Abstract

On these cluster systems, parallel processing is usually accomplished through parallel programming libraries such as MPI, PVM [Geist], and BSP [Jonathan]. These environments provide well-defined portable mechanisms for which concurrent applications can be developed easily. In particular, MPI has been widely accepted in the scientific parallel computing area. The use of MPI has broadened over time as well. Two of the most extensively used MPI implementations are MPICH [Gropp], [Gropp2] from Mississippi State University and Argonne National Laboratory and LAM [LSC] originally from Ohio Supercomputing Center. LAM is now being maintained by the University of Notre Dame. The modular design taken by MPICH and LAM has allowed research organizations and commercial vendors to port the software to a great variety of multiprocessor and multicomputer platforms and distributed environments.

Naturally, there has been great interest in the performance of LAM and MPICH for enabling high-performance computing in clusters. Large scale distributed applications using MPI ( either LAM or MPICH ) as communication transport on a cluster of computers impose heavy demands on communication networks. Gigabit Ethernet technology, among others high-speed networks, can in principle provide the required bandwidth to meet these demands. Moreover it also holds the promise of considerable price reductions, possibly even to commodity levels, as Gigabit over copper devices become more available and use increases. However, it has also shifted the communication bottleneck from network media to protocol processing. Since LAM and MPICH use TCP/UDP socket interfaces to communicate messages between nodes, there have been great efforts in reducing the overhead incurred in processing the TCP/IP stacks. However, the efforts have yielded only moderate improvement. Since then, many systems such as U-Net [Welsh], BIP [Geoffray], and Active Message [Martin] have been proposed to provide low latency and high bandwidth message-passing between clusters of workstations and I/O devices that are connected by a network. More recently, the Virtual Interface Architecture (VIA) [Compaq] has been developed to standardize these ideas. VIA defines mechanisms that will bypass layers of protocol stacks and avoid intermediate copies of data during sending and receiving messages. Elimination of this overhead not only enables significant communication performance increases but will also result in a significant decrease in processor utilization by the communication subsystem. Since the introduction of VIA, there have been several software and hardware implementations of VIA. Berkeley VIA [Buonadonna], Giganet VIA [Speight], M-VIA [MVIA], and FirmVIA [Banikazemi] are among these implementations. This has also led to the recent development of VIA-based MPI communications libraries, noticeably MVICH [MVICH].

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