Committing conflicting transactions in an STM

Ramadan, Hany E.; Roy, Indrajit; Herlihy, Maurice; Witchel, Emmett

doi:10.1145/1504176.1504201

Cited by 43 publications

(33 citation statements)

References 18 publications

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“…Transaction ordering is a limited form of dependenceawareness [27,29], where conflicting accesses in overflowed and hardware transactions are ordered using the commit protocol, and data is forwarded only from overflowed to hardware transactions.…”

Section: Discussion Of Transaction Ordering and Overflowmentioning

confidence: 99%

“…However, zombies are easily contained by a combination of simple hardware and operating system modifications [27,29]. The commit protocol ensures that the hardware transaction serializes after the overflowed transaction and therefore will restart when the overflowed thread writes the data to reestablish the data's invariant.…”

Section: Safety Of Transaction Orderingmentioning

confidence: 99%

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Maximum benefit from a minimal HTM

2009

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A minimal, bounded hardware transactional memory implementation significantly improves synchronization performance when used in an operating system kernel. We add HTM to Linux 2.4, a kernel with a simple, coarse-grained synchronization structure. The transactional Linux 2.4 kernel can improve performance of user programs by as much as 40% over the non-transactional 2.4 kernel. It closes 68% of the performance gap with the Linux 2.6 kernel, which has had significant engineering effort applied to improve scalability.We then extend our minimal HTM to a fast, unbounded transactional memory with a novel technique for coordinating hardware transactions and software synchronization. Overflowed transactions run in software, with only a minimal coupling between hardware and software systems. There is no performance penalty for overflow rates of less than 1%. In one instance, at 16 processors and an overflow rate of 4%, performance degrades from an ideal 4.3× to 3.6×.

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Section: Discussion Of Transaction Ordering and Overflowmentioning

confidence: 99%

Section: Safety Of Transaction Orderingmentioning

confidence: 99%

Maximum benefit from a minimal HTM

2009

Self Cite

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“…Ramadan et al [34] perform value forwarding while tracking individual dependences between transactions, allowing to only abort dependent transactions. Since the system proposed, called DASTM, is based in the use of effective addresses, it works at a finer level of granularity than SP, and therefore there is almost no possibility of discarding potentially valid work due to false-sharing issues.…”

Section: Related Workmentioning

confidence: 99%

Squashing Alternatives for Software-Based Speculative Parallelization

Yaguez

Llanos

González-Escribano

2014

IEEE Trans. Comput.

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Speculative parallelization is a runtime technique that optimistically executes sequential code in parallel, checking that no dependence violations arise. In the case of a dependence violation, all mechanisms proposed so far either switch to sequential execution, or conservatively stop and restart the offending thread and all its successors, potentially discarding work that does not depend on this particular violation. In this work we systematically explore the design space of solutions for this problem, proposing a new mechanism that reduces the number of threads that should be restarted when a data dependence violation is found. Our new solution, called exclusive squashing, keeps track of inter-thread dependencies at runtime, selectively stopping and restarting offending threads, together with all threads that have consumed data from them. We have compared this new approach with existent solutions on a real system, executing different applications with loops that are not analyzable at compile time and present as much as 10% of inter-thread dependence violations at runtime. Our experimental results show a relative performance improvement of up to 14%, together with a reduction of one-third of the numbers of squashed threads. The speculative parallelization scheme and benchmarks described in this paper are available under request.

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“…Here is an illustration of this situation: whereas the other two transitions are dependent due to l2 (flow dependence). Measuring cyclic dependencies-beyond contention-is useful for synchronization, because some protocols work well under high contention, but cope poorly with cyclic dependencies [20,21].…”

Section: Quantifying Dependenciesmentioning

confidence: 99%

“…• Dependence-aware transactional memory (DATM-FG) [20,21] is effective for high-contention profiles with scarce cyclic dependencies between transactions. DATM-FG lets a transaction depend on another transaction "owning" a needed memory location, instead of aborting and retrying, effectively stalling the dependent transaction as long as no cyclic dependencies arise.…”

Section: Switching Between Stm Protocolsmentioning

confidence: 99%

Tightfit: adaptive parallelization with foresight

Tripp

Rinetzky

2013

Proceedings of the 2013 9th Joint Meeting on Foundations of Software Engineering

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Irregular applications often exhibit data-dependent parallelism: Different inputs, and sometimes also different execution phases, enable different levels of parallelism. These changes in available parallelism have motivated work on adaptive concurrency control mechanisms. Existing adaptation techniques mostly learn about available parallelism indirectly, through runtime monitors that detect pathologies (e.g. excessive retries in speculation or high lock contention in mutual exclusion).We present a novel approach to adaptive parallelization, whereby the effective level of parallelism is predicted directly based on input features, rather than through circumstantial indicators over the execution environment (such as retry rate). This enables adaptation with foresight, based on the input data and not the run prefix. For this, the user specifies input features, which our system then correlates with the amount of available parallelism through offline learning. The resulting prediction rule serves in deployment runs to foresee the available parallelism for a given workload and tune the parallelization system accordingly.We have implemented our approach in Tightfit, a general framework for input-centric offline adaptation. Our experimental evaluation of Tightfit over two adaptive runtime systems and eight benchmarks provides positive evidence regarding Tightfit's efficacy and accuracy.

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Committing conflicting transactions in an STM

Cited by 43 publications

References 18 publications

Maximum benefit from a minimal HTM

Maximum benefit from a minimal HTM

Squashing Alternatives for Software-Based Speculative Parallelization

Tightfit: adaptive parallelization with foresight

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