Eeect of Virtual Channels and Memory Organization on Cache-coherent Shared-memory Multiprocessors

In this paper, performance of wormhole routed 2-D torus network with virtual channels has been evaluated for cache-coherent shared-memory multiprocessors with execution-driven simulation using various applications. The traac in such systems is very diierent from the traac in message-passing environment and is characterized by traac bursts, one-to-many and many-to-one traac, and small xed length messages. We show the impact of various network parameters, such as number of virtual channels, number of it buuers per virtual channel, and number of internal links. We have also considered low-order and high-order interleaving of memory blocks on nodes to show its impact on the network performance. The study shows that 4 virtual channels per link is most eecient for 2-D torus networks. The number of it buuers per virtual channel also has a considerable impact and 2 to 4 it buuers are usually enough. The number of internal links also has an impact on the performance for applications, such as MP3D, that generate large contention for shared variables. Larger number of internal links are also useful in case of high-order interleaved memory to reduce hot-spots at the communication interface of favorite nodes.