Adaptive Fast Path Architecture (AFPA) is a software architecture that dramatically improves the efficiency, and therefore the capacity, of Web and other network servers. The architecture includes a RAM-based cache that serves static content and a reverse proxy that can distribute requests for dynamic content to multiple servers. These two mechanisms are combined using a flexible layer-7 (content-based) routing facility. The architecture defines interfaces that allow these generic mechanisms to be exploited to accelerate a variety of application protocols including HTTP. Efficiency is derived from maximizing the number of requests that are handled entirely within the kernel using a deferred interrupt context instead of threads wherever possible. AFPA has been implemented on several server platforms including Windows NT and Windows 2000, OY390, AIX, and most recently Linux. By conservative estimates, AFPA more than doubles capacity for serving static content compared to conventional server architectures and has allowed IBM to establish a leadership position in Web server performance. A prototype implementation of AFPA on Linux delivers more than 10,000 SPECWeb96 operations per second on a single processor.
By: Elbert C. Hu, Philippe A. Joubert, Robert B. King, Jason D. LaVoie, John M. Tracey
Published in: RC22030 in 2001
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