SCC.131 Digital Systems - Process Scheduling

Flashcards for reviewing process scheduling concepts in digital systems.

Memory Protection

A security mechanism that prevents processes from accessing unauthorized memory regions.

Memory Management Unit (MMU)

A hardware component responsible for memory protection and address translation.

Virtual Memory

A memory management technique implemented using both hardware (MMU) and software (OS).

Translation Lookaside Buffer (TLB)

A hardware, automatic page table within the MMU.

TLB-hit

Virtual address translation is already present in the TLB.

TLB-miss

Virtual address translation is not found in the TLB.

Page Swapping

A memory management technique where the OS moves entire blocks of memory (pages) between RAM and HD.

Process Scheduling

Deciding which process to run on the CPU and for how long, ensuring efficient and fair resource allocation.

Program

A set of instructions written to perform a task, stored in memory.

Process

The active execution of a program, using system resources like CPU and memory.

Created/New Process State

Process is being created.

Ready Process State

Process is waiting to be assigned to CPU.

Running Process State

Process is currently being executed by the CPU.

Blocked(Waiting) Process State

Process is waiting for an event (e.g., I/O completion).

Terminated Process State

Process has finished execution.

Swapped Out and Waiting Process State

Process is removed from RAM and placed on HD by the scheduler.

Swapped Out and Blocked Process State

Processes that are blocked may aalso be swapped out.

CPU Utilization

Keep CPU as busy as possible.

Throughput

Number of processes that complete their execution per time unit.

Turnaround Time

Amount of time to execute a particular process.

Waiting Time

Amount of time a process has been waiting in the ready queue.

Response Time

Time taken from request submission to first response.

Fairness

Ensure equal opportunity for all processes.

Context Switching

Saving the state of a running process and loading the state of the next process.

Deadlock

Occurs when a group of processes is permanently blocked, each waiting for a resource held by another process in the group.

Starvation

Low-priority processes never get CPU time.

Multi-tasking

Running multiple processes on the machine interleaved over time.

Pre-emptive Multi-tasking

The OS decides when to switch and it’s done without the process’s involvement.

Short-Term Scheduling (CPU Scheduling)

Decides which process gets the CPU next, runs frequently, uses scheduling algorithms.

First-Come, First-Served (FCFS)

Non-preemptive, runs in order of arrival.

Shortest Job Next (SJN or SJF)

Runs the shortest process first.

Round Robin (RR)

Each process gets a fixed time slice (time quantum).

Priority Scheduling

Higher priority processes execute first.

Multilevel Queue Scheduling

Divides processes into different priority queues.

Round Robin (RR) Scheduling

Each process gets a fixed time (time quantum) for execution. If a process doesn't complete within the time quantum, it is preempted and moved to the end of the queue.