Speculative paging for future NVM storage
Speculative paging for future NVM storage
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未来 NVM 存储的推测分页
DOI：
10.1145/3132402.3132409
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
A. Reddy
中科院分区：
文献类型：
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作者：
Viacheslav V. Fedorov;Jinchun Kim;Mian Qin;Paul V. Gratz;A. Reddy
对更高性能和效率的追求推动了现代云应用程序走向“内存中”实现，例如memcached和Apache Spark。然而，展望未来，DRAM的成本，由于其低面积密度和高能耗，可能使这一趋势不可持续。传统上，OS分页系统机制旨在桥接昂贵的、供应不足的DRAM与廉价的、密集的存储之间的差距，然而，在过去的二十年中，存储相对于DRAM的延迟变得太大而无法在没有显著的性能影响的情况下克服。最近的NVM存储设备，如英特尔Optane驱动器和激进的3D闪存SSD，可能会显着改变操作系统分页的画面。与现有的基于闪存的SSD或传统HDD相比，这些新驱动器预计将提供更低的延迟。不幸的是，即使这些未来的NVM驱动器仍然太慢而不能取代DRAM，因为快速NVM存储的访问延迟预计在几十微秒的量级，并且它们通常需要块级访问。与传统的HDD不同，这些新的SSD不会对“随机”访问进行惩罚，并且它们的访问延迟有望显著低于传统SSD，因此主张重新设计OS分页系统。在本文中，我们提出了SPAN（未来的NVM存储的推测PAG），一个软件，操作系统交换为基础的，页面管理和预取计划设计新兴的NVM存储。与针对传统旋转磁盘进行高度优化的基线OS交换机制不同，SPAN利用NVM设备的固有并行性，从NVM存储器主动获取一组页面到小型快速主DRAM。这样做，与交换到具有基线操作系统的NVM相比，SPAN产生约18%的加速（基线操作系统与将整个工作集放置在DRAM存储器中相比，性能损失约50%）。因此，所提出的技术，使利用这种混合系统的存储器饥饿的应用程序，降低存储器成本，同时保持性能可比的DRAM的唯一的系统。
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. In this paper, we propose SPAN (Speculative PAging for future NVM storage), a software-only, OS swap-based, page management and prefetching scheme designed for emerging NVM storage. Unlike the baseline OS swapping mechanism, which is highly optimized for traditional spinning disks, SPAN leverages the inherent parallelism of NVM devices to proactivley fetch a set of pages from NVM storage to the small and fast main DRAM. In doing so, SPAN yields a speedup of ~18% versus swapping into the NVM with the baseline OS (~50% of the performance lost by the baseline OS versus placing the entire working set in DRAM memory). The proposed technique thus enables the utilization of such hybrid systems for memory-hungry applications, lowering the memory cost while keeping the performance comparable to the DRAM-only system.