::cast(result);
    }
  }

  // Free list allocation failed and there is no next page.  Try to expand
  // the space and allocate in the new next page.
  ASSERT(!current_page->next_page()->is_valid());
  if (Expand(current_page)) {
    return AllocateInNextPage(current_page, size_in_bytes);
  }

  // Finally, fail.
  return NULL;
}


// Move to the next page (there is assumed to be one) and allocate there.
// The top of page block is always wasted, because it is too small to hold a
// map.
HeapObject* MapSpace::AllocateInNextPage(Page* current_page,
                                         int size_in_bytes) {
  ASSERT(current_page->next_page()->is_valid());
  ASSERT(current_page->ObjectAreaEnd() - allocation_info_.top == kPageExtra);
  accounting_stats_.WasteBytes(kPageExtra);
  SetAllocationInfo(&allocation_info_, current_page->next_page());
  return AllocateLinearly(&allocation_info_, size_in_bytes);
}


#ifdef DEBUG
// We do not assume that the PageIterator works, because it depends on the
// invariants we are checking during verification.
void MapSpace::Verify() {
  // The allocation pointer should be valid, and it should be in a page in the
  // space.
  ASSERT(allocation_info_.VerifyPagedAllocation());
  Page* top_page = Page::FromAllocationTop(allocation_info_.top);
  ASSERT(MemoryAllocator::IsPageInSpace(top_page, this));

  // Loop over all the pages.
  bool above_allocation_top = false;
  Page* curr