Hardware Reference
In-Depth Information
*
r
=
r
1
1
r
*
=
r
+
C
1
1
d
J
=
d
-
C 2
J
2
1
2
1
d
=
d
2
2
*
d
C
1
1
J
1
r *
r
d
=
1
1
1
C
2
J
2
*
d
r
r
*
d
=
2
2
2
2
Figure 3.16
The transformation algorithm preserves the timing and the precedence con-
straints.
r i
d j and, according to EDF,
the processor is assigned to the ready task having the earliest deadline.
r j . Moreover, they cannot preempt J i
because d i
Therefore,
both timing and precedence constraints specified for task set
J
are guaranteed by the
J .
schedulability of the modified set
3.6
SUMMARY
The scheduling algorithms described in this chapter for handling real-time tasks with
aperiodic arrivals can be compared in terms of assumptions on the task set and com-
putational complexity. Figure 3.17 summarizes the main characteristics of such al-
gorithms and can be used for selecting the most appropriate scheduling policy for a
particular problem.
 
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