Design and Performance of a Web Server Accelerator

We describe the design, implementation and performance of a Web server accelerator which runs on an embedded operating system and improves Web server performance by caching data. The accelerator resides in front of one or more Web servers. Our accelerator can serve up to 5000 pages/second from its cache on a 200 MHz PowerPC. This throughput is an order of magnitude higher than that which would be achieved by a high-performance Web server running on similar hardware under a conventional operating system such as Unix or NT. The superior performance of our system results in part from its highly optimized communications stack. In order to maximize hit rates and maintain updated caches, our accelerator cache provides API's which allow application programs to explicitly add, delete, and update cached data. We analyse the SPECweb96 benchmark, and show that the cache can provide high hit ratios and excellent performance for workloads similar to this benchmark.