The hardware/software balancing act for information retrieval on symmetric multiprocessors

Abstract

Web search engines, such as AltaVista and Infoseek, handle tremendous loads by exploiting the parallelism implicit in their tasks and using symmetric multiprocessors to support their services. The web searching problem that they solve is a special case of the more general information retrieval (IR) problem of locating documents relevant to the information need of users. In this paper, we investigate how to exploit a symmetric multiprocessor to build high performance IR servers. Although the problem can be solved by throwing lots of CPU and disk resources at it, the important questions are how much of which hardware and what software structure is needed to effectively exploit hardware resources. We have found, to our surprise, that in some cases adding hardware degrades performance rather than improves it. We show that multiple threads are needed to fully utilize hardware resources. Our investigation is based on InQuery, a state-of-the-art full-text information retrieval engine.