A host computer system is configured to present each of multiple resident contexts with an address space that may be mapped, at least in part, to corresponding portions of a host memory. The address space of a selected context is sampled, and, for each of a plurality of sampled portions of the address space of the selected context that are backed by a corresponding portion of host memory, a count of the number of portions of address spaces of any contexts that are backed by the same portion of the host memory is obtained. A metric is then computed as a function of the count. A decision about swapping out or reclaiming the allocation of the memory of the contexts is based on the metric. The metric is preferably a function of a mean (such as harmonic, geometric or arithmetic) or median of the counts for each context.