Podcast
Questions and Answers
Under what conditions does a non-preemptive scheduling algorithm relinquish the CPU?
Under what conditions does a non-preemptive scheduling algorithm relinquish the CPU?
- When the process terminates, or switches to a waiting state. (correct)
- When the OS decides to favor another process.
- When a higher priority process becomes ready.
- After a predetermined time quantum expires.
Which of the following scenarios will invoke preemptive scheduling?
Which of the following scenarios will invoke preemptive scheduling?
- A process switches from waiting to ready state after I/O completion. (correct)
- A process requests I/O and moves to a waiting state.
- A process terminates its execution.
- A new process arrives in the ready queue.
What is the primary goal of CPU scheduling in a multiprogrammed operating system?
What is the primary goal of CPU scheduling in a multiprogrammed operating system?
- To maximize CPU utilization and system throughput. (correct)
- To ensure every process gets an equal share of CPU time.
- To minimize the number of processes in memory.
- To prevent processes from accessing each other's memory.
A process is using the CPU. Which scenario would lead to a non-preemptive context switch?
A process is using the CPU. Which scenario would lead to a non-preemptive context switch?
Why might preemptive scheduling introduce a cost compared to non-preemptive scheduling?
Why might preemptive scheduling introduce a cost compared to non-preemptive scheduling?
Which of the following is the simplest CPU scheduling algorithm?
Which of the following is the simplest CPU scheduling algorithm?
Which scheduling algorithm gives each process a fixed time quantum to execute?
Which scheduling algorithm gives each process a fixed time quantum to execute?
A system uses Shortest Job First (SJF) scheduling. How does it determine which process to execute next?
A system uses Shortest Job First (SJF) scheduling. How does it determine which process to execute next?
Which CPU scheduling algorithm is most suitable for time-sharing systems due to its preemptive nature?
Which CPU scheduling algorithm is most suitable for time-sharing systems due to its preemptive nature?
A process has a long CPU burst. Which scheduling algorithm could potentially lead to other processes waiting for a significant amount of time?
A process has a long CPU burst. Which scheduling algorithm could potentially lead to other processes waiting for a significant amount of time?
Flashcards
CPU Scheduling Definition
CPU Scheduling Definition
Managing CPU usage among multiple processes to maximize computer productivity.
Non-Preemptive Scheduling
Non-Preemptive Scheduling
Process switches from running to waiting state (e.g., I/O request) or process terminates.
Preemptive Scheduling
Preemptive Scheduling
Process switches from running to ready (e.g., interrupt) or waiting to ready (I/O completion).
First Come First Serve (FCFS)
First Come First Serve (FCFS)
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Shortest Job First (SJF)
Shortest Job First (SJF)
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Round Robin
Round Robin
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CPU Burst Time
CPU Burst Time
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Process Preemption
Process Preemption
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Study Notes
- CPU scheduling underlies multiprogrammed OS, increasing computer productivity via process switching.
- OS keeps multiple processes in memory, switching the CPU to another process when one waits.
- When a process waits, another takes over CPU use; this pattern continues.
CPU Scheduling Circumstances
- When a process switches from running to waiting state (e.g., I/O request), this is non-preemptive.
- When a process switches from running to ready state (e.g., interrupt), it's preemptive.
- Switching from waiting to ready state (e.g., I/O completion) is preemptive.
- Process termination is non-preemptive.
- No scheduling choice exists in circumstances 1 and 4; a new process from the ready queue must execute.
- Circumstances 1 and 4 are non-preemptive, where the executing process voluntarily relinquishes the CPU.
- Under non-preemptive scheduling, a process retains the CPU until termination or switching to waiting.
- Circumstances 2 and 3 are preemptive.
- Preemptive scheduling occurs when the OS favors another process, incurring a cost, especially with shared data, which can cause inconsistency.
Scheduling Algorithms
- First Come First Serve (FCFS) is the simplest algorithm and is non-preemptive, allocating the CPU to whichever process requests it first.
- Shortest Job First (SJF) assigns the CPU to the process with the smallest next CPU burst time and can be either non-preemptive or preemptive.
- CPU burst time signifies the required execution time for a specific process.
- SJF operates by assessing the duration of the subsequent CPU burst.
- Round Robin, designed for time-sharing, adds preemption to FCFS to switch processes and allocates CPU to the first ready queue process for "q" time units
- "q" represents the quantum, typically ranging from 10 to 100 milliseconds, and is preemptive.
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