Vincent Gramoli
The University of Sydney, Computer Science, Faculty Member
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We propose a new algorithm for the list-based set based on a value-aware try-lock that we show to achieve optimal concurrency: it only rejects concurrent schedules that violate correctness of the implemented set type. We show empirically... more
We propose a new algorithm for the list-based set based on a value-aware try-lock that we show to achieve optimal concurrency: it only rejects concurrent schedules that violate correctness of the implemented set type. We show empirically that reaching optimality does not induce a significant overhead. In fact, our implementation of the concurrency-optimal algorithm outperforms both the Lazy Linked List and the Harris-Michael state-of-the-art algorithms.
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... 00329946 %2 INFO:INFO_NI %T Méthode décentralisée de mesure de dynamisme d'un réseau logique %A Le Merrer, Erwan %A Kermarrec ... Pour tolérer le dynamisme, ces applications proposent un mécanisme dont la complexité dépend de... more
... 00329946 %2 INFO:INFO_NI %T Méthode décentralisée de mesure de dynamisme d'un réseau logique %A Le Merrer, Erwan %A Kermarrec ... Pour tolérer le dynamisme, ces applications proposent un mécanisme dont la complexité dépend de cette borne maximale et ne prend ...
Transactional memory,(TM) is expected to become,a widely used parallel programming,paradigm,for multi-core architectures. To reach this goal, we need tools that not only help to develop TM, but also test them,and evaluate them,on a wide... more
Transactional memory,(TM) is expected to become,a widely used parallel programming,paradigm,for multi-core architectures. To reach this goal, we need tools that not only help to develop TM, but also test them,and evaluate them,on a wide range of work- loads. In this paper, we introduce a novel tool, TMUNIT, that is both a unit testing and workload,generation tool. Its primary ob-
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In this paper, we present the most extensive comparison of synchronization techniques. We evaluate 5 different synchronization techniques through a series of 31 data structure algorithms from the recent literature on 3 multicore platforms... more
In this paper, we present the most extensive comparison of synchronization techniques. We evaluate 5 different synchronization techniques through a series of 31 data structure algorithms from the recent literature on 3 multicore platforms from Intel, Sun Microsystems and AMD. To this end, we developed in C/C++ and Java a new micro-benchmark suite, called Synchrobench, hence helping the community evaluate new data structures and synchronization techniques. The main conclusion of this evaluation is threefold: (i) although compare-and-swap helps achieving the best performance on multicores, doing so correctly is hard; (ii) optimistic locking offers varying performance results while transactional memory offers more consistent results; and (iii) copy-on-write and read-copy-update suffer more from contention than any other technique but could be combined with others to derive efficient algorithms.
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La plupart des systèmes distribués modernes sont à la fois à grande échelle et dynamiques. Cet article met en avant le passage des systèmes distribués classiques aux systèmes dynamiques à grande échelle. Bien que la ré- plication... more
La plupart des systèmes distribués modernes sont à la fois à grande échelle et dynamiques. Cet article met en avant le passage des systèmes distribués classiques aux systèmes dynamiques à grande échelle. Bien que la ré- plication d'un objet (i.e., d'une donnée) à plusieurs endroits du réseau tolère les défaillances, cette technique implique un coût considérable à chaque modification de la valeur de l'objet. Ce surcoût est nécessaire pour que la valeur de l'objet reste cohérente. Dans les systèmes à grande échelle qui évoluent dynamiquement, les participants ne peuvent obtenir des informations globales. Un des défis majeurs de ces systèmes est donc de trouver un bon compromis entre la complexité en temps des opérations de lecture et d'écriture, et la complexité en messages requis pour la maintenance de la cohérence atomique. Cet article étudie ce compromis en décrivant différentes mémoires atomiques et en prenant en compte les contraintes imposées par les sys...
Blockchain has found applications to track ownership of digital assets. Yet, several blockchains were shown vulnerable to network attacks. It is thus crucial for companies to adopt secure blockchains before moving them to production. In... more
Blockchain has found applications to track ownership of digital assets. Yet, several blockchains were shown vulnerable to network attacks. It is thus crucial for companies to adopt secure blockchains before moving them to production. In this paper, we present Red Belly Blockchain (RBBC), the first secure blockchain whose throughput scales to hundreds of geodistributed consensus participants. To this end, we drastically revisited Byzantine Fault Tolerant (BFT) blockchains through three contributions: (i) defining the Set Byzantine Consensus problem of agreeing on a superblock of all proposed blocks instead of a single block; (ii) adopting a fair leaderless design to offer censorship-resistance guaranteeing the commit of correctly requested transactions; (iii) introducing sharded verification to limit the number of signature verifications without hampering security. We evaluate RBBC on up to 1000 VMs of 3 different types, spread across 4 continents, and under attacks. Although its performance is affected by attacks, RBBC scales in that its throughput increases to hundreds of consensus nodes and achieves 30k TPS throughput and 3 second latency on 1000 VMs, hence improving by 3x both the latency and the throughput of its closest competitor.
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This paper presents Timed Quorum System (TQS), a new quorum system especially suited for large-scale and dynamic systems. TQS requires that two quorums intersect with high probability if they are used in the same small period of time. It... more
This paper presents Timed Quorum System (TQS), a new quorum system especially suited for large-scale and dynamic systems. TQS requires that two quorums intersect with high probability if they are used in the same small period of time. It proposed an algorithm that implements TQS and that verifies probabilistic atomicity: a consistency criterion that requires each operation to respect atomicity
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We present the design, correctness, and analysis of SONDe, a simple fully decentralized object deployment al- gorithm for highly requested systems. Given anobject (ser- vice or data), SONDe provides a node with a constant upper bound (h)... more
We present the design, correctness, and analysis of SONDe, a simple fully decentralized object deployment al- gorithm for highly requested systems. Given anobject (ser- vice or data), SONDe provides a node with a constant upper bound (h) on the number of logical hops to access an object holder (provider), thus making tunable and predictable the communication latency between a node
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We adress the problem of estimating in a fully distributed way the dynamism over a network, called the churn. This BA presents, as far as we know, the first distributed method for monitoring churn in arbitrary networks, subject to... more
We adress the problem of estimating in a fully distributed way the dynamism over a network, called the churn. This BA presents, as far as we know, the first distributed method for monitoring churn in arbitrary networks, subject to arbitrary node departure and arrival patterns.
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Energy consumption is the most important factor that determines sensor node lifetime. The optimization of wireless sensor network lifetime targets not only the reduction of energy consumption of a single sensor node but also the extension... more
Energy consumption is the most important factor that determines sensor node lifetime. The optimization of wireless sensor network lifetime targets not only the reduction of energy consumption of a single sensor node but also the extension of the entire network lifetime. We propose a simple and adaptive energy-conserving topology management scheme, called SAND (Self-Organizing Active Node Density). SAND is fully decentralized and relies on a distributed probing approach and on the redundancy resolution of sensors for energy optimizations, while preserving the data forwarding and sensing capabilities of the network. We present the SAND's algorithm, its analysis of convergence, and simulation results. Simulation results show that, though slightly increasing path lengths from sensor to sink nodes, the proposed scheme improves significantly the network lifetime for different neighborhood densities degrees, while preserving both sensing and routing fidelity.