Providing Di erentiated Levels of Service in Web Content

Web content hosting, in which a Web server stores and provides Web access to documents for diierent customers, is becoming increasingly common. Due to the variety of customers (corporate, individuals, etc.), providing diierentiated levels of service is often an important issue for the hosts. Most server implementations , however, are not structured to service requests based on diierent levels of quality of service (QoS). This paper presents our attempts at augmenting a popular server implementation with diierenti-ated QoS features. We explore priority-based request scheduling at both user and kernel levels. We nd that simple strategies such as controlling the numbers of processes can improve the response time of high-priority requests notably while preserving the system throughput. We also nd that the kernel-level approach tends to penalize low-priority requests less signiicantly than the user-level approach, while improving the performance of high-priority requests similarly. Based on our experiments, we discuss the bottlenecks and limitations from kernel implementations that prevent the augmented server from achieving better performance.