2024-01-22 10:12:47

UNB/Year 4/Semester 1/CS3418/10-16-2023.md

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