Emerging byte-addressable, non-volatile memory (NVM) is fundamentally changing the design principle of transaction logging. It potentially invalidates the need for flush-beforecommit as log records are persistent immediately upon write. Distributed logging-a once prohibitive technique for single node systems in the DRAM era-becomes a promising solution to easing the logging bottleneck because of the nonvolatility and high performance of NVM.In this paper, we advocate NVM and distributed logging on multicore and multi-socket hardware. We identify the challenges brought by distributed logging and discuss solutions. To protect committed work in NVM-based systems, we propose passive group commit, a lightweight, practical approach that leverages existing hardware and group commit. We expect that durable processor cache is the ultimate solution to protecting committed work and building reliable, scalable NVM-based systems in general. We evaluate distributed logging with logging-intensive workloads and show that distributed logging can achieve as much as ∼3x speedup over centralized logging in a modern DBMS and that passive group commit only induces minuscule overhead.

Future servers will be equipped with thousands of CPU cores and deep memory hierarchies. Traditional concurrency control (CC) schemes-both optimistic and pessimistic-slow down orders of magnitude in such environments for highly contended workloads. Optimistic CC (OCC) scales the best for workloads with few conflicts, but suffers from clobbered reads for high conflict workloads. Although pessimistic locking can protect reads, it floods cachecoherence backbones in deep memory hierarchies and can also cause numerous deadlock aborts. This paper proposes a new CC scheme, mostly-optimistic concurrency control (MOCC), to address these problems. MOCC achieves orders of magnitude higher performance for dynamic workloads on modern servers. The key objective of MOCC is to avoid clobbered reads for high conflict workloads, without any centralized mechanisms or heavyweight interthread communication. To satisfy such needs, we devise a native, cancellable reader-writer spinlock and a serializable protocol that can acquire, release and re-acquire locks in any order without expensive interthread communication. For low conflict workloads, MOCC maintains OCC's high performance without taking read locks. Our experiments with high conflict YCSB workloads on a 288core server reveal that MOCC performs 8× and 23× faster than OCC and pessimistic locking, respectively. It achieves 17 million TPS for TPC-C and more than 110 million TPS for YCSB without conflicts, 170× faster than pessimistic methods.

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Persistent memory (PM) is fundamentally changing the way database index structures are built by enabling persistence, high performance, and (near) instant recovery all on the memory bus. Prior work has proposed many techniques to tailor index structure designs for PM, but they were mostly based on volatile DRAM with simulation due to the lack of real PM hardware. Until today is it unclear how these techniques will actually perform on real PM hardware. With the recent released Intel Optane DC Persistent Memory, for the first time, this paper provides a comprehensive evaluation of recent persistent index structures. We focus on B + -Tree-based range indexes and carefully choose four representative index structures for evaluation: wBTree, NV-Tree, BzTree and FPTree. These four tree structures cover a wide, representative range of techniques that are essential building blocks of PM-based index structures. For fair comparison, we used an unified programming model for all trees and developed PiBench , a benchmarking framework which targets PM-based indexes. Through empirical evaluation using representative workloads, we identify key, effective techniques, insights and caveats to guide the making of future PM-based index structures.

A zeolitic imidazolate framework-8-based indocyanine green theranostic agent was constructed for fluorescence imaging and photothermal therapy of tumors in vivo.