A prominent characteristic of write operation in Phase-Change Memory (PCM) is that its latency and energy are sensitive to the data to be written as well as the content that is overwritten. We observe that overwriting unknown memory content can incur significantly higher latency and energy compared to overwriting known all-zeros or all-ones content. This is because all-zeros or all-ones content is overwritten by programming the PCM cells only in one direction, i.e., using either SET or RESET operations, not both. In this paper, we propose data content aware PCM writes (DATACON), a new mechanism that reduces the latency and energy of PCM writes by redirecting these requests to overwrite memory locations containing all-zeros or all-ones. DATACON operates in three steps. First, it estimates how much a PCM write access would benefit from overwriting known content (e.g., all-zeros, or all-ones) by comprehensively considering the number of set bits in the data to be written, and the energy-latency trade-offs for SET and RESET operations in PCM. Second, it translates the write address to a physical address within memory that contains the best type of content to overwrite, and records this translation in a table for future accesses. We exploit data access locality in workloads to minimize the address translation overhead. Third, it re-initializes unused memory locations with known all-zeros or all-ones content in a manner that does not interfere with regular read and write accesses. DATACON overwrites unknown content only when it is absolutely necessary to do so. We evaluate DATACON with workloads from state-of-the-art machine learning applications, SPEC CPU2017, and NAS Parallel Benchmarks. Results demonstrate that DATACON significantly improves system performance and memory system energy consumption compared to the best of performance-oriented state-of-the-art techniques.

中文翻译：

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通过数据内容感知访问提高相变内存性能

相变存储器 (PCM) 中写操作的一个突出特点是其延迟和能量对要写入的数据以及被覆盖的内容很敏感。我们观察到，与覆盖已知的全零或全 1 内容相比，覆盖未知内存内容会导致显着更高的延迟和能量。这是因为通过仅在一个方向上编程 PCM 单元，即使用 SET 或 RESET 操作，而不是同时使用两者，来覆盖全零或全 1 的内容。在本文中，我们提出了数据内容感知 PCM 写入 (DATACON)，这是一种新机制，通过将这些请求重定向到覆盖包含全零或全 1 的内存位置来减少 PCM 写入的延迟和能量。DATACON 分三步操作。第一的，它通过综合考虑要写入的数据中的设置位数量以及能量延迟权衡来估计 PCM 写访问将从覆盖已知内容（例如全零或全 1）中受益多少PCM 中的 SET 和 RESET 操作。其次，它将写地址转换为内存中包含要覆盖的最佳内容类型的物理地址，并将此转换记录在表中以供将来访问。我们利用工作负载中的数据访问局部性来最小化地址转换开销。第三，它以不干扰常规读写访问的方式使用已知的全零或全一内容重新初始化未使用的内存位置。DATACON 仅在绝对必要时覆盖未知内容。我们使用来自最先进机器学习应用程序、SPEC CPU2017 和 NAS Parallel Benchmarks 的工作负载来评估 DATACON。结果表明，与面向性能的最先进技术相比，DATACON 显着提高了系统性能和内存系统能耗。