Userland CO-PAGER: boosting data-intensive applications with non-volatile memory, userspace paging

With the emergence of low-latency non-volatile memory (NVM) storage, the software overhead, incurred by the operating system, becomes more prominent. The Linux (monolithic) kernel, incorporates a complex I/O subsystem design, using redundant memory copies and expensive user/kernel context switches to perform I/O. Memory-mapped I/O, which internally uses demand paging, has recently become popular when paired with low-latency storage. It improves I/O performance by mapping the data DMA transfers directly to userspace memory and removing the additional data copy between user/kernel space. However, for data-intensive applications, when there is insufficient physical memory, frequent page faults can still trigger expensive mode switches and I/O operations. To tackle this problem, we propose CO-PAGER, which is a lightweight userspace memory service. CO-PAGER consists of a minimal kernel module and a userspace component. The userspace component handles (redirected) page faults, performs memory management and I/O operations and accesses NVM storage directly. The kernel module is used to update memory mapping between user and kernel space. In this way CO-PAGER can bypass the deep kernel I/O stacks and provide a flexible/customizable and efficient memory paging service in userspace. We provide a general programming interface to use the CO-PAGER service. In our experiments, we also demonstrate how the CO-PAGER approach can be applied to a MapReduce framework and improves performance for data-intensive applications

Source parameters of the great Sumatran megathrust earthquakes of 1797 and 1833 inferred from coral microatolls

Large uplifts and tilts occurred on the Sumatran outer arc islands between 0.5° and 3.3°S during great historical earthquakes in 1797 and 1833, as judged from relative sea level changes recorded by annually banded coral heads. Coral data for these two earthquakes are most complete along a 160-km length of the Mentawai islands between 3.2° and 2°S. Uplift there was as great as 0.8 m in 1797 and 2.8 m in 1833. Uplift in 1797 extended 370 km, between 3.2° and 0.5°S. The pattern and magnitude of uplift imply megathrust ruptures corresponding to moment magnitudes (M_w) in the range 8.5 to 8.7. The region of uplift in 1833 ranges from 2° to at least 3.2°S and, judging from historical reports of shaking and tsunamis, perhaps as far as 5°S. The patterns and magnitude of uplift and tilt in 1833 are similar to those experienced farther north, between 0.5° and 3°N, during the giant Nias-Simeulue megathrust earthquake of 2005; the outer arc islands rose as much as 3 m and tilted toward the mainland. Elastic dislocation forward modeling of the coral data yields megathrust ruptures with moment magnitudes ranging from 8.6 to 8.9. Sparse accounts at Padang, along the mainland west coast at latitude 1°S, imply tsunami runups of at least 5 m in 1797 and 3–4 m in 1833. Tsunamis simulated from the pattern of coral uplift are roughly consistent with these reports. The tsunami modeling further indicates that the Indian Ocean tsunamis of both 1797 and 1833, unlike that of 2004, were directed mainly south of the Indian subcontinent. Between about 0.7° and 2.1°S, the lack of vintage 1797 and 1833 coral heads in the intertidal zone demonstrates that interseismic submergence has now nearly equals coseismic emergence that accompanied those earthquakes. The interseismic strains accumulated along this reach of the megathrust have thus approached or exceeded the levels relieved in 1797 and 1833

Motivational Characteristics and Fulfillment of Psychological Needs Among Physically Active Undergraduate Students

Background: Physical activity (PA) guidelines describe positive correlations between PA and health outcomes. Self-determination theory (SDT) was used to identify motivational factors crucial to a physically active lifestyle.Purpose: Identify and analyze how motivational characteristics, fulfillment of psychological needs, and individual experiences/beliefs influence PA.Methods: Participants defined as moderately to vigorously physically active by the International Physical Activity Questionnaire were recruited using nominated sampling and public advertising. Motivational characteristics and psychological needs were assessed using SDT, Motives for Physical Activities Measure – Revised (MPAM-R), and The Basic Psychological Need Satisfaction and Frustration Scale – General (BPNSF). Semi-structured interviews were recorded and transcribed for investigators to independently code operationally defined thematic statements and then jointly discuss consensus for final codes.Results: Qualitative analysis showed participants expressed higher life satisfaction (41) than frustration (19). Frequency of statements that expressed motivation included: competence (60), relatedness (35), autonomy (34), interest/enjoyment (34), fitness (12), and appearance (8). The MPAM-R survey revealed interest/enjoyment = 6.2, competence = 6.0, fitness = 6.0, appearance = 5.1, social = 3.9. The BPNSF survey revealed satisfaction was significantly greater than frustration with a large effect size for each psychological need (Autonomy n = 20, p = .05, z = -3.89, r = .87; Competence n = 20, p = .05, z = -4.0, r = .89; Relatedness n = 20, p = .05, z = -3.90, r = .87).Conclusion: Physically active undergraduate students showed greater satisfaction than frustration. Students also shared common beliefs such as a desire for lifelong PA. Motivation stemmed highest from competence, followed by relatedness, interest, and autonomy

The geopolitical economy of Thailand’s marine plasticpollution crisis

Currently approximately 9 million tons of plastic enter the world’s oceans annually. This is a majortransboundary problem on a global scale that threatens marine wildlife, coastal ecologies, human health andlivelihoods. Our concern in this paper is with the environmental governance of marine plastic pollution thatemanates from Thailand, the sixth biggest contributor globally. By zooming in on land-based polluters inThailand, we highlight both the systemic nature of the marine plastic problem and the relative impunity withwhich drivers of transboundary environmental harm function at all levels of governance. Drawing from 19 inter-views conducted with actors from the public, private and non-profit sectors, we examine three stages of theproblem: production, consumption and waste management. We found that three major barriers preventThailand’s government, private sector and citizens from engaging in the sort collective action needed to reducemarine plastic pollution. They are: (i) insufficient incentives to enact political change; (ii) scalar disconnects inwaste management; and (iii) inadequate public and private sector ownership over plastic waste reduction. Asthe state alone cannot change corporate and consumer behaviour, we argue that multi-stakeholder efforts acrossorganisational scales of governance and administrative boundaries are needed to address the barrier

The breakthrough listen search for intelligent life: a wideband data recorder system for the Robert C. Byrd green bank telescope

The Breakthrough Listen Initiative is undertaking a comprehensive search for radio and optical signatures from extraterrestrial civilizations. An integral component of the project is the design and implementation of wide-bandwidth data recorder and signal processing systems. The capabilities of these systems, particularly at radio frequencies, directly determine survey speed; further, given a fixed observing time and spectral coverage, they determine sensitivity as well. Here, we detail the Breakthrough Listen wide-bandwidth data recording system deployed at the 100-m aperture Robert C. Byrd Green Bank Telescope. The system digitizes up to 6 GHz of bandwidth at 8 bits for both polarizations, storing the resultant 24 GB/s of data to disk. This system is among the highest data rate baseband recording systems in use in radio astronomy. A future system expansion will double recording capacity, to achieve a total Nyquist bandwidth of 12 GHz in two polarizations. In this paper, we present details of the system architecture, along with salient configuration and disk-write optimizations used to achieve high-throughput data capture on commodity compute servers and consumer-class hard disk drives

Host and Geographic Range of Snake Fungal Disease in Tennessee, USA

Since 2005, declines in snake populations have been associated with severe fungal skin infections that are referred to as snake fungal disease (SFD: Clark et al. 2011; Sutherland et al. 2014). These infections present with physical signs, such as ulcerations and malformations, as well as behavioral changes, such as an increase in molting frequency and basking behaviors (Lorch et al. 2015; Tetzlafff et al. 2017). Historical reports mentioning sores on the head and body are often associated with the fungus Ophidiomyces ophiodiicola, formerly named Chrysosporium ophiodiicola (Sigler et al. 2013; Allender et al. 2015a). Recently, fulfillment of Koch's postulates has been confirmed for O. ophiodiicola causing disease in two host species including Agkistrodon piscivorus and Pantherophis guttatus (Allender et al. 2015b; Lorch et al. 2015). Although the causative agent for this disease is documented in an experimental setting, the current host, and natural geographic range is largely unknown