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In this paper, we propose a new approach for the development of load control policies in autonomic multitier systems. We control system load in a completely new way compared to existing policies: we leverage on the autocorrelation of service times and show that autocorrelation can be used to forecast future service requirements of requests and adaptively control system load. To the best of our knowledge, this is the first direct application of autocorrelation of service times to autonomic load control. We propose ALoC and D ALoC, two autocorrelation-driven policies that drop a percentage of the load in order to meet pre-defined quality-of-service levels in a distributed system. Both policies are easy to implement and rely on minimal assumptions. In particular, D ALoC is a fully no-knowledge measurement-based policy that self-adjusts its load control parameters based only on policy targets and on statistical information of requests served in the past. We illustrate the effectiveness of these new policies in a distributed multi-server setting via detailed trace driven simulations. We show that if these policies are employed in the server with a temporal dependent service process, then end-to-end response time, across all servers, reduces up to 80% by only dropping at most 13% of the incoming requests. Using real traces, we also show that, in the constrained case of being able to drop only from a portion of the incoming workload, our policy still improves request response time by up to 30%.
Date of Conference: 21-23 Sept. 2009