This paper presents user-level dynamic page migration, a runtime technique which transparently enables parallel programs to tune their memory performance on distributed shared memory multiprocessors, with feedback obtained from dynamic monitoring of memory activity. Our technique exploits the iterative nature of parallel programs and information available to the program both at compile time and at runtime in order to improve the accuracy and the timeliness of page migrations, as well as amortize better the overhead, compared to page migration engines implemented in the operating system. We present an adaptive page migration algorithm based on a competitive and a predictive criterion. The competitive criterion is used to correct poor page placement decisions of the operating system, while the predictive criterion makes the algorithm responsive to scheduling events that necessitate immediate page migrations, such as preemptions and migrations of threads. We also present a new technique for preventing page pingpong and a mechanism for monitoring the performance of page migration algorithms at runtime and tuning their sensitive parameters accordingly. Our experimental evidence on a SGI Origin2000 shows that unmodified OpenMP codes linked with our runtime system for dynamic page migration are effectively immune to the page placement strategy of the operating system and the associated problems with data locality. Furthermore, our runtime system achieves solid performance improvements compared to the IRIX 6.5.5 page migration engine, for single parallel OpenMP codes and multiprogrammed workloads.

Much research on school bullying and victimization have outlined several individual, family, and school parameters that function as risk factors for developing further psychosocial and psychopathological problems. Bullying and victimization are interrelated with symptoms of psychological trauma, as well as emotional/ behavioural reactions, which can destabilize psychosocial and scholastic pathways for children and adolescents. The current study explored the various dimensions of psychological trauma (depressive symptoms, somatization, dissociation, avoidance behaviours) associated with school bullying/victimization in relation to parental bonding among 433 students (8–16 years old) from representative large cities in Greece. The following scales were employed: (a) Olweus Bully/Victim Questionnaire, (b) Child Report of Post-traumatic Symptoms (CROPS), and (c) Parental Bonding Inventory instrument (PBI). Pathways analysis extracted a series of models which showed that maternal and paternal overprotection (anxious-controlling/aggressive) had positive association with post-traumatic stress symptoms. Specifically, the quality of parental bonding was related with children's bullying/victimization experiences and post-traumatic symptomology. Conversely, results indicated that maternal and paternal care can reduce the manifestation of post-traumatic stress symptoms. Implications for interventions are discussed.

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This paper investigates the performance implications of data placement in OpenMP programs running on modern ccNUMA multiprocessors. Data locality and minimization of the rate of remote memory accesses are critical for sustaining high performance on these systems. We show that due to the low remote-to-local memory access latency ratio of state-of-the-art ccNUMA architectures, reasonably balanced page placement schemes, such as round-robin or random distribution of pages incur modest performance losses. We also show that performance leaks stemming from suboptimal page placement schemes can be remedied with a smart user-level page migration engine. The main body of the paper describes how the OpenMP runtime environment can use page migration for implementing implicit data distribution and redistribution schemes without programmer intervention. Our experimental results support the effectiveness of these mechanisms and provide a proof of concept that there is no need to introduce data distribution directives in OpenMP and warrant the portability of the programming model.