Several emerging non-volatile memory (NVM) technologies are rising as interesting alternatives to build the Last-Level Cache (LLC). Their advantages, compared to SRAM memory, are higher density and lower static power, but each write operation slightly wears out the bitcell, to the point of losing its storage capacity. In this context, this paper proposes a new LLC organization designed to extend the lifetime of the NVM data array and a methodological proposal to forecast in detail the capacity and performance of NVM caches over its lifetime. Data compression is one of the techniques dealing with the degradation of a NV-LLC, as it decreases the write bandwidth delivered to the cache. The proposed NV-LLC organization takes advantage of compression, but with a relevant contribution: as capacity is reduced by write wear, degraded cache frames can allocate blocks whose compressed size is adequate. From a methodological point of view, although different approaches are used in the literature to analyze the degradation of a NV-LLC, none of them allows to study in detail its temporal evolution. In this sense, this work proposes a forecast procedure that combines detailed simulation and prediction, allowing an accurate analysis of the impact of different cache control policies and mechanisms (replacement, wear leveling, compression, etc.) on the temporal evolution of the indices of interest, such as the effective capacity of the NV-LLC or the system IPC. The proposed NV-LLC organization has a small added cost compared to that of a baseline NV-LLC without compression in terms of area, latency and energy consumption, and increases up to 6-36 times the time required to reach 50% effective capacity in an STT-RAM-based NV-LLC.
翻译:一些新兴的非挥发性内存(NVM)技术正在上升,作为建立最后一级缓存(LLC)的有趣替代方法。与SRAM记忆相比,其优点是密度较高,静态电量较低,但每个写式操作都略微磨损比特细胞,以致于失去存储能力。在此背景下,本文件提议一个新的LLC组织,旨在延长NVM数据阵列的寿命,并提出一项方法建议,详细预测NV-LC缓存在其寿命期内的能力和性能。数据压缩是处理NV-LAC退化的技术之一,因为它减少了向缓存提供的写带宽度。拟议的NV-LC组织利用了压缩的优势,但做出了相关贡献:随着写式磨损能力减少,退化的缓存框架可以分配压缩容量足够的区块。从方法角度看,虽然在文献中使用了不同的方法来分析NIP-LC的退化情况,但其中没有任何一种方法可以详细研究其时间演变情况。在这方面,这项工作提出了一种预测程序,即不将NV-LC系统的详细模拟和预测,可以精确地分析S-LLLLL值的递增量能力,从而可以精确地分析S-LLLLLLLLLLLLC的汇率的影响。