Optimizing Point-to-Point Ethernet Cluster Communication

This work covers the implementation of a raw Ethernet communication module for the Open MPI message passing library. Thereby it focuses on both the reduction of the communication latency for small messages and maximum possible compatibility. Especially the need for particular network devices, adapted network device drivers or kernel patches is avoided. The work is divided into three major parts: First, the networking subsystem of the version 2.6 Linux kernel is analyzed. Second, an Ethernet protocol family is implemented as a loadable kernel module, consisting of a basic datagram protocol (EDP), providing connection-less and unreliable datagram transport, and a streaming protocol (ESP), providing connection-oriented, sequenced and reliable byte streams. The protocols use the standard device driver interface of the Linux kernel for data transmission and reception. Their services are made available to user-space applications through the standard socket interface. Last, the existing Open MPI TCP communication module is ported atop the ESP. With bare EDP/ESP sockets a message latency of about 30 us could be achieved for small messages, which compared to the TCP latency of about 40 us is a reduction of 25 %