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1. Horus: Persistent Security for Extended Persistence-Domain Memory Systems

   https://doi.org/10.1109/MICRO56248.2022.00087  

   Han, Xijing; Tuck, James; Awad, Amro (October 2022, 2022 55th IEEE/ACM International Symposium on Microarchitecture (MICRO))

   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. 

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2. FusionFS: Fusing I/O Operations using CISCOps in Firmware File Systems

   Jian Zhang, Yujie Ren (April 2022, File and storage technologies)

   We present FusionFS, a direct-access firmware-level in-storage filesystem that exploits the near-storage computational capability for fast I/O and data processing, consequently reducing I/O bottlenecks. In FusionFS, we introduce a new abstraction, CISCOps, that combines multiple I/O and data processing operations into one fused operation and offloaded for near-storage processing. By offloading, CISCOps significantly reduces dominant I/O overheads such as system calls, data movement, communication, and other software overheads. Further, to enhance the use of CISCOps, we introduce MicroTx for fine-grained crash consistency and fast (automatic) recovery of I/O and data processing operations. We also explore scheduling techniques to ensure fair and efficient use of in-storage compute and memory resources across tenants. Evaluation of FusionFS against the state-of-the-art user-level, kernel-level, and firmware-level file systems using microbenchmarks, macrobenchmarks, and real-world applications shows up to 6.12X, 5.09X and 2.07X performance gains, and 2.65X faster recovery for applications. 

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3. Evaluating Asynchronous Parallel I/O on HPC Systems

   https://doi.org/10.1109/IPDPS54959.2023.00030  

   Ravi, John; Byna, Suren; Koziol, Quincey; Tang, Houjun; Becchi, Michela (May 2023, 10.1109/IPDPS54959.2023.00030)

   Parallel I/O is an effective method to optimize data movement between memory and storage for many scientific applications. Poor performance of traditional disk-based file systems has led to the design of I/O libraries which take advantage of faster memory layers, such as on-node memory, present in high-performance computing (HPC) systems. By allowing caching and prefetching of data for applications alternating computation and I/O phases, a faster memory layer also provides opportunities for hiding the latency of I/O phases by overlapping them with computation phases, a technique called asynchronous I/O. Since asynchronous parallel I/O in HPC systems is still in the initial stages of development, there hasn't been a systematic study of the factors affecting its performance.In this paper, we perform a systematic study of various factors affecting the performance and efficacy of asynchronous I/O, we develop a performance model to estimate the aggregate I/O bandwidth achievable by iterative applications using synchronous and asynchronous I/O based on past observations, and we evaluate the performance of the recently developed asynchronous I/O feature of a parallel I/O library (HDF5) using benchmarks and real-world science applications. Our study covers parallel file systems on two large-scale HPC systems: Summit and Cori, the former with a GPFS storage and the latter with a Lustre parallel file system. 

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4. Zhuque: Failure is Not an Option, it's an Exception

   Hodgkins, George; Xu, Yi; Swanson, Steve; Izraelevitz, Joseph (July 2023, Proceedings of the 2023 USENIX Annual Technical Conference)

   Lawall, Julia; Williams, Dan (Ed.)

   Persistent memory (PMEM) allows direct access to fast storage at byte granularity. Previously, processor caches backed by persistent memory were not persistent, complicating the design of persistent applications and reducing their performance. A new generation of systems with flush-on-fail semantics effectively offer persistent caches, offering the potential for much simpler, faster PMEM programming models. This work proposes Whole Process Persistence (WPP), a new programming model for systems with persistent caches. In the WPP model, all process state is made persistent. On restart after power failure, this state is reloaded and execution resumes in an application-defined interrupt handler. We also describe the Zhuque runtime, which transparently provides WPP by interposing on the C bindings for system calls in userspace. It requires little or no programmer effort to run applications on Zhuque. Our measurements show that Zhuque outperforms state of the art PMEM libraries, demonstrating mean speedups across all benchmarks of 5.24x over PMDK, 3.01x over Mnemosyne, 5.43x over Atlas, and 4.11x over Clobber-NVM. More important, unlike existing systems, Zhuque places no restrictions on how applications implement concurrency, allowing us to run a newer version of Memcached on Zhuque and gain more than 7.5x throughput over the fastest existing persistent implementations. 

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5. TENET: Memory Safe and Fault Tolerant Persistent Transactional Memory}

   Madhava Krishnan Ramanathan; Diyu Zhou; Wook-Hee Kim; Sudarsun Kannan; Sanidhya Kashyap; Changwoo Min (February 2023, 21st USENIX Conference on File and Storage Technologies)

   Ashvin Goel; Dalit Naor (Ed.)

   Byte-addressable non-volatile memory (NVM) allows programs to directly access storage using memory interface without going through the expensive conventional storage stack. However, direct access to NVM makes the NVM data vulnerable to software bugs and hardware errors. This issue is critical because, unlike DRAM, corrupted data can persist forever, even after the system restart. Albeit the plethora of research on NVM programs and systems, there is little focus on protecting NVM data from software bugs and hardware errors. In this paper, we propose TENET, a new NVM programming framework, which guarantees memory safety and fault tolerance to protect NVM data against software bugs and hardware errors. TENET provides the popular persistent transactional memory (PTM) programming model. TENET leverages the concurrency guarantees (i.e., ACID properties) of PTM to provide performant and cost-efficient memory safety and fault tolerance. Our evaluations show that TENET offers an enhanced protection scope at a modest performance overhead and storage cost as compared to other PTMs with partial or no memory safety and fault tolerance support. 

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