Improving phase change memory performance with data content aware access
Improving phase change memory performance with data content aware access
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DOI：
10.1145/3381898.3397210
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发表时间：
2020-05
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通讯作者：
Shihao Song;Anup Das;O. Mutlu;Nagarajan Kandasamy
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作者：
Shihao Song;Anup Das;O. Mutlu;Nagarajan Kandasamy
相变存储器 (PCM) 是一种可扩展的非易失性存储器技术，具有低访问延迟（如 DRAM）和高容量（如闪存）。与读取其内容相比，写入 PCM 会产生明显更高的延迟和能量损失。 PCM写入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一内容相比，覆盖未知的内存内容可能会导致明显更高的延迟和能量。这是因为仅在一个方向上对 PCM 单元进行编程（即使用 SET 或 RESET 操作，而不是同时使用两者）来覆盖全零或全一内容。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一的内存位置来减少 PCM 写入的延迟和能量。 DATACON 的操作分三个步骤。首先，它通过综合考虑要写入的数据中设置位的数量以及 PCM 中 SET 和 RESET 操作的能量延迟权衡，估计 PCM 写入访问会从覆盖已知内容（例如全零或全一）中受益多少。其次，它将写入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用已知的全零或全一内容重新初始化未使用的存储器位置。仅当绝对必要时，DATACON 才会覆盖未知内容。我们使用最先进的机器学习应用程序、SPEC CPU2017 和 NAS 并行基准测试的工作负载来评估 DATACON。结果表明，与最先进的性能导向技术相比，DATACON 将有效访问延迟提高了 31%，整体系统性能提高了 27%，内存系统总能耗降低了 43%。
Phase change memory (PCM) is a scalable non-volatile memory technology that has low access latency (like DRAM) and high capacity (like Flash). Writing to PCM incurs significantly higher latency and energy penalties compared to reading its content. A prominent characteristic of PCM’s write operation 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 work- loads 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 improves the effective access latency by 31%, overall system performance by 27%, and total memory system energy consumption by 43% compared to the best of performance-oriented state-of-the-art techniques.