Abstract

Parallel execution can enhance the performance of distributed client-server systems, but the enhancement may be less than expected. Evaluations of such designs must include the complex effects of overheads, heterogeneous parallel branches, contention by the parallel parts for servers in lower levels, and simultaneous resource possession effects. A "compensated complementary delay" approximation is described which exploits layered queueing approximations for layered resources which occur in client-server architectures, based on synchronization delay estimates and adjusted levels of contention. The new approximation uses the overlap of parallel branches and a new fast calculation of join delays. It gives acceptable errors (averaging about two percent), and has an enormously lower computational cost compared to the competing approach based on decomposition. The new approximation may moderate a conclusion made by Heidelberger and Trivedi, that decomposition gives greatly superior accuracy ...

Citations