The memory controller is in charge of managing DRAM maintenance operations (e.g., refresh, RowHammer protection, memory scrubbing) in current DRAM chips. Implementing new maintenance operations often necessitates modifications in the DRAM interface, memory controller, and potentially other system components. Such modifications are only possible with a new DRAM standard, which takes a long time to develop, leading to slow progress in DRAM systems. In this paper, our goal is to 1) ease, and thus accelerate, the process of enabling new DRAM maintenance operations and 2) enable more efficient in-DRAM maintenance operations. Our idea is to set the memory controller free from managing DRAM maintenance. To this end, we propose Self-Managing DRAM (SMD), a new low-cost DRAM architecture that enables implementing new in-DRAM maintenance mechanisms (or modifying old ones) with no further changes in the DRAM interface, memory controller, or other system components. We use SMD to implement new in-DRAM maintenance mechanisms for three use cases: 1) periodic refresh, 2) RowHammer protection, and 3) memory scrubbing. We show that SMD enables easy adoption of efficient maintenance mechanisms that significantly improve the system performance and energy efficiency while providing higher reliability compared to conventional DDR4 DRAM. A combination of SMD-based maintenance mechanisms that perform refresh, RowHammer protection, and memory scrubbing achieve 7.6% speedup and consume 5.2% less DRAM energy on average across 20 memory-intensive four-core workloads. We make SMD source code openly and freely available at [128].

翻译：在现行DRAM芯片中，内存控制器负责管理DRAM维护操作（例如刷新、RowHammer防护、内存擦洗）。实现新的维护操作通常需要修改DRAM接口、内存控制器以及其他系统组件。此类修改仅在新DRAM标准出台后方可实现，而标准制定周期漫长，导致DRAM系统发展缓慢。本文旨在：1）简化并加速新型DRAM维护操作的部署进程；2）实现更高效的片内维护操作。我们的核心理念是解除内存控制器对DRAM维护的管理职责。为此，我们提出自管理DRAM（SMD）架构——一种低成本的新型DRAM架构，可在无需修改DRAM接口、内存控制器或其他系统组件的前提下，实现新的片内维护机制（或修改现有机制）。我们利用SMD为三个应用场景实现了新型片内维护机制：1）周期性刷新，2）RowHammer防护，3）内存擦洗。实验表明，SMD可使高效维护机制得到便捷部署，在提供优于传统DDR4 DRAM可靠性的同时，显著提升系统性能与能效。针对20个内存密集型四核工作负载的测试显示，基于SMD的刷新、RowHammer防护与内存擦洗组合维护机制平均可实现7.6%的加速，并降低5.2%的DRAM能耗。我们已在[128]处开源免费提供SMD源代码。