XML : Boost XML parser RAM consumption

I decided to check memory usage of PropertyTree for XML parsing with this piece of code. The XML has something over 120M, but this program was consuming over 2G when I decided to kill it. Is this standard consumption of PropertyTree or there is something wrong?

  #include <boost/property_tree/ptree.hpp>  #include <boost/property_tree/xml_parser.hpp>  #include <boost/foreach.hpp>  #include <iostream>    int main()  {    using boost::property_tree::ptree;    ptree pt;    read_xml("c.xml",pt);    return 0;  }