CTP: A scheduling strategy to smooth response time fluctuations in multi-tier website system

Performance, in terms of quality of service and resource utilization, is one of top attractions in cloud. However, in practice, most multi-tier applications today frequently present large scale fluctuations of response time during periods of high resource utilization. It is hardly to find any reported work that elaborated the reasons causing response time fluctuations, especially when providing quality performance and high effective multi-tier systems in cloud environments. To this end, this paper, through extensive measurements of a multi-tier application benchmark (RUBiS), corroborates the existing of response time fluctuations. In addition, arithmetic mean of response time is not suitable for the measurement of multi-tier services system performance. In light of probing analysis of requests, we show that the large scale response time fluctuations can be caused by concurrent long or mix transactions. The numerical results validate the correctness of our findings. Consequently, an effective scheduling policy called CTP (cross-tier-proportion) is developed to smooth response time fluctuations while maintaining high resource utilization in the system.