US Patent 9009385 Co-residency detection in a cloud-based system

At least one virtual machine implemented on a given physical machine in an information processing system is able to detect the presence of one or more other virtual machines that are also co-resident on that same physical machine. More particularly, at least one virtual machine is configured to avoid usage of a selected portion of a memory resource of the physical machine for a period of time, and to monitor the selected portion of the memory resource for activity during the period of time. Detection of a sufficient level of such activity indicates that the physical machine is also being shared by at least one other virtual machine. The memory resource of the physical machine may comprise, for example, a cache memory, and the selected portion of the memory resource may comprise one or more randomly selected sets of the cache memory.