Speculative paging for future NVM storage
Viacheslav V. Fedorov, Jinchun Kim, Mian Qin, Paul V. Gratz, A. L. Narasimha Reddy · Proceedings of the International Symposium on Memory Systems · 2017
The quest for greater performance and efficiency has driven modern cloud applications towards "in-memory" implementations, such as memcached and Apache Spark. Looking forward, however, the costs of DRAM, due to its low area density and high energy consumption, may make this trend unsustainable. Traditionally, OS paging system mechanisms were intended to bridge the gap between expensive, under-provisioned DRAM and inexpensive, dense storage, however, in the past twenty years the latency of storage, relative to DRAM became too great to overcome without significant performance impact. Recent NVM storage devices, such as Intel Optane drives and aggressive, 3D flash SSDs, may dramatically change the picture for OS paging. These new drives are expected to provide much lower latency compared to the existing flash-based SSDs or traditional HDDs. Unfortunately, even these future NVM drives are still much too slow to replace DRAM, since the access latency of fast NVM storage is expected on the order of tens of microseconds, and they often require block-level access. Unlike traditional HDDs, for which the baseline OS paging policies are designed, these new SSDs place no penalty for "random" access and their access latency promises to be significantly less than traditional SSDs, thus arguing for a rearchitecting of the OS paging system.