Efficient parallel processing on low-cost clusters with GAMMA active ports

Abstract

The Genoa Active Message MAchine (GAMMA) is an efficient communication layer for 100base-T clusters of Personal Computers under the Linux operating system (OS). It is based on Active Ports, a communication mechanism derived from Active Messages. Active Ports share most of the low-level optimization opportunities with Generic Active Messages while offering a higher-level programming interface not only in the SPMD but also in the MIMD and client/server paradigms. In addition to point-to-point communications, multi-cast, barrier synchronization, scatter, and gather primitives have also been developed based on Active Ports and exploiting shared 100base-T LAN technology in an optimal way. GAMMA Active Ports deliver excellent communication performance at the user level (latency 13 μ s, maximum throughput 12.2 MByte/s, half-power point reached with 200 byte long messages), thus enabling cost-effective cluster computing on 100base-T. Despite being implemented at the kernel level in the Linux OS, performance numbers of GAMMA Active Ports are much better than many other LAN-oriented communication layers, including so called “user-level” ones (e.g. U-Net). Some code porting efforts have already shown that several applications are reasonably easy to develop on top of GAMMA and that they can actually take advantage of the efficient point-to-point as well as collective communication primitives offered by our prototype library implementation. A porting of the MPICH higher-level interface atop GAMMA is currently under way.