1. A method for generating a dynamic call graph of an observation period having a plurality of sampling periods, the method comprising: collecting information on what program code pages are accessed during each sampling period; defining parts of an executable program code which are accessible during each sampling period according to the collected information; defining a set of functions within the defined parts of the executable program code; generating dynamic call graphs using the defined set of functions for each sampling period; generating accurate dynamic call graphs by deleting erroneous dynamic call graphs from the generated dynamic call graphs through analyzing a program source code; and generating dynamic call graphs for the observation period by combining accurate dynamic call graphs of each sampling period.