1. NET 424: REAL-TIME SYSTEMS (Practical Part)
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Tutorial 8: on lecture 6

2. Question 1
A system contains two periodic tasks. They are (10,3) & (15,4).
The task system also contains a sporadic server whose period is 8 and budget =2 The sporadic server is scheduled with the periodic tasks rate-monotonically.
1)Suppose that two aperiodic tasks A1 arrives at 2 and has execution time 2 and A2 arrives at 7 and has execution time 2. Find a feasible schedule.
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3. Answer
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4. Question 2 Assume the following periodic tasks: Task Period
Deferrable server (7,1).
Can we schedule the above tasks using RMS (rate monotonic scheduling)?
Task
Period
Execution time 1 4 2 3 8
0.5 5
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5. Answer
Using :
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6. Answer
Testing for T1: 𝟏 𝟒 + 𝟏 𝟕 𝟏 𝟒 =𝟎.𝟔𝟒𝟐 < U , So we can schedule T1
𝑼=𝒏 𝟐 𝟏 𝒏 − 𝟏 =𝟔 𝟐 𝟏 𝟔 −𝟏 = 𝟎.𝟕𝟑𝟔
///n the total number of tasks including the server
T2, T3 can also be scheduled because they have the same value for the period and the execution time .
Testing for T4: 𝟏 𝟒 + 𝟎.𝟓 𝟖 𝟏 𝟕 + 𝟏 𝟖 =0.58 < U so both T4 and T5 can be scheduled
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7. Question 3 Execution time Period Task
Assume the following periodic tasks:
And a deferrable server (40,10).
Can we schedule the above tasks using RMS (rate monotonic scheduling) or EDF (earliest deadline first)?
Execution time
Period
Task 10 50 1 20 60 2
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8. Answer
Using :
RMS EDF
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9. Answer
1) RMS
Testing for T1: 𝟏𝟎 𝟓𝟎 + 𝟏𝟎 𝟒𝟎 𝟏𝟎 𝟓𝟎 =𝟎.𝟔𝟓 < U , So we can schedule T1
𝑼=𝒏 𝟐 𝟏 𝒏 − 𝟏 =𝟑 𝟐 𝟏 𝟑 −𝟏 = 𝟎.𝟕𝟕
///n the total number of tasks including the server
Testing for T2: 𝟏𝟎 𝟓𝟎 + 𝟐𝟎 𝟔𝟎 𝟏𝟎 𝟒𝟎 + 𝟏𝟎 𝟔𝟎 =0.95 > U T2 can NOT be scheduled.
We can NOT schedule the tasks using RMS.
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10. Answer 2) EDF Calculate T1:
𝟏𝟎 𝟓𝟎 + 𝟐𝟎 𝟔𝟎 + 𝟏𝟎 𝟒𝟎 (𝟏+ 𝟒𝟎−𝟏𝟎 𝟓𝟎 )=0.93<1, So we can schedule T1
Calculate T2:
𝟐𝟎 𝟔𝟎 + 𝟏𝟎 𝟓𝟎 + 𝟏𝟎 𝟒𝟎 (𝟏+ 𝟒𝟎−𝟏𝟎 𝟔𝟎 )=0.905 <1, So we can schedule T2
The tasks can be scheduled using EDF.
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11. The End
Any Questions ?
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