Hybrid Overloading and Fault Tolerant Task Scheduling in Multiprocessor systems Based on Primary and Backup Scheme

With multiprocessor systems, redundant scheduling is a technique that trades processing power for increased reliability through redundancy. One approach, called primary-backup task scheduling, is often used in real-time multiprocessor systems to guarantee the deadlines of tasks in site of faults. Briefly, it consists in scheduling a secondary task conditionally in such a way that the secondary task is actually executed only if the primary task (or the processor executing it) fails to terminate properly. Doing so avoids wasting CPU resources in the failure-free case, but the difficulty comes from the fact that primary and secondary tasks must compete for resources in case of failure. To address this point, overloading strategies, such as primary and backup overloading (PB) and backup-backup overloading (BB), were developed to improve schedulability while retaining a certain degree of reliability. The aim of our research is to develop a good tradeoff between PB overloading and BB overloading. Then, we will use the new overloading technique to develop a new fault tolerance task scheduling approach.