2026-07-28T05:32:21Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:13082 2024-03-06T10:51:31Z ddc:004 open_access

Efficient Multi-Word Compare and Swap Guerraoui, Rachid Kogan, Alex Marathe, Virendra J. Zablotchi, Igor lock-free multi-word compare-and-swap persistent memory Atomic lock-free multi-word compare-and-swap (MCAS) is a powerful tool for designing concurrent algorithms. Yet, its widespread usage has been limited because lock-free implementations of MCAS make heavy use of expensive compare-and-swap (CAS) instructions. Existing MCAS implementations indeed use at least 2k+1 CASes per k-CAS. This leads to the natural desire to minimize the number of CASes required to implement MCAS. We first prove in this paper that it is impossible to "pack" the information required to perform a k-word CAS (k-CAS) in less than k locations to be CASed. Then we present the first algorithm that requires k+1 CASes per call to k-CAS in the common uncontended case. We implement our algorithm and show that it outperforms a state-of-the-art baseline in a variety of benchmarks in most considered workloads. We also present a durably linearizable (persistent memory friendly) version of our MCAS algorithm using only 2 persistence fences per call, while still only requiring k+1 CASes per k-CAS. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Rachid Guerraoui and Alex Kogan and Virendra J. Marathe and Igor Zablotchi 2020 Is Part Of LIPIcs, Volume 179, 34th International Symposium on Distributed Computing (DISC 2020) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.DISC.2020.4 urn:nbn:de:0030-drops-130827 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DISC.2020.4 eng https://creativecommons.org/licenses/by/3.0/legalcode