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Safe OpenNested Transactions Through Ownership Kunal Agrawal ITing Angelina Lee Jim Sukha

Summary: Safe Open胤ested Transactions Through Ownership
Kunal Agrawal I茅ing Angelina Lee Jim Sukha
MIT Computer Science and Artificial Intelligence Laboratory
Cambridge, MA 02139, USA
Researchers in transactional memory (TM) have proposed open nesting as a methodology for increasing the
concurrency of a program. The idea is to ignore certain ``low衍evel'' memory operations of an open要ested
transaction when detecting conflicts for its parent transaction, and instead perform abstract concurrency
control for the ``high衍evel'' operation that nested transaction represents. To support this methodology, TM
systems use an open要ested commit mechanism that commits all changes performed by an open要ested
transaction directly to memory, thereby avoiding low衍evel conflicts. Unfortunately, because the TM runtime
is unaware of the different levels of memory, an unconstrained use of open要ested commits can lead to
anomalous program behavior.
In this paper, we describe a framework of ownership苔ware transactional memory which incorporates the
notion of modules into the TM system and requires that transactions and data be associated with specific
transactional modules or Xmodules. We propose a new ownership苔ware commit mechanism, a hybrid
between an open要ested and closed要ested commit which commits a piece of data differently depending
on whether the current Xmodule owns the data or not. Moreover, we give a set of precise constraints on
interactions and sharing of data among the Xmodules based on familiar notions of abstraction. We prove that
ownership苔ware TM has has clean memory衍evel semantics and can guarantee serializability by modules,


Source: Agrawal, Kunal - Department of Computer Science and Engineering, Washington University in St. Louis


Collections: Computer Technologies and Information Sciences