UWSpace

UWSpace is the University of Waterloo’s institutional repository for the free, secure, and long-term home of research produced by faculty, students, and staff.

Depositing Theses/Dissertations or Research to UWSpace

Are you a Graduate Student depositing your thesis to UWSpace? See our Thesis Deposit Help and UWSpace Thesis FAQ pages to learn more.

Are you a Faculty or Staff member depositing research to UWSpace? See our Waterloo Research Deposit Help and Self-Archiving pages to learn more.

Photo by Waterloo staff

Comunidades no DSpace

Selecione uma comunidade para navegar por suas coleções

Submissões Recentes

  • Imagem de Miniatura
    Item type: Item ,
    The Fence Complexity of Persistent Sets
    (Springer Nature Switzerland, 2023-09-30) Coccimiglio, Gaetano; Brown, Trevor; Ravi, Srivatsan
    We study the psync complexity of concurrent sets in the non-volatile shared memory model. Flush instructions are used in non-volatile memory to force shared state to be written back to non-volatile memory and must typically be accompanied by the use of expensive fence instructions to enforce ordering among such flushes. Collectively we refer to a flush and a fence as a psync. The safety property of strict linearizability forces crashed operations to take effect before the crash or not take effect at all; the weaker property of durable linearizability enforces this requirement only for operations that have completed prior to the crash event. We consider lock-free implementations of list-based sets and prove two lower bounds. We prove that for any durable linearizable lock-free set there must exist an execution where some process must perform at least one redundant psync as part of an update operation. We introduce an extension to strict linearizability specialized for persistent sets that we call strict limited effect (SLE) linearizability. SLE linearizability explicitly ensures that operations do not take effect after a crash which better reflects the original intentions of strict linearizability. We show that it is impossible to implement SLE linearizable lock-free sets in which read-only (or search) operations do not flush or fence. We undertake an empirical study of persistent sets that examines various algorithmic design techniques and the impact of flush instructions in practice. We present concurrent set algorithms that provide matching upper bounds and rigorously evaluate them against existing persistent sets to expose the impact of algorithmic design and safety properties on psync complexity in practice as well as the cost of recovering the data structure following a system crash.
  • Imagem de Miniatura
    Item type: Item ,
    Non-blocking k-ary Search Trees
    (Springer Berlin Heidelberg, 2011) Brown, Trevor; Helga, Joanna
    This paper presents the first concurrent non-blocking k-ary search tree. Our data structure generalizes the recent non-blocking binary search tree of Ellen et al. [5] to trees in which each internal node has k children. Larger values of k decrease the depth of the tree, but lead to higher contention among processes performing updates to the tree. Our Java implementation uses single-word compare-and-set operations to coordinate updates to the tree. We present experimental results from a 16-core Sun machine with 128 hardware contexts, which show that our implementation achieves higher throughput than the non-blocking skip list of the Java class library and the leading lock-based concurrent search tree of Bronson et al. [3].
  • Imagem de Miniatura
    Item type: Item ,
    Range Queries in Non-blocking k-ary Search Trees
    (Springer Berlin Heidelberg, 2012) Brown, Trevor; Avni, Hillel
    We present a linearizable, non-blocking k-ary search tree (k-ST) that supports fast searches and range queries. Our algorithm uses single-word compare-and-swap (CAS) operations, and tolerates any number of crash failures. Performance experiments show that, for workloads containing small range queries, our k-ST significantly outperforms other algorithms which support these operations, and rivals the performance of a leading concurrent skip-list, which provides range queries that cannot always be linearized.
  • Imagem de Miniatura
    Item type: Item ,
    B-slack Trees: Space Efficient B-Trees
    (Springer International Publishing, 2014) Brown, Trevor
    B-slack trees, a subclass of B-trees that have substantially better worst-case space complexity, are introduced. They store n keys in height O(log_b n), where b is the maximum node degree. Updates can be performed in O(log_{b/2} n) amortized time. A relaxed balance version, which is well suited for concurrent implementation, is also presented.
  • Imagem de Miniatura
    Item type: Item ,
    Performance Anomalies in Concurrent Data Structure Microbenchmarks
    (Schloss Dagstuhl – Leibniz-Zentrum für Informatik, 2023-02-15) Kharal, Rosina F.; Brown, Trevor
    Recent decades have witnessed a surge in the development of concurrent data structures with an increasing interest in data structures implementing concurrent sets (CSets). Microbenchmarking tools are frequently utilized to evaluate and compare the performance differences across concurrent data structures. The underlying structure and design of the microbenchmarks themselves can play a hidden but influential role in performance results. However, the impact of microbenchmark design has not been well investigated. In this work, we illustrate instances where concurrent data structure performance results reported by a microbenchmark can vary 10-100x depending on the microbenchmark implementation details. We investigate factors leading to performance variance across three popular microbenchmarks and outline cases in which flawed microbenchmark design can lead to an inversion of performance results between two concurrent data structure implementations. We further derive a set of recommendations for best practices in the design and usage of concurrent data structure microbenchmarks and explore advanced features in the Setbench microbenchmark.