Pointer life cycle types for lock-free data structures with memory reclamation

OpenMemDB is an in-memory database that is implemented solely using wait-free data structures. OpenMemDB is the ﬁrst and only database currently developed in such a way. OpenMemDB also provides linearizable correctness guarantees for all operations executed on the database. OpenMemDB uses a form of snapshot isolation to ensure linearizability, and avoids the write-skew problem that can occur when using snapshot isolation by eliminating writes that are out of data. OpenMemDBs biggest contribution is its completely wait-free implementation. Every operation executed in OpenMemDB is guaranteed to be wait-free and linearizable. This implementation also scales competitively when compared against similar in-memory database management systems. OpenMemDB achieves its best scaling in select heavy operation loads with nearly 12 times speedup at 16 threads. This is better scaling than either VoltDB or MemSQL showed in our testing.

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Decoupling lock-free data structures from memory reclamation for static analysis

Proceedings of the ACM on Programming Languages ◽

10.1145/3290371 ◽

2019 ◽

Vol 3 (POPL) ◽

pp. 1-31 ◽

Cited By ~ 1

Author(s):

Roland Meyer ◽

Sebastian Wolff

Keyword(s):

Static Analysis ◽

Data Structures ◽

Free Data

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Understanding the idiosyncrasies of real persistent memory

Proceedings of the VLDB Endowment ◽

10.14778/3436905.3436921 ◽

2020 ◽

Vol 14 (4) ◽

pp. 626-639

Author(s):

Shashank Gugnani ◽

Arjun Kashyap ◽

Xiaoyi Lu

Keyword(s):

Data Structures ◽

Evaluation Studies ◽

High Capacity ◽

Memory Module ◽

Study Guides ◽

Free Data ◽

Persistent Memory ◽

Benchmark Suite ◽

Near Future ◽

Internal Architecture

High capacity persistent memory (PMEM) is finally commercially available in the form of Intel's Optane DC Persistent Memory Module (DCPMM). Researchers have raced to evaluate and understand the performance of DCPMM itself as well as systems and applications designed to leverage PMEM resulting from over a decade of research. Early evaluations of DCPMM show that its behavior is more nuanced and idiosyncratic than previously thought. Several assumptions made about its performance that guided the design of PMEM-enabled systems have been shown to be incorrect. Unfortunately, several peculiar performance characteristics of DCPMM are related to the memory technology (3D-XPoint) used and its internal architecture. It is expected that other technologies (such as STT-RAM, memristor, ReRAM, NVDIMM), with highly variable characteristics, will be commercially shipped as PMEM in the near future. Current evaluation studies fail to understand and categorize the idiosyncratic behavior of PMEM; i.e., how do the peculiarities of DCPMM related to other classes of PMEM. Clearly, there is a need for a study which can guide the design of systems and is agnostic to PMEM technology and internal architecture. In this paper, we first list and categorize the idiosyncratic behavior of PMEM by performing targeted experiments with our proposed PMIdioBench benchmark suite on a real DCPMM platform. Next, we conduct detailed studies to guide the design of storage systems, considering generic PMEM characteristics. The first study guides data placement on NUMA systems with PMEM while the second study guides the design of lock-free data structures, for both eADR- and ADR-enabled PMEM systems. Our results are often counter-intuitive and highlight the challenges of system design with PMEM.

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