A computing method includes running, on a plurality of compute nodes, multiple workloads that access respective sets of memory pages. Respective bitmaps are calculated for at least some of the workloads, wherein (i) a bitmap of a workload is statistically indicative of a cardinality of the set of memory pages used by the workload, (ii) a union of two or more bitmaps is statistically indicative of the cardinality of a union of the sets of memory pages used by the two or more corresponding workloads, and (iii) an intersection of first and second bitmaps is statistically indicative of an overlap between respective first and second sets of memory pages used by the corresponding workloads. A decision is made to migrate a selected workload from a source compute node to a destination compute node, based on one or more of the bitmaps.