A technique of workload characterization for a computer system. Records of activity in the system are generated and identified as corresponding to each of a plurality of selected time periods. The records of activity for each selected time period are processed to form a characterization of the activity within each corresponding time period. Further, whether little or no activity occurs during a time period can be indicated by a binary representation. Periods of simultaneous activity of processes can then be determined by applying simple logical operations to the binary representations. Resources of the system may be reallocated based on the characterizations of the activity.