Scalable persistent memory (PM) has opened up new opportunities for building indexes that operate and persist data directly on the memory bus, potentially enabling instant recovery, low latency and high throughput. When real PM hardware (Intel Optane DCPMM) first became available, previous work evaluated PM indexes proposed in the pre-Optane era. Since then, newer indexes based on real PM have appeared, but it is unclear how they compare to each other and to previous proposals, and what further challenges remain. This paper addresses these issues by analyzing and experimentally evaluating state-of-the-art PM range indexes built for real PM. We find newer designs inherited past techniques with new improvements, but they do not necessarily outperform pre-Optane era proposals. Moreover, PM indexes are often also very competitive or even outperform indexes tailored for DRAM, highlighting the potential of using a unified design for both PM and DRAM. Functionalitywise, these indexes still lack good support for variable-length keys and handling NUMA effect. Based on our findings, we distill new design principles and highlight future directions.
翻译:可缩放的持久性记忆(PM)为建立直接在记忆总线上运行和持续数据的指数开辟了新的机会,这有可能促成即时恢复、低悬浮度和高输送量。当实际的PM硬件(Intel Optane DCPM)首次出现时,以前的工作评价是在奥普坦时代之前提出的PPM指数。此后,基于实际的PM的更新指数出现了,但还不清楚它们如何相互比较和以往的提案,以及还存在哪些进一步的挑战。本文件通过分析和实验性地评价为实际的PM建立的最新PM范围指数来解决这些问题。我们发现较新者用新的改进方法来设计遗留下来的过去技术,但是它们并不一定超过Optane时代前的建议。此外,PM指数也常常非常具有竞争力,甚至超出为DRAM定制的指数。强调对PM和DRAM使用统一设计的潜力。从功能上看,这些指数仍然缺乏对可变长键和处理NUMA效应的良好支持。基于我们的调查结果,我们提出了新的设计原则并突出未来方向。