Democratizing Transactional Programming

Gramoli, Vincent; Guerraoui, Rachid

doi:10.1007/978-3-642-25821-3_1

Cited by 8 publications

(5 citation statements)

References 41 publications

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“…Nevertheless, the standard TM interface forces all transactions to adopt the same strongest semantics prone to false-conflicts. 29 In Section 4, we discuss how to extend the basic TM interface to cope with such false-conflicts.…”

Section: Limitationsmentioning

confidence: 99%

“…For example, by the time a traversal transaction reaches a leaf, the value it reads at the root likely no longer matters, thus a conflict with a concurrent root update could simply be ignored. Nevertheless, the standard TM interface forces all transactions to adopt the same strongest semantics prone to false‐conflicts . In Section 4, we discuss how to extend the basic TM interface to cope with such false‐conflicts.…”

Section: The Speculation‐friendly Search Treementioning

confidence: 99%

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A speculation‐friendly binary search tree

Crain

Gramoli

Raynal

2018

Concurrency and Computation

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Abstract:We introduce the first binary search tree algorithm designed for speculative executions. Prior to this work, tree structures were mainly designed for their pessimistic (non-speculative) accesses to have a bounded complexity. Researchers tried to evaluate transactional memory using such tree structures whose prominent example is the red-black tree library developed by Oracle Labs that is part of multiple benchmark distributions. Although well-engineered, such structures remain badly suited for speculative accesses, whose step complexity might raise dramatically with contention.We show that our speculation-friendly tree outperforms the existing transaction-based version of the AVL and the red-black trees. Its key novelty stems from the decoupling of update operations: they are split into one transaction that modifies the abstraction state and multiple ones that restructure its tree implementation in the background. In particular, the speculation-friendly tree is shown correct, reusable and it speeds up a transaction-based travel reservation application by up to 3.5×. Key-words: Transactional Memory, concurrent data structures, balanced binary treesUn arbre binaire de recherche dédié aux accès transactionnels Résumé : Les transactions, qui utilisent une technique de synchronisation optimiste, simplifient la programmation des architectures multi-coeurs. En effet, un programmeur a seulement besoin d'insérer des opérations dans des transactions afin d'obtenir un programme concurrent correct. Les programmeurs ont donc tout naturellement utilisé cette encapsulation sur plusieurs structures de données originellement dédiéesà la programmation pessimiste (non optimistes) pourévaluer les transactions. L'exemple le plus probantétant l'arbre transactionnel rouge-noir développé par Oracle Labs et présent dans plusieurs distributions.Malheureusement, ces structures de données ne sont pas adaptéesà des exécutions optimistes car elles reposent sur des invariants contraignants, comme la profondeur logarithmique d'un arbre, pour borner le coût des accès pessimistes. Une telle complexité ne s'applique pas aux accés optimistes et garantir de tels invariants n'est pas nécessaire et induit de la contention en augmentant la probabilité pour une transaction d'avorter et de recommencer.Dans ce papier, nous présentons un arbre binaire de recherche qui viole de façon transitoire ces invariants pour gagner en efficacité. Nous montrons que cet arbre est plus efficace que les arbres AVL et rouge-noir. Sa nouveauté majeure réside dans la séparation de ses opérations de modifications : elles sont coupées en une transaction qui modifie l'abstraction et plusieurs autres qui restructurent son implémentation. La bibliothèque qui en résulte limite la quantité d'avortements en augmentant légèrement le nombre d'accès, en particulier, elle améliore une application de réservation de voyage basée sur les transactions par un facteur multiplicatif de 3,5.

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Section: Limitationsmentioning

confidence: 99%

Section: The Speculation‐friendly Search Treementioning

confidence: 99%

A speculation‐friendly binary search tree

Crain

Gramoli

Raynal

2018

Concurrency and Computation

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“…Introduce weak semantics to transactional memory. One approach is the combination with RCU described in Section 17.2.3.3, while Gramoli and Guerraoui survey a number of other weak-transaction approaches [GG14], for example, restricted partitioning of large "elastic" transactions into smaller transactions, thus reducing conflict probabilities (albeit with tepid performance and scalability). Perhaps further experience will show that some uses of extra-transactional accesses can be replaced by weak transactions.…”

Section: Extra-transactional Accessesmentioning

confidence: 99%

Is Parallel Programming Hard, And, If So, What Can You Do About It? (Release v2021.12.22a)

McKenney¹

2017

Preprint

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This work represents the views of the editor and the authors and does not necessarily represent the view of their respective employers. Trademarks:• IBM, zSeries, and PowerPC are trademarks or registered trademarks of International Business Machines Corporation in the United States, other countries, or both.• Linux is a registered trademark of Linus Torvalds.• i386 is a trademark of Intel Corporation or its subsidiaries in the United States, other countries, or both.• Other company, product, and service names may be trademarks or service marks of such companies.The non-source-code text and images in this document are provided under the terms of the Creative Commons Attribution-Share Alike 3.0 United States license. 1 In brief, you may use the contents of this document for any purpose, personal, commercial, or otherwise, so long as attribution to the authors is maintained. Likewise, the document may be modified, and derivative works and translations made available, so long as such modifications and derivations are offered to the public on equal terms as the non-source-code text and images in the original document.Source code is covered by various versions of the GPL. 2 Some of this code is GPLv2-only, as it derives from the Linux kernel, while other code is GPLv2-or-later. See the comment headers of the individual source files within the CodeSamples directory in the git archive 3 for the exact licenses. If you are unsure of the license for a given code fragment, you should assume GPLv2-only.

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“…But TMs conventionally impose serializability [24] or even stronger properties [13] on operations encapsulated within transactions. This may prohibit certain concurrent scenarios allowed by a large class of dynamic data structures [9].…”

Section: Introductionmentioning

confidence: 99%

In the Search for Optimal Concurrency

Gramoli

Kuznetsov

Ravi

2016

Structural Information and Communication Complexity

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Implementing a concurrent data structure typically begins with defining its sequential specification. However, when used as is, a nontrivial sequential data structure, such as a linked list, a search tree, or a hash table, may expose incorrect behavior: lost updates, inconsistent responses, etc. To ensure correctness, portions of the sequential code operating on the shared data must be "protected" from data races using synchronization primitives and, thus, certain schedules of the steps of concurrent operations must be rejected. But can we ensure that we do not "overuse" synchronization, i.e., that we reject a concurrent schedule only if it violates correctness?In this paper, we treat this question formally by introducing the notion of a concurrency-optimal implementation. A program's concurrency is defined here as its ability to accept concurrent schedules, i.e., interleavings of steps of its sequential implementation. An implementation is concurrency-optimal if it accepts all interleavings that do not violate the program's correctness. We explore the concurrency properties of search data structures which can be represented in the form of directed acyclic graphs exporting insert, delete and search operations. We prove, for the first time, that pessimistic (e.g., based on conservative locking) and optimistic serializable (e.g., based on serializable transactional memory) implementations of search data-structures are incomparable in terms of concurrency. Specifically, there exist simple interleavings of sequential code that cannot be accepted by any pessimistic (and resp., serializable optimistic) implementation, but accepted by a serializable optimistic one (and resp., pessimistic). Thus, neither of these two implementation classes is concurrency-optimal.

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Democratizing Transactional Programming

Cited by 8 publications

References 41 publications

A speculation‐friendly binary search tree

A speculation‐friendly binary search tree

Is Parallel Programming Hard, And, If So, What Can You Do About It? (Release v2021.12.22a)

In the Search for Optimal Concurrency

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