Parallel Logic Programs on the Mayfly

The Mayfly, a parallel processor being built at HP Labs in Palo Alto, has architectural support for several important aspects of the OM virtual machine for parallel logic programs. Each node has an extra processor that is able to relieve the main processor of a significant amount of the “housekeeping” work of memory management, task switching, and message handling. This paper describes how the second processor implements kernel level functions in OM, with particular attention to the operations that support task switching and task allocation. The paper includes detailed timing data from a program with interleaved parallel threads to show that while the main processor is busy in one thread the kernel processor can effectively build the context for the next thread, significantly reducing task switching time.