Circuits, methods, and apparatus for efficiently storing page characteristics. Page characteristics for memory pages are stored post address translation using addresses for physical locations in memory, for example, in a bit vector. The characteristics may include access or dirty bits, as well as other types of information. These bit vectors can also be stored and accumulated to generate histogram data. Two bit vectors may be included, while a first bit vector is written to, another is used. After data has been written to the first, the bit vectors are flipped, and data is written to the second while the first is used.