Leveraging transparent data distribution in openMP via user-level dynamic page migration

Abstract

This paper describes transparent mechanisms for emulating some of the data distribution facilities offered by traditional data-parallel programming models, such as High Performance Fortran, in OpenMP. The vehicle for implementing these facilities in OpenMP without modifying the programming model or exporting data distribution details to the programmer is user-level dynamic page migration [9, 10]. We have implemented a runtime system called UPMlib, which allows the compiler to inject into the application a smart user-level page migration engine. The page migration engine improves transparently the locality of memory references at the page level on behalf of the application. This engine can accurately and timely establish effective initial page placement schemes for OpenMP programs. Furthermore, it incorporates mechanisms for tuning page placement across phase changes in the application communication pattern. The effectiveness of page migration in these cases depends heavily on the overhead of page movements, the duration of phases in the application code and architectural characteristics. In general, dynamic page migration between phases is effective if the duration of a phase is long enough to amortize the cost of page movements.