Kernel-Level Caching of Dynamic HTTP Content from Many Sources

Network file serving applications often use caching to increase throughput and capacity. Furthermore, caching in the operating system’s kernel multiplies these benefits. What these caches lack are the ability to receive or retrieve content from many disparate sources. Adaptive Fast Path Architecture (AFPA) [3], a network server accelerator implemented for HTTP, suffered from this same limitation. AFPA not only required the caching of static content from the file system but dynamic content generated from a myriad of sources.

This paper introduces an architecture designed specifically to address the many combinations of HTTP content sources and caching techniques required by AFPA. N-source In-kernel Cache (NICache) is an in-kernel cache capable of caching both application-specific and application-independent data and delivering it via any application protocol. Data may come from a variety of sources and may be stored in the kernel using numerous kernel specific mechanisms. NICache provides a framework for a generic multiple source, in-kernel cache that provides extensive flexibility without negatively affecting performance for static content and potentially significantly increasing the performance of serving dynamic content. NICache has been implemented on Linux and Windows 2000 for an HTTP reverse-proxy cache, AFPA.