Energy harvesting systems have shown their unique benefit of ultra-long operation time without maintenance and are expected to be more prevalent in the era of Internet of Things. However, due to the batteryless nature, they suffer unpredictable frequent power outages. They thus require a lightweight mechanism for crash consistency since saving/restoring checkpoints across the outages can limit forward progress by consuming hard-won energy. For the reason, energy harvesting systems have been designed with a non-volatile memory (NVM) only. The use of a volatile data cache has been assumed to be not viable or at least challenging due to the difficulty to ensure cacheline persistence. In this paper, we propose ReplayCache, a software-only crash consistency scheme that enables commodity energy harvesting systems to exploit a volatile data cache. ReplayCache does not have to ensure the persistence of dirty cachelines or record their logs at run time. Instead, ReplayCache recovery runtime re-executes the potentially unpersisted stores in the wake of power failure to restore the consistent NVM state, from which interrupted program can safely resume. To support store replay during recovery, ReplayCache partitions program into a series of regions in a way that store operand registers remain intact within each region, and checkpoints all registers just before power failure using the crash consistency mechanism of the commodity systems. For performance, ReplayCache enables region-level persistence that allows the stores in a region to be asynchronously persisted until the region ends, exploiting ILP. The evaluation with 23 benchmark applications show that compared to the baseline with no caches, ReplayCache can achieve about 10.72x and 8.5x-8.9x speedup (on geometric mean) for the scenarios without and with power outages, respectively.
Accelerating Non-volatile/Hybrid Processor Cache Design Space Exploration for Application Specific Embedded Systems
在这篇文章中，我们提出了一种技术，以加速非易失性或混合的易失性和非易失性处理器高速缓存设计空间探索的应用程序特定的嵌入式系统。利用一种新的高速缓存行为建模方程和一个新的准确的高速缓存未命中预测机制，我们提出的技术可以加速NVM或混合FIFO处理器的高速缓存设计空间探索的SPEC CPU 2000应用程序高达249倍，相比传统的方法。
