Title:
PORTS: Experiences with a Scheduler for Dynamic Real-Time Systems
PORTS: Experiences with a Scheduler for Dynamic Real-Time Systems
Author(s)
Ghosh, Kaushik
Fujimoto, Richard M.
Schwan, Karsten
Fujimoto, Richard M.
Schwan, Karsten
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Abstract
This paper describes several of our experiences with a real-time
scheduler. Using a robot control application program, we motivate the
importance of supporting multiple schedulers within the same
application program. We demonstrate the utility of speculative task
execution in dynamic real-time systems, and describe the implementation
of a scheduler for performing speculative execution and recovery. We
show that existing real-time scheduler interfaces have scope for
improvement, especially when scheduling latency must be low and when
multiple schedulers used by a single application must co-exist on a
single processor. A new scheduler interface is specified and its basic
costs are evaluated experimentally. Preliminary measurements on a KSR-1
machine are quoted. The measurements demonstrate how the execution
times of temporal queries may be reduced by use of access structures to
scheduler data structures. Finally, there are several overheads
associated with speculative execution, and multiple schedulers in a
single application. We consider the problem of on-line reconfiguration
of the several overheads associated with the speculative-execution
paradigm for optimal performance in the face of these overheads.
Initial performance measurements of the PORTS scheduler indicate that
it is possible to perform real-time scheduling with latencies
approximating those of proposed specialized scheduling co-processors.
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Date Issued
1994
Extent
205298 bytes
Resource Type
Text
Resource Subtype
Technical Report