VIA over SCI - consequences of a zero copy implementation, and comparison with VIA over myrinet

Abstract

An early implementation of VIA over the latest I/O based SCI hardware is presented. SCI uses a shared address space model that in principle should fit well with the goals of the VIA API. This is demonstrated with a zerocopy and two one-copy implementations of the send/receive model. The paper shows that the VIA abstractions and provisions for zero-copy maps well to the SCI hardware. However, the results indicate that for small messages, a one-copy model outperforms the zero-copy model, due to the serializing properties of the VIA synchronization messages. In addition, a performance comparison is made with two other early VIA implementations: Berkeley’s VIA over Myrinet and VIA over GM. Results from these comparisons shows that a tuned host bridge is a necessity to exploit the hardware speed offered by these PCI 64bit 66MHz interconnects.