C++ MemRegion::is_empty方法代码示例

void CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel(
  Space* sp,
  MemRegion mr,
  OopsInGenClosure* cl,
  CardTableRS* ct,
  uint n_threads)
{
  if (!mr.is_empty()) {
    if (n_threads > 0) {
#if INCLUDE_ALL_GCS
      non_clean_card_iterate_parallel_work(sp, mr, cl, ct, n_threads);
#else  // INCLUDE_ALL_GCS
      fatal("Parallel gc not supported here.");
#endif // INCLUDE_ALL_GCS
    } else {
      // clear_cl finds contiguous dirty ranges of cards to process and clear.

      // This is the single-threaded version used by DefNew.
      const bool parallel = false;

      DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(), cl->gen_boundary(), parallel);
      ClearNoncleanCardWrapper clear_cl(dcto_cl, ct, parallel);

      clear_cl.do_MemRegion(mr);
    }
  }
}

void MutableSpace::initialize(MemRegion mr,
                              bool clear_space,
                              bool mangle_space,
                              bool setup_pages) {

    assert(Universe::on_page_boundary(mr.start()) && Universe::on_page_boundary(mr.end()),
           "invalid space boundaries");

    if (setup_pages && (UseNUMA || AlwaysPreTouch)) {
        // The space may move left and right or expand/shrink.
        // We'd like to enforce the desired page placement.
        MemRegion head, tail;
        if (last_setup_region().is_empty()) {
            // If it's the first initialization don't limit the amount of work.
            head = mr;
            tail = MemRegion(mr.end(), mr.end());
        } else {
            // Is there an intersection with the address space?
            MemRegion intersection = last_setup_region().intersection(mr);
            if (intersection.is_empty()) {
                intersection = MemRegion(mr.end(), mr.end());
            }
            // All the sizes below are in words.
            size_t head_size = 0, tail_size = 0;
            if (mr.start() <= intersection.start()) {
                head_size = pointer_delta(intersection.start(), mr.start());
            }
            if(intersection.end() <= mr.end()) {
                tail_size = pointer_delta(mr.end(), intersection.end());
            }
            // Limit the amount of page manipulation if necessary.
            if (NUMASpaceResizeRate > 0 && !AlwaysPreTouch) {
                const size_t change_size = head_size + tail_size;
                const float setup_rate_words = NUMASpaceResizeRate >> LogBytesPerWord;
                head_size = MIN2((size_t)(setup_rate_words * head_size / change_size),
                                 head_size);
                tail_size = MIN2((size_t)(setup_rate_words * tail_size / change_size),
                                 tail_size);
            }
            head = MemRegion(intersection.start() - head_size, intersection.start());
            tail = MemRegion(intersection.end(), intersection.end() + tail_size);
        }
        assert(mr.contains(head) && mr.contains(tail), "Sanity");

        if (UseNUMA) {
            numa_setup_pages(head, clear_space);
            numa_setup_pages(tail, clear_space);
        }

        if (AlwaysPreTouch) {
            pretouch_pages(head);
            pretouch_pages(tail);
        }

        // Remember where we stopped so that we can continue later.
        set_last_setup_region(MemRegion(head.start(), tail.end()));
    }

inline void CMSBitMap::par_markRange(MemRegion mr) {
  assert_locked();
  mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
  assert(!mr.is_empty(), "unexpected empty region");
  // convert address range into offset range
  size_t start_ofs = heapWordToOffset(mr.start());
  size_t end_ofs = heapWordToOffset(mr.end());
  // Range size is usually just 1 bit.
  _bm.par_set_range(start_ofs, end_ofs, BitMap::small_range);
}

void MutableSpace::numa_setup_pages(MemRegion mr, bool clear_space) {
    if (!mr.is_empty()) {
        size_t page_size = UseLargePages ? alignment() : os::vm_page_size();
        HeapWord *start = (HeapWord*)round_to((intptr_t) mr.start(), page_size);
        HeapWord *end =  (HeapWord*)round_down((intptr_t) mr.end(), page_size);
        if (end > start) {
            size_t size = pointer_delta(end, start, sizeof(char));
            if (clear_space) {
                // Prefer page reallocation to migration.
                os::free_memory((char*)start, size, page_size);
            }
            os::numa_make_global((char*)start, size);
        }
    }
}

void CardTableRS::verify_aligned_region_empty(MemRegion mr) {
  if (!mr.is_empty()) {
    jbyte* cur_entry = byte_for(mr.start());
    jbyte* limit = byte_after(mr.last());
    // The region mr may not start on a card boundary so
    // the first card may reflect a write to the space
    // just prior to mr.
    if (!is_aligned(mr.start())) {
      cur_entry++;
    }
    for (;cur_entry < limit; cur_entry++) {
      guarantee(*cur_entry == CardTableModRefBS::clean_card,
                "Unexpected dirty card found");
    }
  }
}

MemRegion MemRegion::_union(const MemRegion mr2) const {
  // If one region is empty, return the other
  if (is_empty()) return mr2;
  if (mr2.is_empty()) return MemRegion(start(), end());

  // Otherwise, regions must overlap or be adjacent
  assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||
         ((mr2.start() <= start()) && (mr2.end() >= start())),
             "non-adjacent or overlapping regions");
  MemRegion res;
  HeapWord* res_start = MIN2(start(), mr2.start());
  HeapWord* res_end   = MAX2(end(),   mr2.end());
  res.set_start(res_start);
  res.set_end(res_end);
  return res;
}

  void scanCard(size_t index, HeapRegion *r) {
    // Stack allocate the DirtyCardToOopClosure instance
    HeapRegionDCTOC cl(_g1h, r, _oc,
                       CardTableModRefBS::Precise);

    // Set the "from" region in the closure.
    _oc->set_region(r);
    MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);
    MemRegion pre_gc_allocated(r->bottom(), r->scan_top());
    MemRegion mr = pre_gc_allocated.intersection(card_region);
    if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {
      // We make the card as "claimed" lazily (so races are possible
      // but they're benign), which reduces the number of duplicate
      // scans (the rsets of the regions in the cset can intersect).
      _ct_bs->set_card_claimed(index);
      _cards_done++;
      cl.do_MemRegion(mr);
    }
  }