Abstract-Asymmetric multi-core processors (AMPs) comprise cores with different sizes of micro-architectural resources yielding very different performance and energy characteristics. Since the computational demands of workloads vary from one task to the other, AMPs can often provide a higher power efficiency than symmetric multi-cores. Furthermore, as the computational demands of a task change during its course of execution, reassigning the task from one core to another, where it can run more efficiently, can further improve the overall power efficiency. However, too frequent re-assignments of tasks to cores may result in high overhead. To greatly reduce this overhead, we propose a morphable core architecture that can dynamically adapt its resource sizes, operating frequency and voltage to assume one of four possible core configurations. Such a morphable architecture allows more frequent task to core configuration re-assignments for a better match between the current needs of the task and the available resources. To make the online morphing decisions we have developed a runtime analysis scheme that uses hardware performance counters. Our results indicate that the proposed morphable architecture controlled by the runtime management scheme, can improve the throughput/Watt of applications by 31% over executing on a static out-of-order core while the previously proposed big/little morphable architecture achieves only a 17% improvement.
Asymmetric multicore processors (AMPs) consist of cores executing the same ISA, but di↵ering in microarchitectural resources, performance, and power consumption. As the computational bottleneck of a workload shifts from one resource to the next, during its course of execution, reassigning it to the core where it runs most e ciently can improve the overall energy e ciency. Simulation studies show that the performance bottlenecks can shift frequently, often within a few thousands cycles. With frequent core hooping, the overhead of thread migration becomes significant. To mitigate this overhead, we propose a morphable core that can assume one of four possible configurations to address the dominant performance bottlenecks, while retaining the same cache and registers. This way the architectural state remains intact while the morphable core is reconfigured in resources and frequency. We then implement a runtime scheme to decide the best configuration to run on and switch configuration as necessary. Simulation results indicate that on the average, the proposed scheme results in performance/watt improvement of 41%.
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