Hardware Reference
In-Depth Information
SOLUTIONS FOR CHAPTER 5
5.1
The maximum Sporadic Server size can be computed by Equation (5.24):
2
−
P
U
max
SS
=
P
where
n
(
U
i
+1)=
7
9
7
=
3
P
=
6
·
2
.
i
=1
Hence substituting the value of
P
into Equation (5.24) we have
=
1
U
max
SS
3
.
To enhance aperiodic responsiveness, the server must run at the highest priority,
and this can be achieved by setting its period to
T
s
=
T
1
=6. Then, assuming
U
s
=
U
max
, its capacity will be
C
s
=
U
s
T
s
=2.
SS
5.2
The maximum Deferrable Server size can be computed by Equation (5.15).
Hence:
2
−
P
U
max
DS
1
.
And substituting the value of
P
=3
/
2 into Equation (5.15) we have
=
2
P
−
=
1
U
max
DS
4
.
Hence, by setting
U
s
=
U
max
and
T
s
=
T
1
=6, the capacity will be
C
s
=
DS
U
s
T
s
=6
/
4=1
.
5.
5.3
Following the same steps reported in Exercise 5.1, we know that the maximum
utilization that can be assigned to a Polling Server to guarantee the periodic
task set is
=
2
−
P
=
1
U
max
PS
3
.
So, by setting
T
s
=6(intermediate priority) and
C
s
=2, we satisfy the con-
straints. The resulting schedule is illustrated in Figure 13.10.
P
Search WWH ::
Custom Search