CapOS: Capacitor Error Resilience for Energy Harvesting Systems
CapOS: Capacitor Error Resilience for Energy Harvesting Systems
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DOI：
10.1109/tcad.2022.3202861
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发表时间：
2022-11
影响因子：
2.9
通讯作者：
Jongouk Choi;Hyunwoo Joe;Changhee Jung
中科院分区：
文献类型：
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作者：
Jongouk Choi;Hyunwoo Joe;Changhee Jung
能量收集系统已经成为电池供电的物联网（IoT）设备的替代方案。为了在没有电池的情况下处理频繁的停电，能量收集系统依赖于电容器支持的检查点机制，也称为即时（JIT）检查点。它在断电发生之前（使用电容器中缓冲的能量）在非易失性存储器（NVM）中检查点易失性数据，并在断电之后从NVM恢复检查点数据。虽然JIT检查点给人一种错觉，即易失性数据在停电时可以像非易失性数据一样保存下来，但事实证明，由于电容器退化，能量收集系统可能意外地使JIT检查点失败，从而在停电期间丢失或损坏数据。为了解决这个问题，本文提出了一个操作系统驱动的解决方案，称为CapOS。在高水平上，CapOS以无功但安全的方式诊断电容器。当JIT检查点发生故障时，CapOS检测到电容降级而不会导致数据损坏。为了从这样的电容器错误中恢复，CapOS电气隔离了退化的电容器，以便它借助电容器的弹性特性自行恢复其原始电容，并禁用JIT检查点。如果在电容器隔离期间发生停电，CapOS将利用撤销日志记录和基于间隔的检查点进行恢复。一旦电容完全恢复，CapOS就会回到基于电容的JIT检查点。实验结果表明，CapOS可以在不影响停电恢复的前提下，以较低的运行成本有效地解决能量收集系统的电容误差问题。
Energy harvesting systems have emerged as an alternative to battery-operated Internet of Things (IoT) devices. To deal with frequent power outages in the absence of battery, energy harvesting systems rely on a capacitor-backed checkpoint mechanism also known as just-in-time (JIT) checkpointing. It checkpoints volatile data in nonvolatile memory (NVM) just before a power outage occurs—using the energy buffered in the capacitor—and restores the checkpointed data from NVM in the wake of the outage. While the JIT checkpointing gives an illusion that volatile data survive a power outage as if they were nonvolatile, it turns out that due to capacitor degradation, energy harvesting systems can unexpectedly fail the JIT checkpointing, losing or corrupting data across the outage. To address the problem, this article presents an operating system-driven solution called CapOS. At a high level, CapOS diagnoses the capacitor in a reactive yet safe manner. When the JIT checkpoint failure occurs, CapOS detects the capacitor degradation without causing the data corruption. To recover from such a capacitor error, CapOS electrically isolates the degraded capacitor—so that it restores its original capacitance by itself with the help of capacitor’s resilient nature—and disables the JIT checkpointing. In case, power outages occur during the capacitor isolation, CapOS leverages undo logging with interval-based checkpointing for their recovery. Once the capacitor is fully recovered, CapOS gets back to the capacitor-based JIT checkpointing. The experimental results demonstrate that CapOS can effectively address the capacitor error of energy harvesting systems at a low run-time cost, without compromising the recovery of power outages.