Questions and Answers
What is the main topic of the lecture?
What are jobs in the context of supercomputers?
Programs submitted by users that can be serial or parallel.
In batch scheduling, cores are shared between different jobs.
False
What does FCFS stand for?
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How is average wait time calculated?
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The shorter the average ______ time, the better the performance.
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What metrics are used to evaluate the performance of batch schedulers?
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What does the term 'non-preemptive' mean in batch scheduling?
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Study Notes
Batch Scheduling
- Focuses on supercomputers rather than general-purpose operating systems.
- Supercomputers consist of hundreds to millions of CPU cores, interconnected via high-speed networks.
- Commonly used by numerous scientific users, including physicists and chemists.
Job Types in Supercomputers
- Users submit "jobs" which can be:
- Serial Jobs: Utilize one core.
- Parallel Jobs: Utilize multiple cores simultaneously for increased speed.
- Job size (N) is defined by the number of cores required and remains fixed during execution.
- Typical job runtimes range from a few seconds to several hours.
Job Scheduling Representation
- Visualized as rectangles in a core x time plane.
- Size of jobs can be categorized as "wide" or "narrow."
- Runtime categorized as "short" or "long."
First Come First Serve (FCFS) Scheduling
- Jobs are executed in the order they arrive, indicated by numbers.
Key Characteristics of Batch Scheduling
- Ensures all processes of a job run concurrently on dedicated cores.
- Prevents inter-job communication issues by allocating entire cores to each job.
- Scheduling is non-preemptive; jobs complete before cores are released to waiting jobs.
Metrics for Performance Evaluation
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Average Wait Time: Interval from job submission to job start.
- Shorter wait times indicate better performance.
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Average Response Time: Interval from job submission to job termination.
- A shorter response time is indicative of superior performance.
- Response time = Wait time + Runtime.
Comparison of Wait and Response Times
- Users prioritize response time as it impacts job completion.
- Batch schedulers significantly influence wait time but not response time, assuming job runtimes are consistent.
Analytical Connection Between Wait and Response Times
- Average response time differences are constant and equal to the average runtime of all jobs.
- The notation for individual jobs includes:
- Wi = Wait time of job i
- Ri = Runtime of job i
- Ti = Response time of job i (with Ti = Wi + Ri).
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Description
This quiz focuses on scheduling in operating systems, particularly batch non-preemptive schedulers. It encourages students to explore the context of general-purpose operating systems and how specific scheduling topics apply. Prepare to deepen your understanding of scheduling mechanisms in various OS environments.
