Optimum choice of page sizes in a virtual memory with a hardware executive and a rapid-access secondary storage medium

A paged virtual memory system with a finite number n≥1 of page sizes, containing a hardware executive and a rapid-access secondary storage medium is considered. It is postulated that in such a system the smallest page size will be chosen small enough to render internal fragmentation negligible, and that this page size C1 will be fixed independently of the other page sizes. The problem of choosing the remaining page sizes is then cast as a problem of minimizing the bookkeeping space for page tables in the hardware executive, on the average, with the assumption that the probability distribution of segment sizes is known. The mathematical problem is solved for the uniform and exponential distributions and numerical results are given for the Poisson and an empirically determined distribution. These results indicate a rule of thumb which may be used to choose the remaining page sizes. Finally, the results are compared with paging with a single page size.