Predictable threads for dynamic, hard real-time environments

Next-generation, hard real-time systems will require new, flexible function ality and guaranteed, predictable performance. This paper describes the UMa ss Spring threads package, designed specifically for multiprocessing in dyn amic, hard real-time environments. This package is unique because of its su pport for new thread semantics for real-time processing. Predictable creati on and execution of threads is achieved because of an underlying predictabl e kernel, the UMass Spring kernel. Design decisions and lessons learned whi le implementing the threads package are presented. Measurements affirm the predictability of this implementation on a representative multiprocessor pl atform. The adoption of the threads package in the UMass Spring kernel resu lts in additional performance improvements, which include reduced context s witching overhead and reduced average-case memory access durations.