Hybrid memory systems composed of emerging non-volatile memory (NVM) and DRAM have drawn increasing attention in recent years. To fully exploit the advantages of both NVM and DRAM, a primary goal is to properly place application data on the hybrid memories. Previous studies have focused on page migration schemes to achieve higher performance and energy efficiency. However, those schemes all rely on online page access monitoring (costly), and data migration at the page granularity may cause additional overhead due to DRAM bandwidth contention and maintenance of cache/TLB consistency. In this article, we present Object-level memory Allocation and Migration (OAM) mechanisms for hybrid memory systems. OAM exploits a profiling tool to characterize objects’ memory access patterns at different execution phases of applications, and applies a performance/energy model to direct the initial static memory allocation and runtime dynamic object migration between NVM and DRAM. Based on our newly-developed programming interfaces for hybrid memory systems, application source codes can be automatically transformed via static code instrumentation. We evaluate OAM on an emulated hybrid memory system, and experimental results show that OAM can significantly reduce system energy-delay-product by 61 percent on average compared to a page-interleaving data placement scheme. It can also significantly reduce data migration overhead by 83 and 69 percent compared to the state-of-the-art page migration scheme CLOCK-DWF and 2PP, respectively, while improving application performance by up to 22 and 10 percent.

中文翻译：

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混合内存系统中的对象级内存分配和迁移

近年来，由新兴的非易失性存储器 (NVM) 和 DRAM 组成的混合存储器系统引起了越来越多的关注。为了充分利用 NVM 和 DRAM 的优势，主要目标是将应用程序数据正确放置在混合存储器上。以前的研究主要集中在页面迁移方案上，以实现更高的性能和能源效率。但是，这些方案都依赖于在线页面访问监控（成本高），并且由于DRAM带宽争用和缓存/TLB一致性的维护，页面粒度的数据迁移可能会导致额外开销。在本文中，我们介绍了混合内存系统的对象级内存分配和迁移 (OAM) 机制。OAM 利用分析工具来表征对象在应用程序不同执行阶段的内存访问模式，并应用性能/能量模型来指导 NVM 和 DRAM 之间的初始静态内存分配和运行时动态对象迁移。基于我们新开发的混合内存系统编程接口，应用源代码可以通过静态代码检测自动转换。我们在模拟混合内存系统上评估 OAM，实验结果表明，与页面交错数据放置方案相比，OAM 可以显着减少系统能量延迟积平均 61%。与最先进的页面迁移方案 CLOCK-DWF 和 2PP 相比，它还可以分别显着减少 83% 和 69% 的数据迁移开销，同时将应用程序性能提高多达 22% 和 10%。