Insights on the Performance of Cache Management Policies for Fragment-Assembling Caches

The Edge Side Includes (ESI) standard enables Web proxy caches to deliver dynamic web content, such as personalized portal pages and e-business queries, by assembling it on demand from page templates and content fragments retrieved from local caches or remote servers.

This paper investigates whether ESI caches can benefit from exploiting the structure of the composed pages. Toward this end, we view the space of dynamic pages as a partition defined by page templates; the fragments used for each template are grouped in classes, based on the ESI tags that define them. Thus a dynamic page is composed from a page template and one fragment from each of the associated classes.

We consider two components of the cache management infrastructure: the replacement policy and the space allocation. Our experiments show that replacement policies that account for page-structure dependencies can improve hit ratios in comparison to Greedy-Dual Size-Frequency policy. Similarly, partitioning the cache space among fragment classes can improve hit ratios in comparison to sharing the entire cache space among all fragment classes, as traditionally used. The study is conducted through simulation with simple synthetic workloads.