1. A method of modeling performance degradation of a first application, the method comprising: executing the first application on a computing machine, wherein the first application consumes a first varying portion of common machine resources of the computing machine; executing a memory expandable application on the computing machine, wherein the memory expandable application consumes a second varying portion of the common machine resources of the computing machine defined according to a variable working set size, wherein the first varying portion of the common machine resources is separate from the second varying portion of the common machine resources, and wherein the memory expandable application is an application that is programmed to incrementally vary its own working size set by varying a number of operations executed by the memory expandable application; causing changes to a size of the first varying portion of the common machine resources available to the first application by enlarging or reducing the second varying portion of resources in the common machine resources consumed by the memory expandable application; measuring a performance metric of the first application for each working set size; and plotting the performance metric of the first application as a function of the working set size of the memory expandable application.