Too Many Words, Too Little Time: Accelerating Real-Time Keyword Scanning with Multi-Core Processors

Our digital universe is growing, creating exploding amounts of data which need to be searched, protected and filtered. String searching is at the core of the tools we use to curb this explosion, such as search engines, network intrusion detection systems, spam filters, and anti-virus programs. But as communication speed grows, our capability to perform string searching in real-time seems to fall behind. Multi-core architectures promise enough computational power to cope with the incoming challenge, but it is still unclear which algorithms and programming models to use to unleash this power.

We have parallelized a popular string searching algorithm, Aho-Corasick, on the IBM Cell/B.E. processor, with the goal of performing exact string matching against large dictionaries. In this article we propose a novel approach to fully exploit the DMA-based communication mechanisms of the Cell/B.E. to provide an unprecedented level of aggregate performance with irregular access patterns.

We have discovered that memory congestion plays a crucial role in determining the performance of this algorithm. We discuss three aspects of congestion: memory pressure, layout issues and hot spots, and we present a collection of algorithmic solutions to alleviate these problems and achieve quasi-optimal performance.

The implementation of our algorithm provides a worst-case throughput of 2.5 Gbps, and a typical throughput between 3.3 and 4.4 Gbps, measured on realistic scenarios with a two-processor Cell/B.E. system.

By: Oreste Villa; Daniele Paolo Scarpazza; Fabrizio Petrini

Published in: RC24488 in 2008


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to .