A method for automatically determining performance problems in a computer system due to a metric indicating a current memory peak load in the computer system is disclosed. In order to decrease CPU consumption in large memories it is proposed to perform the steps of: a) using a cyclic stealing algorithm used in prior art for stealing subunits, if the subunits were not referenced since the last cycle and writing the subunits to a secondary memory device, with an extension for determining the age of memory subunits, wherein the extension comprises the steps of: b) writing time stamps for a subselection of the memory subunits to a data storage always when the stealing routine has processed a subselection, wherein the current time of a current cycle and the preceding current time of a preceding cycle are stored in respective entries of the data storage, for generating age information for the memory subunits, c) calculating the metric based on average age calculations including differences between a respective one of the current time and a respective one of the preceding current time of one or more of the table entries, d) determining the occurrence of a peak load, when the metric is beyond a predetermined threshold level.