A Cool Scheduler for Multi-Core Systems Exploiting Program Phases

Rapid growth of cloud computing services have led to creation of large scale enterprise data centers which consume great amounts of energy. Data centers usually have an service level agreement (SLA) between the clients and the service providers, which specify the terms and quality of service to be provided. In this paper, we consider a situation in a data center where multiple user applications are executing on a multi-core system and each application may have a specified SLA requirement. We design a voltage and frequency scheduler (the “cool” scheduler) that can be used in enterprise data centers to provide CPU energy saving under the specified SLA requirement by exploiting the applications´ run-time program phases. Our design greatly improves the computation efficiency compared to other recently published works. The scheduler is built into the Linux kernel and evaluated against SPEC CPU2006 and Phoronix Test Suite on a quad-core system. Experiment result demonstrates that our cool scheduler achieves 25.8% energy saving on average with 8.7% performance loss under the given SLA requirement (10% allowed performance loss). Our design achieves 35.8% and 31.6% more energy saving compared to two of the most advanced related works.