Tiled Virtual Memory for UNIX

M.Ly computer applications require the manipulation of large data arrays. These applÍcations can behave b-adly under a paged virtual memory (vM) system, due to poor memory access _p¿tterns. One solution to this problem is tiling, a technique in which the arays are partitioned into sub-arrays that map one-to-one with VM -pages. Software implementations of tiling have been described in the literature, but none pioviAe the speed and application transparency of a hardware solution. We have implemented a hardware based, tiled VM within a version of the UNIX operating system. Based on a novel memory management unit and supporting kemel software, this tiled VM has proven to be an efficient environment for manipulaiing 2-dimensional arrays of data In this paper we discuss the kemel changes required to implement our tiled VM. We then compare tiled and paged versions of our VM system, and show that tiling results in a 5Q-fold reduction in working set size for a common class of image processing algorithms.