Real-Time and Fault-Tolerant Scheduling
FT Scheduling in Distributed and Multiprocessor
systems
Use primary/backup (PB) scheduling for achieving fault tolerance. Use the
concept of overloading a backup (ie, more than one backup use
the same time slot) and de-allocation of unused backup slots. This is
for non-preemptive timeline scheduling.
Papers describing:
Simulation results show that our method achieves higher task
schedulability than using a spare processor as a backup to be invoked
in the event of a failure. Further, we show that the cost, in terms of
schedulability, of guaranteeing fault tolerance for dynamic systems
in a fault-free environment is extremely low.
FT Scheduling in Single Processor NON-Preemptive systems
Devised an optimal scheme to guarantee FT RT PB scheduling assuming
any queue-based scheduling technique in RTSS '95.
The optimal solution is based on dynamic
programming and the second is a greedy heuristic which
closely approximates the optimal.
FT Scheduling in Single Processor Preemptive systems
We have also described a recovery scheme for re-execution in the
event of faults and its accompanying FT-RMS bounds (similar to Liu and
Leyland's bounds, with a multiplying factor!). We also extend the
original RMS, EDF, and the exact characterization of RMS
to provide tolerance for single and multiple transient faults.
Finally, we analyze and compare those bounds with existing bounds for
non-fault-tolerant and other variations of RMS. The
FT-RMS
results appear in the Journal of Real-Time Systems.
Sunondo Ghosh's dissertation, which combines all
these aspects, is
here .
FT need not be at the level of particular tasks. To exploit
system-level fault-tolerant behavior of a real-time system, we have
developed a
scenario changing scheme to create feasible schedules either
online or offline. We allow the system to switch between schedules to
implement graceful degradation, fault masking, load shedding, and
other FT techniques for RTSs.
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if you have a problem, try to get it via anonymous ftp in
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last generated on Thu Sep 2 1997 by Daniel Mosse'