Informatica Industriale Prof. Davide Brugali
RT.10 – Gestione del sovraccarico
Informatica Industriale Prof. Davide Brugali
RT.10 – Gestione del sovraccarico
Types of overload
Transient overloads due to activation overruns. This type of overload is typical in event-driven systems and it is due to excessive arrivals of aperiodic jobs.
Transient overloads due to execution overrun. This type of overload can occur both in event-driven and clock-driven systems, and it is due to periodic or aperiodic tasks that sporadically execute more than expected.
Permanent overloads in periodic task systems. This type of overload occurs when the total utilization factor of the periodic task set is greater than one.
Causes of overloads
Bad system design (based on average behavior)
Malfunctioning of input devices
Variations in the environment
Simultaneous arrivals of events
Exceptions raised by the kernel
Load definitions
C = mean service time
λ = average interrarival time
ρ = load Ci =Computation time
Ti =Task period
U = Utilization factor The number of
Intervals can be
very large.
Istantaneous load ρ(t)
Relative deadline If Ci = Di the job does not have slack time load = 1
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