PCOUNT: A power aware fetch policy in Simultaneous Multithreading processors

The Simultaneous Multithreading (SMT) architecture improves the resource efficiency via scheduling and executing concurrent threads in the same core. Moreover, fetch policies are proposed to assign priorities in the fetch stage to manage the shared resources. However, power consumption study is omitted in most fetch policies. On the other hand, the power management schemes nowadays are focused on multicore processors. Given the growing demands to manage the power consumption of processors and the fully shared system resources in SMT environment, it requires detailed research to develop the power management in an SMT processor. This paper proposes a power aware fetch policy PCOUNT, which evaluates the power consumption for two categories in SMT: computation resources and memory accessing resources. PCOUNT fetches from the thread with lowest evaluated power consumption in every CPU cycle, in order to reduce overall power consumption. Furthermore, this paper justifies studied fetch polices using power efficiency, which is calculated as evaluated power consumption per unit system throughput. As a result, PCOUNT improves power efficiency over ICOUNT by 26% and over DWarn by 31% on average. Meanwhile, PCOUNT is able to achieve better overall system throughput and average thread improvement than ICOUNT and DWarn.