Manu Thapar

Linked list cache coherence for scalable shared memory multiprocessors

This paper presents a singly-linked distributed directory (SDD) cache coherence protocol and compares the performance of the SDD protocol with the fully mapped centralized directory protocol and the IEEE SCI Standard protocol. To maintain coherence, the SDD protocol uses a linked list of cache lines that contain shared copies of the data. The protocol has scalable cost. Coherency related messages are not required to be delivered in order, thus allowing adaptive routing, making the performance more robust in the presence of congested networks. The authors analysis shows that the SDD protocol has generally better performance in the presence of memory and interconnect contention. They discuss the various factors, such as memory reference behavior and interconnect traffic, that affect the performance of these protocols.<<ETX>>

Interleaved dual tag directory scheme for cache coherence

Shared memory multiprocessors generally use caches to improve the performance. This introduces the cache coherence problem. Multiple copies of the data need to be kept consistent by using a suitable mechanism. The paper presents a novel mechanism for organizing the memory modules in order to provide an inexpensive implementation for cache coherence. The interleaved directory scheme uses a unique address mapping to ensure a proper distribution of the directory that holds information regarding cached copies in the system. The memory requirement for the directory is significantly less than current directory schemes and there is no extra interconnect traffic generated by the scheme.<<ETX>>