Breaking the Complexity Barrier: Enhancing Quality of Service in Simultaneous Multithreading Processors

Within the wide variety of applications running in the cloud, demands for service quality and performance guarantees need special attention. Since cloud nodes typically utilize Simultaneous Multithreading (SMT) cores, processor resources may need to be shared and managed among multiple applications. A customer application that demands high levels of Quality of Service (QoS) may require more resources than its best-effort allocated share. QoSMT is an earlier study that focuses on 2-thread SMT cores to address this issue. While a simple relationship between two threads may be relatively straightforward to manage, the interactions among multiple threads can quickly become highly complex and difficult to design and maintain. In this paper, we extend the original QoSMT study to 4-thread SMT cores by proposing three alternative scheduling algorithms that regulate resource usage between a high-priority thread and three ordinary batch-type threads. On average, we achieve 7.2% better overall throughput and up to 218% better throughput for the latency-sensitive, high-priority thread. More than 92% of 600 workloads display higher performance than the baseline configuration, and 8% of workloads perform ten times better compared to a traditional 4-thread baseline SMT with unmanaged resources.