Project Description

Adaptive Fast Path Architecture (AFPA) is a software architecture for high-performance network servers. The architecture is specifically designed to be general purpose. However, most of our work to date has focused on Web servers. AFPA provides a framework that includes three main components: a RAM-based cache, a reverse, split-connection proxy, and a layer-7 (also known as content-based) router. The cache allows AFPA to serve static content efficiently. The proxy distributes requests for dynamic content (that cannot be cached) to a set of "back-end" servers. The layer-7 router can be configured to identify which requests are handled by the cache and proxy respectively, based on URL path and extension (MIME type).

All three components are implemented in the operating system kernel for maximum efficiency. Efficiency is a primary concern for AFPA. In-kernel implementation is only one of many techniques used to improve performance. AFPA has allowed IBM to achieve a leadership position in Web server performance. By conservative estimates, AFPA more than doubles the performance of conventional Web servers for serving static content. Running on a uniprocessor 450 MHz Pentium II Xeon system, Linux AFPA can deliver in excess of 10,000 SPECweb96 responses per second which represents more than a gigabit per second of response bandwidth. Additional benchmark results are available at the SPECweb Web site.

Journal Publications

• "High-Performance Memory-Based Web Servers: Kernel and User-Space Performance," P. Joubert, R. King, R. Neves, M. Russinovich, and J. Tracey, to appear in Proceedings of 2001 USENIX Annual Technical Conference (Boston, MA, June 25-30), June 2001.