Abstract: A data processing system has a virtual memory manager for swapping information between primary memory (such as RAM) and secondary memory (such as a fixed disk). The virtual memory manager employs an ager to determine which information in RAM is eligible for swapping out to the fixed disk. The ager links eligible information to an idle list. The idle list has minimum and maximum sizes. The ager has execution priorities that depend on the minimum and maximum sizes of the idle list. When the idle list is at the minimum size, the ager runs at a higher priority in order to identify information that can be swapped out. When the idle list is at or near the maximum size, the ager runs at a lower priority. The size of the idle list is dynamically adjusted to account for any information that is reclaimed from the idle list and also to account for any changes in the amount of swappable information (which is in non-resident primary memory).