Real-Time Operating Systems
Real-Time Operating Systems
Real-Time Operating Systems
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Deadline monotonic<br />
(DM) scheduling<br />
¿ Assumption up to now:<br />
relative deadline = period<br />
¿ DM scheduling weakens this assumption<br />
¿ Static algorithm<br />
¿ For DM each periodic tasks τ i is characterized by<br />
four parameters:<br />
¿ (phase φ i )<br />
¿ Relative deadline D i (equal for all instances)<br />
¿ Worst case computation time C i (equal for all instances)<br />
¿ Period T i<br />
82<br />
81<br />
DM scheduling<br />
¿ DM = generalization of RM<br />
¿ RMA optimal for D = T<br />
¿ DMA extends this optimality for D < T<br />
¿ Priority of a process inversely proportional to its<br />
deadline<br />
¿ Given tasks τ i and τ j , D i < D j Æ P i > P j<br />
t<br />
t i<br />
C i<br />
T i<br />
D i<br />
41
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