Segment Directory: An Improvement to the Pointer in Directory Cache Coherence Schemes
Jong Hyuk Choi, Kyu Ho Park · Parallel Processing Letters · 1998
We propose a new directory element called the segment directory, which is a hybrid of the full map vector and the pointer. It can be used in place of the pointer in most pointer-based directory schemes to improve directory storage efficiency: a segment directory element can point to several processors with almost the same number of bits as the pointer which can point to only one. In this paper, the segment directory is applied to four of the limited directory schemes, and performance improvement is then evaluated. The segment directory eliminates directory overflows by up to 71% and reduces the traffic and execution time of all the workloads run on the four schemes. This is the first effort in literature to reduce directory overflows themselves. Moreover, the segment directory does not introduce additional hardware overhead or protocol complexity.