Scheduling Configuration on Posix 1003.1b Systems
Abstract
Posix 1003.1b compliant systems provide two well-specified scheduling policies, namely {\it sched\_rr} (Round-Robin like) and {\it sched\_fifo} (FPP like). Up to now, little has been done to take advantage of the combination of both policies to maximize schedulability. In this study, we propose two priority, policy and quantum assignment algorithms for Posix 1003.1b systems that are optimal with regards to the power of the feasibility test (i.e. its ability to distinguish feasible and non feasible configurations). Though much less complex than an exhaustive exploration, the exponential complexity of the algorithms limits their applicability to small or medium-size problems. This is why a heuristic is proposed to handle larger task sets. As shown in the experiments, our proposal allows achieving a significant gain in feasibility over FPP, and therefore using the computational resources at their fullest potential. In many cases where FPP does not lead to a feasible schedule, using both FPP and RR may provide an alternative to EDF, which, most often, is not implemented at the OS kernel level.}
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