Search for: All records

Persistent memory presents a great opportunity for crash-consistent computing in large-scale computing systems. The ability to recover data upon power outage or crash events can significantly improve the availability of large-scale systems, while improving the performance of persistent data applications (e.g., database applications). However, persistent memory suffers from high write latency and requires specific programming model (e.g., Intel’s PMDK) to guarantee crash consistency, which results in long latency to persist data. To mitigate these problems, recent standards advocate for sufficient back-up power that can flush the whole cache hierarchy to the persistent memory upon detection of an outage, i.e., extending the persistence domain to include the cache hierarchy. In the secure NVM with extended persistent domain(EPD), in addition to flushing the cache hierarchy, extra actions need to be taken to protect the flushed cache data. These extra actions of secure operation could cause significant burden on energy costs and battery size. We demonstrate that naive implementations could lead to significantly expanding the required power holdup budget (e.g., 10.3x more operations than EPD system without secure memory support). The significant overhead is caused by memory accesses of secure metadata. In this paper, we present Horus, a novel EPD-aware secure memory implementation. Horus reduces the overhead during draining period of EPD system by reducing memory accesses of secure metadata. Experiment result shows that Horus reduces the draining time by 5x, compared with the naive baseline design. 

The performance of persistent applications is severely hurt by current secure processor architectures. Persistent applications use long-latency flush instructions and memory fences to make sure that writes to persistent data reach the persistency domain in a way that is crash consistent. Recently introduced features like Intel's Asynchronous DRAM Refresh (ADR) make the on-chip Write Pending Queue (WPQ) part of the persistency domain and help reduce the penalty of persisting data since data only needs to reach the on-chip WPQ to be considered persistent. However, when persistent applications run on secure processors, for the sake of securing memory many cycles are added to the critical path of their write operations before they ever reach the persistent WPQ, preventing them from fully exploiting the performance advantages of the persistent WPQ. Our goal in this work is to make it feasible for secure persistent applications to benefit more from the on-chip persistency domain. We propose Dolos, an architecture that prioritizes persisting data without sacrificing security in order to gain a significant performance boost for persistent applications. Dolos achieves this goal by an additional minor security unit, Mi-SU, that utilizes a much faster secure process that protects only the WPQ. Thus, the secure operation latency in the critical path of persist operations is reduced and hence persistent transactions can complete earlier. Dolos retains a conventional major security unit for protecting memory that occurs off the critical path after inserting secured data into the WPQ. To evaluate our design, we implemented our architecture in the GEM5 simulator and analyzed the performance of 6 benchmarks from the WHISPER suite. Dolos improves their performance by 1.66x on average.