We propose signature-accelerated transactional memory (SigTM), a hybrid TM system that reduces the overhead of software transactions. SigTM uses hardware signatures to track the read-set and write-set for pending transactions and perform conflict detection between concurrent threads. All other transactional functionality, including data versioning, is implemented in software. Unlike previously proposed hybrid TM systems, SigTM requires no modifications to the hardware caches, which reduces hardware cost and simplifies support for nested transactions and multithreaded processor cores. SigTM is also the first hybrid TM system to provide strong isolation guarantees between transactional blocks and nontransactional accesses without additional read and write barriers in non-transactional code.Using a set of parallel programs that make frequent use of coarsegrain transactions, we show that SigTM accelerates software transactions by 30% to 280%. For certain workloads, SigTM can match the performance of a full-featured hardware TM system, while for workloads with large read-sets it can be up to two times slower. Overall, we show that SigTM combines the performance characteristics and strong isolation guarantees of hardware TM implementations with the low cost and flexibility of software TM systems.

Transactional Memory (TM) is emerging as a promising technology to simplify parallel programming. While several TM systems have been proposed in the research literature, we are still missing the tools and workloads necessary to analyze and compare the proposals. Most TM systems have been evaluated using microbenchmarks, which may not be representative of any real-world behavior, or individual applications, which do not stress a wide range of execution scenarios.We introduce the Stanford Transactional Application for Multi-Processing (STAMP), a comprehensive benchmark suite for evaluating TM systems. STAMP includes eight applications and thirty variants of input parameters and data sets in order to represent several application domains and cover a wide range of transactional execution cases (frequent or rare use of transactions, large or small transactions, high or low contention, etc.). Moreover, STAMP is portable across many types of TM systems, including hardware, software, and hybrid systems. In this paper, we provide descriptions and a detailed characterization of the applications in STAMP. We also use the suite to evaluate six different TM systems, identify their shortcomings, and motivate further research on their performance characteristics.

Sleep is essential for optimal health, well-being, and cognitive functioning, and yet nationwide, youth are not obtaining consistent, adequate, or high-quality sleep. In fact, more than two-thirds of US adolescents are sleeping less than 8 hours nightly on school nights. Racial and ethnic minority children and adolescents are at an increased risk of having shorter sleep duration and poorer sleep quality than their white peers. In this review, we critically examined and compared results from 23 studies that have investigated racial/ethnic sleep disparities in American school-aged children and adolescents ages 6-19 years. We found that White youth generally had more sufficient sleep than minority youth, Hispanics had more than Blacks, and there was inconclusive evidence for Asians and other minorities. Recommendations for researchers include the following: (1) explore underlying causes of the disparities of these subpopulations, with a particular interest in identifying modifiable causes; (2) examine factors that may be impacted by racial/ethnic sleep disparities; (3) use a multidimensional approach to measuring sleep disparities; and (4) examine how beliefs about sleep are patterned by race/ethnicity. Understanding sleep disparities can inform interventions, policies, and educational programs to minimize sleep disparities and their impact on health, psychological, and educational outcomes.

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We propose signature-accelerated transactional memory (SigTM), a hybrid TM system that reduces the overhead of software transactions. SigTM uses hardware signatures to track the read-set and write-set for pending transactions and perform conflict detection between concurrent threads. All other transactional functionality, including data versioning, is implemented in software. Unlike previously proposed hybrid TM systems, SigTM requires no modifications to the hardware caches, which reduces hardware cost and simplifies support for nested transactions and multithreaded processor cores. SigTM is also the first hybrid TM system to provide strong isolation guarantees between transactional blocks and nontransactional accesses without additional read and write barriers in non-transactional code.Using a set of parallel programs that make frequent use of coarsegrain transactions, we show that SigTM accelerates software transactions by 30% to 280%. For certain workloads, SigTM can match the performance of a full-featured hardware TM system, while for workloads with large read-sets it can be up to two times slower. Overall, we show that SigTM combines the performance characteristics and strong isolation guarantees of hardware TM implementations with the low cost and flexibility of software TM systems.