// Note the end of a marking phase. Install the start of
  // the unmarked area that was captured at start of marking.

  void note_end_of_marking() {

  {- -------------------------------------------
  (1) next TAMS と prev TAMS を入れ替える.
      ---------------------------------------- -}

        _prev_top_at_mark_start = _next_top_at_mark_start;
        _prev_marked_bytes = _next_marked_bytes;
        _next_marked_bytes = 0;

        guarantee(_prev_marked_bytes <=
                  (size_t) (prev_top_at_mark_start() - bottom()) * HeapWordSize,
                  "invariant");
      }