transmittance存储系统的多版本冲突概念
Multiversion Conflict Notion for Transactional Memory Systems
摘要：
近年来，软件事务存储器系统（STM）作为解决存储器中并发问题的优雅替代方案已经引起了极大的兴趣。STM系统采取乐观的方法。允许多个事务并发执行。完成后，每个事务都将被验证，如果观察到任何不一致，则会中止。否则允许提交。在数据库中，基于冲突概念的一类历史被称为冲突可串行化（CSR），其成员可以有效地验证。因此，CSR是数据库中常用的正确性标准。类似地，使用冲突的概念，可以设计其成员资格可以在多项式时间内验证的正确性标准，冲突不透明性（co-opacity），其是的子类。使用该验证机制，可以设计一个有效的STM实现，该实现是允许的w.r.t共不透明度。通过为每个事务对象存储多个版本，多版本STM比单版本STM提供更多的并发性。但共同不透明的主要缺点是，它不承认使用多个版本的历史。这促使我们为多版本STM开发新的冲突概念。本文提出了一种新的冲突概念--多版本冲突。使用这种冲突的概念，我们确定了一个新的子类的不透明性（一个流行的正确性标准），mvc-不透明，承认多版本的历史，其成员资格可以在多项式时间验证。我们证明了共不透明度是这个类的一个真子集。与传统冲突不同，所提出的冲突概念mv-冲突也可以应用于非顺序历史。此外，我们认为，这种冲突的概念可以很容易地扩展到其他正确性标准。
英文摘要：
In recent years, Software Transactional Memory systems (STMs) have garnered significant interest as an elegant alternative for addressing concurrency issues in memory. STM systems take optimistic approach. Multiple transactions are allowed to execute concurrently. On completion, each transaction is validated and if any inconsistency is observed it is aborted. Otherwise it is allowed to commit. In databases a class of histories called as conflict-serializability (CSR) based on the notion of conflicts have been identified, whose membership can be efficiently verified. As a result, CSR is the commonly used correctness criterion in databases. Similarly, using the notion of conflicts, a correctness criterion, conflict-opacity (co-opacity) which is a sub-class of can be designed whose membership can be verified in polynomial time. Using the verification mechanism, an efficient STM implementation can be designed that is permissive w.r.t co-opacity. By storing multiple versions for each transaction object, multi-version STMs provide more concurrency than single-version STMs. But the main drawback of co-opacity is that it does not admit histories that are uses multiple versions. This has motivated us to develop a new conflict notions for multi-version STMs. In this paper, we present a new conflict notion multi-version conflict. Using this conflict notion, we identify a new subclass of opacity (a popular correctness-criterion), mvc-opacity that admits multi-versioned histories and whose membership can be verified in polynomial time. We show that co-opacity is a proper subset of this class. The proposed conflict notion mv-conflict can be applied on non-sequential histories as well unlike traditional conflicts. Further, we believe that this conflict notion can be easily extended to other correctness-criterion as well.
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