70 lines
2.2 KiB
Markdown
70 lines
2.2 KiB
Markdown
# Lecture Topic: Real Time CPU scheduling
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**Material up to 5.27 on the slides will be on the midterm**
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Multilevel Feedback Queue:
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A process can move between multiple queues
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Get from slides (?)
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Real Time CPU scheduling
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Can present challenges
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Soft real time systems: Critical real time tasks have the highest priortiy but there are no guarantees
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Hard real time systems: Tasks need to be scheduled first (?)
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Event Latency: The amount of time that elapses from when an event occurs to when it is serviced
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Two types of latency's affect performance:
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- Interrupt latency
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- Dispatch Latency
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Dispatch latency conflicts:
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- You need to preempt any processes running in kernel mode
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- Release by low priority processes of resource needed by high priority processes
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Priority based scheduling:
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For real time scheduling, you need to support preemptive, priority based scheduling, but this only guarantees soft real time
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For hard real time, must also provide ability to meet deadlines:
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Processes have new characteristics, periodic ones require CPU at constant intervals:
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- has processing time t, deadline of d, and a period p
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- 0 < t < d < p
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- rate of period task is 1/p
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Rate monotonic Scheduling:
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A priority is assigned based on the inverse of its period.
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Shorter periods = higher priority
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longer periods = lower priority
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Earliest deadline first:
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Priorities are assigned according to deadlines:
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The earlier the deadline, the higher the priority
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The later the deadline, the lower the priority
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Algorithm Evaluation:
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(?)
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# **Midterm Review:**
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Midterm is balanced:
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Applying tools relevant to concepts
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Answering theory questions
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About 60% of the grade is theory (no coding)
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50 minutes
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Understanding the labs and stuff under misc. in d2l should be enough
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Topics to review:
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Slides (Chapter 1 to Chapter 5, until rate monotonic scheduling)
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Lab 2 and Lab 3
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A1 and A2
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Content of the misc. useful stuff folder
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Scheduling, metrics
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Materials occurring multiple times in the lectures
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How to answer if you don't know
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If you remember the book answer - use that
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answer in your own words if you are trying to explain a concept
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the book is the most reliable source
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What would the output of the following function will probably be on the midterm |