Hardware Reference
In-Depth Information
C
T i
i
Server
τ
1
5
1
C s
= 5
= 10
τ
4
15
2
T
s
τ
1
τ 2
2
2
aperiodic
requests
SS active
C s
+2
5
+2
3
1
0
2
4
6
8
10
12
14
16
18
20
22
Figure 5.17
Example of a medium-priority Sporadic Server.
by τ 1 at t =5, is resumed at t =6and is completed at t =7. At this time, the replen-
ishment amount to be done at RT 2 is set equal to the capacity consumed in [4 , 7]; that
is, RA 2 =2.
Note that during preemption intervals SS stays active. This allows performing a single
replenishment, even if SS provides a discontinuous service for aperiodic requests.
At time t =8, SS becomes active again and a new replenishment is set at RT 3 =
t + T s =18.At t =11, SS becomes idle and the replenishment amount to be done at
RT 3 is set to RA 3 =2.
Figure 5.18 illustrates another example of aperiodic service in which SS is the highest-
priority task. Here, the first aperiodic request arrives at time t =2and consumes the
whole server capacity. Hence, a replenishment amount RA 1 =2is set at RT 1 =10.
The second request arrives when C s =0. In this case, the replenishment time RT 2 is
set as soon as the capacity becomes greater than zero. Since this occurs at time t =10,
Search WWH ::




Custom Search