Evaluating Content Management Techniques for Web Proxy Caches Martin Arlitt, Ludmila Cherkasova, John Dilley, Rich Friedrich and Tai Jin Proceeding on Second Workshop Internet Server Performance May 1999 Chun-Fu Kung System Laboratory, Dept. of Computer Engineering and Science Yuan-Ze University 2000/9/13

Outline  Workload characteristics  Experimental design  Simulation result  Virtual cache  Conclusion

Workload Characteristics  Current web proxy caches utilize simple replacement policies to determine which files to retain in the cache.  Access log: cable modem users, five months and 115 million requests for 1.3 TB of data.  Cacheable objects (92% for cacheable objects)  Object set size (large object set size)  Object size (4KB~148MB)

Workload Characteristics(cont.)  Recency of reference (1/3 rereference in one hour and approximately 2/3 rereference in 24 hours)  Frequency of reference (over 60% access only a single time, we call these objects as “one-timers”)  Turnover (objects were once popular in the past)

Experimental Design  Least-Recency-Used (LRU)  SIZE  GreedyDual-Size (GD-Size)  Least-Frequency-Used (LFU)  GreedyDual-Size with Frequency (GDSF)  Least Frequency Used with Dynamic Aging (LFU-DA)

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Virtual Cache  We developed an approach that can focus on both of these metrics simultaneously.  Replacements from VC i are moved to VC i+1.  Replacements from VC n-1 are evicted from the cache.  All objects that are reaccessed while in the cache are reinserted in VC 0.

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Conclusion  Our results indicate that size-based algorithm achieve higher hit rates than other algorithms.  We also found that frequency-based algorithm are more effective at improving the byte hit rate of a proxy cache.  We have developed virtual caches as an approach to provide optimal cache performance for multiple metrics simultaneously.