EXPLOITING OPERATING SYSTEM SUPPORT FOR DYNAMIC PAGE PLACEMENT ON A NUMA SHARED MEMORY MULTIPROCESSOR

Shared memory multiporcessors are attractive because they are programmed in a manner similar to uniprocessors. The UMA class of shared memory multiprocessors is the most attractive, from the programmer's point of view, since the programmer need not be concerned with the placement of code and data in the physical memory hierarchy. Scalable shared memory multiprocessors, on the other hand, tend to present at least some degree of non-uniformity of memory access to the programmer, making the NUMA class an important one to consider. In this paper, we investigate the role that DUnX, an operating system supporting dynamic page placement on a BBN GP1000, might play in simplifying the memory model presented to the applications programmer. We consider a case study of psolu, a real scientific application originally targeted for a NUMA architecture. We find that dynamic page placement can dramatically improve the performance of a simpler implementation of psolu targeted for an UMA memory architecture. The addition of a phase change hint to the UMA version of psolu enables the operating system to further improve performance, approaching that of the hand-tuned NUMA implementation.