CARB: A C-State Power Management Arbiter for Latency-Critical Workloads
Xin Zhan, Reza Azimi, Svilen Kanev, David M. Brooks, Sherief Reda · IEEE Computer Architecture Letters · 2016
Latency-critical workloads in datacenters have tight response time requirements to meet service-level agreements (SLAs). Sleep states (c-states) enable servers to reduce their power consumption during idle times; however entering and exiting c-states is not instantaneous, leading to increased transaction latency. In this paper we propose a c-state arbitration technique, CARB, that minimizes response time, while simultaneously realizing the power savings that could be achieved from enabling c-states. CARB adapts to incoming request rates and processing times and activates the smallest number of cores for processing the current load. CARB reshapes the distribution of c-states and minimizes the latency cost of sleep by avoiding going into deep sleeps too often. We quantify the improvements from CARB with memcached running on an 8-core Haswell-based server.