Talk by Prof. Gilles Muller

Abstract:

Transactional Memory (TM) is considered as one of the most promising paradigms for developing concurrent applications. TM has been shown to scale well on multiple cores when the data access pattern behaves “well,” i.e., when few conflicts are induced. In contrast, data patterns with frequent write sharing, with long transactions, or when many threads contend for a smaller number of cores, produce numerous aborts. These problems are traditionally addressed by application-level contention managers, but they suffer from a lack of precision and provide unpredictable benefits on many workloads.
 
In this talk, we propose a system approach where the scheduler tries to avoid aborts by preventing conflicting transactions from running simultaneously. We use a combination of several techniques to help reduce the odds of conflicts, by (1) avoiding preempting threads running a transaction until the transaction completes, (2) keeping track of conflicts and delaying the restart of a transaction until conflicting transactions have committed, and (3) keeping track of conflicts and only allowing a thread with conflicts to run at low priority.
 
Our approach has been implemented in Linux for Software Transactional Memory (STM) using a shared memory segment to allow fast communication between the STM library and the scheduler. It only requires small and contained modifications to the operating system. Experimental evaluation demonstrates that our approach significantly reduces the number of aborts while improving transaction throughput on various workloads.
 
Bio:

Gilles Muller received the Ph.D. degree in 1988 from the University of Rennes I, and the Habilitation a Diriger des Recherches degree in 1997 from the University of Rennes I.
 
After having been a researcher at INRIA for 13 years, he is currently a Full Professor at the Ecole des Mines de Nantes. His research interests include the development of new methodologies based on the use of domain-specific languages for the structuring of operating systems. Gilles Muller has been a member of the IEEE since 1995 and the vice chair of the ACM/SIGOPS from July 2003 to July 2007.