Online Transaction Processing (OLTP) deployments are migrating from on-premise to cloud settings in order to exploit the elasticity of cloud infrastructure which allows them to adapt to workload variations. However, cloud adaptation comes at the cost of redesigning the engine, which has led to the introduction of several, new, cloud-based transaction processing systems mainly focusing on: (i) the transaction coordination protocol, (ii) the data partitioning strategy, and, (iii) the resource isolation across multiple tenants. As a result, standalone OLTP engines cannot be easily deployed with an elastic setting in the cloud and they need to migrate to another, specialized deployment. In this paper, we focus on workload variations that can be addressed by modern multi-socket, multi-core servers and we present a system design for providing fine-grained elasticity to multi-tenant, scale-up OLTP deployments. We introduce novel components to the virtualization software stack that enable on-demand addition and removal of computing and memory resources. We provide a bi-directional, low-overhead communication stack between the virtual machine and the hypervisor, which allows the former to adapt to variations coming both from the workload and the resource availability. We show that our system achieves NUMA-aware, millisecond-level, stateful and fine-grained elasticity, while it is not intrusive to the design of state-of-the-art, in-memory OLTP engines. We evaluate our system through novel use cases demonstrating that scale-up elasticity increases resource utilization, while allowing tenants to pay for actual use of resources and not just their reservation.

GaussDB, and its open source version named openGauss, are Huawei's relational database management systems (RDBMS), featuring a primary disk-based storage engine. This paper presents a new storage engine for GaussDB that is optimized for main memory and many cores. We started from a research prototype which exploits the power of the hardware but is not useful for customers. This paper describes the details of turning this prototype to an industrial storage engine, including integration with GaussDB. Standard benchmarks show that the new engine provides more than 2.5x performance improvement to GaussDB for full TPC-C on Intel's x86 many-cores servers, as well as on Huawei TaiShan servers powered by ARM64-based Kunpeng CPUs.

Non-Volatile Memory offers the possibility of implementing high-performance, durable data structures. However, achieving performance comparable to well-designed data structures in non-persistent (transient) memory is difficult, primarily because of the cost of ensuring the order in which memory writes reach NVM.\@ Often, this requires flushing data to NVM and waiting a full memory round-trip time. In this paper, we introduce two new techniques: Fine-Grained Checkpointing, which ensures a consistent, quickly recoverable data structure in NVM after a system failure, and In-Cache-Line Logging, an undo-logging technique that enables recovery of earlier state without requiring cache-line flushes in the normal case. We implemented these techniques in the Masstree data structure, making it persistent and demonstrating the ease of applying them to a highly optimized system and their low (5.9-15.4%) runtime overhead cost.

Processors with hardware support for transactional memory (HTM) are rapidly becoming commonplace, and processor manufacturers are currently working on implementing support for upcoming non-volatile memory (NVM) technologies. The combination of HTM and NVM promises to be a natural choice for in-memory database synchronization. However, limitations on the size of hardware transactions and the lack of progress guarantees by modern HTM implementations prevent some applications from obtaining the full benefit of hardware transactional memory. In this paper, we propose a persistent hybrid TM algorithm called PHyTM for systems that support NVM and HTM. PHyTM allows hardware assisted ACID transactions to execute concurrently with pure software transactions, which allows applications to gain the benefit of persistent HTM while simultaneously accommodating unbounded transactions (with a high degree of concurrency). Experimental simulations demonstrate that PHyTM is fast and scalable for realistic workloads.

We introduce Leaplist, a concurrent data-structure that is tailored to provide linearizable range queries. A lookup in Leaplist takes O (log n) and is comparable to a balanced binary search tree or to a Skiplist. However, in Leaplist, each node holds up-to K immutable key-value pairs, so collecting a linearizable range is K times faster than the same operation performed non-linearizably on a Skiplist.