Parallel execution can enhance the performance of distributed client-server systems, but the enhancement may he less than expected. Evaluations of such deszgns must include the complex effects of overheads, heterogeneous parallel branch,es, contention by the parallel parts for servers in lower levels, and simultaneous resource possession effects. A "compensated complelnentary delay" approximation is described which explozis layered queuean,g approEzmations for layered re- .sources tuhach occur in client-server architectures, based on synchronazation dela,y estimates and adjusted levels of conieniion. The new approximataon 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 competang approach based on decompositzon. The new approximation may moderate a conclusion made by Heidelberger and Trivedi, that decomposition gives greatly superior accuracy to the much cheaper complementary delay approach; these delay approximations are only a little less accurate.
1st International Workshop on Software and Performance, WOSP 1998
Department of Systems and Computer Engineering

Franks, G, & Woodside, C.M. (1998). Performance of multi-level client-server systems with parallel service operations. In Proceedings of the 1st International Workshop on Software and Performance, WOSP 1998 (pp. 120–130). doi:10.1145/287318.287343