1. A method comprising: receiving a plurality of call graphs from an executable software system, each call graph comprising a plurality of nodes, wherein multiple nodes in different call graphs correspond to the same sub-routines of the executable software system, wherein each node is associated with one or more values indicating resource consumption, and wherein the plurality of call graphs represent resource consumption of the executable software system at different times; generating a merged call graph from the plurality of call graphs, wherein said one or more values for nodes in different call graphs corresponding to the same sub-routine are combined, and wherein the combined values in the merged call graph represent resource consumption across said different times; eliminating nodes from the merged call graph based on said combined values to generated a critical call graph indicating the nodes that consume the most significant amount of resources across said different times; identifying a node within the critical call graph that has been changed across said different times; and analyzing the node to determine a contributing factor to the resource consumption.